• 关键词：环境污染事件  贺江  重金属污染  沉积物  生态风险

• 基金项目：中央级公益性科研院所基本科研业务费专项（No.PM-zx703-201602-048，PM-zx703-201708-219）；贺江镉铊污染后评估项目（No.PM-zx024-201402-023）；广州市科技计划项目（No.201508020078）；广东省科技计划项目（No.2014A040401037，2016B020240007）

• 蓝郁
• 环境保护部华南环境科学研究所, 广州 510655

• 梁荣昌
• 环境保护部华南环境科学研究所, 广州 510655

• 赵学敏
• 环境保护部华南环境科学研究所, 广州 510655

• 马千里
• 环境保护部华南环境科学研究所, 广州 510655

• 许振成
• 环境保护部华南环境科学研究所, 广州 510655

• 苟婷
• 环境保护部华南环境科学研究所, 广州 510655

• 王丽
• 环境保护部华南环境科学研究所, 广州 510655

• 卓琼芳
• 环境保护部华南环境科学研究所, 广州 510655

• 摘要：为科学评估突发镉、铊污染事件及应急处置对贺江生态风险的影响，分别于2013年7月、11月和2014年8月采集水样和沉积物，分析重金属镉（Cd）、铊（Tl）、铅（Pb）、铬（Cr）、砷（As）、汞（Hg）、锌（Zn）、镍（Ni）和铜（Cu）的含量，并采用地积累指数法（I_geo）和潜在生态风险指数法（RI）综合评价贺江沉积物重金属的污染水平和潜在风险程度.结果表明：事件应急期间，水体中Cd含量为0.08~38.35 μg· L^-1，部分点位超地表水Ⅲ类水标准，Tl含量为0.02~0.65 μg· L^-1，除背景点（龟石水库）外其余点位均未达到生活饮用水卫生标准，其余重金属除Hg外均达到地表水Ⅲ类水标准；沉积物中Cd和Tl含量分别为1.40~68.70 mg·kg^-1和0.32~1.39 mg·kg^-1，均超过背景值（Tl除西江交汇口下游500 m点位），其余重金属在大部分点位均超背景值.事件后恢复期，水质均达地表水Ⅲ类水标准，而沉积物重金属含量均大幅降低，表明贺江水环境恢复良好.贺江沉积物中Cd在各个点位的I_geo均为最大，是主要的重金属污染物，其它重金属元素处于清洁到偏中度污染程度；Cd是贺江最主要的具有潜在生态危害的重金属污染物，其次是Hg、As、Tl、Pb和Cu，而Zn、Cr和Ni对潜在生态风险指数的贡献率较小.Cd、As、Pb和Cu元素两两之间呈显著相关，表明有相同的污染来源.本研究通过对贺江镉、铊污染事件应急处置前后水质和沉积物的生态风险进行评价，可为该流域重金属污染防治和水环境管理提供科学依据.

• Abstract：To evaluate the impacts of environmental pollution incident of cadmium and thallium and their emergency disposal on ecological risk of Hejiang River Basin, samples of water and sediments were collected in July and November 2013 and August 2014 and the contents of Cd, Tl, Pb, Cr, As, Hg, Zn, Ni and Cu were analyzed. Geo-accumulation index (I_geo) and risk index (RI) were used to evaluate the pollution level of heavy metal and potential risk in sediments. Results showed that Cd content in water ranged from 0.08 to 38.35 μg· L^-1 during the emergency period. Water quality at some sites could not meet with Class Ⅲ standard for surface water. Tl content in water ranged from 0.02 to 0.65 μg· L^-1, indicating that water quality in most sites did not meet with drinking water standards except for the background site in Guishi reservoir. Content of other heavy metals met with Class Ⅲ standard for surface water, except for mercury. Cd and Tl content in sediments ranged from 1.40 mg·kg^-1 to 68.70 mg·kg^-1 and from 0.32 mg·kg^-1 to 1.39 mg·kg^-1, respectively, both of which exceeded the background concentration except for content of Tl at the site 500 m downstream of the confluence by Hejiang River and Xijiang River). Content of other heavy metals at most sites exceeded local background concentration. During the recovery period after the incident, water quality met with Class Ⅲ standard for surface water, and a drastic decrease of heavy metal content in sediments were observed. The results indicated that good recovery occurred in Hejiang River. I_geo of Cd was the highest in all sites as it was the main heavy metal contaminant in sediments in Hejiang River, while I_geo of other elements ranged from clean level to moderately contaminated level. Cd was the main heavy metal contaminant with potential ecological hazardous in Hejiang River, followed by Hg, As, Tl, Pb and Cu, while Zn, Cr and Ni contributed less to RI. Significant correlation was found among Cd, As, Pb and Cu, which implied the same source of these heavy metals. This study provided important information for the prevention of heavy metal pollution and water and environmental management based on the assessment of ecological risk in water and sediment before and after the emergency treatment of cadmium and thallium pollution.

• Key words：environmental pollution incident  Hejiang River  heavy metal pollution  sediments  ecological risk

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