上覆水pH值和总磷浓度对含铁盐的高砷沉积物中砷迁移转化的影响

Effect of pH and total phosphorus concentration of overlying water on arsenic mobilization in the sediments containing high arsenic and iron salts

含铁盐的高砷沉积物中，上覆水pH值和总磷浓度的变化对砷迁移的影响尚不明确．以含铁盐的高砷沉积物为研究对象，通过实验观测其暴露在不同pH值的上覆水及经过不同初始pH值、不同初始总磷浓度的溶液淋洗后，沉积物中砷的迁移规律．结果表明：当沉积物暴露在pH=10和11的上覆水时，分别在第11d和第6d后，沉积物中的砷溶出速度突然增大，说明当沉积物处于强碱性上覆水环境中，碱性越强，砷的溶出速度越快、溶出量越大．从室内实验条件的角度来看，上覆水的碱化有可能会增加沉积物中砷溶出的风险．而上覆水pH值在4～8之间时，上覆水的酸碱度对沉积物砷的迁移影响较小．此外，当上覆水总磷浓度不高于0．5mg／L时，磷的竞争吸附对砷的迁移影响较小．

Effect of changes in the overlying water pH and total phosphorus concentrations on arsenic migration was unclear for sed- iments which contained high arsenic and iron salts. To figure out the rules of arsenic mobilization under different pH, initial pH and initial phosphorus concentrations, the experiments were conducted with the sediments which contained high arsenic and iron salts. Resuhs showed that： When sediments exposed to overlying water of pH = 10 and pH = 11, leaching speed of arsenic en- hanced suddenly after 11 days and 6 days, respectively. When sediments exposed to alkaline environment, stronger the alkalinity was, much quicker the leaching was,with more arsenic migration from the sediments. From the indoor experiments, lake alkalini- zation may increase the risk of arsenic mobilization from the sediments. However, there was little effect of pH which ranging from 4 to 8 on arsenic mobilization. When the concentration of phosphorus in overlying water was less than 0.5mg/L, the competitive adsorption of phosphorus had little effect on arsenic mobilization.