典型岩溶区地下水系统重金属元素分布特征浅析——以广西坡月地下河为例

地下河为岩溶地下水系统的重要组成部分,为查清典型岩溶区地下水系统中重金属指标的含量变化及空间分布特征,文章以广西坡月地下河系统为例,通过不同断面两次采样分析,重点剖析地下河系统在水文地球化学作用下,地下水中以"五毒"元素及Zn、Al和Mn为代表的重金属元素含量。分析结果表明:坡月地下河水体pH值在7.34~8.10之间,水体中"五毒"元素、Zn、Al和Mn的检出含量极低或未检出,质量浓度均远小于国家地下水环境质量标准中的Ⅲ类水质标准,适合各种用途。检出含量较高的点主要为地下河明流段或补给区地表水,含量最高分布在坡心地下河出口水体,其原因是坡心地下河系统区内工矿企业和其它经济活动干扰相对较强,特别是工矿企业的矿石和尾矿渣的露天堆放(如金矿)是引起地下水中重金属元素的检出或超标的重要因素。

Characteristics of heavy metal element distribution in the groundwater system of typical karst regions: A case study in Poyue underground river, Guangxi, China

Underground river is an important part of karst groundwater system. The purpose of this work is to reveal the concentrations and spatial variation of heavy metals represented by zinc (as Zn), aluminum (as Al) and Manganese (as Mn), in particular by the five toxic heavy metals, under the typically hydrogeochemical environment in the Poyue underground river system, Guangxi. Water sample were collected at the localities along defined cross section lines in the field and the concentrations of heavy metals were analyzed in laboratory. The results show that pH value of the Poyue groundwater is between 7.34 and 8.10, with an average of 7.67. Toxic heavy metals detected in the underground river have very low concentrations, much less than the level of III water quality category recommended by the national environmental quality standards. Therefore, the karst groundwater is suitable for a variety of purposes. The results also show that higher concentrations of these elements occur at the localities where the underground river exposes on the surface or surface water in the recharge area, with the maximum values at the underground river outlet located at slope toe. The reason is that in the slope area, industrial, agricultural and mining activities are extremely strong, which is characterized by the dumps of industrial and mine (such as gold mine) tailing wastes on the slope. This causes the occurrence of the heavy metals in the karst river system.