Marine Water Intrusion Research Articles

A Three-Dimensional Geological Model of the R’Mel Aquifer, Northwestern Morocco

One of the challenges of 3D geological modelling is the spatial representation of heterogeneous sedimentary rocks. The R’Mel coastal basin located in northwestern Morocco is a very suitable area for the modelling of sedimentary rock formations. This basin is part of the external Pre-Rif area and is composed of rocks of Miocene to Quaternary age (principally sand, marl, sandstone, silt, and alluvia). Due to the impact of climate change, any increase in the abstraction of groundwater can accentuate its vulnerability to marine water intrusion. Therefore, understanding of geometry of this aquifer is so important. To achieve this, a 3D geological model was developed to determine the different HydroGeological Units (HGUs) of the R’Mel aquifer. The processing and the construction of a GIS database including a detailed geological map, 125 boreholes, and 50 vertical electrical soundings (VESs), as well as the development of five geological cross-sections, helped build this model using 3D modelling software. The model provides a detailed visualization of the spatial distribution of the eight HGUs. HGUs 3 and 6 consist of marly-clayey lenses and five HGUs of Plio-Quaternary age are composed of: sand or/and sandstone (HGU 1), calcarenites and lumachelles (HGU 2), sandstone and/or shelly marine sand (HGU 4), gravel with a sandy-clayey matrix (HGU 5), and shelly sandstone and gravelly sand (HGU 7). The eighth layer (HGU 8) is composed of marls and clays of Miocene age. The generation of several geological sections from the model made it possible to identify anticlines, synclines and faults trending NNW–SSE and NNE–SSW. Theses, support the tectonics of the Gharb basin during the Mio-Plio-Quaternary. Finally, a conceptual model of the R’Mel aquifer was developed.

SOCIO-ECONOMIC IMPACTS OF MORPHOLOGICAL DYNAMICS INDICATORS AND ECOLOGICAL CHANGE IN THE FISHERIES OF LAKE NOKOUÉ (SOUTH BENIN)

Lake Nokoué is experiencing serious environmental problems which threaten its existence and contribute to the reduction of goods and services for the beneficiary population. The objective of this study is to understand the dynamics of ecological factors and their impacts on the biocenosis. This study is based on bathymetric data collected in 11 stations on the lake following seasonal sampling from February 2017 to January 2018 and from March 2019 to February 2020. Documentary research, field surveys, interview guides, a camera digital and labeled sachets are the tools and materials used for data collection from 120 households. In addition, images from aerial and satellite photographs of the LANDSAT type (TM and ETM) were used to assess the dynamics of the acadjas of Lake Nokoué. The results were analyzed with the FPEIR model. The results show that from 2000 to 2020 Lake Nokoué experienced an increase in the number of acadja which went from 667 to 1417 or 47.07% followed by a decrease in its depth from West to East of the order of 0.5m. The factors favorable to the filling of Lake Nokoué are according to 70% of the population surveyed: the flood and its solid inputs, the proliferation of water hyacinth in the rainy season and its degeneration in the dry season, the erosion of the banks, the intrusion of marine water and stations with high human and economic densities (implantation and decomposition of acadja, agricultural activities, etc.). These internal and external factors contribute to the morphological dynamics of Lake Nokoué, thus hindering the socio-economic development of populations dependent on Lake Nokoué. Faced with this situation, measures have been proposed for better management of this ecosystem, which is essential to the survival of its population.

Coastal squeeze on temperate reefs: Long-term shifts in salinity, water quality, and oyster-associated communities.

Foundation species, such as mangroves, saltmarshes, kelps, seagrasses, and oysters, thrive within suitable environmental envelopes as narrow ribbons along the land-sea margin. Therefore, these habitat-forming species and resident fauna are sensitive to modified environmental gradients. For oysters, many estuaries impacted by sea-level rise, channelization, and municipal infrastructure are experiencing saltwater intrusion and water-quality degradation that may alter reef distributions, functions, and services. To explore decadal-scale oyster-reef community patterns across a temperate estuary in response to environmental change, we resampled reefs in the Newport RiverEstuary (NRE) during 2013-2015 that had previously been studied during 1955-1956. We also coalesced historical NRE reef distribution (1880s-2015), salinity (1913-2015), and water-quality-driven shellfish closure boundary (1970s-2015) data to document environmental trends that could influence reef ecology and service delivery. Over the last 60-120 years, the entire NRE has shifted toward higher salinities. Consequently, oyster-reef communities have become less distinct across the estuary, manifest by 20%-27% lower species turnover and decreased faunal richness among NRE reefs in the 2010s relative to the 1950s. During the 2010s, NRE oyster-reef communities tended to cluster around a euhaline, intertidal-reef type more so than during the 1950s. This followed faunal expansions farther up estuary and biological degradation of subtidal reefs as NRE conditions became more marine and favorable for aggressive, reef-destroying taxa. In addition to these biological shifts, the area of suitable bottom on which subtidal reefs persist (contracting due to up-estuary intrusion of marine waters) and support human harvest (driven by water quality, eroding from up-estuary) has decreased by >75% since the natural history of NRE reefs was first explored. This "coastal squeeze" on harvestable subtidal oysters (reduced from a 4.5-km to a 0.75-km envelope along the NRE's main axis) will likely have consequences regarding the economic incentives for future oyster conservation, as well as the suite of services delivered by remaining shellfish reefs (e.g., biodiversity maintenance, seafood supply). More broadly, these findings exemplify how "squeeze" may be a pervasive concern for biogenic habitats along terrestrial or marine ecotones during an era of intense global change.

Predictable shifts in diversity and ecosystem function in phytoplankton communities along coastal salinity continua

AbstractSalinity is a major environmental predictor of phytoplankton species richness and composition. We hypothesize that the variation in phytoplankton richness along coastal salinity gradients is reflected in essential ecosystem functions like resource use efficiency (RUE)—the proportion of limiting resource that is converted into biomass. To test the hypothesis, we analyzed time series of phytoplankton and environmental variables from the Chesapeake Bay and the Baltic Sea. We analyzed the relationship among salinity, diversity, and RUE in bivariate and interaction association, and in structural equation model (SEM)—a form of path analysis to resolve multivariate relationships among interrelated variables. We concluded that the intrusion of marine water will lead to rapid change in species diversity on the fresh side. Despite diversity drop, individual community functions, like RUE, remain relatively resilient, reflecting functional redundancy. We propose that the salinity gradient also reflects trophic complexity, allowing stable resource use at reduced diversity.

Hydrochemical appraisal of groundwater quality for drinking and irrigation: a case study in parts of southwest coast of Tamil Nadu, India

The quality of groundwater standards in Muttom–Mandaikkadu coastal stretch is the focus of the present study, whose coastal aquifers are particularly at risk due to intrusion of marine water. Thirty groundwater samples were scrutinized for the assessment of physical and chemical parameters during January and June. Hydrochemical characteristics were spatially depicted to understand the spatial variations such as (pH, EC, TDS, Na+, K+, Ca2+ and Mg2+, SO42−, HCO3−, and Cl−). Drinking water quality index based on those 11 parameters and irrigation water quality index based on EC, Na%, sodium adsorption ratio and permeability index was used to assess the water quality for drinking and irrigation, respectively. These results demonstrate that dominant hydrochemical facies for groundwater in both months are Na-K-Cl-SO4 type and Ca-Mg-Cl-SO4 type. The USSL diagram endorses that most of the water samples belong to low-medium salinity with low sodium hazards. Cl−/HCO3− ratio indicates that the majority of the samples show low to moderate seawater intrusion in the study area. Additionally, six vertical electrical sounding measuring points (Schlumberger array) were carried out in order to determine the number of the underlying layers, aquifer depths and their thicknesses as well as its influence by the marine water. The geophysical self-potential measurements suggest that the groundwater in the Manavalakurichi area is prone to contamination by seawater intrusion, confirmed by the use of Schlumberger vertical electrical sounding. For better understanding, the subsurface layers were shown in a 2D model using the constructed geoelectrical cross section.

Using multiple environmental proxies and hydrodynamic modeling to investigate Late Holocene climate and coastal change within a large Gulf of Mexico estuarine system (Mobile Bay, Alabama, USA)

A high degree of uncertainty exists for understanding and predicting coastal estuarine response to changing climate, land-use, and sea-level conditions, leaving geologic records as a best-proxy for constraining potential outcomes. With the majority of the world's population focused in coastal regions, understanding how local systems respond to global, regional, and even local pressures is key in developing mitigation, adaptation, and management plans. The geomorphology of Mobile Bay in southeast Alabama (USA) has evolved considerably (e.g., bayhead delta back-stepping) over the late Holocene in response to global and regional sea-level and climate change. Smaller-scale geomorphic changes (e.g., spit and beach ridge development) have also had a significant influence on the evolution of the estuary. Organic matter characteristics, inorganic sediment geochemistry, benthic microfossils, and pollen in a ~ 3500 cal yr BP sediment sequence recovered in a gravity core (20GC) from Bon Secour Bay, a small sub-bay in the southeast corner of Mobile Bay, record time-varying marine influence. Increases in marine influence during ~3500 to 2300 cal yr BP and 1930 to 1160 cal yr BP are defined as zones with high-density and pre-dominantly calcareous foraminiferal species, abundant sand (>10%) and more marine-like geochemical signatures, which contrast the low-density and pre-dominantly agglutinated foraminiferal and more terrestrially influenced estuarine muds observed in other intervals of the sedimentary record (2300–1930 and 1160–400 cal yr BP) and the modern bay. Hydrodynamic models constrained by geomorphic boundary conditions for the time ~ 3500 cal yr BP, consistent with the most prominent marine-influenced sediment, provide insight to potential coastal configuration that might have permitted such marine water intrusion into the bay. Of several scenarios evaluated, a breach in Morgan Peninsula produces tidal circulation within the basin supportive of persistent marine incursions in the bay between ~3500 to 2300 cal yr BP. The findings show that slight variations in coastal configuration can have broad-scale effects on bays and estuaries with consequences that may relate to water quality, vertebrate and invertebrate habitat, and coastal vulnerability to episodic events like (extra)tropical storms.

Salt variation induces oxidative stress response in aquatic macrophytes: The case of the Eurasian water-milfoil Myriophyllum spicatum L. (Saxifragales: Haloragaceae)

Wetlands are very fragile systems and susceptible to being affected by human activity. S'Albufera de Mallorca Natural Park is the main wetland in Mallorca Island (Spain), and undergoes a salinization process derived from the overexploitation of adjacent aquifers, which favors marine intrusion. The objective was to evaluate the effects of salinity changes in a channel in s'Albufera de Mallorca through the analysis of biomarkers of oxidative stress in the submerged macrophyte Myriophyllum spicatum. Six different points were analysed along a channel characterized by different salinity values, ranging from ~2 to ~11. The % of macrophyte coverage in the studied stations followed an inverse salinity pattern with greater coverage in areas of low salinity and minimal coverage in those with higher saline concentration. The photosynthetic pigments index (D430/D665), determined in M. spicatum leaves, was significantly higher at the stations most affected by salinity. All antioxidant enzyme activities – catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase – followed a similar pattern of response with an increase in activity as salinity increases. Similarly, the levels of malondialdehyde, as marker of lipid peroxidation, were also increased the stations with the highest salinity. In conclusion, marine water intrusion causes an increase in the salinity of inland waters in s’Albufera de Mallorca, which is evidenced by the increase in the antioxidant enzyme activities and oxidative damage.

Holocene sedimentary and environmental development of Aarhus Bay, Denmark – a multi‐proxy study

Holocene sedimentation patterns and environmental development in Aarhus Bay, Denmark, were reconstructed based on proxy analyses of two sediment cores (M1 and M5). Together, the two cores offer an opportunity to examine the history of the area during the past c. 10 000 years. The investigation consisted of acoustic mapping and multi‐proxy analyses of the sediment cores including macrofossils, sediment physical properties, sediment accumulation rates, grain size, and X‐ray fluorescence elemental counts. Radiocarbon dating of the two sediment successions revealed that they cover the periods c. 10 000–3700 cal. a BP (M1) and c. 4400 cal. a BP to the present (M5). The data from the M1 site indicate the presence of a near‐shore lake environment between c. 10 000 and 9000 cal. a BP. The first intrusion of marine water into the area is dated to c. 9000 cal. a BP. In the following c. 1300 years, brackish‐water conditions prevailed in the area characterized by a mixture of taxa from marine, limnic and terrestrial habitats, reflecting a shallow estuarine environment. Around 7700 cal. a BP full marine conditions were established, accompanied by a marked increase in sedimentation rates. The changes to full marine conditions and higher sedimentation rates are probably due to a significant sea‐level rise leading to flooding of former land areas and intensified erosion. A subsequent distinct decrease in sedimentation rates around 6350 cal. a BP is presumably linked to a previously documented sea‐level drop about this time. Continuous sedimentation ceased around 3700 cal. a BP in the central part of the bay, most probably due to a major sea‐level lowering involving widespread erosion. In the eastern and deeper part of the bay, sedimentation continued until today. Fully marine conditions prevailed there for at least the last 4400 years.

Drivers of deep water renewal in Macquarie Harbour, Tasmania

Abstract Macquarie Harbour is a fjord-like estuary located on the west coast of Tasmania and is home to a growing aquaculture industry. The harbour is oriented with the mouth on its north west end and two main tributaries located on its northeast and southeast ends. Both of the system's major tributaries have hydroelectric power schemes controlling catchment discharge into the harbour. The harbour has a history of low oxygen concentrations and the bottom water is often oxygen poor. No study to date has described the underlying mechanisms of deep water renewal and oxygenation in the system. Approximately 5 years of data from monthly dissolved oxygen, salinity, and temperature profiles, located throughout the harbour, and 3 continuous logger stations was analysed with water level and meteorological data. These data were used to describe the drivers of water level and deep water oxygen renewal in the system. This study provides a first order estimate of the net mass of dissolved oxygen entering via these marine water intrusion events. Data analysis indicates that deep water renewal appears to occur episodically, with only 2 significant events recorded over a 5 year period, though a number of smaller events were also recorded on a monthly basis. The largest events were observed during winter and late autumn and are associated with strong north westerly winds and a sudden drop in atmospheric pressure. The drop in pressure results in an increase in water level that allows marine water to enter the harbour via the mouth. The north westerly winds act to push surface water to the southern end of the harbour allowing more water to flood over the sill into the Sophia basin. Analysis of oxygen, temperature and salinity logger data indicates that larger renewal events create water column instabilities which can provide a potential threat to the salmon aquaculture industry situated in the harbour. The frequency of renewals also has implications on the standing oxygen concentrations in the harbour, with fewer events likely resulting in greater periods of hypoxia in the bottom and mid water column.

Hydrogeochemical and isotopic signatures for the identification of seawater intrusion in the paleobeach aquifer of Cox's Bazar city and its surrounding area, south-east Bangladesh

In order to better understand the encroachment of seawater into the groundwater system a total 115 groundwater samples were collected in an area of ∼7 km2 in Cox's Bazar paleobeach and its vicinity, from different types of tubewells, which included hand pump fitted bore wells (<50 m depth), moderately deep energized bore wells (50 m–100 m depth) and deep bore wells (>100 m depth) during June 2013. A combined hydro-geochemical indicators, selected trace elements (Sr and B) and in addition to δ18O and δ2H were used in this study. Results show that the high values of EC (202 μS/cm to 6730 μS/cm) and TDS (135 mg/L to 4509 mg/L) are found in groundwater of wells closer to the coast and few wells from the northern and central part of the study area. The cross plot of HCO3/Cl and TDS shows that groundwater along the paleobeach and some isolated areas are saline with TDS > 1000 mg/L, associated with high ratios of Cl/TDS (0.065). The groundwater facies generally evolves from freshwater (Ca-Mg-HCO3) to saline water (Na- Cl) type with an intermediate Ca-Mg-Cl type indicating that the aquifer system interacts with seawater and undergoes cation exchange. Results also reveal that the area affected by marine water intrusion has ionic ratios of Br/Cl (0.0006–0.0021) similar to seawater (0.0015) with some higher values. Groundwaters along the paleobeach and some isolated areas, low ionic ratios of SO4/Cl (0.01–6.53) and Na/Cl (0.20–152.09), relative to marine ratios (0.05 and 0.86 respectively), are also observed. Groundwaters with Seawater Mixing Index >1.0 and TDS >1000 mg/L constitute about 20% of the studied groundwaters and have relatively high δ18O (>- 4.0‰) values and the linear relationships between TDS and most of the ions, including B and Sr, and the chemical signature of the saline plumes (e.g., marine SO4/Cl, Na/Cl and Br/Cl ratios) suggest that mixing processes control the chemical composition of the seawater within the aquifers. However, these geochemical variations also reveal that the quality of potable water has deteriorated to a large extent due to seawater intrusion along the paleobeach, migrating inland toward the heavily groundwater exploited areas from the coast line and may entail various future health hazards.

Determination of groundwater parameters for drinking and agricultural use in the coastal region of Engiz Aquifer System, Samsun (Turkey)

The aims of this study are to evaluate the physico-chemical properties of groundwater in the Engiz Aquifer System, determine the sea water intrusion, and investigate suitability of groundwater for both agricultural and drinking purposes of Samsun City in Turkey. It was interpreted whether groundwater was suitable for drinking and the parameters analyzed were checked according to the standards determined by the Turkish drinking water standard (TSE 266 2005). The use of groundwater for irrigation purposes was classified based on the Water Pollution Control Regulation of the Turkish Republic, Criteria for Inland Surface Water Classification (WPCR 2004). The groundwater samples of the Engiz Aquifer System were analyzed for major anion and cations, trace elements, pH, EC, and TDS. The groundwater samples are Ca-Mg-Na-SO4 and Ca-Mg-Na-Cl water types. The groundwater samples are not suitable for drinking because of the high levels of Na, Al, As, Fe, and Ni. Besides, %Na and SAR values indicate that the water is suitable for only salt-tolerant and semi-tolerant crops under suitable irrigation circumstances. According to the Mg Hazard and PI values, 30 and 70%, respectively, of the groundwater samples are not suitable for irrigation in the basin. It is thought that the groundwater salinity is increasing in the future because the groundwater wells are close to the Black Sea coast and there is some intrusion of saline marine waters.

Geoelectrical investigations for aquifer characterization and geoenvironmental assessment in northern Morocco

The Mediterranean mountains of Morocco (“Rif”) show an intense sensitivity to hydro-climatic hazards. Hydrologic achievements are thwarted by a series of constraints that request strategic consolidation. The acceleration of socioeconomic activities is causing an increasing pressure on water resources that are already facing insufficiency and degradation problems. This paper aims at geophysical characterization of the most important intramountainous alluvial aquifer on the Rif, Ghis–Nekor. Its electrical and hydrogeological properties are investigated through a correlation of 2D electrical resistivity tomography (ERT), vertical electrical sounding (VES) and borehole data. The results have shown that this monolayer coastal aquifer is constituted of large coarse sand, gravel and pebble deposits that overlay substrata of different hydrogeological and electrical types. A geoenvironmental survey was also carried out in the coastal zone and near the uncontrolled waste landfill of Beni Bouayach. The 2D ERT profiles indicate an increase of marine water intrusion (over 2 km) particularly on the eastern bank of the Nekor river. They also show a spread of the landfill leachate flow path beyond 1 km in the direction of the groundwater flow (to the North), towards an area of hydrogeological interest located east of the city of Imzouren. These results imply a socioeconomic and environmental vulnerability that evokes an immediate intervention to restore weakened equilibrium.

Hydrogeochemical appraisal of groundwater quality in the Ga west municipality, Ghana: Implication for domestic and irrigation purposes

This study was conducted to appraise the quality of groundwater for irrigation and domestic water supply in the Ga West Municipality, Ghana. A total of 29 borehole water samples were collected for hydrogeochemical analysis and interpreted using hydrogeochemical plots and multivariate statistical analysis. The relative abundance of the major ions in the analyzed water samples were in the order Na+ > Ca2+ > Mg2+ > K+ and HCO3− > Cl− > SO42−. Trilinear Piper plot shows that NaHCO3Cl and NaCaHCO3Cl are the dominant water types in the area. The Ca2+ and HCO3− in these type of waters are primarily from dissolution of carbonate minerals whilst the Na+ and Cl− may have been input from water-rock interaction with granitic rocks, seawater intrusion, and anthropogenic activities in the watershed. All the analyzed physico-chemical parameters are within the acceptable limits of the World Health Organization (WHO) for drinking except TDS, total hardness, Na+, and Cl− which could be as a result of solid waste leachate and marine water intrusion. The samples have low to medium sodium hazard values with high to very high salinity hazard values when plotted on the Wilcox diagram. This suggests that the water is suitable for irrigation purposes with regard to sodium hazard but a mixing of the high salinity water with low salinity water is highly recommended prior to irrigation to reduce the salinity hazard in the area. However, if the crops are salt tolerant, then mixing is not necessary. Three factors explain 99.8% of the total variance and suggest that water–rock interaction is the most important factor that controls the groundwater chemistry. Besides, some contribution from agricultural activities and seawater mixing are the other factors influencing the groundwater chemistry. These factors are indicated by the positive correlation among the individual hydrochemical parameters.

Using Water Quality Index for Assessing of Physicochemical Quality of Quaternary Groundwater in the Southern Part of Abidjan District (C&amp;#244;te d’Ivoire)

In this study, fourteen physicochemical parameters were monitored at 61 groundwater sampling points located in the southern part of Abidjan District. Each water sampling location was sampled in March and July 2007, representing respectively the long dry season and the long wet season. Groundwater evaluation index and statistical methods were used to assess Quaternary groundwater physicochemical quality in term of drinking and irrigation purposes. The groundwater samples irrespective of seasons fell in mixed K-Na-HCO3 and K-Na-Cl types. Groundwater quality index values varied from 14.01 to 593.44 and from 20.88 to 567.44, in dry and rainy seasons, respectively. In both seasons, 9.83% exhibited poor water quality and 3.27% indicated unsuitable water for drinking purposes. The studied water wells were heavily contaminated with nitrate, nitrite and ammonium in the strongly urbanized areas at Treichville, Koumassi, Marcory, Port-Bouet and Grand-Bassam. The degree of correlation between physicochemical parameters suggested that groundwater quality was mainly related to geogenic (rock–water interaction) and anthropogenic sources (domestic sewage), and intrusion of marine and lagoon waters in the study area. Sodium adsorption ratio was generally low during study period, indicating most groundwater sampled was suitable for irrigation purposes.

REY geochemistry in groundwater from Paratunka geothermal area (Kamchatka peninsula, Far East of Russia)

New data on geochemistry of the Paratunka deposit of mineral waters—Russian biggest geothermal system is presented in this paper. Studied waters are thermal (T = 45–80 °C), alkaline (ph = 7.9–8.7), belong to Ca–Na Cl–SO4 type with reducing environment (Eh = − 150 to − 180 mV) leading to Ce- (+ 0.31) and Eu- (+ 0.8) anomalies. Evolution of chemical type of thermal water from Na–SO4 to Ca–Cl is discussed from the point of water–rock interaction and marine water intrusion as well. REY concentrations are extremely low due to alkaline pH (∑REY = 25–165 ppt). First reliable data on REY concentration in alkaline thermal water, surrounding river water and suspended matter of these waters gave an opportunity to discuss cerium, europium and yttrium anomalies in terms of sorption/desorption processes and pH/Eh dependencies, confirmed by thermodynamic calculations of the REE migration forms.

Groundwater Overexploitation and Seawater Intrusion in Coastal Areas of Arid and Semi-Arid Regions

The exploitation of groundwater resources is of high importance and has become very crucial in the last decades, especially in coastal areas of arid and semi-arid regions. The coastal aquifers in these regions are particularly at risk due to intrusion of salty marine water. One example is the case of Tripoli city at the Mediterranean coast of Jifarah Plain, North West Libya. Libya has experienced progressive seawater intrusion in the coastal aquifers since the 1930s because of its ever increasing water demand from underground water resources. Tripoli city is a typical area where the contamination of the aquifer in the form of saltwater intrusion is very developed. Sixty-four groundwater samples were collected from the study area and analyzed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters Electrical Conductivity, Na+, K+, Mg2+, Cl− and SO42−, which can be attributed to seawater intrusion, where Cl− is the major pollutant of the aquifer. The water types according to the Stuyfzand groundwater classification are mostly CaCl, NaCl and Ca/MgMix. These water types indicate that groundwater chemistry is changed by cation exchange reactions during the mixing process between freshwater and seawater. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 25 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high NO3− concentration in the region.

Hydrological Studies of the Dniester Estuary in 2012-2017

Purpose. The study of the features of long-term changes of the Dniester Estuary hydrological regime main characteristics in 2012-2017 based on the results of annual surveys performed by Odessa National I. I. Mechnikov University. Methods. Measuring of the water transparency, temperature and electrical conductivity in the surface and near-bottom layers were carried out using standard techniques with Secchi disk and portable HACH analyser with temperature and conductivity sensors. Results. Based on the studies performed, almost two times decrease in water transparency values in summer of 2012-2017 has been established compared with the same period of 2003-2011. It was shown that the maximum transparency values were observed in the southern part of the estuary, where the presence of seawater is almost constant. Analysis of electrical conductivity spatial distribution has revealed practically constant influence effect of seawater intrusion in the southern part of the estuary, especially in the bottom layer, and periodical influence effect in the middle and northern parts. Significant increasing of the range of water temperature and electrical conductivity variations in the Dniester Estuary has been recorded in summer 2012-2017 comparison with summer 2003-2011. Conclusions. The established peculiarities of hydrological characteristics’ spatial distribution indicate that river discharge and intrusion of marine water are the most important factors determining the Dniester Estuary hydrological regime. Increase of temperature and conductivity of the Dniester Estuary water in summer 2012-2017 in comparison with 2003-2011 was registered. An anomalous penetration of marine waters into most part of the estuary was detected in July 2016, which in the past was observed for the last time in 2011.

Design Concept of an Automated Irrigation System for Simulating Saltwater Intrusion in a Mesocosm Experiment

Coastal wetlands make up about one third of the overall wetland area in the conterminous United Stated based on the Environmental Protection Agency 2016 [1]. Sea-level rise is expected to elevate water salinity and effect carbon sequestration, nitrogen removal, further alter plant communities and shift ecosystem function. To promote understanding of the influence of seawater intrusion into tidal freshwater wetlands, we designed a mesocosm experiment with automated irrigation system at Spring Hill, Storrs, CT, USA (41.8°N, 72.3°W). To simulate marine water intrusion, we designed an automated irrigation to work for an on-going mesocosm experiment, which is composed of 64 tanks with 4 wetland species: Carexstricta, Spartinapectinata, Typhalatifolia, Phragmitesaustralis. During low tide, solenoid valves quantify water based on the instruction of system core controller (Arduino) and water is distributed to assigned tank [2] [3]. During high tide, water is pumped up into assigned tank, salinity is varied with plant species, Carexstricta and Spartinapectinata are fresh water species, Typhalatifolia, Phragmitesaustralis are brackish water species. The manipulation core of system is an open-source microcontroller platform. The irrigation system was designed daily twice change from low tide water level to high tide water level, and same water tank should keep at constant salinity within 30 days. Staff just needs monthly visit to add sea salts, the raw material of artificial seawater. Ecosystem CO2 and CH4 gas exchanges were measured monthly from May to September 2015 using large transparent chambers that enclosed emergent plants and the soil surface; field sampling and analysis procedures followed [4]. The simulated saltwater intrusion results are expected to alter plant growth, emission of carbon dioxide, methane and other greenhouse gases, and effect interaction with coastal marsh ecosystem.

GROUNDWATER PROSPECTING ON THE ONSHORE PORTION OF CAMPOS BASIN, IN MICO LEÃO DOURADO PARK, CABO FRIO MUNICIPALITY, RIO DE JANEIRO, BRAZIL, BY GPR (GROUND PENETRATING RADAR) METHOD

The coastal region of Rio de Janeiro State (Brazil) is strongly influenced by the presence of brackish water in its sedimentary substrate. This study aims to map localities where the intrusion of brackish water in groundwater is taking place and to provide a guiding tool using the Ground Penetrating Radar (GPR) data to search freshwater for social use. The study area is located in Mico Leao Dourado Park, at the northern part of Cabo Frio municipality , Rio de Janeiro State, at 1.5 km from the coast, onshore to Campos Basin. In this region, the potable water is scarce; therefore, the exploration and use of groundwater constitute an important alternative to the local population. We obtained one line of Ground Penetrating Radar (GPR) record on 2D profile through 20 meters depth using 100Mhz antenna in quaternary sedimentary area of the central area of Mico Leao Dourado Park. The method provides variations in the subsoil dielectric discontinuity as a function of GPR electromagnetic wave emission. The brackish water intrusion limited the penetration of GPR waves; thus, at some places, because of the change in conductivity of environment, it was not possible to map larger sediment thickness due to those conditions. Results of this research allowed understanding why freshwater or brackish water is being found in neighboring wells of the study area. The arrangement of the sedimentary layers interleaved with clay lenses allows getting freshwater from holes; and, in places without clay lenses, the wells have brackish water. The layered sedimentary structure seems to delimit the clay lenses which avoid the intrusion of marine water and the salinization of groundwater. The GPR method proved to be a useful tool for the characterization of the sediment layers on the edges of sedimentary basins, such as in Mico Leao Dourado Park, in Cabo Frio Region.

Baseline seasonal investigation of nutrients and trace metals in surface waters and sediments along the Saigon River basin impacted by the megacity of Ho Chi Minh (Vietnam).

The Saigon River, Southern Vietnam, crosses one of the most dynamic developing Megacity in Southeast Asia: Ho Chi Minh City (HCMC). The increased economic, industrial, and domestic developments may affect the environmental quality of water and halieutic resources. In this study, we evaluated the seasonal (dry and wet seasons) biogeochemical state of the Saigon River during two snapshot campaigns conducted along the river basin upstream from HCMC; the Saigon River was characterized by slightly acidic (pH 5.7-7.7) and oxygen-depleted water (dissolved oxygen (DO), 0.36-5.18mgl-1). Nutrients (N-NH4=0.01-2.41, N-NO3=0.14-2.72, and P-PO4=~0-0.42mgl-1), DOC (2.2-8.0mgl-1), POC, and trace metal(oid) (As, Cd, Cr, Cu, Zn, and Hg) concentrations were low showing a good quality of the upstream river. In the urban center area, DO dropped to 0.03mgl-1 accompanied with a rise of nutrient concentrations (e.g., N-NH4, up to 17.7mgl-1) likely originating from wastewater discharges. Trace metal concentrations also rose sharply (e.g., Cr and Hg rose up to 10-fold higher) in both water and sediments but remained under the World Health Organization (WHO) and Vietnamese concentration guidelines. In the downstream estuarine area, the intrusion of marine waters diluted water flowing from HCMC, leading water quality to return close to the state observed upstream from HCMC. In general, levels of nutrient and metal contaminations along the Saigon River during both seasons appear moderate regarding to Vietnamese and WHO guidelines although the urban area is highlighted as the major contributor for metal(oid) emissions. Finally, we showed that apart from wastewater and industrial discharges that affect the river quality, metal(oid) partitioning between solid and solution is controlled by the change in water geochemistry along the continuum during both seasons, such as DO (e.g., for As and Cr) and pH (e.g., for Pb) which drives their sorption/dissolution dynamics.