United States
Environmental Protection
Agency
Atmospheric Sciences J^--
Research Laboratory -
Research Triangle Park NC 27711 -/
Research and Development
EPA/600/S3-86/065 Mar. 1987
Tf I
Project Summary
Cold Weather Plume Study
William M. Vaughan
While many studies of power plant
plume transport and transformation
have been performed during the sum-
mer, few studies of these processes
during the winter have been carried
out. Accordingly, the U.S. Environ-
mental Protection Agency and the
Electric Power Research Institute jointly
sponsored a field study in February
1981, the Cold Weather Plume study.
It was based on St. Louis, Missouri, and
focused on the plume from the Kincaid
power plant located southeast of
Springfield, Illinois. The objective was
to characterize heterogeneous and/or
homogeneous SOX and IMOX chemistry
in a power plant plume in cold weather.
Three measurement aircraft were in-
volved, along with meteorological,
analytical chemistry, and data base
support crews. Measurements were
made on five days. Stability conditions
varied from a well-mixed state with
rapid plume dispersion to a stable
atmosphere when the plume was ob-
served over 100 km downwind.
This report presents descriptive
analyses of these measurements. Cross
plume integrations of pollutant pa-
rameters are provided along with esti-
mates of plume age. An integrated data
base in consistent format has been
established to permit wider use of the
measurements.
This Protect Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).
Introduction
Most field studies of chemical conver-
sion rates of primary air pollutant emis-
sions from power plants have been
conducted during the summer. This fact
makes application of derived plume
chemistry information inappropriate for
winter conditions. In an attempt to provide
information on plume behavior under
winter conditions, the Cold Weather
Plume study was carried out in February,
1981.
The study was undertaken as a joint
effort of the U.S. Environmental Protec-
tion Agency (EPA) and the Electric Power
Research Institute (EPRI). The EPA was
interested in far field SOX transformations
having an impact on long range transport
issues, while the EPRI was primarily in-
terested in near field NOX transformation
processes for incorporation into reactive
plume models. The complementary nature
of these interests led to two interrelated
sets of measurements with a single
general objective:
To characterize SOX and NOX chemistry
in a power plant plume by heterogeneous
and/or homogeneous mechanisms in
cold weather.
Participants
The Cold Weather Plume study was
carried out by a team which received
funding from two sources, EPA and EPRI.
Table 1 indicates the funding source for
the participants.
The responsibilities of the team
members were detailed in a work plan
developed after a planning meeting held
in St. Louis in October 1980. Coordination
of the planned tasks was conducted
primarily by phone during the preparation
phase of the work. During the field study
itself, more iterative coordination was
obtained by daily meetings at the project's
Mission Control Office which was
established on the grounds of the Spirit
of St. Louis airport near the hangar used
by EMI and MRI.
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Table 1. Participants in the Cold Weather Plume Study
EPA-Supported
Environmental Measurements, Inc. (EMI)
AeroVironment, Inc. (AV)
SRI International
Washington University Technology Associates (WUTAj
EPA Environmental Monitoring Systems Laboratory, Las Vegas
EPRI-Supported
Battelle Columbus Laboratories (BCL)
Meteorology Research, Inc. (MRI)
Rockwell International
Operations
Sites
Power Plant: The plant chosen for study
was Commonwealth Edison's Kincaid
plant in central Illinois southeast of
Springfield. During the study, only one of
the two 660-MW generators was oper-
ating; effluent was emitted from a 187-m
stack with exit diameter 9 m.
Adjacent to the plant, Rockwell operated
10-m and 100-m meteorological towers.
A baseline was used for double theodolite
tracking of pibal and temperature sonde
releases. A surface meteorological station
was also operated during the study.
Mission Control: An office was set up
in a small house at the Spirit of St. Louis
airport, 70 km southwest of the Kincaid
plant. Daily weather briefings were held,
and each day's mission plans were dis-
cussed. Data from previous missions were
displayed and evaluated in order to refine
future operations.
The office was a short distance from
the main hangar used by EMI and MRI,
enabling all technical personnel to par-
ticipate in briefings and discussions. An
outside power drop was installed to allow
BCL's mobile GC laboratory to operate
near the sampling aircraft.
Instrumentation and
Measurements
Aircraft: EMI flew a Cessna 404, and
MRI, a QueenAir. Each aircraft was out-
fitted for gaseous, aerosol, and meteoro-
logical measurements as well as recording
position and altitude. EMI made con-
tinuous measurements of 03, S02,
NO/NOX, sulfate and sulfuric acid, light
scattering, Aitken nuclei, and aerosol
charge acceptance, together with tem-
perature and dew point. Batch analyzers
provided data on aerosol size distributions,
and integrated samples were collected
for subsequent laboratory analyses. MRI
made continuous measurements of 03,
S02, NO/NOX/HN03, light scattering,
condensation nuclei, and aerosol charge
acceptance, together with meteorological
parameters of total solar radiation, U-V
radiation, turbulence, temperature, and
dew point. Aerosol size distribution mea-
surements were made by a combination
of three instruments, filter samples were
collected to determine the chemical
composition of the aerosols and gaseous
NH3 and HN03, and bag samples were
collected to be returned for hydrocarbon
analysis at the BCL mobile laboratory.
All continuous data, including aircraft
position and altitude, as well as event
information were recorded on magnetic
tapes on board the two aircraft. These
tapes were delivered to Mission Control
following each flight for reduction and
preparation of data displays.
Source Measurements: Rockwell made
continuous source measurements using
the instrumentation that had been in-
stalled for EPRI's plume validation project.
Effluent concentrations of SO?, NO, and
02 were measured, together with tem-
perature and flow speed. More extensive
stack sampling had been planned, but a
severe storm shortly before the study
began disabled the elevator to be used
for such sampling.
Meteorological measurements: Rock-
well also operated the meteorological
facility at the Kincaid plant. Wind speed
and direction and temperature were
measured at several levels on the towers,
and dew point temperature and the 3-
dimensional wind were measured at the
100-m level. At a surface weather station,
pressure, cloud cover, precipitation, and
several components of radiation were
measured or observed.
On each day of aircraft operations,
Rockwell launched temperature-sounding
balloons and tracked them from a double-
theodolite baseline adjacent to the plant.
These launches began several hours
before the first aircraft took off to deter-
mine how well the observed wind agreed
with that forecast, and continued at hourly
intervals throughout each mission.
Launch data were quickly reduced onJ
site, and the resultant wind data were'
phoned to Mission Control.
AV's mobile minisonde unit operated at
five different sites located from 40 to 100
km from the plant to measure conditions
downwind. The minisondes measured air
and wet bulb temperature and pressure,
and were tracked with a theodolite to
obtained the wind aloft. These soundings
were initiated within a hour of the depar-
ture time of the first aircraft leaving the
Spirit of St. Louis airport, and continued
at approximately hourly intervals through-
out each mission.
Weather Forecasting: William Viezee
of SRI provided the weather forecasting
support for the study. He was provided
access to all the analysis and forecast
products at the National Weather Service
(NWS) office in St. Peters, Missouri,
where he would prepare each day's fore-
cast for the briefings of Mission Control;
as needed, he would return to the NWS
office for updates and refinements to the
forecast as the missions were underway.
After the field study, he prepared an
overview and description of the meteoro-
logical conditions, including air transport,
that were experienced during the study.
This summary is included as an appendix
to the full report.
Aircraft Sampling Missions: Sampling
missions extended from 12 February to
20 February, 1981. During that time, EMI
flew 7 flights on 5 different days, and
MRI flew 6 flights on 4 different days.
The EMI flight plan usually consisted of
multiple traverses across the plume at
different altitudes along with a vertical
spiral at each downwind distance. Sam-
pling ranged from just under 20 km
downwind to 114 km downwind, with
corresponding plume ages from 0.5 to 5
hours.
The MRI flight plan usually consisted
of orbits in the plume at a fixed distance
downwind extending over about an hour's
time. These flights provided measure-
ments of average plume parameters,
while sacrificing determination of the
horizontal and vertical structure of the
plume. MRI also performed one plume
sampling mission according to a flight
plan similar to the one usually used by
EMI, and also made a pre-dawn flight to
investigate plume chemistry under stable,
non-photochemical conditions. Overall,
MRI sampled from about 30 to 120 km
downwind, sampling plumes from 0.75
to 5 hours old.
The EPA Lidar aircraft conducted 6
flights on 5 days. The dual frequency
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Lidar provided vertical profiles of aerosol
rbackscatter beneath the flight tracks, with
flights over the areas of plume sampling
by both EMI and MRI. The recorded data
provided excellent pictures of the some-
times complex structure of the plume
embedded in the regional haze layer.
Quality Assurance and Data Processing
and Validation: Each participating group
was responsible for its own data proces-
sing activities, which involved instrument
calibrations, pre-flight and in-flight checks
of instrument and data acquisition system
performance, followed by careful exami-
nation and editing of the magnetic tape
data In addition, special procedures were
set up to assure timely recognition of any
instrument problems and to assure satis-
factory intercomparison of measurements
from the EMI and MRI aircraft. This inter-
comparison was carried out by cross
calibrations of instruments by the two
aircraft groups, parallel flights to make
direct in-situ measurements in the same
air mass, and analyses of split filter
samples.
WUTA processed data tapes within 24
hours, converting the data to strip chart
formats. This provided a quick appraisal
of instrument operation and of the suc-
cess of each mission. Several problems
(were corrected in timely fashion because
of this rapid data turnaround.
The cross calibrations gave satisfactory
results, with instrument responses gen-
erally within 10% of nominal input values.
The results from the parallel flights lend
confidence to the overall sampling and
data reduction procedures, since the data
from the two platforms are very close,
both in magnitude and in temporal
variations.
All data have been incorporated into a
special studies data center at Washington
University. The data base consists of final
validated data on magnetic tapes, as well
as hard copies of reports, articles, and
data volumes associated with the Cold
Weather Plume study
an ensemble of observed wind vectors
close in space and time to the plume
being dispersed, with plume "particles"
being moved in accordance with the
selected winds at successive time steps.
The majority of flights were conducted
under stable atmospheric conditions that
restricted the vertical dispersion of the
plume, and at times led to multiple plume
layers at different altitudes. Under such
conditions there were only very slow
chemical reactions within the plume, so
that even at distances on the order of
100 km, ozone levels in the plume were
still depressed below ambient values,
conversion of S02 to sulfate was in-
significant, and a substantial fraction of
the emitted NO remained unconverted to
higher oxidation states.
For those flights made under unstable
atmospheric conditions, strong and shift-
ing winds dispersed the plume very
rapidly, making its detection very difficult.
Concentrations of plume pollutants were
only slightly above background values, so
that estimates of any chemical changes
in the plume are very uncertain.
More detailed analyses of the collected
data are needed to quantitatively deter-
mine rates of chemical reactions in a
power plant plume in cold weather for
comparison with the more extensive data
available from studies conducted during
warmer seasons.
Descriptive Analyses
The data collected by the EMI and MRI
aircraft have been summarized in exten-
sive tabulations in the full report. These
list, for each orbit or cross-plume traverse,
the time of sampling, altitude, and average
values of all the measured pollutant
parameters, as well as the estimated
plume age, or time interval of transport.
Plume age together with an estimate of
plume spread was determined by a Monte
Carlo technique that selects winds from
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William M. Vaughan was with Environmental Measurements, Inc. (now with
AeroVironment, Inc.). University City, MO 63124-2110.
Francis Pooler. Jr. is the EPA Project Officer (see below).
The complete report, entitled "Cold Weather Plume Study," (Order No. PB 87-
145 694/AS; Cost: $18.95. 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 Sciences Research 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 S300
EPA/600/S3-86/065
OCQG329
PS
IL
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