土壤和沉积物中的聚合有机质对多环芳烃分布和提取的影响

为了研究土壤和沉积物中凝聚型有机碳(碳黑、干酪根)的含量及其对多环芳烃(PAHs)分布和提取的影响,分别用三氟醋酸(TFA)和在375℃下通氧燃烧的方法从珠江三角洲2个污染土壤和5个河口沉积物样品中提取酸非水解有机碳(NHC)和碳黑(BC);用索氏抽提法和不同溶剂的加速溶剂萃取法(包括连续加速萃取法ASESum和标准溶剂萃取法ASESTD)抽提土壤和沉积物中的多环芳烃,并在不同温度梯度(25℃到150℃)下用水为溶剂加速溶剂萃取其水溶态.结果表明,1)NHC是珠江三角洲土壤和沉积物中总有机碳的重要组成部分,NHC碳明显高于BC碳,NHC和BC分别占土壤和沉积物中有机碳的25.6%￣73.8%和4.64%￣17.3%.2)3种有机溶剂(丙酮、甲苯1、甲苯2)连续抽提的PAHs含量是索氏抽提的2.11倍;5种ASE方法(丙酮、甲苯1、甲苯2、ASESum、ASESTD)提取的PAHs含量与NHC含量存在明显的相关性,而且比PAHs含量与BC或无定型有机碳(AOC)含量的相关性更明显.3)在不同温度梯度下水溶态PAHs浓度符合Van’tHoff方程.研究说明除了BC外,非水解有机碳对土壤和沉积物中PAHs的分布和提取具有重要影响.

Effect of Condensed Organic Matters on Distribution and Extraction of PAHs in Soils and Sediments

The nonhydrolyzable organic carbons(NHC)and black carbons(BC)in two contaminated soils from the Guangzhou urban area and five sediments from the estuary of Pearl River were measured using trifluoroacetic acid and hydrochloride acid method, and the combustion method at 375℃, respectively. The PAHs were extracted respectively by Soxhlet extraction and different accelerated solvent extraction(ASE),and repeatedly by water ASE with different temperature steps ranging from 25℃ to 150℃. The results showed that NHC and BC account for 25.6%~73.8% and 4.64%~17.3% of total organic carbons in the soils and sediments, respectively. The PAHs content measured with the sequential three solvent ASE is over two times that measured with the Soxhlet extraction. The relationships of the PAHs contents extracted by the five extraction methods with the NHC contents are very significant, and are better than those with the BC contents and the amorphous organic carbon contents. The PAHs concentrations measured at various temperature steps fit well to the van't Hoff equation. The investigation indicates the important effect of NHC, besides BC, on the extraction and distribution of native PAHs in the investigated field soils and sediments.