Institute of Natural Resources and Agrobiology of Salamanca (IRNASA-CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain.
Institute of Natural Resources and Agrobiology of Salamanca (IRNASA-CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain.
Sci Total Environ. 2019 Feb 25;653:1301-1310. doi: 10.1016/j.scitotenv.2018.11.015. Epub 2018 Nov 5.
A laboratory study was designed to assess the following: i) the degradation kinetics of chlorotoluron and flufenacet at two different temperatures, 6 °C and 16 °C, in an unamended agricultural soil and one amended with spent mushroom substrate (SMS) and green compost (GC), and ii) the formation of the main metabolites of both herbicides with potential risk for water pollution over degradation time. The aim was to determine the dependence of these herbicide degradations on temperature (Q factor) using kinetic parameters, which is essential information for the later simulation of herbicide environmental fate with FOCUS models. SMS and GC were applied in situ to the natural soil as organic amendments at rates of 140 or 85 t residue ha, respectively. Unamended and amended soils were taken from the 0-10 cm topsoil of experimental plots (three replicates/treatment) located on an agricultural farm. Samples of soil + herbicides were incubated at 6 °C or 16 °C under laboratory conditions. The degradation curves of chlorotoluron and flufenacet were fitted to single first-order and first-order multicompartment kinetic models, respectively. The flufenacet degradation, the more hydrophobic herbicide, was slower than that of chlorotoluron in all the treatments. The application of the organic amendments to soil increased the half-lives (DT) for both herbicides incubated at 6 °C (1.3-1.9 times) and 16 °C (1.4-1.9 times) due to their higher sorption and lower bioavailability for degradation in amended soils. The herbicides recorded a faster degradation at 16 °C than at 6 °C (Q = 1.9-2.8) due to the increased microbial biomass and/or activity with temperature. The metabolites desmethyl chlorotoluron, flufenacet ESA and flufenacet OA were detected in all the soil treatments at both incubation temperatures. The determination of Q factors in amended soils is very valuable for generating accurate input data for pesticide fate models such as FOCUS in order to improve the evaluation of the leaching of herbicides and their transformation products, which is a relevant goal to maintain the sustainability of agricultural systems.
设计了一项实验室研究，以评估以下内容：i）在未经改良的农业土壤和添加用过的蘑菇基质（SMS）和绿肥（GC）的土壤中，氯氟脲和氟磺胺草醚在两个不同温度（6°C 和 16°C）下的降解动力学，ii）在降解过程中随着时间的推移形成对水污染有潜在风险的两种除草剂的主要代谢物。目的是通过动力学参数确定这些除草剂降解对温度的依赖性（Q 因子），这对于使用 FOCUS 模型模拟除草剂环境命运至关重要。将 SMS 和 GC 以 140 或 85 t 残渣/公顷的速率分别作为有机肥料原位施用于天然土壤中。未改良和改良土壤取自位于农田上的实验地块的 0-10 cm 表土（每个处理 3 个重复）。土壤+除草剂样品在实验室条件下于 6°C 或 16°C 下孵育。氯氟脲和氟磺胺草醚的降解曲线分别拟合为单一级和一级多室动力学模型。在所有处理中，疏水性更强的除草剂氟磺胺草醚的降解速度均慢于氯氟脲。有机肥料的施用增加了在 6°C（1.3-1.9 倍）和 16°C（1.4-1.9 倍）孵育的两种除草剂的半衰期（DT），因为它们在改良土壤中具有更高的吸附性和更低的生物降解性。由于温度升高导致微生物生物量和/或活性增加，与在 6°C 相比，除草剂在 16°C 下的降解速度更快（Q=1.9-2.8）。在所有土壤处理中，在两个孵育温度下均检测到代谢物去甲基氯氟脲、氟磺胺草醚 ESA 和氟磺胺草醚 OA。在改良土壤中确定 Q 因子对于生成农药命运模型（如 FOCUS）的准确输入数据非常有价值，以便改进对除草剂及其转化产物淋失的评估，这是维持农业系统可持续性的一个相关目标。
