冻融循环和长期放置对西南喀斯特地区土壤中多环芳烃解吸行为的影响

Effects of freezing-thawing cycle and long-term placement on PAHs desorption behavior in soil of Southwest China karst area

土壤是多环芳烃(PAHs)的主要环境汇集库,而PAHs的解吸和生物有效性主要受土壤与PAHs相互作用以及自身理化特性等的影响。自然界冻融循环和长期自然作用过程对西南喀斯特地区土壤中PAHs的解吸行为的影响仍不清楚。本研究选取西南喀斯特地区两种典型土壤(黄壤和石灰土),选取菲和芘为代表性PAHs化合物,在实验室中模拟冻融循环和长期放置两种环境过程对土壤中PAHs解吸过程的影响。结果表明:冻融循环和长期放置显著影响土壤对PAHs的解吸行为,在这两个过程中土壤颗粒结构和孔隙等发生变化,可能改变土壤颗粒与污染物的作用方式和作用强度,导致深入土壤吸附态PAHs分子与水溶液隔离,致使其解吸能力下降甚至被锁定;冻融循环和长期放置下,西南喀斯特地区土壤中PAHs的解吸速率与其疏水性呈显著负相关。

Soil is the main sink of hydrophobic organic pollutants(PAHs).Desorption and bioavailability of PAHs are mainly affected by the interaction strength between PAHs and soil,as well as their physical and chemical properties.The effects of natural freezing-thawing cycle and long-term placement on desorption of PAHs in soil of Southwest China karst area are still unclear.In this study,we examined the effects of two environment processes of freezing-thawing cycle and long-time placement on the desorption behavior of PAHs(phenanthrene and pyrene)in two typical soils(yellow soil and limestone soil)in Southwest China karst area.The results showed that the freezing-thawing cycle and long-term placement significantly affected the desorption behavior of PAHs in soil,probably because due to the changes of soil particle structure and pores.Such changes may alter the interaction mode and intensity between soil particles and pollutants,change the isolation of adsorbed PAHs molecules from aqueous solution,and lead to the decrease of desorption ability and even being locked.Under the freezing-thawing cycle and long-term placement,the desorption rate of PAHs in Southwest China karst soil had a negative correlation with its hydrophobicity.