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APPENDIX 6
Determining distribution by wind

Table A presents the assumptions used for the calculations in the wind distribution model (see Figure, p.13).

TABLE A

ParameterAssumptions
Emissions from the storeDiffuse, through natural ventilation only
Average wind velocity4 m/year
Concentration of pesticides in store1 000 mg/m3
Emission rates25; 12.5; 2.5 kg/h for open, moderately open and closed stores, respectively
Distribution modelGaussic plume model (short term deposition)
Atmosphere stabilityNeutral
Diameter pesticides particlesModerately fine (80%d<4um; 17%4<d<10 um; 3% d>10 um)
Emission frequencyEvery day throughout the year

The model does have its limitations. The fact that the calculations are carried out for the worst-case parameters means that the maximum emission and maximum distance are calculated to the effect that the long-distance calculations will be overestimates, and the short-distance calculations will be underestimates.


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