Integrated Geothermal-CO2 Reservoir Systems: Reducing Carbon Intensity through Sustainable Energy Production and Secure CO2 Storage

AbstractLarge-scale geologic CO2 storage (GCS) can be limited by overpressure, while geothermal energy production is often limited by pressure depletion. We investigate how synergistic integration of these complementary systems may enhance the viability of GCS by relieving overpressure, which reduces pore-space competition, the Area of Review, and the risks of CO2 leakage and induced seismicity, and by producing geothermal energy and water, which can defray parasitic energy and water costs of CO2 capture

Emerging organic contaminants in the river Ganga and key tributaries in the middle Gangetic Plain, India:Characterization, distribution & controls

The presence and distribution of emerging organic contaminants (EOCs) in freshwater environments is a key issue in India and globally, particularly due to ecotoxicological and potential antimicrobial resistance concerns. Here we have investigated the composition and spatial distribution of EOCs in surface water along a ∼500 km segment of the iconic River Ganges (Ganga) and key tributaries in the middle Gangetic Plain of Northern India. Using a broad screening approach, in 11 surface water samples, we identified 51 EOCs, comprising of pharmaceuticals, agrochemicals, lifestyle and industrial chemicals. Whilst the majority of EOCs detected were a mixture of pharmaceuticals and agrochemicals, lifestyle chemicals (and particularly sucralose) occurred at the highest concentrations. Ten of the EOCs detected are priority compounds (e.g. sulfamethoxazole, diuron, atrazine, chlorpyrifos, perfluorooctane sulfonate (PFOS), perfluorobutane sulfonate, thiamethoxam, imidacloprid, clothianidin and diclofenac). In almost 50% of water samples, sulfamethoxazole concentrations exceeded predicted no-effect concentrations (PNECs) for ecological toxicity. A significant downstream reduction in EOCs was observed along the River Ganga between Varanasi (Uttar Pradesh) and Begusarai (Bihar), likely reflecting dilution effects associated with three major tributaries, all with considerably lower EOC concentrations than the main Ganga channel. Sorption and/or redox controls were observed for some compounds (e.g. clopidol), as well as a relatively high degree of mixing of EOCs within the river. We discuss the environmental relevance of the persistence of several parent compounds (notably atrazine, carbamazepine, metribuzin and fipronil) and associated transformation products. Associations between EOCs and other hydrochemical parameters including excitation emission matrix (EEM) fluorescence indicated positive, significant, and compound-specific correlations between EOCs and tryptophan-, fulvic- and humic-like fluorescence. This study expands the baseline characterization of EOCs in Indian surface water and contributes to an improved understanding of the potential sources and controls on EOC distribution in the River Ganga and other large river systems

Quantifying the impacts of groundwater abstraction on Ganges river water infiltration into shallow aquifers under the rapidly developing city of Patna, India

Study region Patna is located on the southern bank of the River Ganges in Bihar, India. Rapid population growth over the past few decades has driven an increase in groundwater abstraction from aquifers under the city. Study focus This study exeplores the pumping-induced water exchange between the River Ganges and groundwater under transient conditions between 2009 and 2015, using a numerical simulation. The deterministic water exchange model within an uncertainty quantification was used to reveal the controlling factors affecting river water infiltration. New hydrological insights for the region Modelling reveals that under baseline (eno pumping) conditions, the dominant (~ 91% of the year) flow direction is from the aquifer to the river, which reverses (~ 9% of the year) when the river stage is high. When a municipal pumping well is implemented, river water infiltration into the aquifer increases to 68% of the year. The groundwater pumping rate is found to be the most important factor affecting the river water infiltration, whilst the groundwater table level is most sensitive to the well distance from the river, followed by pumping rate. Optimizing the location, depth and pumping rate of new wells in the area could mitigate fluvial contamination of the aquifer and help maintain groundwater levels

Redox hydrogeochemistry of organic rich floodplain exemplified by Ammer river

Diffusive groundwater pollution caused by agricultural and atmospheric inputs is a pressing issue in environmental management worldwide. Various researchers have studied nitrate contamination since the substantial increase of nitrogen fertilization in agriculture starting in the second half of the 20th century. This study addresses large scale reactive solute transport in typical landscapes and aquifers exemplified by geological analogues of southwestern Germany.. Fate of nitrate and other solutes (e.g. agricultural nitrate, ammonium, natural sulfate and dissolved organic carbon) was studied in a typical small river floodplain. Reactive transport model of Ammer river floodplain shows that agriculture nitrate is reduced rapidly in the Ammer floodplain sediments. However, there is a potential for geogenic production of ammonium in sediment layers high in organic carbon and peat, which might be a major source of nitrate in the drains. Part of the nitrate in drains and creeks in the Ammer valley thus could be of geogenic origin. Such findings are relevant for regional land and water quality management

Exposure-time based modeling of nonlinear reactive transport in porous media subject to physical and geochemical heterogeneity

Transport of reactive solutes in groundwater is affected by physical and chemical heterogeneity of the porous medium, leading to complex spatio-temporal patterns of concentrations and reaction rates. For certain cases of bioreactive transport, it could be shown that the concentrations of reactive constituents in multi-dimensional domains are approximately aligned with isochrones, that is, lines of identical travel time, provided that the chemical properties of the matrix are uniform. We extend this concept to combined physical and chemical heterogeneity by additionally considering the time that a water parcel has been exposed to reactive materials, the so-called exposure time. We simulate bioreactive transport in a one-dimensional domain as function of time and exposure time, rather than space. Subsequently, we map the concentrations to multi-dimensional heterogeneous domains by means of the mean exposure time at each location in the multi-dimensional domain. Differences in travel and exposure time at a given location are accounted for as time difference. This approximation simplifies reactive-transport simulations significantly under conditions of steady-state flow when reactions are restricted to specific locations. It is not expected to be exact in realistic applications because the underlying assumption, such as neglecting transverse mixing altogether, may not hold. We quantify the error introduced by the approximation for the hypothetical case of a two-dimensional, binary aquifer made of highly-permeable, non-reactive and low-permeable, reactive materials releasing dissolved organic matter acting as electron donor for aerobic respiration and denitrification. The kinetically controlled reactions are catalyzed by two non-competitive bacteria populations, enabling microbial growth. Even though the initial biomass concentrations were uniform, the interplay between transport, non-

Diversity of bacteria in cloud water collected at a National Atmospheric Monitoring Station in Southern China

Bacteria in the atmosphere affect human health and atmospheric characteristics, however, few studies have investigated bacteria in high altitude areas in China, especially in clouds and fog. In this study, the bacterial community structures of three cloud water samples, collected at the Nanling national atmospheric monitoring station (112 degrees 53'56 '' E, 24 degrees 41'56 '' N) in China, were studied by combining culture-based approach and high-throughput sequencing technology. The results showed that the dominant bacteria in cloud water samples were Proteobacteria (71.36%), followed by Actinobacteria (21.72%) and bacteroidetes (6.43%), but bacterial species identified using a culture-based approach were < 1% of the total bacteria. NO2, SO42-, and pH value were related to the community structures of bacterial, indicating anthropogenic emissions possibly enhanced the variety of bacterial communities in cloud water