Effects Of Seawater Intrusion Research Articles

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.

Salinity Affects Freshwater Invertebrate Traits and Litter Decomposition

We evaluated the effect of seawater intrusion in coastal ecosystems on the freshwater invertebrate community and on leaf litter decomposition under realistic scenarios in six outdoor freshwater mesocosms containing fauna and flora, to which increasing volumes of seawater were added. The resulting salinity values were 0.28 (control, freshwater only), 2.0, 3.3, 5.5, 9.3, and 15.3 mS cm−1. The effect of salinity was assessed for 65 days after seawater intrusion, by computing the deviation of values in each treatment in relation to the control. Our results show that seawater intrusion into freshwaters will affect the invertebrate communities and organic matter decomposition, with salinities of up to 3.3–5.5 mS cm−1 having opposite effects to salinities of more than 9.3 mS cm−1. There was a net negative effect of the two highest salinities on mass loss and richness of the invertebrates associated with the decomposing leaves. Regarding the invertebrate communities of the mesocosms, there was a net negative effect of the intermediate salinity levels on abundance and richness. Invertebrate life cycle traits conferring resilience and resistance tended to increase with low and decrease with high salinity values, while avoidance traits showed an opposite trend, and these responses were more pronounced on the later stage community. These wave-like responses of the invertebrate species traits to increasing salinity suggest that the life-history and physiological adaptations most suitable to cope with osmotic stress will differ between low and high salinity levels.

Effect of seawater intrusion on groundwater in the Demak coastal area Indonesia: a review

One of the most complicated areas to repair on the North Shore of Central Java is the beach in the Sayung Demak. More than 300 hectares of land have been flooding in the last five years due to high tides. The erosion area in Sayung area has also been affected by port development activities in the Semarang area, thus changing the hydrodynamic nature of Sayung Demak Waters. Overuse of groundwater has been showing to lead to brine ingress in the coastal region. And long-term groundwater withdrawal forces land subsidence formation. A few waterfront structures in Sayung waters were built as breakwaters to decrease incoming waves. The solution presently used to minimize erosion while catching sediment in the Sayung area is hybrid engineering. The purpose of this study is to review the effectiveness of hybrid engineering in the coastal area of Demak and its relation to seawater intrusion and groundwater based on previous research. Understanding the factors that influence water quality in the source area over time is needed to establish appropriate management plans for the protection of groundwater resources and to ensure the safety and health of the beverage.

Coupled effect of seawater intrusion on groundwater quality: study of South-West zone of Surat city

Abstract Groundwater quality is a major problem for humanity since it is closely related to human health. The flow of seawater into freshwater aquifers is known as saltwater intrusion, and it can lead to groundwater quality contamination, including drinking water. Due to the extremely severe hydraulic interface between groundwater and seawater, saltwater intrusion can happen naturally in coastal aquifers. The aim of the study is to examine the status of seawater intrusion within the study region of the South-West zone of Surat city, Gujarat. The present study evaluates Groundwater Quality Index using a weighted arithmetic method including various chemical ions. The South-West zone of Surat city is located along the coast; seawater infiltration has a significant impact on the groundwater in the state. The conceptual model will be developed and analyzed using MODFLOW to analyze the effects of seawater intrusion analysis. The model domain is characterized by three hydro-stratographic layers and covers an area of approximately 110 km2 in a 400 m × 400 m grid size. An analytical study with MODFLOW would be carried out for three-dimensional groundwater flows with species of solute transport. This study would help profile the study area regarding groundwater quality.

Coupled three-dimensional modelling of groundwater-surface water interactions for management of seawater intrusion in Pingtung Plain, Taiwan

Study regionA coupled framework, linking subsurface flow and surface hydrodynamics, is developed and applied to a real-world case study of Pingtung coastal aquifer in southwest of Taiwan, in East Asia. Study focusFEFLOW is adopted to develop a 3-D variable density and transient groundwater model of the Pingtung shallow aquifer lying 250 m below mean sea level (MSL). This model is coupled with a 1-D river network model, comprised of the main river and its two tributaries, using MIKE 11 through the IFM MIKE 11 coupling interface. The model is capable of analysing the relationship between rainfall, surface water and groundwater recharge lag time. Also, the analysis of potential river inundation and maximum river discharge enable the model to choose the best location to apply artificial recharge as a management scenario to mitigate the effect of seawater intrusion (SWI). To the authors’ knowledge, the developed coupled model is the first detailed integrated framework analysing the interaction of surface and subsurface water, with the capability to contribute to the restoration, rehabilitation, and management of the river network. New hydrological insights for the regionThe rainfall ratio in the wet season to dry season is significant in this plain comparing with the rest of Taiwan. Also, southern Taiwan experiences the largest sea and river interaction, while Kaoping River playing as a pathway role for inland lead of seawater intrusion.

Consequence of Seawater Intrusion on Soil Properties in Agricultural Areas of Nonthaburi Province, Thailand

Seawater intrusion associated with climate change and sea level rise (SLR) has been postulated for the last decade that causes negative impact on worldwide environmental resources. In Thailand, however; the pertaining information to its effect on soil properties in agricultural areas has not been clearly reported yet. Hence, this study aimed to investigate the seawater intrusion effect on soil properties in agricultural areas of Nonthaburi Province, Thailand. Five study locations, which anticipated to be affected by seawater intrusion, were selected based on the different distances from the Chao Phraya River. Soil morphological properties at depth of 0-15 and 15-30 cm were recorded, besides disturbed soil samples at depth of 0-15, 15-30, 30-60, 60-90 and 90-120 cm were collected to determine the soil physical and chemical properties. Additionally, the soil electrical conductivity (ECe) and sodium adsorption ratio (SAR) analyses demonstrating soil salinity and sodicity were monthly conducted from March 2018 to February 2019 and their annual average values were calculated. The results revealed that all soils were deep to very deep, consisted of silty clay, clay textures, and its field soil pH varied from 6.0-8.0. Soil saturated hydraulic conductivity rating exhibited that it was very slow to moderate. ECe and SAR values of these soils ranged from 0.21-4.38 dS m-1 and 8.29-41.89 consecutively, which trended to increase from its annual average during March and April 2019 as well as July and August 2019. These results suggested that seawater intrusion could be presumptively regarded as a co-factor affecting the variability of soil salinity and sodicity occurring at the interval of insufficient freshwater content for forcing seawater. The implementation strategies for freshwater management and planning are required to prevent future potential seawater intrusion.

Economic Effects of Seawater Intrusion on Life of Coastal Communities in Sindh Region of Pakistan

Recently rising sea levels and a decrease of Indus water into the delta have resulted in high seawater intrusion at the coastal shores of Sindh. Seawater intrusion has severely affected the livelihood sources of local people. Therefore, this study is conducted with an aim to measure the economic effects of seawater intrusion on the lives of the local population in the deltaic coasts of the Sindh region in Pakistan. This is a quantitative study conducted through a survey questionnaire in the coastal belt of Badin and Thatta districts of Sindh province, Pakistan. A total of 200 participants were recruited in the study through multistage sampling. Results show a significant impact of seawater intrusion on the economic conditions of coastal communities in the province of Sindh, Pakistan. Adverse effects of seawater intrusion can be seen in the shape of a decrease in cultivated land, low agricultural production, decreasing livestock production and fishing quantity.

The interactive effects of the seawater intrusion-affected zones and types of waterways on the surface water quality from the coastal Tien Giang Province, Vietnam.

Although inland surface water bodies have been studied intensively, few studies have looked at the interactive effects of seawater intrusion and waterway types on the water quality. The current study aimed to (1) assess the inland water quality as affected by waterway types and seawater intrusion-affected zones, (2) examine the longitudinal dynamics of the water quality, and (3) quantify the contributive percentage of pollution sources in the coastal Tien Giang Province, Vietnam. A total of 680 surface-water samples were taken from 34 sites distributed over the Tien River and its tributary canals from 2015 to 2019. The water samples were analyzed for 16 physical, chemical, and biological parameters, which were used for water quality index (WQI) estimation and subjected to two-way ANOVA and principal component analysis/factor analysis (PCA/FA). The WQI in both waterway types tended to get better from the downstream to the upstream zone with an improving rate of WQI faster in the River (from 79 to 88) than in the canals (from 82 to 85). The PCA/FA showed that water from the two waterway types could be polluted by six main pollution sources, one of which was derived from the seawater intrusion, one from aquaculture, and the others from agricultural, residential, and industrial activities. In brief, the inland surface water quality of a coastal area was interactively influenced by spatial distance and waterway types, transferring various pollutants in and out of the inland area.

Temporal NDVI analysis to detect the effects of seawater intrusion on rice growth in coastal areas

As population size grows over time, staple food production also needs to keep up with increased annual demands. In Indonesia, the agricultural sector applies intensification and extensification to maximize rice productivity. However, farm extensification can instead decline productivity, should it sprawl into marginal lands like the study area that has been affected by sea-level rise impact, i.e., surface saltwater intrusion. Therefore, this study set out to differentiate paddies into segments affected and unaffected by salinity based on discernible variation in rice growth stages. These stages were determined using a vegetation index, NDVI (Normalized Difference Vegetation Index), calculated from time-series Sentinel-2 L2A+B image data from 2015 until 2020. The resulting temporal NDVI showed two cropping patterns year-round but with different planting times. In salinity-unaffected paddy segments, farmers began the inundation-transplanting stage in late March and ended the cropping season with fallow in August. Meanwhile, in salinity-affected segments, the cropping stages were the opposite: inundation in early April and fallow in early September. The measurable impact of salinity was apparent at the vegetative-generative stage, where salinity-affected paddies had the highest NDVI of 0.64–0.65, whereas those unaffected had the highest NDVI of 0.7–0.75. These index values indicate an impaired rice growth rate due to salinity effects. Compared with the field-measured data, the NDVI showed 85% accuracy, with a Kappa coefficient of 0.87. Meanwhile, the NDVI-EC correlation test produced R-values of 63–85%. Overall, this research has confirmed that remote sensing image and technology can acquire variable data that explain salinity effects on coastal paddies.

Contamination Transport in the Coastal Unconfined Aquifer under the Influences of Seawater Intrusion and Inland Freshwater Recharge-Laboratory Experiments and Numerical Simulations.

The coupled effect of seawater intrusion and inland freshwater recharge plays an important role in contamination transport in coastal heterogeneous aquifer. In this study, the effects of seawater intrusion and inland recharge on contamination transport were investigated by conducting laboratory experiments and numerical simulations. The laboratory tests were conducted in a sand tank considering two scenarios, namely the conditions of landward and seaward hydraulic gradients. The SEAWAT software was applied for validating the contaminant transport in coastal heterogeneous aquifer. The results indicated that the simulated seawater wedge and contours of the saltwater contaminant matched the observed ones well. The length of the seawater wedge in the scenario of seaward hydraulic gradient was smaller than that in the scenario of landward hydraulic gradient, which reflected that the large quantity of inland recharge have a negative effect on the invasion process of seawater. The plume moved mainly downward in the heterogeneous unconfined aquifer for both scenarios. The pollution plume became concave at the interface between each two layers, which was because the velocity of contaminant plume migration increased gradually from the upper layer to lower layer. The migration direction of the front of the plume was consistent with the direction of hydraulic gradient, which indicated that it was influenced by the water flowing. The maximum area of plume in the scenario of seaward hydraulic gradient was slightly smaller than that in the scenario of landward hydraulic gradient. The maximum area and vertical depth of the pollutant plume were sensitive to the hydraulic conductivity, dispersivity and contamination concentration. This study was of great significance to the controlling of pollution and utilization of freshwater resources in coastal areas.

Evaluation of Sea-Water Intrusion in Coastal Aquifers Using both Numerical Methods and Causal Research: A Case Study of Mombasa, Kenya

This research carried out in Mombasa Island links research done in 2020 on the effects of sea-water intrusion and the current state. The aquifer in Mombasa Island is semi-confined and consists of limestone and coral rock. Water samples were collected and tested from 32 boreholes to determine chemical qualities. Results showed that chloride levels ranged from 74 mg/l to 412 mg/l, with 34% of boreholes having high chloride concentration. After modelling using MT3D program results indicated that the boreholes near the ocean were interfered by sea-water intrusion because chloride concentration was high. Control measures to prevent further sea-water intrusion should be put in place. Therefore, from a practical point of view, individuals who have sunk boreholes since 2020 try to mitigate the problem by installing Reverse Osmosis systems within their facilities, to reduce chloride levels from borehole water. The current research analyses the impact of intrusion on the installed RO systems on Mombasa Island, including cost implications, with the view of proposing viable mitigation measures. The reverse osmosis system though expensive would save a lot of chloride entering the bore holes. It is a little bit expensive though but the end results are positive and the chloride levels will reduce the cost of using too much soap.

Ground water copper levels in the seawater intrusion area and the possible physical and chemical dynamics.

Seawater intrusion, a common geological process along the coastal zones, changes the groundwater properties, which are potentially associated with the groundwater copper (Cu) levels. However, there are no studies on the details of groundwater Cu levels affected by seawater intrusion. The groundwater in the seawater intrusion area of Buzhuang Town was sampled to detect the effect of seawater intrusion on groundwater Cu levels. The Cu levels in the local groundwater range between 0.92 and 4.99 μg L-1, which averages about 5 times than those in the non-intrusion area. The Cu deviations (ΔCu) are positive, and increase with more intrusion of seawater. Simulation experiments also confirm that more Cu leaches from sediments when more seawater or brine water is mixed in. The groundwater Cu levels are positively correlated with TDS, Cl-, Br-, SO42-, HCO3-, Na+, K+ and Mg2+. The Cu-bearing minerals in the local groundwater are under-saturated. The CEC of the sediment for the simulated experiments decreases with more mixture of seawater or brine water. CuCO03, Cu(OH)02, CuHCO3+, Cu(CO3)22-, CuCl2-, Cu2+ species in the local groundwater are obviously higher than those in the non-intrusion area, and the levels of CuCl2-, Cu+, CuCO3, Cu2+, CuSO4, CuOH+, CuCl+, Cu2(OH)22+ are positively correlated with the degree of seawater intrusion, indicating the important role of Cl-, HCO3-, OH- complexation on groundwater Cu levels. Thus, ion competition and complexation are the important dynamics of groundwater Cu enrichment along the coastal zones. A new enrichment model of groundwater Cu in the seawater intrusion area is presented. Seawater intrusion should be taken into consideration when the enrichment mechanisms of groundwater Cu are discussed.

Effect of seawater intrusion using real wastewater on an attached biomass system operating a nitrogen and phosphorus removal process

Wastewater treatment plants that are close to the coast and sea level often have problems with seawater intrusion. Because of this, three saline intrusions of 2%, 5% and 10% in volume (socks 1, 2 and 3 respectively) were carried out using actual wastewater. As a technology, a sequential biofilm batch reactor operating an enhanced biological phosphorus removal process was studied. The main focus of the study lies in the impact on the plant's nutrient removal performance during these seawater intrusion events until achieving system recovery. During the study a constant salinity profile was observed without large variations in the reactor after reproducing the seawater intrusions. The COD removal rate decreased below 80% and 65.4% for shock 2 and 3 respectively. In a seawater intrusion of 2% and 5% in volume, corresponding to shocks 1 and 2, TN removal decreased to 66.4% and 71.5%, respectively, and was subsequently restored to previous removal rate values (>80%) 4 days after the shocks, in both cases. TP removal was negative after every shock due to increased concentrations in the effluent resulting from deficient PAO activity. This situation lasted for 9, 10 and 14 days for shocks 1, 2 and 3, respectively, until recovery of performance to the same levels as prior to the shocks.

Fresh and saline groundwater ages and flow dynamics in a perturbed coastal aquifer

Excessive freshwater pumping in coastal areas result in an inland intrusion of the saltwater wedge underlying the freshwater aquifer, leading to salinization of coastal aquifers. While multiple approaches and techniques in the form of analytical solutions, numerical simulations, mass balance calculations and laboratory experiments have been used to study the flow dynamics of the density-driven circulation of saltwater, little is known regarding the groundwater ages in coastal aquifers and the process timescales. The current study makes use of multiple age tracers such as 3H, 85Kr and 39Ar, allowing to calculate both modern and sub-modern groundwater ages. The ages derived based on the measured tracer values were compared to a numerical flow simulations. The results indicate that seawater intrusion in the Nitzanim coastal reserve (prompted by excessive freshwater pumping upstream) has a different effect on the ages of the shallow groundwaters in comparison with the deeper groundwater. Close to the shoreline (<~200 m) at shallow depths (<40 m below sea level), the intruding saline groundwater is younger than the freshwater system leading to young ages of <50 years. Further away from the shoreline (~700 m), at greater depths (~60 m below sea level), the deep intruding saline groundwater is dated to ~350 years, which is significantly older than fresh groundwater ages in this part of the coastal aquifer. The approach brought forward in the paper allows to better understand the timescales of density-driven circulation mechanism and the effect of seawater intrusion on groundwater ages.

222Rn, 210Pb and 210Po in coastal zone groundwater: Activities, geochemical behaviors, consideration of seawater intrusion effect, and the potential radiation human-health risk

Groundwater quality in human-influenced coastal landscapes is receiving novel attention. Radionuclides have been recognized as another important monitoring indicator in many developed countries due to the discovery of extremely high level of natural 210Po (up to 10,000 Bq/m3) and radium and radon isotopes. This study aims to evaluate the groundwater quality in the Beibu Bulf-Guangxi coast from radiological point of view. 210Po, 210Pb and 222Rn activities in 20 wells ranged from 0.24 ± 0.05 to 6.96 ± 1.62 Bq/m3, 2.17 ± 0.12 to 13.08 ± 0.74 Bq/m3 and 1500 ± 200 to 31,800 ± 900 Bq/m3, respectively. Compared with research data of other countries, groundwaters in this area have 210Po, 210Pb and 222Rn activity within low levels. The large deficiencies of 210Po and 210Pb relative to 222Rn in groundwaters implied that 210Po and 210Pb are strong particle-reactive radionuclides and they might be controlled by similar scavenging processes in groundwaters due to a good positive correlation between 210Pb and 210Po (R2 = 0.67, p < 0.01). The concentrations of 210Po and 210Pb decreased with increasing pH values and salinity, which indicated that geochemical behaviors of 210Po and 210Pb in groundwater were influenced by seawater intrusion and pH changing. Groundwater 222Rn activity concentrations decreased with increasing salinity in coastal zone, which may be caused by dilution due to seawater intrusion or intensified 222Rn escaping from well-developed pores in coastal zone. The estimated annual ingestion doses for infants, children and adults were well below the recommended reference dose level (RDL) of 0.2–0.8 mSv/a, suggesting that consumption of analyzed groundwaters is safe from radiological point of view.

Study on geochemistry of sea water intrusion effect in Jailolo geothermal system

The possibility of seawater intrusion in geothermal systems is very likely to occur. This is caused by several locations of geothermal systems which are very close to the coast. This paper presents a geochemical analysis of the data manifestations of water and gas, to determine the effect of sea water on the Jailolo geothermal system. From the results of the water analysis, it is clear that the effect of sea water intrusion on the Jailolo geothermal system is shown in the anions and cations diagrams, which is almost all of the plots very close to the seawater points. So that the next analysis is focused on the position of mixing sea water with reservoir water and correction of the parameters that are affected by the mixing of sea water. It is intended that the resulting geochemical model can describe the actual reservoir conditions. If we did not include the correction factor to the calculation this will lead into mislead assessment of the reservoir temperature of geochemistry model which is the final result of the study/assessment. It is also necessary take into account for the next step of the process which is exploitation phase.

Geochemical Characteristics and Influencing Factors of Groundwater Fe in Seawater Intrusion Area

To reveal the influencing process and mechanism of seawater intrusion on groundwater Fe in coastal zones, the local groundwater in Buzhuang Town, together with those in the neighboring area where no seawater intruded, was sampled and comparatively analyzed, and the static simulation experiments were also performed in laboratory. The local groundwater has Fe levels of 6.09–196.96 μg/L, with an average of 73.38 μg/L, but groundwater Fe levels from the neighboring area are 1.3–17.7 times of those in local groundwater. Such facts indicate the groundwater Fe levels decreased due to seawater intrusion. The groundwater Fe levels are significantly negatively correlated with pH, significantly positively correlated with Ca2+, Mg2+, and positively correlated with SO42−. The simulation experiments indicate leached Fe increases with a greater mixture of seawater, increasing concentrations of NaCl and CaCl2, but decreases with increasing NaHCO3 concentrations. Fe(OH)2 and Fe(OH)3 minerals are super-saturated because of the high pH and high OH− concentration resulting from seawater intrusion. By this way, the dissolving ability of groundwater Fe is restricted. Therefore, pH is the key factor determining groundwater Fe levels in coastal zones. Another, the decreasing of Ca2+, Mg2+ in groundwater decreases Fe levels because of the co-precipitation and deactivation of groundwater Fe. Salt effect and NaHCO3 contribute less to groundwater Fe levels because of the restriction of maximum Fe solubility by high OH− and super-saturation of Fe-bearing minerals. The influencing model of groundwater Fe levels under the effect of seawater intrusion is forwarded.

Seawater intrusion impacts on groundwater and soil quality in the northern part of the Nile Delta, Egypt

Seawater intrusion (SI) is thought to be a significant threat to groundwater and soil quality in arid costal ecosystems, causing a reduction in freshwater availability and soil productivity. This study investigated the effects of seawater intrusion on soil and groundwater quality in the Nile Delta region at 16 sites located at distances of 5–45 km from the coast. We found that groundwater and soil quality were significantly affected by seawater intrusion. Results from the investigations indicated that: (1) the salinity and alkalinity of groundwater and soil pore-water decreased with increasing distances towards the inland, and showed significant positive correlations for EC, SAR, Na+ and Cl− by 0.80, 0.46, 0.78 and 0.66 respectively offshore (45 km); (2) there were significant positive correlations between salinity and alkalinity of both groundwater and soil pore-water inland up to 15 km distance from the coast;(3) mixing ratio values (F%) of seawater and groundwater were 9.30 to 37.56% in different sites, recording a maximum value close to the sea (5 km), while a minimum value was observed offshore (45 km); and (4) increasing seawater intrusion had negative impacts on the quality of groundwater and soil up to 15 km from the sea, providing the possibility of exploiting irrigated land in Nile delta up to 15 km from the Mediterranean sea.