低分子量有机酸作用下土壤中菲和芘的残留及形态

采用微宇宙试验方法,以菲和芘为多环芳烃(PAHs)代表物,研究了几种低分子量有机酸作用下黄棕壤中菲和芘的残留和形态。结果表明,老化60 d后土壤中菲和芘的残留含量明显减少;不施加有机酸的对照土壤中,菲和芘的残留含量为10.13和29.18 mg kg-1,去除率为87.33%和63.50%。与对照相比,供试浓度(0～64 mg kg-1)范围内,柠檬酸、草酸、酒石酸等3种低分子量有机酸作用下土壤中PAHs残留含量提高,去除率减小,表明供试条件下有机酸抑制土壤中菲和芘的降解;进一步分析发现,少量(≤4 mg kg-1)的有机酸即可对PAHs降解产生高的抑制效果。微生物降解在PAHs的去除中起重要作用,且芘比菲更抗微生物降解。供试条件下,可脱附态和有机溶剂提取态是土壤中菲和芘存在的主要形态,而结合态残留占总残留的比例很小(<8.5%)。3种有机酸均提高了土壤中可脱附态和有机溶剂提取态菲和芘的残留含量,施加有机酸使土壤中菲和芘的可脱附态含量较对照分别提高了46.67%～749.1%和1.83%～80.20%,有机溶剂提取态则提高了8.73%～375.2%和22.63%～114.3%;低分子量有机酸作用下结合态的菲和芘含量仍很小。

Effect of low-molecular-weight organic acids on residues and forms of phenanthrene and pyrene in soil

Effects of low-molecular-weight organic acids(LMWOAs) on residues and forms of phenanthrene and pyrene in yellow brown earth was investigated using a microcosm testing procedure.It was found that after 60 days of aging,the total residual concentrations of phenanthrene and pyrene in the soil decreased significantly to only 10.13 and 29.18 mg kg-1,respectively,showing a removal rate of 87.33% and 63.50% as compared with the control without the addition of LMWOAs.The test PAHs increased in residual concentration,but decreased in degradation rate with 0~64 mg kg-1 of citric acid,oxalic acid or tartaric acid added.Further investigations revealed that a small amount(≤4 mg kg-1) of organic acids was adequate to inhibit significantly degradation of PAHs in the soil.The degradation of test PAHs in the soil depended markedly on microbial activities in the soil environment.As pyrene is higher in molecular weight and complexity of structure,pyrene is more resistant to microbial degradation than phenanthrene in the soil.The PAHs in soil could be fractionated into desorbing fraction,non-desorbing fraction,and bound residue.The former two fractions were observed to be the dominant forms of the test PAHs in the soil irrespective of addition of LMWOAs.However,the addition of LMWOAs increased the concentrations and proportions of the two forms of the PAHs in the soil.It did the desorbing fractions of phenanthrene and pyrene by 46.67% ~749.1% and 1.83% ~80.20%,respectively and the non-desorbing fractions by 8.73% ~375.2% and 22.63% ~114.3%,respectively.The fractions of bound residue of the PAHs remained to be the smallest in the soil irrespective of whether organic acids were added or not.