嘉陵江流域水质综合评价与时空变化分析

Comprehensive Evaluation and Spatiotemporal Analysis of Water Quality in the Jialing River Basin

嘉陵江是长江上游重要的水源涵养地,由于其水域广,存在农业污染和跨界污染等问题,水质状况不够稳定。为深入分析嘉陵江干流及涪江、渠江两个主要支流的水质变化特征,基于2021年总流域48个水质断面5项水质指标的监测数据,包括溶解氧、高锰酸盐指数、氨氮、总磷、总氮,采用模糊综合评价法、内梅罗指数法、最近邻法分析了流域的水质变化特征。结果表明:①内梅罗指数法评价结果偏劣,最近邻法偏优,模糊评价法能更好地反映各指标对每级水质标准的贡献程度。②流域有38个断面总氮劣于Ⅲ类,有1个断面高锰酸盐指数为Ⅳ类,总氮污染较为严重,高锰酸盐存在超标问题,农业活动是这两个指标超标的重要原因。其余3个指标符合嘉陵江水域功能控制标准;③空间上,干流劣Ⅲ类断面最少,水质相对最优,而涪江最差;且Ⅴ类断面都分布在中下游,流域上游水质优于中下游;④在年内,流域枯水期的劣Ⅲ类断面相比汛期增加3个,枯水期水质相对更差;其中涪江全年水质变化较小,而渠江在7-12月Ⅴ类断面数降低,年内水质有变好的趋势;干流在7-12月Ⅴ类断面数增多,年内水质有变差的趋势。研究成果可为嘉陵江流域的污染治理和水生态修复提供支撑。

The Jialing River,a key watershed in the upper Yangtze River,faces challenges in maintaining stable water quality due to its extensive area and issues such as agricultural and cross-border pollution.This study examines the water quality variations in the Jialing River's main course and its two major tributaries,Fujiang and Qujiang,using 2021 monitoring data for five water quality indicators:dissolved oxygen,permanganate index,ammonia nitrogen,total phosphorus,and total nitrogen,across 48 river sections.Methods including Fuzzy Comprehensive Evaluation,Nemerow Index,and Nearest Neighbor Analysis were applied.The findings reveal that:①The Fuzzy Evaluation method effectively demonstrates the impact of each indicator on various water quality standards.②In the study area,38 sections are rated below Grade Ⅲ for total nitrogen,and one section is rated Grade IV for permanganate index,indicating significant pollution of total nitrogen and exceedances of permanganate standards.Agricultural activities are identified as a major contributor to the exceedances of these two indicators.The remaining three indicators meet the water quality control standards for the Jialing River.③Spatially,the sections with Class Ⅲ water quality are the least in the main stream,indicating relatively optimal water quality,while the Fujiang exhibits the poorest water quality.ClassⅤsections are mainly distributed in the middle and lower reaches,with better water quality in the upper reaches of the watershed.④Seasonally,the water quality of river sections categorized as Class Ⅲ deteriorated during the dry season,with an increase of three sections compared to the wet season.The water quality during the dry season exhibited greater instability.Specifically,the Fujiang demonstrated relatively stable water quality throughout the year,whereas Qujiang exhibits a decreasing trend in the number of ClassⅤsections from July to December,indicating an improvement in water quality during the year.Conversely,the main stream shows an increase in the number of ClassⅤsections from July to December,suggesting a declining trend in water quality during this period.These results offer valuable insights for pollution control and aquatic ecosystem restoration in the Jialing River basin.