酸性矿山废水对稻田土壤中磷形态及磷有效性的影响

选择我国西南典型喀斯特地区的稻田土壤为研究对象,通过模拟不同污染浓度酸性矿山废水(AMD)的污灌试验,分析稻田土壤磷酸铁类化合物(Fe-P)、磷酸钙类化合物(Ca-P)、磷酸铝类化合物(Al-P)、闭蓄态磷(O-P)等不同矿物形态磷及土壤总磷和有效磷的变化,并初步探讨AMD中主要污染因子pH值、Fe3+对稻田土壤磷释放的作用,评价AMD持续污染对稻田土壤不同磷形态及磷有效性的影响.结果表明:在AMD添加比例小于50％时,随着AMD污染浓度的持续增加,稻田土壤中Fe-P呈显著升高的趋势(P=0.0001),在AMD添加比例为50％～75％时土壤中Fe-P趋于稳定,并在无机磷总量中占绝对优势;而Ca-P、O-P、Al-P在AMD 0.1％～1％极低污染水平下含量显著升高,而在AMD大于1％后又均呈显著降低的趋势(PCa-P=0.0003、PO-P=0.0001、Pl-P=0.0001);土壤有效磷和Ca-P、O-P、A1-P有基本一致的变化趋势,说明较高AMD污染程度可造成稻田土壤有效磷的显著淋失.土壤有机磷含量在0％～10％ AMD浓度范围内先小幅上升,在AMD浓度10％～75％范围内趋于平稳,当AMD浓度大于75％时,土壤有机磷含量与AMD浓度呈显著负相关(P=0.030).稻田土壤中总磷的含量随着AMD污染程度的增加呈先小幅上升后持续降低的趋势,但总体变化不明显.对应AMD相应比例下的pH值和Fe3+浓度,单独的pH值降低对土壤中磷(Ca-P)溶出效果不明显,而结合铁的添加可显著增加土壤中磷(Ca-P)的溶解.综上,酸性矿山废水污染可显著改变稻田土壤中磷的存在形态及有效性,其中AMD中高含量的Fe3+污染造成的影响最大.

Impacts of acid mine drainage on form and availability of phosphorus in paddy soil

The paddy soil in typical karst region of Southwest China were selected to simulate variation of different mineral forms of phosphorus including iron phosphate (Fe-P), calcium phosphate (Ca-P), occluded phosphorus (O-P), aluminum phosphate phosphorus (Al-P), total phosphorus and available phosphorus by sewage irrigation experiment of acid mine drainage pollution (AMD). It was also designed to investigate the impact of pH and iron ions in AMD on releasing of phosphorus from the paddy soil and to estimate the effects of AMD continuous pollution on forms of phosphorus and available phosphorus in paddy soil. The results showed that Fe-P in paddy soil significantly increased (P= 0.0001) at low addition of AMD when the ratio of AMD was lower than 50% and then kept stable at 50%-75%. As well, Fe -P was the main form of total inorganic phosphorus in paddy soil. The contents of Ca -P, O -P, Al -P increased significantly at extremely low ratio of 0.1%-1% and then decreased at high ratio above 1% (PCa-P=0.0003, PO-P=0.0001, PAl- P=0.0001). Available phosphorus had the same trend with Ca-P, O-P, Al-P, which indicated that high AMD content could cause significant leaching of phosphorus. The organic phosphorus content in soil had slight rise at level of 0%-10%, and then kept stable at 10%-75%, and finally showed a negative relationship (P=0.030) with AMD concentration when the ratio exceeded 75%. The content of total phosphorus increased slightly at the beginning and then continually declined with the increase of pollution, but the overall change was not obvious. The reduce of pH had no obvious impact on dissolution of phosphorus (Ca-P), but the impact could be significant by addition of iron. It concludes that the acid mine drainage pollution can significantly impact the forms and effectiveness of phosphorus in paddy soil, especially in the high iron content of AMD pollution.