焦化厂不同粒径土壤中PAHs的赋存特征

Occurrence characteristics of PAHs in different particle size of soil from a coking plant

为分析典型焦化污染场地不同粒径土壤中PAHs的累积及其与土壤有机碳含量（TOC）、比表面积（SA）等土壤性质的相关性,对北京焦化厂长期受PAHs污染的土壤进行粒度分级[P1（0.5~1.0 mm）、P2（0.25~0.5 mm）、P3（0.15~0.25 mm）、P4（0.106~0.15 mm）、P5（0.075~0.106 mm）、P6（〈0.075 mm）],测定了各粒径土壤的理化性质及土壤中USEPA优先控制的16种PAHs的浓度,探究PAHs在不同粒径土壤中的累积特征,并通过PAHs质量分数及土壤部分理化性质的曲线拟合结果分析PAHs的赋存特征。结果表明：各粒径土壤中16种PAHs均有检出,其最高质量分数大多出现在P1粒径土样,最低质量分数出现在P4、P5中。各粒径土壤中2~3（低）环PAHs、ΣPAHs16质量分数变化趋势相似,均为P1〉P2〉P3、P4、P6〉P5（P〈0.05）,4（中）、5~6（高）环PAHs趋势类似,均为P1、P2〉P3〉P6〉P4、P5（P〈0.05）。比表面积（SA）、总有机碳（TOC）、可溶解性有机碳（DOC）与各类PAHs的质量分数呈现一定的相关性,各类PAHs质量分数随SA的增大呈先增大随后减小趋势,最大质量分数所对应的SA为38~41 m2.g-1,随TOC的增加呈先减小随后增大趋势,最小质量分数所对应的TOC为7.0~8.7 g.kg-1。不同粒径土壤颗粒中,基于污染物毒性当量因子（TEF）的等效质量分数与污染物实际质量分数变化趋势并不相同,ΣPAHs16实际质量分数变化趋势为P1〉P2、P3、P4、P6〉P5（P〈0.05）,而其等效质量分数则为P1、P2、P3、P4、P6〉P5（P〈0.05）。

To investigate the accumulation of Polycyclic Aromatic Hydrocarbons （PAHs） in different particle size fraction of soil and the correlation between the concentrations and soil physicochemical property, the naturally aged PAHs contaminated soil taken from a typical coke oven plant at southeast suburb of Beijing, China, was mechanically screened and classified by particle size, Pl（0.5-1.0 mm）, P2（0.25-0.5 mm）, P3（0.15-0.25 ram）, P4（0.106-0.15 mm）, P5（0.075-0.106 mm）, P6（〈0.075 mm）. The physicochemical property parameters such as pH, specific surface area （SA）, total organic carbon （TOC）, dissolved organic carbon （DOC） and cation exchange capacity （CEC）, and concentrations of 16 priority PAHs in USEPA list were analyzed in the six particle size fractions. The results demonstrated that 16 PAHs were detected in each particle size fractions, where the highest total PAHs concentration occurred in P1 size fraction, and the lowest occurred in P4 and P5 size fraction. Low rings PAHs （2-3 carbon rings） and the total PAHs had the similar concentration changing trend, P1 〉 P2 〉 P3, P4, 〉 P5, P6 〉 P5 （p 〈 0.05）, whereas another similar trend, P1, P2 〉 P3 〉 P6 〉 P4, P5 （p 〈 0.05）, appeared at both the middle rings PAHs （4 carbon rings） and the high rings PAHs （5-6 carbon rings）. It suggested that the concentration of PAHs had depended on SA, TOC and DOC for all the six size particles. With the augment of SA, the concentration of 16 PAHs increased to a highest value, 38--41 m2·g^-1, before the decrease at the P6 size particle. As for relationship between PAHs and TOC, the concentrations of PAHs decreased to .0~8.7 g.kgl with the increase of TOC, followed by the increase at P6 size particle. Furthermore, it was revealed that the toxic equivalency factors （TEF） concentration had a changing trend P1 〉 P2, P3, P4, P6 〉 P5 （p 〈 0.05）, differing from the actual quality concentration changing trend, which was P1, P2, P3, P4, P6 〉 P5 （p 〈 0.05）.