Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
College of Resources and Environment Science, Hebei Agricultural University, Baoding, China.
Environ Pollut. 2018 Dec;243(Pt A):734-742. doi: 10.1016/j.envpol.2018.09.019. Epub 2018 Sep 11.
Soil organic matter (SOM) is the principal aggregating agent for soil aggregation and also the main adsorbent for organochlorine pesticides (OCPs) such as dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH), which may thereby affect OCP distribution in soils subjected to different land use types. However, the potential effects of land use on SOM and OCP distribution patterns in soil aggregates are not well understood. In this study, soils from farmlands and barelands in the Danjiangkou Reservoir area were analyzed to determine the influence of land use on OCP distribution and composition in different aggregate fractions (>3, 1-3, 0.25-1, and <0.25 mm). The results showed that the levels of ∑DDTs ranged from 9.01 to 27.48 with a mean of 14.40 ng g, and ∑HCHs ranged from 2.06 to 4.66 with a mean of 3.19 ng g in farmland soils. In comparison, bareland soils were less contaminated, with total DDTs and HCHs fell in the range of 0.75-5.01 ng g and not detected (n.d.)-1.40 ng g respectively. In regard to the distribution patterns in soil aggregates, the residual levels of ∑DDTs and ∑HCHs tended to a certain degree to enrich in microaggregates (<0.25 mm) relative to bulk soils. A further analysis revealed that the enrichment of ∑DDTs and ∑HCHs in microaggregates were mainly attributed to the accumulation of p,p'-DDE and β-HCH. Moreover, SOM was found also enriched in microaggregates. The enrichment of SOM was significantly and positively correlated with these of ∑DDTs, ∑HCHs, and the dominant metabolites (i.e., DDE and β-HCH) in both land use types. Such results indicated that the variations in behavior of OCPs could be linked to the processes of soil aggregate turnover. These findings may help to enrich the theory of soil OCPs sequestration and establish targeted strategies to mitigate their health risks in the environment.
土壤有机质（SOM）是土壤团聚体的主要团聚剂，也是有机氯农药（OCPs）如滴滴涕（DDT）和六氯环己烷（HCH）的主要吸附剂，这可能会影响到不同土地利用类型下土壤中 OCP 的分布。然而，土地利用对土壤团聚体中 SOM 和 OCP 分布模式的潜在影响尚不清楚。本研究分析了丹江口库区农田和裸地土壤，以确定土地利用对不同团聚体（>3、1-3、0.25-1 和<0.25mm）中 OCP 分布和组成的影响。结果表明，农田土壤中∑DDTs 水平范围为 9.01-27.48ng/g，平均值为 14.40ng/g；∑HCHs 水平范围为 2.06-4.66ng/g，平均值为 3.19ng/g。相比之下，裸地土壤的污染程度较低，总 DDTs 和 HCHs 的含量分别在 0.75-5.01ng/g 和未检出（n.d.）-1.40ng/g 的范围内。就土壤团聚体中的分布模式而言，∑DDTs 和∑HCHs 的残留水平在某种程度上趋于在微团聚体（<0.25mm）中富集。进一步分析表明，∑DDTs 和∑HCHs 在微团聚体中的富集主要归因于 p,p'-DDE 和β-HCH 的积累。此外，SOM 也在微团聚体中富集。SOM 的富集与两种土地利用类型中∑DDTs、∑HCHs 及其主要代谢物（即 DDE 和β-HCH）的富集显著正相关。这些结果表明，OCPs 的行为变化可能与土壤团聚体转化过程有关。这些发现可能有助于丰富土壤 OCPs 固定的理论，并制定有针对性的策略来减轻其在环境中的健康风险。
