西昌市尔乌泉域泉水水文地球化学特征及成因

摘要

Springs and/or spring groups are primary groundwater resources for local people in towns and villages in the southwest Sichuan Province.A study of hydrogeochemical characteristics and genesis of spring water is of scientific value and realistic significance to the local people.Chemical components,oxygen and hydrogen and tritium isotopes of the springs and surface water in the catchment area of the Erwu spring of Xichang are combined to identify the hydrogeochemical characteristics and genesis of the spring water.The chemical components analyses show that the spring waters with low TDS are neutral to weak alkalinity groundwater,and are of HCO3-Ca · Mg and HCO3 · SO4-Ca · Mg types.The chemical components of the surface waters are similar to those of the spring waters.The hydrogen and oxygen isotopes illustrate that the spring waters and surface waters are of meteoric origin,and there is no isotope shift of oxygen.Moreover,tritium isotopes demonstrate that the spring waters originated from meteoric waters,and experienced a long runoff time.local fault and fold structure are helpful in leading to interaction between the meteoric water and carbonate,gypsum of clastic rocks,and the cation exchange with clay minerals of Quaternary sediments subsequently occurs,which results in the major chemical constituents of Ca2+,Mg2+,HCO3-and SO42-in the spring waters.In addition,some water samples with high concentrations of Na + and SO42-can be interpreted by the influence of sewage and chemical fertilizers.%泉和泉群是川西南乡村居民首要的生活水源,对本区泉水水文地球化学特征及成因的研究具有重要的科学价值和指导意义.以尔乌泉域泉水和地表水为研究对象,通过分析泉水和地表水常规水化学组分、氢氧同位素和氚同位素,探讨了该泉域泉水水文地球化学特征及成因.结果显示:尔乌泉域泉水为中偏碱性低矿化水,其水化学类型为HCO3-Ca· Mg和HCO3·SO4-Ca· Mg型水.地表水因受泉水补给影响具有与泉水相似的组分特征.氢氧同位素分析显示尔乌泉水和地表水补给来源为大气降水,且未发生氧同位素漂移.氚同位素进一步确定泉水为非现代水,地下水经历较长的径流时间.受断裂带和褶皱构造的影响,入渗补给的大气降水与碎屑岩中碳酸盐岩、石膏等矿物发生水岩相互作用,后与第四系黏土物质发生阳离子交换反应,致使泉水水化学组分以Ca2+、Mg2+、HCO3-和SO42-为主.此外,居民生活污水的排放和化学肥料的施用也对泉水中Na+和SO42-组分产生影响.