Do some pesticides run off more than others? How does pesticide runoff vary with pesticide properties?

Improve understanding of pesticide runoff from croplands.

Concentrations in surface soil and in runoff from three Australian rainfall simulation studies and three rainfall simulation and five catchment studies in North American croplands were used. The ratio of event averaged runoff concentrations and the surface soil concentrations is the runoff extraction ratio.

Pesticide runoff concentrations were closely related to soil surface concentrations at the start of rainfall. Runoff extraction ratios were not significantly different for 13 pesticides with a wide range of properties, on gentle slopes (0–3%), but were significantly lower for three pesticides. On steeper slopes, runoff extraction was significantly greater for atrazine but lower for glyphosate and metolachlor. Low sloping, furrow irrigated fields had low sediment concentrations and low pesticide runoff concentrations for more tightly sorbed pesticides, but not for less sorbed pesticides. Runoff extraction was not significantly different for simulated and most catchment studies.

Similar runoff extraction ratios were due to similar hydrology and limited sediment concentrations. Different runoff extraction occurs on bare soil if (a) pesticides are leached from the runoff-mixing layer, requiring sorption coefficients less than two and significant infiltration, and no interflow, (b) sediment concentrations are either low (<2 g L⁻¹) or high (>100 g L⁻¹) and (c) pesticides have different concentration profiles in the runoff-mixing layer.

Conditions studied apply for croplands in the North American mid-west on silty soils and for Australian clay soils.

有些农药比其他农药流失得更多吗？农药径流如何随农药特性变化？

提高对农田农药径流的了解。

使用了来自三项澳大利亚降雨模拟研究和三项降雨模拟以及北美农田五项流域研究的表层土壤和径流浓度。事件平均径流浓度与表层土壤浓度之比即为径流抽取率。

农药径流浓度与降雨开始时土壤表面浓度密切相关。 13 种具有多种特性的农药在缓坡 (0–3%) 上的径流提取率没有显着差异，但 3 种农药的径流提取率明显较低。在较陡的斜坡上，莠去津的径流提取量明显较高，但草甘膦和异丙甲草胺的径流提取量较低。对于吸附较紧密的农药而言，低坡度、沟渠灌溉田的沉积物浓度和农药径流浓度较低，但对于吸附较少的农药则不然。模拟研究和大多数流域研究的径流提取没有显着差异。

相似的径流提取率是由于相似的水文和有限的沉积物浓度。如果 (a) 农药从径流混合层中浸出，要求吸附系数小于 2 且渗透显着，且无互流，(b) 沉积物浓度较低 (<2 g L ⁻¹）或高（>100 g L ^-1）和（c）农药在径流混合层中具有不同的浓度分布。

研究的条件适用于北美中西部粉质土壤和澳大利亚粘土的农田。