岩溶山区磷石膏堆场重金属迁移对耕地质量的影响及污染风险管控

[目的]探讨磷石膏堆场周边耕地土壤重金属含量的变化、成因及污染风险,为磷化工产业可持续发展及水土环境重金属污染的治理提供科学依据。[方法]通过对贵州省中部磷石膏堆场进行实地调查与采样开展分析和研究。[结果]磷石膏堆场排水、侵蚀冲沟水及洼地积水中Cd,Hg,As的含量都超过农田灌溉水质一类标准(水作)水质限值,特别是Cd。在磷石膏堆场周边50～300 m范围内,玉米地、蔬菜地、水稻土中Cd的含量分别超过农用地土壤污染风险筛选值的4.87～9.43倍、8.83～19.13倍和3.83～13.42倍,堆场周边旱作土主要是Cd,As,Zn的污染风险,而水稻土则主要是Cd,As,Hg,Zn的污染风险;大部分蔬菜地土壤和水稻土中Cd的含量超过农用地土壤污染风险管控值。[结论]天然降雨对露天磷石膏堆场产生的侵蚀及淋溶作用是重金属迁移的主要原因,在地表水流方向上耕地重金属污染风险随着堆场距离的增加而逐步减小。兴修排灌设施及调整种植结构是减少磷石膏堆场周边耕地重金属污染的有效途径。

Impacts of Heavy Metal Migration on Quality of Cultivated Land and Control of Pollution Risk in Phosphogypsum Yard in Karst Mountain Area

[Objective] The content changes, cause and pollution risk of heavy metals in cultivated land around phosphogypsum yard were studied in order to provide scientific basis for sustainable development of phosphate industry and remidiation of water or soil heavy metal pollution.[Methods] Researches and analyses were carried out by field investigation and sampling of the phosphogypsum yard in Central Guizhou Province.[Results] The the contents of Cd, Hg and As in the drainage of phosphogypsum yard, erosion gully water and shoal water were exceeded the water quality limit of farmland irrigation water quality, especially Cd. In the range of 50~300 m around the phosphogypsum yard, the content of Cd in corn field, vegetable field and paddy soil were respectively exceeded 4.87~9.43 times, 8.83~19.13 times and 3.83~13.42 times of the soil pollution risk screening value of agricultural land. The dry soil around the yard was mainly the pollution risk of Cd, As and Zn, while the paddy soil was mainly the pollution risk of Cd, As, Hg and Zn. The content of Cd in most vegetable soils and paddy soils exceeds the control value of soil pollution risk in agricultural land.[Conclusion] The erosion and leaching of natural rainfall on the phosphogypsum yard was the main reason for the migration of heavy metals. In the direction of surface water flow, the risk of heavy metal pollution in cultivated land gradually decreases with the increase of the distance of the yard. The improvement of irrigation and drainage facilities and the adjustment of planting structure were effective ways to reduce heavy metal pollution in cultivated land around the phosphogypsum yard.