焦化污染土壤有机质不同组分中多环芳烃分布及其生物有效性分析

The analysis in distribution and bioavailability of polycyclic aromatic hydrocarbons in organic matter components of coking contaminated soil

土壤有机质(SOM)是影响土壤中多环芳烃(PAHs)赋存的重要因素,本文对3个地区的PAHs污染土壤,将其分为土壤轻组分(LF)、重组分(HF)以及另外3个有机质组分(松散结合的腐殖质(H_(1))、稳定结合的腐殖质(H_(2))和紧密结合的腐殖质(H_(3))),采用过硫酸盐氧化法间接测定土壤中16种PAHs的生物有效性,分析了氧化前、后土壤分离的各组分之间PAHs的浓度以及其结构组成.结果表明:(1)LF中PAHs浓度为226.51~11240.40 mg·kg^(-1),HF则为29.81~1506.00 mg·kg^(-1),虽然LF占总样品的质量百分比仅为1.41%~2.43%,所含的PAHs占土壤中PAHs总量的13%~17%,LF富集PAHs的能力要远大于HF;(2)原土中2~3环的PAHs生物有效性为0.48~0.81,均值为0.68,略高于∑PAHs均值(0.67)、4环(0.55)以及5~6环(0.30);而HF中4环PAHs生物有效性为0.58~0.68,均值为0.61,略高于∑PAHs均值(0.56)、5~6环(0.45)以及2~3环(0.60),原土中PAHs生物有效性均值要比HF高,低环PAHs生物有效性要高于高环.(3)对比HF和LF,FTIR(傅里叶变换红外光谱)分析结果显示,LF比HF在波长为1033 cm^(-1)处相对吸光度明显增加,增幅为11.41%~22.62%,而在3500~3300 cm^(-1)处LF比HF相对吸光度则略有下降,降幅为1.57%~16.36%,因而LF中含C—O官能团的物质较多,表明LF比HF含有更多的碳水化合物以及高度聚合物等,导致LF中所含的PAHs要远高于其他组分,而HF中的PAHs多分布于H_(3)中,可能是由于H_(3)中存在较高的疏水性有机质.在对PAHs污染土壤修复治理以及健康风险评估中,应重视土壤LF组分及其所含PAHs生物有效性规律以及PAHs污染严重时HF中PAHs可能存在较多的情况,土壤中有机物成分显著影响土壤中PAHs的分布和生物利用度这一事实可用于PAHs污染的土壤.

Soil organic matter(SOM) is an important factor which affects the occurrence of polycyclic aromatic hydrocarbons(PAHs) in the soil. In this paper, the PAHs contaminated soils from three regions were divided into light component(LF), heavy component(HF) and three other organic matter components(loosely bound humus(H_(1)), stable bound humus(H_(2)) And tightly bound humus(H_(3))). The bioavailability of 16 PAHs in soil was determined using the persulfate oxidation method. The contents of PAHs and their structural compositions in various components of soil before and after oxidation were analyzed. The content of PAHs in LF was 226.51~11240.40 mg·kg^(-1), while that of HF was 29.81 ~1506.00 mg·kg^(-1). Although the mass percentage of LF in the total sample was only 1.41%~2.43%, the PAHs content in LF account for 13%~17% of the total amount of PAHs in soil. The ability of LF to enrich PAHs is much greater than that of HF. The bioavailability of PAHs of 2~3 rings in the original soil was 0.48~0.81, with an average value of 0.68, which was slightly higher than the mean value of ∑PAHs(0.67), 4 rings(0.55) and 5~6 rings(0.30). Four rings PAHs in HF shows a bioavailability of 0.58~0.68, with the average value being 0.61, which was slightly higher than the average value of ∑PAHs(0.56), 5~6 ring(0.45) and 2~3 ring(0.60). The average bioavailability of PAHs in the original soil was higher than that of HF. The bioavailability of low-loop PAHs was higher than that of high-loop PAHs. Comparing HF and LF, Fourier Transform Infrared Spectroscopy results showed that the relative absorbance of LF at 1033 cm^(-1) is significantly higher than that of HF, with an increase of 11.41%~22.62%, while LF showed a relatively higher absorbance than HF at 3500~3300 cm^(-1). The absorbance decreased slightly from 1.57% to 16.36%. Therefore, there are more C—O functional groups in LF, indicating that LF contains more carbohydrates and higher polymers than HF, resulting in more PAHs enriched in LF. PAHs in HF are mostly distributed in H_(3), likely due to the high content of hydrophobic organic matter in H_(3). During the remediation of PAHs contaminated soil and health risk assessment, attention should be paid to the LF components of the soil and the bioavailability of the PAHs contained therein. When PAHs is seriously polluted, there may be more PAHs in HF. The fact that the organic matter components in the soil significantly affected the distribution and bioavailability of PAHs in soil can be used to help remediate PAHs-contaminated soil.