Monitoring of As, Cd, Cr, and Pb in Groundwater of Mexico's Agriculture Mocorito River Aquifer: Implications for Risks to Human Health

Groundwater from the Mocorito River aquifer in Mexico has been historically employed for both human consumption and irrigation of its overlaying agriculture fields. The aim of this research was to investigate the levels and distribution of potentially toxic elements (PTEs) in the aquifer to determine their sources and to assess their potential health risks. Groundwater samples were collected from wells at eighteen sites in two climatic seasons. In the dry season, mean dissolved concentrations (mu g L-1) of As, Pb, Cd, and Cr were 3.19, 0.05, 0.02, and 0.15, respectively, and their total (unfiltered) concentrations were 4.10, 0.47, 0.05, and 0.52, respectively. While in the rainy season, their dissolved concentrations were 4.60, 0.03, 0.01, and 0.06, respectively, and their total concentrations were 5.58, 0.25, 0.01, and 0.12, respectively. On average, concentrations of the four PTEs were below national and international guidelines for drinking water. Concentrations of As exceeded the WHO (2007) guidelines (10 mu g L-1) at three sites and had yielded relatively high values of both chronic daily intake and hazard quotient. Lifetime cancer risk for As indicated the probability for developing this disease of 1 in 10, 000 inhabitants. Pearson's correlation and principal component analysis (PCA-Varimax) were carried out. According to these, all the PTE concentrations were mainly derived from natural lithogenic sources. Arsenic concentrations constitute potential human health concerns for both direct consumption and its bioaccumulation in local crops. Finally, due to high As concentrations in some sites in the aquifer, the implementation of a sustainable groundwater management plan in the MORCA, that include a monitoring of PTE levels, is recommended.