农地排水中水溶性重金属浓度及其与土壤性状的关系研究

Concentration of Soluble Heavy Metals in Farmland Drainage and Its Relationship with Soil Properties

为了解农地排水中重金属浓度的变化特点及影响因素,从杭州市选择了代表性水田、果园、蔬菜地和苗木地等4种利用方式的农地,采样分析了暴雨产生的地表径流中水溶性镉、钴、铬、铜、铁、镍、铅、锌和锰的含量,并与城区地表径流中重金属状况进行了比较。分析结果可知,暴雨期间农地地表径流中不同种类的水溶性重金属浓度有较大的差别,平均浓度从低到高依次为镉(0.19μg/L)、钴(0.46μg/L)、铬(1.04μg/L)、镍(1.73μg/L)、铅(4.98μg/L)、铜(88.47μg/L)、锌(184.52μg/L)、锰(609.52μg/L)和铁(1135.21μg/L),径流中铜、锌、锰和铁的浓度明显高于其他金属元素。除锰与铁外,农地径流中重金属浓度均较低,基本上都达到地表水环境质量I和II类水的要求。统计分析表明,地表径流中水溶性重金属浓度受土地利用方式的影响,铁与锰浓度在水田径流中最高,铜浓度在果园径流中最高,镉、钴、铬、镍、铅与锌浓度在城区径流中最高。相关性分析表明,地表径流中重金属浓度主要与土壤酸碱度有关,与土壤pH呈显著的负相关,与土壤中相应重金属全量和水溶态含量呈显著的正相关,但与土壤阳离子交换量、有机质含量和粘粒含量相关不明显。地表径流中重金属含量高低主要受土壤重金属污染程度和pH影响,正常农田地表径流中的重金属浓度不会对地表水质产生明显的影响。

To understand the change characteristics of heavy metal concentrations in farmland drainage and their influencing factors,the representative farmlands of paddy field,orchard,vegetable field and nursery field were selected from Hangzhou.The authors sampled and analyzed the concentrations of water-soluble cadmium,cobalt,chromium,copper,iron,nickel,lead,zinc and manganese in the runoff drainage caused by rainstorm,and compared them with the status of heavy metals in urban runoff drainage.The analysis results showed that the soluble concentrations of different kinds of heavy metals in the farmland runoff water during the rainstorm were quite different.The average concentrations of the metals were as follows:cadmium(0.19μg/L)