页岩气钻井液污染土壤中石油烃类污染物的生物有效性及毒性的时间变化趋势

Temporal variation in bioavailability and toxicity of petroleum hydrocarbons in soil contaminated by shale gas drilling fluids

页岩气开发有助于促进能源结构转型,了解页岩气开采过程的潜在风险对行业的可持续发展至关重要.油基钻井液含高浓度的石油烃类物质,可造成周边土壤污染,但目前对污染土壤的毒性效应知之甚少.为考察老化对页岩气开采污染土壤中典型污染物的生物有效性和毒性的影响,本研究将油基钻井液污染土壤老化至270 d,利用耗竭性萃取和Tenax萃取分析了不同时间点土壤中多环芳烃(PAHs)和烷烃总浓度和生物有效浓度,同时测试了土壤对白符跳虫的96-h致死性以及存活跳虫中富集的污染物.结果表明,油基钻井液污染土壤中PAHs主要以低环形式存在,污染物生物有效性随老化时间延长显著下降,且高环PAHs生物有效性降低更快.场地环境可检出浓度下,即使老化270 d,钻井液污染土壤仍对跳虫表现高毒性(96-h LC50为4.00%),但毒性随老化时间延长,逐步下降,且与土壤中多环芳烃生物有效浓度以及生物体内富集有机物浓度密切相关.本研究揭示了老化时间对钻井液污染土壤中主要污染物生物有效性和毒性的影响,有利于全面认识页岩气开采过程对周边土壤的潜在风险.

The development of shale gas is conducive to energy structure transformation.Understanding potential risks related to shale gas exploitation is crucial to the sustainable development of this industry.Oil-based drilling fluids contain high concentrations of petroleum hydrocarbons,which may pollute surrounding soils,but the toxicity of contaminated soil is largely unknown currently.To investigate the impact of aging on the bioavailability and toxicity of typical pollutants in soil contaminated by shale gas extraction,oil-based drilling fluid contaminated soil was aged until 270 d,and the total and bioavailable concentrations of polycyclic aromatic hydrocarbons(PAHs)and alkanes were analyzed in soils with different aging time using exhaustive and Tenax extraction.In addition,96-h lethality of the contaminated soil to springtails was examined and the pollutants accumulated in surviving springtails were also assessed.Results showed that PAHs in oilbased drilling fluid-contaminated soil mainly occurred in low-ring forms.The bioavailability of pollutants decreased with increasing aging time,and the bioavailability of high-ring PAHs decreased faster than the low-rings.At the concentrations similar to those in the shale gas extraction sites,even if aged for 270 d,soil contaminated by drilling fluid was still highly toxic to the springtails(96-h LC50 of 4.00%),but the toxicity gradually reduced with aging time.The toxicity was related to the bioavailable concentration of PAHs in the soil and body residues in organisms.The present study revealed the impact of aging time on the bioavailability and toxicity of main pollutants in drilling fluid-contaminated soil,which is beneficial to a comprehensive understanding of potential risks of the shale gas extraction process to surrounding soil.