Effects Of Seawater Intrusion Research Articles

Seawater intrusion effects on nitrogen cycling in the regulated Nakdong River Estuary, South Korea

Seawater intrusion effects on nitrogen cycling in the regulated Nakdong River Estuary, South Korea

Analysis on the spatiotemporal evolutions of groundwater hydrochemistry and water quality caused by over-extraction and seawater intrusion in eastern coastal China

The over-extraction of groundwater has resulted in seawater intrusion and the southward migration of the saltwater interface, gradually deteriorating the groundwater quality in the Weibei Plain. In this research, groundwater samples were gathered from 46 monitoring wells for shallow groundwater during the years 2006, 2011, 2016, and 2021. The hydrochemical features of regional groundwater and the factors influencing the issue were subjected to statistical analysis. Additionally, the assessment of spatiotemporal variations in groundwater quality was conducted using the customized entropy-weighted water quality index (EWQI) method. The relationship between groundwater over-extraction and the southward intrusion of the saltwater interface was compared and analyzed. The results of this paper revealed that the Weibei Plain has been in a state of long-term over-extraction of groundwater from 2000 to 2021, with an average annual over-extraction of 118.49 million m3. The groundwater depression cone areas in the northern part of the study area increased from 3,247.37 to 4,581.34 km2 from 2006 to 2021, with the center of the cone experiencing a drop in groundwater level from −22 to −85 m. The saltwater interface shifted southward by 711.71 km2 from 2006 to 2021. In groundwater, the high concentrations of TH, TDS, and Cl− were primarily related to the seawater intrusion, while higher concentrations of NO3− were mainly determined by frequent agricultural production, industrial wastewater, and domestic sewage discharges. The groundwater hydrochemical types in the study area transitioned from predominantly HCO3·Ca-Mg type in 2006 to HCO3-Na type and SO4·Cl-Ca·Mg type in 2021 due to seawater intrusion. The results of PCA and HCA show the effects of seawater intrusion, human activities, and rock weathering on groundwater hydrochemistry. The evaluation results based on the EWQI revealed that the average value of the samples in 2021 was 101.36, which belonged to Class IV water quality standards, representing the poorest water quality among the 4 years. The southward migration of the saltwater interface led to the deterioration of groundwater quality in the groundwater depression cone areas, which gradually worsened from 2006 to 2021. The maximum increase in EWQI value was 174.68 during the period, shifting from Class III water quality to Class V water quality. Groundwater quality remained relatively better in the western and southern regions which were less affected or unaffected by seawater intrusion. The results of the study can provide a certain reference value for the sustainable management of groundwater resources and the management of groundwater pollution and seawater intrusion in the Weifang City area in the future.

Comparative study for coastal aquifer vulnerability assessment using deep learning and metaheuristic algorithms.

Coastal aquifer vulnerability assessment (CAVA) studies are essential for mitigating the effects of seawater intrusion (SWI) worldwide. In this research, the vulnerability of the coastal aquifer in the Lahijan region of northwest Iran was investigated. A vulnerability map (VM) was created applying hydrogeological parameters derived from the original GALDIT model (OGM). The significance of OGM parameters was assessed using the mean decrease accuracy (MDA)method, with the current state of SWI emerging as the most crucial factor for evaluating vulnerability. To optimize GALDIT weights, we introduced the biogeography-based optimization (BBO) and gray wolf optimization (GWO) techniques to obtain to hybrid OGM-BBO and OGM-GWO models, respectively. Despite considerable research focused on enhancing CAVA models, efforts to modify the weights and rates of OGM parameters by incorporating deep learning algorithms remain scarce. Hence, a convolutional neural network (CNN) algorithm was applied to produce the VM. The area under the receiver-operating characteristic curves for OGM-BBO, OGM-GWO, and VMCNN were 0.794, 0.835, and 0.982, respectively. According to the CNN-based VM, 41% of the aquifer displayed very high and high vulnerability to SWI, concentrated primarily along the coastline. Additionally, 32% of the aquifer exhibited very low and low vulnerability to SWI, predominantly in the southern and southwestern regions. The proposed model can be extended to evaluate the vulnerability of various coastal aquifers to SWI, thereby assisting land use planers and policymakers in identifying at-risk areas. Moreover, deep-learning-based approaches can help clarify the associations between aquifer vulnerability and contamination resulting from SWI.

Modeling of seawater intrusion into Salalah coastal plain aquifer, sultanate of Oman

Excessive groundwater pumping has become a concern in Salalah coastal aquifer in Oman causing seawater intrusion at different farms and abstraction wells near the shoreline. MODFLOW and MT3DMS were calibrated and validated for Salalah coastal aquifer to assess aquifer behavior and seawater intrusion pattern with new input data and fine grid spacing to improve the accuracy of predictions as compared to the previous modeling studies in this region. The study was conducted over an area of 640 km2 of Salalah Plain representing around 83% of its total area. Injection of tertiary treated wastewater, rainfall and dams were considered as sources of aquifer recharge while groundwater abstraction occurred for agricultural, domestic, and commercial uses. The calibration and validation of the models were done in steady and transient states using observed groundwater levels from year 2000–2019. The aquifer properties such as hydraulic conductivity, specific yield, and vertical anisotropy were calibrated. MODFLOW results were utilized by MT3DMS to simulate solute transport at transient state. The longitudinal dispersivity and porosity of the aquifer were obtained by calibration and validation of the model. Over the three aquifer layers, the hydraulic conductivity ranges from 10 m/day to 100 m/day, vertical anisotropy is 4 and the specific yield ranges from 0.01 to 0.1. The calibrated values of the longitudinal dispersivity and porosity range from 500 m to 50000 m, and 0.4, respectively. The study indicated a clear impact of seawater intrusion at coastal side of the Salalah plain. The predictive modeling indicated an average of 1.5 m drop in hydraulic head across the whole study area by 2040, while seawater intrusion effect was expected to increase near the coast with potential extension to the central area of the Salalah plain. The validated model can be used as a prediction tool by the decision makers to manage the aquifer considering different scenarios, for integrated water resources management in Salalah city.

Hydrochemical characterizations and groundwater quality assessment in the coastal region of the Jiaodong peninsula, North China

Groundwater resources constitute a primary water source in the coastal region of Jiaodong Peninsula (CRJP), serving as an essential foundation for socio-economic development and municipal water supply. This study sought to evaluate the hydrogeochemical properties of the CRJP's groundwater using 73 samples collected in 2017, comprehensively analyzing the chemical composition and environmental factors using mathematical statistics and hydrochemical techniques. The results demonstrate that groundwater in the CRJP possesses TDS values ranging from 262 to 28,160 mg/L, with a pH ranging between 6.4 and 8.5, characterizing a weakly alkaline water system. The cation order in groundwater is Na+ > Ca2+ > Mg2+ > K+, while the anionic sequence comprises Cl− > HCO3− > SO42− > NO3−. According to the Piper diagram, groundwater samples predominantly clustered into SO4·Cl-Ca·Mg and SO4·Cl-Na types. Additionally, significant spatial variations exist in the primary chemical components of groundwater. Hydrogeochemical characteristics within the region are influenced both by natural and human activities; natural elements include weathering of silicate rocks, gypsum and carbonate minerals dissolution, while human practices comprise industrial and mining activities, agricultural practices, and domestic waste discharge. The results from a health risk assessment show that non-carcinogenic risks posed by nitrate intake via drinking water are considerably high for infants in comparison to adults, teenagers, and children. Furthermore, certain regions within the CRJP show notable seawater intrusion effects on groundwater studied.

Design of an Exploratory Experiment in Teaching for Engineering Education Accreditation: Fluoride Geochemical Simulation during Water–Rock Interactions under the Effect of Seawater Intrusion

Engineering education is critical for the creation of a more sustainable world, and engineering education accreditation has become the current trend for reform in higher education worldwide. Traditional replication experiment-based teaching cannot meet the standards of engineering education accreditation, and integrating the ideas of engineering education accreditation into experimental teaching is an important aspect of practical teaching. Taking fluoride evolution simulation during water–rock interactions under the effect of seawater intrusion as an example, an exploratory experiment was designed with the idea of engineering education accreditation. The experiment concluded that leached fluoride increases with increasing ratios of seawater and brine water, NaCl levels, and NaHCO3 levels, but with decreasing CaCl2 levels, which confirms that seawater intrusion deeply affects fluoride evolution. The saturation index and Fourier Transform Infrared analyses indicate that Ca2+ restriction and exchange of F with O–H and Si–O–Si are responsible for fluoride leaching. The experiment was characterized by deeper theory, logicality, and openness, and was also multi-schematic and exploratory. Therefore, it is an ideal subject matter to develop an exploratory experiment. A reasonable teaching link was designed to integrate the ideas of engineering education accreditation. Students were required to creatively and personally devise an experimental design and an expansion to the experiment based on the given databases and other relevant literature and to cooperate and discuss in groups. The experiment not only integrates basic knowledge of water–rock interactions, but also cultivates the awareness of and ability to analyze and solve problems, innovative thinking, scientific literacy, and teamwork. Meanwhile, the experiment effectively supports the graduate requirements of various subjects, including Design/Development Solutions, Research, Applying Modern Tools, Individual and Teams, and Communication.

Using Statistical Analysis to Assess Shallow Groundwater Quality in Squatter Settlement of Dar es Salaam and Pwani Regions in Tanzania

In Dar es Salaam and the Coastal regions, groundwater is the primary source of freshwater. Urbanization, industrialization, and agricultural activities have all contributed to the overuse of this resource, resulting in a decline in quality. In this study, we employ statistical analysis as a means to improve our understanding on groundwater quality. Seventy-one groundwater samples in squatter areas of Dar es Salaam and Coastal regions were used with 10 chemical parameters. Based on their dominant chemical compositions, hierarchical cluster analysis (HCA) classified samples into three main clusters. The clusters were then characterized with the help of the results from principal component analysis (PCA), Pearson's correlation coefficient of the chemical variables and piper diagrams. Cluster one was characterized by high salinity as a result of seawater intrusion. Cluster two was characterized by an intermediate salinity and high contamination. This was a result of sewage contamination and a moderate effect of seawater intrusion. With a low level of salinity and contamination, cluster three was found to be suitable for human consumption. The information obtained from this study demonstrates that the quality of the water has declined in some areas within the chosen regions. Therefore, prompt action is required to prevent further deterioration to the aquifers in the region.

Effect of seawater intrusion on water quality of coastal aquifer of Bagerhat district, Bangladesh

Effect of seawater intrusion on water quality of coastal aquifer of Bagerhat district, Bangladesh

Identification of Seawater Intrusion in the Dibdibba Coastal Aquifer, South of Iraq Using Chemical Indicators and Multivariate Analyses

Seawater intrusion into the groundwater is a major environmental disaster which affects the environment as well as community. This research aims to analyze the seawater intrusion in the Dibdibba coastal aquifer. In this study, researchers used statistical techniques to examine the impact of seawater intrusion in the Dibddiba coastal aquifer in southern Iraq. They collected 15 groundwater samples from pumping wells during wet and dry periods and analyzed those using multivariate statistical analyses and ionic ratios based on the GIS technique. The results showed that there was a strong linear correlation between total dissolved solids (TDS) and several other ions, including Ca2+, Mg2+, Na+, Cl− SO−2 4, and NO−3. The principle component analysis revealed two factor loadings, with the first accounting for a significant portion of the total variance and showing a high loading for TDS, Na+, Cl−, SO−2 4, Mg2+, Ca2+, and NO−3. The second factor had a high loading for K+. The seawater influence was detected in 33.33 percent of the low zone groundwater, 26.66 percent of the moderate zone groundwater, and 40 percent of the high zone groundwater that was studied. Eighty and sixty-seven percent of the groundwater samples, respectively, belonged to the seawater field as Na-Cl type, as shown by Chadha’s graphic, demonstrating the effect of seawater intrusion. Also, during the wet time, 20% of the samples belonged to the reverse ion exchange water field as Ca-Mg-Cl type, but during the dry period, 33.3% did. This is further evidence of the impact of seawater intrusion.

Geochemistry and assessment of groundwater resource in coastal arid region aquifer (Dahab delta, South Sinai, Egypt)

Dahab is a tourist city located in the Sinai Peninsula, downstream of the Dahab watershed, as a part of the arid coastal region. Groundwater samples have been collected from the Dahab delta and were tested for salinity, major ions, minor elements, and heavy metals to investigate the geochemical processes deteriorating the groundwater quality. The spatial distribution of major, minor, and trace elements integrated with the geochemical interrelationships using the cumulative salinity bases mixing curves have been utilized to investigate the main source(s) of groundwater recharge and salinization origin in Dahab delta aquifer. The groundwater salinity ranges from 339 upstream of Dahab watershed to 53,216 mg/L downstream in the delta area. The groundwater varies from fresh, brackish, and saline water. The spatial distributions of major ions, minor elements (Si, and Br), and heavy metals (B and Sr) confirm that the recharge comes from the upstream watershed. According to the mixing model curves, groundwater quality has declined due to interactions with the aquifer matrix, mixing with seawater, and rejected brine from the reverse osmosis desalination plants. The fresh/brackish groundwater classes have been recorded in the northwestern part of the study area close to the basement rocks, where the Quaternary aquifer receives considerable recharge through the underneath fractures, joints, and faults that enhance the subsurface recharge. The samples with a high saline groundwater class have been recorded in the eastern and southern parts of the delta, demonstrating the effects of seawater intrusion. Based on WHO guideline criteria, the assessment of groundwater for various uses has determined that most groundwater samples from the alluvial aquifer (91%) are unfit for human consumption. The Water Quality Index indicates that the groundwater in the southern part of the delta is not suitable for all uses due to mixing with the seawater, and injection of rejected brine water from the desalination plants. In the north, groundwater is unfit for drinking and aquatics, excellent for recreation, marginal for irrigation, and fair for livestock. The groundwater in coastal arid region aquifers has deteriorated due to seawater intrusion.

Effects of Seawater Intrusion on the Groundwater Quality of Multi-Layered Aquifers in Eastern Saudi Arabia

The degradation of groundwater (GW) quality due to seawater intrusion (SWI) is a major water security issue in water-scarce regions. This study aims to delineate the impact of SWI on the GW quality of a multilayered aquifer system in the eastern coastal region of Saudi Arabia. The physical and chemical properties of the GW were determined via field investigations and laboratory analyses. Irrigation indices (electrical conductivity (EC), potential salinity (PS), sodium adsorption ratio (SAR), Na%, Kelly's ratio (KR), magnesium adsorption ratio (MAR), and permeability index (PI)) and a SWI index (fsea) were obtained to assess the suitability of GW for irrigation. K-mean clustering, correlation analysis, and principal component analysis (PCA) were used to determine the relationship between irrigation hazard indices and the degree of SWI. The tested GW samples were grouped into four clusters (C1, C2, C3, and C4), with average SWI degrees of 15%, 8%, 5%, and 2%, respectively. The results showed that the tested GW was unsuitable for irrigation due to salinity hazards. However, a noticeable increase in sodium and magnesium hazards was also observed. Moreover, increasing the degree of SWI (fsea) was associated with increasing salinity, sodium, and magnesium, with higher values observed in the GW samples in cluster C1, followed by clusters C2, C3, and C4. The correlation analysis and PCA results illustrated that the irrigation indices, including EC, PS, SAR, and MAR, were grouped with the SWI index (fsea), indicating the possibility of using them as primary irrigation indices to reflect the impact of SWI on GW quality in coastal regions. The results of this study will help guide decision-makers toward proper management practices for SWI mitigation and enhancing GW quality for irrigation.

A Case Study of the Effect of Seawater Intrusion on the Water Quality Index of the Indian Southeastern Coastal Region

Safe and clean acceptable quality of water is essential for the survival of life. There are severe problems with the insufficient availability of safe groundwater for human consumption. The present study aims to evaluate the groundwater quality in the coastal area of Srikakulam district, located in the extreme northeastern direction of Andhra Pradesh in India. The study area spreads over an area of 130 km2. In this study, groundwater is the major source for drinking and irrigation purposes. A total of 20 bore well (BW) groundwater samples were collected with a distance of 5 km each during the period of the premonsoon and monsoon seasons of 2020. This study investigates the importance of groundwater quality in some areas of the coastal villages in the Srikakulam district. The overall water quality condition is explained with various physicochemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), total alkalinity (TA), calcium (Ca2+), magnesium (Mg2+), fluoride (F–), chloride (Cl–), nitrate (NO3–), sulfate (SO42–), sodium (Na+), potassium (K+), and turbidity. The water quality is assessed on the basis of the water quality index (WQI) method. The physicochemical results are compared to the water quality standards of the World Health Organization (WHO), 2012, and the Bureau of Indian Standards (BIS), 2012. The correlations between the values have been presented for various parameters. The water quality index (WQI) ranged between 11.56 and 61.27, the highest value recorded at M. Ganguwada and the lowest at Bandaravanipeta. The analytical results showed that around 90% of the samples are extremely hard in their nature and that their Na+ and Cl– concentrations are also higher. It indicates that the coastal region is influenced by seawater intrusion.

HYDRO-GEOCHEMICAL EVALUATION AND APPLICATION OF WATER QUALITY INDEX (WQI) OF GROUNDWATER ON EAST COAST STRETCH OF TAMIL NADU, INDIA

The geochemical characteristics of 33 groundwater samples collected in and around the Kalpakkam area in 2019 were investigated, as well as the effects of seawater intrusion. The dominance of anions and cations is Cl- > HCO3- > NO3- > SO4 and Na+ > Mg >Ca> K. Electrical conductance has exceeded the allowable limit in the northeastern part of the study area, which could be accredited to the proximity of a backwater. The Cl (strong acid) predominates over HCO3 and SO4 (weak acids) in the groundwater of the study region during both seasons of 2019, 90.9 percent and 100%, respectively, based on the hydro-chemical features. The Water Quality Index was determined, and many of the 33 samples fell into the bad category, followed by the nice. The majority of anions and cations show a positive correlation (correlation matrix) with Cl-, especially Na and Mg, suggesting these ions may have been derived from seawater intrusion, secondary salt leaching, and chemical weathering, indicating both natural and anthropogenic origins. The interaction of the ions representing Mg, Ca, Na, and Cl in factors suggests secondary salt leaching or backwater recharge. The study's theme is to examine groundwater's geochemical signatures through geochemical analysis. Using statistical approaches, assess the impact of various pollution sources. The water quality index (WQI) is used to classify the quality of groundwater.

Effect of Seawater Intrusion on the Formation of Chlorinated and Brominated Trihalomethanes in Coastal Groundwater

Around the world, coastal groundwater is increasingly subject to seawater intrusion (SWI). The quality and characteristics of such waters differ from those of surface and groundwater. In the current study, trihalomethane (THM) formation under varying levels of SWI, natural organic matter (NOM), and chloride-to-bromide (Cl/Br) ratio was evaluated. Different levels of SWI were simulated by mixing deionized water with real seawater (RSW) collected from the Indian Ocean or synthetic seawater (SSW) by varying seawater volumes from 0% to 3%. Humic acid (0 to 5 mg/L) was added to represent NOM at concentrations mimicking natural levels of dissolved organic carbon. The chlorine demand of the simulated water samples was significantly correlated to SWI levels and NOM concentrations. THM concentration in SSW increased from 12.64 µg/L to 105.34 µg/L after 24 h and to 115.8 µg/L after 48 h for an increase from 0% to 3% volume of seawater. For water samples simulated with RSW, maximum THMs after 24 h were 119.2 µg/L, and after 48 h were 126.4 µg/L. An increase in NOM concentration in seawater-intruded water samples resulted in increasing THMs, especially tribromomethane. However, the increment in THMs at higher NOM concentration was lower compared to that at low NOM concentration. Chlorine demand was positively correlated only to tribromomethane. An increase in bromide concentration resulted in lower Cl/Br ratio and a concomitant increase in brominated THMs. The bromine substitution factor corresponding to increasing SWI of 0.25–3% decreased from 2.67 to 1.81 over a reaction time of 24 to 48 h, indicating a shift from TBM dominance to chlorinated THMs.

Usage of Coal Fly Ash and Bottom Ash from Ash Ponds for Bricks and Precast Concrete Blocks – A Review

As larger amounts of coal are burned every day to produce electricity for a growing population, more coal ash is produced and stockpiled in large landfills and ash ponds. The ever-increasing stockpiles of unutilized Coal Fly Ash (CFA) and Bottom Ash (CBA) are a growing health and environmental concern. Studies have shown that communities living near ash ponds are subjected to an increased risk of respiratory illness, and the stockpiles can also potentially cause environmental pollution due to leachate. The potential utilization of CFA and CBA is to use them as natural aggregate substitutes for construction materials such as mortar, bricks and precast concrete. This paper aims to review recent studies on the usage of CFA and CBA in producing brick and precast concrete blocks, the changes in the properties of the CFA or CBA bricks and precast concrete blocks compared to control samples, as well as the effects of seawater intrusion into the concrete mix, which indicate the potential effects of using CFA and CBA stored in coastal ash ponds.

Combined effects of seawater intrusion and nitrate contamination on groundwater in coastal agricultural areas: A case from the Plain of the El-Nil River (North-Eastern Algeria)

This study focuses on coastal aquifers subject to uncontrolled land use development by investigating the combined effects of seawater intrusion and nitrate contamination. The research is undertaken in a Mediterranean coastal agricultural area (Plain of the El-Nil River, Algeria), where water resources are heavily impacted by anthropogenic activities. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, δ15NNO3 and δ18ONO3), is combined with a hydrochemical facies evolution diagram, and a Bayesian isotope mixing model (MixSIAR) to assess seawater contamination with its inland intrusion, and distinguish the nitrate sources and their apportionment. Results show that seawater intrusion is circumscribed to the sector neighboring the Mediterranean Sea, with two influencing functions including classic inland intrusion through the aquifer, and upstream seawater impact through the river mouth connected to the Mediterranean Sea. Groundwater and surface water samples reveal nitrate concentrations above the natural baseline threshold, suggesting anthropogenic influence. Results from nitrate isotopic composition, NO3 and Cl concentrations, and the MixSIAR model show that nitrate concentrations chiefly originate from sewage and manure sources. Nitrate derived from the sewage is related to wastewater discharge, whereas nitrate derived from the manure is attributed to an excessive use of animal manure to fertilise agricultural areas. The dual negative impact of seawater intrusion and nitrate contamination degrades water quality over a large proportion of the study area. The outcomes of this study are expected to contribute to effective and sustainable water resources management in the Mediterranean coastal area. Furthermore, this study may improve scientists' ability to predict the combined effect of various anthropogenic stressors on coastal environments and help decision-makers elsewhere to prepare suitable environmental strategies for other regions currently undergoing an early stage of water resources deterioration.

Analysis of seawater intrusion into groundwater in the coastal area of Durung Village, Aceh Besar Regency, Aceh Province, Indonesia

Durung Village is a region consisting mostly of coastal and hilly areas. Utilization of groundwater in the coastal zone has been increased these recent years for all purposes of life, from drinking to sanitation and from industry to agriculture. It results new environmental problem, such as seawater intrusion that caused negative impact on groundwater resources. This research aims to analyze the effect of seawater intrusion into the groundwater in the study area. Total Dissolved Solids (TDS) was used in this research as approximation of groundwater salinity value. The spatial distribution of seawater intrusion had been prepared by using Geographic Information System (GIS) spatial interpolation technique for TDS parameter. The results revealed that seawater intrusion presented more obviously near the coastal line and its northern part was the most affected area by this contamination indicated by the highest TDS value of 2.947 mg l-1, whereas the farther location from the coastline were free of seawater intrusion indicated by low TDS values between 181 – 579 mg l-1.

Corrosion - Scaling Potentially of Domestic Water Pipelines and Evaluate the Applicability of Raw Water Sources in Basrah, IRAQ

As a result of changes in the chemical properties of the Shatt al-Arab River, especially in the last decade, as well as the lack of rainfall and the effect of seawater intrusion into the Shatt al-Arab, this study was conducted to investigate the possible changes in the water pipelines like corrosive and scaling which Shatt al-Arab River is the source of water supply for domestic use. Domestic water samples were collected from 10 various locations in Basrah to study the water's tendency to be corrosive or form scales along the pipelines. The Langelier Index, Ryznar Index, Larson-Skold Index, and Saturation Index were used to determine the corrosivity potential of water based on physical and chemical parameters. Most domestic water sources tend to form scales based on the Langelier Saturation Index, Ryznar Index, and Saturation Index. According to the evaluation, the Langelier Index ranged from -1.71 to 1.98, Ryznar Index was between 4.45 and 10.53, Larson-Skold Index was between 1.13(rainwater) 62.70 (Dibdabba Water) and Saturation Index was ranged -1.31 to 1.24. The results indicated that the rainwater and some groundwater samples are moderately corrosive. The water of all the water resources sampled in this study ranged from balanced to mild scaling. The Larson-Skold Index, on the other hand, shows that all domestic water samples are corrosive. The corrosion and scaling potential of natural water sources collected from groundwater, river water, and rainwater has also been determined.

Soil Salinity Estimation Over Coastal Wetlands Based on Random Forest Algorithm and Hydrological Connectivity Metric

Owing to climate warming and human activities (irrigation and reservoirs), sea level rise and runoff reduction have been threatening the coastal ecosystem by increasing the soil salinity. However, short-term sparse in situ observations limit the study on the response of coastal soil salinity to external stressors and thus its effect on coastal ecosystem. In this study, based on hydrological connectivity metric and random forest algorithm (RF), we develop a coastal soil salinity inversion model with in situ observations and satellite-based datasets. Using Landsat images and ancillary as input variables, we produce a 30-m monthly grid dataset of surface soil salinity over the Yellow River Delta. Based on the cross-validation result with in situ observations, the proposed RF model performs higher accuracy and stability with determination coefficient of 0.89, root mean square error of 1.48 g·kg-1, and mean absolute error of 1.05 g·kg-1. The proposed RF model can gain the accuracy improvements of about 11–43% over previous models at different conditions. The spatial distribution and seasonal variabilities of soil salinity is sensitive to the changing signals of runoff, tide, and local precipitation. Combining spatiotemporal collaborative information with the hydrological connectivity metric, we found that the proposed RF model can accurately estimate surface soil salinity, especially in natural reserved regions. The modeling results of surface soil salinity can be significant for exploring the effect of seawater intrusion and runoff reduction to the evolution of coastal salt marsh ecosystems.

Effects of seawater intrusion on the formation of disinfection byproducts in drinking water

Seawater contains high levels of halides, which can increase the concentrations of bromide and iodide ions in coastal groundwater and surface water sources. Intrusion of seawater alters the chemistry of fresh water leading to the formation of additional brominated and iodinated disinfection byproducts (DBPs), many of which are cyto- and genotoxic to the mammalian cells, and have cancer risks to humans. In this study, effects of seawater intrusion on the formation of trihalomethanes (THMs), and haloacetic acids (HAAs) were investigated by spiking groundwater using 0.0–2.0% seawater (by volume) and liquid chlorine as disinfectant. The concentrations of bromide and iodide ions in groundwater (0.0% seawater) were 42.5 and non-detected (ND) μg/L respectively, which were increased up to 1100 and 2.1 μg/L respectively, following mixing with 2.0% seawater. The regulated THMs (THM4) were increased from 30.4 to 106.3 μg/L while iodinated THMs (I-THMs) were increased from 0.13 to 1.6 μg/L respectively due possibly to molecular substitution and additional pathways of THMs formation. Bromoform was increased from 0.5 to 94.3 μg/L while iodoform was increased from ND to 1.02 μg/L. HAAs were increased from 27.9 to 72.9 μg/L where tribromoacetic acid was increased from 2.0 to 43.7 μg/L. In 0.0% seawater, bromine incorporation factor (BIF) for THM4 and HAAs were 0.077 and 0.050 respectively, which were increased to 0.942 and 0.38 at 2% seawater respectively. For dihalogenated HAAs (X2AA) and trihalogenated HAAs (X3AA), BIF in 0.0% seawater were 0.098 and 0.14 respectively, which were increased to 0.863 and 0.924 for 2.0% seawater respectively. Mixing of 2.0 seawater increased the toxicity of THM4, HAAs and I-THMs by 4.2, 5.9 and 201.8 folds, respectively indicating the importance of reducing seawater intrusion into the freshwater sources. Further, alteration of water sources and/or adaptation of advanced treatment can assist in lowering the risks.