云南阳宗海砷污染水平、变化趋势及风险评估

云南阳宗海砷污染事件引起社会广泛关注.为了解事件发生后阳宗海砷污染水平及变化趋势,分别于2008年12月、2009年2月、5月及9月四次采样,研究了阳宗海湖水、底泥、周边井水、土壤、农作物及水生生物中的砷含量及其变化趋势.研究结果显示:湖水平均砷浓度分别为176.9、147.3、159.3和161.1μg/L(算术平均),底泥平均浓度分别为32.87、62.41、62.99和46.96μg/g(算术平均).阳宗海湖水砷浓度经历了先升后降再到平稳的变化过程,底泥砷含量迅速升高后缓慢下降,湖水和底泥间砷交换还在进行.阳宗海附近土壤中砷最高浓度为23.33μg/g,未超过国家土壤环境质量三级标准.大米、玉米、花椰菜、小油菜等农作物可食用部分中砷的最高值为0.35μg/g,均未超过国家无公害食品标准.水生植物中砷水平大多在100～200μg/g之间,最高为苦草,砷含量超过300μg/g,说明该植物对砷有一定的富集能力.虾、鱼类等可食用水生动物砷浓度范围为1.52～11.4μg/g.

The levels,trends and risk assessment of arsenic pollution in Yangzonghai Lake,Yunnan

Arsenic contamination incident in Yangzonghai Lake, Yunnan, has attracted wide attention in society. In order to evaluate the arsenic levels and temporal trends after the incident, the sampling and determination were carried out in December, 2008, February, May and September, 2009, respectively. The samples included lake water, sediment, soil, aquatic organisms and crops. The average arsenic concentrations of lake water in the four samplings were 176.9, 147.3, 159.3, 161.1 μg/L （arithmetic average）, those of the sediments were 32.87, 62.41, 62.99, 46.96 μg/g （arithmetic average）, respectively. As time goes by, the arsenic concentration of lake water in Yangzonghai increased firstly and then decreased, finally, the concentration leveled off. Meanwhile, the arsenic content of the sediment increased rapidly and then decreased slowly. The arsenic exchange between lake water and sediment is still in progress. The highest total arsenic of soil in the vicinity of Yangzonghai was 23.33 μg/g, which was lower than relevant national standard. The contents of edible parts of rice, corn, cauliflower and small cole were lower than 0.35 μg/g and the relative national standards for non-polluted food. The total arsenic levels of aquatic plants are between 100 and 200 μg/g and the highest was Vallisneria natans （Lour.） Hara, which was higher than 300 μg/g. The arsenic concentrations of fish and shrimp were1.52–11.4 μg/g （dry weight）.