西藏帕隆藏布江流域天然水的水化学特征

Aquatic chemistry characteristics of natural water in the Parlung Zangbo River Basin,Tibet

帕隆藏布江是雅鲁藏布江左岸水量最大的支流.为了调查帕隆藏布江流域水体水质和水化学特征,分析了水体的常规指标,包括p H、电导率、含盐量(SAL)、总溶解固体(TDS)和溶解氧(DO)值.同时测定了水样和底泥样品中23种金属元素,Ca是水体中的主要阳离子,水体中离子的平均含量趋势符合Ca>Mg>Fe>K>Na>Mn>Zn>Ba>V>Pb>Cr>Ni>As>Cu>Co>Se>Hg>(Mo、Ag、Sb、Tl、Cd和Be).采用《地表水环境质量标准》(GB3838—2002)及地质累积指数(Igeo)分别评价了水质和底泥状况.结果表明,水体中Cu、Se、As、Zn、Cd和Pb均达到Ⅱ类及以上标准,仅Hg是潜在污染物质,Hg含量虽略高(最高达0.3μg·L^(-1)),但低于《国家生活饮用水卫生标准》(<1μg·L^(-1))限量;底泥中重金属污染程度较轻,Zn、Pb、Ni、Cu和Cd几乎不存在污染,As是底泥中的主要污染物,其次为Cr.综合各项指标表明帕隆藏布江流域水体水质良好.

The objective of this study was to investigate the water quality and characteristics of water chemistry in the Parlung Zangbo River basin,which is the largest tributary of the Yarlung Zangbo River basin. The conventional indices of the water samples were analyzed, including p H,conductivity,salinity（ SAL）,total dissolved solids（ TDS） and dissolved oxygen（ DO）. Contents of more than 23 metal elements in the water and sediments samples were measured. The results showed that the major cation in the water was Ca. The average concentrations of cations in the water samples followed the order of Ca〉Mg〉Fe〉 K 〉Na 〉Mn 〉Zn 〉Ba 〉V 〉Pb〉 Cr〉 Ni〉 As 〉Cu 〉Co〉 Se〉 Hg （ Mo,Ag,Sb,Tl,Cd and Be）. Besides,the water quality and the status of the sediments were evaluated by the Environmental Quality Standards for Surface Water（ GB3838—2002） and the geoaccumulation index,respectively. As shown in the result,the concentrations of Cu,Se,As,Cd and Pb in the water reached the levels of quality Ⅱ suggested by GB 3838—2002. Hg was the sole potential pollutant in the water. Although,the concentration of Hg（ 〈0. 3 μg·L^-1） was relatively high,it still reached the Standards for Drinking Water Quality. On the other hand,the major pollutant in the sediments was As,followed by Cr. Other cations including Zn,Pb,Ni,Cu and Cdcontributed little to the heavy metal pollution in the sediments. In conclusion,the water in the Parlung Zangbo River basin was of good quality.