Evaluation of heavy metal contamination and pollution indices through geostatistical methods in groundwater in Bafra Plain, Turkey

Groundwaters are continuously polluted by various factors, including industry, excessive fertilizer, and pesticide use. In this study, ten heavy metals (Pb, Zn, Cr, Mn, Fe, Cu, Cd, Ni, Al, and As) were analyzed in groundwater samples collected from Bafra Plain, and groundwater quality was assessed through heavy metal pollution index (HPI), heavy metal evaluation index (HEI) and degree of contamination (Cdeg) indices. Geostatistical analyses and ordinary kriging methods were used to determine the spatial distribution of heavy metals and pollution indices. The present findings revealed that Al, As, Fe, and Mn concentrations in some sections of the study area were above the limits set for drinking waters. In terms of pollution indices, 21.97% of the study were found to be highly polluted with HPI, 16.27% with HEI, and 36.08% with Cdeg. Geostatistical analyses revealed that Al, Mn, HPI, HEI, and C-deg exhibited moderate spatial dependence, and As and Fe exhibited strong spatial dependence. In some parts of the research area, groundwater iron levels were above the limits set for drip irrigation. Less heavy metal pollution levels were encountered in western parts of the research area. It was thought that pesticide and fertilizer used over the agricultural lands and geological structures were effective in groundwater pollution. It was concluded based on the present findings that groundwater quality should continuously be monitored, and fertilizer and pesticide use should be minimized to reduce groundwater pollution levels. Geostatistical methods should also be used in the management and development of groundwater resources.