Impact of human activities on the physico-chemical quality of surface water and groundwater in the north of Marrakech (Morocco)

Hydrogeochemical evolution of groundwater impacted by acid mine drainage (AMD) from polymetallic mining areas (South China)

Mining activities have long-term impacts on the groundwater of surrounding areas and deserve in-depth analysis and study. Herein, the geochemical mechanisms of acid mine drainage (AMD)-affected groundwaters were examined, and groundwater quality was assessed through water quality indices. 15 water samples from 7 domestic and 4 groundwater monitoring wells were tested for physical and chemical parameters in 2022, and multivariate statistical analysis was carried out with monitoring data from 21 domestic wells in 2010. The groundwater chemical composition varied from a predominantly Ca-HCO3 type in 2010 to a Ca-SO4 type in 2022. The isotopic values of δ18O and δD indicate that groundwater has not been significantly affected by evaporation. Changes in groundwater sulfate and total dissolved solids (TDS) levels over the twelve-year period confirmed the AMD infiltration impact on groundwater quality. The groundwater chemical properties changed more slowly than those of surface waters affected by AMD based on a cumulative increase in sulfate concentration of 29.94 mg/L. Changes in groundwater quality were investigated, namely, the spatiotemporal distribution of potentially toxic elements (PTEs), including Fe, Mn, Cd, Pb, and As. Mn concentrations in upstream groundwater areas near the mine decreased by 61.8% between 2010 and 2022. Conversely, groundwater in midstream areas had Mn concentrations of 2.25 mg/L and arsenic concentrations of 11.8 μg/L, both exceeding the WHO, 2022 standard. According to multivariate statistical analysis, Mn, Cd, and Pb originated from polymetallic minerals, whereas As was likely derived from the reduction of Fe/Mn hydroxyl oxides. AMD remediation improved contaminated upstream groundwater quality over 12 years, with a 36.8% improvement in WQI values. PTE distribution determined water quality changes; therefore, PTE contamination should be treated in mid- and downstream regions while contaminated groundwater should be treated upstream.

Spatial and Temporal Variations of the Water Quality of the Tiflet River, Province of Khemisset, Morocco

Humanity’s water needs are constantly increasing, however, under the action of humanity themselves, the reserves of this substance are, constantly, deteriorating in quantity and quality. It is, therefore, necessary to preserve the water reserves. However, any development of a hydrosystem’s quality conservation strategy is based on determining the chemical characteristics of its waters. Therefore, the objective of this study is to investigate the spatial and temporal variations of water quality in the Tiflet River, a watercourse in the northwest of Morocco, to estimate its degree of pollution and to determine its main sources of pollution. Thus, eight stations, distributed along the watercourse and positioned taking into account the potential sources of pollution, were fixed, and eleven physicochemical parameters were, seasonally, evaluated. Multivariate statistical techniques were used to assess variations in water quality and identify the main factors responsible for pollution. The results showed that wastewater discharges into the river can increase the water salinity, phosphorus load and organic pollution load of the river. The total loads of nitrogen and nitrate pollution were higher compared to the standard norms in the stations exposed to agricultural pollution and to the leaching of the watersheds, which could aggravate the eutrophication state of the river and stimulate the growth of aquatic vegetation. The organic pollution load recorded in the wet season is low, compared to that recorded in the dry season. Whereas, the nutrient load recorded during the dry season is low, compared to that recorded in the wet season. An overall pollution index was used, classifying surface waters from sub-clean to moderately polluted.

Facing the Challenge of Poly- and Perfluoroalkyl Substances in Water: Is Electrochemical Oxidation the Answer?

Electrochemical treatment systems have the unique ability to completely mineralize poly- and perfluoroalkyl substances (PFASs) through potential-driven electron transfer reactions. In this review, we discuss the state-of-the-art on electrooxidation of PFASs in water, aiming at elucidating the impact of different operational and design parameters, as well as reported mechanisms of PFAS degradation at the anode surface. We have identified several shortcomings of the existing studies that are largely limited to small-scale laboratory batch systems and unrealistic synthetic solutions, which makes extrapolation of the obtained data to real-world applications difficult. PFASs are surfactant molecules, which display significant concentration-dependence on adsorption, electrosorption, and dissociation. Electrooxidation experiments conducted with high initial PFAS concentration and/or in high conductivity supporting electrolytes likely overestimate process performance. In addition, the formation of organohalogen byproducts, chlorate and perchlorate, was seldom considered. Nevertheless, the first step toward advancing from laboratory-scale to industrial-scale applications is recognizing both the strengths and limitations of electrochemical water treatment systems. More comprehensive and rigorous evaluation of novel electrode materials, application of scalable proof-of-concept studies, and acknowledgment of all treatment outputs (not just the positive ones) are imperative. The presence of PFASs in drinking water and in the environment is an urgent global public health issue. Developments made in material science and application of novel three-dimensional, porous electrode materials and nanostructured coatings are forging a path toward more sustainable water treatment technologies and potential chemical-free treatment of PFAS-contaminated water.

Morphological and physiological assessments reveal that freshwater turtle (Mauremys leprosa) can flourish under extremely degraded-polluted conditions

Freshwater turtles are long-lived sedentary organisms used as biological sentinels to assess anthropogenic perturbations in freshwater-ecosystems; notably because pollutants tend to accumulate in their tissues. Pollution has detrimental effects in sea turtles, but studies in freshwater turtles have provided contrasted results: several species have been impacted by habitat perturbation and pollution while others not. It is important to explore this issue since freshwater turtles are threatened worldwide. We compared two populations of the stripe necked terrapin (Mauremys leprosa) in a relatively pristine area (piedmont of the Atlas mountain) versus an extremely degraded-polluted area (sewers of a large city) in Morocco. All morphological and physiological proxies showed that turtles were able to cope remarkably well with highly degraded-polluted habitat. Population density, body size, and body condition were higher in the sewers, likely due to permanent water and food availability associated with human wastes. Stress markers (e.g. glucocorticoids) provided complex results likely reflecting the capacity of turtles to respond to various stressors. Reproductive parameters (testosterone level, indices of vitellogenesis) were lower in the relatively pristine area. The deceptive overall image provided by these analyses may hide the disastrous human impact on rivers. Indeed, Mauremys leprosa is the only aquatic vertebrate able to survive in the sewers, and thus, might nonetheless be a pertinent indicator of water quality, providing that the complexity of eco-physiological responses is considered.

Nutrients' distribution and their impact on Pangani River Basin's ecosystem - Tanzania

Surface and groundwater from Pangani River Basin (PRB) were sampled in dry and wet seasons, analysed for dissolved organic and inorganic nutrients (N, P, Si and Urea). There was spatial and seasonal nutrients' variability, with enrichment of dissolved inorganic fractions accumulated from natural and anthropogenic sources. Silicates increased in dry season, whereas nitrate, ammonium, phosphate and urea increased in wet season; except for phosphate, other nutrients increased from upstream to the river mouth. High rate of chemical weathering possibly due to tropical climate and volcanic rocks has caused PRB to have higher concentration of silicates than average freshwater African Rivers. Contribution of PRB to the coast of Indian Ocean was 2.6, 39.0, 45.2, 67.4 and 5444.8 (mol/km²/yr) for nitrite, phosphate, ammonium, nitrate and silicates, respectively, which were lower than most of the tropical rivers in the world. Levels of nitrate and phosphate for most of the stations were higher than recommended levels for aquatic ecosystem health. Furthermore, observed hypoxia condition in some stations threatens aquatic life. This study recommends the efficient use of fertilizers to reduce nutrients' uptake into the lakes and rivers so as to meet the recommended level for aquatic and human health.

Avaliação da qualidade da água de consumo por comunidades ribeirinhas em áreas de exposição a poluentes urbanos e industriais nos municípios de Abaetetuba e Barcarena no estado do Pará, Brasil

Resumo Apesar dos grandes avanços tecnológicos introduzidos nos processos de tratamento das águas de consumo humano, as utilizadas para abastecimento tornaram-se um grande problema de saúde pública. O objetivo deste estudo foi avaliar a qualidade das águas consumidas em duas comunidades ribeirinhas no Estado do Pará expostas a poluentes domésticos e industriais. Foram realizadas quatro campanhas de amostragem nas duas comunidades e as variáveis utilizadas para o cálculo do Índice de Qualidade da Água (IQA) foram pH, Sólidos Totais, Cloreto, Fluoreto, Dureza e N-Nitrato. As águas utilizadas para consumo humano na Comunidade Maranhão, onde não há contaminação por poluentes industriais, apresentaram amostras adequadas, com melhora no período seco; já as águas de Vila do Conde, local próximo à atividade industrial, estiveram em ambos os períodos sazonais com qualidade inaceitável para consumo humano. Os principais parâmetros afetados foram o pH e o N-Nitrato, com valores até 25 vezes a referência da legislação brasileira para água de consumo humano. Esses resultados indicaram maior interferência antrópica no entorno da Vila do Conde em Barcarena, necessitando-se de avaliações clínicas por profissionais especializados sobre o estado de saúde desta população.