纳米黑碳载带有机污染物在水-土介质中的迁移行为及机制研究

Nano-scale black carbon (NBC) widely exists in the environment. Recently, the potential environmental risk of NBC received more and more attention. NBC exhibits strong adsorption affinities to a number of organic contaminants and it is quite mobile in aquatic environment. Thus, NBC could adsorb the organic contaminants, facilitate their transport. However, most studies have focused on the engineering nano-materials–carried transport behavior of organic contaminants. Few studies have been carried out to examine NBC-carried transport behavior and mechanism of organic contaminants in water-soil media. In this project, NBC produced from straws and woods is selected. The objectives of this project are to examine NBC with different properties-carried transport behavior of organic contaminants (e.g. phenanthrene and bisphenol A) in saturated water-soil media, compare the NBC-carried transport behaviors under ideal solution condition and real soil solution condition, and analyze how it is affected by the properties of NBC and the related environmental factors. Based on this, the mobility and the sorption-desorption ability of NBC will also be analyzed. Microcosmic examination, mathematical model and experimental verification will be applied in this project to discuss the NBC-contaminants-soil interaction, to understand the intrinsic mechanism of NBC-carried transport behavior of organic contaminants. The outcome of this project will contribute to assessing the environmental risks of NBC and predicting the fate of organic contaminants in water-soil environment.

纳米黑碳在环境中来源广泛，其潜在环境风险日益受到关注。纳米黑碳良好的迁移性和吸附性，使其具备载带污染物在环境中迁移的能力。目前，有关纳米颗粒载带污染物迁移行为的研究多局限于工程纳米材料，对纳米黑碳的相关行为鲜有报道，纳米黑碳载带污染物迁移的作用机制尚不明确。本项目拟选取秸秆和木本来源的纳米黑碳，研究不同性质的纳米黑碳载带有机污染物（以菲和双酚A为模型污染物）在饱和水-土介质中的迁移行为，并比较理想溶液体系和真实土壤溶液体系中纳米黑碳载带污染物迁移行为的差别，分析纳米黑碳的性质和相关环境因素对其载带污染物迁移能力的影响。在此基础上，综合纳米黑碳自身的迁移性能及其对污染物的吸附解吸性能，以微观表征、数学模型与实验验证相结合的方式，深入探讨纳米黑碳-污染物-土壤介质之间的相互作用，揭示纳米黑碳载带污染物在水-土介质中的迁移机制，为全面评价纳米黑碳的环境效应和准确预测污染物的迁移归宿提供科学依据。

纳米尺度的黑碳，即纳米黑碳，是黑碳在环境中的重要存在形式，纳米黑碳的小尺寸和高比表面积使其环境行为与常规尺度的黑碳显著不同，其潜在环境风险已受到越来越多的关注。该项目以不同温度下制备的水稻秸秆来源的纳米黑碳为研究对象，分析并比较了纳米黑碳和常规黑碳以及溶解性黑碳的性质区别；探究了纳米黑碳对有机污染物的吸附机制；探讨了纳米黑碳自身的迁移规律；结合有机污染物自身的迁移规律，模拟计算了纳米黑碳载带有机污染物的迁移行为。该研究发现，与原始黑碳的蜂窝结构不同，纳米黑碳呈现堆叠的碎片或颗粒状，平均粒径为99±3.5 nm。不同制备温度下的纳米黑碳在形态上没有明显的区别，其含氧官能团的量随着温度的升高反而降低。纳米黑碳对有机污染物有较强的吸附能力。与原始黑碳相比，纳米黑碳对有机污染物（如菲、双酚A）的吸附线性更强。纳米黑碳对有机污染物的吸附以疏水性作用为主，此外，π-π电子供受体作用和H键作用也在其中起重要作用。纳米黑碳本身迁移性强。水化学条件和多孔介质的性质可影响纳米黑碳的迁移性。如水环境中的二价阳离子和低pH可降低纳米黑碳的迁移性，多孔介质中如含有羟基氧化铁、粘土等成分，可造成纳米黑碳的迁移迟滞。环境中的有机污染物极易在土壤上吸附，其本身的迁移性较差。当有机污染物与纳米黑碳在环境中共存时，污染物可富集在纳米黑碳上，与纳米黑碳发生共迁移，从而导致污染物的迁移能力大幅度提高。该项目研究成果科学预测有机污染物在水-土环境中的迁移规律及全面评价纳米黑碳的环境生态风险提供理论依据和数据支持。