摘要
1987-1988年及1997-2000年间,在西藏拉萨、定日、当雄、安多采集降雨样品及部分大气浮尘样品,分析测定了pH、电导率、CO2分压、总悬浮颗粒含量及10多种离子浓度.共测量了300场次降雨的pH值、电导率和其中60场次降雨的化学成分含量.结果显示:青藏高原降雨常呈弱碱性,1987-1988年间加权平均pH值为8.36,1997-1999年间为7.5.造成高原降雨呈弱碱性的主要原因是来自地面富含钙的粉尘.西藏是世界上空气污染最轻的地方,但是从20世纪80~90年代的降雨中,NO3-与SO42-含量增加,pH值降低,表明保护这片脆弱环境的紧迫性.
Some rainfall and dustfall samples were collected during 1987-1988 field expedition periods and in 1997, 1998, 1999 and 2000 at Lhasa, Dingri, Dangxiong and Amdo, Tibet. The parameters of rainfall, such as the pH values, conductivity, CO2 partial pressure, content of total suspended particles, and concentrations of K^+ , Na^+ , Ca^2+ , Mg^2+, Fe, Mn, NH4^+, Cl^-, NO2^-, NO3^-, SO4^2-, Br^-, HCO3^- and HPO4^2-, were measured. Some atmospheric dust samples were also collected. The pH values and conductivity of more than 300 rainfall events were measured, in which the chemical composition of 60 rainfall events were analyzed. The results show that rainwater in Lhasa was constantly alkaline with weighted average pH value of 8.36 during the period of 1987-1988 and 7.5 during the period of 1997-1999. Only one rainfall event was weakly acidic during 1997-1999. Although CO2 partial pressure, a major producer of acidity in natural water on the Plateau, falls with increasing elevation, the lowest measured CO2 partial pressure can only raise pH value by 0.1 in the sampling areas. The analysis on chemical composition reveals that the major contributor to alkaline rainfall is continental dust, which is rich in calcium. The analysis also shows that Tibet is still one of the cleanest areas in the world with little air pollution. However, the decrease of pH value of rainwater from the 1980s to 1990s, which was reflected by an increase of NO3^- and SO4^2- in rainwater, awakes us the urgency of environmental protection in this fragile paradise.
出处
《干旱区研究》
CSCD
北大核心
2005年第4期471-475,共5页
Arid Zone Research
基金
香港特区政府大学研究资助局(RGC)(HKU7123/02P)资助
关键词
碱雨
降雨pH值
气溶胶
雨水化学
西藏
alkaline rainfall
pH value
aerosol
CO2
chemical composition of rainwater.