应用过硫酸盐氧化法预测焦化厂土壤中PAHs的生物有效性

采用过硫酸盐氧化法测定了北京市某焦化厂表层土壤中16种PAHs的生物有效性,并分析了过硫酸盐氧化前、后SOM(土壤有机质)的质量分数及其结构组成,以研究过硫酸盐氧化法预测焦化厂土壤中PAHs生物有效性方面的可行性. 结果表明:①7个供试土壤样品中w(∑PAHs)(16种PAHs质量分数之和)为10.80~249.00 mg/kg,并以HPAHs(高分子量PAHs)为主,不同环数PAHs的质量分数与w(SOM)均呈正相关,二者关系符合对数方程(R2为0.653~0.798). ②依据过硫酸盐氧化前、后土壤中w(PAHs)的变化得到PAHs的生物有效性,其中,2~3环PAHs的生物有效性平均值为0.46,略高于4环PAHs(0.22)和5~6环PAHs(0.28),较高w(SOM)及HPAHs均易引起焦化厂土壤中PAHs生物有效性的下降. ③过硫酸盐氧化前不同环数PAHs的质量分数与氧化后PAHs的残留量呈显著正相关(R2为0.991~0.994),故可利用过硫酸盐氧化前的w(PAHs)预测土壤中PAHs的生物有效性. ④与过硫酸盐氧化前相比,氧化后土壤中w(SOM)平均下降23.0%,FTIR(傅里叶变换红外光谱)分析结果显示,1 448 cm-1处吸收峰表征的脂肪碳可能是被氧化去除的软质碳的主要组分,氧化后SOM中的芳香碳相对吸光度增幅为0.88%~11.62%,可引起SOM的缩合程度加剧、憎水性增强. 因此,过硫酸盐氧化法能够作为测定焦化厂土壤中PAHs生物有效性的快速方法,可利用过硫酸盐氧化前的w(PAHs)预测土壤中PAHs的生物有效性. 

Application of Persulfate Oxidation to Predict PAHs Bioavailability in Soils at a Coking Plant Site

To assess the feasibility of persulfate oxidation for predicting the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soils polluted by the coking process, persulfate oxidation was used to determinate bioavailable fraction of 16 priority PAHs (US EPA) in surface soils from a coking plant in Beijing, China. The changes in contents and components of the soil organic matter (SOM) were investigated before and after oxidation. The results showed:1) The total concentrations of PAHs in seven test soils were between 10.80 and 249.00 mg/kg, dominated by high molecular weight PAHs. There was a significant positive correlation between the PAHs concentrations for different ring groups and the content of SOM in soils, according with a logarithmic equation (R2 values ranged from 0.653 to 0.798). 2) The bioavailability of PAHs was expressed as the ratio of oxidated PAHs concentration to initial PAHs concentration. Bioavailability of 2-3 ring PAHs was 0.46, higher than 4 ring PAHs (0.22) and 5-6 ring PAHs (0.28). High SOM content and high molecular weight of PAHs caused the decrease in PAHs bioavailability. 3) There was a significant positive linear relationship between initial PAHs concentrations and residual PAHs concentrations for different ring groups (R2 values ranged from 0.991 to 0.994). Thus, an empirical equation could be built to calculate the PAHs bioavailability based on the initial PAHs concentrations. 4) After persulfate oxidation, average SOM content decreased by 23.0%, and fourier transform infra-red (FTIR) spectroscopy showed that aliphatic carbons characterized by the absorption peak at 1448 cm-1 might be the main component of the oxidized soft carbon in soils. A slight increasing by 0.88% to 11.62% for aromatic carbon in relative absorbance values provided the evidence that the persulfate oxidation would make the residual SOM more condensed and hydrophobic. In summary, persulfate oxidation could be adopted to determine PAHs bioavailability rapidly in coking plant soils, especially using the empirical equation to predict soil PAHs bioavailability based on its initial concentration.