New insights into trace elements in the water cycle of a karst-dominated glacierized region, southeast Tibetan Plateau

Hydrogeological Functioning of a Karst Underground River Basin in Southwest China

The Maocun underground karst river system in the peak cluster depression is an important source of groundwater in southwest China. Multitracers and high resolution water-level-monitoring technology were used to assess and evaluate the hydrogeological structure and flow dynamics. The results showed that the spatial geological structures of the sites had high heterogeneity. Scatter plots of environmental tracers divided the sampling points into groups under different water flow patterns. The karstification was found to increase from sites XLB and LLS to sites BY, SGY and BDP to sites CY and DYQ, where the main water flow patterns at these site groups were diffuse water, both diffuse water and conduit water, and conduit water, respectively. The response times of the subsystems were found to be influenced by the spatial structure, the degree of karstification, and the volume of precipitation and frequency. The average response times of SGY, BDP, ZK, and Outlet in the selected precipitation scenarios were 5.17, 4.08, 16.42, and 5.83 h, respectively. In addition, the EC, δ13 CDIC , 222 Rn, and δ18 O exhibited both linear or exponential relationships. Overall, three hydrogeological conceptual models were constructed showing: (1) high precipitation driving the deep water, resulting in a concentrated flow regime and regional groundwater flow field; (2) both concentrated and diffuse water flows existing under moderate precipitation, resulting in mixed water flow field; (3) the water cycle in the shallow karst aquifer system under low precipitation causing the local groundwater flow field to be dominated by diffuse water flow.

Distribution and risk appraisal of dissolved trace elements in Begnas Lake and Rupa Lake, Gandaki Province, Nepal

Contamination of the trace elements (TEs) in the freshwater ecosystems is becoming a worldwide problem. This study was carried out to investigate the TEs contamination, and their associated health risk in Begnas Lake and Rupa Lake, Gandaki Province, Nepal. A total of 30 water samples were collected from both lakes during the pre-monsoon season in 2016. The samples were analyzed for the TEs including copper (Cu), lead (Pb), zinc (Zn), nickel (Ni), cobalt (Co), chromium (Cr), cadmium (Cd), manganese (Mn), cesium (Cs), and arsenic (As) using inductively coupled plasma mass spectrometry. The results exhibited that the mean concentrations of all the TEs were higher in Rupa Lake as compared to Begnas Lake except Pb. Principal component analysis and cluster analysis revealed that both the geogenic and anthropic sources were the major contributors of TEs in the lake water. Anthropic activities were considered to contribute the TEs like Zn and Mn in lake water mainly via agricultural runoff, while evaluating the risk of TEs on human health all the elements showed HQ < 1 and CR < 10−4 indicating currently very low health risk concerns. In good agreement with above, the water quality index (WQI) of the Begnas Lake and Rupa Lake was 2.67 and 5.66, respectively, specifying the lake water was safe for drinking and public health concern. This appraisal would help the policymakers and concerned stakeholders for the sustainable management of Ramsar listed freshwater lakes in the Himalayas.