丽江市大气环境特征分析

丽江市1990~2003年SO₂、NO_x和TSP的平均浓度为0.018、0.013和0.112 mg/m³,SO₂和NO_x浓度在1998之前为上升阶段,1998年之后为下降阶段。1989~2006年期间降水中年均pH值为6.08,高于酸雨标准值,EC均值为14.2 US/cm;pH值自1994年以来一直处于缓慢上升状态,EC也呈现出缓慢上升趋势。1989~2006年降水中SO₄^2-、NO₃^-、Cl^-、NH₄⁺、Ca²⁺、Mg²⁺、Na⁺、K⁺、平均浓度值依次为1.57、0.41、0.20、1.14、0.09、0.06、0.13 mg/L。研究证实大气环境状况、气候特征和产业结构转型对丽江降水中离子浓度有重要影响。

Rainwater Chemistry and Its Environmental Significance in a Typical Monsooonal Temperate Glacial Region,China

The mean concentrations of SO₂, NO_x and TSP are 0.018 mg/m³, 0.013 mg/m³ and 0.112 mg/m3 during 1990-2003 in Lijiang City. The average pH value is 6.08 during 1989-2006, which is lower than the standard of acid rain. The average EC value is 6.08 during 1989-2006, and the increase of EC value accelerated in 1998. The average concentrations of SO₄^2-, NO₃^-, Cl^-, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺ and K⁺ are 1.57 mg/L, 0.16 mg/L, 0.41 mg/L, 0.20 mg/L, 1.14 mg/L, 0.09 mg/L, 0.06 mg/L and 0.13 mg/L in Lijiang City. The mean concentrations of SO₂, NO_x and TSP in Lijiang City are lower than those in many cities of China because of the successful transformation of the industrial structure from conventional industries to tourism, characteristically bringing higher economic benefit and less environmental pollution. The variations of SO₂ and NO_x between 1990 and 2003 reflected this change. Concentrations of anions and cations are out of balance: the mean total anion concentration exceeds the mean total cation concentration. TSP concentrations have been low because Lijiang City is far from the source region of wind-borne sand. A slow increasing trend of pH values between 1990 and 2002 reflected the decline or relocation of primary manufacturing industries, a source of air pollution, as the tourist trade developed rapidly. A decrease of pH values from 2003 probably was a consequence of the sharp increase of coal-burning heating plants and motor vehicles needed to meet the requirements of tourism. Increases of EC and total cation concentrations have accelerated since 1998 as precipitation has decreased. The data from Lijiang City demonstrate the necessity of developing tertiary industry and promoting a better industrial structure in order to improve the quality of the urban atmosphere and to control air pollution in China's cities.