生物碳对焦化场地多环芳烃的吸附-固定作用和微生物降解影响研究

In recent years, the abandoned coking areas are increasing, and their soil pollution has been paid more attention. Polycyclic aromatic hydrocarbons (PAHs) are representative toxic persistent organic pollutants in soils at coking areas, with high residual concentrations, which poses a great risk to human health and ecological environment. Therefore, PAHs contaminated soils in abandoned coking areas urgently need to be remediated. Applications of the present remediation methods are limited because of their high costs, low efficiencies or secondary contaminations. In this project, laboratory simulation experiments on remediation of PAHs contaminated soils by combination of biochars and microorganisms will be carried out. We are to investigated sorption-immobilization of PAHs by biochars, biodegradation of PAHs by indigenous microorganisms, remediation of PAHs contaminated soil by combination of biochars and microorganisms, and the impacts of soil components, heavy metals and environmental factors on above remediation processes. Finally, interaction mechanisms for remediating PAHs contaminated soils will be explained from the aspects of properties and structures of biochars/components, and the variations of microbial biomass and the activities of degrading enzymes. The successful implementation of this project will provide scientific evidence for using the combination of biochars and microorganisms to remediate high concentration of PAHs contaminated soils rapidly, efficiently and environmental friendly. Therefore, this project has important theoretical significance and practical value.

近年来，废弃焦化场地增多，其土壤污染问题已经引起人们的关注。多环芳烃(PAHs)是焦化场地的特征毒害有机污染物，残留浓度相当高，对人体健康和生态环境构成巨大威胁，亟需治理。但现有修复PAHs污染焦化场地的方法因价格昂贵、见效缓慢及易导致二次污染等问题使推广应用受限。本项目拟将具有广阔应用前景的生物碳与微生物联合起来用于修复PAHs污染焦化场地，采用实验室模拟土壤修复方法，研究生物碳对土壤中PAHs的吸附-固定作用；土著微生物对PAHs的降解作用；生物碳-微生物联合修复PAHs污染土壤；土壤组分、重金属和环境因子对上述修复过程的影响。从生物碳和土壤特征的微观性质和结构，以及微生物的生物量和降解酶活性变化角度诠释生物碳-微生物联合修复PAHs污染土壤过程中的交互作用机制，以期为利用生物碳-微生物联合作用快速、高效和环境友好地修复高浓度PAHs污染土壤提供科学依据，具有重要的理论意义和实用价值。

废弃焦化污染场地(包括土焦场地)土壤不仅含有较高浓度的有机和无机污染物，而且土壤结构和地表植被遭到严重破坏，亟待进行污染修复和植被恢复。本研究利用农业废弃物(核桃壳、玉米秸秆、玉米轴和水稻秸秆)分别在不同热解温度下(HTT：250、400和600 ºC)制备生物碳，研究生物碳理化性质对焦化场地土壤中PAHs降解、重金属生物可利用性和植物生长的影响。结果表明：微生物数量和酶活性与生物碳热解温度(而不是原料)直接相关。微生物数量与脂质C显著正相关(p﹤0.01)，但与芳香族C呈负相关(p﹤0.01)。低分子量PAHs(如萘和菲)的降解率与厚壁菌门(细菌)有关，而高分子量PAHs(如芘和䓛)的降解率主要与诺克菌门(真菌)有关。盆栽试验结果表明，生物炭仅略有降低，甚至增加了EDTA混合试剂提取的重金属(Cd、Cu、Mn、Ni、Pb、Zn)。大多数EDTA混合试剂提取的重金属与生物炭灰含量之间的显著正相关。生物碳显著降低了黑麦草对重金属(除了Mn)的吸收。EDTA混合试剂提取的重金属与黑麦草吸收重金属(除了Mn)时间无显著正相关性，表明化学提取法无法可靠地预测施加生物碳的碱性土壤中大多数重金属的植物可利用性。重金属(除了Mn)和(O N)/C和H/C之间明显的负相关关系，表明在较低温度下产生的并且具有更多极性官能团的生物碳，更有效地降低碱性土壤中重金属的植物可利用性。此外，生物炭使土壤中可利用N从21.76 mg/kg减少到14.96 mg/kg，玉米秸秆和水稻秸秆生物炭将可利用P从2.14 mg/kg增加到28.35 mg/kg，而核桃壳和玉米棒的生物炭对可利用P的影响很小。生物炭使可利用K从173.58 mg/kg增加到355.64 mg/kg，这是由生物炭上的可溶性阳离子与K对土壤表面吸附位点的竞争引起的。生物炭使黑麦草的生物量从0.07 g/盆增加到0.16 g/盆，特别是400 ºC制备的生物炭效果最为显著。黑麦草的生物量与可利用K呈显著正相关，表明可利用K对本研究土壤中黑麦草生长起到关键作用。本研究结果为利用生物碳修复污染土壤和土壤植被修复提供了科学依据。