United States
 Environmental Protection
 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
  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).

  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,
  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.

  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.

Table 1.    Participants in the Cold Weather Plume Study
Environmental Measurements, Inc. (EMI)
AeroVironment, Inc. (AV)
SRI International
Washington University Technology Associates (WUTAj
EPA Environmental Monitoring Systems Laboratory, Las Vegas

Battelle Columbus Laboratories (BCL)
Meteorology Research, Inc. (MRI)
Rockwell International
  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
  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

  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

 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
   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
   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

   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
Center for Environmental Research
Cincinnati OH 45268
Official Business
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