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Benthic habitats in shallow oxbow lakes may serve as permanent nitrogen (N) sinks by facilitating denitrification. Oxbow sediments may also accumulate nutrients through uptake, deposition and heterotrophic N2 fixation, and ultimately provide a significant internal source of N and phosphorus (P) through sediment release to the water column. To better understand nutrient source-sink dynamics in oxbow lakes, we explored seasonal and habitat specific patterns in sediment dissolved dinitrogen gas (N2-N) and nutrient flux within an oxbow in the Mississippi Alluvial Plain. Time series models indicate a higher probability of positive N2-N fluxes in fall through spring, significant negative summer fluxes, and clear differences among habitats with net annual N2-N fluxes, ranging from − 2.34 g m−2 Y−1 in open water habitat to 0.26 g m−2 Y−1 in shoreline areas. Integrated lake-wide N2-N sediment flux estimates were negative indicating the significant role of net N2 fixation. More complex models explained similar amounts of variation (Adj. R2 = 0.57 vs. 0.45) and indicated that benthic N2-N fluxes were associated with changes in temperature, dissolved inorganic N, sediment oxygen demand, and sediment carbon:N ratios. Ammonium and P flux from sediments were substantial across all habitats and internal N regeneration far outpaced removal from the system by sediment N2-N flux. Results indicate that nutrient release from sediments generate internal nutrient loads proportional to external loading from the watershed. Our results highlight the significant potential for internal nutrient loading and benthic N2 fixation within sediments to regulate biogeochemical processes within understudied oxbow lake ecosystems.

Land subsidence (LS) is becoming one of the major problems in coastal and delta cities worldwide. Understanding the current LS situation and the research trends is of paramount importance for further studies and addressing future international research networks. We analyzed the LS-related literature available from the Scopus database. The use of a single database avoided the redundancy of articles, while excluding some subject areas was useful to obtain only studies related to LS. By using VOSviewer and CiteSpace tools, we conducted a bibliometric analysis by considering title, keywords, and abstract to identify the temporal development, the geographical origin, and the area of study of the research. The results revealed a considerable heterogeneity of approaches, thematics, study areas, and research output trends. China, the US, and Italy are the major contributors to the scientific production, but the higher number of articles is not always related to the extension of the LS phenomenon in these countries. The monitoring approach differs worldwide, and univocal modeling is still lacking; from the analysis of the keywords, it is clear that the focus of most studies is on the relationship with the hydrological/hydrogeological aspects. Since the 2000s, however, the development of SAR technologies has boosted the study of the phenomenon from a different point of view.

The present study assessed the human health risk exposure from the consumption of poor quality groundwater in the Lucknow area, a part of Central Ganga alluvial plain in India. Around 27 ( n  = 27) groundwater samples were collected from the study area. The analytical results of the samples ( n  = 27) collected indicate silicate and carbonate weathering is the dominant process along with cation exchange, sulfide oxidation, and reverse ion exchange. The type of groundwater is Ca 2 –Na–HCO 3 − type having all cations and anions within permissible WHO limits except for iron (Fe 2+ ) and nitrate (NO 3 − ). The high concentrations of Fe 2 and NO 3 − in samples indicate the possibility of a non-geogenic point source for the same in an urban-influenced environment. The ionic concentration of dissolved constituents is used in weighted overlay analysis to generate the water quality index (WQI). WQI indicates that most urban areas (~ 98.52%) have fallen in the good to excellent category except few situated in the highly populated parts of Lucknow. The ionic concentrations of Fe 2+ and NO 3 − have been further used to estimate human health risk by integrating regional urban population density data in Lucknow. The risk map shows alarming risks in the west-central part, where nearly ~ 35% of the total area is at moderate to high health risk.

Alluvial soils are rich in mineral nutrients, and contain high heavy metals, especially Cd. The interactions of mineral nutrients with Cd in soil-rice grain systems on natural condition of alluvial plain are highlighted in this study. 110 pairs of rice grain and soil (0–20 cm) samples from the Pearl River Delta were investigated and measured. The results indicated that pH, organic matter, cation exchange capacity, clay, Ca, Cd, Fe, Mn and Zn are the most important soil characteristics controlling Cd uptake by rice grain. There are synergetic interactions between Cd and mineral elements in the soils, and antagonistic interactions between them in the rice grains. It could provide useful information for the risk assessment of heavy metals in the soils of alluvial plain.

Ground deformation on a regional to local scale is the consequence of a wide range of natural processes such as tectonic and anthropogenic activities. Globally, the over-extraction of groundwater and hydrocarbon exploitation are the primary causes of ground subsidence. The current study demonstrates regional scale ground subsidence analysis of the Dibrugarh and Digboi regions of Brahmaputra alluvial plain, Assam, Northeast India. To understand the ongoing surface deformation satellite base, the RADAR technique has been applied using SENTINEL-1A data, which were acquired between 15 October 2015 to 25 January 2022. The assessment carried out via the time series analysis of the radar data suggests that the Dibrugarh area is subsiding at a rate of ~5 mm/yr, whereas the Digboi is deforming at a much faster rate (±22 mm/yr) than Dibrugarh. The presence of active faults in the subsurface and associated deformation is another reason for active ground subsidence. The outcomes of the current study validate that the study area is currently undergoing active subsurface deformation caused by both endogenic as well as exogenic processes. Furthermore, our Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) and satellite-based analysis suggest that the over-exploitation of the natural resources is enhancing the rate of deformation in the Brahmaputra alluvial plain in the northeast of India.

Understanding dynamic groundwater–surface water interactions in alluvial plains is critical for sustainable water resource management, yet seasonal variability and spatial heterogeneity of these exchanges remain imprecisely quantified. Here, we present an improved [sup.222]Rn mass balance model for evaluating the seasonal hydraulic exchange between groundwater and the Xintongyang Canal in the Taizhou alluvial plain over the course of a hydrologic year. To reduce the model uncertainty, the “background” [sup.222]Rn for non-groundwater sources was incorporated into the model to replace the influence of hyporheic exchange. The results indicate that the hydraulic exchange process of surface water and groundwater has significant spatiotemporal differences. Based on the calculations from the [sup.222]Rn mass balance model, the canal leakage flux follows the order of summer > autumn > winter > spring over the course of a hydrologic year. In contrast, the groundwater discharge flux follows the order of summer > spring > autumn > winter. During a hydrological year, summer demonstrated the most intense water exchange dynamics, with peak fluxes reaching 0.0455 m[sup.3]/(s·m) for surface water leakage and 0.0013 m[sup.3]/(s·m) for groundwater discharge, revealing pronounced spatial heterogeneity in dominant exchange processes. [sup.222]Rn activity in canal and groundwater varies significantly across different regions, with canal leakage being the dominant mode of hydraulic exchange within the study area. The change of the hydraulic exchange process was mainly affected by factors such as rainfall. In the process of promoting surface water leakage, precipitation will also strengthen the supplement of groundwater and contribute to the groundwater discharge in most of the canal sections. This study offers insight into the seasonal variations of groundwater and surface water interaction within an alluvial plain.

In Tunisia, the discharge of treated wastewater onto land area has become a common practice, especially in arid and semi-arid regions where there are no permanent rivers to receive discharge. Treated wastewater constitutes a potential anthropogenic source of aquifer recharge as is the case for the alluvial aquifer downstream of the Kairouan plain. This alluvial aquifer receives annually an average volume of 4.9 hm3 of treated wastewater from the Dhraa Tammar wastewater treatment plant, which is discharged over a land area of 182 ha. This research presents the first piezometric and hydrogeochemical characterization of Kairouan plain shallow groundwater and the assessment of treated wastewater impacts on groundwater piezometric levels, salinity and hydrogeochemical composition and microbiological contents of groundwater. To achieve these objectives, a piezometric surveys of 15 shallow wells was undertaken. Additionally, groundwater and treated wastewater samples were collected in February and April 2017 for chemical and microbiological analysis. The piezometric study shows that treated wastewater discharge induces a local increase of the water table level materialized by the appearance of a piezometric dome (a height estimated at 1.5 m) in the discharge site during a period of 4 years (2014–2017). Shallow groundwater downstream of Kairouan plain shows a naturally high mineralization state (a salinity more than 20 g L−1) caused by natural mineralization process. A considerable reduction of groundwater salinity (between 3 and 10 g L−1) is observed in the discharge site due to treated wastewater infiltration. Discharge of treated wastewater has caused an increase of groundwater bicarbonate concentration due to leaching of organic matter and local microbiological groundwater contamination (250–450 fecal germs per 100 ml) in the discharge site.

Groundwater is a vital resource in the Chuoshui River alluvial plain (CSAP), a key agricultural area in Taiwan. Understanding groundwater recharge is crucial for sustainable water management amidst changing climatic conditions and increasing water demand. This study investigates the major ion composition, solute Sr concentrations, and 87Sr/86Sr ratios in groundwater and stream water from the Choushui River (CSR) to trace groundwater recharge sources. The Piper diagram reveals that most groundwater samples are of the freshwater Ca–HCO3 type, aligning with the total dissolved solids (TDS) classification. TDS and major ion compositions indicate that groundwater near Baguashan Terrace (BGT) and Douliu Hill (DLH) primarily derives from stream water and rainwater. Na+ and Cl− enrichment in some aquifers of BGT and DLH is attributed to the dissolution of paleo-sea salt and mixing with paleo-seawater from sedimentary porewater. Elevated dissolved Sr concentrations and lower 87Sr/86Sr ratios in these aquifers further support the intrusion of paleo-seawater. Groundwater in the proximal fan shows high TDS due to intensive weathering, complicating the use of TDS as a tracer. Sr isotopic compositions and solute Sr2+ concentrations effectively distinguish recharge sources, revealing that the CSR mainstream primarily recharges the proximal fan and BGT region, while CSR tributaries and rainwater mainly recharge the DLH region. This study concludes that Sr isotopic compositions and solute Sr2+ concentrations are more reliable than TDS and major ion compositions in identifying groundwater recharge sources, enhancing our understanding of groundwater origins and the processes affecting water quality.

Human health is “at risk” from exposure to sub-lethal elemental occurrences at a local and or regional scale. This is of global concern as good-quality drinking water is a basic need for our wellbeing. In the present study, the “probability kriging,” a geostatistical method that has been used to predict the risk magnitude of the areas where the probability of dissolved mercury concentration ( d Hg) is higher than the World Health Organization (WHO) permissible limit. The method was applied to geochemical data of d Hg concentration in 100 drinking groundwater samples of Lucknow monitoring area (1222 km 2) located within the Ganga Alluvial Plain, India. Threefold (high to extreme risk) and twofold (moderate risk) higher d Hg concentration values than the WHO permissible limit were observed in all of the groundwater samples. The generated prediction map using the probability kriging method shows that the probability of exceedance of d Hg is the highest in the northwestern part of the Lucknow monitoring area due to anthropogenic interferences. The hotspots with high to very high probability are potentially alarming in the urban sector where 32.4% of the total population is residing in 6.8% of the total area. Interpolation of local estimates results in an easily readable and communicable human health risk map. It may help to consider substantial remediation measures for managing drinking water resources of the Ganga Alluvial Plain, which is among the anthropogenic mercury emission–dominated regions of the world.

Qin, W.J. and Fan, G.S., 2020. Estimating soil water characteristic curve from soil physical-chemical properties in alluvial plain. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 421-424. Coconut Creek (Florida), ISSN 0749-0208. The soil water characteristic curve is an important equation of soil hydraulics, which plays a decisive role in the storage and transport of soil water, and has potential influences of hydrological and ecological processes in whole ecosystems. In order to understand the controlling factors affect Van Genuchten model parameters in Alluvial Plain, ninety undisturbed soil samples were collected from Chanyuan River and Xishan Lake. The direct determination of the soil water characteristic curve has the defects of time-consuming and high cost, the BP based on genetic algorithm optimization model was proposed to obtain the Van Genuchten model parameters from easily-obtained soil physical-chemical properties. The research results provide a basis for the further study of soil water holding capacity of undisturbed soil, and also provide a more accurate method for obtaining soil water characteristic curve in Alluvial Plain.