Fumigants
131
FIGURE 8.8
MeBr air concentrations measured at different distances from downwind of feld.
Complex-Short Term II [ISC-STII]) in order to assess the value of this model
for use in exposure assessment for agricultural workers and downwind residents (Seiber et al., 1996). As expected, measured air concentrations of MeBr
fell off exponentially with downwind distance (Figure 8.8). MeBr air concentrations measured downwind of the treated feld source compared well with
those predicted by the ISC-STII model, although measured dispersion values
were less than modeled dispersion values by a factor of ~2. Later, application of the SCREEN-3 model allowed for better approximation of actual measured values.
Section 8.3.1: (Reprinted (adapted) with permission from Seiber et al. (1996).
Flux, Dispersion Characteristics, and Sinks for Airborne Methyl Bromide
Downwind of a Treated Agricultural Field. In Fumigants, pp. 154–177.
Washington, D.C.: American Chemical Society. Copyright (1996) American
Chemical Society.)
8.3.2 Flux from Multiple Sources
Estimates of downwind concentrations of pollutants from multiple agricultural sources simultaneously were addressed in a feld study conducted in
September 1995 (Honaganahalli and Seiber, 2000). The ambient atmospheric
concentrations of MeBr in the Salinas Valley, California, were measured following application of MeBr to multiple agricultural felds (Figure 8.9). To
catch the spreading plume, air samples of MeBr were measured at 11 sites
located on the adjacent mountains, valley foor, and at the Pacifc Ocean coast
each night and day over a 4-day period. The laborious feld experiment could
then be adjusted for weather, topography, application rate and method, and
tarp composition using computational models provided by EPA (ISCST) and
California EPA (CALPUFF). MeBr exposure for the population of the city of
Salinas was calculated based on the measured ambient concentrations and
131
FIGURE 8.8
MeBr air concentrations measured at different distances from downwind of feld.
Complex-Short Term II [ISC-STII]) in order to assess the value of this model
for use in exposure assessment for agricultural workers and downwind residents (Seiber et al., 1996). As expected, measured air concentrations of MeBr
fell off exponentially with downwind distance (Figure 8.8). MeBr air concentrations measured downwind of the treated feld source compared well with
those predicted by the ISC-STII model, although measured dispersion values
were less than modeled dispersion values by a factor of ~2. Later, application of the SCREEN-3 model allowed for better approximation of actual measured values.
Section 8.3.1: (Reprinted (adapted) with permission from Seiber et al. (1996).
Flux, Dispersion Characteristics, and Sinks for Airborne Methyl Bromide
Downwind of a Treated Agricultural Field. In Fumigants, pp. 154–177.
Washington, D.C.: American Chemical Society. Copyright (1996) American
Chemical Society.)
8.3.2 Flux from Multiple Sources
Estimates of downwind concentrations of pollutants from multiple agricultural sources simultaneously were addressed in a feld study conducted in
September 1995 (Honaganahalli and Seiber, 2000). The ambient atmospheric
concentrations of MeBr in the Salinas Valley, California, were measured following application of MeBr to multiple agricultural felds (Figure 8.9). To
catch the spreading plume, air samples of MeBr were measured at 11 sites
located on the adjacent mountains, valley foor, and at the Pacifc Ocean coast
each night and day over a 4-day period. The laborious feld experiment could
then be adjusted for weather, topography, application rate and method, and
tarp composition using computational models provided by EPA (ISCST) and
California EPA (CALPUFF). MeBr exposure for the population of the city of
Salinas was calculated based on the measured ambient concentrations and