Application for the Reassessment of a Hazardous Substance under ...

Plants and soil organisms, off-target soil exposureMaximum application rates (Table C2) were used to calculate concentrations in soil adjacentto the application area. For off-field deposition of the substances it was assumed that driftfrom a 1 ha treated area was evenly distributed over a 1 ha non-target area. It was assumedthat 9.7% of the active ingredient will drift outside the target area by airblast application,6.6% by ground application high boom (vegetables, cereals, berries, maize), and 2.9% byground boom application low boom (strawberries, pasture). These drift assumptions werebased on GENEEC2 modelling. Dichlorvos application to passionfruit is by knapsack sprayer,but GENEEC2 does not provide a drift assumption for knapsack application. As passionfruitis a vigorous, climbing vine that clings by tendrils to almost any support it was assumed thatthe drift is comparable with a ground application high boom (6.6%). Results are shown inTable C6 for dichlorvos.Table C6:Deposition dichlorvos off-fieldApplication scenarioApplication rate(kg ai/ha)% of applicationdriftingDeposition bydrift (kg/ha)Deposition(mg/m 2 )Airblast 2.052 9.7 0.199 19.9Ground (high boom) 0.8 6.6 0.053 5.3Ground (low boom) 0.8 2.9 0.023 2.3Knapsack 1.026 6.6 0.068 6.8Soil concentrations of the active ingredient are calculated by assuming the deposition wouldmix into the top 5 cm of soil, and this soil would have a bulk density of 1500 kg/m 3 , ie thedeposition expressed in mg/m 2 would mix into 75 kg of soil.Deposition after 2 applications was calculated according to European guidance (EU, 2000):PEC multiple applications = PEC one application x (1- e -nki ) / (1-e –ki )Where for dichlorvosPEC = predicted environmental concentrationn = number of applications =2k= ln 2/ DT 50 (in days)i= interval between two consecutive applications in days= 7 daysDT 50 = half life soil in days = 1 daye = constant= 2.718The estimated soil concentrations of dichlorvos are shown in Table C8.Table C8:Soil concentration of dichlorvosApplicationscenarioSoil concentration off field (mg/kg)Soil concentration in field (mg/kg)1 application 2 applications 1 application 2 applicationsAirblast 0.27 0.27 2.74 2.74Ground (highboom)0.07 0.07 1.07 1.07Dichlorvos reassessment – application Page 136 of 436