United States Environmental Protection Agency Atmospheric Research and Exposure Assessment Laboratory Research Triangle Park, NC 27711 Research and Development EPA/600/S3-90/040 Aug. 1990 &EPA Project Summary Summary Report for the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) Site Visitation Program for the Period October 1987 through September 1988 W. C. Eaton, C. E. Moore, R. W. Murdoch, R. C. Shores, and D. A. Ward The proper collection of precipitation and the accurate measurement of its constituents are important steps in attaining a better understanding of the distribution and effects of "acid rain" in the United States. One of NAPAP Task Group IV's major programs concerns wet deposition monitoring. One of that pro- gram's projects, 4A-15, "Quality Assur- ance Support for Wet Deposition Mon- itoring," is sponsored by the U.S. Environmental Protection Agency (EPA) to evaluate the sample collection process and provide technical assistance to the NADP/NTN network through a site visitation program. Research Triangle Institute, as contractor to EPA, conducts these visits. If deficiencies or nonstand- ard procedures are noted, the site operator and supervisor are notified. Brief reports are sent to the EPA Project Officer, the NADP/NTN Quality Assur- ance Manager, and others. In this way, necessary changes can be made promptly. All NADP/NTN sites were visited in 1985-1986. A second round of visits began in October 1986, with the goal of visiting approximately one-third of the 200 sites each year over the next three years. This document is a summary report of the findings from the 1987-1988 (Fiscal Year 1988) site visitation program to 57 of the sites of the NADP/NTN network. In its present configuration, the network's research and monitoring programs are supported and operated by the U.S. Geological Survey; State Agricultural Experiment Stations; the Departments of Agriculture, the Interior, Commerce, and Energy; and EPA. Additional support is provided by state agencies, public utilities, and industries. Protocols and procedures followed in conducting the site visits are described. Results of systems and performance audits are discussed for siting, collection equipment, and the field support labor- atories. Where exceptions are found, the potential effects of nonstandard siting, improperly operating equipment, and improper sample handling or analysis technique on the database are dis- cussed. This report was submitted in partial fulfillment of EPA Contract No. 68-D8- 0001 by Research Triangle Institute. This report covers site visits made during the period October 1, 1987, through Sep- tember 30,1988. All work was completed as of September 30,1988. This Project Summary was developed by EPA's Atmospheric Research and Exposure Assessment Laboratory, Research Triangle Park, NC, to announce key findings of the research project that ------- Is fully documented In a separate report of the same title. (See Project Report ordering Information at back). Introduction The main report summarizes quality assurance assistance and findings from site visits made to the National Atmo- spheric Deposition Program/National Trends Network (NADP/NTN) precipita- tion collection stations for the period October 1987 through September 1988. Each site is located and operated accord- ing to protocols and procedures as given in the siting and operating manuals for the networks. The purposes of the site visitation program, sponsored by the U.S. Environmental Protection Agency (EPA), are to verify that each site is operating within control limits and according to established procedures, and to provide technical assistance as required. Fifty-seven of the 196 sites that were in operation as of January 15,1989, were visited during this time frame. Figure 1 shows the NADP/NTN site locations. Goals of the Site Visitation Program The goals of the site visitation program for quality assurance assistance to the NADP/NTN collection sites are as follows: 1. Provide a qualitative assessment of each site and its surroundings, the operator's adherence to sample col- lection and analysis procedures, and the condition of the site's collection and analysis equipment through an on-site systems survey; 2. Provide a quantitative assessment of the operation of the precipitation collector and the accuracy of response of field and laboratory measurement devices for precipitation depth, mass, temperature, conductivity, and pH through, an on-site performance survey; 3. Provide technical assistance to the opierator by verbal explanation, minor troubleshooting, repair and calibration of equipment, and by making recom- mendations for sources of corrective action; 4. Prepare brief reports for each site detailing site characteristics, results of quality assurance tests, and technical assistance provided. Submit the reports to the NADP/NTN Quality Assurance Manager, the Central Ana- lytical Laboratory's Site Liaison, and the EPA Project Officer; 5. Computerize results of all information gathered from each site and submit this to the NADP/NTN Quality Assurance Manager on an annual basis; 6. Document the sites and their surround- ings by assembling a collection of site maps and color photographs. , '.,V~-3 > . .. .. \ ..~5?"£ ''» .->.\> i : '-...e^ h c»^ «d v-TT 1 T s v.^ ic ; I SO -c -^ ~x SH ' T- ND.«, \ ~"v I I MN >C vvwv t " -L?_V K-^ / -rW ,' 4 S-sAJ" jfe? ( «v ' T^r~.-L, " « A " }i T>T.T-, 0\ bf »cj P%o **" j X V **J IM !tS_/v 0 100 200 300 400 Mi 1 - 1 AS \9* 0 161 322 483 644 Km OS? Figure 1. Location of active sites in the NADP/NTN network as of August 1989. ------- Conclusions Fifty-seven of the 196 active NADP/ NTN precipitation collection sites were visited over the one-year period, October 1987 through September 1988. About one-third of the sites were visited during this second year of a three-year effort. The sites are located in all regions of the country and are sponsored and operated by numerous agencies. Each site is located according to established siting criteria and operates according to pub- lished procedures. This report assesses the degree to which criteria and proce- dures are adhered to; predicts, where possible, the relative impact on the data that might be expected from the variances found; and compares results thus far from the second round of visits to those docu- mented in the first round of visits that occurred over the period December 1984 through September 1986. Siting Improvements in adherence to siting criteria were noted at most of the sites visited in 1988 that were not in compliance at the time of the first round of visits in 1985-1986. A number of sites had sepa- rated the collector and rain gauge to the prescribed 5-m distance and had oriented the collector's wet-side bucket to the west. Obstructions and sources of dust such as animals, parking lots, and chem- ical storage areas had been removed, or the site's equipment had been moved away from them. For the 13 siting criteria summarized in this report, 41 of 57 sites (72%) visited in FY 1988 had at least one variance. Twenty-five percent of the sites had three or more variances. However, most of the variances are expected to have minimal effects on the database because of the nature of certain criteria and/or the degree to which the criteria were exceeded. For example, network siting criteria require that the precipitation collector and rain gauge be separated by at least 5 m but not more than 30 m. Twenty-six percent of the 57 sites did not meet this criterion, always because of inadequate separation. Sample Collection Designated sample collection proce- dures were adhered to at almost all the sites in the network. All operators were careful not to touch the inside of the collection bucket or lid or contaminate the sample in any' way. All site operators stated that they checked the sample for contaminants (leaves, bird droppings, etc.) at the time of the bucket's removal from the collector. This procedure was not being well adhered to at the time of the first round of visits. To ensure accurate precipitation data, it is most important that the precipitation collector and rain gauge are properly working and well-maintained. Only two sites were unable to make a weekly equip- ment check. A properly working precip- itation collector should uncover the wet bucket at the beginning of a precipitation event and recover the wet bucket shortly after the event stops to keep matter such as dust out of the wet bucket when there is no precipitation. There were indications at 13 of 57 sites (23% of the total) that the clutch on the Aerochem Metrics precipitation collector was wearing; however, only 2 of these 13 failed to operate properly when tested with a 1600- g load. Only 2 of 55 sensors checked were not operating properly. Fifty-two percent of the rain gauges (29 of 56) were found to be out of calibration by more than ±0.1 in. at some point on the 0-12-in. scale. This is not believed to be a major source of error because the calibration errors usually occurred at a depth of 5 in. or more, and the operator is instructed to empty the catch bucket before this depth is reached. Calibration checks showed that 48 of the 56 gauges (86%) met acceptable calibration criteria (±0.1 in.) over the range of 0 to 5 in. Field Laboratory Procedures Field laboratory procedures for sample handling, conductivity measurements, and pH determinations were being carried out properly and accurately in almost all cases. Proper procedures were dis- cussed or demonstrated to site operators as needed. Results were improved over those noted at the time of the first round of visits. For example, all but three sites were able to determine the pH to within ±0.1 unit of the designated value. Two sites had inoperative pH meters and could not be checked. All six of the sites that were outside of tolerance for pH measurements in Round 1 were within tolerance in Round 2. Overall, 95% of the 55 field laboratories checked in 1988 agreed within ±0.1 pH unit with the audit solu- tion's designated value. For conductivity measurements, each of the 53 sites checked (100%) determined the audit solution's conductivity to within ±4 juS/cm of the designated value. Four sites had exceeded the limit of agreement during Round 1 visits. Four sites had malfunctioning or broken equipment and thus could not be audited. The solution balances were operating properly in all of the 56 cases checked. Of 56 balances checked, more than half agreed within ±1 g with the designated weight over the range of 823 to 4043 g. All but one balance agreed within ±5 g with the designated weight over the same range. In terms of percent variation with respect to weight, the worst case for the 55 balances that operated within ±5 g agreement would be ±0.6% at a loading of 823 g and ±0.1 % at a loading of 4043 g. Recommendations The site precipitation collector and rain gauge,are central to the successful operation of the network. However, the equipment in the NADP/NTN network is aging and will require increased main- tenance. Therefore, weekly equipment checks by the operator should continue to detect problems as early as possible. The collector's clutch assembly should be inspected for signs of wear. The failure of the precipitation collector's sensory heaters has greatly diminished. A simple check of the collector's sensory heater by activating the collector with water and, after 5 min, lightly touching the sensory surface to verify it is heating, should con- tinue. A number of rain gauges were found to be out of calibration. However, many of those calibrated in 1985-1986 met specifications in 1988. It is recommended that a simple, on-site calibration check1 of the rain gauge be carried out every six months. A copy of the gauge chart used for the check should be forwarded to the network's Central Analytical Labor- atory (CAL) for review. Recommendations for improving site locations center on those siting criteria that, if violated, may affect the catch efficiency or chemistry of the precipitation samples. Specifically, it is recommended that the NADP/NTN Coordination Office take the following steps to correct con- ditions at several sites. Relocate the collector or remove the obstruction (tree, etc.) that causes the 45° angle rule to be violated (five sites). Relocate the collector or restrict use of nearby parking lots and storage ------- facilities so that a 100-m separation is achieved (six sites). Relocate the collector or install fencing so that animals are kept at least 30 m away (12 sites) Relocate the collector so that transpor- tation roadways and sources are at least 100 m away (two sites). Reorient the collectors whose wet-side collection bucket faces north or east so that all wet-side buckets face west (seven sites). Where expedientand inexpensive to do so, relocate collectors or rain gauges so that a minimum separation distance of 5 m is achieved (15 sites). Emphasize to site operators and super- visors that grass, weeds, and small trees or bushes should be kept at a height of 2 ft or less in a circle with a radius of 30 m from the collector. Level any collectors or rain gauges that are out of tolerance (two sites). Investigate whether or not the resistivity required to activate the collector sensor should be set closer to the factory value of 80K n for several of the collectors. Supply rain gauge dampening fluid (silicone oil) to those sites that may need to fill reservoirs to within 0.25 in. of the top. Site Survey Visits A quality assurance systems survey was conducted at each site to qualitatively assess the site, its surroundings, and the operator's adherence to procedures specified in the NTN design document and in the NADP/NTN site operator's instruction manual. Criteria for siting an NADP/NTN precipitation station are illustrated in Figure 2. The operator was asked to demonstrate sample collection and analysis, procedures. These were observed with special attention given to calibration procedures and sample han- dling technique. Site equipment was examined for signs of wear or faulty operation. It was noted whether solutions and equipment were properly stored. Site logbooks and rain gauge charts (if present) were examined for legibility, completeness, and accuracy. Information from the systems survey was entered in the systems survey questionnaire. Two sets of photographs (color slides) of the sites were taken. The N, E, 8, and W views were photographed with the precipitation collector in the foreground. Additional views were taken as specified in the questionnaire. A quantitative performance survey was conducted at each site. Table 1 lists the equipment that was checked for perfor- mance and the type of test used. Criteria for evaluating performance are specified in the NADP Quality Assurance Plan. Wo residential structures within 30m, within 30° . cone of mean wind direction Wo ~~ object should project _ beyond \ Wet bucket- Collector L-X Overhead wire, tree, building, etc. 5m Conversion m-ft 0.3-1.0 0.6-2.0 5-16 20-66 30-98 500-1640 km - mi 10-6.2 20-12.4 40-24.8 \ Notes Platforms discouraged; however, no higher than anticipated ^_ snowpak Spacing between the gauge and collector at 5 to 30m * Wo residential buildings within upwind 30° cone If more than 2096 of precipitation Is snow, gauge must have an alter wind shield, pivot axis at same elevation as gauge inlet In snow areas, collector roofs should be properly counter weighted * Question future land use Changes must be submitted to coordinator's office Wo objects greater than 1 m in height 20m* Slopes±15% > Natural vegetation <0.6 m : 1 Wo grazing animals , ' 30m* No sudden changes in slope greater than ±15% Farm area should be nothing except vegetation maintained at less than 0.6 m TOO m* No surface storage of agricultural products, fuels, vehicles, parking lots, or maintenance yards No moving source of pollutants such as runway, taxiway, road, or navigable river 500 m* No feed lots, dairy barns, or large concentration of animals 10 km * No downwind industries, factories, chemical or power plants * No downwind urban areas greater than 10,000 20 km No upwind industries, factories, chemical or power plants No upwind urban areas greater than 10,000 > Wo downwind urban areas greater than 75,000 40 km* No upwind urban areas greater than 75,000 Figure 2. NADP/NTN siting criteria. ------- Table 1. NADP/NTN Site Measurements and Performance Survey Methods Site Measurement Measurement Device Performance Survey Method Designated Performance Criteria Rain depth Precipitation sample collection Mass PH Conductivity Rain gauge (Belfort) Precipitation collector (Aero- chem Metrics) Triple beam balance pH meter and electrode Conductivity meter and cell Challenge with known weights that simulate rainfall. Measure resistance across sensor, measure tension and drop of bucket lid, measure temperature and resistance of activated sensor. Challenge with traceable weights. Challenge with simulated precipitation sample of known pH. Challenge with simulated precipitation sample of known conductivity. Agreement within ±0.1 in. of test weight value over the range 0-12 in. Resistance in range of 60- 90K n. Lid drop distance >3 mm. Sensor temperature ambient prior to activation; temperature of 50-70° C after activation. Agreement within ±5 g of test weight value. Agreement within ±0.1 pH unit of test solution's desig- nated value. Agreement within ±4 fjS/cm of test solution's designated value. ------- ------- ------- W. C. Eaton, C. E. Moore. R. W. Murdoch, R. C. Shores, and D. A. Ward are with Research Triangle Institute, Research Triangle Park, NC 27709. Berne I. Bennett is the EPA Project Officer (see below). The complete report, entitled "Summary Report for the National Atmospheric Deposition Program/National Trends Network (NADPiNTN) Site Visitation Program for the Period October 1987 through September 1988," (Order No. PB 90-212 614/AS; Cost: $17.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Atmospheric Research and Exposure Assessment Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Official Business Penalty for Private Use $300 EPA/600/S3-90/040 ------- |