The changing nature of groundwater in the global water cycle.

In recent decades, climate change and other anthropogenic activities have substantially affected groundwater systems worldwide. These impacts include changes in groundwater recharge, discharge, flow, storage, and distribution. Climate-induced shifts are evident in altered recharge rates, greater groundwater contribution to streamflow in glacierized catchments, and enhanced groundwater flow in permafrost areas. Direct anthropogenic changes include groundwater withdrawal and injection, regional flow regime modification, water table and storage alterations, and redistribution of embedded groundwater in foods globally. Notably, groundwater extraction contributes to sea level rise, increasing the risk of groundwater inundation in coastal areas. The role of groundwater in the global water cycle is becoming more dynamic and complex. Quantifying these changes is essential to ensure sustainable supply of fresh groundwater resources for people and ecosystems.

Microplastics contamination of groundwater: Current evidence and future perspectives. A review.

Groundwater is a primary water source which supplies more than 2 billion people. The increasing population and urbanization of rural areas stresses and depletes the groundwater systems, reducing the groundwater quality. Among the emerging contaminants, microplastics (MPs) are becoming an important issue due to their persistency in the environment. Seepage through the pores and fractures as well as the interaction with colloidal aggregates can partially affect the MPs dynamics in the subsoil, making the detection of the MPs in the groundwater systems challenging. Based on literature, a critical analysis of MPs in groundwater is presented from a hydrogeological point of view. In addition, a review of the MPs data potentially affecting the groundwater systems are included. MPs in groundwater may have several sources, including the atmosphere, the interaction with surface water bodies, urban infrastructures, or agricultural soils. The characterization of both the groundwater dynamics and the heterogeneity of MPs is suggested, proposing a new framework named "Hydrogeoplastic Model". MPs detection methods aimed at characterizing the smaller fragments are necessary to clarify the fate of these contaminants in the aquifers. This review also aims to support future research on MP contamination in groundwater, pointing out the current knowledge and the future risks which could affect groundwater resources worldwide.

Groundwater Complexity in Urban Catchments: Shenzhen, Southern China.

Groundwater interactions with surface water and sewers in an urban setting are complex, and classic hydrogeological approaches must be combined with anthropogenic elements to characterize them. The level of detail needed to understand these interactions is illustrated by the analysis of an urban subcatchment in the megacity of Shenzhen in southern China that has had a drastic urban expansion in the last 40 years. The study area is characterized by the Yanshanian granite that is widespread across southern-eastern China. The urban setting is studied using multitemporal analysis of satellite images, borehole investigations and field surveys. Given the local hydrostratigraphy, a conceptual model was developed to identify the physical and anthropogenic factors that regulate the urban groundwater system. Based on the conceptual model and the data collected from the field or compiled from the literature, the average annual effective recharge is estimated to be 290 mm/year, after the urbanization process. From rural to urban conditions, it is estimated that the effective recharge increased by 170% and sewers intercept at least 23% of the effective recharge. Groundwater captured by sewers reduces river flows and increases the required capacity and costs for waste water treatment plants.