[Effect of developing tourism on chemical characteristic of precipitation: taking Lijiang for example].

1090 precipitation samples were collected from 1989 to 2006 at Lijiang City. The analyzed results indicate that the average pH value is 6.08 at study period, which is higher than the average pH value (5.0) during 1987 to 1989, and the annual pH value show an increasing trend, suggesting there are more alkaline mass input to air after 1989. the concentrations of major ions Cl-, SO4(2-), NO3-, Na+, Ca2+, Mg2+ and NH4+ are 11.56, 32.64, 3.63, 2.54, 50.19, 7.73 and 11.36 microeq x L(-1), respectively. By computed the correlation coefficients and sources contribution among major ions, it find that Ca2+ and Mg2+ are from soil-derived sources, and about 57.2% of SO4(2-) also come from soil-derived sources; 95.4% of total NO3- and 41.9% of SO4(2-) come from anthropogenic sources, and only Na+ and 25.7% of Cl- come from sea source, meaning that the chemical composition of precipitation at Lijiang region is main influenced by regional sources. According to the variation of tour scale at Lijiang city, it can be divided into 3 periods of 1987-1989, 1989-1996 and 1997-2006. The percent of soil-derived ions at different periods is 40%, 53% and 72%, respectively, showing a significant increase trend; but the percent of anthropology-derived ions at different periods is 39%, 36% and 15%, respectively, showing a decrease trend. It explains that more dust input to the air by expending city scale, changing the land form and overusing water resources. But in order to develop tourism, the pollutants related to industries are controlled well.