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环境化学

Influence of dissolved organic matter on the desorption kinetics of phenanthrene in a soil-water system

基金项目：国家自然科学基金项目(No.40428005,40332015);国家重点基础研究发展计划(973)项目(No.2002CB410810,2007CB407301/3)

摘要：土壤解吸过程是影响污染物生物有效性和土壤修复的重要因素.采用人工添加方法制备加菲(PHE)老化1个月的土壤,考察水-土体系中溶解有机质(DOM)对PHE解吸动力学的影响和相互关系.结果表明,DOM与PHE的解吸释放浓度表现出相似的先增后减、最后趋于平衡的动力学过程(双尾显著性水平0.000,Spearman秩相关系数0.778).PHE解吸动力学常数量级的变化范围在10^-5～10^-6 s^-1之间,而且转折变化发生在峰值释放量所对应的时间点(25h左右).另外,紫外光谱表征参数E₄/E₆<5说明解吸进入水相的DOM主要为胡敏酸,另一参数A_254,SUV的变化趋势与PHE解吸动力学过程相一致.在不同pH条件下,PHE解吸浓度的关系为:碱性>中性>酸性.因酸性条件下溶解释放的胡敏酸(DHA)发生沉淀而无法判定其与PHE释放浓度的相关性;在其它pH条件下DOM、A_254,SUV都分别与PHE的解吸浓度显著相关.这些结果说明DOM是影响PHE解吸动力学的重要因素.

Abstract：Desorption in natural soils is a vital factor affecting the bioavailability of pollutants and remediation of polluted soils.In this study,artificial addition of phenanthrene(PHE) to a soil sample with subsequent aging for 1 month was used to study the influence of dissolved organic matter(DOM) on the desorption kinetics of PHE.The results showed that the released concentrations of DOMand PHEboth initially increased,then decreased,and finally achieved equilibrium(Spearman′s correlation coefficient was 0.778 at a significance level of 0.000).The magnitude of the kinetic constant for PHE desorption ranged from 10^-5 to 10^-6 s^-1,and the break point corresponded to the time point with the highest released concentration of PHE(about 2.5 h from the beginning of desorption).In addition,the value of the UV spectral parameter,E4/E6,was less than 5,indicating that the released DOM was dissolved humic acid(DHA),and the A_254,SUVtrend was similar to the desorption kinetics of PHE.Under different pHconditions,the concentration of PHE decreased in the following order: alkaline>neutral>acidic.Under acidic conditions.the association between released DOM and phenanthrene could not be determined due to precipitation of DHA.Under the other two conditions,the amount of released DOM and the value of A_254,SUVwere closely correlated with the desorbed amount of PHE.All these results demonstrate that DOM was a critical factor influencing the desorption kinetics of PHE.