Analysis of the quality, source identification and apportionment of the groundwater in a typical arid and semi-arid region

Abstract

A detailed and thorough study of the quality and its distribution, source identification and apportionment of groundwater, as the major or even sole selection of clean water in Songyuan City (a typical arid and semi-arid district in China), is needed for local sustainable development. The groundwater quality was evaluated using a vague set (VS)-technique for order of preference by similarity to ideal scheme (TOPSIS) model to determine its contamination status. Additionally, to explore the source and quantitative analysis of the driving factors of the groundwater chemistry in Songyuan City, a hydrochemical graphical method and a Principle Component Analysis (PCA) and Positive Matrix Factorization (PMF) model were employed. Regarding the quality of the groundwater in Songyuan, 74.5% of the samples were categorized into Grade I–III (Excellent, Good, and Moderate) water, indicating that the majority of the groundwater can be used directly. Moreover, the confined water tended to be cleaner and more appropriate for use in comparison with the phreatic water in Songyuan City. The PCA and PMF model and hydrochemical graphs demonstrated water–rock interactions and the evaporation process acted as the main factor, which was followed by anthropogenic activities as they contributed 50.1% and 20.4% of the total, respectively. Besides, the fluoride and iron contamination mainly caused by geogenic processes cannot be ignored as they were identified as the two driving factors that controlled the water quality, accounting for 20.2% and 9.3%, respectively. The mutual influence of the natural geological processes and human interventions contribute to the groundwater deterioration in Low Plain. Furthermore, the inappropriate well-forming techniques (without water-stop processes) in Qianan County was the main reason for the low-quality of deep Neogene confined water. This research provides useful information and directions for the local government to carry out corresponding and effective groundwater remediation strategies.