Groundwater Quality in the Yucatan Peninsula: Insights from Stable Isotope and Metals Analysis

• Published in: Ground water 2021-11, Vol.59 (6), p.878-891
• Main Authors: Arcega‐Cabrera, F., Sickman, J. O., Fargher, L., Herrera‐Silveira, J., Lucero, D., Oceguera‐Vargas, I., Lamas‐Cosío, E., Robledo‐Ardila, P. A.
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Aquifers; Cadmium; Conductance; Contaminants; Contamination; Denitrification; Dilution; Dry season; Groundwater; Groundwater pollution; Groundwater quality; Groundwater treatment; Heavy metals; Isotopes; Metals; Nitrates; pH effects; Pollution transport; Rainy season; Seasonal variations; Seasonality; Seasons; Sinkholes; Stable isotopes; Statistical methods; Surface water; Surface-groundwater relations; Transport; Wastewater; Wastewater pollution; Wastewater treatment; Water analysis; Water pollution; Water quality; Water sampling; Water treatment; Watersheds; Wet season
• ISSN: 0017-467X; 1745-6584
• DOI: 10.1111/gwat.13109

High surface water‐groundwater connectivity characterizes watersheds underlain by karsts, increasing contaminant transport risks. However, karsts are highly complex, making research necessary to understand the transport of contaminants from the surface, through the aquifer, to discharge areas. In Yucatan, the lack of waste water treatment raises the risk of groundwater contamination. We monitored stable isotopes (δ18O‐NO3 and δ15N‐NO3), cadmium, and lead to document waste water contamination and transport during the rainy and dry seasons, using water samples collected along the Ring of Cenotes during each season. Specific conductance and pH showed no consistent seasonality, with conductance ranging from 0.5 to 55 mS/cm and pH ranging from 6.6 to 8.6 for most samples. Nitrate concentrations in the cenotes averaged 205 ± 260 μM and no seasonal pattern was observed. Cd and Pb concentrations were 0.1 to 37.9 μg/L and 0.2 to 243.2 μg/L, respectively. Nitrate stable isotope values were 2.6 to 27.2‰ for δ18O and 1.2 to 20.7‰ for δ15N. The statistical relationship between δ15N and δ18O, in dry season samples, indicated that denitrification was occurring. A scale measure for waste water recognition showed: (1) high variability among sites probably related with dry/rainy seasons and/or diverse anthropogenic activities; and (2) specific water quality variables that contribute to contamination at each site during each season. Importantly, our analyses indicate that in the area surrounding the Ring of Cenotes, waste water exhibits spatial and temporal patterns related to complex transport and dilution processes, as is the case in karsts in general.