The groundwater environment changes under the influence of anthropogenic activities. Because of the construction of the Da'an irrigation area, the amount of irrigation and fertilizer there has changed. Achieving the coordinated development of groundwater resources and economic benefits requires a deeper understanding of the impact of the construction of irrigation areas on groundwater chemistry. In this study, the variations in groundwater chemistry characteristics were studied using statistics and hydrogeochemical methods. Further, the groundwater quality was assessed using the support vector machine method. The results show that the primary water chemistry type was the HCO3 - Ca - Mg type, with local Fe3+ and F- pollution. After the construction of irrigation area, the SO42-, HCO3-, K+ + Na+, and Ca2+ contents decreased, but the Cl- and Mg2+ contents increased. The main nitrogen source in phreatic water was anthropogenic activities, and the main pollution component was NH4+. After the construction of the irrigation area, the NH4+ concentration increased significantly, and the ratio of samples exceeding the standard increased by 37.5%. The over-standard regions spread to the northwest, east, and southeast of Da'an City and east and southeast of the irrigation area. The groundwater quality was predominantly grade IV and V, which accounted for an increase of 16.35%, widely distributed in the south, east, and southwest of the irrigation area and urban areas. The construction of the irrigation area reduced the suitability of phreatic water for agricultural irrigation in the southeast but increased in the west and north.
Keywords: Anthropogenic activities; HJ-biplot; Irrigation area; Nitrogen; SVM; Water chemistry characteristics; Water quality.
© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.