Multivariate and index-based assessment of classical and emerging contaminants in Ramsar wetlands of northern Mexico

Wetlands are among the most essential and diverse ecosystems, providing a wide range of intrinsic ecological functions that sustain biodiversity and contribute to the well-being of surrounding communities. However, they are increasingly threatened by water quality degradation resulting from both natural processes and anthropogenic pressures. This study presents an assessment of water quality in two Ramsar-designated wetlands in northern Mexico: the Cañón de Fernández State Park and the Laguna de Santiaguillo. In situ measurements and laboratory analyses were conducted to evaluate physicochemical, microbiological, and emerging contaminants, with a focus on pharmaceuticals. Multivariate statistical methods, specifically cluster and correlation analyses, were applied to identify spatial patterns, contaminant sources, and potential environmental stressors. Additionally, a Weighted Arithmetic Water Quality Index (WAWQI) was calculated to provide an integrated evaluation of water quality. Results revealed distinct contaminant profiles across sites, reflecting both geogenic inputs (e.g., Al, As, Fe) and anthropogenic influences, including wastewater discharge, agricultural runoff, and seasonal tourism. The presence of pharmaceuticals, such as diclofenac, along with high coliform counts and chemical oxygen demand, indicates the occurrence of emerging pollutants in protected areas. The WQI classified water quality as "poor" in Cañón de Fernández and "unsuitable" in Laguna de Santiaguillo, mainly associated with elevated arsenic levels and low dissolved oxygen. These findings highlight the need for integrated watershed management, improved wastewater infrastructure, and monitoring strategies that include emerging contaminants, while emphasizing the value of wetlands and the critical need for conservation efforts that acknowledge both their ecological functions and the benefits they provide to humanity.