Hydrochemical evolution processes of multiple-water quality interfaces (fresh/saline water, saline water/brine) on muddy coast under pumping conditions

Microplastic transport and ecological risk in coastal intruded aquifers based on a coupled seawater intrusion and microplastic risk assessment model

Seawater-groundwater interactions can enhance the migration process of microplastics to coastal aquifers, posing increased associated environmental risks. Here, we aim to analyze the relationship between seawater intrusion (SWI) and groundwater microplastic pollution in Laizhou Bay (LZB), which is a typical area of sea-land interactions. The results showed that modern seawater intrusion was the main process controlling the migration of microplastics. The detected microplastics in the study area showed a migration pattern from nearshore marine areas to groundwater aquifers along the SWI direction. In addition, the microplastics also reached the brine formed by palaeo-saltwater intrusion through hydraulic exchange between aquifers. By comparing the spatial distributions of different microplastic parameters, we found that nearshore fisheries, commercial, tourism, textile, and agricultural activities were the main sources of microplastics in groundwater in the study area. A risk assessment model of microplastics associated with SWI was further optimized in this study using a three-level classification system by assigning appropriate weights to different potential influencing factors. The results showed moderate comprehensive ecological risks associated with microplastics from seawater intrusion in the study area, with high microplastic enrichment risks. This study provides a scientific basis for future research on seawater-groundwater interactions and microplastic pollution in coastal regions.

Effects of global and climate change on the freshwater-seawater interface movement in a Mediterranean karst aquifer of Mallorca Island

Karst aquifers are globally prized freshwater sources, posing a significant preservation challenge. These aquifers typically exhibit dual or even triple porosities, encompassing matrix, fractures-fissures and conduits, rendering them highly responsive to variations in chemical characteristics and hydraulic head. In coastal regions, these aquifers often possess extensive subsurface conduit networks intricately linked to the rock matrix, facilitating groundwater discharge into the sea. Therefore, they display acute sensitivity to seawater intrusion, swiftly reacting to changes in precipitation and pumping regimes. This makes them exceptionally vulnerable to short-term meteorological fluctuations and long-term climate change. Their high heterogeneity leads to uneven penetration of the freshwater-seawater interface, causing rapid seawater intrusion inland over significant distances. The Mediterranean region, characterized by water deficit and water stress, faces strong impacts from climate change, featuring a warming atmospheric trend exceeding the global average, along with diminished rainfall exacerbating water scarcity. Increasing water demands for agriculture, urban development, and the growing tourism industry, because of global change, are worsening water stress. Our primary research objectives were analyzing the environmental consequences of global and climate change on seawater intrusion in Mediterranean coastal karst aquifers, with a focus on the role of the double-flow model, thus contributing to the understanding of the processes involved. To achieve this, we selected a study region on Mallorca Island in the western Mediterranean, where a karst aquifer system discharges into the sea. We employed various study methods, notably hydrochemical techniques and multi-isotopic analysis, encompassing the examination of 2H and 18O isotopes in water, 87Sr/86Sr ratio, Sr and B concentrations, and δ11B in water. A key finding is the rebound effect, wherein aquifers recontaminate due to solute molecular back-diffusion following cessation of extractions and the retreat of marine intrusion, providing insight into the impact of climate and global change on Mediterranean karst aquifers.

Groundwater for drinking and industrial purposes: A study of water stability and human health risk assessment from black sand mineral rich coastal region of Kerala, India

Tempero-spatial analysis of groundwater to disseminate the level of drinking water quality and industrial suitability to meet the developmental requirement of a region is a significant area of research. Accordingly, groundwater quality and geochemical interactions prevailed in a black sand mineral rich coastal village is systematically presented in appraisal of drinking and industrial uses for economic engineering purposes. The study area focused is Alappad village, Kollam, Kerala, India has numerous ecological features in a sustainable perspective. The region is unique with placer deposits where an alluvial soil aquifer-saline water-freshwater interaction occurs. This dynamics decides the pertinent hydro geochemistry, potable and designated uses of ground water in season wise. Coastal area is hereby presented based on water quality parameters predicted with the health risk assessment model with a view on human health and cancer risk due to ions (Pb, Ni, Cu, Ba, Fe, Al, Mn, Zn) in groundwater.. To ascertain industrial usage, ground water is evaluated by Langelier saturation index (LSI), Ryznar stability index (RSI), Aggressive index (AI), Larson-Skold index (LS) and Puckorius scaling index (PSI) and inferences are complemented. Chemical weathering and evaporation processes are the natural factors controlling hydrochemistry of this aquifer. This complex coastal system has Nemerow pollution index (NPI) of moderate pollution for total dissolved ions of Fe and lesser for Cu, and Cr present in groundwater. LSI indicates, water is scale forming but non corrosive (46% in PRM, 20% in MON and 47% in POM). Water quality index (WQI) in POM (ranged 28.7-79.9) was excellent for drinking, followed by PRM (23.6-218.2) and MON (33.4-202.7) seasons. This groundwater bears temporary hardness with the dominance of Ca-Mg-HCO3 water type. Health risk assessment of non-carcinogenic risk index of trace metals (Fe, Zn, Mn, and Pb) revealed, children are at 'low risk' and 'medium' risk with Ni and Cu. The carcinogenic risk index indicated 93% of samples were high Ni induced cancer risk for children, and 87% for adults due to long term ingestion (drinking water intake) pathway. Studies specific on placer mineral deposited coastal region of India are not sufficiently reported with a focus on the above perspectives. Growing need of rare earths for material, device and energy applications, placer mineral explorations can destabilise the coastal hydrosphere. Interrelations of mineral soil - water chemistry prevailed and health hazard predicted would kindle a set of sustainable deliberations. This study summarises the drinking and industrial use of coastal groundwater for future development and human well-being on the basis of quality criteria, corrosion proneness, water stability and health risk factors.