造纸废水灌溉对湿地土壤重金属累积影响及趋势评价

The effect of irrigation with paper-making wastewater on the accumulation of heavy metals and their fate assessment in wetland soil

探讨造纸废水灌溉下芦苇湿地土壤重金属累积规律,对有效利用造纸废水,防控湿地重金属污染具有重要意义.本研究以双台河口芦苇湿地土壤为研究对象,分析不同浓度造纸废水（CODCr浓度分别为：300 mg·L-1、175 mg·L-1、50 mg·L-1）灌溉下湿地土壤重金属含量的累积规律,基于重金属残留模型对土壤重金属累积量进行预测和评估.试验结果表明：1废水灌溉使土壤重金属含量显著增加,与废水浓度显著相关,芦苇生长对土壤中As、Ni、Cu含量影响较大而对Pb、Cd含量影响较小.2不同重金属在各土层垂直分布规律存在差异：As、Pb在中间层（20～40 cm）含量最高,Cd、Cu垂直分布较为均衡,Ni主要集中在土壤表层（0～20 cm）,中下层（20～60 cm）含量迅速降低.3基于重金属残留模型对土壤重金属累积量进行预测和评估,以300 mg·L-1浓度废水灌溉,重金属都出现不同程度的累积,其中10 a后Cd的累积量超过我国《土壤环境质量标准》一级标准,50 a后Pb的累积量接近一级标准.以175 mg·L-1浓度废水灌溉,各重金属均出现累积,但增长幅度较300 mg·L-1低,50 a后Cd累积量未超过一级标准.以50 mg·L-1废水灌溉时,Pb、Ni、Cu出现土壤轻度积累,50 a后未超过一级标准。

Understanding the accumulation of heavy metal in soil reed wetlands irrigated by paper making wastewater was significant to the effective utilization of paper making wastewater and the control of heavy metal pollution. This article studied the seasonal variation of heavy metal in Shuangtai estuarine reed wetland,the effects of paper making wastewater with different COD on heavy metal in the soil,and the forecast and assessment of heavy metal accumulation with the remnant model. The results showed that： 1 irrigation with paper making wastewater can increase the heavy metal content in soil. There was a significant correlation between the heavy metal content in soil and its concentration in wastewater. The reed grown had a greater influence on As、Ni、Cu but less on Pb and Cd. 2 There was a different vertical distribution between heavy metals： As、Pb were accumulated in the middle level of soil（ 20 ～ 40 cm）,the content of Cd、Cu in each solum were similar,Ni were accumulated in upper level of soil and the content of Ni was decreased gradually with the deepening of solum. 3 Every tested heavy metal could accumulate in soil with 300 mg·L- 1of COD. Af ter 10 years of irrigation,the accumulation amount of Cd in the soil exceeds the National Soil Environmental Quality Standard Class I. Pb accumulation amount was slightly less than Class I standard. Every heavy metal in the test could be accumulated less in soil with 175 mg·L- 1than 300 mg·L- 1. After 50 years of irrigation,the accumulated Cd in the soil was less than Class I standard. When irrigated with 50mg·L-,Pb,Ni,Cu accumulated lightly,and after about 50 years of irrigation,the accumulated Pb,Ni,Cu in the soil were found to be less than the Class I standard.