Groundwater of alluvial fan plains is the foremost water source, especially in arid/semiarid regions. Its contaminants are big issues for water supply and public health concern. To reveal the ...groundwater chemistry, contaminants sources and health threats in alluvial aquifers, 81 groundwaters were collected from a typical alluvial fan plain of northern China for nitrogen, fluoride and major ions analysis. Statistical analysis and hydrochemical diagrams as well as human health risk assessment were performed. Nitrate is widely distributed and 53% of groundwaters exceed the permissible limit with the maximum concentration up to 326 mg/L. The distributions of nitrite, ammonia and fluoride contaminants are sporadic in spatial, and the concentrations of fluoride in groundwaters are slightly beyond the permissible limit of 1 mg/L. The hydrochemical facies shift from HCO3-Ca or Mixed HCO3-Na·Ca type to Mixed Cl-Mg·Ca and ClCa type with the increase of nitrate content. Two factors (Factor-1 and Factor-2) are extracted by factor analysis and account 63% of the total variances. The positive loading of F− and negative loading of NO3− on Factor-2 reveal geogenic and anthropogenic origins, respectively. The significant positive loadings of TDS, TH, SO42−, Cl−, Ca2+, Mg2+ on Factor-1 reveal the governing mechanisms on groundwater chemistry by intermixed sources of geogenic origins and anthropogenic inputs. Hydrogeochemical evolution in the study area is driven by both water-rock interaction and anthropogenic forces. Anthropogenic inputs/influences are the dominated forces increasing groundwater nitrate content and salinity in the piedmont zone and the residential and industrial zone of the southeastern lower parts, and would pose potential non-carcinogenic risks to various populations via oral intake pathway. Rational measures should be taken to protect groundwater quality out of the threats of anthropogenic pollution. The geogenic fluoride in groundwater would threat the health of children through oral pathway and should be also concerned.
The driving forces of groundwater chemistry in alluvial fan plains were revealed using integrated approach of factor analysis and geostatistical modelling.
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•Groundwater quality in alluvial fan plains is potentially threatened by both geogenic and anthropogenic contaminants.•Anthropogenic contamination inputs can lead to groundwater chemical facies evolution towards salty types.•Factor analysis coupled with geostatistical modelling was used to reveal the hydrogeochemical driving forces in spatial.•Anthropogenic nitrate can pose higher health risk than nitrite, ammonia and geogenic fluoride in present alluvial aquifer.
At high concentrations nitrate is considered a serious environmental pollutant which degrades the quality of ground and surface waters. Such high nitrate concentrations (>50 mg NO3/L) have been ...observed for decades in the alluvial aquifer in the Varaždin region of Croatia. Here we employ a novel cross disciplinary approach (dual isotopes, chemical, bacteria diversity and mixing modelling) to determine sources of nitrate and processes that can influence nitrate concentration within this vulnerable alluvial aquifer. Ten groundwater wells were sampled across the region and in different hydrological conditions for basic chemical, stable isotopes (δ18O-H2O, δ2H-H2O, δ15N-NO3 and δ18O-NO3), and bacterial diversity analyses. In addition, solid samples, i.e. soil samples and fertilizers were collected and analysed for bulk δ15N. The primary nitrate sources were manure, sewage, soil organic N, and ammonia fertilizers, however we observe no clear evidence to indicate that synthetic fertilizers are a major contributor to groundwater nitrate concentrations. Whilst denitrification was observed in the parts of the study area with dissolved oxygen (DO) deficiency, i.e. anoxic conditions, nitrification has been identified as the major process responsible for nitrate behaviour within the aquifer system. Our results will facilitate the creation of a conceptual model of nitrate behaviour in the study area and from this, a numerical groundwater nitrate transport model. These data, understanding of nitrate dynamics and subsequent models will be critical for future sustainable water and agricultural management of the study area.
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•A novel multi proxy approach was used to understand nitrate in alluvial system.•Agriculture and sewage water has considerable impact nitrate concentrations.•Nitrification was identified as the main process controlling nitrogen dynamics.•Denitrification was site-specific and temporally limited.
Sediment interfaces in alluvial aquifers have a disproportionately large influence on biogeochemical activity and, therefore, on groundwater quality. Previous work showed that exports from ...fine-grained, organic-rich zones sustain reducing conditions in downstream coarse-grained aquifers beyond the influence of reduced aqueous products alone. Here, we show that sustained anaerobic activity can be attributed to the export of organic carbon, including live microorganisms, from fine-grained zones. We used a dual-domain column system with ferrihydrite-coated sand and embedded reduced, fine-grained lenses from Slate River (Crested Butte, CO) and Wind River (Riverton, WY) floodplains. After 50 d of groundwater flow, 8.8 ± 0.7% and 14.8 ± 3.1% of the total organic carbon exported from the Slate and Wind River lenses, respectively, had accumulated in the sand downstream. Furthermore, higher concentrations of dissolved Fe(II) and lower concentrations of dissolved organic carbon in the sand compared to total aqueous transport from the lenses suggest that Fe(II) was produced in situ by microbial oxidation of organic carbon coupled to iron reduction. This was further supported by an elevated abundance of 16S rRNA and iron-reducing (gltA) gene copies. These findings suggest that organic carbon transport across interfaces contributes to downstream biogeochemical reactions in natural alluvial aquifers.
A hydrochemical study on the coastal aquifers were collected initiated to determine the factors affecting the groundwater chemistry in South India. 48 groundwater samples from bore wells during post ...monsoon period. The samples were measured for in situ parameters and major ions following the standard procedures. The analyzed results were further interpreted using geochemical plots, ionic ratios, water quality indices, geochemical modeling and statistics. pH values in the groundwater ranged from 6.6 to 8.0 and alkaline in nature. The average value of EC was 7155 μS/cm and higher values were mostly distributed along the coastal region of the study area. From the Piper plot, hydrochemical evolution path was identified, from Ca−HCO3 (recharge waters) to mixed Ca-Mg-Cl (reverse ion exchange waters) through Ca-Cl types (leachate waters), indicating the reverse ion exchange and seawater intrusion. Saturation index reflected that Calcite was oversaturated due to availability of Ca and HCO3 ions. Factor analysis further improved the understanding of the major controlling hydrochemical processes for groundwater chemistry. The hydrochemistry of the coastal aquifer was affected by several factors such as dissolution, water-rock interaction, reverse ion exchange, seawater intrusion, and influence of minor agricultural. The water quality assessment showed that the concentration of most of the parameters exceeded the standards limit, and considered as unsuitable for drinking purposes. But they are inferred to be suitable for agricultural purposes according to SAR, Na%, RSC and PI.
The Middle Western Cheliff plain hosts an important alluvial aquifer that is exploited for various uses including drinking water supply, irrigation and industry. This study aims to provide a ...hydrogeochemical characterisation of groundwater by using statistical methods and binary diagrams, as well as to evaluate the physico-chemical quality of groundwater by using the water quality index (WQI). Moreover, parametric indices such as SAR and %Na were used to evaluate the suitability of groundwater for irrigation. The hydrochemical approach based on results of 45 analyses of groundwater samples for the dry period 2019 enabled the determination of the most dominant chemical facies, which was chloride, sulphate, calcic and magnesium. The binary diagrams used indicated that the water-rock interaction and the evaporitic phenomenon are major geochemical processes that control the mineralisation of groundwater. The evaluation of groundwater quality for drinking water supply using WQI provided results with values ranging from 45.95 to 194.78, and above 60% of samples were classified into the category of excellent to good quality (WQI < 100), while the remaining 40% of water samples were classified in the category of poor quality for drinking (WQI > 100). However, the quality of groundwater is mostly acceptable for irrigation, mostly for plants with salinity-tolerant in drained soils.
The rapid development of Rayong Province has resulted in increased demands on groundwater usage. This has potentially induced the release of contaminants such as arsenic (As), among others (i.e., NO
...3
−
, PO
4
3−
) from various land use types—especially in intensive agricultural areas and heavy industrial areas, including landfill sites. The objectives of this research are to investigate the As speciation and groundwater chemistry occurring due to different hydrogeological settings and the influence of human activities and to explain the mechanism of As release in the coastal alluvial aquifers in Rayong Province using multivariate statistical techniques and hydrogeochemical modeling (PHREEQC). Six major water facies, mainly consisting of Ca–Na–HCO
3
–Cl and Ca–Na–Cl, were included in the hydrochemical analysis. Arsenic levels were inversely correlated with NO
3
−
, SO
4
2−
, DO, and ORP, confirming the reducing environment in the groundwater system. The results from the PHREEQC model show that most wells were strongly under-supersaturated with respect to arsenorite, scorodite, and arsenic pentoxide. Arsenic (As) is probably derived from the dissolution of Fe oxide and hydroxide (i.e., Fe(OH)
3
, goethite, maghemite, and magnetite). The multivariate statistical techniques revealed that the As species mainly consisted of As(III), governed by the reducing environment, while As(V) may be desorbed from Fe oxide and hydroxide as the pH increases. Anthropogenic inputs and intensive pumping may enhance the reducing environment, facilitating the release of As(III) into the groundwater. The knowledge gained from this study helps to better understand the mechanisms of As contamination in coastal groundwater aquifers, which is useful for groundwater management, including the optimum pumping rate and long-term monitoring of groundwater quality.
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•Optimized water recharge using infiltration galleries prevents groundwater depletion.•Surrogate-based simulation–optimization developed the recharge management model.•Simulation model output ...generated the input–output patterns for surrogate models.•Bayesian and ASHA optimizations automatically selected the best surrogate model.•Planned recharge aids optimized water injection and groundwater depletion control.
The Mississippi River Valley Alluvial Aquifer (MRVAA) is the main irrigation source for the Lower Mississippi River Basin. Irrigation water abstraction to meet the demands for extensive agricultural practices has contributed to groundwater depletion in this area. A managed aquifer recharge (MAR) approach has been proposed in this geographic location to minimize the impact of pumping on groundwater depletion. However, it is essential to determine the optimal amount of water to be injected through a MAR technique to reduce the decline in groundwater heads. This paper utilizes a coupled simulation–optimization (S-O) approach to estimate the optimal recharge volume into the alluvial aquifer through infiltration galleries. The aquifer processes were simulated using a physically based, three-dimensional finite-difference numerical code, MODFLOW. The MODFLOW model was calibrated and validated using the recharge rates and available groundwater head data for 26 months (27 February 2020 to 27 May 2022). The calibrated and validated models were then deployed within the coupled S-O approach to develop an aquifer recharge management model to estimate optimal groundwater recharge rates to minimize groundwater decline. Computational efficiency of the aquifer recharge management model was achieved using surrogate models that accurately reproduced the groundwater heads calculated by MODFLOW. Our evaluation demonstrates that a planned transient groundwater recharge strategy, obtained as a solution of the surrogate model based coupled S-O approach, is a useful management strategy for optimized water recharge and groundwater depletion control. This study shows the promise of the surrogate model based coupled S-O approach to potentially reduce groundwater depletion in the MRVAA by utilizing optimized recharge rates at the infiltration galleries. This work has potential applications to other aquifers and geographic locations to mitigate groundwater depletion issues due to extensive agricultural practices.
Effective response to groundwater salinity in the developing world may critically safeguard drinking-water supplies. Groundwater resources throughout rural Africa are exploited by a vast and ...increasing number of hand-pumped boreholes for community supply. Our research in TA Ngabu (Shire Valley), Southern Malawi aims to: define groundwater-salinity problem occurrence within the semi-arid alluvial-valley aquifer, rural developing-world setting; critique current capacity to respond; and, to discuss future response options - in particular considering the need to explore alternative options that boldly go beyond the world of hand-pumped groundwater supply. Salinity problem definition was achieved through survey of 419 hand-pumped boreholes that revealed widespread brackish groundwater leading to non-potable (unpalatable) drinking-water supplies. Persistent non-functionality or abandonment of boreholes was typically ascribed to salinity. Whilst salinity is conceptualised to arise from shallow-groundwater evaporation, formation-evaporite dissolution and faulted-area upwelling, sparse data locally renders attribution of salinity sources to individual boreholes difficult. There is a significant need to better resolve the vertical distribution of salinity and local controlling processes. Problem response capacity was hampered by multiple factors, including, sector inertia, low drilling costs compromising water-point integrity, and lack of technical vision for alternatives. Various recommendations are made to improve response capacity continuing to work at the hand-pump supply scale. However, in areas where salinity is significant, exploring the feasibility of other options is advocated in conjunction with technical capacity development. Groundwater options may utilise high borehole yields possible from alluvial aquifers, grossly under-exploited by hand pumps. Groundwater at depth, albeit of unknown quality typically, or pipeline transfers of probable good-quality groundwater from valley-margin units, should be considered. Surface-water pipeline supplies may be viable for (growing) population centres. Canal-fed irrigation schemes (pending for the area), should be multiple-use, protective of groundwater and embrace pipeline drinking-water supply and managed-aquifer-recharge opportunities. Advancing desalination technologies, although presently unaffordable, should be kept under review.
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•Effective response to developing-world groundwater salinity to safeguard water supply•Salinity problem defined via conceptual model - salinity survey - water-point mapping.•Groundwater salinity response capacity constrained in Malawi by multiple factors.•Need to evaluate options beyond model-supply paradigm of hand-pumped borehole supply•Feasibility study of larger groundwater or surface-water supply alternatives
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