Spatial and seasonal variations of trace metals in a karst water system in Central China and implications
Based on monitoring (2011.7-2012.6) of a karst water system in NE Sichuan, Central China, we presented monitoring results of the spatial and seasonal variations of metals Ca, Mg, Sr and Ba in cave waters and surface river water. Three sites were chosen for the monitoring. SLPB and LZLY are two in-cave sites and HS represents the Nuoshui River. SLPB is the deepest point of the cave, where an underground river emerges. There is fast dripping water in winter and the drip water becomes a waterfall in summer. LZLY is the pool. The drip water at SLPB, pool water at LZLY and surface river water at HS were collected once a month from July 2011 to June 2012. At each site, about 500 ml of waters were sampled with pre-cleaned polypropylene bottles (Nalgene), acidified in site to pH<2 with double distilled HNO3. These samples were kept in a refrigerator at a low temperature (~ 4°C) until analysis. On average, the surface river water represented by HS experienced much less water-rock interaction compared with the cave waters at SLPB and LZLY, providing us the opportunity to investigate the influence of water-rock interaction on the hydro-geochemistry of groundwater enroute to Loufang Cave. Ca, Mg, Sr, and Ba in these water samples were measured at the geochemistry laboratory of Southwest University in China. Mg and Ca were analyzed with an ICP-OES with detection limits of 1×10-9 and analytical precisions (RSD) better than 1%. Sr and Ba were analyzed with an ICP-MS with RSD better than 5%. A synthetic multi-element standard (High-Purity Standards) was used for external calibration.