Background: Foliage residue decline data are used to re ne the risk assessment for herbivorous birds and mammals foraging in elds treated with plant protection products. For evaluation, current EFSA guidance has a clear focus on single-rst order (SFO) kinetic models. However, other kinetic models are well established in other areas of environmental risk evaluations (eg, soil residue assessment), and easyto-use calculation tools have become available now. We provide case studies with 6 fungicides how such evaluations can be conducted with two of these tools (KinGUII and TREC) that have been developed by Bayer. Results: SFO kinetics provided the best ts only for 13 of 36 residue decline studies conducted in a standardized design under eld conditions. Biphasic models (double rst order in parallel, hockey stick) were often superior and sometimes more conservative for risk assessment. The additional effort is manageable when using software such as KinGUII and TREC, and appears justi ed by the more reliable outcome of the evaluations. Conclusions: Further research would be useful to better assess the extent to which non-SFO better ts foliage residue decline, but our study suggests that it may be a signi cant proportion. Therefore we encourage the use of biphasic models in the regulatory risk assessment for herbivorous birds and mammals, in the ongoing revision of the European Food Safety Authority (EFSA) guidance document from 2009.

-Agricultural use of pesticides has remained high for economic reasons. Because aquatic species may bioaccumulate pesticides more readily than terrestrial organisms, there has been much concern about pesticides in agricultural runoff. Despite this concern, there presently is little relevant information for use in making accurate predictions of the impact of specific pesticide amounts in agricultural runoff on water quality at some point downstream. There is a compelling need for fundamental research on the physical, chemical, biological and hydrological processes that regulate pesticide behavior not only in agricultural and aquatic habitats, but also during transit between the two. Further, data are needed concerning pesticide toxicity potential as a function of the aquatic physical and chemical regime, and concerning population recovery dynamics as a function of pesticide concentration and species stress.

The purpose of this study was to quantify hysteresis during adsorption and desorption of atrazine as a function of incubation time for a Sharkey clay soil. Adsorption was carried out using one day batch equilibration and was followed by incubation periods ranging from 1 to 24 d. Incubation was subsequently followed by six consecutive desorption steps where each step represented 1 d. The Freundlich equation (S = K CNwhere S is the amount of atrazine retained, μg g-1; C is concentration, μg ml-1; K is the distribution coefficient, cm3g-1; and N is a dimensionless parameter) was used to describe batch results. Both adsorption and desorption isotherms were well described by the Freundlich model. Fitted K parameter values for desorption isotherms were consistently higher than those associated with adsorption. The opposite trend was observed for the exponential parameter N. The results revealed that desorption deviated significantly from adsorption data. The deviation, which is commonly referred to as hysteresis, was more pronounced as incubation time increased. Batch equilibration results also indicated that the extent of hysteresis was not influenced by soil sterilization. Attempts to quantify the extent of hysteresis using a simplified approach are presented. We found that, for a given batch data set, hysteresis can be quantified provided that Freundlich N from adsorption and desorption isotherms is known.

We have studied the leaching losses of NO3, atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], and metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazine‐5(4H)‐one] applied to sugarcane (Saccharum officinarum L.) planted in Mississippi River alluvial soil in southern Louisiana. Nitrogen (122 kg/ha) and atrazine (2.24 kg/ha) were applied in June, and atrazine (2.24 kg/ha) and metribuzin (1.12 kg/ha) were applied in December; losses through a Sharkey clay (very fine, montmorillonitic, nonacid, thermic Vertic Haplaquepts) into subsurface drains (5.5‐ and 10.9‐m spacing) were measured for about 100 d in both seasons. Five days after application NO3‐N appeared in its highest concentrations (5–11 mg/L) in the drain water; after this first event, concentrations remained below 10 mg/L throughout the summer season. After application in the summer atrazine appeared in the subsurface drains at its highest seasonal concentrations (114–144 µg/L) on the day of application; after 4 to 7 wk these concentrations remained below 3.0 µg/L. Total losses in the summer amounted to 3 to 8% of the NO3 application and 0.6 to 1.2% of the atrazine application. Almost 50% of the NO3 leaching into the subsurface drains occurred after Day 76, whereas 82% of the atrazine leached into the drains by Day 8. After the winter application, high concentrations of atrazine (67–81 µg/L) and metribuzin (52–94 µg/L) were measured within 8 d. Similarly, large concentrations of atrazine occurred in the drain water throughout the winter season. The much higher concentrations of atrazine during the winter study, compared with the summer, coincided with soil surface concentrations that were 3 to 10 times those of the summer. Total losses during the winter were 0.4 to 2.0% (atrazine) and 0.4 to 1.7% (metribuzin) of the applications. Evidence for preferential flow into the drains of the NO3 and the herbicides is presented.

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