Chiral organochlorine pesticide signatures in global background soils
Chiral organochlorine pesticide signatures in global background soils
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DOI：
10.1021/es051004c
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发表时间：
2005-11-15
影响因子：
11.4
通讯作者：
Jones, KC
中科院分区：
文献类型：
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作者：
Kurt-Karakus, PB;Bidleman, TF;Jones, KC
手性农药在土壤中经常发生对映体选择性降解。以前对手性签名的研究主要集中在经过处理的农业土壤上，而不是背景(未处理)土壤上，并出于来源解析的目的跟踪大气中的签名。在这项研究中，我们调查了来自世界各地的65个背景土壤的手性特征。从不同的生态系统(如草地、森林)采集土壤，测定了手性手性氯丹、α-六氯环己烷和o，p‘-DDT的对映体分数(EFS)。大多数土壤中的氯丹表现出农业土壤中常见的对映选择性降解模式，即(+)-反式氯丹(TC)和(-)-顺式氯丹(CC)的消耗。然而，一些样品对TC、CC和氯丹化合物MC5的对映体降解规律相反。对EFS与外消旋的偏差(DEVrac=0.500-EF的绝对值)、土壤有机质百分比(%SOM)、年平均温度以及TC与更稳定的化合物反式九氯(TN)的比率之间的相关性进行了检验。TC和CC的DEVrac与%SOM呈显著正相关(p=0.0022和0.0031)，而其他OCP的DEVrac与%SOM无相关性。没有发现任何一个有机氯农药的DEVrac与年平均温度之间存在显著的相关性。TIC的DEVrac与TC/TN呈负相关，但回归是由TC/CC高的两个点驱动的。移除这两个点会导致不显著的回归。土壤中TC、CC和a-HCH的EL‘s范围大于环境空气中的EL，这为某些情况下大气沉积后的就地降解提供了证据。土壤中的可变EFS表明，当考虑将空气中的对映体特征作为风化土壤中有机氯挥发的标志时，需要谨慎。
Chiral pesticides frequently undergo enantioselective degradation in soils. Prior studies to characterize chiral signatures have focused on treated agricultural soils, rather than background (untreated) soils, and tracking signatures in the atmosphere for source apportionment purposes. In this study, we investigated the chiral signatures in 65 background soils collected from different locations across the world. The soils were taken from different ecosystems (e.g., grasslands, forests), and the enantiomeric fractions (EFs) of chiral chlordanes, alpha-hexachlorocyclohexane (alpha-HCH), and o,p'-DDT were determined. Chlordanes in most of the soils showed the usual pattern of enantioselective degradation seen in agricultural soils, depletion of (+)-transchlordane (TC) and (-)-cis-chlordane (CC). However, some samples showed opposite enantiomer degradation patterns for TC, CC, and chlordane compound MC5. Correlations were tested between the deviation of EFs from racemic (DEVrac = absolute value of 0.500 - EF), the percent soil organic matter (% SOM), annual mean temperature, and the ratio of TC to the more stable compound trans-nonachlor (TN). Significant positive correlations were found between DEVrac and % SOM for TC and CC (p = 0.0022 and 0.0031), but not for the other OCPs. No significant correlations were found between DEVrac and annual mean temperature for any of the OCPs. DEVrac for TIC was negatively correlated with the TC/TN ratio, but the regression was driven by two points with high ratios of TC/CC. Removing these two points resulted in a nonsignificant regression. The range of El's for TC, CC, and a-HCH in soils was greater than in ambient air, providing evidence of in situ degradation after atmospheric deposition in some cases. Variable EFs in soil suggest that caution is needed when considering the enantiomer signatures in air as a marker of volatilization of weathered soil-derived organochlorines.