多年冻土区土壤多环芳烃污染研究进展

多环芳烃（polycyclic aromatic hydrocarbons，PAHs）是一种难降解、毒性强的致癌性污染物，其广泛分布于各环境介质中，陆地环境中90%的PAHs累积在土壤中。随着资源的开发，由油品泄漏、垃圾渗滤、污水排放等行为造成的多年冻土区PAHs土壤污染问题日益突显，并且在气候变化背景下，多年冻土中的PAHs具有重新释放而造成二次污染的风险，多年冻土区土壤多环芳烃污染分布特征和迁移规律研究对评估多年冻土区生态环境风险，防治土壤持久性有机物污染，保障广大多年冻土居民生命健康安全具有重要意义。通过回顾目前国内外多年冻土区土壤中PAHs污染的相关研究，分析发现多年冻土区未受污染的土壤中PAHs的污染水平远低于中低纬度人口密集区域，可代表地球土壤中PAHs的背景值；高纬度或高海拔的地理位置以及严寒的气候使得冻土区土壤中PAHs一个普遍且最重要的来源是大气远距离传输；活动层的冻融作用主要通过改变土壤理化性质和控制水分运移方向影响PAHs在多年冻土区土壤中的垂向分布特征，多年冻土的低渗透性具有阻碍PAHs垂向迁移的作用。综合分析已有研究成果，表明目前冻土区土壤PAHs污染研究还是大量集中于表层土壤中的污染分布调查和来源解析，而关于PAHs在活动层和多年冻土层中的垂向迁移研究还仅限于对其在土壤剖面中分布状况的解释性分析，冻融作用对PAHs在土壤中的迁移、转化和归宿的影响机制还不清楚。未来多年冻土区土壤中PAHs的研究将集中于迁移转化机理与污染治理技术两方面，针对PAHs在多年冻土区土壤中迁移行为的模拟模型亟待研究开发，以实现PAHs污染储量和迁移通量的定量预测；此外，多年冻土区土壤污染问题的深入研究还需要紧密联系多圈层、多界面、多介质、多要素以及多目标污染物而开展。

A review of polycyclic aromatic hydrocarbons pollution in soil of permafrost regions

Polycyclic aromatic hydrocarbons （PAHs） widely distributed in the environment medium， which is a strong carcinogenic persistent pollutant. About 90% PAHs in terrestrial environment accumulate in soils. With the development of resources in the cold region and the intensification of human activity， the soil pollution of PAHs in permafrost regions caused by oil leakage， landfill leach and sewage discharge has become increasingly prominent. Under the background of global warming， there is a risk of secondary pollution due to the re-release of PAHs from permafrost. The study on the distribution characteristics and migration process of soil PAHs pollution have great significance to the assessment of ecological environment risks， the prevention and control of persistent organic matter pollution in soil， and the protection of life and health safety of residents in permafrost region. In this review， we summarized the latest research on the distribution characteristic， source identification， vertical migration and risk assessment of PAHs in soil of permafrost regions. As the remote area on the earth， the pollution level of PAHs in the soil of permafrost region is much lower than that in the densely populated areas of middle and low latitudes， which can represent the background value of PAHs in the soil of the earth. Due to the high latitude or altitude and cold climate， a common and most important source of PAHs in soil of permafrost region is long-distance atmospheric transport. The freezing-thawing effect of the active layer affects the vertical distribution of PAHs in soil profile by changing the physical and chemical properties of soil and controlling the direction of unfrozen water migration. Meanwhile， the low permeability of permafrost can hinder the vertical migration of PAHs. Based on the overview of research results， it is concluded that the current research on soil PAHs pollution in permafrost region is mainly focused on the investigation of the distribution and source analysis of the pollution in the surface soil， while the research on the migration of PAHs in the deeper active layer and permafrost is only limited to the explanatory analysis of its distribution in the soil profile. The effects of freezing-thawing on the migration， transformation and destination of PAHs in soil are still unclear. In view of the problems and shortcomings of the current researches， it is believed that the future effort on PAHs in soil of permafrost region will focus on the migration and transformation mechanism and pollution control technology. The simulation model for migration behavior of PAHs in soil of permafrost region needs to be developed urgently to achieve the quantitative prediction of PAHs pollution reserves and migration flux. In addition， the in-depth study of soil pollution in permafrost regions needs to be carried out by closely associating with multi-layer， multi-interface， multi-medium， multi-factor and multi-target pollutants.