Environment International：DGT和常规提取技术对土壤-作物系统中的农药及其...

英国兰开斯特大学环境中心Hao Zhang教授团队对5种不同性质的土壤进行了试验，比较DGT方法和两种常规提取方法对土壤中的阿特拉津（ATR）及其代谢物的测定及生物有效性的预测。相关成果发表于Environment International（IF=7.943）。

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Highlights

·DGT and two extraction approaches for sampling pesticides from soils are compared.

·This is the first research on bioavailability of organic compounds in soils using DGT.

·DGT and soil solution extracts predict bioavailable atrazine taken up by maize.

·Solvent extraction will not mimic conditions encountered in soil-plant systems.

·DGT may aid contaminated land assessment or pesticide risk assessment testing.

Abstract

Traditional extraction methods (soil solution and solvent extraction) are simple to use and conventionally employed to assess pesticide chemical form and bioavailability in soils. However, whilst convenient for regulatory testing, it has been suggested that these approaches may be too crude or are poor predictors of bioavailability, due to their arbitrary original development to detect ‘total’ concentration using exhaustive extraction. The diffusive gradients in thin films (DGT) technique has been widely used to measure chemical speciation in situ and shown to reliably predict bioavailability of a range of contaminants (e.g. heavy metals, radionuclides, nutrients) in soil systems, because it dynamically samples contaminants from/re-supplied to the soil solution phase. Experiments were therefore conducted with 5 soils of different properties to compare DGT and the two conventional extraction approaches for sampling atrazine (ATR) and its metabolites from soils and for predicting their uptake by maize tissues. After 23 days aging, a large proportion of total ATR was still available for solvent (acetonitrile) extraction and the major constituent in soils was parent ATR. The best correlations of total ATR concentrations in maize and total ATR measured in soil were with DGT and soil solution measurements. This is encouraging, in jointly supporting one of the established methodologies traditionally used in pesticide testing (i.e. soil solution) and a widely used method (i.e. DGT), which has been validated previously for a range of contaminants. The poorer performance of solvent extraction (a procedure widely used for pesticide testing) is perhaps to be expected, given that solvents will not truly mimic the conditions encountered in soil-plant systems.

传统的土壤农药提取方法（土壤溶液和溶剂萃取）使用简单，通常用于评估土壤中农药的化学形态和生物有效性。然而，这种传统的方法尽管便于测定，但有人认为其较为原始，会提取出全部待测物，从而导致结果过于粗糙，不能很好地反应生物有效性。薄膜扩散梯度（DGT）技术能够动态地测定土壤溶液中已存在或新加入的污染物，已被广泛用于土壤系统的不同情景中，来测定化学物质成分和一系列污染物的生物有效性（如重金属、放射性核素、养分）。基于此，本研究对5种不同性质的土壤进行了试验，比较DGT方法和两种常规提取方法对土壤中的阿特拉津（ATR）及其代谢物的测定，并预测了其被玉米组织吸收的情况。在进行23天老化后，使用溶剂萃取（乙腈）仍能提取出土壤中较大比例的总ATR，且主要成分为原始ATR。DGT方法和土壤溶液测定方法下玉米中总ATR浓度与土壤中总ATR的相关性均较好。这一结果表明在农药生物有效性检测方面，传统既定方法（即土壤溶液）和新的广泛使用的方法（即DGT）同样有效，这种传统方法从前曾用于一系列污染物的验证。溶剂萃取（同样是一种广泛用于农药检测的方法）的作用结果较差，可能是因为溶剂无法真正模拟土壤-植物系统中的条件。