新型有机污染物在生物炭-根-土界面的环境行为研究

In recent years, the soil pollution by emerging organic contaminants (EOCs), such as new chemical products and pharmaceutical and personal care products (PPCPs), has been becoming more and more serious, causing serious threat to the ecological environment and human health. The study on the immobilization or removal of EOCs in soil has attracted extensive attention of science researchers and become a hotspot in environmental protection field. Biochar (BC), as an environment-friendly material may provide a new possible approach for remedying the EOCs contaminated soil because of its strong adsorption capacity for organic pollutants. In this study, BC samples were produced from different biomass feedstocks at a series of temperature, and were crushed and screened into the different size of particles. The designer BCs with different pore structure or rich special functional group were also prepared using different modification methods (e.g., activation, coating) to investigate the sorption characteristics of different EOCs on these BCs and the BCs-amended soils polluted with EOCs. We focused on the environmental behaviors of EOCs, including adsorption, desorption, leaching and degradation, in the BC-root-soil interface, and evaluated the bioavailability of EOCs in the EOCs polluted soils amended with the BCs. The study can be useful for understanding the interactions among EOCs, BC, soil and plant, and provide important theoretical data for developing the BC-based remediation technology for the EOCs polluted soils.

近年来，土壤环境中以新出现的化工产品和药物及个人护理品为代表的新型有机污染物（Emerging organic contaminants，EOCs）的污染日益严重，对生态环境和人类健康造成了严重的威胁。有关土壤EOCs污染控制、去除及相关机制的研究已成为当前环境领域的研究热点。对有机物具有强吸附能力的新型环保材料生物炭（Biochar，BC）的出现，为土壤EOCs污染控制提供了新的途径。本项目拟以不同生物质为原料，调控热解温度、活化和改性方法制备不同孔隙结构、富含特殊官能团的BC，研究其对EOCs的吸附特性，筛选可有效吸附EOCs的功能化BC；重点研究EOCs在BC-根-土新界面的吸附、解吸、淋溶和降解等环境行为，评估BC对土壤中EOCs生物有效性的影响。以上研究将有助于深入理解EOCs、BC、土壤及植物间的相互作用，为最终建立适用于土壤EOCs污染控制的BC技术提供重要理论依据。

本项目主要研究了生物炭的老化及其输入下土壤有机污染物的环境行为，取得了一些创新性成果，主要包括：.① 明晰了不同热解温度制备生物炭对微囊藻毒素（MCLR）的吸附机制，低温生物炭（≤ 400 °C）碳质组分对MCLR的吸附机制归因于其含氧官能团与MCLR的相互作用，而高温生物炭（≥ 500 °C）碳质组分对MCLR的吸附机制则为疏水作用力和π–π作用。高温生物炭具有发达的介孔结构，对MCLR表现出良好吸附能力，最大吸附容量达40 mg/g以上；.② 明确了典型根系分泌物低分子量有机酸对生物炭的老化作用，发现低分子量有机酸老化对生物炭吸附有机磷农药的促进作用，碳质组分表面暴露和孔隙结构改善是对有机磷农药吸附能力提高的关键机制；.③ 揭示了生物炭微纳米颗粒的产生途径，包括生物质热解过程中孔隙坍塌、炭壁破损，机械粉碎和环境中风化老化的物理破损。生物炭的无定型碳质组分相比于石墨化碳质结构更容易发生物理破损，形成生物炭微纳米颗粒。静电吸引驱使生物炭纳米颗粒与针铁矿、赤铁矿发生异相团聚，但不与负电荷的高岭石、蒙脱石相互作用。生物炭大颗粒、微纳米颗粒均可显著降低黄瓜对磺胺甲恶唑的吸收，机制为生物炭具有强的吸附能力。. 这些研究成果的产出，为功能化生物炭产品的研发和生物炭在土壤有机污染物修复中的应用提供了重要的理论依据。