淮河流域(河南段)水质时空变化特征及其与土地利用类型的关系

水质的定量评估有利于地方政府制定和实施水污染防治政策.为研究近期淮河流域行政区划尺度上水质的时空变化特征及其受土地利用类型的影响，以淮河流域（河南段）为研究区，根据2009-2017年31个水质站点的水质周测浓度，结合土地利用遥感监测数据，利用季节性Mann-Kendall趋势检验法及Spearman相关分析法，对ρ（COD_Cr）、ρ（NH₄+-N）和ρ（TP）的时空变化特征及其与土地利用类型的相关性进行分析.结果表明:①在时间上，ρ（COD_Cr）、ρ（NH₄+-N）和ρ（TP）在大部分地区呈下降趋势，但各水质指标依然较高，ρ（COD_Cr）和ρ（TP）在丰水期略高于枯水期，ρ（NH₄+-N）在枯水期高于丰水期.②在空间上，水污染比较严重的有沱河、浍河、惠济河、涡河、贾鲁河、清潩河、颍河中游、黑茨河、汾泉河和洪汝河，大部分站点为GB 3838-2002《地表水环境质量标准》Ⅳ类或Ⅴ类水质，部分站点甚至属于GB 3838-2002劣Ⅴ类水质；而颍河上游、北汝河、沙河、淮河干流及史灌河的水质较好，基本属于GB 3838-2002Ⅰ类或Ⅱ类水质.③土地利用类型与水质之间的相关性表现为ρ（COD_Cr）、ρ（NH₄+-N）、ρ（TP）与旱地和城镇面积占比均呈正相关，与林地、草地和荒地面积占比均呈负相关，与水域面积占比也呈负相关但不显著.研究显示，淮河流域（河南段）水质有所改善，但部分地区水污染问题仍然比较严重，旱地与城镇用地是造成研究区水污染的主要原因，林地、草地、荒地和水域能够缓解水污染. 

Spatiotemporal Changes of Water Quality in Huai River Basin (Henan Section) and Its Correlation with Land Use Patterns

The quantitative assessment of water quality is beneficial to local governments in formulating and implementing water pollution prevention policies. The Huai River Basin (Henan section) is selected as the research area, aiming to study the spatiotemporal changes of water quality, and the impact of various land use patterns on water quality on the scale of administrative division of the Huai River Basin. According to the weekly data at 31 water quality monitoring sites from 2009 to 2017, the spatiotemporal changes of ρ(COD_Cr), ρ(NH₄+-N) and ρ(TP) concentrations and their correlation with land use patterns are analyzed with the assistance of remote sensing monitoring data of land use, the seasonal Mann-Kendall trend test and Spearman correlation analysis. The results show that:(1) During the study period, ρ(COD_Cr), ρ(NH₄+-N) and ρ(TP) show a significant downward trend in most regions. However, these water quality indexes still remain at a relatively high level. Specifically, ρ(COD_Cr) and ρ(TP) are slightly higher in wet season than in dry season, whilst ρ(NH₄+-N) is higher in dry season. (2) In terms of spatial characteristics, the rivers that have been severely polluted include:the Tuo River, the Hui River, the Huiji River, the Guo River, the Jialu River, the Qingyi River, the midstream section of the Ying River, the Heici River, the Fenquan River and the Hongru River. The water quality measured at most of these monitoring sites fell into Class Ⅵ or Ⅴ based on GB 3838-2002 Environmental Quality Standards of Surface Water, and the water quality at some sites even exceeded the GB 3838-2002 standards for Class Ⅴ category. In contrast, the water quality of the upstream of the Ying River, Beiru River, Sha River, the main stream of Huai River and Shiguan River are better and can meet the GB 3838-2002 standards for Class Ⅰ and Ⅱ. (3) The correlation between land use patterns and water quality demonstrates that ρ(COD_Cr), ρ(NH₄+-N) and ρ(TP) are positively correlated with the percentage of drylands and urban areas, but negatively correlated with the percentage of forest lands, grasslands, and unused lands. Additionally, the three indexes are negatively correlated with the proportion of water areas but the correlations were statistically insignificant. This research shows that the overall water quality of the Huai River Basin (Henan section) has been improved, but the water pollution problems in some parts of the area are still severe. The primary reasons resulting in water pollution, as the study indicates, are the drylands and urban lands, while forest lands, grasslands, unused lands and water bodies can alleviate water pollution.