Assessment of As, Pb, Cr and Cd in surface water systems accounting for dry and wet season and ecotoxic effect in Elodea canadensis in the historic mining district of Taxco, Mexico

The article examines the seasonal dynamics of As, Pb, Cr, and Cd in the surface waters of the Taxco mining district in Guerrero, located in southwestern Mexico. It quantifies the concentrations of these metals via Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and assesses spatial source influences through ArcGIS-based geostatistical mapping. Ecotoxicological responses were assessed in the submerged macrophyte Elodea canadensis , focusing on genotoxic effects and the decline of chlorophyll a , chlorophyll b , and total chlorophyll over a 30-day exposure period at mixed-metal hotspot sites. Seasonal contrasts showed that As, Pb, Cr, and Cd concentrations were higher during the wet season, consistent with enhanced hydrologic mobilization and runoff from mine wastes. Conversely, As levels concentrations peaked in the dry season, likely due to reduced dilution and greater aqueous aqueous persistence relative to particulate partitioning. Despite generally low genotoxic signals, the highest Pb exposure produced approximately 60–65 % DNA damage, indicating a dominant contribution of Pb to mixture toxicity. The overall toxicity ranking followed the order Pb > Cr > Cd > As at both 15-day and 30-day exposures. The parallel decreases in total and individual chlorophyll fractions reflect photosynthetic impairment under mixed-metal stress. However, the moderate pigment loss and time-dependent recovery suggest compensatory physiological mechanisms, such as antioxidant activation and pigment remodeling, that partially offset cumulative damage—particularly under Cr-rich conditions. The spatial clustering of metals near mine-waste discharges zones, combined with seasonally modulated exposure, underscores thejoint influence of source proximity and hydrologic regime on ecological risk. The agreement between geochemical gradients and the physiological responses of E. canadensis supports its use as a reliable bioindicator for mixture toxicity screening in mining-impacted tropical dry-forest watersheds. Overall, the results emphasize: (i) the need to prioritize Pb-dominated mixtures in management actions; (ii) the importance of seasonally targeted monitoring and flow-awere mitigation strategies (e.g., enhance controls during storm season), and (iii) the potential of phytorestoration strategies employing metal-tolerant macrophytes to reduce contaminant loading at the source.Future work focusing on redox/speciation (As(III)/As(V), Cr(VI)/Cr(III)) and bioaccumulation dynamics will refine risk assessments and inform the design pathway-based remediation approaches. • Water quality is influenced by metal pulses driven by waste and varies seasonally. • Bioassays showed progressive but moderate genotoxic stress over 15 and 30 days. • Ecotoxicological effects are dominated by Pb and Cd, while those from As and Cr were minor. • Chlorophyll a/b levels declined at day 15 but partially recovered by day 30. • E. canadensis can survive under chronic, low-to-moderate exposure to mixed-metals hotspots.