污染土壤和粉尘中人为成因磁信号的溯源区分及其监测污染的分子机制

Soil pollution is a serious environmental issue with fast growing industriation and urbanization in China. The monitoring, source tracing, and control of heavy metal pollution in soils is an important tasks. In recent years, environmental magnetic methods have been widely used to investigate the degree, source, scope and temporal evolution of heavy metals pollution in soils and dusts related to industrial and other human activities. However, the mechanisms are not fully understood. This project uses high-gradient magnetic separation technique to collect the magnetic particles (MPs) from polluted soils and dusts. The physical, chemical and magnetic properties of MPs are characterized by field emission scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), environemtal magnetism, and X-ray diffraction (XRD). The results will establish a database for magnetic signature of MPs emitted from various industrial and human activities. These magnetic signatures can be used to trace the origin of various anthropogenic MPs, reveal the pollution pathways, and discriminate between lithogenic/pedogenic and anthropogenic magnetic signals. Synchrotron-based X-ray microfluorescence (XRF), X-ray absorption near edge spectroscopy (XANES), and X-ray diffraction (XRD) techniques are used to identify and quantify different iron oxide minerals and heavy metals in the MPs on the micron and sub-micron scale. These results will enrich the understanding of magnetic signature of single MPs in the soils and dusts. Synchrotron-based XRF, XRD, XANES, soft X-ray magnetic circular dichroism (XMCD), and scanning transmission X-ray microscopy (STXM) techniques are introduced to reveal heavy metals-iron oxide minerals-magnetism interaction on the MPs. This study will give insight into the quantitative link between the enhanced concentration-related magnetic parameters and heavy metals in polluted soils and dusts. The establishment of relationship between magnetic parameters and heavy metals will provide new analytical and theoretical tools for environmental application of soil magnetism. Laboratory and field experiments are set up to simulate the vertical movement, redistribution and dissolution of MPs, and dynamic release processes of heavy metals in MPs in different soil type, organic matter and water regime. In situ magnetic measurement technique are used to investigate the mobilization, re-distribution, and danamic evolution of MPs. Synchrotron-based XRF, XANES, and XRD are used to resolve the mechanisms of soil process of MPs. Our results will help to develop a magnetic tracing procedure for in situ monitoring the transportation, vertical redistribution and pollution pathway of heavy metals under the influences of a wide range of environmental processes. The studies will help the understanding of basic theory in environmental magnetism and provide a basis for the magnetic methodology in soil pollution survey and environmental management.

围绕我国日益严重的土壤污染问题，探索利用环境磁学方法监测重金属污染状况，探明重金属来源与去向，明晰重金属污染过程和迁移规律等科学问题中需要解决的关键理论问题。项目利用环境磁学、扫描电镜-能谱和矿物分析等技术，探明污染土壤和粉尘中各种人为成因磁颗粒的理化特性和磁性指纹信息，建立土壤和粉尘中不同人为成因磁性颗粒的指纹数据库；采用同步辐射X-射线荧光、X-射线衍射、X-射线吸收结构谱、软X-射线磁园二色谱等前沿技术，揭示人为成因磁性颗粒中重金属-氧化铁-磁性定量关系的分子机制，阐明磁性指示重金属污染的基本理论；利用模拟示踪和同步辐射技术，探明人为成因磁性颗粒在土壤中的行为和归趋及影响因素，发展原位监测土壤中重金属污染过程和环境效应的磁示踪技术。研究结果将为土壤和粉尘中污染物溯源区分提供科学依据和方法，建立磁性监测土壤和粉尘中重金属污染的基本理论和方法体系，完善和发展环境磁学理论和方法。

项目围绕污染土壤和粉尘中人为成因磁信号及其溯源区分、人为成因磁颗粒中氧化铁-重金属的微尺度定量关系、土壤和粉尘中重金属环境行为和迁移过程磁示踪等内容，以东北重工业基地鞍山城市土壤和道路灰尘为对象，系统研究了污染土壤和灰尘中的人为成因磁性指纹信息，建立了城市土壤和灰尘磁性参数与重金属污染负荷指数(PLI)的定量关系及其空间分布规律，提出了判断土壤重金属污染程度的磁性诊断指标(磁化率和SIRM值)，为快速判断重金属污染区域和污染程度提供了方法。利用岩石磁学、XRD和SEM/EDS等技术对土壤和灰尘中不同污染来源磁颗粒(TMP)的指纹信息(包括磁性、磁性矿物类型、磁畴态等)进行了溯源区分，建立了利用磁性指纹鉴定区分污染来源的科学依据。针对不同区域和污染源中TMP的电子显微镜-能谱数据，为污染源鉴定积累了大量基础数据，成为国内外同类研究的重要参考。利用同步辐射微束技术(u-XRF、u-XANES) 分析了代表性污染土壤和典型污染源中TMP的矿物组成和重金属微区分布，明确了TMP中重金属元素-铁信号的微尺度空间分布规律，结合小波和heatmap分析揭示了氧化铁矿物-重金属的相互作用机制及其污染物溯源区分的新途径。建立的同步辐射结合多尺度和heatmap综合分析为鉴定和定量不同污染来源磁信号提供了新方法。发现污染土壤和灰尘中TMP-重金属-黑炭具有耦合关系，土壤中黑炭含量与重金属Cr、Cd、Pb、Zn和Cu显著正相关，黑炭是重金属和TMP的载体，黑碳-重金属-磁性的空间分布具有一致性，共同反映了重金属的污染程度和空间分布规律。利用化学选择性溶解法分析了TMP中重金属的环境行为和生态风险，初步区分了重金属与铁矿物的结合形态。采用不同来源TMP污染过程和效应的磁示踪法原位动态模拟试验，阐明了人为成因TMP磁信号在环境中的动态演变规律，提出了磁性指纹信息理解重金属环境过程和归趋的新途径。项目建立了土壤和粉尘中不同人为成因磁信号指纹库，为环境中污染物溯源区分提供了依据和方法，发展了环境磁学理论和应用途径。