钨矿区尾矿及周围土壤中砷的形态与释放特征研究

In-situ status and releasing characteristics of the arsenic presence in the tailings of the tungsten mining area and its surrounding soils

为了考察赣南某钨矿尾矿砂及其周围土壤中砷的赋存状态及释放特征,通过二乙基二硫代氨基甲酸银分光光度法对尾矿砂和矿区周围土壤中的砷进行了全量分析,同时采用Tessier连续提取法和静态释放试验对不同形态的砷进行提取与分析。结果表明：尾矿砂中砷的质量比达到63.2 mg/kg,主要以残渣态的形式存在,残渣态砷占总砷的39.4%;周边土壤中砷的平均质量比达到83.83 mg/kg,已受到了严重的砷污染,土壤中砷主要以铁锰氧化物结合态的形式存在,占总砷的36.13%~38.63%;而且离尾矿砂堆越近,土壤中砷的富集越明显。尾矿砂和土壤中砷的释放能力受外界条件和体系pH值等因素的影响。经振荡处理后,尾矿砂和土壤中砷的释放量有明显提高;砷在酸性条件下的释放能力小于碱性条件下的释放能力,而且在一定范围内释放量会随pH值升高而增加。

The present paper is to report our investigation results on the in-situ status and the releasing characteristic features of the arsenic content in the tailings of tungsten mining area and its surrounding soils. For our research purpose, we have collected samples in the tailings of the tungsten mining area and its surrounding soils, in Gannan in Jiangxi and finished our analysis of all the tailing samples with arsenic content by means of spectrophotometry through diethyl dithiocarbamated silver. At the same time, we have also used Tessier sequential extraction method and done static release experiments for extracting and analyzing different concentrations of arsenic, respectively. Our results have shown that the concentration of the arsenic present in the mining tailings can likely be as high as 63.2 mg/kg, which exists mainly in the residual form. The arsenic concentration in the residual form accounts for about 39.4 of the total tailing samples. At the same time, we have also found that the average content of ar-enic can reach as high as 83.83 mg/kg in the surrounding soils, which demonstrates that the surrounding soils have also been heavily polluted. In addition, the arsenic content has also been found mainly existing in the compound form due to the oxidation of ferron and manganese in the arsenic percentage at about 36.13%- 38.63%. The study also proves that the closer is the distance of the sample from the piles of tailings, the more remarkable and noticeable the richness of arsenic is in the soil. The releasing characteristic features of arsenic in the tailings and surrounding soil have also been found influenced by the external factors besides the pH value. When strong oscillation was done with the samples, more dissolved arsenic content is likely to be found in the tailings and the surrounded soils. Thus, the releasing capability of arsenic in the acidic conditions proves less than that in alkaline conditions, when the arsenic releasing quantity tends to increase gradually with the increase of pH value within a certain range.