重庆南山老龙洞地下河系统重金属分布、迁移及自净能力

2013年12月(冬季)和2014年6月(夏季)分别采集重庆南山老龙洞地下河上覆水,孔隙水和表层沉积物样品.分析重金属Mn、Pb、Cu、As在上覆水-孔隙水-表层沉积物中的分布及迁移特征,研究地下河对重金属的自净能力,以期为岩溶区城镇的发展和地下水的合理开发与保护提供科学依据.地下河上覆水和孔隙水中Mn、Pb、Cu、As检出率为100%,其质量浓度大小为MnPbCuAs,夏季冬季,孔隙水上覆水;地下河上覆水因Mn、Pb含量超标已不可作为饮用水源,夏季重金属在孔隙水和上覆水之间的浓度差大于冬季,更容易扩散到上覆水中影响上覆水水质;地下河表层沉积物存在重金属富集现象,4种重金属总量自采样点UGR6到采样点UGR5呈减少趋势,由采样点UGR5至采样点UGR0段逐渐增加;表层沉积物中Mn具有极强的不稳定性和迁移性,容易污染上覆水,扩大污染区域;地下河对Mn具有很强的自净能力,其中表层沉积物对Mn的自净能力要大于岩溶管道壁.

Distribution and Transportation Characteristics of Heavy Metals in Nanshan Laolongdong Subterranean River System and Its Capacity of Self-Purification in Chongqing

For figuring out the distribution and transportation characteristics of heavy metals Mn,Pb,Cu and As among overlying water-pore water-surface sediments so as to offer a scientific basis for the development of urban construction and protection of karst groundwater, overlying water, pore water and surface sediment samples were collected in December 2013(winter) and June 2014(summer) respectively. Results show that the detection rates of Mn, Pb,Cu and As are 100% both in overlying water and pore water with the concentration Mn >Pb >Cu >As, summer >winter,pore water >overlying water, respectively, and the groundwater could not be a source of drinking water because of the excessive content of Mn and Pb. In addition, the concentration of heavy metals Mn, Pb, Cu and As in pore water are higher than that in overlying water, indicating that heavy metals could diffuse into overlying water from pore water because of concentration gradient, especially in summertime.Moreover, study also finds that heavy metals are accumulated in surface sediments, the total content of four heavy metals has a decreasing trend between UGR6(sampling site 7) and UGR5(sampling site 6), but has an increasing trend from UGR5 (sampling site 6) to URG0(sampling site 1). Mn, in surface sediments, has strong instability and mobility, which can not only cause the pollution of overlying water but also enlarge contaminated area. In a word, Laolongdong subterranean river has strong capacity of self-purification, especially the surface sediments.