This study assessed the geochemistry and quality of groundwater in the Hongdunzi coal mining area in northwest China and investigated the mechanisms governing its hydrogeochemistry and the hydraulic ...connectivity between adjacent aquifers. Thirty-four groundwater samples were collected for physicochemical analyses and bivariate analyses were used to investigate groundwater quality evolution. The groundwater in the mine was determined to be neutral to slightly alkaline, with high levels of salinity and hardness; most samples were of SO
4
·Cl–Na type. Fluoride and nitrate pollution in the confined aquifers were identified, primarily sourced from coals. Natural geochemical processes, such as mineral dissolution, cation exchange, and groundwater evaporation, largely control groundwater chemistry. Anthropogenic inputs from agricultural and mining activities were also identified in both shallow unconfined aquifers and the deeper confined aquifers, respectively. It was determined that the middle confined aquifer has a high hydraulic connectivity with the lower coal-bearing aquifer due to developed fractures. Careful management of the overlying aquifers is required to avoid mine water inrush geohazards and groundwater quality deterioration. The groundwater in the mining area is generally of poor quality, and is unsuitable for direct human consumption or irrigation. Na
+
, SO
4
2−
, Cl
−
, F
−
, TH, TDS, NO
3
−
, and COD
Mn
are the major factors responsible for the poor quality of the phreatic water, while Na
+
, SO
4
2−
, F
−
, and TDS are the major constituents affecting the confined groundwater quality. This study is beneficial for understanding the impacts of coal mine development on groundwater quality, and safeguarding sustainable mining in arid areas.
An understanding of the vertical variations in hydrogeochemical processes in various aquifers and quality suitability assessment is crucial for the utilization of groundwater in the Ningtiaota ...coalfield of Ordos Basin, Northwestern China. Based on 39 water samples collected from surface water (SW), Quaternary pore water (QW), weathered fissure water (WW), and mine water (MW), we conducted self-organizing maps (SOM) algorithm, multivariate statistical analysis (MSA), and classical graphical methods to elucidate the mechanisms controlling the vertical spatial variations in SW and groundwater chemistry and conducted a health risk assessment. The findings indicated that the hydrogeochemical type showed a transition from the HCO
3
−
-Na
+
type in SW to the HCO
3
−
-Ca
2+
type in QW, then to the SO
4
2−
-Mg
2+
type in WW, and back to HCO
3
−
-Na
+
type in MW. Water–rock interaction, silicate dissolution, and cation exchange were the main hydrogeochemical processes in the study area. Additionally, groundwater residence time and mining operations were critical external factors that affect water chemistry. Contrary to phreatic aquifers, confined aquifers featured greater circulation depth, water–rock interactions, and external interventions leading to worse quality and higher health risks. Water quality surrounding the coalfield was poor, causing it to be undrinkable, with excessive SO
4
2−
, arsenic (As), and F
−
, etc. Approximately 61.54% of SW, all of QW, 75% of WW, and 35.71% of MW can be used for irrigation.
Heat has been widely applied to trace groundwater‐surface water exchanges in inland environments, but it is infrequently applied in coastal sediment where head oscillations induce periodicity in ...water flux magnitude/direction and heat advection. This complicates interpretation of temperatures to estimate water fluxes. We investigate the convolution of thermal and hydraulic signals to assess the viability of using heat as a tracer in environments with tidal head oscillations superimposed on submarine groundwater discharge. We first generate sediment temperature and head time series for conditions ranging from no tide to mega‐tidal using a numerical model (SUTRA) forced with periodic temperature and tidal head signals. We then analyze these synthetic temperature time series using heat tracing software (VFLUX2 and 1DTempPro) to evaluate if conventional terrestrial approaches to infer fluxes from temperatures are applicable for coastal settings. We consider high‐frequency water flux variability within a tidal signal and averaged over tidal signals. Results show that VFLUX2 analytical methods reasonably estimated the mean discharge fluxes in most cases but could not reproduce the flux variability within tidal cycles. The model results further reveal that high‐frequency time series of water fluxes varying in magnitude and direction can be accurately estimated if paired temperatures and hydraulic heads are analyzed using numerical models (e.g., 1DTempPro) that consider both dynamic hydraulic gradients and thermal signals. These results point to the opportunity to incorporate pressure sensors within heat tracing instrumentation to better assess sub‐daily flux oscillations and associated reactive processes.
Plain Language Summary
Coastal water bodies are hydrologically connected to underlying aquifers or sediment, which allows for exchanges of water, heat, and chemicals between these domains. These interactions can influence the temperatures and chemistry of coastal water bodies and impact ecosystems. Thus, it is important for us to measure the variability of these exchanges in space and time to better understand their impacts on coastal water quality. Presently, it is challenging to accurately measure how these exchanges vary in time due to tidal variability. In this study, we propose that sediment temperature and groundwater pressure data can be measured and analyzed to estimate these vertical exchanges in coastal settings. We use model results to reveal that if both the temperature and water pressure in coastal sediments are recorded, models can be applied to interpret measured data and quantify exchange between coastal sediment and overlying coastal water bodies.
Key Points
Temperature and hydraulic head exhibit multi‐frequency periodicity in coastal sediment due to diurnal and semi‐diurnal forcing
Multi‐frequency signal convolution complicates application of methods using diurnal temperature signals to trace vertical water exchange
These limitations can be overcome by using dynamic sediment porewater head and temperature in conjunction to estimate water fluxes
Water reuse is receiving unprecedented attention as many areas around the globe attempt to better-manage their fresh water resources. Wastewaters in coastal regions may contain elevated levels of ...bromide (Br–) and iodide (I–) from seawater intrusion or high mineral content in the source waters. Disinfection of such wastewater is essential to prevent the spread of pathogens; however, little is known about the toxicity of the treated wastewater. In this study, we evaluated the genotoxicity to Chinese hamster ovary (CHO) cells induced by municipal secondary wastewater effluent amended with elevated Br– and I– after disinfection by chlorine, chloramines, or ozone. We calibrated and applied an N-acetylcysteine (NAC) thiol reactivity assay as a surrogate for thiol reactivity with biological proteins (glutathione) of wastewater samples. Chlorination of wastewaters produced CHO cell genotoxicity comparable to chloramination, 3.9 times more genotoxic than the nondisinfected controls. Ozonated wastewater was at least 3 times less genotoxic than the samples treated with chlorine-based disinfectants and was not significantly different compared with the nondisinfected controls. Positive and significant correlations were observed among genotoxicity, cytotoxicity, and NAC thiol reactivity for all disinfected samples. These results indicate that the ozonation of wastewater with high Br– and I– levels may yield organics with lower genotoxicity to CHO cells than chlorine-based disinfection. NAC thiol reactivity, although excluding the possible effect of bromate from ozonation in this work, could be used as a rapid in chemico screen for potential genotoxicity and cytotoxicity in mammalian cells exposed to disinfected wastewaters.
Water resources planning and management by water utilities have traditionally been based on consideration of water availability. However, the reliability of public water supplies can also be ...influenced by the quality of water bodies. In this study, we proposed a framework that integrates the analysis of risks of inadequate water quality and risks of insufficient water availability. We have developed a coupled modeling system that combines hydrological modeling of river water quantity and quality, rules for water withdrawals from rivers into storage reservoirs, and dynamical simulation of harmful algal blooms in storage reservoirs. We use this framework to assess the impact of climate change, demand growth, and land‐use change on the reliability of public water supplies. The proposed method is tested on the River Thames catchment in the south of England. The results show that alongside the well‐known risks of rising water demand in the south of England and uncertain impacts of climate change, diffuse pollution from agriculture and effluent from upstream waste water treatment works potentially represent a threat to the reliability of public water supplies in London. We quantify the steps that could be taken to ameliorate these threats, though even a vigorous pollution‐prevention strategy would not be sufficient to offset the projected effects of climate change on water quality and the reliability of public water supplies. The proposed method can help water utilities to recognize their system vulnerability and evaluate the potential solutions to achieve more reliable water supplies.
Key Points
Proposes an integrated water quality‐quantity model,including ion rules and reservoir water quality,for PWS reliability assessment
Assesses the impact of land‐use change, and potential mitigations, on water supply reliability
Applies a novel climate dataset to explore hydrological variability and change
This study explores the hydrogeochemical processes and groundwater quality of different aquifers in the Caojiatan coal mine in the Ordos Basin, northwestern China, using classical graphical methods ...and multivariate analysis. The study found that surface water and groundwater in the Quaternary unconsolidated aquifer (UA) and weathered bedrock zone (WZ) have a HCO
3
–Ca·Mg hydrochemical type, while the groundwater in the Jurassic Zhiluo aquifer (ZA) and Jurassic Yanan aquifer (YA) are predominantly of the HCO
3
–Na type. Rock weathering, silicate dissolution, and reverse cation exchange are the dominant hydrogeochemical processes controlling the water chemical variables in the study area. In addition, variations in the hydraulic conductivities and TDS in different aquifers indicate that groundwater residence time is also the main factor controlling the chemical variables. Groundwater in the UA and WZ is suitable for drinking and irrigation, with low ion concentrations. However, the groundwater in ZA and YA must be treated before drinking, because of the high pH value. The excessive concentrations of F
-
, and high sodium adsorption ratio Na%, and residual sodium carbonate values also make the water unsuitable for irrigation. Mining activities can significantly impact the circulation and occurrence of natural groundwater. Once the groundwater in WZ becomes mine water, it becomes contaminated because of the mixing process with groundwater in ZA and YA. Further, undissolved coal slime and large quantities of oil leaking from fully mechanized mining equipment increase the COD
Mn
levels in the mine water, making the levels higher than in natural groundwater and beyond permissible limits for drinking.
Accurately measuring water use by the economy is essential for developing reliable models of water resource availability. Indeed, these models rely on retrospective analyses that provide insights ...into shifting human population demands and adaptions to water shortages. However, accurate, methodologically consistent, empirically authentic, and spatiotemporally comprehensive historical datasets for water withdrawals are scarce. Herein, we present a reanalysis of annual resolution (1950–2016) historical data set on irrigation, electric power, and public supply water withdrawal within the conterminous United States (US) at the county‐level, and, for power plants, at the site‐level. To estimate electric power water use, we synthesized a historically comprehensive list of generators and historic patterns in generation across fuels, prime movers, and cooling technologies. Irrigation water use estimation required building a crop‐demand model that utilized historical information on irrigated acreage for crops and golf courses, stage‐specific crop water demand, and climate information. To estimate public water supply use, we developed a random forest model constructed from information on population, infrastructure, climate, and land cover. These estimates generally agree with total county and state water use information provided by the US Geological Survey (USGS) water use circular and estimates generated from independent studies for specific years. However, we also observed discrepancies between our estimates and USGS data that appear to be caused by inconsistencies in the methods used by the USGS's primary data sources at the state level over decades of data collection, highlighting the importance of reanalysis to yield spatiotemporally consistent and intercomparable estimates of water use.
Key Points
Spatiotemporally comprehensive water use data are needed to characterize water resource availability and model long‐term hydrologic changes
We present an annual (1950–2016) data set on US agriculture, electric power, and public supply water use at the county level
The data set provides new spatiotemporally rich information compiled using consistent reanalysis methods to inform multi‐sectoral research
Multiple chemical forms of nitrogen in urban stormwater make its management challenging. Sixteen storm events were monitored and analyzed for total nitrogen (TN), particulate organic nitrogen (PON), ...nitrate (NO3-N), nitrite (NO2-N), ammonium (NH3-N), and dissolved organic nitrogen (DON) in stormwater runoff and in treated discharge through a conventional bioretention cell. Influent PON can be effectively removed via bioretention sedimentation/filtration, NH3-N by ion exchange/sorption, and NO2-N by oxidation. However, significant DON and NO3-N leached from the bioretention cell, resulting in only 9% net overall TN concentration reduction. Captured PON and vegetation detritus in the bioretention cell can be leached as DON or mineralized into NO3-N. The effluent N is dominated by NO3-N (46%) and DON (42%). Therefore, in addition to creating denitrification conditions for NO3-N, preventing DON leaching is also critical for effective nitrogen removal though bioretention systems. The bioretention cell exhibited a moderate mass load reduction for TN (41%), which mainly results from runoff volume reduction.
To study the hydrochemical characteristics of main aquifers in Jiaojia gold mine area and their changing regularities, exploring the main sources of mine water, 244 water samples from the main ...aquifers and mine water were collected. The principal components were extracted by factor analysis and shows that with the increase of depth, the concentration of Na
+
and Cl
−
increased significantly, the water–rock interaction becomes stronger, the water quality develops towards salinization, the total water quality, hydrodynamic conditions, and the connection between groundwater and surface water becomes worse. We extracted the main influential discriminant indexes using principal component analysis (PCA), that is, pH, MH
4
+
, NO
3
−
, NO
2
−
, total hardness, TDS, Fe
3+
, SO
4
2−
, Cl
−
and F
−
. We weighted the extracted discriminant indexes using entropy weight method (EWM), that is in turn, 0.0002, 0.1883, 0.1272, 0.2061, 0.0680, 0.0613, 0.1461, 0.0573, 0.0844, and 0.0613. 55 water samples from each aquifer in the last 5 years were analyzed by hierarchical cluster analysis (HCA), and the relational degree between the main aquifers and mine water was judged by the distance between them; result shows that the main source of mine water is from the hanging wall of fault aquifer, followed by the footwall of fault aquifer. The mine water has little connection with bedrock weathered fractured aquifer, and almost no connection with Quaternary porous aquifer. The PCA–EWM–HCA model established in this paper provides a theoretical basis for identification of mine water inrush source and protection of underground water resources.
This paper presents a case study of an optimized combination of mine water control, treatment, utilization and reinjection to achieve the zero discharge of mine water. Mine water has been considered ...a hazard and pollution source during underground mining, so most mining enterprises directly discharge mine water to the surface after simple treatment, resulting in a serious waste of water. Moreover, discharging a large amount of mine water can destroy the original groundwater balance and cause serious environmental problems, such as surface subsidence, water resource reduction and contamination, and adverse impacts on biodiversity. The Zhongguan iron mine is in the major groundwater source area of the Hundred Springs of Xingtai, which is an area with a high risk of potential subsidence. To optimize the balance between mining and groundwater resources, a series of engineering measures was adopted by the Zhongguan iron mine to realize mine water control, treatment, utilization, and reinjection. The installation of a closed grout curtain has greatly reduced the water yield of deep stopes in the mine; the effective sealing efficiency reaches 80%. Nanofiltration membrane separation was adopted to treat the highly mineralized mine water; the quality of the produced water meets China’s recommended class II groundwater standard. Low-grade heat energy from the mine water is collected and utilized through a water-source heat pump system. Finally, zero mine water discharge is realized through mine water reinjection. This research provides a beneficial reference for mines with similar geological and hydrogeological conditions to achieve environmentally sustainable mining.
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