Changes of hydrochemical composition and heavy metals concentration in shallow groundwater from karst hilly areas in Guiyang region,China

The quality changes of shallow groundwater from karst hilly areas in Guiyang region of China impacted by the urbanization were investigated.The results show that the major ions in shallow groundwater from the karst hilly areas are mainly composed of HCO3-,SO42-,Ca2+ and Mg2+,and the concentrations scopes of NO3-,Cl-,K+ and Na+ of the groundwater in agricultural,residential and industrial areas are 4.5-9.6,2.8-7.1,3.9-6.3 and 2.5-4.9 times higher than those in the forest areas,respectively.The concentrations of As,Pb and Cd of shallow groundwater in the industrial areas are also significantly enhanced,followed by those in the residential areas and the agricultural areas.The concentrations of NO3-,SO42-,As,Pb and Cd of the groundwater in the industrial areas and those of NO3-,SO42-,As and Cd of shallow groundwater in the residential areas reach grade Ⅲ of the Groundwater Quality Standard of China(GB/T 14848-93),while the concentration of NO3-in the groundwater from the industrial areas exceeds grade Ⅴ.With the process of urbanization,NO3-is the key factor to influence the groundwater quality in karst hilly areas,followed by SO42-,As,Pb and Cd.