渭河陕西段水体中重金属的时空动态变化特征研究

Spatial and temporal variation features of heavy metal pollutants in the Weihe River in Shaanxi

基于2008—2012年渭河流域陕西段水体26个断面的重金属监测数据,以Hg、Cd、Cr6+、Pb和As为研究对象,采用单因子水质标准比较法、重金属污染指数法(HPI)和秩相关系数法等对该段水体中重金属污染的时空动态变化特征进行研究。结果表明,渭河流域陕西段水体重金属综合污染程度年际变化呈显著下降趋势,年内变化特征各异,没有明显的规律性,Cr6+污染程度呈不显著上升趋势,Hg、Cd、Pb和As污染程度呈下降趋势,其中Hg下降趋势显著。渭河流域陕西段水体重金属综合污染程度空间分布呈现明显的区域性差异,其中西安段变化幅度最大,是影响渭河陕西段水体重金属质量浓度分布的主要河段。

Based on the data of heavy metal samples collected at 26 monitoring sections from 2008 to 2012, the article has made an anal ysis of the spatial and temporal variation features of such heavy metals as Hg, Cd, Cr6 , Pb and As in Weihe River, Shaanxi, with the methods of single factor pollution index, heavy metal pollution index （HPl）, and Spearman＇ s rank correlation coefficient. The results of our analysis demonstrate that, the extent of annual total pollution in-dex of the said five heavy metals in the above mentioned region tendsto decline significantly in the given period, though the monthly con- centration variation of such pollutants each year tends to be rather sporadic or stochastic. For example, the water polluted by Cr6＋ proves to be in a slight-rising tendency, whereas the extent of pollu tion by Hg, Cd, Pb and As turns to be gradually declining. Particu larly speaking, Hg pollution reveals a noticeable decline during the period under study. On the other hand, the variation of the compre hensive pollution index of the five heavy metals also reveals its region al traits in their spatial distribution, with the scope of such variation in Xi＇an section being the strongest, which features the efficiency of the key control measures affecting the water quality in terms of heavy metal pollution. Moreover, the comprehensive heavy metal pollution levels in the section from Xianyang to Xi＇ an turns to be relatively higher. The degree of heavy metal pollution in the tributaries proves to be higher than that in the River mainstream, for a few of them con tribute to the major part of such pollution. The pollution in-situ with the said tributaries account for the reinforced control of the industrial heavy metal emission in recent years. However, with the expansion of the urban areas and the growth of urban population, in addition to the limited capability of the sewage treatment and the insufficient landfill disposal power, the source of heavy metal pollution from the traffic and transportation of the metropolitan Xi＇ an into the surrounding wa ter environments, the pollution situation of heavy metals from the river sediments still remains the major concern for the heavy metal pollution in the River in the future.