Application of Matter-Element and extension method in the comprehensive evaluation of groundwater environment quality of Zhecheng County, Henan Province

Considering the diversity of evaluation indexes in the water quality evaluation was incompatible with the results of single index, the authors used the Matter-Element and Extension method to comprehensively evaluate the shallow groundwater quality in Zhecheng County of Henan Province, and then compared its outcome with those of both the comprehensive scoring method and single index, which can analyze further the reliability of Matter-Element and Extension method and the variation trend of water quality. The Matter-element extension evaluations of the samples in 2008 and 2019 show that the comprehensive quality grade of shallow groundwater in Zhecheng County was better than those of comprehensive score method and single index, and that the grade of most samples is better than Class Ⅲ. The main influencing factors of groundwater quality in Class Ⅳ and Ⅴ are F and total hardness. Compared with the shallow groundwater quality of Zhecheng County in 2008 and 2019, the trend of grade was from Class Ⅰ to Class Ⅱ, from Class Ⅳ—Ⅴ to Class Ⅲ—Ⅳ, which was consistent with the prediction results by Matter-Element using samples in 2008. The Matter-Element and Extension method combines the comprehensive correlation degree and extension index, and can not only objectively reflects the overall situation of groundwater quality but also qualitatively analyzes the change trend of sample water quality, so its evaluation results are closer to the actual situation. This evaluation method has applicative value and research significance in the field of water quality evaluation.