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Due to an increasing reduction of hydrological resources across Mexico and their growing contamination from global warming and anthropogenic activities, this study evaluated water from the perennial Lake Coatetelco (Ca-Mg-HCO 3 ) in tropical central-southern Mexico and groundwater (Ca-Mg-HCO 3 and Na-HCO 3 -Cl) from the surrounding wells for drinking as well as irrigation qualities. Comparison with the WHO guidelines and the estimated water quality indices (DWQI and IWQI) grouped almost all the samples collected after the warm season rainfall in excellent and good categories (DWQI < 100) for drinking, even though fluoride remained > 1.5 mg/L in 50% samples. Except for one groundwater sample, all showed > 25% permeability (classes I and II) in Donnen classification indicating their suitability for irrigation. USSL and Wilcox classifications, however, catalogued some in the high-salinity hazard group and some as doubtful for irrigating regular plants. Samples from about 53% wells were also in high and severe restriction categories of IWQI for the irrigation. Total Hazard Quotient Index (THQI) for estimating the non-carcinogenic risk (HQ fluoride  > 1) showed that at least one lake water sample and 53% of groundwater might expose the adult and child population to dental and skeletal fluorosis. This water quality assessment data posterior to the rainfall season could be useful as a baseline for both the short- and long-term monitoring in attention to the United Nation's Sustainable Development Goal 6., (© 2023. The Author(s).)

North-central Mexico has groundwater contaminated with arsenic (As) and fluoride (F). Based on the dispersion patterns of these solutes, their sources are linked to felsic volcanic rock fragments and secondary minerals (clays, iron oxyhydroxides) within the alluvium fill of the aquifers. However, little is known about the effect of the enrichment factors for F and As in this area. Natural enrichment factors include evaporation, Ca/Na, and competitive adsorption and desorption from solid phases. This study used 1237 groundwater quality data measurements from 305 sampling sites collected between 2012 and 2019 in the state of Durango in north-central Mexico. To determine the contribution of enrichment factors to As and F content, the study area was divided into four sections, two being in the mountainous part of the state and two in the high plateaus. The data were compared among sections and analyzed using Spearman correlation and Piper and Block diagrams. The results indicate that the main solute enrichment mechanisms are evaporation and weathering of silicates and evaporites. Among the four sections, As, pH, and HCO 3 seemed not to vary, F varied slightly, and nitrate and total dissolved solids varied the most. The lack of variation in As among sections is associated to its strong adsorption to clay minerals and iron oxyhydroxides, whereas the diminished F content in the eastern sections is likely linked to the adsorption of F to precipitating calcite (since groundwater is saturated with respect to calcite (SI calcite  = 0.43) and undersaturated for fluorite (SI fluorite  =  - 1.16). These processes shed light on the distribution of F and As in this area, and are likely operating in other states in northern Mexico and in semi-arid areas elsewhere., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Polycyclic aromatic hydrocarbons (PAHs) are petroleum components that, when dissolved in the aquatic environment, can disrupt normal animal physiological functions and negatively affect species populations. Gambusia yucatana is an endemic fish of the Yucatán Peninsula that seems to be particularly sensitive to the presence of PAHs dissolved in the water. Here, we examined PAH effects on gene expressions linked to endocrine disruption and biotransformation in this species. Specifically, we examined the expression of vitellogenin I (vtg1), vitellogenin II (vtg2), oestrogen receptor α (esr1), oestrogen receptor β (esr2), aryl hydrocarbon receptor (AhR) and the cytochrome P4503A (CYP3A) genes. We exposed G. yucatana to different concentrations of PAHs (3.89, 9.27, 19.51 μg/L) over a period of 72 h and found changes associated with reproduction, such as increases in hepatic expression of vtg, esr, AhR and CYP3A, mainly at concentrations of 9.27 and 19.51 μg/L. Our results also indicate that benzo[a]pyrene was probably the main PAH responsible for the observed effects. The genes examined here can be used as molecular markers of endocrine-disrupting compounds, as the PAHs, present in the environment, as gene expression increases could be observed as early as after 24 h. These biomarkers can help researchers and conservationists rapidly identify the impacts of oil spills and improve mitigation before the detrimental effects of environmental stressors become irreversible., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Mexican Lake Chapala is used as water supply for human consumption. Consequently, water quality of this lake is of paramount importance for the lake's wellbeing. The contribution presented in this paper investigates monitoring and assessment of lake water quality using water quality index (WQI), metal chemical speciation, and multivariate statistical techniques. Descriptive statistics shows total metal concentrations undetected conferring the lake a healthy status. Dissolved Cd and Pb exceed criterion continuous concentration limit, whereas Zn is below this limit indicating that water quality is satisfactory for aquatic life. However, WQI indicates poor water quality attributed to failure of conductivity, total solids, nitrogen, and phosphates, due to industrial and agro-industrial effluents. Metal speciations indicate that the presence of low concentrations of dissolved metals reflect interactions with gills of fish through metal-biotic ligand complexes affecting water quality. Positive correlations are obtained between conductivity and nitrates, indicating that agricultural activities and fertilizer runoffs increase the conductivity and that the environmental state of lake is being altered by human activities. Factors F1 (31%), F2 (19%), and F3 (11%) represent 61% of variability; F1 and F2 corroborate the pressure exerted by pollutants related with fertilizers and agrochemicals; F3 contains Zn and Pb with positive loads attributed to influx of tourist visitors. Sites S4, S5, S6, and S9 are identified as the most environmentally affected by COD, Alk*, pH, Cl - , nitrites, phosphates, and TS. Multivariate techniques permit to conclude that environmental stress of Lake Chapala is caused by variables pertaining to agrochemical, fertilizers and municipal wastes.

The geochemical behavior of zinc, lead and copper from sulfidic tailings in a mine site with potential to generate acidic drainage (pyrite (55%) and sphalerite (2%)) is reported in this paper. The mining area is divided in two zones, considering the topographic location of sampling points with respect to the tailings pile: (a) outer zone, out of the probable influence of acid mine drainage (AMD) pollution, and (b) inner zone, probably influenced by AMD pollution. Maximum total ions concentrations (mg/L) measured in superficial waters found were, in the outer zone: As (0.2), Cd (0.9), Fe (19), Mn (39), Pb (5.02), SO4(2-) (4650), Zn (107.67), and in the inner zone are As (0.1), Cd (0.2), Fe (88), Mn (13), Pb (6), SO4(2-) (4,880), Zn (46). The presence of these ions that exceeding the permissible maximum limits for human consume, could be associated to tailings mineralogy and acid leachates generated in tailings pile.