High - Speed Impact Of Urbanization On The Hydrochemical Characteristics In Beijing And Beijing's Water Study On Safety Assessment

Urbanization is both a social phenomenon and a regular transfer of nature, and it is one of the strongest human powers, numerous changes related to global environmental change are happened in city area. City water environment is not only the material base of human daily life but also the carrier of human waste. With the development of urbanization, lacking of water resources and water pollution are becoming more and more serious. Thus systematic study on environmental effects of urbanization towards water has positive function on sustainable development of city and solving the conflict between economic increasing and water environment quality decreasing.Based on historical record and water samples collected in Chao-Baihe River, Jiyunhe River and Beiyunhe River, the time and spatial variation of water is discussed and the sources of and nature and anthropogenic sources of major ions, the change of weathering rate and CO2 consumption, meantime, evaluation of water safety is conducted. The conclusions are show as follows:1.water chemistry is controlled by rock weathering in Chaohe River and Baihe River before rapid urbanization. However, Wenyuhe appears obvious human interference since 1980. Despite Mg2+ and HCO3-, the concentrations of other ions rose slightly, and have a concentration trend of water quality. Precipitation functions as a dilution. Reservoirs in river systems have influence on ion concentration. Since urbanization, factors such as regional climate change, population increasing, wastes outlets, land use transformation and industry development have effects on concentration of major ions. Water plant and industry have influence on Cl-, SO42-, while the concentration of K+ and the area of city shows positive relationship.2.The diversion of geology background results in the different contribution of rocks. In Jiyunhe River, the total contribution of rock weathering is 71.26%, in which carbonate contribute 48.34% and silicates contributes 22.93%. In Chao-Baihe River, the total contribution of rock weathering is 74.64%, in which silicates accounts for 77.95% and carbonates accounts for 26.34%. In terms of Beiyunhe River, the total contribution of rock weathering, the contribution of silicates and the contribution of carbonates are 77.95%, 61.27% and 16.67% respectively.3.River is stable in general. p(CO2)riv/p(CO2)atm analysis shows that the value increase along with the development of urbanization. Polluted water, biomass in water and the decomposition of organic compound are reasons of p(CO2)riv increasing. The weathering rate in Chao-Baihe River and Beiyunhe River have been decreased since 1960, the variation range during 1980-2006 is 13.99-75.99kg/km2?yr,the annual reduction amount is 1.39kg/km2, the annual CO2 consumption is 9.0t, and the variation range from 2.8-13.7t.4.Logarithm function calculation shows that the safety index in Beijing in 2006 is 0.94, and is higher than that in 2001.