摘要
洞庭湖平原西部地区浅层承压含水层是当地主要的地下水开采层,却面临严重的水质型缺水问题,其中以铵氮异常最为典型,但目前对于其来源和富集机制的认识十分薄弱。以洞庭湖平原西部为研究区,沿区域地下水流方向对地下水样品进行水文地球化学分析,旨在查明地下水中铵氮的来源,揭示地下水流动对铵氮富集的控制机理。结果表明:NH4-N质量浓度为0.05~16.75 mg/L,且与DOC、HCO3^-、As、Fe^2+、Mn、P质量浓度呈现较好正相关性;而高质量浓度的NH4-N对应着很低质量浓度的Cl^-、SO4^2-、NO3^-和很低的Cl/Br比值,可以推测浅层承压水中的铵氮主要由天然有机质矿化作用产生,而非人为输入。沿着地下水流向,NH4-N和As、Fe2+、Mn质量浓度均显著升高,说明由于水流越来越滞缓,含水介质颗粒越来越细,沉积物有机质越来越富集,含氮有机质矿化作用逐渐增强,使得NH4-N质量浓度逐渐升高,并形成了还原性逐渐增强的地下水环境,相关地球化学过程产生的还原性组分(砷、铁、锰等)也逐渐富集。本研究进一步丰富了地下水原生铵氮的成因理论,可为当地的供水安全保障提供理论基础。
Shallow confined aquifer is the main groundwater exploitation layer in the West of Dongting Plain,but it is faced with serious water shortage owing to worse water quality,among which ammonium anomaly is the most typical.However,its source and enrichment mechanism has been poorly understood at present.Taking the west of Dongting Plain as the study area,the hydrogeochemical analysis of groundwater samples along the direction of regional groundwater flow was carried out to find out the source of ammonium in groundwater and reveal the controlling mechanism of groundwater flow to the enrichment of ammonium.The results showed that the concentration of NH4-N was 0.05~16.75 mg/L,and had good positive correlations with DOC,HCO-3,As,Fe2+,Mn and P,while the high concentration of NH4-N corresponded to very low concentrations of Cl-,SO24-,NO-3,and very low Cl/Br ratio,it can be speculated that ammonium in shallow confined aquifer was produced by the mineralization of natural organic matter rather than anthropogenic input.Along the groundwater flow direction,the concentrations of NH4-N,As,Fe2+and Mn increased significantly,indicating that with the more sluggsih groundwater flowed,the particles of water-bearing media were becoming finer and finer,and the organic matter in sediments was more and more enriched,thus the mineralization of nitrogen-bearing organic matter was gradually enhanced and the concentration of NH4-N increased gradually,forming a gradually reduced groundwater environment.As a result,the reductive components(arsenic,iron,manganese,etc)produced from related geochemical processes were also gradually enriched.The study further enriches the genetic theory of geogenic ammonium in groundwater and provides theoretical basis for the safety and security of local water supply.
作者
黄艳雯
杜尧
徐宇
陶艳秋
邓娅敏
马腾
Huang Yanwen;Du Yao;Xu Yu;Tao Yanqiu;Deng Yamin;Ma Teng(School of Environmental Studies,China University of Geosciences(Wuhan),Wuhan 430078,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Wuhan),Wuhan 430078,China;China Three Gorges Corporation,Beijing 100038,China)
出处
《地质科技通报》
CAS
CSCD
北大核心
2020年第6期165-174,共10页
Bulletin of Geological Science and Technology
基金
中国地质调查局项目(DD20190263,DD2019040022)。
关键词
洞庭湖平原
浅层承压水
铵氮
有机质矿化
还原环境
Dongting Plain
shallow confined groundwater
ammonium
organic matter mineralization
reducing environment
