Geochemistry of trace elements and water quality assessment of natural water within the Tarim River Basin in the extreme arid region, NW China

Concentrations of twenty-one trace elements were measured by ICP-MS in 57 river and 20 well water samples collected in 2011 to define the spatial variability, sources, and the quality of natural water within the Tarim River Basin (TRB), one of the driest arid zones on the earth. The results showed that waters within the TRB were slightly alkaline with high total dissolved solids (TDS). TDS values in 76% of the samples, especially the well waters, were brackish water. The measured trace elements could be divided into dominant trace elements (>10 mu g/L; Sr, B, Al, Li, Fe, Ba, and Mn), moderate trace elements (10-0.1 mu g/L; Ti Pb, As, Ni, Cu, Zn, V, and Cr), and low trace elements (<0.1 mu g/L; Sn, Cd, Tl, Co, Sb, and Ga). The trace element concentrations in both the southern sub-basin and the Tarim River were high whereas those in the northern sub-basin were low. The trace elements have slightly higher concentrations in well waters than those in river waters. Principal component analysis (PCA) showed that B, Li, Sr, Co, Cd, and Tl derive from evaporite dissolution and carbonate weathering, while Ni, Cu, Zn, Sn, and Ga originate from mining industries. According to the water quality index (WQI), about 79% of the waters within the TRB can be classified of "good" and "excellent" quality, and are suitable for drinking. However, the high boron concentrations in the southeastern and the Yarkant sub-basins, high fluorine in the southeastern sub-basin and well waters, and high total hardness (TH) in the southern and the Yarkant sub-basins, and the Tarim River could constitute a threat to human health.