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Pesticide volatilization from soil: Lysimeter measurements versus predictions of European registration models

: Wolters, A.; Linnemann, V.; Herbst, H.; Klein, M.; Schäffer, A.; Vereecken, H.

Journal of environmental quality 32 (2003), No.4, pp.1183-1193
ISSN: 0047-2425
Journal Article
Fraunhofer IME ()

A comparison was drawn between model predictions and experimentally determined volatilization rates to evaluate the volatilization approaches of European registration models. Volatilization rates of pesticides (C-14-labeled parathion-methyl, fenpropimorph, and terbuthylazine and nonlabeled chlorpyrifos) were determined in a wind-tunnel experiment after simultaneous soil surface application on Gleyic Cambisol. Both continuous air sampling, which quantifies volatile losses of C-14-organic compounds and (CO2)-C-14 separately, and the detection of soil residues allow for a mass balance of radioactivity of the C-14-labeled pesticides. Recoveries were found to be >94% of the applied radioactivity. The following descending order of cumulative volatilization was observed: chlorpyrifos > parathion-methyl > terbuthylazine > fenpropimorph. Due to its high air-water partitioning coefficient, nonlabeled chlorpyrifos was found to have the highest cumulative volatilization (44.4%) over the course of the experiment. Volatilization flux rates were measured up to 993 mug m(-2) h(-1) during the first hours after application. Parameterization of the Pesticide Emission Assessment at Regional and Local Scales (PEARL) model and the Pesticide Leaching Model (PELMO) was performed to mirror the experimental boundary conditions. In general, model predictions deviated markedly from measured volatilization rates and showed limitations of current volatilization models, such as the uppermost compartment thickness, making an enormous influence on predicted volatilization losses. Experimental findings revealed soil moisture to be an important factor influencing volatilization from soil, yet its influence was not reflected by the model calculations. Future versions of PEARL and PELMO ought to include improved descriptions of aerodynamic resistances and soil moisture dependent soil-air partitioning coefficients.