活化过硫酸钠氧化土壤对挥发性有机污染物吸附特性的影响

活化过硫酸钠(Sodium persulfate,SPS)氧化技术是一种新型的土壤修复技术。为了更科学地评价化学氧化处理后土壤的环境风险,本文通过亚铁离子活化过硫酸钠法对有机质(Organic matter,OM)含量存在显著差别的两种土壤进行氧化处理,比较了活化过硫酸钠氧化前后两种土壤样品对3种挥发性有机污染物的吸附特性。结果表明,亚铁活化的SPS能够氧化土壤中腐殖酸和胡敏素类的有机质。对OM含量较高的1号土,SPS氧化对有机质的去除率为71.9%。而对OM含量较低的2号土,SPS氧化对有机质的去除率为49.9%。1号土样对3种挥发性有机物的吸附以分配作用为主,氧化后的1号土样对3种物质的吸附机制不变,但吸附量有所增加;2号土样对3种挥发性有机污染物的吸附有一定的非线性,而氧化后的2号土样对3种物质的吸附线性特征增强。吸附数据用对数形式的Freundlich方程拟合得到分配系数lg Kf值,比较有机碳标化后的分配系数lg Kfoc,氧化后的土壤有机质对3种挥发性有机污染物的吸附特性有所提高。分析表明,SPS氧化了有机质中较多的极性组分(如羧基及羟基等),从而使处理后的土壤中有机质的非极性增强,强化了对非极性化合物的吸附。

Effect of soil oxidation with reactivated sodium persulfate on sorption of volatile organic contaminants

Soil oxidation with reactivated sodium persulfate (SPS) is a new kind of in situ soil remediation technology. In order to assess scientifically the environmental risks of the chemicals to oxidized soil, two types of soils obviously different in organic matter(OM) content were oxidized with ferrous ion activated SPS and then used to explore the effects of oxidation on sorption behaviors of three volatile organic contaminants (VOCs) in the two soils. Results show that the oxidation had great effects on soil organic matter (e.g., humic acids and humins). It removed 71.9% of the organic matter in Soil No. 1, which was relatively high in soil organic matter and 49.9% in Soil No. 2, which was relatively low in soil organic matter. The sorption of the three compounds in Soil No. 1 was dominated by the mechanism of partition. Soil oxidation did not alter the dominance, but slightly increased its sorption capacity. The sorption of the three compounds in Soil No. 2 was somewhat nonlinear, implying the existence of some other sorption mechanisms. However, the sorption isotherms became more linear after oxidation. The normalized logarithm of partition coefficient of organic carbon content (lg K_foc ) was used to evaluate OM sorption capacity of the soils as affected by oxidation. Lg K_foc of the three compounds in the two oxidated soil samples were substantially higher than those in the original soil samples. The analysis indicates that activated SPS oxidized quite a portion of polar components (such as carboxyl and hydroxyl etc.) of OM so that the polarity of the OM was reduced, thus in turn enhancing its sorption of non-polar compounds.