中文摘要：

共收集丽江市1989～2006年间1090个大气降水样品,分析结果表明研究期间平均pH值为6.08,高于丽江地区1987～1989年间的平均pH值5.0,并且年平均pH值呈上升趋势,说明在发展旅游业的背景下,本区有更多碱性物质输送到大气环境中.主要阴阳离子Cl^-、SO24^-、NO 3^-、Na^＋、Ca^2＋、Mg^2＋和NH ^4＋的浓度值分别为11.56、32.64、3.63、2.54、50.19、7.73、11.36μeq.L-1,均相应地高于1987～1989年间的离子浓度值.通过计算降水中离子间相关系数和各离子的非海源比例,得出Ca^2＋和Mg^2＋主要来自于地表粉尘,57.2%的SO42-来自于地表粉尘;95.4%的NO 3-和41.9%的SO42-来自于人类活动排放;Na＋和少部分Cl-（25.7%）来自于海源;表明丽江市大气降水中的化学成分主要受区域大气环境影响.根据丽江市近年来游客人数变化,可将其分为1987～1989年、1989～1996年和1997～2006年3个发展时期.其中来自地表粉尘源离子浓度在不同时期的比例分别为40%、53%和72%,增加明显,而人为排放源离子的浓度比例分别为39%、36%和15%,逐渐减小.这主要是由于丽江市产业结构以旅游业为主,随着旅游规模扩大,原有的自然环境改变以及水资源减少,导致地表粉尘量增加.同时,对与人类活动有关的化石燃料污染物排放控制较好.

英文摘要：

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-,SO42-,NO 3-,Na ＋,Ca2 ＋,Mg2 ＋ and NH 4＋ are 11.56,32.64,3.63,2.54,50.19,7.73 and 11.36 μeq.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 SO42-also come from soil-derived sources;95.4% of total NO 3-and 41.9% of SO42-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.