生物炭对沉积物中持久性有机污染物阻控的生物动力学机制与生态毒性风险评价

Sediment is an important depository of pollutants. Biochar emerged as a green environmental sorbent, and is of great potential for in situ remediation of contaminated sediments. Previous investigations regarding sequestration of pollutants in soil and water with biochar amendment mainly focused on bioavailability of pollutants. However, reduced bioavailability of pollutants does not invariably lead to decreased bioaccumulation and subsequent reduced ecotoxicity. Little is known concerning biodynamic mechanisms of sequestration of persistent organic pollutants in sediments with biochar amendment. In this project, we will focus on the sequestration capacity of surplus sludge biochar and maize straw biochar to pollutants. Two types of persistent organic pollutants including polybrominated diphenyl ethers (PBDEs) and perfluorochemicals (PFCs) are selected as target pollutants. The sediment-dwelling benthic macroinvertebrate Bellamya aeruginosa is chosen as a test species. The potential ecotoxicity of two biochars and the key factors controlling bioaccumulation and ecotoxicity of PBDEs and PFCs with biochar amendment will be investigated by using sediment bioassay to obtain optimized conditions for the application of biochar to remediation of sediments contaminated with PBDEs and PFCs and to establish biodynamic models of PBDEs and PFCs bioaccumulation in polluted sediments. This study will be of important scientific significance for understanding remediation efficacy of biochar to polluted sediments and potential ecological risks, and further providing scientific basis for the setting of long-term application to the environment.

沉积物是污染物的贮藏库。生物炭作为一种新兴绿色环境吸附剂，对污染沉积物的原位修复具有很大的潜力。以往关于生物炭对水土环境中污染物阻控的研究主要关注污染物的生物有效性，而生物有效性的降低并不必然导致生物积累减少和生态毒性降低。有关生物炭对沉积物中污染物阻控的生物动力学机制知之甚少。以剩余污泥生物炭和玉米秸秆生物炭作为研究对象，以两种典型持久性有机污染物PBDEs和PFCs为目标污染物，以沉积物栖居型底栖动物铜锈环棱螺为测试生物，采用沉积物生物测试，研究两种生物炭对铜锈环棱螺的潜在生态毒性、生物炭添加对污染物生物积累和生态毒性影响的关键因素，获得两种生物炭应用于PBDEs与PFCs污染沉积物修复的优化条件，建立污染沉积物中PBDEs和PFCs的生物积累动力学预测模型。本项目的研究对于理解生物炭修复污染沉积物的效力及其潜在生态风险具有重要的科学意义，并为生物炭环境应用规范的制订提供科学依据。

生物炭对污染沉积物的原位修复具有很大的潜力。以往关于生物炭对水土环境中污染物阻控的研究主要关注污染物的生物有效性，很少关注生态毒性风险评价。以活性污泥生物炭（ASB）、玉米秸秆生物炭（CSB）和改性复合生物炭作为研究对象，以持久性有机污染物BDE-47和PFOA为目标污染物，以铜锈环棱螺为测试生物，采用沉积物生物测试，研究单一生物炭和改性复合生物炭对的生态毒性以及生物炭对污染物生物有效性、生物积累和生态毒性的影响，获得生物炭应用于BDE-47和PFOA污染沉积物修复的优化条件，建立污染沉积物中BDE-47的生物积累动力学预测模型，探讨改性复合生物炭对Cd/BDE-47复合污染沉积物的修复成效。本研究制备的CSB性能优越，其比表面积比ASB高8.1%；其孔径比ASB小17.8%。CSB对铜锈环棱螺不具有毒性。CSB降低BDE-47生物积累和生态毒性的效果均优于ASB。本研究开发出一种对污染物吸附性能优异的KOH改性复合生物炭KCA82（玉米秸秆与活性污泥的配比为80:20），它能显著降低沉积物中PFOA的生物有效性、生物积累和生态毒性，但对铜锈环棱螺具有轻微毒性。应用KCA82修复PFOA污染沉积物时以3%小颗粒为宜。利用本研究建立的基于铜锈环棱螺摄取和消除BDE-47的相关生理学参数和沉积物地球化学参数的生物动力学预测模型可以有效地预测铜锈环棱螺体内BDE-47的积累量，从而减少沉积物生态毒性风险评价和利用生物炭进行原位修复效果评估的不确定性。KCA82对Cd/BDE-47复合污染沉积物具有较好的修复效果，可以完全消除BDE-47的生态毒性，但不能完全消除Cd的生态毒性。当同时添加5%腐殖酸和3%KCBC可同时完全封存间隙水中的Cd和BDE-47，消除它们对铜锈环棱螺的生态毒性，此研究结果对于修复重金属/有机污染物复合污染沉积物的解决方案具有重要的参考价值。