包头大气可吸入颗粒物中Ce的环境行为与细胞毒性研究

The exploitation and utilization of rare earth elements (REEs) is having more impacts ever on the environment and human health. Therefore, the study on the environmental behavior and health risk assessment of REEs in mining areas has become a major need of the national basic research. A variety of studies focusing on the concentration, transformation and toxicity of REEs in different environmental components had been carried out in past. Yet it is still insufficient and remains controversial. In particular, the research on the existing forms of REEs in inhalable particulate matter (AIP) and their exposure toxicity on human beings are still missing. This project intends to select Baotou city (including the Bayan Obo mine and tailings area) in Inner Mongolia of China as the study area. The Andersen cascade impactor, combined with techniques such as SEM, XRD, EXAFS will be utilized to characterize the Ce’s exposure level, binding forms, size distribution, seasonal variation and spatial migration in AIP in both time dimension (different seasons) and spatial dimension (different sources). By conducting in vitro exposure experiments, we will also study on the toxical effects of Ce in AIP on human bronchial epithelial cells (16HBE) and murine alveolar macrophages, discussing the relationship between its concentration, formation and its toxicity. The results will not only enrich the database of the contents, existing forms and toxicity of REEs in atmosphere, but also can provide a direct basis for assessing the human health risk of REEs in mining area.

随着稀土开发利用对环境与健康影响的途径、范围和程度日益增加，矿区稀土元素的环境行为与健康风险研究已成为国家基础研究的重大需求。过去对环境各要素中稀土含量、迁移转化及毒性等方面已开展大量研究，但有很多不足和争议之处，特别是人群呼吸暴露的大气可吸入颗粒物(AIP)中稀土的赋存状态及毒性效应研究几乎空白。本项目拟选择内蒙包头市(含白云鄂博矿区及尾矿区)为研究区，从时间(四个季节)和空间(四个区域)两个维度，利用Andesen九级颗粒物分级采样器，结合SEM、XRD、EXAFS等原位技术及大气模型模拟，表征AIP中Ce的暴露水平、结合形态、粒径分布、季节变化和空间迁移；并通过体外暴露实验，探讨AIP中Ce对支气管上皮细胞16HBE、小鼠肺泡巨噬细胞的毒性效应，揭示其浓度和形态与毒性关系。研究成果将不仅丰富大气环境中稀土含量、存在形态和基础毒性的数据库，而且可为矿区稀土人体健康风险评估提供直接依据。

本项目选择内蒙包头市(含白云鄂博矿区及尾矿区)为研究区，在2016-2018年的不同季节和不同类型区域（白云鄂博矿区、包头工业区、包头市区、包头居住区）两个维度，采集了大气可吸入颗粒物（九级粒径）样品，表征了大气可吸入颗粒物中稀土元素（重点关注Ce）的暴露水平、结合形态、粒径分布、季节变化和空间迁移。并通过体外暴露实验，将人肺上皮细胞(A549)暴露于不同浓度水平的包头大气可吸入颗粒物和标准颗粒物1649b暴露液中，测定了暴露24 h后的细胞活性以及暴露3 h 后的细胞内活性氧产生水平和DNA 双链损伤程度。研究结果表明：1）包头典型稀土矿地区春季颗粒物污染水平高于夏季；大气颗粒物中以粒径>2.5µm的颗粒物分布为主；白云鄂博矿区的PM10和PM2.5质量浓度最低，工业区的PM10和PM2.5质量浓度最高；从区域分布看，工业区大气颗粒物中重金属污染浓度最高，白云鄂博矿区浓度最低，这源于多年强风干燥气候所致。但就颗粒物本身组成来看，其PM10及PM2.5上的重金属及稀土元素浓度均处于较高的水平，是重要的污染源。2）包头春、夏季大气PM10、PM2.5及SRM1649b 均引起A549 细胞活性下降，并诱导细胞内ROS 生成量增加，造成显著的细胞内DNA 损伤。含REEs 的大气颗粒物毒性显著高于标准颗粒物；与春季相比，包头夏季大气可吸入颗粒物对细胞活性的抑制程度更高，可造成更多的DNA 双链损伤，表现出更强的细胞毒性和遗传毒性；包头大气可吸入颗粒物中呈现明显的轻稀土元素富集，铈(Ce)、钷(Pm)、镧(La)和钕(Nd)含量占稀土总量的50%以上。LREEs 均与细胞活性和细胞内ROS 产生水平呈负相关性。包头春季和夏季大气可吸入颗粒物中稀土元素含量的差异是导致包头大气可吸入颗粒物细胞毒性效应不同于标准颗粒物且具有季节性差异的原因之一。本项目的研究成果不仅丰富了稀土矿区大气环境中稀土含量、存在形态和基础毒性的数据库，而且可为矿区稀土元素人体健康风险评估提供重要参考。