磷输入对湖滨底泥砷形态转化及生态风险的影响

Effects of Phosphate Input on the Speciation Transformations and Related Ecological Risks of Arsenic in the Sediment of Lakeside Wetland

为探究底泥As(砷)形态转化与磷(P)的内在关联,揭示湖滨底泥中As形态和磷形态转化带来的生态风险,选取云南阳宗海湖滨湿地底泥为研究对象,通过设置上覆水不同水平磷(K 2HPO 4,以P计)输入〔ρ(P)分别为0、1、5、10、20、60 mg/L〕的短期(1~72 h)和长期(7~30 d)扰动室内模拟试验,基于底泥对磷的等温吸附模型拟合结果,探究底泥中As释放及As与磷形态转化的规律.结果表明:①短期试验中,磷输入量为0~5 mg/L时,底泥As释放量为0.004~0.009 mg/L;磷输入量≥10 mg/L时,底泥As 释放量为0.052~0.120 mg/L.②长期试验中,第7、15、30天底泥中w(TAs)平均值分别为(13.31±1.87)(10.39±0.74)(17.88±0.65)mg kg,呈先降后升的趋势.③随着磷输入量的升高,底泥中As和磷的形态均表现为由非活性态向活性态(弱酸提取态As和磷酸二钙)转化,As和磷的生物可利用性增加.研究显示,磷输入能促进底泥中As和磷由非活性态向活性态转化,增加其生物可利用性,生态风险相应增加.

Yangzonghai lakeside wetland in Yunnan Province was selected as the research object to explore the correlation between arsenic (As) transformation and phosphorus (P) in the sediment and to evaluate the ecological risks brought by the speciation transformation.The rules of As release and P transformation in the sediments were investigated via short-term (1-72 h) and long-term (7-30 d) disturbance indoor simulation experiment with various P inputs (ρ(P) was set as 0,1,5,10,20 and 60 mg/L,respectively) in the overlying water and the corresponding adsorption isotherm model fitting results.The results showed that:(1) During the short-term experiment of P input,phosphorus concentration at 0-5 mg/L,As released from sediments reached 0.004-0.009 mg/L.But when phosphorus concentration overtop 10 mg/L,As released from sediments reached 0.052-0.120 mg/L.(2) During the long-term experiment,the average total As concentration in sediment were (13.31±1.87)(10.39±0.74) and (17.88±0.65)mg kg after 7,15 and 30 d of P input,showing descending first and then ascending trend.(3) As and P in sediments were transformed to active forms (weak acid extracted As and dicalcium P) with the increase of different phosphorus concentration,leading to increased bioavailability of As and P.The study showed that P input improved As and P transformation to active forms,increasing their bioavailability thus the environmental ecological risk.