&EPA
United States
Environmental
Protection
Agency
Environmental Monitoring
Systems Laboratory
P.O. Box 93478
Las Vegas, NV 89193-3478
EPA 600/8-87/024
June 1987
Research and Development
WET DEPOSITION AND
SNOWPACK MONITORING
OPERATIONS AND QUALITY
ASSURANCE MANUAL
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EPA 600/8-87/024
June 1987
WET DEPOSITION AND SNOWPACK MONITORING OPERATIONS
AND QUALITY ASSURANCE MANUAL
by
D. J. Chaloud, L. R. Todechiney, R. C. Metcalf, and B. C. Hess
Lockheed Engineering and Management Services Co., Inc.
Las Vegas, Nevada 89114
Contract No. 68-03-3249
Project Officer
Wesley L. Kinney
Exposure Assessment Research Division
Environmental Monitoring Systems Laboratory
Las Vegas, Nevada 89114
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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NOTICE
The information in this document has been funded wholly or in part by the
U.S. Environmental Protection Agency under contract number 68-03-3249 to
Lockheed Engineering and Management Services Company, Inc. It has been subject
to the Agency's peer and administrative review, and it has been approved for
publication as an Agency document.
The mention of trade names or commercial products in this manual is for
illustration purposes and does not constitute endorsement or recommendation for
use.
11
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ABSTRACT
This manual (user's guide) describes the quality assurance plan and
operations protocols for a comparative study of snow collection instruments
being conducted on Mt. Evans. Instruments to be compared include the Aerochem
Metrics Model 301 wet/dry deposition collector, the Belfort Model 780-5 weighing
rain gage, and 18 inch-diameter flanged bulk samplers. In addition, ground
measurements are made to provide a "ground truth" standard. Primary project
objectives include assessment of operational reliability, estimation of inter-
instrument and temporal variability, comparison of water equivalent and matrix
chemistry between the collection devices and ground measurements, and recommen-
dation of instruments and sampling intervals for future high altitude, complex
terrain monitoring. The protocols related to quality assurance, quality control,
calibration, operation, maintenance, processing, analysis, and data management
are described. As such, this manual is considered to be of greatest benefit to
field operators, laboratory analysts, and project managers.
This manual is submitted in partial fulfillment of Contract 68-03-3249 by
Lockheed-EMSCO under the sponsorship of the U.S. Enironmental Protection
Agency. This manual covers operations from February 1987 to June 1987, and
work will be completed as of December 1987.
111
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IV
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Section Contents
Revision 1
Date: 4/87
Page 1 of 3
CONTENTS
Page Revision
Abstract iii
Figures viii
Tables ix
Acknowledgment x
1.0 Introduction 1 of 2 1
2.0 Project Description 1 of 3 1
3.0 Quality Assurance Plan 1 of 15 1
3.1 Quality Assurance Objectives 1 of 15 1
3.1.1 Precision and Accuracy 1 of 15 1
3.1.2 Completeness . 5 of 15 1
3.1.3 Representativeness 5 of 15 1
3.1.4 Comparability 6 of 15 1
3.2 Field Operations QA 6 of 15 1
3.2.1 Siting Criteria and Facilities 6 of 15 1
3.2.2 Instrument Operation 7 of 15 1
3.2.3 Sample Handling 7 of 15 1
3.2.4 Documentation 8 of 15 1
3.3 Processing Laboratory QA 8 of 15 1
3.3.1 Water Equivalent 10 of 15 1
3.3.2 pH 10 of 15 1
3.3.3 Specific Conductance 10 of 15 1
3.3.4 Aliquot Preparation 10 of 15 1
3.3.5 Field Support 11 of 15 1
3.3.6 Documentation 11 of 15 1
3.4 Analytical Laboratory QA 11 of 15 1
3.5 Data Evaluation 11 of 15 1
3.5.1 Audit Sample Acceptance Criteria 12 of 15 1
3.5.2 Duplicate Sample Acceptance Criteria. ... 14 of 15 1
3.5.3 Blank Sample Acceptance Criteria 14 of 15 1
3.5.4 Holding Times 14 of 15 1
3.5.5 Data Flags 15 of 15 1
4.0 Field Operations 1 of 26 1
4.1 Equipment and Supplies 1 of 26 1
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CONTENTS (Continued)
Page Revision
4.1.1 Wet/Dry Collector 1 of 26 1
4.1.2 Bel fort Recording Rain Gage 5 of 26 1
4.1.3 Bulk Sampler 7 of 26 1
4.1.4 Science Associates Wind Speed and Wind
Direction Sensors 8 of 26 1
4.1.5 Data Acquisition System 10 of 26 1
4.2 Calibration, Maintenance, and Quality Control. . 11 of 26 1
4.2.1 Wet/Dry Collector 11 of 26 1
4.2.2 Bel fort Rain Gage 12 of 26 1
4.2.3 Bulk Samplers 15 of 26 1
4.2.4 Science Associates Meteorological Sensors 15 of 26 1
4.2.5 Data Acquisition System 17 of 26 1
4.3 Troubleshooting 18 of 26 1
4.4 Sample Collection, Handling, and Shipment. ... 18 of 26 1
4.5 Daily Operator Activities 20 of 26 1
4.6 Documentation 21 of 26 1
4.6.1 Site Operator's Logbook 21 of 26 1
4.6.2 Belfort Rain Gage Charts 21 of 26 1
4.6.3 Data Acquisition System 21 of 26 1
4.6.4 Photographs 22 of 26 1
4.6.5 Field Data Form 22 of 26 1
4.7 Snow Coring, Snow Pit Density Measurements,
and Snowboards 22 of 26 1
4.7.1 Snow Coring 22 of 26 1
4.7.2 Snow Pit Density 23 of 26 1
4.7.3 Snowboard Precipitation Amount Sampling . 24 of 26 1
5.0 Analytical Operations 1 of 35 1
5.1 Processing Activities 1 of 35 1
5.1.1 Sample Handling 1 of 35 1
5.1.2 Water Equivalent Determination 3 of 35 1
5.1.3 Specific conductance 4 of 35 1
5.1.4 pH 7 of 35 1
5.1.5 Aliquot Preparation 9 of 35 1
5.1.6 Field Support 12 of 35 1
vi
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CONTENTS (Continued)
Page Revision
5.2 Analytical Procedures 13 of 35 1
5.2.1 Determination of Ammonium 13 of 35 1
5.2.2 Determination of Chloride, Nitrate, and
Sulfate by Ion Chromatography 19 of 35 1
5.2.3 Determination of Metals (Ca, K, Mg, Na)
by Atomic Absorption Spectroscopy .... 24 of 35 1
6.0 Data Management 1 of 1 1
7.0 References 1 of 2 1
Appendices
A DAS Operation 1 of 7 1
B Processing Laboratory Conductivity Method 1 of 7 1
C Laboratory pH Determination 1 of 10 1
D Filtration, Preservation, and Shipping 1 of 7 1
E Determination of Ammonium by Flow Injection Analysis. . 1 of 4 1
F Determination of Dissolved Metals (Ca and Mg) by
Inductively Coupled Plasma Emission Spectroscopy. . . 1 of 9 1
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Page 1 of 1
FIGURES
Figure Page Revision
3-1 Snowpack field data form 9 of 15 1
4-1 Aerochem metrics wet/dry deposition collector .... 3 of 26 1
4-2 Bel fort weighing rain gage 6 of 26 1
5-1 Ammonia manifold AAI 17 of 35 1
5-2 Ammonia Manifold AAI I 18 of 35 1
5-3 Standard Addition Plot 30 of 35 1
A-l Windspeed indicator calibration 6 of 7 1
B-l Flowchart for conductivity 2 of 7 1.
C-l Flowchart for laboratory pH determination 2 of 10 1
C-2 Troubleshooting flowchart for pH determination. ... 3 of 10 1
D-l Filtration apparatus 3 of 7 1
vm
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Section Tables
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Page 1 of 1
TABLES
Number Page Revision
3-1
3-2
3-3
4-1
5-1
5-2
5-3
5-4
C-l
F-l
F-2
F-3
F-4
Quality Assurance Objectives for Detectability,
Precision, and Accuracy
Processing Laboratory Aliquot Description and
Analytical Laboratory Analysis Schedule
List of Maximum Recommended Holding Times
Field Equipment List
Suggested Concentration of Dilute Calibration
Standards
Typical 1C Operating Conditions
Atomic Absorption Concentration Ranges
pH Values of Buffers at Various Temperatures
Recommended Wavelengths and Estimated Instrumental
Detection Limits
Analyte Concentration Equivalents (mg/L) Arising From
Interferences at the 100-mg/L Level
Interference and Analyte Elemental Concentrations Used
for Interference Measurements in Table F-2
ICP Precision and Accuracy Data
2 of 15
12 of 15
15 of 15
2 of 26
22 of 35
23 of 35
24 of 35
25 of 35
6 of 10
2 of 9
4 of 9
5 of 9
8 of 9
1
1
1
1
1
1
1
1
1
1
1
1
1
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ACKNOWLEDGEMENT
Contributions provided by the following individuals were essential to the
completion of this manual and are gratefully acknowledged: Lori Arent, Larry
Fisher, Sevda Drouse, Marianne Faber, Jan Engels, Dave Peck, Dan Hillman,
Steve Pi a, Xavier Suarez, Marty Stapanian, Mohammad Mi ah, Dick Buell, Annalisa
Hall, and Steve Pierett (Lockheed Engineering and Management Services Company,
Inc.). Don Campbell (U.S. Geological Survey), Mark Peden (Illinois State Water
Survey), Mary Ann Allan (Electric Power Research Institute), and Sharon Brown
and her entire staff (Computer Sciences Corporation).
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1.0 INTRODUCTION
Established acidic deposition monitoring networks largely neglect the high
elevation areas of the western United States. Interest in these areas is
growing, particularly for the Rocky Mountain region, because of evidence
that precipitation amount, and possibly total chemical loading, is strongly
correlated with elevation (Svoboda and Olson, 1986). Most monitoring
equipment and siting criteria were developed for low elevation, flat-land
sites. Meteorology in mountainous terrain is significantly more complex,
and precipitation levels are higher than at low-elevation sites. Research
on the suitability of existing instruments for use at high altitude is
needed before large funding and personnel resources are committed to
monitoring acidic deposition in mountainous terrain.
The National Atmospheric Deposition Program (NADP), EPA Region VIII, and
U.S. Forest Service are participating in an investigation of equipment
performance at high altitude. The University of Denver High Altitude
Laboratory, EPA Environmental Monitoring Systems Laboratory in Las Vegas,
Nevada (EMSL-LV), and the prime contractor for EMSL-LV, Lockheed Engineering
and Management Services Company, Inc. (Lockheed-EMSCO), are responsible
for equipment installation, field station operation, and data interpreta-
tion. EMSL-LV and Lockheed-EMSCO have primary responsibility for construc-
tion of the monitoring platform, installation of equipment, operator
training, snow density/coring activities, data verification and interpreta-
tion, chemical analyses, and quality assurance. Instruments to be evaluated
include the Aerochem Metrics Model 301 wet/dry deposition collector, the
Belfort weighing rain gage, and bulk samplers. Snow density, snow coring,
and event sampling also are being undertaken to provide a "ground truth"
comparison. Samplers are to be evaluated in terms of reliability and ease
of operation, catch efficiency, and resultant sample matrix chemistry.
Meteorological sensors located on the monitoring platform will provide
information on the meteorological environment surrounding the collectors.
The selected site is the High Altitude Laboratory operated by the University
of Denver. The High Altitude Laboratory is located adjacent to the Mount
Evans highway near Echo Lake, 14 miles south of Idaho Springs, Colorado.
The site offers several advantages: the terrain is complex, and the area
is subject to large amounts of precipitation and to high winds; the site
is accessible even in winter, it has electrical power, and it is inhabited
year-round. A National Oceanic and Atmospheric Administration (NOAA) mon-
itoring station located near the monitoring platform can provide additional
meteorological information. Monitoring is to begin as soon as possible
after construction of the monitoring platform and is to continue through
the winter of 1986-87. Operation is scheduled to cease in mid-June 1987.
This manual details the equipment operation, chemical analyses, and
quality assurance plan for the wet deposition and snowpack monitoring
project. It is designed to be of primary benefit to the station operator,
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Page 2 of 2
laboratory analysts, and data analysts. The protocols presented here may
be revised over the course of the program to reflect necessary changes and
improvements in procedures. Related documents include an operations
status report which will be delivered in June 1987 and a final report on
the evaluation results which will be provided in January 1988.
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Section 2.0
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2.0 PROJECT DESCRIPTION
Snowpack and wet deposition monitoring on Mount Evans is being conducted
to assess the suitability of selected collection devices to high altitude,
complex terrain situations. Specific objectives of the project are as
fol1ows:
o Inter-instrument sampling variability for two colocated wet/dry
collectors will be estimated by comparing chemistry and water
equivalent for weekly samples.
o Inter-instrument sampling variability for two colocated Bel fort
weighing rain gages will be estimated by comparing water equiv-
alent for event and weekly data.
o Temporal variability will be estimated by comparing chemistry and
water equivalent of wet/dry collector event samples to weekly
samples.
o Inter-instrument sampling variability for two colocated bulk
samplers will be estimated by comparing chemistry and water equiv-
alent for weekly samples.
o A "ground truth standard" for estimating the accuracy of all
collection instruments will be estimated by comparing sample
chemistry to the chemistry of snowpack cores taken to snowboards.
The comparison will be made on samples collected after events.
o A "ground truth standard" for estimating the accuracy of all
collection instruments will be provided by comparing water equiv-
alent of samples collected after events and collected weekly. The
comparison will be made on snow pit density measurements and on
snowboard measurements.
o Instruments and sampling intervals for high altitude, complex
terrain situations will be recommended based on results of all the
above comparisons.
° Operational reliability will be assessed in qualitative terms of
types of instrument malfunctions, length of downtime, cause and
resolution of problems, ease of operation, frequency and difficulty
of maintenance, and sample contamination.
Instruments to be assessed include three Aerochem Metrics Model 301 wet/dry
deposition collectors, two Belfort Model 5-780 weighing rain gages, and two
18-inch-diameter flanged bulk samplers. The wet/dry collector and Belfort
rain gage are the standard instruments used by NADP and by other major
monitoring and research networks. The Belfort gages are unshielded;
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Page 2 of 3
recent studies indicate that the Alter windshield is not effective at wind
speeds greater than 3 mph (Goodison et al., 1981; Goodison and Metcalfe,
1982). The bulk sampler design is identical to that used by the United
States Geological Survey (USGS) in snow studies. Supplemental instru-
mentation includes Science Associates Models 424-1 and 424-2 wind speed/wind
direction sensors and a data acquisition system (DAS) composed of an IBM
at personal computer and Metrobyte logic boards. Snow coring equipment and
the Taylor-LaChapelle snow-density kits used are manufactured by Hydro-Tech.
Snowboards are fabricated by Lockheed-EMSCO of polyurethane-coated plywood.
The collection devices and meteorological sensors are mounted on a 20-foot-
diameter octagonal wooden platform erected on a southeast-facing slope at
the maximum expected snowpack height (19 feet at the point closest to the
ground). Cables connect the sensors to the DAS which is located approxi-
mately 275 feet distant in a heated building. The platform is accessed by
steps located on the uphill (NNE) side. The closest tree tops subtend an
angle of 47° ± 3°. The nearest of several buildings is located 28 feet
NNW of the platform. A fireplace in one of these buildings is a possible
source of contamination; however, the building is more than 500 feet away
and is shielded by other buildings and by trees.
The monitoring equipment and DAS are checked daily by an on-site operator.
In addition, a Lockheed-EMSCO scientist visits the site at least once a
month. During most of the study, samples are collected from two wet/dry
collectors and two bulk samplers on a weekly basis or more frequently as
required by event loading. Samples are collected from the third wet/dry
collector daily. Snowboard cores and snow pit density measurements are
taken weekly. During a 30-day period, two wet/dry collectors are operated
on a daily basis, and the third is operated on a weekly basis. Snow cores
and snow pit density measurements are taken daily as well as weekly during
this same 30-day period.
No analyses are performed in the field. On a weekly basis, all samples
are shipped frozen to Lockheed-EMSCO in Las Vegas, Nevada, where water
equivalents are determined and where melted samples are processed. Process-
ing includes pH and specific conductance measurements, which are completed
immediately after melting, and filtration and preservation of aliquots for
subsequent analysis. Analyses for chloride and ammonium are completed
approximately every two weeks; analyses for metal cations, nitrate, and
sulfate are completed every four weeks. All analyses are completed within
recommended holding times for the chemical variable of interest and pre-
servation treatment used.
Data from the field, processing laboratory, and anaytical laboratory are
compiled into a single database; because of the small size of the database,
an IBM-PC is used for data compilation. Quality control sample data are
used to verify the data; data of poor or unknown quality are deleted.
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Statistical tests, including paired t-tests, %RSD, and means, are employed
to quantify the project objectives. Other interpretative schemes may be
developed dependent upon the initial intra- and inter-comparison results.
An interim progress report, detailing field and laboratory operations,
will be delivered in June 1987. A final project report will be available
in January 1988. The final report will include interpretative results,
assessment of instrument reliability, and recommendations for future snow-
pack monitoring and research.
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3.0 QUALITY ASSURANCE PLAN
The Quality Assurance (QA) policy of EPA requires that every monitoring
and measurement project have a written and approved QA project plan (Costle,
1979a and 1979b). This requirement applies to all environmental monitoring
and measurement efforts authorized or supported by EPA through regulations,
grants, contracts, or other formal means. The QA project plan should
specify the policies, organization, objectives, functional activities, and
specific quality control (QC) procedures designed to achieve the data
quality goals of the project. As used herein, QC is the specific procedures
and checks used to provide a quality product, while QA is the overall
system used to ensure that the QC system is performing. All project
personnel should be familiar with the policies and objectives outlined in
the operations and QA plan to ensure proper interactions among the field
operations, laboratory operations, and data management.
3.1 QUALITY ASSURANCE OBJECTIVES
QA objectives are defined in terms of precision, accuracy, completeness,"
representativeness, and comparability.
3.1.1 Precision and Accuracy
The QA objectives for precision and accuracy of the parameters being
measured are given in Table 3-1. Precision, defined as the mutual
agreement among individual measurements of the same property, is expressed
in terms of percent relative standard deviation (%RSD). Precision is
calculated from results of duplicate analyses and repetitive analyses of
audit samples and quality control check solutions. Accuracy is the
degree of agreement of a measurement with an accepted or true value. It
is expressed as percent bias and is determined from the difference
between recorded measurements and accepted true values of audit samples,
quality control check solutions, and calibration standards.
An additional estimate of precision is provided by the two colocated
wet/dry collectors, Bel fort rain gages, and bulk samplers. It is common
practice in many studies to designate one unit as the primary or routine
sampler and the other as a secondary or duplicate sampler. This practice,
in effect, designates samples from the secondary unit as QC samples.
Because one of the project objectives is estimation of inter-instrument
sampling variability (i.e., quantification of precision limits), units
used in this project will not receive primary and secondary designations.
Consequently, a field duplicate is not included as one of the QC samples
described below. Analysis of the data on colocated samplers is included
in the data interpretation scheme, as discussed in Section 6.0 of this
manual.
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TABLE 3-1. QUALITY ASSURANCE OBJECTIVES FOR DETECTABILITY,
PRECISION, AND ACCURACY
Parameter3 Units
Required
Detection
Limits
Expected Rangeb (NADP)
Precision0
Percent
Relative Standard
Deviation (%RSD)
Upper Limit (%)
Accuracy
Max.
Absolute
Bias (%)
Na+
CT ,
so4'<
N03
S4
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
pH units
Specific yS/cm
Conductance
0.005-
0.010-
0.003-
0.01-
0.01-
0.04-
0.002-
0.003-
5.1-
0.160
0.30
0.051
0.026
1.00
0.32
0.120
0.180
5.9
1.78-6.10
0.03
0.01
0.01
0.01
0.02
0.10
0.02
0.025
pH > 5.
pH < 5.
0.6 yS/cm
5
5
5
5
5
5
10
5
±0.30
±0.10
10-100-3%
> 100 - 1%
10
10
10
10
10
10
10
10
±0.03
±0.10
5%
2%
Dissolved ions and metals are being determined.
bRanges are for snowpack. Laird et al. (1986).
cUnless otherwise noted, this is the %RSD at concentrations approximately
10 times the instrument detection limit.
Modified from: Drouse et al. (1986).
External and internal QA and QC samples include the following:
Field Blank - A field blank is a deionized water sample meeting specifi-
cations for ASTM Type 1 reagent water (ASTM, 1984) that is poured into a
clean sample bucket by the site operator and, thereafter, is treated as
though it were a routine sample. One field blank accompanies each
weekly sample shipment. Field blank data are used to establish the
estimated system background value that can be expected for each type of
chemical analysis. For data interpretation, a data point above the 95
percentile of the field blank value is considered a positive response.
Blanks above the 80 percentile are investigated for contamination.
Bucket Blank - A bucket blank is a deionized water sample meeting spe-
cifications for ASTM Type I reagent water (ASTM, 1984) that is poured
into a clean sample bucket in the processing laboratory and, thereafter,
is processed and analyzed as though it were a routine sample. A minimum
of 5 percent of each lot of washed buckets and lids are retained and
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stored at the processing laboratory until the next sample shipment
arrives. The bucket blanks are then prepared and incorporated into the
sample batch. Bucket blank data are used to establish the estimated
system background values associated with the bucket washing procedure.
Data interpretation is the same as described for field blanks, above.
Audit - An audit sample is a material with known characteristics which
is used to determine the accuracy of the measurement system. Several
types of audit samples are used in this project and are described below.
A processing laboratory audit provides a known measure of pH and spe-
cific conductance. These samples are prepared by a group within Lockheed-
EMSCO, separate and distinct from either the processing laboratory or
analytical laboratory.
An analytical laboratory audit is a set of pre-prepared aliquots that
are incorporated into the batch at the processing laboratory. Five
synthetic audits are prepared for each of three concentration ranges
for each chemical parameter.
National Bureau of Standards (NBS) audit samples are incorporated into
the batch in two ways: (1) as packaged and received, and (2) diluted at
the processing laboratory and packaged as an aliquot set. Six of each
are used.
Field QC methods are limited to (1) sandbag weights used in the field to
measure the accuracy of the Belfort weighing rain gages and to (2)
periodic calibrations of the meteorological sensors and of the Belfort
rain gages.
Internal laboratory QC samples for the processing and analytical labor-
atories include the following:
Initial Calibration - An initial calibration is performed on each day
of analysis or as required for each analytical method. The concentra-
tions of the calibration standards must bracket the expected sample
concentrations. Occasionally, the standards recommended for a method must
be adjusted to meet this requirement. The concentration of the low
calibration standard should not be more than 10 times the detection
limit. If, during the analysis, the concentration of the sample is
above the linear dynamic range (LDR), two options are available. One
option is to dilute and reanalyze the sample. Alternatively, two con-
centration ranges may be calibrated. Samples are first analyzed on the
lower concentration range. Each sample with a concentration exceeding
the upper end of the LDR is then reanalyzed at the higher concentration
range. If the second option is taken, separate QC samples must be
analyzed and reported for each range.
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Quality Control Check Sample - Immediately after the instruments are
calibrated, a Quality Control Check Sample (QCCS) containing the
analyte of interest at a concentration that is in the middle of the
calibration range must be analyzed. The QCCS may be obtained commer-
cially, or it may be prepared by the analyst from a source which is
independent of the calibration standards. The QCCS must be analyzed to
verify the calibration curve prior to any other sample analyses, after
every 10 samples, and after the last sample. If the measured value for
a QCCS differs from the theoretical value by more than five percent
(10 percent for nitrate), the instrument must be recalibrated, and all
samples that were analyzed after the last acceptable QCCS must be
reanalyzed.
The measured concentrations for the QCCS's also must be plotted on a
control chart, and the 99 percent and 95 percent confidence intervals
must be calculated. Monthly the control charts are updated, cumulative
means are calculated, and new warning limits (95 percent) and control
limits (99 percent) are determined. If the 99-percent control limit
differs from the theoretical concentration by more than the limit given
in Table 3-1, the QA manager or laboratory manager must be notified, to
ensure the continuity of the control chart, all of the QCCS's must have
the same theoretical concentration and must be from the same source.
Detection Limit QCCS - A sample containing the analyte of interest at a
concentration two to three times the required detection limit, a detec-
tion limit QCCS, is analyzed once per batch, and the results are reported.
The purpose of the detection limit QCCS is to eliminate the necessity of
formally determining the detection limit on a daily basis. The measured
value must be within 20 percent of the theoretical concentration. If it
is not, the problem must be identified and corrected, and an acceptable
result must be obtained prior to sample analysis.
Calibration Blank - A calibration blank must be analyzed once per batch,
immediately after the initial calibration, to check for baseline drift.
The instrument is rezeroed if necessary. The calibration blank is
defined as a "0" mg/L standard and contains only the matrix of the
calibration standards. The measured concentration of the calibration
blank must be less than or equal to twice the required detection limit.
If it is not, the calibration must be rechecked.
Duplicate Sample Analysis - One sample per batch must be prepared and
analyzed in duplicate for each parameter. The %RSD is calculated as:
S
%RSD = — X 100
X
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- X)2vl/2
S -
where S = the standard deviation of the duplicate pair
X = a datum
"X = the mean of the duplicate pair
n = the number of sample and duplicate (n = 2)
Control limits are set at the precision levels given in Table 3-1. If
the observed precision of a duplicate pair falls outside the control
limits and if the analyte concentration is greater than 10 times the
detection limit, the source of the variability (e.g., instrument mal-
function, calibration drift) must be sought and eliminated. A second,
different sample then must be analyzed in duplicate. Further samples
may not be analyzed until the duplicate sample results are within the
prescribed 3&RSD limits, unless the QA manager gives approval.
3.1.2 Completeness
Completeness refers to the amount of valid data that is obtained from a
measurement system compared to the amount expected to be obtained under
normal conditions. The completeness objective for total possible
field observations of event, daily, weekly, or longer term composite
samples is 80 percent. Instruments that do not to meet this objective
also do not meet the project objective of operational reliability.
3.1.3 Representati veness
This study is designed to achieve the objectives outlined in Section 2.0.
As the objectives primarily relate to collection variability, the data
are representative if sources of variability other than collection are
minimized or eliminated. Independent quality control checks are associated
with each step of operation, analysis, and interpretation. These checks
are designed to quantify and minimize the variability inherent in each
step. This process reduces sources of variability including processing,
analysis, and operator variability.
Spatial variability represents an exception. Snowpack depth recordings
are taken at-multiple points in an attempt to quantify spatial variability.
However, these measurements are taken at ground level; spatial variability
across the platform, including the possible effect of the close clustering
of instruments, is not quantifiable in this design. An assumption has
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«. been made that spatial variability is insignificant in relation to
collection variability.
3.1.4 Comparability
Most of the project objectives are stated in terms of comparisons, includ-
ing comparisons of same and different sampling methodologies and compari-
sons of same and different sampling intervals. These comparisons require
that the data be reported in a uniform set of units. A uniform set of
procedures for the site and laboratory ensures that any observed vari-
ability is due to the variable of interest rather than to a lack of
comparability in sample collection or treatment. Uniform units and
procedures, coupled with data quality estimates, permit comparison of
data collected in this study to data collected in other snow monitoring
and research studies.
3.2 FIELD OPERATIONS QA
The field QA/QC program includes consideration of siting criteria, facil-
ities, instrument operation, sample handling, and documentation. Avoid-
ance of sample contamination is of particular concern because the samples
are of low ionic strength; analytes introduced by simply touching the
bucket interior may exceed analyte concentrations present in the sample.
Continuity of field operations is ensured by adherence to documented
protocols. These protocols or standard operating procedures (SOP's) are
discussed in Section 4.0.
3.2.1 Siting Criteria and Facilities
The siting criteria set forth in the draft document by Svoboda and Olsen
(1986) are met as closely as possible. These criteria include consider-
ation of spacing from objects which may influence micrometeorological
conditions, separation from sources of local pollutants, and orientation
of collection devices. A complete site description, including photo-
graphs, is to be included in the project documentation.
Facilities requirements include adequate electrical power, site
accessibility during events, accessibility to shipping facilities,
heated sheltering for the DAS, cold storage for samples, and a clean
area for sample handling. The selected site meets all of these needs.
The University of Denver High Altitude Research Laboratory supplies
electrical power and on-site heated facilities for site operator
residence, DAS shelter, and sample handling. Collected samples may
be stored in an unheated building since ambient temperature should
provide adequate refrigeration. A United Parcel Service (UPS) facility
is located in Idaho Springs, and the site access road is kept open
year-round.
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3*2.2 Instrument Operation
In this project, collection instruments of the same model are intra-
compared to estimate sampling variability and different model instru-
ments are compared to each other and to "ground truth" measures to
estimate sampling accuracy. Instruments are also evaluated in terms of
operational reliability. To achieve these objectives, it is imperative
that the instruments be operated so as to achieve maximum performance and
so that complete, detailed records be maintained of field operations.
Detailed SOP's that are based on manufacturers instructions and on
experience gained in previous studies ensure peak performance and
comparability of sampling methods. The SOP's contain instructions for
calibration, QC checks, routine and preventive maintenance, operator
checks, and troubleshooting. A limited spare parts inventory is main-
tained to minimize downtime caused by component malfunction. Supplies
of consumable items are maintained and periodically are inventoried to
ensure uninterrupted operation. Each instrument is operationally tested
prior to deployment and again upon installation. The site operator
undergoes a training program including "hands-on" experience prior to
initiation of sampling. Monthly on-site visits by a Lockheed-EMSCO
scientist include evaluation of operator performance and "refresher"
training.
Field documentation includes outputs of the DAS, field forms that
accompany sample shipment, and an operator logbook. The operator is
encouraged to record all observations in the logbook. The logbook
also serves as a calibration and maintenance record and tracks mal-
functions from symptoms through final resolution.
3.2.3 Sample Handling
Parameters used for instrument comparisons are snow chemistry and water
equivalent. It is essential that samples be handled so as to minimize
potential contamination or sample loss. During the collection period,
the reciprocating lid of the wet/dry collector must operate properly by
exposing the wet bucket during periods of precipitation and by sealing
tightly during dry periods. The foam lid seal surface also must be
clean to avoid contamination. Wind scour is a potential source of
sample loss for all collection devices. Wet/dry collector and bulk
sampler collection vessels (buckets and bags, respectively) should be
checked frequently and should be changed if nearly full. A line indicat-
ing volume is marked on the collection vessel immediately after removal,
i.e., before any contents settling occurs. An antifreeze/oil mixture
helps prevent wind scour and evaporative losses from the Bel fort rain
gages.
The site operator wears sterile or clean rubber gloves when touching
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sample collection vessels. Wet/dry collector buckets are sealed with
the lid accompanying the to-be-installed bucket rather than with the lid
that accompanied the to-be-removed bucket. Any post-sampling in-field
washing, e.g., washing of the snow density and coring equipment, is done
with deionized (DI) water prior to sampling, and snow density and coring
equipment are rinsed with visually clean snow of the same type that is
to be sampled. All collected samples are sealed and placed in clean
plastic bags for storage and shipment.
3.2.4 Documentation
Field documentation includes:
o DAS outputs
o Field forms
o Bel fort rain gage charts
o Operator logbook
o Photographs
The recording medium for the DAS is floppy diskette. In addition,
hardcopy outputs may be obtained from the printer. Disks are retrieved
and are transported to Las Vegas by a Lockheed-EMSCO scientist monthly.
Hardcopy outputs accompany weekly sample shipments.
The field form (Figure 3-1) is completed and is shipped with the samples.
The form is in triplicate; one copy is retained by the site operator,
and two accompany the samples. Of these, one is retained by the
processing laboratory, and the other, after QA review, is submitted for
data entry. Bel fort rain gage charts are attached to the data entry
copy and are shipped weekly.
The operator logbook contains duplicate numbered pages. All entries
are carbon-copied to the duplicate page. Duplicate pages accompany
each sample shipment. The operator maintains the original, bound log-
book until study completion. The operator also photographs site
conditions daily. Exposed film rolls are retrieved during the monthly
on-site visits and are processed in Las Vegas.
3.3 PROCESSING LABORATORY QA
The processing laboratory functions include calculation of water equiva-
lent, measurement of pH and specific conductance, preparation of aliquots
for subsequent chemical analyses, and provision of field-required sup-
plies including washed buckets. Processing laboratory protocols are
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WET DEPOSITION AND SNOWPACK FIELD DATA FORM
YY MM DO Start: / / YY MM DD End:
/ / OPERATOR:
NTN 1 Weekly MTC MM/OD HH/MM • HH/MM:
ON MHDD
OFFMMDO
FU. HCT. (CM.)
BUCKET/110 WEIGHT
BUCKET
BUCKET
BUCKET
BUCKET
BUCKET
BUCKET
BUCKET
NTN 2 Weekly MTC:
ON MMOO
HHMM
OFFMMDD
HHMM
FU HGT. (CM.)
BUCKET/LID WEIGHT
BUCKET
BUCKET
BUCKET
BUCKET
BUCKO
BUCKET
BUCKET
NTN 3 Weekly MTC:
ON MMDD
HHMM
OFF MMOO
FU. HGT. (CM.)
BUCKET/LID WEIGHT
BUCKET
BUCKET
BUCKET
BUCKET
BUCKET
BUCKET
BUCKET
BULK SAMPLERS
BIII K 1 (USE 2ND COLUMN ONLY F
BULR ' BAG REPLACED MD-WEEK)
ON
OFF
FUHGT.
BUCKET/LID WEIGHT
BELFORT RAIN QAQES
BULK 2
(USE 2ND COLUMN ONLY IF
BAG REPLACED MID WEEK)
SNOW CORES
UHfT 1 UNIT 2 Weekly Simples « C4 f"«r- >«" scif"*rr«CrT
CHART ON
MMOO HHMM
CHART OFF
MMOO HHMM
AtmniEEZE CHANGE
MMOO II MM III MM
QCCS (M.)
RTE HGT. OOP HGT.
Y !»WM
M HEIGHT
S HEIGHT
ROUTME HEIGHT
OOP HEIGHT
SHIPPING INFORMATION Date Shipped: /
TAKEN MMOO HHMM
/ * of Shipping Containers:
SAMPLE ID NUMBERS
BUCKETS
BAGS
CORES
HELD BLANK
TOTAL
Comments: .
List Supplies Needed:.
* of dean buckets on-site:.
Figure 3-1. Snowpack field data form.
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based on procedures developed for the National Surface Water Survey (NSWS),
including a snowpack survey (Chaloud et al., 1986)
3.3.1 Water Equivalent
Water equivalent is calculated from sample weight and volume. The
sample depth is marked in the field; sample volume is calculated to the
nearest cubic centimeter (cm^). Weights are recorded to ±1.0 g. QA/QC
checks for the scale include calibration with a minimum of three NBS-
traceable weights encompassing the range of sample weights and a check
of a single weight after every 10 sample weights. Calculations are
made on a programmable calculator to minimize arithmetic errors. All
data, including bucket tareweight, sample depth and weight, balance
calibration and QC check values, and calculated volume, density, and
water equivalent, are recorded in a dedicated logbook. At least 10
percent of all values are reviewed and hand-calculated to check for
transcription and transposition errors.
3.3.2 £H
Because melted snow samples are at atmospheric equilibrium with respect
to carbon dioxide (COg), all pH measurements are made on sample aliquots
in centrifuge tubes or beakers (open system). Two-point temperature
calibrations are performed weekly; a single-point temperature check is
performed daily. The meter calibration is checked each day against pH
4.00 and 7.00 NBS-traceable standards. A pH 4.00 QCCS is checked prior
to sample analysis, after every 10 samples or mid-batch (whichever is
fewer), and following analysis of the last sample. One sample is
measured in duplicate.
3.3.3 Specific Conductance
The conductivity meter is checked daily with NBS-traceable resistors.
(The conductivity cell function is checked daily with a potassium
chloride [KC1] standard and a calibration blank.) At least one QCCS,
prepared from a different stock solution than the calibration standard,
is checked prior to sample analysis, after every 10 samples or mid-batch
(whichever is fewer), and following sample analysis. One sample is
measured in duplicate. By using the calibration standard, a cell
constant is calculated at the beginning and end of each batch. All
measurements are made at 25°C; a temperature-controlled water bath is
used to maintain constant temperature.
3.3.4 Aliquot Preparation
Filtration is performed in a clean air station set to deliver a positive
flow of class 100 air. Acid-washed and non-acid washed filtration units
are labeled and are separated by a plexiglass shield. Vacuum pump
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pressure is checked daily. Ultrex acids and reagent-grade mercuric
chloride are used as preservatives. Aliquots are prepared immediately
upon completion of melting; processed aliquots are refrigerated at 4°C.
A description of the aliquots is given in Table 3-2.
3.3.5 Field Support
Support of field operations includes provision of washed sample buckets
and lids, DI water for field blanks, frozen gel packs, plastic bags,
shipping containers, and miscellaneous consumable items. At least
5 percent of all washed buckets and lids are processed as bucket blanks
as a check of the bucket washing procedure. The specific conductance
of the DI water produced in the processing laboratory by the Millipore
system is analyzed weekly or more often to verify that it meets the
ASTM Type I requirements for specific conductance (<1 yS/cm at 25°C;
ASTM, 1984).
3.3.6 Documentation
Upon receipt, shipping container temperatures are measured and are recorded
on the field data form. Sample identification is verified prior to
assignment of batch and sample numbers. Each laboratory procedure is
documented in a bound logbook. Results, including QC data, are transcribed
onto multiple-copy batch forms. One copy is retained at the processing
laboratory while the original is sent to QA personnel for verification
and data entry. Processing laboratory results may also be recorded on
floppy disk. A shipping or chain-of-custody form accompanies aliquot
transfer to the analytical laboratory.
3.4 ANALYTICAL LABORATORY QA
The analytical laboratory analysis schedule is shown in Table 3-2. Ana-
lytical protocols are fully documented and tested, having been previously
used in (NSWS) (Hiljman et al., 1986). QA/QC protocols also are those
used in NSWS (Drouse et al., 1986).
Data reports, both hardcopy and floppy disk, are prepared monthly. These
reports include analytical results, in milligrams per liter (mg/L), and
QA/QC data. Copies are retained in the analytical laboratory; the orig-
inals are sent to QA personnel for verification and data entry.
3.5 DATA EVALUATION
All data are reviewed for compliance with QA objectives prior to any
interpretation of results. This evaluation of data quality is completed
as soon as data are received so that problems can be detected and cor-
rected rapidly. Values associated with poor QA/QC data or outside the
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1 TABLE 3-2. PROCESSING LABORATORY ALIQUOT DESCRIPTION AND ANALYTICAL
LABORATORY ANALYSIS SCHEDULE
Analyte Aliquot Description Analysis Schedule
Ca2+, Na+, 125-mL Nalgene bottles monthly
K+, Mg2+ (acid washed), filtered
(0.45-ym HA type filter),
preserved with HN03
to pH < 2
NOo", S042" 125-mL Nalgene bottles monthly
(non-acid washed), filtered
(0.45-ym HA type filter),
preserved with HgCl2
(0.15 M)
CT 125 mL-Nalgene bottles bimonthly3
(non-acid washed), filtered
(0.45-ym HA type filter),
no preservative
NH4+ 125-mL Nalgene bottles bimonthly3
(acid washed), filtered
(0.45-ym HA type filter),
preserved with H2S04 to
pH < 2
30r within required holding times.
expected range (see Table 3-1) are flagged, and the sample is reanalyzed
(if possible), or the value is excluded from interpretative use.
3.5.1 Audit Sample Acceptance Criteria
Acceptance windows for single values from audit samples are based on
previous inter!aboratory analyses of the same sample material. The
objective of creating windows is to predict intervals for acceptable
single future values based on a sample mean (x) and sample standard
deviation (s) computed from n previously observed values. The limits
of the windows are determined by using a t-statistic (t).
Z
t = is a "Student's" t-statistic
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where: Z is the standard normal variate having a normal distribution
with a mean of 0 and a variance of 1
y is a variable with chi-square distribution that has r degrees
of freedom, and
Z and y are independent.
The observed values X^, X£, Xj,...Xn are independent and have a normal
distribution (~N) with a population mean (y) and variance (a2). A
(1 -_a) prediction interval for a single future value y is needed.
Let x = sample mean and s = sample standard deviation. It is known
that
Therefore,
~ N (y, a2) and x ~ N y, \ n/.
y - x ~
z =
y -
N(0,
Substituting,
n-1 —~ x2 (n-1) and
a2
r = n-1.
t =
y -
\ 1 + n
y - x
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The upper and lower limits of the window can be formalized as follows:
x" + (t)(s) 4/1 + - = upper limit of the window
n
~ (t)(s) \l + - = lower limit of the window
1 n
The Student's t-value (t) has n-1 degrees of freedom. The t-value is
for a 2-tailed test with a cumulative probability of 0.975 (i.e., 2.5
percent probability on either side).
For predicting future values, wider windows than the standard 95 percent
confidence interval about the mean are desirable. As the number of
observed values increases, more variance occurs because of chance alone.
Grubbs' test (Grubbs, 1969) is applied to the data before interval
estimation is used to detect outliers. The outliers are excluded from
the computation of the windows.
Windows for matrix spike analysis results are computationally identical
to those for audit sample results.
3.5.2 Duplicate Sample Acceptance Criteria
Acceptance criteria for the %RSD are based on the upper 95th percentile
of observed values of %RSD. Because the %RSD is affected by concentra-
tion, these criteria are applied only when the mean of the duplicate
analyses exceeds the detection limit by a factor of 10. Arbitrary
acceptance criteria may be used until sufficient (at least 10) %RSD
values have been observed.
The distribution of the %RSD values cannot be estimated accurately until
the sufficient %RSD values have been observed. It is recommended that
no outlier test be applied until the distribution has been estimated.
3.5.3 Blank Sample Acceptance Criteria
Field and bucket blanks must be less than five times the minimum
detection limit or, failing that, must constitute less than 20 percent
of the mean total analyte concentration of routine samples. Analytical
blanks must be less than three times the minimum detection limit.
3.5.4 Holding Times
The processing laboratory analyses are performed within 24 hours of
completion of melting. The analytical laboratory analyses of chloride
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and ammonium are performed approximately every two weeks or within the
the required holding time; analyses of cations (Na, K, Ca, and Mg),
sulfate, and nitrate are performed every four weeks. These schedules
are less than the maximum recommended holding times shown in Table 3-3.
3.5.5 Data Flags
Flags are applied to the entire batch of samples if the batch QA sample
data do not meet the acceptance criteria given above. Each parameter is
also flagged if internal QC checks such as matrix spike recovery, cali-
bration and reagent blank analytical results, internal duplicate pre-
cision, instrumental detection limits, QCCS analytical results, or
required holding times do not meet specifications. Flagged data are
reananalyzed, if possible, or are excluded from data interpretation.
TABLE 3-3. LIST OF MAXIMUM RECOMMENDED HOLDING TIMES
=====================================£=======================================:==
Holding Time Parameter
7 days N03',a pH,b
14 days Specific conductance
28 days NH4+, Cl", S042'
6 months0 Ca, Mg, K, Na
aAlthough the EPA (U.S. EPA, 1983) recommends that nitrate in unpreserved
samples (unacidified) be determined within 48 hours of collection, evidence
exists that nitrate in mercuric chloride preserved samples is stable for up to
3 months (Suarez, personal communication, 1987).
bAlthough the EPA (U.S. EPA, 1983) recommends that pH be measured immediately
after sample collection, evidence exists (McQuaker et al., 1983) that it is
stable for up to 15 days if stored at 4°C and sealed from the atmosphere.
Seven days is specified here as an added precaution.
cAlthough the EPA (U.S. EPA, 1983) recommends a 6-month holding time for these
metals, this study requires that all of the metals be determined within 28
days. This is to ensure that significant changes do not occur and to obtain
data in a timely manner.
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4.0 FIELD OPERATIONS
The equipment installed at the monitoring site includes wet/dry collectors,
Bel fort rain gages, bulk samplers, wind speed and wind direction sensors,
and a data acquisition system (DAS). All of these, with the exception of
the DAS, are mounted on the raised sampling platform. Additional measure-
ments are taken on the ground within a clearing. Snowboards provide a
base for core samples which are collected on an event and weekly basis.
Density measurements are performed in a snow pit. Responsibilities of the
site operator include sample collection, handling, and shipment; instrument
calibration, maintenance, and quality control checks; equipment trouble-
shooting and repair; and documentation of all field activities. The
following sections detail each of these aspects of field operations;
ground-level measurements are treated in a separate section.
4.1 EQUIPMENT AND SUPPLIES
The equipment and supplies required for operation of the monitoring site
are listed in Table 4-1. Each piece of equipment is assembled and tested
upon receipt and is tested again following installation on the monitoring
platform. Specifications, assembly instructions, and operations tests are
described below.
4.1.1 Wet/Dry Collector
The Aerochem Metrics 301 Model wet/dry deposition collector depicted in
Figure 4-1 has two containers and a common lid topped by a peaked roof to
minimize snow buildup. The lid seals the wet sample bucket when precipi-
tation is not occurring and thus minimizes evaporation and contamination
by dry deposition or dustfall. When precipitation occurs, the lid moves
off the wet bucket and covers the dry deposition bucket.
To monitor the movement of the collector lid, an event recorder output
signal is provided. A continuous 12-volt direct current (DC) signal is
present during wet collection; a 0-volt DC signal is present during dry
collection. Two polyethylene buckets are generally used to collect wet
and dry deposition. The common lid is driven by a motor that is con-
trolled by a rain sensor. The sensor contains a face plate with a grid
closely spaced above it; when the grid and plate are shorted by a drop
of water (precipitation), the motor is actuated to lift the lid from the
collection bucket. The sensor contains two heating circuits: one is
activated during non-event periods when ambient temperature is below 4°C;
the second is activated during events to increase sensor temperature to
about 55°C. The first prevents ice accumulation on the sensor grid
while the second increases evaporation to permit accurate detection of
the end of the event. Heating increases the rate of water evaporation
from the sensor and hastens the closing of the wet bucket by the lid
after precipitation ceases. This procedure minimizes the exposure time
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TABLE 4-1. FIELD EQUIPMENT LIST
Equipment/Materials Quantity
Aerochem Metrics wet/dry collector 3
Collection buckets with lids 9
Fuses 1/2 Amp (120 V AC operation) ' 12
Fuses 2A (for DC operation) 12
Precipitation sensor and motor box 3
Peaked aluminum snow roof 3
Belfort Rain gage (weighing type) 2
Rain gage clock 2
Rain gage chart paper 2
Rain gage ink 2
Science Associates wind speed sensor 1
Science Associates wind direction sensor 1
Cup assembly 1
Vane assembly 1
Power and distribution assembly 1
Shielded cable 500 ft 1
IBM PC AT computer 1
Sysdyne graphics adaptor 1
Sysdyne amber monitor 1
Okidata 293 printer 1
Floppy disk 1
Light bulbs 60 W 1
Teflon spray 1
Taylor Hydro-Tech snow corer and extensions 1
Snow shovel 1
Snow knife 1
Spatula 1
Taylor-LaChapelle snow density kit 1
to dry fallout. A seal between the bucket and the lid is achieved by a
plastic foam gasket under the lid and by a spring load; however, with
strong winds the lid may wobble, and some contamination may enter the
wet bucket.
Assembly and Site Installation
Assemble the unit according to the instructions provided by the manu-
facturer. The counterweight is in two parts; the smaller of the two is
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LID MOVES FROM
ONE BUCKET TO ANOTHER
PLASTIC
BUCKET
THERMISTOR SENSOR-PLATE
ACTIVATES MOVEABLE LID
WHEN WET PRECIPITATION
OCCURES
SUPPORT
BRACKET,
LIGHT
BULB
PEAKED
SNOW ROOF
PLASTIC
BUCKET
ALUMINUM
TABLE
MOTOR BOX ...
(UNDER TABLE TOP) R
AUXILIARY
D.C. POWER
12 VOLTS
SUPPORT
BRACKET
Figure 4-1. Aerochem Metrics wet/dry deposition collector.
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added to counterbalance the peaked snow roof. If proper counterweighting
is achieved, the lid will move to mid-position unassisted. Next, add
the snow roof and recheck the balance. If necessary, add weight to
the rod or existing counterweight until the lid moves to mid-position
unassisted.
The wet/dry collector should be mounted so that the rims of the buckets
are level and are at least 1 meter above the platform. Because of its
large cross-section and relatively low weight, the wet/dry collector is
susceptible to being blown over in high winds. Therefore, it is essential
to anchor the unit firmly to the platform with two 5/16-inch bolts and
nuts. Holes in the platform and the two sections of aluminum will have
to be drilled at the site after the wet/dry collectors have been spaced.
The distance between collectors or neighboring rain gages must be equal
to or greater than the height of the taller object. Correct spacing
will minimize interference.
Acceptance Tests
Wet/dry collector acceptance tests are conducted before the collector is
used in the field. These tests include: (1) heating the sensor and
checking that the lid activates when the sensor is shorted with water
drops, (2) cooling the sensor and checking that the lid returns to the
wet-side bucket when the water is removed (sensor may be wiped dry), (3)
checking that the sensor temperature reaches 50° to 60°C when the lid is
off.the wet bucket, (4) checking that the sensor temperature reaches 1°
to 2°C when ambient temperature falls below 4°C; and (5) checking that
the lid cycling and sealing operation is correct. The procedures to be
used for these acceptance tests are outlined below:
a. With the collector lid in its normal position over the wet bucket,
add several drops of water to the sensor. The lid should move off
the bucket within seconds and should cover the dry bucket. After
the water evaporates, the lid should return to cover the wet bucket.
If there is no response, check to see that the sensor is connected
to the motor box and that the power is on. If the connection is
complete, the sensor or motor box is probably faulty and should be
replaced. To remove the box, see the instructions provided by the
manufacturer.
b. Affix a temperature probe (thermistor, thermometer, or thermocouple)
to the sensor plate near the screw head in the plate. Make sure the
contact is good, and cover the probe with an insulating material.
Short the grid and plate together with a paper clip or coin. In a
few minutes the temperature should start to climb and should level
off at 50° to 60°C. If the temperature setting is incorrect, it can
be adjusted by turning the potentiometer screw inside the sensor
box. Directions are given in the instructions provided by the
manufacturer.
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t c. Remove the shorting object. The lid should close within a few
seconds, and the temperature should fall to ambient.
d. During steps b and c, check that the lid does not cycle. Also check
the lid seals.
e. If the lid does not seal the wet bucket, check to see whether or not
the plastic foam gasket is secured in the correct position. To
remove the seal, see the instructions provided by the manufacturer.
If this is not the problem, call the manufacturer.
f. If the lid cycles while the sensor is shorted, the cause is probably
a bad magnetic switch in the motor box or the lid arm that actuates
the switch. The arm may be loose or may have moved too far out
(more than 1 mm) from the switch as it passed the switch during lid
movement. If the latter is the case, the lid arm can be adjusted
and secured by tightening the 1/4 x 20 head screw in the bronze
collar that secures the arm and the clutch to the motor shaft.
g. Check the sensor heating circuit at freezing temperature. The
Aerochem Metrics collector has a standard heater/ammeter test plug
which connects the sensor and the table cannon plugs. When the
heater goes on, 0.6 to 0.7 A of current flows through the heater.
The sensor can be cooled at warm temperatures by unscrewing the
sensor probe from the collector table and by placing it in a refrig-
erator freezer compartment. A temperature probe on the sensor will
give its temperature. Current should flow when the temperature
falls to 0° to 2°C. The temperature setting of this circuit cannot
be altered except by changing the resistor in the circuit.
If any of the above tests indicate a malfunction, the problem must be
remedied or the apparatus must be returned to the manufacturer. In
general, the operator can rectify the problem by replacing the sensor or
the motor box. Do not replace any switches.
4.1.2 Bel fort Recording Rain Gage
The Bel fort 5-780 series recording rain gage is a weighing gage that
converts the weight of the precipitation caught by an 8 inch diameter
cylindrical collector into the curvillinear movement of a recording pen
(Figure 4-2). The pen makes a trace on a rectangular paper chart that
is graduated in centimeters or millimeters of precipitation.
Sensitivity: 0.01 cm of precipitation
Chart timing: within 14 minutes/week accuracy
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— 8-3/32'OD.
35-3/8'
17/64'D. HOLE,
3 PLACES
120°APART
3/8'D. HOLE.
3 places
120° APART
5-3/8'R.
SCALE
3-5/8BR.
Figure 4-2. Bel fort weighing rain gage.
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Assembly and Site Installation
Mount the rain gage on a firmly anchored support. Make sure that its
funnel rim is level and at the same height as the collector rim of
the Aerochem Metrics samplers. This procedure enables comparisons of
collection amounts between the two instruments. The Bel fort gage can be
mounted with three bolts to a level platform. The gage level can be
checked with a carpenter's level placed at two intersecting positions.
Position the rain gage to prevent or minimize blowing dirt or snow from
entering the access door for the chart drive. Never oil any part of the
gage except the chart drive mechanism.
Acceptance Tests
Rain gage acceptance tests should include checks on the following:
(1) sensitivity and accuracy, (2) clock function, (3) pen and recorder
function, and (4) event pen function. The procedures to be used for
these acceptance tests are outlined below.
a. With the weighing rain gage level and zeroed, add water equivalent
to several inches of precipitation. For the Belfort rain gage 5-780
series, 1 inch equals 824 g of water.
b. If the rain gage does not read correctly, adjust it according to the
instructions provided by the manufacturer.
c. With the pens inked and a chart in place, turn the drum to produce
a zero-level trace; add water equivalent to 0.51 mm (0.02 inch) and
measure the response. (For the Belfort recording rain gage 5-780
series, 0.51 mm equals 16.4 g [0.02 inch]). If there is no response
or if the response is more than 1.0 mm (0.04 inch), call the manu-
facturer.
d. Wind the chart drive (or clock) until it is fully wound, and set it
for the correct time. Let the clock run for at least 24 hours, and
check the pen traces and the clock time. The time should be correct
to within 0.5 hours over 24 hours. If the clock does not meet this
specification, it should be replaced. If any other problems are
evident, the instructions provided by the manufacturer should be
consulted.
4.1.3 Bulk Sampler
The bulk sampler is an 18-inch by 6-foot galvanized metal cylinder.
A hose clamp permits attachment of a polyethylene bag. The top of the
cylinder is open to the atmosphere. No special assembly or acceptance
tests are required. The bulk samplers may be mounted to the platform by
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means of a tie-strap secured to the platform. Alternatively, the sampler
may be lowered through a hole cut in the platform and may be secured
from below.
4.1.4 Science Associates Wind Speed and Wind Direction Sensors
The Science Associates Model 424-1 wind speed and 424-2 wind direction
sensors are the same types used by NOAA for airport observations under
severe conditions.
The wind speed transmitter is essentially a direct current, permanent
magnet generator with a cup-wheel directly attached to its armature
shaft. The output voltage of this unit, which is directly proportional
to the rate of cup-wheel rotation, is applied to a remotely located
voltmeter indicator that has been calibrated to indicate wind speed in
terms of miles per hour or in terms of knots, depending upon the
measurement system selected. (The output of the transmitter has been set
up at such a value that an additive constant can be used for all wind
speeds.) This constant correction is applied by changing the rest
position of the indicator pointer from 0 to 2.0. The transmitter-
indicator system is entirely self contained and requires no external
source of electrical power for operation.
The wind direction transmitter contains a resistance coil in toroid
form; two brushes spaced 180° apart move around the edge of the coil.
The brushes are attached to the wind vane shaft and turn with the shaft.
The energizing voltage, 12 volts DC, is introduced into the coil by
means of these brushes, and movement of the brushes causes varying
voltages to appear at the three equally spaced taps on the toroid coil.
These voltage changes are transferred to the indicator where three coils
mounted at equally spaced intervals around a circular iron core are
located. A small permanent magnet, which is located at the center of
the iron core and which supports the indicator pointer shaft, follows
the magnetic field through the coils and causes the pointer to indicate
the direction of the wind. Prime power for operation of the wind direc-
tion system is obtained from a 115 volt, 60 cycle source. This is
converted to the required 12 volts of DC power through a step-down
transformer and a dry disc rectifier located in the power supply and
distribution assembly.
Assembly and Site Installation
Wind Speed Transmitter Installation—
Unpack the cup-wheel and transmitter body with care. This is especially
important in the case of the cup-wheel which is capable of withstanding
wind speeds of 170 mph without damage but which easily can be thrown out
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of balance and calibration if subjected to rough handling. After in-
specting the components for damage and for loose parts, remove the
adaptor from the case of the transmitter body and install it on the
supporting pipe. Do not remove the length of two conductor cords soldered
to the connector in the adaptor. Use the connector to splice to the
connecting cable from the power and distribution assembly. With the
adaptor installed, remove the cap nut from the top of the transmitter
body shaft and place the cup-wheel in position on the shaft. Tighten the
lateral set screw in the cupwheel hub and replace the cap nut firmly.
Place the transmitter on the adaptor and rotate the transmitter until
proper seating of the coupling connectors takes place, which is indicated
by a sudden lowering of the transmitter body to a full seated depth on
the adaptor. Lock the transmitter body in place on the adaptor by
securing the two hexagonal lock screws in the body.
Wind Direction Transmitter Installation--
As with the wind speed transmitter components, exercise care in unpacking
the wind vane and transmitter body. This is important in the case of .
the wind vane; rough handling can cause misalignment. After inspecting
the equipment, remove the adaptor from the transmitter body and place it
on the IPS 1 1/4-inch pipe support. Lock it firmly in place by means of
the two hexagonal cap screws. Use the length of five conductor cables
attached to the adaptor to splice to the main connecting cable from the
power and distribution assembly. Remove the cap nut from the transmitter
shaft and place the wind vane in position on the shaft. Tighten the
locking screw on the wind vane hub, taking care that the screw binds
firmly on the flat side of the transmitter shaft.
Mount the transmitter on the adaptor and secure it by tightening the
locking screws that are similar to the screws on the wind speed trans-
mitter. For proper orientation, the alignment marks on the transmitter
body must match the mark on the adaptor. The mark on the adaptor is
normally oriented to magnetic north.
Connections
All joints (wire splices) are made by soldering and taping in an approved
manner. Note the color coding of the conductors that are used for the
wire splices and connect them to the power and distribution assembly as
follows:
Wind speed transmitter Power and dist. assembly
A F
B G
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t Wind direction transmitter Power and dist. assembly
A A
B B
C C
D D
E E
The power and distribution assembly is located in a temperature-controlled
area with the DAS. Connect the power and distribution assembly to a
110 V AC source. Outputs from this assembly are as follows:
Wind speed Wind direction
L H
M J
K
Additional signal conditioning may be required for the wind direction
output before it is recorded by the DAS.
Acceptance Tests
Acceptance tests are limited to calibration, as described in Section
4.4, and to verification of proper interface to the DAS.
4.1.5 Data Acquisition System
The DAS consists of (1) an IBM-PC AT computer with a 12-V DC battery
backup (to be used in the event of station power failure) and a 360-KB
floppy disk drive, (2) a DAS-8 interface for analog to digital conver-
sion and timing, (3) a PIO-12 interface for digital input/output signals,
and (4) a SRA-01 module board with the IDC-05 solid state input/output
modules to sense and convert higher than 5-V DC voltages to TTL level
signals. Other instrumentation and software that support the computer
include a math coprocessor 80287, PC DOS, graphics adaptor module,
Sysdyne amber monitor, and Okidata 293 printer.
Assembly and Site Installation
Assembly instructions are contained in the manuals provided by the
manufacturer. At the field site, the DAS is housed in a temperature-
controlled building and is connected to the monitoring instruments via a
buried cable.
Acceptance Tests
Most of the equipment from Metrabyte and IBM have internal system
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diagnostics programs. These system diagnostic checks are performed
after the equipment arrives. Some other areas of concern are data
conversion and timing accuracy, memory capacity, recovery of data from
disk, and power failures.
Data conversion and timing accuracy involves applying a constant voltage
source to all analog inputs, then allowing the DAS to scan all input
channels at specific intervals, to record the data on disk and to provide
a printout copy to the user.
To minimize the effect of power failures, an uninterruptable power
source (PS) is connected to the DAS. PS is expected to keep the system
running for not longer than 30 minutes.
4.2 CALIBRATION, MAINTENANCE, AND QUALITY CONTROL
Calibration, maintenance, and QC checks are all elements of the field
QA/QC program. Calibration is adjustment of an instrument response to
known values of standards. A QC check is a periodic check, without
adjustment, of instrument response to a known-value standard. Generally,
QC checks are performed more frequently and employ different standards
than do calibration checks. Maintenance consists of tasks performed on a
set schedule to ensure operational reliability. Some maintenance tasks
are specific to winter operations.
4.2.1 Wet/Dry Collector
There are no calibration or QC check procedures.
Maintenance
Weekly, test the precipitation sensor by placing two or three drops of
water on the sensor grid. The top will then expose the wet-side col-
lector, and the event signal will indicate a logic high ( + 12-V DC at
the unit or a logic high [1] at the DAS). Within several minutes, the
top will return to its original position, and the event signal will
indicate a logic low (0) at the DAS or a 0-V DC level at the precipita-
tion collector. Faulty sensors should be removed and replaced, and the
faulty sensor should be returned to Aerochem Metrics for repair or
exchange.
Weekly, wash the sensor grid with clean water to remove any accumulation
of materials that would close the circuit and would present a false
event signal. A shorted sensor can be verified by unscrewing the cannon
plug connector at the motor box. When the sensor is disconnected, the
cover will always position itself over the wet-side bucket. To clean
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the space between the sensor grid and the plate, cut a strip of card-
board or manila folder to a width of about 1.8 inch and pass it between
the sensor grid and plate.
Weekly, clean the Aerochem Metrics sampler cover and dry-side bucket rim
with deionized water (if temperatures permit) and wipe it with a clean
laboratory tissue. This procedure removes loose dirt on the cover and
removes any excess buildup that would contaminate the samples. Replace
the dry-side bucket every 3 weeks.
Winter Operation
The two most common problems encountered during winter operation of the
Aerochem Metrics sampler are that the collector lid freezes to one of
the buckets and that the lid is immobilized because of heavy snow or ice
accumulation.
To help prevent both of these problems, the peaked snow roof has been
modified for heating capability: a light bulb has been installed
which must be checked periodically or changed to ensure proper heating
operation. Increasing the rating of the light bulb will increase the
heating capability.
Gaiters or boots may be installed on the cover arm to prevent freezing
of the joint. Weekly, lubricate the moveable joints with Teflon or
graphite spray. Spraying should be done only when the sampler lid is
covering the dry-side bucket and there is not a bucket in the wet side.
4.2.2 Bel fort Rain Gage
Because winter operation includes use of an antifreeze-oil mixture that
must be emptied to perform calibration or QC checks, the schedule for
these activities may be shifted slightly to coincide with needed anti-
freeze replacements.
Calibration
Two types of calibrations are recommended for the Bel fort 5-780. A
single-point check should be performed monthly; and a multipoint calibra-
tion should be conducted twice a year, at initial setup and 6 months
later.
1. Once a month, add several known weights to the rain gage to measure
the accuracy. For the Bel fort weighing gage, 824 g will equal 1 inch
of displacement according to the chart drive. It is recommended that
for the 0- to 6-inch range, a mid-scale reading of 3 inches be used.
(3 inches of water will be approximately 2,472 g).
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a. Place several calibration weights, which are equal to 2,472 g,
in the center of the bucket platform.
b. Loosen the set screw which fastens the lever to the Pen Arm
shaft and rotate the Pen Arm shaft to put the recording pen in
the center of the chart; retighten the set screw.
c. Remove the calibration weights from the bucket, and set the pen
to the zero-line of the chart. Rotate the thumbscrews clockwise
to lower the pen and counterclockwise to raise it.
d. Place the calibration weights on the bucket to determine
whether or not the pen position is within accuracy tolerance
(0.333 percent of fullscale or 0.02 inch of precipitation). If
the pen position is not within accuracy tolerance, perform steps
(a) through (d) again, then recheck accuracy tolerance. Call the
manufacturer if the accuracy tolerance cannot be attained.
e. Remove weights from the bucket, and set up equipment for normal.
operation.
2. At 6-month intervals after the inital setup (unless the test
described above shows that it is necessary to do so sooner), cali-
brate and adjust the weighing rain gage at each 1-inch level accord-
ing to instructions provided by the manufacturer.
In the winter, approximately 2 inches of an antifreeze and oil mixture
must be added to the weighing gage bucket to capture and melt the
snow. Thus, a prolonged storm can bring the gage to the 5- to
7-inch level. If a problem occurs with the calibration in this
range, it is recommended that the bucket be emptied whenever the
5-inch range is approached and that new antifreeze and oil be added.
Linearity Test
Calibration
Level, in. weight in bucket, g
1 824
2 1,648
3 2,472
4 3,296
5 4,120
6 4,944
Quality Control Check
The QC check is performed exactly like calibration except that
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sandbag weights prepared by the Las Vegas laboratory are substituted
for the standard weights. Two weights are supplied, corresponding
to 1- and 5-inch precipitation. Place the smaller weight in the
catch bucket first; record the value on the chart after stabilization.
Add the larger weight without removing the smaller; record the value
corresponding to 6-inch precipitation. If either value is not with-
in ±0.05 inch, perform a full calibration and then recheck the QC
check weights. This QC check is performed every time that the
antifreeze-oil mixture is changed or, at a minimum, every 2 weeks.
Maintenance
Routine checks must be performed at daily, weekly, or monthly inter-
vals, as appropriate, to ensure proper operation.
1. Whenever the antifreeze-oil mixture is replaced, adjust the zero
setting with the fine-adjustment screw if necessary. The zero
setting will fluctuate slightly with temperature but generally
not more than 0.75 mm or 0.03 inch.
2. When the rain gage pail is removed, be sure that it is replaced
correctly so that it is level.
3. Weekly, wind the clock on the weighing gage and correct the
time setting if necessary. (Record any changes in the station
logbook.) Be sure to correct for backlash and to set the time
correctly with respect to a.m. and p.m.
4. Daily, inspect the ink level and check that the pen is writing
on the chart paper. If it is not, clean the pen, refill the pen
reservoir; and, using a flat toothpick, make the ink from the
pen reservoir form a small pool at the point of contact between
the pen and the chart.
5. Weekly, remove the old chart paper by removing the chart cyl-
inder thumbnut and by lifting the chart cylinder from its spindle.
Release the chart clip that holds the paper. Install the new
chart and chart clip. Replace the cylinder in its original
position on the starting point of the new week; and replace the
cylinder thumbnut. The winding mechanism for the clock is
exposed when the chart cylinder is removed. Make sure that the
cylinder gears mesh. Close the access door.
6. At weekly intervals, measure the gage level to ensure that it is
still horizontal. The check can be performed by placing a
machinist's level across the mechanism base that supports the
bucket.
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Winter Operation
Blowing snow causes the biggest problem in the winter operation of
the rain gage. Besides the inaccurate measurement of precipitation
caused by wind scour out of the gage, the dash pot may be damaged
if snow enters the weighing mechanism. Both problems may be pre-
vented by the following procedure:
Remove the funnel that is fixed to the bottom of the collector by
rotating the funnel until it clears the pins in the collector tube.
Empty the catch bucket, replace it in the gage, and add to it an
antifreeze solution composed of 2 pints of ethylene glycol and 3
pints of methyl alcohol. Add 6 ounces of motor oil to the solution
to reduce evaporation. Replace mixture whenever the gage indicates
more than 9 inches of precipitation (5 inches if calibration in mid-
range is poor). Empty the mixture into an approved disposal can.
Do not make any zeroing adjustment to the gage after adding the
antifreeze and oil mixture to the bucket. The gage will indicate a
precipitation level of approximately 2 2/3 inch. Approximate freezing
temperatures of the antifreeze solution, when diluted by additional
water content to the gage levels indicated, are as follows:
Gage level, inch Temperature, (°C)
6 -40
7 -30
8 -23
10 -13
12 -4
4.2.3 Bulk Samplers
There are no calibration procedures or quality control checks for this
instrument. Maintenance consists of weekly replacement of the collec-
tion bag. Each bag must be rinsed three times with deionized water prior
to installation. Two bags are used in each sampler, one inside the
other. Approximately one meter below the top, the bags are constricted
and wrapped with strapping tape to form a funnel approximately 23 cm
diameter.
4.2.4 Science Associates Meteorological Sensors
The meteorological sensors are located on a pole approximately 2 meters
above the platform. A stepladder or step-box is provided to access the
sensors.
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1/Jind Speed Calibration
The wind speed transmitter is calibrated monthly by using a synchronous
motor and by adjusting the output of the generator. The following three
revolutions per minute (RPM) speeds have been selected to determine
linearity of the wind speed transmitter:
RPM MPH Knots Volts (DAS)
300 32.4 ± 1 28.1 ± 1 1.50
600 62.4 ± 1 54.2 ± 1 2.90
900 92.5 ± 1 80.3 ± 1 4.28
Remove the transmitter from the supporting structure. Remove the cap nut
and cup-wheel assembly from the wind speed transmitter. Attach the
synchronous motor to the shaft and apply power to the synchronous motor.
This motor will rotate at a speed of 300 RPM, which corresponds to an
output voltage of 1.50 V. Repeat for remaining RPM points. If the
output of the wind speed transmitter is not within ±0.05 V for any
point, adjust the generator. To do so, loosen the two binder head
screws that overlap the metal brush mounting ring. Turn the ring to
change the output voltage of the transmitter. Adjust the brush ring
until proper indication is obtained, and secure the ring in this posi-
tion by tightening the binder screws. Recheck calibration after secur-
ing the ring; in tightening the screws, the ring may have rotated
slightly. If the transmitter will not calibrate, check the terminal
resistance and swamping resistance before proceeding further. Using an
ohm meter, check the terminal resistance which should read 40 ohms. The
swamping resistor should have a value of 8 ohms. If the terminal resis-
tance is not correct, replace the brushes according to the procedures
given in the instruction manual.
Wind Direction Calibration
Calibrate the wind direction transmitter by using a circular plexiglass
template with at least eight marks or lines at 45° spacing to indicate
the eight cardinal compass directions.
Remove the wind direction transmitter from the supporting structure, and
place it on the calibration stand. Secure it to the stand by tightening
the locking screws on the transmitter body. Connect a voltmeter to the
output of the power and distribution assembly or to the signal condition-
ing circuit. Rotate the vane until a north reading is observed on the
voltmeter, and rotate the calibration template until the north mark is
also aligned with the vane position. Secure the template against changing
position. Position the vane at each of the 45° marks, and record the
readings from the voltmeter. Accuracy within 3° is acceptable.
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After calibration has been completed for both transmitters, install them
on the 1 1/4-inch pipe on the supporting structure. Place the vane
directly over the scribed line on the side of the case. This line cor-
responds to north. Rotate the wiper-arm assembly so that the resistance
between terminal and wiper arm is at minimum resistance. Use the low-
range scale on the ohm meter. Fasten the wiper-arm assembly in that
position securely. Check alignment with a compass or landmark, and
secure case to pole.
Quality Control Check
There are no QC check procedures.
Maintenance
Routine maintenance of the wind speed and wind direction transmitters
consists of checking calibration, lubricating moving parts, and replac-
ing defective or worn parts at regular intervals. Calibration of the
wind speed transmitter is checked at monthly intervals, and the bearings
are cleaned and lubricated at 6-month intervals.
Calibration of the wind direction transmitter is checked at monthly
intervals, and the commutator torroid resistor unit and contact brushes
are checked at 6-month intervals.
Replacement of defective or worn parts is performed as necessary,
according to the instructions provided by the manufacturer.
Winter Operation
Snow buildup or freezing of the transmitters can cause inaccurate
information to be recorded. To reduce or prevent snow accumulation on
the wind speed and wind direction transmitters, lightly coat the units
with a Teflon spray. It is recommended that this procedure be performed
indoors or be performed outdoors when the air is calm, provided that
the outside temperature is within the specified limits of the Teflon
spray.
4.2.5 Data Acquisition System
Calibration
A constant voltage source is used to ensure proper recording of inputs;
the recording process is checked as part of the initial acceptance
tests, during installation and at 6-month intervals thereafter. On
site, the constant voltage source is connected to the cable end on the
monitoring platform to check the cable and the DAS.
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Quality Control Check
There is no specific QC check for the DAS. Instead, the DAS-recorded
values of meteorological sensor calibrations are compared to recorded
voltmeter or ohm-meter readings. Clock accuracy is verified weekly
against standard time.
Maintenance
Routine maintenance includes replacement of printer paper and periodic
hard disk downloading. See Appendix A or the instructions provided by
the manufacturer for specific procedures.
Winter Operation
Because the DAS is housed in a temperature-controlled shelter, specific
procedures for winter operation are not necessary.
4.3 TROUBLESHOOTING
Copies of manufacturer manuals are maintained on site to provide trouble-
shooting guidance. Further troubleshooting aid is provided by Lockheed-
EMSCO engineers who may be called through the project supervisor at
1-800-322-8844 or (702) 734-3227. Spare parts and test equipment are
provided on site.
All malfunctions from initial symptoms through final resolution are
tracked in the site operator's logbook. Analysis of malfunctions is
included in the assessment of instrument operational reliability.
4.4 SAMPLE COLLECTION, HANDLING, AND SHIPMENT
Sample collection, handling, and shipment procedures are structured to
ensure that contamination and sample loss are minimized.
The following discussion is limited to the physical samples shipped to
Las Vegas for processing and analysis. Included are snow cores and sam-
ples from the wet/dry collectors and bulk samplers. The documentation
included with each shipment, including Bel fort rain gage charts, DAS
outputs, site operator's logbook entries, and field forms, are discussed
in greater detail in Section 4.6.
Samples are collected in accordance with the sampling schedule unless
heavy precipitation necessitates more frequent replacement of collection
vessels. Specific guidelines are as follows:
1. Change bucket or bag if it is observed to be more than 3/4 full during
daily checks and if snow or winds are forecast.
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2. Change bucket or bag if it is more than 1/2 full and if forecasts
predict heavy snowfall (more than 6 inches) in the next 24 hours.
In all cases when multiple buckets or bags represent a single sample
interval, identify each container chronologically (i.e., indicate date
removed, and indicate that the vessel is 1 of x, 2 of x, x of x).
Change the sampling bucket in the wet/dry collector as follows:
1. Approach the collector from and work from the downwind side (if
possible) to minimize windblown contaminants from entering the
buckets. Open one of the shipping containers, and, wearing gloves,
remove the new lid from the plastic bag. Do not touch surfaces that
will come in contact with the precipitation sample. Place the lid on
the bucket to be removed. With masking tape or a similar tape,
temporarily fasten the lid on the bucket. With a permanent marker,
record sample identification information on the bucket lid, and mark
snow depth on the outside of the bucket. Remove the bucket with the
lid from the collector, and secure the lid by snapping in place or by
striking the edges with a rubber mallet. Place the bucket in the
plastic bag and then in the shipping container. Secure the bucket so
that it will not tip over and leak.
Perform weekly instrument maintenance tasks after removing the bucket
and prior to installing a new bucket.
2. Place the new bucket on the collector after removing the plastic bag
in which it was shipped. Buckets are not to be removed from plastic
bags until they have been taken to the sampling site and are ready to
be placed on the collector. This procedure helps avoid dust and other
contamination of the bucket before it is installed. Note times of
bucket removal and placement.
NOTE: If possible, change buckets only when no precipitation is
occurring.
Change the bag in the bulk sampler as follows:
1. Wearing lab gloves and working from the downwind side, lift bags
by edges protruding from the hose clamp which secures the bags to
the rim. Remove the bags and twist the top closed; secure the bag
with twist tie or a cable tie. Mark the snow depth with a per-
manent marker. Place the bags inside a plastic garbage bag, and
close the garbage bag with twist tie. Attach the sample identi-
fication label. Replace the bags with clean, washed double-bags
without touching any part of the inside surface except the top
edge. Note times of removal and replacement.
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2. If the volume is too large to place into a shipping container,
measure and record the fill height, then carefully transfer the
contents to sample buckets. Perform the transfer in an area out
of the wind, such as the unheated barn. Record the sample identi-
fication information on the bucket lids with a permanent marker.
Samples are shipped once each week. Until that day, collected
samples are stored in an unheated or refrigerated area. On the
shipping date, place four to eight frozen gel packs around
samples, enclose related documentation in a Ziploc bag, and tape
the tab to the shipping container lid. Seal the shipping con-
tainer. Label each container, and ship by designated carrier
(UPS). Retain a copy of the bill of lading provided by the carrier
or a copy of a similar document. By telephone, notify the project
supervisor of the shipment; provide the project supervisor with the
sample identifications, the number of containers, and the identifi-
cation number provided by the carrier.
4.5 DAILY OPERATOR ACTIVITIES
The following section details the checks, observations, and tasks to be
performed each day of operation. Calibrations, maintenance, QC checks,
and sample collection activities all are dictated by schedules. Therefore,
the first task to be performed each day is to check these schedules to
determine the specific tasks to be performed on that day. Note the task
to be performed, and refer to the relevant section of this manual for the
specific procedures. In addition, the following tasks are to be performed
each day:
1. Obtain a weather forecast for the next 24 hours. It may be necessary to
change sample collection vessels and to empty the Bel fort rain gage
catch bucket if heavy snowfall is predicted. If an event is in
progress but is scheduled to end within the next 2 hours, delay sample
collection (if possible) until event conclusion.
2. Check the most recent outputs of the DAS (see Appendix A for pro-
cedure). Note the indicated wind speed and wind direction and the
wet/dry collector open/closed position. Upon ascending the platform,
verify that actual instrument status corresponds to recorded data.
3. Inspect each instrument. Check fill levels of wet/dry collectors,
bulk samplers, and Belfort rain gages; change collection vessels and
empty rain gage catch bucket if needed. Check for joint freezing;
lubricate as needed.
NOTE: Before applying spray lubricant, cover all collection
vessels.
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1 4. Check Bel fort rain gage chart trace. Re-ink pens if chart trace
is light.
5. Photograph the area in each of the four directions, beginning on the
north side and proceeding clockwise.
6. Clear the accumulated snow from the monitoring platform and steps.
NOTE: Cover all collection vessels.
Before descending from the platform, make a last check of each instrument
to ensure that covers are removed, wet/dry collectors are in the correct
open/closed position, and meteorological sensors are positioned and are
responding properly.
4.6 DOCUMENTATION
Field documentation includes the site operator logbook, Bel fort rain gages
charts, DAS outputs, photographs, and a field data form.
4.6.1 Site Operator's Logbook
The site operator's logbook is the permanent history of all field
activities. Each day the operator records the following information:
date, time of site checks, names of personnel on site, all tasks per-
formed, calibration values, results of QC checks, weather observations,
problems and resolutions, samples collected, and personal observations.
The logbook is doublepaged and numbered. Duplicate (carbon copy) pages
are submitted with each weekly shipment; the original bound pages are
maintained on site.
4.6.2 Bel fort Rain Gage Charts
Chart changing procedures are described in Section 4.2.2. Annotation
on the chart includes rain gage identification, dates and times of
installation and removal, dates and times of calibrations, QC checks,
and antifreeze-oil mixture replacement. Charts are submitted weekly
with the sample shipment. Copies may be retained on site if duplicating
services are available.
4.6.3 Data Acquisition System
DAS outputs include floppy disks, graphics, and hardcopy outputs from
the printer. Hardcopy outputs are submitted weekly with the sample
shipment and are annotated with the following information: time period
covered, dates and times of wet/dry collector and meteorological sensor
calibration, QC checks, maintenance, dates and times of sample collection,
and notation of malfunctions. Floppy disks of DAS outputs are created
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x monthly during site visits by a Lockheed-EMSCO scientist. They are
hand-carried back to Las Vegas. Copies of each disk are kept on site.
All graphics are produced in duplicate; one set accompanies sample
shipments, and the other set is kept on-site. These graphics are used
for data analysis purposes and are annotated with the site operator's
interpretation of the data.
4.6.4 Photographs
Photographs are taken daily to document site conditions. The site
operator records the date, time, direction, and number of frames taken
in the site operator logbook. The first and last frames are pictures of
a chalkboard or other surface annotated with date and time. Exposed
film rolls are kept on site until they are hand-carried to Las Vegas
after a visit by a Lockheed-EMSCO scientist. Processed slides are
identified by date, time, and direction and are filed in protective
sheets.
4.6.5 Field Data Form
The field data form (Figure 3-1) is described in Section 3.2.4. The
site operator records requested information daily. On the date of
sample shipment, the final information is recorded, and the site oper-
ator reviews the form for completeness, legibility, and accuracy. The
last copy is removed and filed on site; the original and first copy are
included in the sample shipment.
4.7 SNOW CORING, SNOW PIT DENSITY MEASUREMENTS, AND SNOWBOARDS
In addition to the use made of the instruments located on the monitoring
platform, measurements are made manually at ground level. The site operator
receives 2 weeks of training in performance of these measurements. Training
is conducted by a Lockheed-EMSCO scientist familiar with these techniques.
Particular attention is given to performance of these methods during
monthly site visits.
4.7.1 Snow Coring
Snow coring is performed weekly, except during the intensive sampling
period when samples are taken daily as well as weekly. The purpose in
snow coring is to establish on a weekly or daily basis a "ground truth"
value for the mean chemical composition of snow after deposition occurs.
Snowboards are the standard for quantitative comparison of snow accumu-
lation in both hydrological and glaciological studies. This study
incorporates the snowboard as the base for vertical cores to ensure that
they are representative of the same sampling interval as collected by
the platform-mounted instruments.
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The snowboard base limits the migration of chemical species vertically
through the pack, except in situations of fairly high liquid water
content flowing through the snow (greater than 5 percent liquid water).
The base of the board also serves as a very effective event marker or
time stratigraphic marker.
During weekly sampling periods for the Aerochem Metrics samplers, vertical
snow coring also is performed weekly. The field sampler takes two
vertical cores to the base of a snowboard on the day that the NTN sample
buckets are sealed. The "pusher" is used to extrude the core from the
core barrel into the standard sample buckets. The pusher can be used to
tamp the sample into the buckets in order to maximize the amount of
snow core shipped in one bucket. The snow core depth is recorded in the
field notebook for each core. This measurement can be calculated later
to a snow density that is determined from the diameter of the corer
and from the sample weight recorded by the processing laboratory. It is
important that duplicate cores be taken to establish an estimate of the
spatial variability of the ground truth data. These two cores should be
taken as close together temporally as logistical constraints allow.
Usually, one core should be taken directly after the other, unless the
first sample freezes solid in the core barrel. In that case, the cores
must be brought inside, and the snow sample must be melted into the
bucket. This should be noted in the field book and the sample logbook,
because melting and subsequent refreezing of samples may precipitate out
materials that will be filtered out of the sample during processing in
Las Vegas.
The procedure is altered slightly during daily event sampling of the NTN
monitors. Each day, one vertical core is taken to the snowboard base, is
extruded into a sample bucket, and is shipped as above. Once each week
(to split up tasks, the day before sample shipping) a second daily
vertical core sample is taken in order to estimate the natural variability
associated with daily "ground truth" samples. During the 30-day daily
sampling period on the day of sample shipping, two weekly cores are
taken in addition to the core taken daily. This procedure should ensure
comparability of weekly event chemistry in the unlikely situation that
chemical processes affect samples left on snowboards for a week dif-
ferently than they affect samples left on the boards for a day.
4.7.2 Snow Pit Density
Density measurements compose the primary "ground truth" to determine
incoming precipitation water-equivalent volumes. In order to quantify
the natural variability between measurements, two complete sets of snow
pit density measurements are made from the snow surface to the pit
bottom each week. It should be recognized that stratigraphic layers may
not always lie flat, but may slope. For these situations, a comparsion
of densities of layers at equal depths from the snow surface (or height
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above the ground surface) will be in error. Only stratigraphically
similar snow samples should be compared for density.
The north- or northwest-facing snow pit walls should be scraped with a
shovel from the snow surface to the ground to form a nearly perpendicular
surface. Then a snow shovel or snow knife is used to trim the walls
visibly smooth. The Hydro-Tech Taylor-LaChapelle snow density kit is
opened on the floor of the pit or, if snow depth necessitates, on a
shelf cut into a side wall. First, place the three thermometers into
the snow at about equal intervals. Insert the stem of the thermometer
perpendicular to the pit wall until the dial is flush with the pit wall.
Allow 5 minutes for the thermometers to come to equilibrium before
recording temperatures in the field book. Make certain to record the
label identification for each thermometer and the height above the
ground. Use the folding ruler supplied with the kit to make the measure-
ment. This procedure ensures that temperature calibration errors are
not randomly superposed on the data. Temperature is measured to obtain
a rapid, indirect indication of liquid water in the pack. The presence
of liquid water is inferred from 0°C temperatures. At temperatures
below 0°C, liquid water is assumed to be below 1 percent by volume,
which is below the limit of detection by standard field techniques.
Remove the larger of the two "cookie cutters" from the density kit, and
insert it into the snow pack until a full sample is taken. Visually
confirm that the sample is full, then empty the sample into the weighing
pan on the upper surface of the analytical balance. Weigh the sample,
and record the weight in the field book. Use the volume of the "cookie
cutter" to compute sample weight to density.
The hand lens estimate of snow grain shape and metamorphic changes is
used to evaluate intervals throughout the snow pack (LaChapelle, 1969).
As with the distribution of thermometers, the purpose of the interval
evaluation is to acquire qualitative data (in this case on snow grain
shapes) that can be correlated with vertical coring chemistry data
collected throughout the study. These correlations provide preliminary
information on changes in pollutant distribution on snow grains during
diagenetic changes in the snow pack.
It is especially important to note in the field logbook the presence
and potential variability of water within the pack. The presence of
water is a potential source of variability which will not be obvious
during subsequent interpretation of the data and field notes. Only air
temperature, snow temperature, and the field observer's comments will
help identify that water was present in the sample.
4.7.3 Snowboard Precipitation Amount Sampling
Two snowboards with 1.30 meter center posts ruled in centimeters are
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used to collect daily samples during intensive sampling and to collect
weekly samples throughout the monitoring study. When there is no measur-
able precipitation in progress, a measurement of accumulation is entered
into the field logbook. The boards are painted white with satin-finish
polyurethane. This treatment minimizes melt absorption by the wood and
prevents heat absorption from affecting thin layers of snow significantly.
Four snowboards are needed to quantify independently the variation in
"ground truth" accumulation in the study plot. Lockheed-EMSCO will
provide two snowboards for use in the area surrounding the sampling
platform and two for the snow study clearing, 60 meters further south.
Because snow accumulation rates are not always the same for different
clearings, separate accumulation "ground truth" measurements are needed
for the platform clearing and the snow pit clearing.
During the measurement period, the following items should be entered in
the field logbook for each set of measurements:
1. Observer's general impression of the wind speed during the previous
24 hours:
a. high (greater than 30 MPH)
b. medium (10 to 30 MPH)
c. low (less than 10 MPH)
2. Tendency for redeposition or scouring (check for YES, blank for no):
Saltation of snow grains along snow surface
Blowing snow moving in suspension 10 cm above the snow surface
Blowing snow moving in suspension 50 cm above the snow surface
Blowing plumes of snow observed going onto or over the
sampling deck of the platform
Presence of dunes or ridges on snow surface
Evidence of wind erosion on snowboard sample surface
If yes, specify which snowboard.
3. Platform Clearing - snow accumulation:
Depth of snow on board A, (cm)
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* which are ruled in centimeters are used to collect daily measurements
Depth of snow on board B, (cm)
Presence of ice layers in snow on boards
Snowmelt refrozen
Rain refrozen
Ice layer in sample, origin not obvious
4. Snow pit clearing - snow accumulation:
Depth of snow on board C, (cm)
Depth of snow on board D, (cm)
Presence of ice layers in snow on boards
Snow melt refrozen
Rain refrozen
Ice layer in sample, origin not obvious
5. Date of observation:
6. Time of observation:
7. Weather conditions in relation to ability to complete field
observations:
(1-10; 1 = excellent conditions
5 = average conditions
10 = normal protocols not possible)
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5.0 ANALYTICAL OPERATIONS
All analytical activities are performed by Lockheed-EMSCO in facilities
provided by EPA EMSL-LV. Processing operations, including water equiv-
alent determination, aliquot preparation, specific conductance and pH
measurements, and field operations support, are conducted in laboratory
facilities at 4675 Valley View, Las Vegas, Nevada, under the direction of
D. J. Chaloud, Laboratory Operations Supervisor. Analyses of chloride,
ammonium, nitrate, sulfate, and cations are performed on instrumentation
located at 944 East Harmon, Las Vegas, Nevada, under the direction of
D. C. Hillman, Methods Development Supervisor. Weekly processing activ-
ities are initiated immediately upon receipt of samples and are concluded
within 48 hours of receipt of frozen samples. Every two weeks, the ali-
quots that have been prepared and accumulated for chloride and ammonium
determinators are analyzed; every four weeks the accumulated aliquots for
cations (Na, K, Ca, and Mg) and nitrate and sulfate determinations are
analyzed. The accumulated aliquots that are analyzed at one time are
considered a unique batch.
5.1 PROCESSING ACTIVITIES
Samples are received weekly via UPS. Initial measurements are taken, then
samples are permitted to melt. Conductivity and pH measurements and ali-
quot preparation are performed upon completion of melting. Clean sample
buckets and field supplies are shipped to the field station via UPS weekly
or as needed.
5.1.1 Sample Handling
1) Sample Receipt
The UPS shipping form is checked to verify receipt of all samples.
Each sample is then checked against the field data form to verify
complete identification of each sample. A log is maintained showing
sample identification, bucket ID, and relevant comments such as
incomplete lid seal, leakage, or partial melting. Measurements
(weight and volume) for determination of water equivalent are taken.
Samples are then placed on snowmelt racks and are left undisturbed
until the next morning. Bucket blanks are prepared and placed on
the snowmelt racks with samples.
2) Batch Organization
Buckets are shaken to determine if the snow has melted. When melt-
ing is complete, bucket lids are removed by using a specially designed
metal tool which does not contact any internal surfaces. Sample ID
numbers are randomly assigned and comments (e.g., low volume, debris)
are noted.
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Audits and blanks are incorporated according to the schedule
supplied by QA personnel. Audits and blanks are described in
Section 3.1. Blanks and audits are assigned sample ID numbers
randomly. A Batch/QC Field Data Form is initiated which makes
use of sample codes below:
R = routine
B = field blank
BB = bucket blank
Audits F L I - XXX
ID number (sequential)
concentration lot number
concentration level
S = synthetic
L = low NBS
H = high NBS
audit type
L = lab
F = field
3) Sample Preparation
The bucket is transferred to the clean-air station where an analyst,
wearing a lab coat and gloves, prepares the sample for analyses by
following these steps in the order given:
a) pH and specific conductance. Obtain four 50-mL centrifuge tubes
(not acid-washed [NAW]) which have been soaked in deionized
water for 24 hours. Swirl the contents of the bucket and mix.
Rinse the tubes three times with sample (if the sample volume is
low, rinse twice with deionized water and a third time with
sample).
Swirl the bucket, and pour 25 ml of the sample into each tube.
Cap the tubes, and label two of the tubes with an "R." The
contents of these tubes are to be used as a rinse for each
method.
b) Filtration and Preservation. Rinse a Cubitainer or a 500-mL NAW
aliquot bottle three times with sample (rinse twice with deion-
ized water and once with sample if the sample volume is low).
The remaining sample volume is transferred to the Cubitainer by
using a funnel which has been soaked in deionized water for 24
hours.
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4) Sample Storage and Transfer
Prepared aliquots are kept refrigerated at 4°C until they are
received by analytical personnel. On the date of transfer, a
shipping form is completed and is signed by the analyst receiving
the aliquots.
5.1.2 Water Equivalent Determination
1) Balance Standardization
Check standardization prior to each use of the balance. Select
weights encompassing the range for which the balance is used. Wear
gloves. Do not touch the weights with anything but forceps (or a
gloved hand for weights over 1 kg). Tare balance, and record read-
ing for each weight in the logbook. If weight values and balance
readings do not agree, consult the guide provided by the manufac-
turer for adjustments.
2) Weight and Volume
Record weight of clean, empty bucket prior to shipment to field.
Upon return from field, record weight of sealed bucket. Subtract
the bucket tare weight and the average lid weight; record net sample
weight.
With the sealed bucket on a level surface, measure height to the
fill level marked by the site operator (see Section 4.4), and record
that height (centimeters). Determine volume (cm^) by:
volume = IT
height
Record volume.
3) Snow Density and Water Equivalent Calculation
Calculate snow density (SO) by:
SD =
net sample weight, g
sample volume, cm^
Snow density is used as a cross-check of snow pit density measure-
ments (see Section 4.7) computed on-site.
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Calculate water equivalent (we) by:
net sample weight, g
we =
density of water, g/cnv* x surface area*, cm^
*of bucket base, bulk sampler funnel, or core barrel.
For these calculations, the density of water is assumed to be
1.00 g/cnP. Record both snow density and water equivalency values
in the logbook.
5.1.3 Specific Conductance
1) Summary of Method
The specific conductance in samples is measured with a conductance
meter and conductivity cell. The meter and cell are calibrated
with potassium chloride standards of known specific conductance
(U.S. EPA, 1983).
Samples are preferably analyzed at 25°C. If they cannot be analyzed
at 25°C, temperature corrections are made, and results are reported
at 25°C. A water bath may be used to maintain constant temperature.
2) Interferences
Temperature variations represent the major source of potential error
in specific conductance determinations. To minimize this error,
calibration standards and samples must be measured at the same tem-
perature.
The samples may contain substances (suspended solids, etc.) which
may build up on the conductivity cell. Such a buildup interferes
with the operation of the cell and must be removed periodically by
following the recommendations provided by the cell manufacturer.
3) Apparatus and Equipment
0 Specific Conductance Meter—Digital meter with the following
minimum specifications:
Range--0.1 to 1,000 yS/cm
Readability--0.1 yS/cm
Maximum error—1 percent of reading
Maximum imprecision—1 percent of reading
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0 Conductivity Cell--High quality glass cell with a cell constant
of 1.0 cm'l or 0.1 cm~m. Cells containing platinized electrodes
are recommended.
0 Thermometer--NBS-traceable thermometer with a range of 0 to 40°C
and divisions of 0.1°C.
0 Water bath (Optional) with heating/cooling apparatus capable of
maintaining constant temperature of 25°C ± 0.1°C.
4) Reagents and Consumable Materials
0 Potassium Chloride Stock Calibration Solution (0.01000M KC1)--
Dissolve 0.7456 g potassium chloride (KC1 , ultrapure, freshly
dried for two hours at 105°C and stored in a desiccator) in
water, and dilute the solution to 1.000 L. Store the final
solution in a tightly sealed container.
NOTE: Prepare two stocks. Label one as Calibration Stock, the
other as QCCS stock.
0 Potassium Chloride Calibration Solution (0.001000M KC1)--Dilute
10.00 ml KC1 stock calibration solution to 100.00 ml with water.
This solution has a theoretical specific conductance of 147.0
uS/cm at 25°C.
0 Potassium Chloride QC Solution (0.000500M KC1)--Dilute 5.00 ml
0.0100M KC1 solution (independent of the KC1 stock calibration
solution) to 100.00 ml with water. This solution has a theoret-
ical specific conductance of 73.9 yS/cm at 25°C.
0 Water—Water must meet the specifications for Type I Reagent
Water given in ASTM D 1193 (ASTM, 1984).
0 Glassware - Class A volumetric.
5) Calibration and Standardization
Step I—Measure and record the specific conductance of the KC1
calibration solution.
Step 2--Calculate the corrected cell constant, Kc, with the
following equation:
147.0 uS/cm
KClm
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where: KClm = measured specific conductance for the KC1
calibration solution.
The corrected cell constant, Kc, includes the calculation for the
cell constant and for the temperature correction to 25°C.
NOTE: See SOP (Appendix B) for quality control checks.
6) Procedure
Step I—Follow the instructions for the operation of the meter and
cell which are provided by the manufacturer.
Step 2—Allow the samples and calibration standard to equilibrate to
room temperature.
Step 3—Measure the sample temperature. If different from the
standard temperature, allow more time for equilibration.
Step 4--Rinse the cell thoroughly with water.
Step 5--Rinse the cell with a portion of the sample to be measured.
Immerse the electrode in a fresh portion of sample, and measure its
specific conductance.
Step 6—Rinse the cell thoroughly with water after use. Store the
cell in water.
If the readings become erratic, the cell may be dirty or may need
replatinizing. Consult the operating manual provided by the manu-
facturer for guidance.
7) Calculations
Calculate the corrected specific conductance (Sc) for each sample
with the following equation:
Sc = (KC) (Sm)
where: Kc = corrected cell constant
Sm = measured specific conductance
Report the results as specific conductance: pS/cm at 25°C if using
a constant temperature water bath. If analysis is not at 25°C,
report pS/cm at temperature of analysis.
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8) Precision and Accuracy
Forty-one analysts in 17 laboratories analyzed 6 synthetic samples
containing increments of inorganic salts, with the following
results (U.S. EPA, 1983):
Increment, as Precision, as Accuracy, as
Specific Conductance Standard Deviations
(yS/cm) (yS/cm) Bias (%) Bias (yS/cm)
100 7.55 -2.02 -2.0
106 8.14 -0.76 -0.8
808 66.1 -3.63 -29.3
848 79.6 -4.54 -38.5
1,640 106 -5.36 -87.9
1,710 119 -5.08 -86.9
In a single laboratory (EMSL-Cincinnati) analyzing surface-water
samples with an average conductivity of 536 yS/cm at 25°C, the
standard deviation was 6 yS/cm (U.S. EPA, 1983).
5.1.4 £H
NOTE 1: Because of the length of the detailed SOP for the determination
of pH, only an overview of the method is presented here. The
SOP is included in this document as Appendix C.
NOTE 2: This SOP is written specifically for the Orion Model 611 pH
meter and Orion Ross combination pH electrode and is based on
instructions provided by the manufacturer (Orion, 1983).
1) Summary of Method
The pH of samples is measured with a pH meter and electrode. The
meter and electrode are calibrated with commercially available, NBS-
traceable buffers.
2) Interferences
No interferences are known.
3) Apparatus and Equipment
0 Orion Model 611 pH meter.
0 Orion Ross combination pH electrode.
0 50-mL plastic centrifuge tubes.
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4) Reagents and Consumable Materials
0 pH Calibration Buffers (pH 4.00 and 7.00)--Commercially available
NBS-traceable.
0 Potassium Chloride (3 M)--Dissolve 70 g KC1 in 1 L of DI water.
0 Water—Water used in all preparations must conform to ASTM
specifications for Type I water (ASTM, 1984). It is obtained
from the Millipore water system.
5) Calibration and Standardization
Weekly, calibrate the temperature function of the pH meter and
electrode by using a two-point calibration (4°C and room temper-
ature) and by following the instructions provided by the
manufacturer.
Daily, calibrate the pH function of the pH meter and electrode by
using a two-point calibration (pH 7 and 4) and by following the
instructions provided by the manufacturer. Generally, the calibra-
tion involves setting the meter calibration control while measuring
pH 7 buffer and setting the slope control while measuring pH 4
buffer. After calibration, the calibration accuracy is checked
according to the following procedure:
Step I—Copiously rinse the electrode with water. Immerse the elec-
trode in 20 ml pH 7 buffer, and stir it for 30 to 60 seconds.
Discard the original buffer and replace it with an additional 40 ml
pH 7 buffer. While gently stirring the solution, measure and record
the pH.
Step 2--Repeat step 1 with the pH 4 buffer.
Step a—Compare the pH values obtained for the pH 7 and 4 buffers
in steps 1 and 2 to the certified values of the buffers. If either
observed value differs from the certified value by more than ±0.02
pH units, repeat the electrode calibration. If acceptable results
cannot be obtained, replace the electrode.
NOTE: See SOP (Appendix C) for quality control checks.
6) Procedure
Step 1—Calibrate the pH meter and electrode.
Step 2—Equilibrate samples to room temperature.
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Step 3--Perform the required QC analysis. Proceed with sample
analyses if acceptable results are obtained.
Step 4--Immerse the pH electrode in the 50-mL centrifuge tube
designated as the rinse for 5 to 10 seconds. Measure pH in the
second tube, allowing the pH to stabilize over a 2-minute interval.
The pH is stable when the value does not change more than 0.02 pH
units in one direction over a 2-minute interval.
Step 5--Rinse the electrode copiously with water between samples.
Step 6--At the end of the day, store the electrode in 3 M KC1.
7) Calculations
No calculations are required.
Record pH and temperature values in the logbook.
5.1.5 Aliquot Preparation
NOTE: Because of the length of the detailed SOP for filtration and
preservation, only an overview of the method is presented here.
The SOP is included in this document as Appendix D.
1) Summary of Method
Samples are filtered to remove the biotic and abiotic particles
which exceed 0.45 urn in size. This procedure is necessary to
prevent changes in particular chemical parameters prior to analysis.
The preparation of the sample and the preservation used depends on
the parameter being measured; the sample-preservative design ensures
sample stability until analysis is complete. Aliquots are prepared
within approximately 12 hours following completion of snow melting.
Aliquots are prepared as follows:
Aliquot Chemical Parameter Container Preservative
1 Na, K, Ca, Mg 125 ml AW* HN03 to pH < 2
2 N03, S04 125 ml NAW* HgCl2
3 Cl 125 ml NAW* none
4 NH4 125 mL AW* H2S04 to pH < 2
*Smaller bottles or reduced volume or both may be substituted for
low volume samples (AW = acid-washed, NAW = not acid-washed).
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2) Apparatus and Equipment
Filtration Apparatus—Includes filter holder, vacuum chamber, and
vacuum pumps.
Pi pets—Calibrated over range 40 to 200 uL(2) and 1 to 5 mL(l).
3) Reagents and Consumable Materials
0 Nitric Acid (HN03, 12 M, Baker Ultrex grade or equivalent).
0 Sulfuric Acid (t^SO^ 18 M, Baker Ultrex grade or equivalent).
0 Mercuric chloride (HgC^, 5 percent, reagent grade or equivalent).
0 Water—Water used in all preparations must conform to ASTM
specifications for Type I water (ASTM, 1984). It is obtained
from the Mi Hi pore Milli-Q water system.
0 Aliquot Bottles--Clean aliquot bottles are required for the
four aliquots prepared from each sample and for any split samples,
The bottles are cleaned and are supplied by an outside con-
tractor.
0 Indicating pH Paper (Range pH 1 to 3).
0 Membrane Filters (0.45-ym pore size).
4) Procedure
Preparation of the four aliquots and any split samples is described
in this section. All filtrations are performed in the laminar-
flow clean work station.
a) Preparation of Aliquots 1 and 4
Step 1—Complete aliquot labels for aliquots 1 and 4, and attach
labels to containers. Assemble the filtration apparatus with a
waste container as a collection vessel. Apply vacuum (pressure
must not exceed 12 inches Hg). Thoroughly rinse the filter
holder and membrane filter in succession with 20 to 40 ml DI
water, 20 ml 5 percent HN03 (Baker Instra-Analyzed grade), and
40 to 50 ml DI water.
Step 2—Rinse the filter holder and membrane with 10 to 15 mL
of the sample to be filtered.
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Step 3—Turn off vacuum. Replace the waste container with the
aliquot 1 container. Reapply vacuum and filter 10 to 15 ml of
sample. Remove the vacuum. Rinse the aliquot 1 container with
the 15 ml of filtered sample by slowly rotating the bottle so
that the sample touches all internal surfaces. Discard the
rinse sample, and replace the container under the filter holder.
Step 4--Filter sample into the container until the container is
full.
Step 5--Transfer filtered sample into the aliquot 4 container
(previously labeled) after first rinsing the container with 10
to 15 mL of filtered sample.
Step 6--Return the aliquot 1 container to the filtration
apparatus, and collect additional filtered sample until the
container is full.
If it is necessary to replace a membrane (because of clogging)
before adequate filtered sample has been obtained, rinse the
new membrane with 15 to 20 mL of water, 10 to 15 ml of 5 percent
HNOj, 40 to 50 ml of water, and 10 to 15 ml of sample prior to
collecting additional sample.
Step 7--Between samples, remove the membrane and thoroughly
rinse the filter holder with water.
Step 8--Preserve the sample by adding concentrated HN03 to
aliquot 1 and concentrated HpS04 to aliquot 4 in 0.100-mL
increments until the pH <2 (O.S. EPA, 1983). Check the pH by
using a clean pipet tip to place a drop of sample on indicating
pH paper.
Step 9—Store aliquots 1 and 4 at 4°C until ready to transfer.
b) Preparation of Aliquots 2 and 3
Step l--Soak filter holders for 24 hours in deionized water
prior to first use and weekly thereafter.
Step 2--Complete aliquots 2 and 3 labels, and attach labels
to the aliquot bottles. Assemble the filtration apparatus
with a waste container as a collection vessel. Thoroughly
rinse the filter holder and membrane filter with three 25-mL
portions of water followed by a final rinse with 10 to 15 ml
of the sample to be filtered.
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Step 3—Replace the waste container with the aliquot 3 con-
tainer, and filter an additional 15 ml of sample. Remove the
container, and rinse it by slowly rotating the bottle so that
the sample touches all internal surfaces. Discard the rinse
sample, and replace the container under the filter holder.
Step 4--Filter sample into the container until cubitainer is
full.
Step 5--Transfer filtered sample into the aliquot 2 container
(previously labeled) after first rinsing the container with
10 to 15 ml of filtered sample.
Step 6--Return the aliquot 3 container to the filtration appara-
tus, and collect additional filtered sample until the container
is completely full. Cap the container tightly to ensure that
all headspace is removed.
If it is necessary to replace a membrane (because of clogging),
rinse the membrane with three 20-mL portions of water followed
by a final rinse with 15 ml of sample.
Step 7--Between samples, remove the membrane and thoroughly
rinse the filter holder with water.
Step 8—Preserve aliquot 2 by adding 0.1 ml 5 percent mercuric
chloride. No preservation is required for aliquot 3.
Step 9—Store at 4°C until ready to ship.
5.1.6 Field Support
Items supplied by the laboratory to the field include clean, tared
sampling buckets and lids, DI water, and various consumable items. The
DI water is used for rinses and field blanks. Consumable items may
include such things as sterile laboratory gloves, freeze-gel packs,
spare parts, bulk sampler bags, field forms, and other items defined
on an as-needed basis.
All buckets and lids are initially leached in DI water for at least
72 hours, and three DI water rinses and a wipe down with a natural
sponge follow. Each bucket is assigned a unique ID number and is
weighed prior to each use. Prior to the first use, 20 lids will be
weighed; if the standard deviation is less than 1 g, a mean lid weight
will be used in weight calculations. Each bucket and lid is placed in a
large plastic bag and is closed with a twist tie. They are shipped to
the field in styrofoam containers along with freeze-gel packs and other
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Section 5.0
Revision 1
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Page 13 of 35
required consumable items. After each use, the cleaning procedure is
repeated for each used bucket; lids are not reused.
All shipping is by UPS.
5.2 ANALYTICAL PROCEDURES
The most economical means of providing analyses is to analyze a large
number of samples at one time. However, chemical changes may occur in
a sample over time. Filtration, preservation, and storage at 4°C aid in
maintaining sample integrity over a discrete period, defined as the
holding time. Because of the small number of raw samples received weekly,
samples from successive weeks are grouped or batched for analysis. The
holding times determine the analysis schedule; aliquots 3 (Cl) and 4
are analyzed every two weeks while aliquots 1 (metals) and 2 (NO^, $04)
are analyzed every 4 weeks. Analysis procedures were developed for NSWS
and, except for the use of preservatives, closely mirror those used by
CAL for NADP samples. The procedures presented in the sections below are
reprinted with minor modification from the NSWS Eastern Lake Survey
(Phase I-Synoptic Chemistry) Analytical Methods Manual (Hillman et al.,
1986).
5.2.1 Determination of Ammonium
NOTE: An alternate method using flow injection analysis (FIA) may be
used if sample concentrations are low. The FIA method is
presented in Appendix E.
1) Scope and Application
This method covers the determination of ammonium in natural surface
waters in the range of 0.01 to 2.6 mg/L NH/1". This range is for
photometric measurements made at 630 to 660 nm in a 15-mm or 50-mm
tubular flow cell. Higher concentrations can be determined after
sample dilution. Approximately 20 to 60 samples per hour can be
analyzed.
2) Summary of Method
Alkaline phenol and hypochlorite react with ammonium to form an
amount of indophenol blue that is proportional to the ammonium
concentration. The blue color formed is intensified with sodium
nitroprusside (U.S. EPA, 1983).
3) Interferences
Calcium and magnesium ions may be present in concentrations suf-
ficient to cause precipitation problems during the analysis. A
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Section 5.0
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5 percent EDTA solution is used to prevent the precipitation of
calcium and magnesium compounds.
Sample turbidity may interfere with this method. Turbidity is
removed by filtering the sample at the processing laboratory.
Sample color that absorbs in the photometric range used also
interferes.
4) Safety
The calibration standards, sample types, and most reagents used in
this method pose no hazard to the analyst. Use protective clothing
(lab coat and gloves) and safety glasses when preparing reagents.
5) Apparatus and Equipment
o
Technicon AutoAnalyzer Unit (AAI or AAII) consisting of sampler,
manifold (AAI) or analytical cartridge (AAII), proportioning
pump, heating bath with double-delay coil (AAI), colorimeter
equipped with 15-mm tubular flow cell and 630- to 660-nm filters,
recorder, and digital printer for AAII (optional).
6) Reagents and Consumable Materials
0 Water—Water must meet the specifications for Type I Reagent
Water given in ASTM D 1193 (ASTM, 1984).
0 Sulfuric Acid (5N), Air Scrubber Solution—Carefully add 139 mL
concentrated sulfuric acid to approximately 500 ml ammonia-free
water. Cool the solution to room temperature, and dilute it to
1 L with water.
0 Sodium Phenol ate Solution—Using a 1-L Erlenmeyer flask, dissolve
83 g phenol in 500 ml water. In small increments, cautiously add
with agitation 32g NaOH. Periodically cool flask under flowing
tap water. When it is cool, dilute the solution to 1 L with
water.
0 Sodium Hypochlorite Solution—Dilute 150 ml of a bleach solution
containing 5.25 percent NaOCl (such as Clorox) to 500 ml with
water. The concentration of available chlorine should be
approximately 2 to 3 percent. Clorox is a proprietary product,
and its formulation is subject to change. The analyst must
remain alert to any variation in this product which is significant
to its use in this procedure. Because of the instability of this
product, storage over an extended period should be avoided.
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Section 5.0
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0 Disodium Ethylenediaminetetraacetate Acid (EDTA) (5 percent w/v)-
Dissolve 50 g EDTA (disodium salt) and approximately six pellets
NaOH in 1 L water.
0 Sodium Nitroprusside (0.05 percent w/v)—Dissolve 0.5 g sodium
nitroprusside in 1 L deionized water.
0 NH4+ Stock Standard Solution (1,000 mg/L)—Dissolve 2.9654 g
anhydrous ammonium chloride, NH4C1 (dried at 105°C for 2 hours),
in water, and dilute the solution to 1,000 ml.
0 Standard Solution A (10.00 mg/L NH4+)—Dilute 10.0 ml NH4+ stock
standard solution to 1,000 ml with water.
0 Standard Solution B (1.000 mg/L NH4+)--Dilute 10.0 mL standard
solution A to 100.0 mL with water.
Using standard solutions A and B, prepare (fresh daily) the
following standards in 100-mL volumetric flasks:
NH4+ (mg/L) mL Standard Solution/100 mL
Solution B
0.01 1.0
0.02 2.0
0.05 5.0
0.10 10.0
NH4+ (mg/L) mL Standard Solution/100 mL
Solution A
0.20 2.0
0.50 5.0
0.80 8.0
1.00 10.0
1.50 15.0
2.00 20.0
7) Sample Collection, Preservation, and Storage
Samples are filtered and preserved (addition of H2S04 until pH <2)
in the processing laboratory. The samples must be stored in the
dark at 4°C when not in use.
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Section 5.0
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8) Calibration and Standardization
Analyze the series of ammonium standards by following the procedure
described in Section 10. Prepare a calibration curve by plotting
the peak height versus standard concentration.
9) Quality Control
The required QC is described in Section 3.1.
10) Procedure
Since the intensity of the color used to quantify the concentration
is pH-dependent, the acid concentration of the wash water and the
standard ammonium solutions should approximate that of the samples.
For example, if the samples have been preserved with 2 ml concen-
trated H2S04/L, the wash water and standards should also contain
2 ml concentrated
Step l--For a working range of 0.01 to 2.6 mg/L NH/^ (AAI), set up
the manifold as shown in Figure 5-1. For a working range of 0.01
to 1.3 mg/L NH^+ (AAII), set up the manifold as shown in Figure 5-2.
Higher concentrations may be accommodated by sample dilution.
Step 2--Allow both colorimeter and recorder to warm up for 30
minutes. Obtain a stable baseline with all reagents, feeding
distilled water through the sample line.
Step 3 — For the AAI system, sample at a rate of 20/hr, 1:1.
For the AAII system, use a 60/hr 6:1 cam with a common wash.
Step 4--Load sampler tray with samples.
Step 5 — Switch sample line from water to sampler, and begin analysis,
Step 6--Dilute and reanalyze samples which have an ammonium concen-
tration exceeding the calibrated concentration range.
11) Calculations
Compute concentration of samples by comparing sample peak heights
with calibration curve. Report results in mg/L NH^+.
12) Precision and Accuracy
In a single laboratory (EMSL-Cincinnati) , by using surface-water
samples at concentrations of 1.41, 0.77, 0.59, and 0.43 mg NH3-N/L,
the standard deviation was ±0.005 (U.S. EPA, 1983).
-------
PROPORTIONING
SM = SMALL MIXING COIL
LM = LARGE MIXING COIL
HEATING BATH f\\
37° C
WASH WATER
,L TO SAMPLER
IL
LM
r
LM
r * d b d ff
) f
i
^
SM
mnsif
•
: WASTE
n
I
^J
1
IP B
G G
R R
G G
W W
W W
R R
P P
ml/min.
2.9 WASH
2.0 SAMPLE
i
0.8 EDTA }
2.0 AIR*
0
SAMPLER
?0/hr.
1:1
0.6 PHENOLATE
0.6 HYPOCHLORITE
0.6 NITROPRUSSIDE
2.5
_ I WASTE
c
I
RECORDER
COLORIMETER
15mm FLOW CELL
650-660 nm FILTER
SCRUBBED THROUGH
5N H2SO4
Figure 5-1. Ammonia Manifold AAI.
•W O 73 to
o» tu n> (D
«Q c* < o
n> n> -••<-»•
. . to — '.
O "^^
-h 00
tn
03
3
01
-------
HEATING BATH
50° C
PROPORTIONING
PUMP
ml/min.
SAMPLER
60/hr.
6:1
WASH WATER
TO SAMPLER
0.42 PHENOLATE
0.32 HYPOCHLORITE
0.42 NITROPRUSSIDE
WASTE
COLORIMETER
50mm FLOW CELL
650-660 mm FILTER
* SCRUBBED THROUGH
5N
Figure 5-2. Ammonia Manifold AAII.
-O O TO fV CD fP
10 <-!• < O
n> o> -••€-»•
.. m ->.
I—1 -"• O
03
00
o
oo
en
CO i
-J
tn
•
O
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Section 5.0
Revision 1
Date: 4/87
Page 19 of 35
In a single laboratory (EMSL-Cincinnati), with surface-water sam-
ples at concentrations of 0.16 and 1.44 mg NH3-N/L, recoveries were
107 percent and 99 percent, respectively (U.S. EPA, 1983). These
recoveries are statistically significantly different from 100
percent.
5.2.2 Determination of Chloride, Nitrate, and Sulfate by Ion Chromatography
1) Scope and Application
This method is applicable to the determination of chloride, nitrate,
and sulfate in natural surface waters by ion chromatography (1C).
It is restricted to use by or under the supervision of analysts
experienced in the use of ion chromatography and in the interpreta-
tion of the resulting ion chromatogram.
2) Summary of Method
Samples are analyzed by 1C. 1C is a liquid chromatographic technique
that combines ion exchange chromatography, eluent suppression, and
conductimetric detection.
A filtered sample portion is injected into an ion chromatograph.
The sample is pumped through a precolumn, separator column, suppres-
sor column, and a conductivity detector. The precolumn and separator
column are packed with a low-capacity anion exchange resin. The
sample anions are separated in these two columns with separation
being based on their affinity for the resin exchange sites.
The suppressor column reduces the conductivity of the eluant to a
low level and converts the sample anions to their acid form. Typ-
ical reactions in the suppressor column are represented as follows:
Na+ HC03~ + R - H > HoC03 + R - Na
(high-conductivity eluant) (Tow conductivity)
Na+ A" + R - H > HA + R - Na
Three types of suppressor columns are available: the packed-bed
suppressor, the fiber suppressor, and the micromembrane suppressor.
The packed-bed suppressor contains a high-capacity cation exchange
resin in the hydrogen form. It is consumed during analysis and must
be periodically regenerated off-line. The latter two suppressors
are based on cation exchange membranes. These suppressors are
continuously regenerated throughout the analysis. Also, their dead
volume is substantially less than that of a packed-bed suppressor.
For these two reasons, the latter two suppressors are preferred.
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Section 5.0
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Page 20 of 35
The separated anions in their acid form are measured with a conduc-
tivity cell. Anion identification is based on retention time.
Quantification is performed by comparing sample peak heights to a
calibration curve generated from known standards (ASTM, 1984; O'Dell
et al., 1984; Topol and Ozdemir, 1984).
3) Interferences
Interferences can be caused by substances with retention times that
are similar to and overlap those of the anion of interest. The
samples are not expected to contain any interfering species. Large
amounts of an anion can interfere with the peak resolution of an
adjacent anion. Sample dilution or spiking can be used to solve
most interference problems.
The water dip or negative peak that elutes near and that can inter-
fere with the chloride peak can be eliminated by the addition of
the concentrated eluant so that the eluant and sample matrix are
similar.
Method interferences may be caused by contaminants in the reagent
water, reagents, glassware, and other sample processing apparatus
that lead to discrete artifacts or elevated baselines in ion chro-
matograms.
Samples that contain particles larger than 0.45 microns and reagent
solutions that contain particles larger than 0.20 microns require
filtration to prevent damage to instrument columns and flow systems.
4) Safety
Normal, accepted laboratory safety practices should be followed
during reagent preparation and instrument operation. The calibra-
tion standards, samples, and most reagents pose no hazard to the
analyst. Protective clothing and safety glasses should be worn when
handling concentrated sulfuric acid.
5) Apparatus and Equipment
0 Ion Chromatograph—Analytical system complete with ion chromato-
graph and all accessories (conductivity detector, autosampler,
data recording system, etc.).
0 Anion Preseparator and Separator Columns—Dionex Series AG-4A
and AS-4A are recommended for use with the 2000i ion chromato-
graphs. AG-3 and AS-3 columns are recommended for older ion
chromatographs.
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Section 5.0
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Page 21 of 35
0 Suppressor Column--Dionex AFS fiber suppressor or AMMS membrane
suppressor is recommended.
6) Reagents and Consumable Materials
Unless stated otherwise, all chemicals must be ACS reagent grade or
better. Also, salts used in preparation of standards must be dried
at 105°C for 2 hours and must be stored in a desiccator until they
are weighed.
0 Deionized Water—Water must meet the specifications for Type I
Reagent Water given in ASTM D 1193 (ASTM, 1984).
0 Eluant Solution (0.0028M NaHC03/0.0020M Na^COa) —Dissolve 0.94 g
sodium bicarbonate (NaHC03) and 0.85 g sodium carbonate
in water and dilute to 4 L. This eluant strength may be
adjusted for different columns according to the recommendations
provided by the manufacturer.
0 Fiber Suppressor Regenerant (0.025 H2S04)--Add 2.8 ml concen-
trated sulfuric acid (^SO/i, Baker Ultrex grade or equivalent) to
4 L water.
0 Stock Standard Solutions — Store stock standards in clean poly-
ethylene bottles (cleaned without acid) at 4°C. Prepare monthly.
a) Bromide Stock Standard Solution (1,000 mg/L Br')--Dissolve
1.2877 g sodium bromide (NaBr) in water and dilute to
1.000 L.
b) Chloride Stock Standard Solution (200 mg/L Cl')— Dissolve
0.3297 g sodium chloride (NaCl) in water and dilute to
1.000 L.
c) Fluoride Stock Standard Solution (1,000 mg/L F~)--Dissolve
2.2100 g sodium fluoride (NaF) in water and dilute to
1.000 L.
d) Nitrate Stock Standard Solution (200 mg/L N03")--Dissol ve
0.3261 g potassium nitrate (KN03) in water and dilute to
1.000 L.
e) Phosphate Stock Standard Solution (2,000 mg/L P)— Dissolve
4.3937 g potassium phosphate (K^PO^ in water and dilute
to 1.000 L.
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Section 5.0
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Date: 4/87
Page 22 of 35
f) Sulfate Stock Standard Solution (1,000 mg/L SO^,2')—Dissolve
1.8141 g potassium sulfate (KgSO^ in water and dilute to
1.000 L.
0 Mixed Resolution Sample (mg/L F' 2 mg/L Cl~, 2 mg/L NO-T,
2 mg/L P, 2 mg/L fir', 5 mg/L S042-).
Prepare by appropriate mixing and dilution of the stock standard
solutions.
7) Sample Collection, Preservation, and Storage
Samples are filtered in the processing laboratory. Nitrate and
sulfate are preserved with mercuric chloride. Store samples at 4°C
when not in use.
8) Calibration and Standardization
Each day (or work shift) analyze a blank and a series of standards
for each analyte, which bracket the expected analyte concentration
range. Suggested concentrations for the dilute standards are given
in Table 5-1.
TABLE 5-1. SUGGESTED CONCENTRATION OF DILUTE CALIBRATION STANDARDS
Standard
1
2
3
4
5
6
cr
0
0.020
0.10
0.50
1.00
3.00
Concentration (mg
N03-
0
0.020
0.10
0.50
1.00
3.00
/L)
so42-
0
0.20
0.50
2.00
5.00
10.00
Prepare a calibration curve for each analyte by plotting peak height
versus standard concentration.
9) Quality Control
General QC procedures are described in Section 3.0.
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Section 5.0
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Page 23 of 35
After calibration, perform a resolution test. Analyze the mixed
standard containing fluoride, chloride, nitrate, phosphate, bromide,
and sulfate. Resolution between adjacent peaks must equal or exceed
60 percent. If it does not, replace or clean the separator colunn
and repeat calibration.
10) Procedure
Step l--Set up the 1C for operation. Typical operating conditions
for a Dionex 2010i 1C are given in Table 5-2. Other conditions may
be used depending upon the columns and system selected.
TABLE 5-2. TYPICAL 1C OPERATING CONDITIONS
1C: Dionex 2010i Sample Loop Size: 250 p
Precolumn: AG-4A
Separator Column: AS-4A
Suppressor Column: AMMS
Eluant: 0.75mM NaHC03/2.0mM Na2C03
Eluant Flow Rate: 2.0 mL/min
Regenerant: 0.025N ^$04
Regenerant Flow Rate: 3 mL/min
Ion Typical Retention Time (min.)
Cl- 1.8
N03' 4.9
V
SO/,2' 8.1
Step 2--Adjust detector range to cover the concentration range of
samples.
Step 3—Load injection loop (manually or via an autosampler) with
the sample (or standard) to be analyzed. Load 5 to 10 times the
volume required to flush the sample loop thoroughly. Inject the
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Section 5.0
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sample. Measure and record (manually or with a data system) the
peak heights for each analyte.
Step 4--Di1ute and reanalyze samples which have an analyte concen-
tration exceeding the calibrated concentration range.
11) Calculations
Compute the sample concentration by comparing the sample peak
height with the calibration curve. Report results in mg/L.
12) Precision and Accuracy
Typical single operator results for surface water analyses are
listed in Table 5-3 (O'Dell et al., 1984).
TABLE 5-3. SINGLE-OPERATOR ACCURACY AND PRECISION (O'Dell et al., 1984)a
Ion
CT
N03-
so24-
Spike
(mg/L)
1.0
0.5
10.0
Number of
Replicates
7
7
7
Mean %
Recovery
105
100
112
Standard
Deviation (mg/L)
0.14
0.0058
0.71
aThe chromatographic conditions used by O'Dell were slightly different than
those listed in Table 5-2. However, the results are typical of what is
expected.
5.2.3 Determination of Metals (Ca, K, Mg, Na) by Atomic Absorption
Spectroscopy
NOTE: An alternate method for Ca and Mg determination using Inductively
Coupled Plasma (ICP) Emission Spectroscopy may be used if
sample concentrations are low. The ICP method is presented in
Appendix F.
1) Scope and Application
Metals in solution may be readily determined by atomic absorption
Spectroscopy. The method is simple, rapid, and applicable to the
determination of Ca, K, Mg, and Na in natural surface waters.
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Section 5.0
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Detection limits, sensitivity, and optimum ranges of the metals vary
with the makes and models of atomic absorption spectrophotometers.
The data listed in Table 5-4, however, provide some indication of
the actual concentration ranges measurable by direct aspiration
(flame) techniques. In the majority of instances, the concentration
range shown in the table for analysis by direct aspiration may be
extended much lower with scale expansion and, conversely, may be
extended upward by using a less sensitive wavelength or by rotating
the burner head. Detection limits by direct aspiration may also be
extended through concentration of the sample and through solvent
extraction techniques. The concentration ranges given in Table 5-4
are somewhat dependent on equipment such as the type of spectro-
photometer, the energy source, and the degree of electrical expan-
sion of the output signal.
TABLE 5-4. ATOMIC ABSORPTION CONCENTRATION RANGES1
Flame
Metal
Calcium
Magnesium
Potassium
Sodium
Detection
Limit
(mg/L)
0.01
0.001
0.01
0.002
Sensi-
tivity
(mg/L)
0.08
0.007
0.04
0.015
Optimum
Concentration
Range
(mg/L)
0.2 to 7
0.02 to 0.5
0.1 to 2
0.03 to 1
*The concentrations shown are obtainable with any
satisfactory atomic absorption spectrophotometer.
2) Summary of Method
In direct aspiration atomic absorption spectroscopy, a sample is
aspirated and atomized in a flame. A light beam from a hollow
cathode lamp, whose cathode is made of the element to be determined,
is directed through the flame into a monochromator and onto a detec-
tor that measures the amount of light absorbed. Absorption depends
upon the presence of free unexcited ground state atoms in the flame.
Since the wavelength of the light beam is characteristic of only the
metal being determined, the light energy absorbed by the flame is a
measure of the concentration of that metal in the sample. This
principle is the basis of atomic absorption spectroscopy. A mono-
chromator isolates the characteristic radiation from the hollow
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Section 5.0
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cathode lamp, and a photo-sensitive device measures the attenuated
transmitted radiation. Dissolved metals (Ca, K, Mg, and Na) are
determined in a filtered sample (aliquot 1) by flame atomic absorp-
tion spectroscopy (U.S. EPA, 1983).
3) Definitions
0 Optimum Concentration Range—This is a range, defined by limits
expressed in concentration, below which scale expansion must be
used and above which curve correction should be considered. This
range will vary with the sensitivity of the instrument and with
the operating conditions employed.
0 Sensitivity—Sensitivity is the concentration in milligrams of
metal per liter that produces an absorption of 1 percent.
0 Dissolved Metals--Dissolved metals are those constituents (metals)
which can pass through a 0.45-ym membrane filter.
4) Interferences
The most troublesome type of interference in direct aspiration
atomic absorption spectrophotometry is usually termed "chemical"
and is caused by lack of absorption of atoms bound in molecular
combination in the flame. This phenomenon can occur when the flame
is not sufficiently hot to dissociate the molecule, as in the case
of phosphate interference with magnesium, or because the dissoci-
ated atom is immediately oxidized to a compound that will not
dissociate further at the temperature of the flame. The addition of
lanthanum will overcome the phosphate interference in the magnesium
and calcium determinations.
Chemical interferences may also be eliminated by separating the
metal from the interfering material. While complexing agents are
primarily from the interfering material employed to increase the
sensitivity of the analysis, they may also be used to eliminate or
reduce interferences.
lonization interferences occur when the flame temperature is
sufficiently high to generate the removal of an electron from a
neutral atom, giving a positively charged ion. This type of
interference can generally be controlled by the addition, to
both standard and sample solutions, of a large excess of an easily
ionized element.
Although quite rare, spectral interference can occur when an
absorbing wavelength of an element present in the sample but not
being determined falls within the width of the absorption line of
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Section 5.0
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the element of interest. The results of the determination will then
be erroneously high because of the contribution of the interfering
element to the atomic absorption signal. Also, interference can
occur when resonant energy from another element in a multi-element
lamp or from a metal impurity in the lamp cathode falls within the
bandpass of the slit setting and when that metal is present in the
sample. This type of interference may sometimes be reduced by
narrowing the slit width.
5) Safety
The calibration standards, sample types, and most reagents pose
no hazard to the analyst. Use protective clothing (lab coat and
gloves) and safety glasses when preparing reagents, especially
when concentrated acids and bases are used. The use of concen-
trated hydrochloric acid should be restricted to a hood.
Follow the safety precautions recommended by the manufacturer
when operating the atomic absorption spectrophotometer.
Follow good laboratory practices when handling compressed gases.
6) Apparatus and Equipment
0 Atomic Absorption Spectrophotometer--The spectrophotometer
used shall be a single- or dual-channel, single or double-
beam instrument having a grating monochromator, photomulti-
plier detector, adjustable slits, a wavelength range of 190
to 800 nm, and provisions for interfacing with a strip chart
recorder.
0 Burner—The burner recommended by the particular instrument
manufacturer should be used. For certain elements, the
nitrous oxide burner is required.
0 Hollow Cathode Lamps--Single element lamps are preferred.
Electrodeless discharge lamps may also be used when available.
7) Reagents and Consumable Materials
General reagents used in each metal determination are listed in
this section. Reagents specific to particular metal determinations
are listed in the particular procedure description for that metal.
0 Concentrated Hydrochloric Acid (12M HC1)--Ultrapure grade (Baker
InstraAnalyzed or equivalent) is required.
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Section 5.0
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0 HC1 (1 percent v/v)—Add 5 mL concentrated HC1 to 495 ml water.
0 Nitric Acid (0.5% v/v HNO - UHrapure grade, Baker Instra-
Analyzed or equivalent)--Carefully dilute HN03 in water in the
ratio of 0.5 to 100.
0 Stock Standard Metal Solutions—Prepare as directed in the
individual metal procedures. Commercially available stock
standard solutions may also be used.
0 Dilute Calibration Standards—Prepare a series of standards of
the metal by dilution of the appropriate stock metal solution to
cover the concentration range desired.
0 Fuel and Oxidant—Commercial grade acetylene is generally
acceptable if replaced at 100 Ibs pressure. Air may be supplied
from a compressed air line, from a laboratory compressor, or from
a cylinder of compressed air. Reagent grade nitrous oxide is
also required for certain determinations. Standard, commercially
available argon and nitrogen are required for furnace work.
0 Water—Water must meet the specifications for Type I Reagent
Water given in ASTM D 1193 (ASTM, 1984).
8) Sample Collection, Preservation, and Storage
Samples are processed in the processing laboratory. The sample for
dissolved metals (aliquot 1) is filtered through a 0.45-ym membrane
filter and is then preserved by acidifying to a pH <2 with nitric
acid. After processing, the samples are transferred to the analyt-
ical laboratory.
9) Calibration and Standardization
The calibration procedure varies slightly with the various atomic
absorption instruments.
For each analyte, calibrate the atomic absorption instrument by
analyzing a calibration blank and a series of standards and by
following the instructions in the instrument operating manual.
The concentration of standards should bracket the expected sample
concentration. However, the linear range of the instrument should
not be exceeded.
When indicated by the matrix spike analysis, the analytes must be
quantified by the method of standard additions. In this method,
equal volumes of sample are added to a deionized water blank and to
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Section 5.0
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three standards containing different known amounts of the test
element. The volume of the blank and of each standard must be the
same. The absorbance of each solution is determined and is then
plotted on the vertical axis of a graph; the concentrations of the
known standards are plotted on the horizontal axis. When the
resulting line is extrapolated to zero absorbance, the point of
intersection of the abscissa is the concentration of the unknown.
The abscissa on the left of the ordinate is scaled the same as on
the right side but in the opposite direction from the ordinate. An
example of a plot so obtained is shown in Figure 5-3. The method of
standard additions can be very useful; however, for the results to
be valid, the following limitations must be taken into consideration:
0 The absorbance plot of sample and standards must be linear over
the concentration range of concern. For best results, the slope
of the plot should be nearly the same as the slope of the aqueous
standard curve. If the slope is significantly different (more
than 20 percent), caution should be exercised.
0 The effect of the interference should not vary as the ratio of
analyte concentration to sample matrix changes, and the standard
addition should respond in a similar manner as the analyte.
0 The determination must be free of spectral interference and must
be corrected for nonspecific background interference.
10) Quality Control
The required QC procedures are described in Section 3.1.
11) Procedure
General procedures for flame atomic absorption analysis are given in
Section lla. Detailed procedures for determinating Ca, K, Mg, and
Na are given in Sections lib through lie.
a) Flame Atomic Absorption Spectroscopy
Differences between the various makes and models of satisfactory
atomic absorption spectrophotometers prevent the formulation of
detailed instructions applicable to every instrument. The
analyst should follow the operating instructions which are
provided by the manufacturer for the particular instrument. In
general, after choosing the proper hollow cathode lamp for the
analysis, the lamp should be allowed to warm up for a minimum of
15 minutes. During this period, align the instrument, position
the monochromator at the correct wavelength, select the proper
monochromator slit width, and adjust the hollow cathode current
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ZERO
ABSORBANCE
CONCENTRATION
Cone, of
Sample
AddnO
No Addn
Addn 1
Addn of 60%
of Expected
Amount
Addn 2
Addn of 100%
of Expected
Amount
Addn 3
Addn of 160%
of Expected
Amount
Figure 5-3. Standard Addition Plot.
by following the recommendations of the manufacturer. Subse-
quently, light the flame and regulate the flow of fuel and
oxidant, adjust the burner and nebulizer flow rate for maximum
percent absorption and stability, and balance the photometer.
Run a series of standards of the element under analysis, and
calibrate the instrument.
Aspirate the samples, and determine the concentrations either
directly (if the instrument reads directly in concentration
units) or from the calibration curve.
b) Procedure for Determination of Dissolved Calcium
Samples for determination of dissolved calcium (filtered and
preserved in the field) are analyzed by flame atomic absorption
spectroscopy for calcium (U.S. EPA, 1983).
1) Preparation of Reagents
Lanthanum chloride matrix modifier solution (LaCls)--
Dissolve 29 g I^Oj, slowly and in small portions, in 250 ml
concentrated HC1 (Caution: Reaction is violent), and dilute
to 500 ml with water.
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2) Preparation of Calcium Standard Solutions
Calcium stock solution (500 mg/L Ca)--Suspend 1.250 g
(analytical reagent grade, dried at 180°C for 1 hour before
weighing) in water, and dissolve it cautiously with a minimum
of dilute HC1. Dilute the solution to 1,000 mL with water.
Dilute calibration standards—Prepare a series of dilute Ca
standards from the calcium stock solution to span the
desired concentration range. These stocks are stable for
two weeks or longer.
3) Suggested Instrumental Conditions (General)
Lamp—Ca, hollow cathode
Wavelength—422.7
Fuel—acetylene
Oxidant--air
Flame—reducing
4) Analysis Procedure
Step 1—To each 10.0 mL volume of dilute calibration stand-
ard, blank, and sample, add 1.00 mL LaCl3 solution (e.g.,
add 2.0 mL Lad 3 solution to 20.0 mL sample).
Step 2—Calibrate the instrument as directed by the
manufacturer.
Step 3—Analyze the samples.
Step 4—Dilute and reanalyze any samples which have a con-
centration exceeding the calibrated range.
Report results as mg/L Ca.
NOTE 1: Phosphate, sulfate, and aluminum interfere but are
masked by the addition of lanthanum. Because low
calcium values result if the pH of the sample is
above 7, both standards and samples are prepared in
dilute acid solution. Concentrations of magnesium
greater than 1,000 mg/L also cause low calcium
values. Concentrations of up to 500 mg/L each of
sodium, potassium, and nitrate cause no inter-
ference.
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NOTE 2: Anionic chemical interferences can be expected if
lanthanum is not used in samples and standards.
NOTE 3: The nitrous oxide-acetylene flame will provide two
to five times greater sensitivity and freedom from
chemical interferences. lonization interferences
should be controlled by adding a large amount of
alkali to the sample and standards. The analysis
appears to be free from chemical suppressions in
the nitrous oxide-acetylene flame.
5) Precision and Accuracy—In a single laboratory (EMSL-
Cincinnati), with distilled water spiked at concentrations
of 9.0 and 36 mg Ca/L, the standard deviations were ±0.3 and
±0.6, respectively. Recoveries at both these levels were 99
percent.
c) Procedure for Determination of Dissolved Magnesium
The samples for determination of dissolved magnesium (filtered
and preserved in the field) are analyzed by flame atomic
absorption spectroscopy.
1) Preparation of Reagents
Lanthanum chloride solution (LaCl3)--Dissolve 29 g 13303,
slowly and in small portions, in 250 ml concentrated HC1
(Caution: Reaction is violent), and dilute the solution
to 500 mL with water.
2) Preparation of Magnesium Standard Solutions
Stock solution (500 mg/L Mg)--Dissolve 0.829 g magnesium
oxide, MgO (analytical reagent grade), in 10 ml of HN03, and
dilute the solution to 1 L with water.
Dilute calibration standards—Daily, prepare from the Mg
stock solution a series of Mg standards that span the desired
concentration range.
3) Suggested Instrumental Conditions (General)
Lamp--Mg, hollow cathode
Wavelength—285.2 nm
Fuel--acetylene
Oxidant—air
Flame—oxidizing
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4) Analysis Procedure
Step l--To each 10.0 mL dilute calibration standard, blank,
and sample, add 1.00 ml LaCl3 solution (e.g., add 2.0 ml
LaCl3 solution to 20.0 ml sample).
Step 2--Calibrate the instrument as directed by the
manufacturer.
Step 3— Analyze the samples.
Step 4--Dilute and reanalyze any samples which have a
concentration exceeding the linear range.
Report results as mg/L Mg.
5) Precision and Accuracy-- In a single laboratory (EMSL-
Cincinnati), with distilled water spiked at concentrations
of 2.1 and 8.2 mg/L Mg , the standard deviations were ±0.1
and ±0.2, respectively. Recoveries at both of these levels
were 100 percent.
d) Procedure for Determination of Dissolved Potassium
The samples for determination of dissolved potassium (filtered
and preserved in the field) are analyzed by flame atomic absorp-
tion spectroscopy for potassium (U.S. EPA, 1983).
1) Preparation of Potassium Standard Solutions
Potassium stock solution (100 mg/L K)— Dissolve 0.1907 g KC1
(analytical reagent grade, dried at 110°C) in water, and
bring volume of solution to 1 L.
Dilute calibration standards—Daily, prepare a series of
calibration standards spanning the desired concentration
range. Match the acid content of the standards to that of
the samples (ca. 0.1 percent [v/v]
2) Suggested Instrumental Conditions (General)
Lamp--K, hollow cathode
Wavelength--766.5 nm
Fuel --acetylene
Oxidant--air
Flame—slightly oxidizing
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3) Analysis Procedure
Step 1—Calibrate the instrument as directed by the
manufacturer.
Step 2--Analyze the samples.
NOTE: In air-acetylene or other high-temperature flames
(>2,800°C), potassium can experience partial
ionization which indirectly affects absorption
sensitivity. The presence of other alkali salts in
the sample can reduce this ionization and can thereby
enhance analytical results. The ionization suppres-
sive effect of sodium is small if the ratio of Na to
K is under 10. Any enhancement which is due to
sodium can be stabilized by adding excess sodium
(1,000 yg/mL) to both sample and standard solutions.
If more stringent control of ionization is required,
the addition of cesium should be considered. Reagent
blanks should be analyzed to correct for potassium
impurities in the buffer stock.
4) Precision and Accuracy—In a single laboratory (EMSL-
Cincinnati), with distilled water samples spiked at concen-
trations of 1.6 and 6.3 mg/L K, the standard deviations were
±0.2 and ±0.5, respectively. Recoveries at these levels
were 103 percent and 102 percent, respectively.
e) Procedure for Determination of Dissolved Sodium
The samples for determination of dissolved sodium (filtered and
preserved in the field) are analyzed by flame atomic absorption
spectroscopy for sodium (U.S. EPA, 1983).
1) Preparation of Sodium Standard Solutions
Sodium stock solution (1,000 mg/L Na)—Dissolve 2.542 g NaCl
(analytical reagent grade, dried at 140°C) in water, and
bring the volume of the solution to 1 L.
Dilute calibration standards—Daily, prepare a series of
calibration standards spanning the desired concentration
range. Match the acid content of the standards to that of
the samples (ca. 0.1 percent [v/v] HMOs).
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2) Suggested Instrumental Conditions (General)
Lamp--Na, hollow cathode
Wavelength—589.6 nm
NOTE: The 330.2-nm resonance line of sodium, which has a
relative sensitivity of 185, provides a convenient
way to avoid the need to dilute more concentrated
solutions of sodium.
Fuel—acetylene
Oxidant--air
Flame—oxidizing
3) Analysis Procedure
Step I—Calibrate the instrument as directed by the
manufacturer.
Step 2—Analyze the samples.
Step 3—Dilute and reanalyze any samples which have a
concentration exceeding the calibrated range.
Report results as mg/L Na.
NOTE: Low-temperature flames increase sensitivity by
reducing the extent of ionization of this easily
ionized metal. Ionization may also be controlled
by adding potassium (1,000 mg/L) to both standards
and samples.
4) Precision and Accuracy--!n a single laboratory (EMSL-
Cincinnati), with distilled water samples spiked at levels
of 8.2 and 52 mg/L Na, the standard deviations were ±0.1 and
±0.8, respectively. Recoveries at these levels were 102
percent and 100 percent.
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6.0 DATA MANAGEMENT
Most data for this program are provided on floppy disk. A limited amount
of data must be manually entered (e.g., Belfort rain gage data). Hand
entered data are reviewed for transcription accuracy. Evaluation of data
quality is described in Section 3.0. Following this evaluation, data of
poor or unknown quality are removed from the data base. Operator records
are reviewed, and data corresponding to calibrations, quality control
checks, maintenance activities, or malfunctions are removed.
The remaining verified data are analyzed and interpreted in accordance
with the project objectives. Inter-instrument comparisons are made for
instruments of the same model operating over the same sampling interval.
These include the two Belfort rain gages, the two bulk samplers, duplicate
weekly and daily snow cores, paired weekly wet/dry collectors, and paired
daily wet/dry collectors. Comparisons are made of the water equivalent
and chemistry results. Specific comparisons include computation of means,
range, %RSD, and paired t-tests.
Comparisons between different instrument models employ statistical tests
similar to those described above. All instruments operating over the same
sampling interval are intercompared with intercomparison being based on
water equivalent and chemistry results. In addition, comparisons are made
of same model and different model instruments operating over different
sampling intervals. This comparison of daily and weekly samples is made
possible by integration of daily samples to create a "synthetic" weekly
sample. Graphics are also used to illustrate temporal variability results.
The water equivalent and chemistry results of each instrument are also
compared to ground truth measurements. The ground truth measurements
include snow pit density measurements (water equivalent only) and snow
cores (chemistry and water equivalent). To make these comparisons, the
inter-instrument and spatial variability must be quantified; comparisons
between instruments and ground truth measurements are generally made on
means rather than on individual sample data.
Operational reliability is assessed on the basis of field documentation
and data quality. Statistical analyses, comparison to ground truth, and
operational reliability are all considered in the evaluation of recom-
mended instruments and sampling intervals; this is the substance of the
final project objective.
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7.0 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM
standards, Vol. 11.01, Standard Specification for Reagent Water, D 1193-77
(reapproved 1983). ASTM, Philadelphia, Pennsylvania.
Chaloud, D. J., L. 0. Arent, B. B. Dickes, 0. D. Nitterauer, M. 0. Morison,
and D. V. Peck, 1986. National Surface Water Survey Eastern Lake Survey -
Phase II National Stream Survey Phase I Processing Laboratory Training and
Operations Manual, EMSL/ORD. U.S. Environmental Protection Agency,
Las Vegas, Nevada.
Costle, D. M., May 30, 1979(a). Administrator's Memorandum, EPA Quality
Assurance Policy Statement. U.S. Environmental Protection Agency,
Washington, D.C.
Costle, D. M., June 14, 1979(b). Administrator's Policy Statement, Quality
Assurance Requirements for All EPA Extramural Projects Involving
Environmental Measurements. U.S. Environmental Protection Agency,
Washington, D.C.
Drouse, S. K, D. C. Hillman, L. W. Creelman, and S. J. Simon, 1986. National
Surface Survey Eastern Lake Survey (Phase I - Synoptic Chemistry) Quality
Assurance Plan.EPA/600 4-86/008. U.S Environmental Protection Agency.
Goodison B. E., H. L. Ferguson, and G. A. McKay, 1981. Measurement and data
analysis. Handbook of Snow - Principles, Processes, Management., and Use,
Edited by Gray, D. M. and Male, D. H.Pergamon Press, Willowdafe,
Ontario, pp. 191-274.
Goodison B. E., and J. R. Metcalfe, 1982. Canadian snow gauge experiment
recent results. Proceedings of the Western Snow Conference,
April 20-23, 1982. Reno, Nevada.
Grubbs, F. E., 1969. Procedures for Detecting Outlying Observations in
Samples. Technometrics, TCMTA, v. 11, n. 4, pp. 1-21.
Hillman, D. C., J. F. Potter, and S. J. Simon, 1986. National Surface Water
Survey Eastern Lake Survey (Phase I - Synoptic Chemistry) Analytical
Methods Manual . EPA/600 4-86-009. U.S. Environmental Protection Agency,
Las Vegas, Nevada.
LaChapelle, E. R., 1969. Field Guide to Snow Crystals. University of
Washington Press, Seattle.
Laird, L. B., H. E. Taylor, and V. C. Kennedy, 1986. Snow Chemistry of the
Cascade - Sierra Nevada Mountains, Environ. Sci. Technol. v. 20,
pp. 275-290.
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Page 1 of 2
McQuaker, N. R., P. D. Kluckner, and D. K. Sandberg, 1983. Chemical Analysis
of Acid Precipitation: pH and Acidity Determinations. Environ. Sci.
Techno!., v. 17 n. 7, pp. 431-435.
O'Dell, J. W., J. D. Pfaff, M. E. Gales, and G. D. McKee, 1984. Technical
Addition to Methods for the Chemical Analysis of Water and Wastes, Method
300.0, The Determination of Inorganic Anions in Water by Ion Chromatography,
EPA-600/4-85-017. U.S. Environmental Protection Agency, Cincinnati, Ohio.
Orion Research Incorporated, 1983. Instruction Manual - Model 611 pH/milli-
volt manual. Orion, Cambridge, Massachusetts.
Suarez, F. X., 1987. Personal Communication.
Svoboda, L., and R. Olson, 1986. Quality Assurance Project Plan for the Rocky
Mountain Deposition Monitoring Project as part of the Western Conifers
Research Cooperative, ERL/EPA U.S. EPA Corvallis, Oregon. Draft.
Topol, L. E., and S. Ozdemir, 1984. Quality Assurance Handbook for Air Pollu-
tion Measurement Systems: Vol. V. Manual for Precipitation Measurement
Systems, Part II. Operations and Maintenance Manual. EPA-600/4-82-042b.
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical
Analysis of Water and Wastes. EPA-600/4-79-020. U.S. EPA, Cincinnati,
Ohio.
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Appendix A
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Page 1 of 7
APPENDIX A
DAS OPERATION
A.O PROGRAM: SAMPLER
Version Documented: 2.00
Date: 11 February 1987
A.I Introduction
SAMPLER is a program designed to acquire meteorological data continuously
in analog and digital form in a remote setting. It is to operate in a
relatively severe environment with unreliable electrical power. Therefore
it is designed to be self starting and automatic with as much data file
protection as possible.
A.2 Hardware Environment
SAMPLER is designed to operate on an IBM PC or compatible computer. The
computer must be equipped with a MetroByte DAS-8 Analog to Digital (A/D)
converter board.
A.3 Operating SAMPLER
To start SAMPLER, type the command
SAMPLER
from any directory on the computer ("" means "press the Carriage Return
or ENTER key"). The program will immediately take its first sample, enter
it into a file for that day, display a summary of the sample on the console,
and wait for about one minute. Then the process repeats.
Normally, a command to start the program will automatically be given when-
ever power is first applied to the computer (or when it is reset). This is
done by including the command SAMPLER in the AUTOEXEC.BAT file, which
includes a variety of startup commands. Therefore, the starting sequence
given above is only necessary after the program has been intentionally
halted.
Please refer to section (7) for precautions to guarantee that the date
(which is important for data file generation) is maintained properly.
A.4 Stopping SAMPLER
To halt SAMPLER, press the ESCape key (on the top left of the keyboard for
the "new-style" IBM PC/AT keyboard). Within about a second, the prompt
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Terminate [Y/N]?
will appear. You must press the "y" key (either upper or lower case)
within approximately two seconds to terminate. No is needed.
When the program is stopped, the computer can be used for any other
desired purpose, such as copying data files to floppy disk. When the
other activity has been completed, restart SAMPLER as indicated in (3).
A.5 Other Keyboard Input
The design of SAMPLER assumes that the computer is usually completely
dedicated to data acquistion and that it is often untended. To minimize
the danger of tampering, "busy fingers," or carelessness, keystrokes other
than ESCape are rejected and produce an audible tone and the message
"Keyboard input ignored." Also, the same response is given after an
ESCape if there is no response within about two seconds or if the response
is other than "y" or "n."
If the program has been terminated properly, the following functions may
be accessed:
Function
view data files:
print data files:
format the disk:
(for drive A):
(for drive B):
copy to disk:
(for drive A):
(for drive B):
restart "Sampler Ver.
2.0"
Command
type YYMMDD.DAT
print YYMMDD.DAT
format A:/s
format B:/s
copy *.DAT A:
copy *.DAT B:
(easiest method) press ALT,
DEL,CTRL keys simultaneously
A.6 Data Files
SAMPLER places its records into a file whose name is derived from the
current date. The file name is of the form
YYMMDD.DAT
where YY, MM, and DD are year, month, and day numbers. For example,
files 870101.DAT and 871231.DAT would be used for 1 January 1987 and
31 December 1987, respectively.
At each new record, the current day's file is opened (or created if it
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does not exist), a new record is appended at its end, and it is closed.
This assures file integrity in the event of power failure.
Note that if the program is halted and then restarted, data will continue
to be appended to the current day's file if it existed before the restart
and if it was not deleted or renamed.
The data files are standard MS-DOS "ASCII" (American Standard Code for
Information Interchange) files. They can be viewed or printed with the
MS-DOS "TYPE" or "PRINT" commands or processed with any text editor. The
file format is
hh:mm:ss www.w ddd X X X
where "hh," "mm," and "ss" are sample time hours, minutes, and seconds,
"www.w" is wind speed in meters/second (m/s) (to a precision of 0.1 m/s),
"ddd" is wind direction bearing in degrees (0 to 359), and "X X X" is the
state of three moisture detectors. The states are "W" for wet (high signal
level) or "D" for dry (low signal level).
A.7 Maintaining the Proper Date
SAMPLER obtains the date from MS-DOS when it is first started, and MS-DOS
in turn obtains it from an internal clock/calendar whenever the computer is
reset or powered up. As the time of day passes midnight (23:59:59 to 00:00:
00), the internal copy of the date of SAMPLER is updated to the next day.
A.8 Sample Timing
SAMPLER spends most of its time in a delay loop in a procedure named Wait-
for-1-Minute. This procedure makes 60 calls to an internal procedure named
Delay that waits for (approximately) 1,000 milliseconds (one second). This
delay value is established in a constant named OneSecond that is currently
set to 1,000. If required, this constant can be raised or lowered to adjust
the sampling interval. If it is changed, the program will need to be
recompiled (Section 13).
A.9 Hardware Configuration
SAMPLER assumes that the DAS-8 A/D converter is used as follows (Pin numbers
refer to the 37-pin connector on the DAS-8 board):
A/D Converter Analog Channels:
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Channel
0
1
2
3
4-7
Pin Number
Signal Ground
37
Not used
Not used
34
Not used
18
15
Binary Inputs
Inputs Pin Number
1
2
3
25
26
27
Purpose
Wind Direction Signal
Wind Speed Indicator Output
Purpose
Moisture Detector No. 1
Moisture Detector No. 2
Moisture Detector No. 3
The computer is also equipped with a parallel interface card that provides
additional binary inputs. SAMPLER does not use that card at the present
time, but it could be modified to do so if necessary.
A.10 Obtaining the Wind Direction
The wind direction indicator is powered by a 5.0 volt d.c. source and
produces an output of 0 to 360 degrees proportionate to 0 to 5.0 volts.
volts
0.0
25
50
75
4.97
degrees
0.0
90.0
180.0
270.0
359.0
A.11 Wind Speed
The wind speed indicator contains a generator that produces an output volt-
age proportional to wind speed. Three calibration values were provided by
data from the manufacturer:
Rotation
Speed (RPM)
300
600
900
Wind Speed
Mi 1es/Hr Knots Meters/sec
32.4
62.4
92.5
28.1
54.2
70.3
14.48
27.90
41.35
Output
Voltage (volts)
1.50
2.90
4.28
The output voltage is clearly nonlinear with respect to rotation speed.
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However, when wind speed is plotted as a function of output voltage
(Figure A-l), the relation is as nearly linear as can be observed from the
three points. Therefore, a simple scaling constant is used to derive
wind speed from its sample (on A/D converter channel 2):
1. Sample channel 2
2. Convert to the equivalent voltage in volts
3. Multiply this by the constant "MetersPerSecondPerVolt" = 41.35/
4.28 = 9.6612
A.12 Moisture Detection
The Wet (high) or Dry (low) status of three moisture detectors must be
monitored. This can be accommodated by the DAS-8 A/D converter hardware,
which makes three TTL-compatible binary input signals available. SAMPLER
uses these. The sampling procedure is simple; it is documented in the DAS-
8 manual and in the appropriate procedure in the source code for SAMPLER.
A.13 Program Elements for SAMPLER
SAMPLER is written in Turbo Pascal, Version 3.02, and is compiled into a
executable file. Both source and executable forms are in directory
C:\FISHER. The program elements are
SAMPLER.PAS: Pascal source code
SAMPLER.COM: Executable form
Directory C:^FISHER also contains the Turbo Pascal system, which includes
the compiler and a full-screen editor. These files are TURBO.COM (the
compiler/editor) and TURBO.MSG (an error message file).
A.14 Generating SAMPLER.COM
If SAMPLER.PAS is modified, it must be recompiled to produce a new execut-
able file SAMPLER.COM. To do this, a "Compile into .COM file" option must
be invoked in TURBO (otherwise the program is compiled only into memory).
To do this,
1. Set the current directory to C:\FISHER with the command
CD\FISHER
2. Start the TURBO system by giving the command
TURBO
3. Select the "Compile to .COM file" option with the following
command sequences (only the first letter is used; no is
used):
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50 n
40
^ 30-
o
UJ
UJ
Q.
CO
O
z
20-
10-
2 3
OUTPUT VOLTAGE (VOLTS)
Figure A-l. Windspeed indicator calibration.
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0 (for "Options")
C (for "Compile to .COM file")
Q (for "Quit Options")
W (for "Workfile")
SAMPLER (to specify the file to compile)
C (to compile it, creating a new SAMPLER.COM)
Q (to exit from TURBO.)
A.15 General Remarks About SAMPLER
The program is written in normal Pascal style, with a number of procedures
defined first, followed finally by a brief main program which is merely a
collection of procedure calls. The procedures are generally straightforward
and are heavily commented, so little needs to be added here.
Access to the registers of the DAS-8 board are handled by "Port" instruc-
tions that write to or read from an Input/Output port on the computer.
The DAS-8 programmers' manual describes the use of the registers in detail,
and the source code of SAMPLER also elaborates on them.
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Appendix B
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APPENDIX B
PROCESSING LABORATORY CONDUCTIVITY METHOD
(Modified from Chaloud et al., 1986, unpublished document)
B.O INTRODUCTION
Conductivity is a measure which often can be linearly correlated with the
ionic strength of a solution. Conductivity can be used to generate a
synthetic ionic balance which can be used as a check on measured ionic
concentrations.
The Beckman Instruments Model RC-20 conductivity bridge employs a Wheatstone
bridge in which the values of three out of four resistances are known.
Conductivity is determined by measuring the reciprocal of the unknown
resistance when a constant voltage is delivered across the conductivity
cell.
B.I Instrument Set-up
NOTE 1: Never acid wash any containers used for conductivity measurement.
Rinse the containers three times with deionized water, or soak
them in deionized water overnight before use.
NOTE 2: Store the conductivity probe in fresh deionized water daily. Sub-
stances which build up on the probe (e.g., suspended solids, etc.)
should be removed periodically according to the recommendations
provided by the manufacturer. Probe replatinization is also
required periodically; consult the instruction manual for the
proper method.
NOTE 3: An analyst pours the snow melt into the conductivity tubes after
completion of melting.
NOTE 4: See the conductivity flowchart (Figure B-l).
1) Unscrew both of the leads connecting the probe to the conductivity
meter to break the circuit and to prevent capacitance shunting between
calibrating resistors and probe.
2) Check the electronic function of the conductivity meter by plugging in
the resistors and by reading the conductivity at the appropriate ranges
(RES MULT/CONDMULT Switch).
Readings should be within 1 percent of the theoretical value. Record
the values in the logbook. If the values are not within 1 percent,
consult the guide provided by the manufacturer.
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ELECTRONICS
CHECK
WITH RESISTORS
VALUES
WITHIN IX OF
THEORETICAL
VALUES
7
CALIBRATION
PROCEDURE
TO CHECK
PROBE CELL
CONSTANT
CONSULT CONDUCTIVITY
METER OR CONDUCTIVITY
ROBE OPERATIONS MANUAL
AND NOTIFY SUPERVISOR
ACCEPTABL
VALUES
OR 147HScnf1CALIBRATIO
STANDARD (10%)
AND BLANK
QCCS(S)
WITHIN
10% ?
REMAKE AND
REMEASURE
SOLUTIONS
MEASURE
SAMPLES AND
RECORD IN LOGBOOK
FINAL CELL
CONSTANT CHECK
ANALYSES
COMPLETE
PREVIOUS SAMPLES (FROM LAST ACCEPTABLE QCCS)
MUST BE REANALYZED AFTER ACCEPTABLE QCCS
IS OBTAINED.
Figure B-l. Flowchart for conductivity.
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B,2 Reagents
B.2.1 Potassium Chloride Stock Solution (1 M KC1)
NOTE 1: Prepare as needed and refrigerate at 4.0°C.
NOTE 2: This stock solution is used to make the following standards:
147 "S cm'1 calibration standard,
14.7, 74, 147 ™S cm'1 QC standards.
NOTE 3: This stock solution should be made up in at least 1-L batches
to minimize weighing and dilution errors. The 1 M KC1 stock
solution has a theoretical electrical conductivity of 111,900
"S cm"1 at 25°C. This value should be verified by measuring
at least three 35-mL samples contained in 50-mL centrifuge
tubes.
1) Fill a clean 1-L volumetric flask with approximately 500 ml of
deionized water.
2) Weight 74.553 g of potassium chloride (KC1, ultrapure, dried for
2 hours at 105°C, and ampulated).
3) Completely dissolve the KC1 in deionized water, and dilute to the
1-L mark. Mix again thoroughly.
4) Store the stock solution in 500-mL bottles (not acid washed) which
have been rinsed three times with the 1 M KC1 solution. Label the
bottles "1 M KC1 Stock Solution," and refrigerate them at 4.0°C.
B.2.2 Calibration Blank
NOTE 1: Two centrifuge tubes (deionized water leached) are required for
each of the calibration, QCCS, and blank solutions. Label the
tubes accordingly, and designate one of each pair as the rinse.
NOTE 2: It cannot be assumed that the deionized water has a negligible
conductivity; therefore, the blank conductivity value is sub-
tracted from all standards.
NOTE 3: Be consistent in obtaining deionized water. Obtain deionized
water from the same reverse osmosis (RO) system from which all
standards are made.
1) Rinse two clean, labeled 50-mL centrifuge tubes three times with
deionized water, and then fill them with 30 to 40 mL deionized
water.
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B.2.3 Calibration Standard - 147 yS cm'1
NOTE: Prepare Daily
1) Fill a clean labeled 1-L volumetric flask with approximately 500 ml
of deionized water. Obtain a 50-mL disposable beaker, rinse the
beaker three times with 1 M KC1 stock solution (2 to 3 mL rinse),
and fill it with 5 to 10 mL of stock solution. Use this stock
solution to make calibration and QCCS solutions.
2) Use a calibrated 100 to 2,000 yL pipet (rinse pipet tip one time
with solution) to deliver 1.000 ml of stock solution to the 1-L
flask. Mix and dilute to 1-L mark, and mix again.
3) Rinse two clean, labeled 50-mL centrifuge tubes three times with
calibration standard, and pour 30 to 40 mL in each tube.
B.2.4 QC Standards - 14.7, 74, 174 yS cm'1
NOTE: Prepare daily.
1) Fill three clean, labeled 500-mL volumetric flasks each with
approximately 250 mL deionized water.
2) Use the beaker of 1 M KC1 stock solution (see Section B.2.3, Step 1)
to prepare the following solutions:
a) 14.7 yS cm'1. Use a calibrated 40- to 200-yL pipet to deliver
0.050 mL of stock solution to the volumetric flask labeled
"14.7 yS cm'1 QC Standard."
b) 74 yS cm'1. Use a calibrated 200- to 1,000-yL pipet to deliver
0.250 mL of stock solution to the volumetric flask labeled
"74 yS cm'1 QC Standard."
c) 147 yS cm'1. Use a calibrated 200- to 1,000-yL pipet to deliver
0.500 mL of stock solution to the volumetric flask labeled
"174 yS cm'1 QC Standard."
3) Mix and dilute each of the three standards to the 500-mL mark, and
mix them again.
4) Rinse each clean, labeled, centrifuge tube three times with the
appropriate standard (two centrifuge tubes for each standard, with
one tube designated as rinse). Fill each tube with its correspond-
ing standard (30 to 40 mL).
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5) Cap and store each standard, and all poured centrifuge tubes, at
room temperature.
B.3 Probe Calibration Check
NOTE 1: Turn conductivity meter "OFF" when removing probe from solution.
Follow the guidelines provided by the manufacturer for operation
of the conductivity bridge. The following procedure is modified
from the Beckman instruction manual.
NOTE 2: When measuring the conductivity of a solution, do not allow
the probe to touch the sides or the bottom of the plasticware.
Hold the cell upright. Be sure the vent holes are covered by
solution and that there are no air bubbles around the electrode.
NOTE 3: Rinse the probe in deionized water between each measurement.
NOTE 4: Always measure the blank first.
1) Connect the probe leads to the instrument at CELL binding posts 2 and
3.
2) Instrument settings: set MODE switch to COND/RES. position; set
FREQ switch to IKHZ bridge frequency; set CAP COARSE and CAP FINE
switches to zero.
3) Turn instrument on by actuating the ON-BAT check switch.
4) The conductivity measurements are made without temperature compensa-
tion when a water bath is employed. If not using a temperature bath,
consult the guide provided by the manufacturer for information about
alternative methods. Set the TEMP COMP switch to NONE, and adjust the
BALANCE control to give a counter reading of 1.05.
5) To balance the meter, set the COND MULT selector to 0.1 (the balance
meter pointer will deflect left of zero). Increase the multiplier
value step by step until the balance meter pointer deflects to the
right of zero, and then return the multiplier dial one step so that the
pointer deflects left again. Turn the BALANCE control until the
balance meter pointer reads zero. Set MODE selector to the CAP
setting. If the balance meter pointer deflects less than one major
division (five minor divisions) to either side of zero, the meter is
balanced. If the one division limit is exceeded, rotate the CAP
FINE switch to bring balance meter pointer toward zero. The CAP
COARSE switch is used if the CAP FINE switch fails to bring the
pointer toward zero (return CAP FINE to zero before using CAP COARSE).
Alternate the MODE switch between COND/RES and CAP as described
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above until COND/RES balance equals zero, and the CAP balance is
within one major division of zero.
6) To determine the conductivity value, place the probe into the con-
tainer with the solution to be measured and use the BALANCE control
to obtain the measured conductivity. The measured conductivity value
is the counter reading at balance multiplied by the COND MULT
setting.
Determine the value of the cell constant as follows:
147.0 yS cnr* Theoretical value of
calibration standard at 25°C
Measured value of Measured value
calibration standard - of blank at
at 25°C 25°C
B.4 QCCS Check
NOTE 1: Measure 14.7, 74, and 147 yS cm"1 QC standards after every 10
samples and at the end of the batch which follows the trailer
duplicate, and do the calculations as described below in Step 2.
Record all calculations in the logbook.
NOTE 2: If any QCCS solution is not in range, try repouring the standard.
If it still is not in range, remake the standard, and make a note
in the logbook under the comment section indicating exactly when
this occurred. Record the data.
1) Measure the conductance of the three QCCS solutions (prepared in Section
B.2.4).
2) Determine the conductivity values of QCCS solutions as described in
Section B.3, Step 6. Multiply the measured value (counter reading x
COND MULT setting) by the cell constant (Kc) value calculated in B.3,
Step 7. Subtract the measured value of the blank (counter reading x
COND MULT setting x Kc) to determine the actual value of the QCCS
solutions. The actual values must be within 10 percent of the
theoretical values.
B.5 Sample Measurement
1) Sample conductivity is determined, and measured conductivity is
calculated as follows: measured conductivity x COND MULT setting x
Kc. Do not subtract the temperature adjusted blank value from the
result. Record all computations in the logbook.
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2) The trailer duplicate is measured last. The trailer duplicate values
must be within 10 percent of each other.
B.7 Clean-up
1) Make sure that the conductivity meter is in the "OFF" position.
Place the probe in fresh deionized water, and cover the container with
Parafilm.
2) Clean all glassware used for the preparation of the standard solutions
by rinsing them three times with deionized water.
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Appendix C
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APPENDIX C
LABORATORY pH DETERMINATION (OPEN SYSTEM)
(modified from Chaloud et al., 1986, unpublished document)
C.O INTRODUCTION
The pH of an aquatic environment is regulated by both abiotic (inorganic
C02 equilibria, surficial geology, and anthropogenic pollutants) and biotic
(photosynthesis, respiration, and decomposition) factors. A pH balance is
usually maintained by the presence of buffering reactions within the aquatic
system. If this balance is shifted, both chemical and biotic repercussions
may result.
In the processing laboratory, pH is measured with Orion Model 611 pH/
millivolt meters and Orion Ross combination electrodes. Measurements of
snow samples are made with an open system because snow samples are assumed
to be at equilibrium with respect to C02 gas transfer between the water
sample and the laboratory atmosphere.
The pH is defined as the negative logarithm of the activity of hydrogen
ions (H+). The H+ activity is a measure of the "effective" concentration
of hydrogen ions in solution, and it is always equal to or less than the
true concentration of hydrogen ions in solution. Values usually range
from pH 1 to pH 14, with pH 1 being most acidic, pH 7 neutral (at 25°C).
and pH 14 most alkaline. Each pH unit represents a tenfold change in H+
activity. For example, a pH 4 solution is 10 times as acidic as a pH 5
solution.
When the pH of a sample solution is measured, the hydrogen ions come into
equilibrium with the ion exchange surface (glass) of a calibrated pH elec-
trode which creates an electrical potential. This voltage difference is
measured by the pH meter in millivolts and is then converted and displayed
as pH units.
C.I Reagents
NOTE 1: See the flowcharts for pH determinations (Figures C-l and C-2).
NOTE 2: Use deionized water obtained from the same RO system throughout
all reagent preparation.
C.I.I pH 4.00 QCCS Solution (0.0001 N H2S04)
NOTE: pH 4.00 QCCS must be prepared daily.
1) Fill a clean 1-L volumetric flask with approximately 500 mL deionized
water.
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INITIAL
STANDARDIZATION
AND CHECK
CHECK QCCS
STANDARD
YES
MEASURE pH
OF
SAMPLES
YES
ENOUGH
OLUME REMAININ
N PREVIOUSLY ANALYZE
SAMPLES TO
REANALYZ
7
QCCS
WITHIN 0.1 pH
UNITS
MORE
SAMPLES
RECORD QCCS VALUE IN
LOGBOOK AND NOTE
SAMPLE ID NUMBERS
ASSOCIATED WITH
UNACCEPTABLE QCCS.
I PREVIOUS SAMPLES (FROM LAST ACCEPTABLE QCCS)
MUST BE REANALYZED AFTER ACCEPTABLE QCCS IS
OBTAINED.
Figure C-l. Flowchart for laboratory pH determination.
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UNACCEPTABLE
QCCS VALUE
REANALYZE
WITH SAME QCCS
IN NEW CONTAINER
ACCEPTABLE
VALUE
+O.l pH UNITS)
REMAKE QCCS
AND
REANALYZE
PROCEED
WITH
SAMPLE ANALYSIS
(Figure C-l)
YES
CHECK
METER
STANDARDIZATION
WITH
BUFFER SOLUTIONS
RESTANDARDIZE
USING
BUFFERS
CHECK
TEMPERATURE
CALIBRATION
RECALIBRATE
FOR
TEMPERATURE
CONSULT
OPERATIONS
MANUAL AND
NOTIFY SUPERVISOR
©PREVIOUS SAMPLES (FROM LAST ACCEPTABLE
QCCS) MUST BE REANALYZED AFTER
ACCEPTABLE QCCS IS OBTAINED.
Figure C-2. Troubleshooting flowchart for pH determination.
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2) Pour approximately 5 ml 0.1 N ^804 into a 50-mL disposable beaker.
3) Using a calibrated 200- to 1,000-yL pipet, add 1.000 ml of 0.1 N
to the volumetric flask. Stopper the flask, and mix the solution
thoroughly by inversion. Dilute to the 1-L mark with deionized
water to produce 0.0001 N ^804. Mix the solution again, and label
the flask "QCCS-pH 4.00."
C.I.2 NBS-Traceable Buffers
Two commercially prepared buffer solutions (pH 4.00 and pH 7.00) are
required.
C.I.3 Dilute pH 7.00 Buffer Intermeter Comparability Solution
NOTE: The dilute pH 7.00 buffer must be prepared daily; the theoretical
pH value is 7.31 ± 0.07.
1) Fill a clean, labeled, 1-L volumetric flask with approximately
500 ml deionized water.
2) Tare the balance containing a 50-mL beaker, and measure 5.000 ±
0.001 g of NBS pH 7.00 buffer. Add the volume to the 1-L flask.
Stopper the flask, and mix the solution thoroughly by inversion.
Dilute to the 1-L mark with deionized water. Mix the solution
again.
C.2 Instrument Preparation
NOTE 1: It is mandatory that all personnel operating the pH meter be
familiar with its operating procedures before using the instrument.
NOTE 2: Always leave the pH meter on "STD BY" when the electrode is removed
from a solution, when rinsing the electrode, or when the meter is
not in use.
1) Plug in the instrument, and verify that the control knob is on "STD
BY." Allow at least 30 minutes for instrument warm-up prior to use.
2) Connect the Orion Ross combination electrode to the meter. Consult the
pH electrode manual for the proper procedure.
3) Verify that the level of reference filling solution (3 M KC1) in the
electrode is just below the fill hole and that the fill hole is uncovered
during measurement (slide the plastic sleeve down).
4) Calibrate the meter for temperature weekly by using a two-point stand-
ardization (one point at approximately 5°C to 10°C and the other point
at room temperature).
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a) Room Temperature: Place the electrode and an NBS thermometer into
deionized water which is at room temperature. Swirl the electrode
for 5 to 10 seconds.
b) Turn the knob on the meter to "TEMP." With a small screw driver,
adjust the "TEMP ADJ" screw on back of pH meter until the display
corresponds to the temperature reading of the thermometer.
c) Cold Temperature: Place the probe and the NBS thermometer into a
250-mL beaker containing cold deionized water (5 to 10°C). Repeat
Step b by adjusting the display with the "TEMP SLOPE" screw on the
back of the meter.
d) Continue Steps a through c until no further adjustments are
necessary, and record all values in the logbook.
C.3 Daily Instrument Standardization
C.3.1 Temperature Standardization
1) Check the calibration of the temperature meters daily with a beaker
of room temperature deionized water and with an NBS thermometer as
described in Section C.2, Steps 4a and 4b.
2) If the meter reading differs from the NBS thermometer by more than
1.0°C, adjust the display to that of the thermometer by using the
"TEMP ADJ" screw.
C.3.2 Standardization with NBS-Traceable Buffers
NOTE: The pH meter is standardized daily with two NBS pH buffers (pH
7.00 and pH 4.00).
1) Pour fresh pH 7.00 and pH 4.00 buffer solutions into labeled 50-mL
beakers (one "RINSE," one "CALIBRATION," and one "CHECK" beaker for
each buffer). Rinse all beakers three times, and fill them with
the appropriate buffer solutions.
2) Rinse the electrode with deionized water. Place the electrode into
the pH 7.00 "RINSE" beaker, and swirl the beaker for 30 seconds.
Place the electrode into the "CALIBRATION" beaker, turn the knob to
"pH," swirl the beaker for 30-60 seconds (or until the pH reading
is stable), and read the value on the display. Consult the
pH-temperature chart, Table C-l. Use the "CALIBRATE" knob to adjust
the pH reading on the meter to the theoretical pH of the buffer
solution at the appropriate temperature.
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TABLE C-l. pH VALUES OF BUFFERS AT VARIOUS TEMPERATURES
(from Orion Research Instruction Manual, 1983).
NBS buffer, Temperature
nominal value
at 25°C 0°C 5°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C 80°C 90°C
1.68 1.67 1.67 1.67 1.67 1.68 1.69 1.71 1.72 1.74 1.77 1.79
3.78 3.86 3.84 3.82 3.79 3.77 3.75 3.75
4.01 4.00 4.00 4.00 4.00 4.02 4.03 4.06 4.08 4.13 4.16 4.21
6.86 6.98 6.95 6.92 6.87 6.85 6.84 6.83 6.84 6.85 6.86 6.88
7.00* 7.11 7.08 7.06 7.01 6.98 6,97 6.97
7.41 7.53 7.50 7.47 7.43 7.40 7.38 7.37
9.18 9.46 9.40 9.33 9.23 9.14 9.07 9.01 8.96 8.92 8.89 8.85
10.01 10.32 10.25 10.18 10.06 9.97 9.89 9.83
*Non-NBS Phosphate buffer
3) Repeat Step 2 for pH 4.00 buffer adjust the "% SLOPE" knob to adjust
the pH reading.
4) Repeat Steps 2 and 3 until both the pH 7.00 and the pH 4.00 buffers
agree with the theoretical pH of the buffer solution at the appropriate
temperature.
5) Check the standardization with the buffer solutions in the "CHECK"
beakers. If the values differ by more than ±0.03 units from the
theoretical value, repeat the standardization process (see Section
C.3.2, Steps 1-5). When the meter standardization is acceptable,
record the pH and temperature readings for each buffer solution in
the pH logbook.
C.4 Sample Analysis
NOTE 1: At the beginning of each survey, a primary meter must be desig-
nated. This meter is to be used when only one meter is necessary
to analyze a batch.
NOTE 2: If the batch size is equal to or greater than 20 samples, a
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secondary meter may be used, and additional procedures are
involved (see Section C.5).
NOTE 3: pH is not measured in field blanks, lab blanks, or lab audits.
NOTE 4: Allow samples to warm to room temperature before measuring pH.
C.4.1 Initial QCCS Check
1) Rinse and fill two beakers with pH 4.00 QCCS.
2) Rinse the electrode by swirling it in the rinse beaker for 15 to 30
seconds.
3) Insert electrode into the QCCS beaker.
4) Turn the knob to pH and start the stopwatch. Record the initial pH,
temperature, and time (0:00) in the pH logbook.
5) Wait until the reading seems fairly consistent, and then note the
time and pH values on a loose sheet of paper. If the pH reading
does not vary by more than 0.02 pH units in one direction throughout
a 1-minute interval, the reading is considered stable. Record the
stable pH and temperature readings, and the total elapsed time in
the logbook.
C.4.2 Sample Measurement
1) Rinse the electrode copiously with deionized water, and then rinse
it in the sample tube marked "Rinse."
2) Determine sample pH by following the instructions in Section C.4.1.
C.4.3 Routine QCCS Determination
NOTE: The pH 4.00 QCCS is always analyzed at the beginning of a batch
and at the end of a batch. The QCCS is also analyzed at intervals
within the batch; the intervals depend on the batch size and on
the number of pH meters used. The criteria necessary for deter-
mining when a QCCS should be analyzed are listed below:
0 If the batch is less than 20 samples, use only the meter designated
as the primary meter. Run a QCCS in the middle of the batch.
0 If the batch is less than or equal to 5 samples, a QCCS does not
need to be analyzed mid-batch.
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0 If the batch is greater than or equal to 20 samples and if one pH
meter is used, analyze a QCCS after every 10 samples.
1) Measure and record the QCCS by following the instructions in Section
C.4.1.
2) If the measured QCCS pH is acceptable (pH 4.00 ± 0.10), proceed with
routine sample pH determinations.
3) If the QCCS pH is not acceptable, follow the steps below until an
acceptable value is obtained.
a) Repour the pH 4.00 QCCS into a beaker and reanalyze.
b) Remake the pH 4.00 QCCS (see Section C.I.I), and reanalyze the
QCCS.
c) Repeat the standardization steps (see Section C.3), and reanalyze
the QCCS.
d) If an acceptable reading is still not obtained, consult the lab-
oratory supervisor.
4) If the pH meter requires recalibration to obtain an acceptable QCCS
reading, make a notation in the pH logbook. Determine which samples
must be reanalyzed.
a) Reanalyze all samples back to the last acceptable QCCS.
C.5 Data Reporting
Trailer Duplicate (TO) Pair. One sample is analyzed in duplicate. The pH
value of the duplicate sample must be within 0.1 pH unit of the routine
sample value. If the value is outside the acceptable range, record the
values and notify the laboratory supervisor for the appropriate procedure.
C.6 Instrument Care and Clean-up
NOTE: Read the instructions provided by the manufacturer for the main-
tenance of the pH meter and electrode.
C.6.1 Daily Clean-up
1) Copiously rinse the electrode and glassware with deionized water.
2) Cover the fillhole of the electrode with the plastic sleeve, and
store the electrode in 3 M KC1.
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3) Make sure the meter is on "STD BY."
C.6.2 Weekly Maintenance
1) Drain the 3 M KC1 filling solution from the electrode by using a
disposable pi pet with Teflon tubing attached.
2) Refill the electrode chamber with the 3 M KC1 filling solution, and
rinse it by inverting the electrode. Drain the solution as in Step 1,
3) Refill the electrode with the filling solution to just below the
fill hole.
4) Gently spin the electrode overhead by the leader for approximately
1 minute to remove any air bubbles. Be careful to stand clear of
any obstacles when swinging the electrode.
C.6.3 pH Meter Electronic Checkout
NOTE: This procedure should be performed whenever a new pH meter is
set up or when calibration problems occur.
1) Connect the shorting strap by following the instructions in Orion pH
meter manual.
2) Turn the "TEMP ADJ" and "TEMP SLOPE" screws fully counterclockwise
and record the display pH value (turn knob to "pH" position).
3) Turn the "TEMP SLOPE" screw 7.5 turns clockwise, and record the
display pH value. The difference between the "TEMP SLOPE" value in
Step 2 and Step 3 should be between 7.0 and 15.0.
4) Turn the "TEMP ADJ" screw until a value between 50.0 ± 0.1 appears
on display.
5) Press the test button. A value of 42.2 ± 2.0 should appear on
display when the knob is in the "TEMP" positon. If this value is
not displayed, keep depressing the test button and use the "TEMP
SLOPE" screw to adjust the reading to 40.0 ± 0.1. Release the test
button and use the "TEMP ADJ" screw to obtain reading of 50.0 ± 0.1.
Press the test button again. The reading should be 42.2 ± 2.0.
Repeat this procedure several times if the value is not in range.
6) If the meter still will not calibrate, consult the laboratory
supervisor.
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C.6.4 Electrode Etching Procedure
CAUTION: Use Extreme Caution when using the NaOH pellets. Be sure to
wear gloves, protective glasses, and a rubber apron.
NOTE 1: If the electrode response is sluggish or if the instrument
cannot be standardized, the following procedure is recommended
for cleaning the ceramic junction of the electrode and for
improving the electrode response time. Consult the laboratory
supervisor before performing this procedure.
NOTE 2: Etch electrodes in groups of three when possible. Prepare a
fresh NaOH solution for each group of electrodes.
1) Drain the filling solution from the electrode.
2) Rinse the filling chamber with deionized water, and drain it.
3) Refill the chamber with deionized water.
4) Prepare a 50 percent (weight to volume) NaOH solution by slowly
adding 30 g NaOH to 30 ml deionized water.
5) Gently stir the solution with up to three electrodes to dissolve the
NaOH. The solution will be very hot and may boil and splatter, and
CAUTION MUST BE USED.
6) Stir the solution for an additional 2 minutes with the electrodes.
7) Rinse the electrodes with deionized water.
8) Rinse the electrodes in pH 7.00 buffer for 2 minutes.
9) Drain the deionized water from the filling chambers.
10) Refill each electrode with 3 M KC1 , agitate the electrodes, and
drain the chambers.
11) Refill the chambers once more with 3 M KC1 , and spin each electrode
from the leader to remove air bubbles.
12) Soak electrode in pH 7 buffer for 24 hours prior to checking
performance.
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Appendix D
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Page 1 of 7
APPENDIX D
FILTRATION, PRESERVATION, AND SHIPPING
(Modified from Chaloud et al., 1986, unpublished document)
D.O INTRODUCTION
Samples are filtered to remove the biotic and abiotic particles which
exceed 0.45 urn in size. This procedure is necessary to prevent changes in
particular chemical parameters prior to processing at the analytical labora-
tory. The parameter being measured at the analytical laboratory dictates
what the preparation and preservation procedure performed by the processing
laboratory will be in order to ensure sample stability until analysis is
complete. Aliquot preparation takes priority in the laboratory in that
the samples must be processed after completion of melting but before
sample temperature exceeds 4°G.
D.I Filtered Aliquots - Acid-Rinsed Units
(Aliquots 1 and 4)
D.I.I Filtration Unit Assembly
NOTE 1: There are two 4-apparatus filtration set-ups in each clean air
station.
NOTE 2: A slight positive (blowing into the laboratory) air flow should
be maintained in the clean air station. Air flow can be regu-
lated by turning the adjustment screw located centrally above
the sash. Check for positive air flow by taping a Kimwipe
strip to the bottom of the glass window.
1) Four filtration units in a series constitute a set-up. Counting
inward from the side of the hood, the first three units are acid-
rinsed. The fourth, in the center of the hood and isolated by a
Plexiglas divider, is not acid-rinsed. This unit is also identified
by the presence of a strip of blue tape.
2) Attach the vacuum line from the vacuum pump via a waste filter flask
to the outlet on the first filtration base. Turn on the vacuum.
Adjust the vacuum pump to 10 to 12 inches Hg.
CAUTION: (to ncrt exceed 12 inches Hg under any circumstances.
Be sure that the waste flask remains upright and that it is emptied
on a regular basis.
3) Two sets of Teflon forceps are needed. One set is acid-rinsed.
Label one pair of this set "ACID-CLEAN" and the other "ACID-DIRTY."
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Mark these with red tape. One set is not acid-rinsed. Label one
pair of this set "NONACID-CLEAN" and the other "NONACIO-DIRTY." Mark
these with blue tape.
D.I.2 Between Sample Rinsing - Acid-Rinsed Units
NOTE: Each filter apparatus must be rinsed completely before a new
sample is processed. See Figure D-l for a diagram of the
filtration unit.
1) Place a 250-mL plastic beaker (for waste) under each filter funnel.
2) Rinse the filter funnel once with deionized water from a 1-L wash
bottle. Be sure water flows evenly over all interior surfaces of
the filter cup; turn the cup one complete revolution while rinsing
the sides.
3) Rinse the filter funnel once with 5 percent HN03 (Baker Instra-
Analyzed grade) from 1-L wash bottle. Turn the cup one complete
revolution while rinsing the sides.
4) Rinse the filter funnel three times with deionized water from a 1-L
wash bottle. Turn the cup one complete revolution for each rinse,
and allow the water to drain completely.
D.I.3 Filter Rinsing Procedure - Acid-Rinsed Units
NOTE 1: The 0.45 ym membrane filter should be replaced before a new
sample is to be filtered. Be sure that the filter is centered
and that it lies smoothly on the filter screen with no tears.
NOTE 2: Make sure the blue filter separators are removed before placing
the filter on the screen. Do not touch the filter to any object
other than clean Teflon forceps or the filter screen. If the
filter does touch another object, discard the filter and obtain
a new one.
NOTE 3: Empty the waste beaker that is under the filtration apparatus
into a second waste beaker to be dumped outside the hood.
Never remove the apparatus waste beaker from the clean air
station.
1) Unscrew the filter cup from the filter holder. Make sure that it
separates properly and that the 0-rings are secure and in place.
2) Lift the cup. Using clean, acid-rinsed Teflon forceps, place a 0.45
urn membrane filter onto the screen. Moisten the filter with deion-
ized water (from wash bottle), and apply the vacuum to seal the
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FUNNEL
CHAMBER^
CAP
CUP
SCREEN
O-RINGS
RING
HOLDER
STOPPER
BASE-4
HOSE
Figure D-l. Filtration apparatus.
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filter to the screen. Be sure that the filter is centered and that
it lies smoothly with no tears.
3) Replace the cup onto the holder without disturbing the filter.
Tighten the ring securely. If the ring is not properly tightened,
it may leak while filtering. If this happens, obtain a new aliquot
bottle of the same type, and reprocess the aliquot.
4) Rinse the filter with 5 ml of deionized water, and follow that with
a 5-mL rinse of 5 percent HN03, and follow that with two 5-mL rinses
with deionized water. A third rinse with deionized water should
cover the sides of the cup as well as the filter.
5) Shut off the vacuum. Break the seal, and thoroughly rinse the
filter funnel tip with deionized water.
D.I.4 Sample Filtration - Acid-Rinsed Units
NOTE 1: The cap is kept on the aliquot bottles until the bottle is
placed under the funnel to avoid any possible contamination from
the chamber.
NOTE 2: If the Cubitainer cap (or its white paper liner) is dropped at
any time, rinse it one time with deionized water and one time
with sample and then continue processing.
NOTE 3: Keep the hood area clean. Wipe up spills after they occur.
1) Agitate the Cubitainer. Pour no more than 10 ml of sample into the
filter cup.
2) Turn on the vacuum, and filter the sample into the waste beaker.
Turn off the vacuum.
3) Lift the chamber and remove the waste beaker. Empty the beaker, and
place it behind the apparatus out of the way. Loosen the lid of the
Aliquot 1 bottle. Lift the chamber, and set the Aliquot 1 bottle on
the base. Remove the cap, and lower the chamber back onto the base.
Set the cap upright next to apparatus in a clean spot.
4) Agitate the Cubitainer. Pour no more than 10 mL of sample into the
filter cup.
5) Turn on the vacuum. Filter the sample into the Aliquot 1 bottle,
and turn off the vacuum.
6) Lift the chamber, and replace the cap on the Aliquot 1 bottle. Remove
the bottle, and tighten down the cap. Rinse the bottle thoroughly by
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shaking and rotating. Pour the rinse sample into the waste beaker.
Loosen the cap, lift the chamber, and replace the bottle under the
funnel. Remove the cap, and set the chamber on its base.
7) Agitate the Cubitainer. Pour 200 ml of the sample into the filter
cup. Apply vacuum pressure, and filter the sample into the Aliquot 1
bottle. Turn off the vacuum.
8) Only the Aliquot 1 bottle is used to collect the filtered sample.
Aliquot 4 is poured from Aliquot 1.
D.2 Filtered Aliquots - Units Which are not Acid-Rinsed
(Aliquots 2 and 3)
NOTE 1: Use the filtration apparatus which is not acid-rinsed to filter
Aliquot 2 and 3. All components of this unit (except the base)
should be soaked in deionized water for 48 hours prior to the
initial set-up, and each component should be labeled with blue
tape.
NOTE 2: If any part of the apparatus is contaminated by acid, replace
the entire apparatus with a clean one. Soak the dirty one in
deionized water for 48 hours.
1) Follow the same set-up and rinsing procedures described in Section
D.I.2 through D.I.4. However, eliminate the 5 percent HNO^ rinse in
all steps, rinsing three times with deionized water only.
2) Aliquot 2 is poured from aliquot 3.
3) The aliquot 3 bottle should be filled to the brim and should be capped
tightly so that no headspace exists. To break the pressure in the
chamber and to avoid losing sample, carefully insert a gloved finger
between the stopper and the funnel.
D.3 Filter Changing Procedure
1) If it is necessary to change the filter before filling all aliquots
from one sample because the filter has become clogged, use the
following procedure:
a) Shut off the vacuum. Lift the chamber, cap the aliquot bottle,
and remove it; replace it with the waste beaker.
b) Unscrew the filter cup, remove the dirty filter with the "DIRTY"
forceps, and replace it with a clean filter by using the "CLEAN"
forceps.
c) For aliquots prepared with the acid-rinsed units, rinse the
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filter by following the instructions in Section D.I.3. For
Aliquots 2 and 3 (which make use of the filtration unit which is
not acid rinsed), follow the same procedure except eliminate the
5 percent HNCh wash; instead, rinse three times with deionized
water.
D.5 Preservation
NOTE 1: Prepare and attach the appropriate labels to the aliquot bottles
prior to sample arrival; the label color reflects the appropriate
preservation procedure.
Acid used for
Aliquot No. Label Color Preservation
1 Pink HN(h
2 Blue HgCl2
3 White None
4 Yellow H2S04
1) Use two 40- to 200-yL micropipets, one labeled for nitric acid
(red tape) and one labeled for sulfuric acid (yellow tape). Add
100 yL of the appropriate Ultrex acid to the sample as follows:
Aliquot 1 is preserved with Ultrex HN03.
Aliquot 4 is preserved with Ultrex H2S04.
2) After the acid is added, tighten the caps and mix the solution
thoroughly.
3) Loosen the aliquot bottle caps, and using a fresh capillary tube for
each bottle, collect and place a drop of preserved sample on Whatman
pH paper (type CS, 1.8 to 3.8). The pH should be less than 2.
4) It may be necessary to add more than 100 yL of acid for the pH to be
less than 2. If this situation occurs, continue adding the appropriate
acid in 100-yL increments until the pH is less than 2, using a new
capillary tube each time the pH is tested.
5) Write the total amount of acid added to the sample on the aliquot
label and in the logbook.
6) Dissolve 50 g HgCl2 in 1 L of deionized water.
CAUTION: HgCl2 is hazardous. Wear gloves when weighing HgCl2.
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7) Use one 40- to 200-yL pi pet to add 100 yL 5 percent HgCl2 to aliquot 2.
Cap the aliquot tightly, and indicate amount of 5 percent HgCl2 on the
aliquot label and in the logbook.
D.6 Preparation of Aliquots for Shipping
1) Refrigerate all aliquots for at least 1 hour at 4°C before shipping.
Check that all labels are correct, and tighten the caps firmly. Tape
each cap in a clockwise direction with electrical tape. Place each
each aliquot or centrifuge tube to be shipped in an individual plastic
bag, and tie them with a twist-tie.
2) Place each set of aliquot bottles into a 1-pint Ziploc bag. Face the
labels in the same direction for easy sample identification. Remove
the air from the bag, seal it, and place the bag in the refrigerator
or directly into the prepared shipping coolers.
D.7 Shipping Instructions
NOTE 1: Samples are delivered to the analytical laboratory the day before
analysis.
NOTE 2: Styrofoam containers are used to ship the aliquots. Be sure that
the containers are sturdy.
1) Place eight frozen gel packs into each large shipping container,
lining the inside of the container. Use four gel packs for the smaller
shipping containers.
2) Place 12 sets of aliquots in a container. If there are less than 12
sets to be shipped, fill the excess space with gel packs or newspaper.
3) A four part shipping form is completed by the laboratory coordinator,
and it contains all aliquot information for the batch. The pink and
gold copies are placed inside a Ziploc bag and are placed inside the
shipping box on the cooler lid. The yellow copy is sent to QA per-
sonnel. The original (white) is retained in the processing laboratory.
4) Samples are hand delivered to the analytical laboratory.
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APPENDIX E
DETERMINATION OF AMMONIUM BY FLOW INJECTION ANALYSIS
E.O Scope and Application
This method covers the determination of ammonium in the range of 0.01 to
0.150 mg/L NH4+. This range is for photometric measurements made at 630
to 660 nm in a 10-mm tubular flow cell. Higher concentrations can be
determined by sample dilution. Approximately 60 samples per hour can be
analyzed.
E.I Summary of Method
Alkaline phenol and hypochlorite react with ammonium to form an amount
of indophenol blue that is proportional to the ammonium concentration.
The blue color formed is intensified with sodium nitroprusside.
E.2 Interferences
Calcium and magnesium ions may be present in concentration sufficient to
precipitate during the analysis. A 5 percent EDTA solution is used to
prevent the precipitation of calcium and magnesium ions.
Sample turbidity may interfere with this method. Turbidity is removed
by filtration at the processing laboratory. Sample color that absorbs
in the photometric range used also interferes.
E.3 Safety
The calibration standards, sample types, and most reagents used in this
method pose no hazard to the analyst. Use protective clothing (lab coat
and gloves) and safety glasses when preparing reagents.
E.4 Apparatus and Equipment
Tecator FIAstar flow injection analyzer or equivalent consisting of:
Sampler
Analytical manifold with 200-yl sample loop
In-1ine heater
Colorimeter equipped with a 10-mm flow cell
Printer
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E.5 Reagents and Consumable Materials
Water—Water must meet the specifications for Type I Reagent Water given
in ASTM D 1193 (ASTM, 1984).
Acidified water—To a 2-1 volumetric flask containing 1500 ml water,
pipet 0.70 ml of concentrated H2S04 (Ultrex or equivalent). Dilute to
2 L and mix.
Sodium Phenate Solution—Using a 400-mL Griffen beaker, dissolve 20.7 g
phenol in 200 ml water. Add 8 g NaOH by stirring occasionally. Add water
to the 250-mL mark and stir. The final solution should be a light amber
color. Pour the solution into a 250-mL amber plastic bottle and store the
bottle in a hood until used.
Sodium Hypochlorite Solution—Using a 500-mL Erlenmeyer flask, dilute
100 ml of a commercial bleach solution (Chlorox or equivalent, 5 percent
NaOCl, minimum) with 100 mL water.
Disodium Ethylenediaminetetraacetate Acid (EDTA)—Dissolve 50 g EDTA
(disodium salt) and approximately 6 pellets of NaOH in 1 L water and store
the solution in a 1 L plastic bottle. To facilitate solution, use of a
mechanical shaker is recommended.
Sodium Nitroprusside—Dissolve 0.5 g sodium nitroprusside in 1 L water.
Store the solution in a 1-L plastic bottle.
Ammonium Stock Solution (1000 mg/L NH^"1") —In a 1-L volumetric flask,
dissolve 3.6624 g (NH/) 2SO* (dried at 105°C for 2 hours) in water, add
0.35 mL concentrated H2S04 (Ultrex or equivalent), and dilute the solution
to 1 L. Store it in a 1-L plastic bottle.
Standard Solutions (10 mg/L NH^"1") —In a volumetric flask, dilute 1 mL of
ammonium stock solution to 100 mL with acidified water.
Working Standards—Using the standard solution and diluting with acidified
water, prepare the following standards in 100-mL volumetric flasks:
NH4+ (mg/L) mL standard solution /100 mL
0.010 0.100
0.025 0.250
0.050 0.500
0.100 1.00
0.150 1.50
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E.6 Sample Collection, Preservation, and Storage
Samples are filtered and preserved (addition of ^04 to pH <2) in the
processing laboratory. The samples must be stored at 4°C when not in use.
E.7 Calibration and Standardization
Analyze the series of standards described above.
The calibration curve is calculated by the instrument. Follow the instruc-
tions provided by the manufacturer for creating calibration curves.
E.8 Quality Control
The following special sample types are used for quality control. A batch
is defined herein as the number of samples, excluding the standards and QC
samples, accommodated by the analyzer at any one time. For the FIAstar,
this is approximately 25 samples.
Quality control check standard (QCCS) is a standard having a concentration
of approximately the midpoint of the calibration range. Use 0.100 ppm
concentration for this procedure. The QCCS is analyzed after the calibra-
tion standards (before any samples), then after every tenth sample and as
the last sample of any batch of samples. The QCCS must be within the
prescribed accuracy limits (within 10 percent of actual concentration).
If a QCCS is not within the prescribed limit, all samples analyzed since
the last good QCCS are reanalyzed. Prepare the QCCS from an ammonium
stock made of ammonium sulfate from a different lot than that used for
the ammonium stock used to prepare the standards.
Detection limit standard (DL) is a standard 2 to 5 times the required
detection limit. Use a 0.050 ppm solution for this standard. The DL
is analyzed after the first QCCS and before the first sample and must be
within the prescribed accuracy limit (within 20 percent of actual concen-
tration) .
A blank is run once per batch of samples. The blank is a sample of the
acidified water used to make up the standards.
External standards from the National Bureau of Standards or the EPA are
analyzed twice in any batch of samples.
An internal standard (IS) or calibration standard is run three times in
a batch, the first time before the first sample. The additional IS's are
spaced at approximately equal intervals in the sample batch. The IS
assists in compensating for any drift that may occur during the analysis.
One sample in any batch is analyzed in duplicate.
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E.9 Procedure
Turn the power to the analyzer and to data station on for at least 30
minutes before use.
Set up the ammonium manifold, and pump water through the manifold and lines
while making the standards.
Prepare the reagents, standards, and QC samples.
Check the photometer reference and sample dark current. Consult the owners
manual for specific instructions for this adjustment.
Load the standards, QC, and samples in the sample trays.
Enter the required information about the standards into the analyzer.
Begin the analysis.
Dilute any samples which are outside the calibration range.
E.10 Calculations
The concentrations of the samples are computed by the data station.
E.ll Precision and Accuracy
In a single laboratory (LEMSCO-Las Vegas) with standards at concentra-
tions of 0.125. 0.104 (EPA reference sample WP486 No. 1), 0.100, and
0.050 mg/L NH, , the average %RSD was 5.65 (Pia, personal communication,
1987). *
Bias for the same samples were 102, 106, 105, 106, respectively.
E.12 References
American Society for Testing and Materials, 1984. Annual Book of ASTM
Standards, Vol. 11.01, Standard Specifications for Reagent Water,
D 1193-77 (reapproved 1983). ASTM, Philadephia, Pennsylvania.
Pi a, S. H., 1987. Personal Communication.
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APPENDIX F
DETERMINATION OF DISSOLVED METALS (Ca and Mg) BY INDUCTIVELY
COUPLED PLASMA EMISSION SPECTROSCOPY
(modified from Hi 11 man et al., 1986)
F.O Scope and Application
This method is applicable to the determination of dissolved Ca and Mg in
natural surface waters and precipitation.
Table F-l lists the recommended wavelengths and typical estimated instru-
mental detection limits using conventional pneumatic nebulization for the
specified elements. Actual working detection limits are sample-dependent,
and as the sample matrix varies, these concentrations may also vary.
Because of the differences among makes and models of satisfactory instru-
ments, no detailed instrumental operating instructions can be provided.
Instead, the analyst is referred to the instructions provided by the
manufacturer of the particular instrument.
F.I Summary of Method
The method describes a technique for the simultaneous or sequential
determination of Ca and Mg in natural surface waters and precipitation
samples. The method is based on the measurement of atomic emission by
optical spectroscopy. Samples are nebulized to produce an aerosol. The
aerosol is transported by an argon carrier stream to an inductively
coupled argon plasma (ICP), which is produced by a radio frequency (RF)
generator. In the plasma (which is at a temperature of 6,000 to 10,000°K),
the analytes in the aerosol are atomized, ionized, and excited. The
excited ions and atoms emit light at their characteristic wavelengths.
The spectra from all analytes are dispersed by a grating spectrometer, and
the intensities of the lines are monitored by photomultiplier tubes. The
photocurrents from the photomultiplier tubes are processed by a computer
system. The signal is proportional to the analyte concentration and is
calibrated by analyzing a series of standards (U.S. EPA, 1983; Fassel ,
1982).
A background correction technique is required to compensate for variable
background contribution to the determination of trace elements. Back-
ground must be measured adjacent to analyte lines during sample analysis.
The position selected for the background intensity measurement, on
either or both sides of the analytical line, will be determined by the
complexity of the spectrum adjacent to the analyte line. The position
used must be free of spectral interference and must reflect the same
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TABLE F-l. RECOMMENDED WAVELENGTHS3 AND ESTIMATED INSTRUMENTAL
DETECTION LIMITS
Element Wavelength (nm) Estimated detection limit (ug/L)b
Calcium 317.933 2-3
Magnesium 279.079 2-3
aThe wavelengths listed are recommended because of their sensitivity and
overall acceptance. Other wavelengths may be substituted if they can provide
the needed sensitivity and are treated with the same corrective techniques for
spectral interference.
bThe estimated instrumental detection limits as shown are taken from Fassel ,
1982. They are given as a guide for an instrumental limit. The actual method
detection limits are sample-dependent and may vary as the sample matrix varies.
change in background intensity as occurs at the analyte wavelength
measured. Generally, each instrument has different background handling
capabilities. The instrument operating manual should be consulted for
guidance.
The possibility of additional interferences named in Section F.2 should
also be recognized, and appropriate corrections should be made.
F.2 Interferences
Several types of interference effects may contribute to inaccuracies in
the determination of trace elements. They are summarized in Sections
F.2.1 through F.2.3.
F.2.1 Spectral Interferences
Spectral interferences can be categorized as (1) overlap of a spectral
line from another element; (2) unresolved overlap of molecular band
spectra; (3) background contribution from continuous or recombination
phenomena; and (4) background contribution from stray light from the
line emission of high-concentration elements. The first of these
effects can be compensated by utilizing a computer correction of the
raw data, requiring the monitoring and measurement of the interfering
element. The second effect may require selection of an alternate wave-
length. The third and fourth effects can usually be compensated by a
background correction adjacent to the analyte line. In addition, users
of simultaneous multi-element instrumentation must assume the responsi-
bility of verifying the absence of spectral interference from an element
that could occur in a sample but for which there is no channel in the
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instrument array. Listed in Table F-2 are some interference effects
for the recommended wavelengths given in Table F-l. The interference
information is expressed as analyte concentration eqivalents (i.e.,
false analyte concentrations) arising from 100 mg/L of the interfering
element. The values in the table are only approximate and should be
used as a guide for determining potential interferences. Actual values
must be determined for each analytical system when necessary.
Only those interferences listed were investigated. The blank spaces in
Table F-2 indicate that measurable interferences were not observed for
the interferent concentrations listed in Table F-3. Generally, inter-
ferences were discernible if they produced peaks or background shifts
corresponding to 2 to 5 percent of the peaks generated by the analyte
concentrations (also listed in Table F-3).
F.2.2 Physical Interferences
Physical interferences are generally considered to be effects associ-
ated with the sample nebulization and transport processes. Changes in
viscosity and surface tension can cause significant inaccuracies,
especially in samples that contain high dissolved solids or acid con-
centrations. The use of a peristaltic pump may lessen these inter-
ferences. If these types of interferences are operative, they must be
reduced by dilution of the sample or by utilization of standard addition
techniques.
High dissolved solids may also cause salt buildup at the tip of the
nebulizer. This affects aerosol flow rate and causes instrumental
drift. Wetting the argon prior to nebulization, the use of a tip washer,
or sample dilution have been used to control this problem.
It has been reported that better control of the argon flow rate improves
instrument performance. This is accomplished with the use of mass flow
controllers.
F.2.3 Chemical Interferences
Chemical interferences are characterized by molecular compound formation,
ionization effects, and solute vaporization effects. Normally these
effects are negligible with the ICP technique. If observed, they can be
minimized by careful selection of operating conditions (i.e., incident
power, observation position, and so forth), by buffering of the sample,
by matrix matching, and by standard addition procedures. These types
of interferences can be highly dependent on matrix type and on the
specific analyte element.
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TABLE F-2. ANALYTE CONCENTRATION EQUIVALENTS (mg/L) ARISING FROM
INTERFERENCES AT THE 100-mg/L LEVEL
Analyte
Wavelength
(nm)
Al
Ca
Interference
Cr Cu
Fe
Calcium
Magnesium
Mg
-- 0.08 —
0.02 0.11 --
Interference
Mn Ni Ti
0.01
0.13
Calcium
Magnesium
0.01
0.04
0.25
0.03
0.07
0.03
0.12
F.2.4 Interference Tests
Whenever a new or unusual sample matrix is encountered, a series of
tests should be performed prior to reporting concentration data for
analyte elements. These tests, as outlined in sections F.2.4.1 through
F.2.4.4, will ensure that neither positive nor negative interference
effects are operative on any of the analyte elements, in a way that
would distort.
F.2.4.1 Serial Dilution—If the analyte concentration is sufficiently high
(minimally a factor of 9 above the instrumental detection limit
after dilution), an analysis of a dilution should agree within 5
percent of the original determination (or within some acceptable
control limit that has been established for that matrix). If not, a
chemical or physical interference effect should be suspected.
F.2.4.2 Spiked Addition—The recovery of a spiked addition added at a minimum
level of 10X the instrumental detection limit (maximum 100X) to the
original determination should be recovered to within 90 to 110 percent
or within the established control limit for that matrix. If not, a
matrix effect should be suspected. The use of a standard addition
analysis procedure can usually compensate for this effect.
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TABLE F-3. INTERFERENCE AND ANALYTE ELEMENTAL CONCENTRATIONS USED
FOR INTERFERENCE MEASUREMENTS IN TABLE F-2
Analytes (mg/L) Interferences (mg/L)
Ca 1
Mg 1
AT
Ca
Cr
Cu
Fe
Mg
Nn
Ni
Ti
V
1,000
1,000
200
200
1,000
1,000
200
200
200
200
CAUTION: The standard addition technique does not detect coincident
spectral overlap. If overlap is suspected, use of computer-
ized compensation, an alternate wavelength, or comparison
with an alternate method is recommended.
F.2.4.3 Comparison with Alternate Method of Analysis—When investigating a
new sample matrix, a comparison test may be performed with other
analytical techniques such as atomic absorption spectrometry or
other approved methodology.
F.2.4.4 Wavelength Scanning of Analyte Line Region—If the appropriate equip-
ment is available, wavelength scanning can be performed to detect
potential spectral interferences.
F.3 Safety
Generally, the calibration standards, sample types, and most reagents
pose no hazard to the analyst. Protective clothing (lab coats and gloves)
and safety glasses should be worn when handling concentrated acids.
Follow the safety recommendations for the instrument provided by the
manufacturer for the operation of the ICP.
The toxicity or carcinogenicity of each reagent used in this method has
not been precisely defined. Each chemical compound should be treated as
a potential health hazard. From this viewpoint, exposure to these chemicals
must be reduced to the lowest possible level by whatever means available.
The laboratory is responsible for maintaining a current awareness file of
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OSHA regulations regarding the safe handling of the chemicals specified
in this method. A reference file of material data handling sheets should
also be made available to all personnel involved in the chemical analysis.
Additional references to laboratory safety are available and have been
identified (DHEW, 1977; OSHA, 1976; ACS, 1979) for the information of
the analyst.
F.4 Apparatus and Equipment
° Inductively Coupled Plasma-Atomic Emission Spectrometer.
o Computer-controlled ICP emission spectrometer with background correc-
tion capability.
F.5 Reagents and Consumable Materials
o Acids used in the preparation of standards and for sample processing
must be ultra-high purity grade or equivalent (e.g., Baker Ultrex grade
or SeaStar Ultrapure grade).
a. Hydrochloric Acid, concentrated (sp gr 1.19).
b. Hydrochloric Acid (50 percent v/v)--Add 500 ml concentrated HC1 to
400 ml water and dilute to 1 L.
c. Nitric Acid, concentrated (sp gr 1.41).
d. Nitric Acid (50 percent v/v)--Add 500 ml concentrated HNOs to 400 ml
water and dilute to 1 L.
o Water — Water must meet the specifications for Type I Reagent Water
given in ASTM D 1193 (ASTM, 1984).
o Standard Stock Solutions—Solutions should be purchased or alternatively
may be prepared from ultra-high purity grade chemicals or metals. All
salts must be dried for 1 hour at 105 C unless otherwise specified.
CAUTION: Many metal salts are extremely toxic and may be fatal if
swallowed. Wash hands thoroughly after handling.
a. Calcium Stock Standard Solution (100 mg/L)— Suspend 0.2498 g
(dried at 180°C for 1 hour before weighing) in water and dissolve
the mixture cautiously with a minimum amount of 50 percent HN03. Add
10.0 ml concentrated HN03 and dilute the solution to 1,000 ml with
water.
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b. Magnesium Stock Standard Solution (100 mg/L)--Dissolve 0.1658 g MgO
in a minimum amount of 50 percent HN03. Add 10.0 ml concentrated
HN03 and dilute the solution to 1,000 mL with water.
F.6 Sample Handling, Preservation, and Storage
For the determination of trace elements, contamination and loss are of
prime concern. Dust in the laboratory environment, impurities in reagents,
and impurities on laboratory apparatus which the sample contacts are all
sources of potential contamination. Sample containers can introduce
either positive or negative errors in the measurement of trace elements
by (a) contributing contaminants through leaching or surface desorption
and (b) by depleting concentrations through adsorption. Thus the collec-
tion and treatment of the sample prior to analysis requires particular
attention. Labware should be thoroughly acid-washed.
Samples are collected and processed in the field and processing laboratory.
A portion (aliquot 1) of each sample is filtered and acidified (0.1-mL
increments) with nitric acid until the pH <2. The processed samples are
then sent to the lab and are analyzed (as is) for dissolved metal (Ca and
Mg) content.
F.7 Calibration and Standardization
Prepare a calibration blank and a series of dilute calibration standards
from the stock solutions so that the expected sample concentration range
is spanned. Match the acid content of the standards to that of the samples
(written on the sample label, ca. 0.2 percent). A multi-element standard
may be prepared.
The calibration procedure varies with the various ICPES instruments.
Calibrate the ICPES for each analyte by following the instrument operating
conditions.
F.8 Quality Control
The required QC procedures are described in Section 3.
F.9 Procedure
Step 1—Set up instrument as recommended by the manufacturer or as
experience dictates. The instrument must be allowed to become thermally
stable before beginning (10 to 30 minutes).
Step 2--Profile and calibrate instrument according to the recommended
procedures for the instrument provided by the manufacturer. Flush the
system with the calibration blank between each standard. (The use of the
average intensity of multiple exposures for both standardization and sample
analysis has been found to reduce random error.)
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Step 3--Begin sample analysis, flushing the system with the calibration
blank solution between each sample. Remember to analyze required QC
samples.
Step 4—Dilute and reanalyze any samples with a concentration exceeding
the calibration range.
F.10 Calculations
Generally, instruments are calibrated to output sample results directly
in concentration units. If not, then a manual calibration curve must
be prepared, and sample concentrations must be determined by comparing the
sample signal to the calibrated curve. If dilutions were performed, the
appropriate factor must be applied to sample values. Report results as
mg/L for each analyte.
F.ll Precision and Accuracy
In an EPA round-robin study, seven laboratories applied the ICP technique
to acid-distilled water matrices that had been dosed with various metal
concentrates; Ca and Mg, however, were not included. Table F-4 lists the
true value, the mean reported value, and the mean %RSD (U.S. EPA, 1983).
TABLE F-4. ICP PRECISION AND ACCURACY DATA1
Sampl e 1
Samp! e 2
Element
Mn
Fe
True
Value
(ug/L)
350
600
Mean
Reported
Value
(ug/L)
345
594
Mean
%RSD
2.7
3.0
True
Value
(ug/L)
15
20
Mean
Reported
Value
(yg/L)
15
19
Mean
%RSD
6.7
15
Sampl e 3
E 1 ement
Mn
Fe
True
Value
(ug/L)
100
180
Mean
Reported
Value
(ug/D
99
178
Mean
%RSD
3.3
6.0
all elements were analyzed by all laboratories.
Ca and Mg were not determined.
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Appendix F
Revision 1
Date: 4/87
Page 9 of 9
F.12 References
American Chemical Society, 1979. Safety in Academic Laboratories,
3rd ed. Committee on Chemical Safety, ACS, Washington, D.C.
American Society for Testing and Materials, 1984. Annual Book of ASTM
Standards, Vol. 11.01, Standard Specification for Reagent Water,
D 1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsylvania.
Department of Health, Education, and Welfare, 1977. Carcinogens -
Working with Carcinogens. No. 77-206. DHEW, Public Health Service,
Center for Disease Control, National Institute for Occupational
Safety and Health, Cincinnati, Ohio.
Fassel, V. A., 1982. Analytical Spectroscopy with Inductively Coupled
Plasmas - Present Status and Future Prospects. In: Recent Advances
in Analytical Spectroscopy. Pergamon Press, Oxford and New York.
Occupational Safety and Health Administration, 1976. OSHA Safety and
Health Standards, General Industry. OSHA 2206 (29 CFR 1910). OSHA.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemi-
cal Analysis of Water and Wastes, Method 200.7, Inductively Coupled
Plasma-Atomic Emission Spectrometric Method for the Trace Element
Analysis of Water and Wastes. EPA-600/4-79-020. U.S. EPA, Cincinnati,
Ohio.
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