酸性矿山废水污灌对农田土壤氮磷钾组分的影响

Effect of acid mine drainage irrigation on nitrogen,phosphorus and potassium components of farmland soil

【目的】为研究酸性矿山废水(Acid mine drainage,AMD)污染对农田土壤氮磷钾组分的影响。【方法】采集安徽省铜陵市某硫铁矿尾矿库区酸性矿山废水和附近未受酸性矿山废水(AMD)污染的农田土壤,构建不同浓度AMD污灌土壤实验,分析在污灌周期内土壤理化性质和土壤氮磷钾组分含量的变化。【结果】酸性矿山废水污灌显著降低了土壤pH,提高了土壤的电导率,AMD浓度越高,土壤pH以及电导率的变化幅度越大。污灌实验周期内,土壤铁铝磷(NaOH-P)含量显著增加且与AMD浓度呈显著正相关(r=0.38,P<0.05),而残渣态磷(Res-P)含量显著减少,有效磷(NaHCO_(3)-P)和钙磷(HCl-P)含量则无明显变化,污灌实验周期内对照组土壤有效磷(NaHCO_(3)-P)、钙磷(HCl-P)和铁铝磷(NaOH-P)含量呈先升高后降低的趋势,主要源于土壤含水率在实验前期1~5周处于较高的水平,而在第7、9周含水率突降至较低;污灌土壤有效磷(NaHCO_(3)-P)和钙磷(HCl-P)含量的变化趋势与对照组相同,而铁铝磷(NaOH-P)含量随时间呈增加趋势。表明,AMD污灌促进了土壤残渣态磷的溶解并以NaOH-P形式赋存在土壤中。AMD污灌土壤氨态氮(NH_(4)^(+)-N)和硝态氮(NO_(3)^(-)-N)含量显著增加,土壤总氮含量无明显变化,而有机质显著降低,指示AMD促进了土壤有机氮的矿化。土壤硝态氮(NO_(3)^(-)-N)在25%AMD污灌条件下增加量最大,指示高浓度AMD抑制了土壤的硝化作用。污灌周期内土壤速效钾含量无显著变化。【结论】酸性矿山废水排放对铜陵尾矿区周边农田土壤氮磷组分有显著影响,在后期AMD污染修复过程中应予以重视。

【Objective】The study aimed to understand the effects of acid mine drainage(AMD)pollution on the fractions of nitrogen,phosphorus and potassium in farmland soils.【Method】Acid mine drainage and nearby uncontaminated farmland soils were collected from a pyrite mine tailing area in Tongling city,Anhui province,to construct an experiment of irrigation with different concentrations of AMD,and study the changes of soil physical and chemical properties and the fractions of nitrogen,phosphorus and potassium in contaminated soils during the irrigation period.【Result】The pH decreased while the electrical conductivity increased significantly in those irrigated soils due to the acid mine drainage inputs.During the irrigation period of nine weeks,the content of iron/aluminum-bound phosphorus(NaOH-P)in soils increased significantly and correlated well with the concentrations of AMD(r=0.38,P<0.05),the fraction of residual phosphorus(Res-P)decreased significantly,and the fractions of available phosphorus(NaHCO_(3)-P)and calcium-bound phosphorus(HCl-P)changed insignificantly.During the nine weeks of AMD irrigation,the available phosphorus(NaHCO_(3)-P),calcium-bound phosphorus(HCl-P)and iron/aluminum-bound phosphorus(NaOH-P)in control groups increased first and decreased then.It was mainly because the soil water content was at a high level in the first 1-5 weeks of the experiment,while it suddenly dropped to a very low level in the seventh and ninth weeks;The available phosphorus(NaHCO_(3)-P)and calcium-bound phosphorus(HCl-P)in contaminated soils showed similar trend with those in control groups over time,while the iron/aluminum-bound phosphorus(NaOH-P)showed different trend with that in control group.These results indicate that AMD irrigations promoted the dissolution of Res-P in soils to phosphate that ultimately transformed into NaOH-P.The increased ammonia nitrogen(NH_(4)^(+)-N)and nitrate nitrogen(NO_(3)^(-)-N),decreased organic matter and stable total nitrogen in those irrigated soils suggested a mineralization of soil organic nitrogen due to the AMD inputs.Nitrate nitrogen(NO_(3)^(-)-N)in polluted soils show highest increase with the 25%AMD irrigation,indicating that high AMD likely restricted the soil nitrification.The available potassium in contaminated soils was stable during the irrigations.【Conclusion】This study shows that the discharge of acid mine drainage from mine tailing has a significant effect on the fractions of nitrogen and phosphorus of nearby farmland soils,it should be noted during the remediation of AMD polluted farmland soils.