Strontium isotope and chemical compositions of rainwaters from Guiyang, Guizhou Province, China

Land-use and industrial activities are considered the most important driving forces in the ongoing processes of alteration in atmospheric chemistry. Most of these anthropogenic influences on the atmospheric chemistry are due to emissions of nitrogen, ammonia and sulfur. Oxidation of these chemicals and subsequent scavenging by precipitation have caused widespread acidification of precipitation and extra inputs of nitrogen and sulfur to terrestrial and aquatic systems, with several deleterious consequences to the environment, such as decline of forests and crop productivity, increase of lake and soil acidification and loss of biodiversity [1]. With a fast economic development, energy consumption has increased significantly in the last two decades in Guizhou Province. This has led to widespread coal combustion as an important alternative of energy generation. Acid rain, therefore, has been an atmospheric environment problem especially of several big cities in Guizhou Province. In order to identify and quantify contaminant sources and their fluxes to the catchment, we have conducted a study on chemistry of the rainwaters over Guiyang, a capital city of Guizhou Province. Twenty-two bulk rainwater samples were collected from Jan. 11, 1999 to Oct. 24, 2001, and analyzed for their chemical and isotopic compositions. Ca, Mg, SO4 2and NO3 are the principal ions in the rainwater samples. The sum of Ca and Mg accounts for 78%-96% of the total cations, while SO4 2for 28%-98% of the total anions. As compared with rainwaters of several big cities in eastern China, the rainwaters samples show significantly high SO4 2and NO3 contents, and high enrichment of these ions over Cl. Enrichment of SO4 2and NO3 in the rainwater samples are mainly due to industrial inputs. Sr concentrations of rainwaters vary from 0.02 to 0.33μmol/L. Sr/Sr ratios range from 0.707934 to 0.709080. Combined with element ratios of major cations, the variation in Sr isotopic compositions shows that the cations, such as Ca, Mg and Na have two principal sources, rock/soil chemical weathering, and anthropogenic sources, with marine input very small. Acknowledgement: National Science Foundation of China (Grant no: 40372108) and Chinese Academy of Sciences (Grant no: KZCX2-205) support this research.