Spatial Distribution of Pollutants and Risk Assessment of Heavy Metals in Farmland Groundwater around a Traditional Industrial Park—A Case Study of Shifang City, Southwestern China

Abstract

In this paper, the groundwater environment in the farmland area around a traditional industrial park in Shifang City, southwest China, was taken as the research object. Geostatistical methods with GIS technology were adopted to analyze the spatial distribution of conventional pollutants and heavy metals in groundwater and to evaluate potential ecological risks. Chemical oxygen demand (CODMn) and ammonia nitrogen (NH3-N) distributions showed poor continuity and apparent spatial differentiation, which were primarily attributed to intensive anthropogenic activities (e.g., industrial discharges). The total relative hardness of (TH), SO42−, and Cl− were uniformly affected by external factors, with little spatial differentiation. Concentrations of total phosphorus (TP), TH, SO42−, and Cl− followed an approximately normal distribution; the peak values of detected concentrations appeared in the frequency distribution range, while CODMn and NH3-N did not. Groundwater showed enrichment for various heavy metals, mainly Zn and Cu, with apparent spatial differentiation in Cr and Cu, consistent with external interference. The correlation coefficients of Cr–Cu and Cu–Pb were 0.693 and 0.629 (p < 0.01), respectively, indicating similar pollution sources. The single-factor pollution index for groundwater was Ni > Pb > Mn > Zn > Cu > Cr. Cu had a moderate potential ecological risk. The six heavy metals’ average integrated potential ecological risk index (RI) revealed that mild pollution accounted for 96.2% of the investigation area. Overall, the traditional industrial park poses a mild ecological risk to the shallow groundwater in the surrounding farmland.