渭河干流陕西段综合治理前后的水质变化与趋势

目的]讨论渭河干流陕西段综合整治项目启动以来河道水质的变化趋势,检验整治工程的治理成效,为后续河道的污染防治提供一定技术支持。方法]基于2010—2016年渭河干流陕西段主要监测断面的水质数据进行水质综合评价,应用Mann-Kendall检验法阐述水质变化趋势,运用重标极差分析法(R/S分析法)查明水质的未来变化趋势。结果]2016年渭河干流陕西段河道水污染已由2010年的重度污染转为轻度污染,劣Ⅴ类水质断面比例减少了58.8%,Ⅳ—Ⅴ类断面比例增加了55.5%,Ⅰ—Ⅲ类断面占比保持平稳;宝鸡市、咸阳市、西安市和渭南市4个出境断面枯水期化学需氧量(COD)、NH3-N浓度普遍高于丰水期,治理后西安市出境断面污染削减最为显著,但是西安市出境断面仍然是4个断面中污染最为严重的断面;4个出境断面NH3-N浓度均呈现高度显著下降趋势且未来持续性较强;咸阳、西安、渭南市出境断面COD浓度呈显著下降趋势,但是未来持续性较弱,宝鸡市出境COD浓度呈不显著上升趋势且会延续。结论]综合治理后,河道污染程度明显减轻,水质变化明显,但部分断面污染物浓度有上升趋势,需引起特别关注。

Water Quality Change Before and After Comprehensive Treatment in Shaanxi Section of Weihe Main Stream

Objective] To explore the trend of water quality since the start of the comprehensive regulation project in Shaanxi section of the main stream of Weihe River, in order to check the effectiveness of regulation works and provide technical support for subsequent river pollution prevention and control.Methods] Based on the water quality data of the main monitoring points in Shaanxi section of the Weihe River main stream during 2010-2016, the temporal and spatial variation characteristics of water quality were analyzed, the trend of water quality was expounded by using Mann-Kendall test, and the future trend of water quality was identified by using R/S analytical method.Results] From 2010 to 2016, the water pollution had changed from severe pollution to mild pollution. The chemical oxygen demand(COD) and NH₃-N concentrations of 4 exit monitoring points in Baoji, Xianyang, Xi''an and Weinan cities during the dry season were generally higher than those in the flood season. After the treatment, the decrease of the pollution in Xi''an City exit section was the most significant, but still was the most polluted section. The concentration of NH₃-N in Baoji, Xianyang, Xi''an and Weinan cities showed a significant downward trend, and this trend would continue. The concentration of COD in Xianyang, Xi''an and Weinan City showed a significant downward trend, but the future sustainability was weak. The increasing trend of COD concentration in Baoji City was not significant.Conclusion] After the comprehensive treatment, the pollution level of the river is obviously reduced and the water quality is changed obviously. However, the concentration of pollutants in some sections shows an upward trend, which needs special attention.