Background

Broad spectrum of activity and low potential for leaching to groundwater are important arguments for the application of the herbicide glyphosate on railway tracks. Nevertheless, certain weeds are insufficiently controlled or develop resistance, and there is also an ongoing controversial discussion about possible carcinogenicity of glyphosate. Alternatives are thus strongly desired. 2,4-D and quizalofop-P-ethyl (QE) are two selective herbicides with a complementary spectrum of activity. When used in agriculture, the compounds and their metabolites exhibit low groundwater contamination potential. Uses on railway tracks may, however, be more critical, since degradation likely is slower and mobility higher than in agricultural soils. In this study, we investigated degradation and sorption of the two active substances as well as five metabolites in three soils collected from railway tracks and in a crushed sand, used for construction works.

Results

In these railway materials, the compounds were indeed degraded slower than in agricultural soils (mean half-lives differed by a factor of 1.4–26, depending on the substance) and mobility was higher (mean sorption coefficients differed by a factor of 3–19). Half-lives and sorption coefficients were also estimated by extrapolation of data from agricultural soils, considering the organic carbon content of railway soils and agricultural soils. Estimated values were more conservative than measured values.

Conclusions

Based on our experimental data, possible leaching to groundwater is predicted to be highest for 2,4-D and quizalofop-acid, the primary metabolite of QE, moderate for 2,4-dichlorophenol, the primary metabolite of 2,4-D, but low for QE. Secondary and tertiary metabolites were formed in only low quantities. For herbicides, for which no measured parameters are available for railway soils, estimated values may also be a viable alternative for a first tier groundwater assessment.

中文翻译：

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铁路土壤中除草剂2,4- D和喹唑磷-P-乙基及其代谢产物的降解和吸附

背景

对于除草剂草甘膦在铁路轨道上的应用而言，广泛的活性谱系和向地下水淋溶的低潜力是重要的论据。然而，某些杂草没有得到足够的控制或产生抗药性，关于草甘膦可能的致癌性的讨论仍在不断进行。因此，强烈希望有替代方案。2,4- d和quizalofop-P-ethyl（QE）是两种具有互补活性的选择性除草剂。当用于农业时，这些化合物及其代谢产物显示出较低的地下水污染潜力。然而，在铁路轨道上使用可能更为关键，因为与在农业土壤中相比，其降解速度可能更慢，迁移率更高。在这项研究中，我们调查了两种活性物质以及五种代谢物在铁轨和碎砂中收集的三种土壤的降解和吸附情况，这些土壤用于建筑工程。

结果

在这些铁路材料中，化合物的降解确实比在农业土壤中要慢（平均半衰期相差1.4-26，具体取决于物质），并且迁移率更高（平均吸附系数相差3-19）。 ）。考虑到铁路土壤和农业土壤的有机碳含量，还可以通过对农业土壤的数据进行外推来估算半衰期和吸附系数。估计值比测量值更保守。

结论

根据我们的实验数据，可以浸出到地下水被预测为最高为2,4- d和喹禾灵酸，QE的初级代谢物，中度为2,4-二氯酚，2,4-的初级代谢产物d，但量化宽松率较低。二级和三级代谢产物仅少量形成。对于无法用于铁路土壤的测量参数的除草剂，估计值也可能是一线地下水评估的可行替代方案。