Chemical influence factors and contribution rate in shallow groundwater of Wuxi City

Accurate assessment of the chemical factors influencing groundwater is crucial to classify groundwater pollution, select appropriate treatment schemes and set treatment objectives. This study analyzes 67 groups of shallow groundwater samples from Wuxi city in Jiangsu Province by using mathematical statistics, factor analysis, and an absolute factor score-multiple linear regression model. The findings are as follows: Firstly, regarding the quality grade of shallow groundwater in Wuxi, Class III water constitutes 53.7% of the samples, while ultra-Class III water accounts for 46.3%. The ions exceeding standards are COD, NH₄⁺, NO₃⁻ and SO₄^2- in sequence. Secondly, the groundwater can be categorized into 9 types, with HCO₃-Ca ·Na, HCO₃-Ca and HCO₃· SO₄-Ca ·Na types predominating, representing 76.1% of the total samples. Thirdly, three major chemical influence factors in the groundwater chemical index system—natural evolution (F1), industrial production (F2) and agricultural production (F3)—account for 76.05% of the cumulative variance contribution rate, with their comprehensive contributions being 57.44 %, 27.62 % and 14.94 %, respectively. The results indicate that the measured concentrations of groundwater chemical index closely match the predicted concentrations derived from the absolute factor score and multiple linear regression model, demonstrating the method’s effectiveness in analyzing the chemical factors influencing groundwater.