Surface Water Salinity Research Articles

GIS-based Valuation of Ecosystem Services in the Lower Delta Plain of West Bengal with Special Reference to Indian Sundarbans

The Indian Sundarbans partly hosts the world’s largest mangrove forest and support the livelihood of almost five million people. The Holocene delta of Indian Sundarbans was formed by the river Ganges. The decay of the distributaries of the river Ganges in deltaic West Bengal began with the eastward avulsion of the river Ganges. The rivers of Sundarbans now stand disconnected from their sources and therefore do not get a significant amount of freshwater from upstreams. The people of Sundarbans depend on the services of the Sundarbans ecosystem which is directly linked to the upstream freshwater flow, rainfall and groundwater. The scarcity of freshwater during dry seasons, high salinity of surface water and soil, siltation and drainage congestion are major constraints on livelihood security in this area. The biodiversity of Sundarbans is also threatened by water stress. To ensure the sustainable conservation of the rich biodiversity and well-being of the people of Sundarbans, improving ecosystem services in the region is extremely essential. From this perspective, the present study aims to identify major flow-dependent ecosystem services in the region and estimate the value of those ecosystem services using geoinformatics. The land use land cover (LULC) maps have been prepared for the years 1990, 2000, 2010 and 2020 from Landsat images for the valuation of major ecosystem services. Accuracy assessment has been performed using high-resolution satellite images and field data. Change detection analysis has been done to understand the changing land use pattern in the study area. The LULC-based valuation of the ecosystem services has been carried out for the years 1990, 2000, 2010 and 2020. The area under each LULC class has been multiplied by the global Ecosystem Service Value (ESV) of that class to calculate the total ESV of the specific LULC class. The study reveals that the ESVs are the highest for freshwater bodies including rivers, and estuaries followed by forests. With the decreasing upstream freshwater flow and deteriorating mangrove health, the services of flow-dependent ecosystems have changed drastically.

Multiple controls on carbon dioxide sequestration in the beagle channel (Southern Patagonia) in early fall

Subpolar coastal waters are key hotspots in the global carbon cycle. However, the small-scale distribution of partial pressure of carbon dioxide (pCO2) in these environments and the physical and biological controls underlying this variability are still poorly understood. Here, we examine simultaneous high-resolution spatial measurements of wind speed and pCO2, temperature, salinity, and in-vivo chlorophyll-a fluorescence (chl-a fluo, a proxy of phytoplankton biomass) in surface waters that were obtained during an oceanographic survey in the Argentinian Beagle Channel (subantarctic Atlantic Patagonian) in early fall 2017. The 240 km study transect (centered at 55°S - 67°W) was divided into two zones: (A1) The Beagle Channel innermost portion, semi-enclosed and subject to strong continental influence and (A2) its eastern outlet towards the open Southwest Atlantic. Discrete seawater samples were also collected for apparent oxygen utilization (AOU), nutrients and pH measurements. High-resolution spatial measurements revealed the persistence of pCO2 below atmospheric equilibrium, increasing in median (interquartile range 25–75%) from 314 μatm in the inner Beagle Channel (A1) to 348 μatm towards the adjacent open sea (A2). A decrease in atmospheric CO2 sequestration was associated with an increase in water temperature from 9.5 °C to 10.7 °C, salinity from 30.8 to 32.5, and chl-a fluo from 2.24 to 2.91 mg m−3 along the coastal-offshore gradient. Low AOU and nutrient levels were found in regions inside the channel. Indeed, the relationships between CO2 and temperature or salinity were significantly different from those expected from the theoretical solubility effect, indicating a dominance of metabolic over physicochemical controls on this gas. Moreover, physical factors such as vertical stratification contributed to the variable surface pCO2 values. These findings reveal the existence of short-scale spatial variability of CO2 in the Beagle Channel, improving our understanding of the multiple controls on atmospheric carbon sequestration in extensive subpolar continental shelves.

Distribution and density estimates of cetaceans along the midAtlantic Ridge during summer 2004

During 4 June-2 July 2004, the Norwegian R/V G.O. Sars conducted a multi-disciplinary survey along the mid-Atlantic Ridge (MAR) from the Reykjanes Ridge to north of the Azores. This provided the first systematic survey information on MAR cetacean populations. Using naked eye or 7350 hand-held binoculars, observers searched in a 140° arc centred along the ships’ heading. Eleven cetacean species and 10 other taxonomic groups were identified along 2,321km of transect effort. The sei whale (Balaenoptera borealis) and sperm whale (Physeter macrocephalus) were the most commonly sighted species (53 and 48 sightings, respectively). There were 12 sightings of the fin whale (B. physalus). There were 26, 13 and 12 sightings, respectively of the common dolphin (Delphinus delphis), pilot whale (Globicephala sp.) and striped dolphin (Stenella coeruleoalba). Density estimates of species ranged from 0.018 to 0.238 animals km–2. The precision of the estimates (CV) was low, ranging from 40% to 61%. Species distribution varied north to south; the highest aggregations of baleen whales were sighted at the Charlie Gibbs Fracture Zone (CGFZ). Sperm whales were also observed at the CGFZ as well as north of this area. Pilot whales and Atlantic white-sided dolphins (Lagenorhynchus acutus) were sighted mainly in the cold (5-16°C) and less saline (34.6-35.8‰) water masses along the Reykjanes Ridge. Conversely, common dolphins and striped dolphins were most commonly sighted south of the CGFZ in areas with warmer (12-22°C) and more saline (34.8-36.7‰) surface water temperatures.

Late Quaternary Ponto-Caspian dinoflagellate cyst assemblages from the Gulf of Corinth, Central Greece (eastern Mediterranean Sea)

We present here the first long Quaternary record of organic-walled dinoflagellate cyst assemblages analysed from sediment cores retrieved during the International Ocean Discovery Program (IODP) Expedition 381 in the Gulf of Corinth. Site M0078A is located in the central part of the Gulf of Corinth (GoC), a semi-isolated marine basin that was repeatedly isolated and reconnected to the Mediterranean Sea during the Quaternary glacial/interglacial cycles. Our results show that dinoflagellate cysts are sorted in two major ecogroups, each group alternating between marine and isolated/brackish conditions. The marine intervals are characterised by high dinocyst diversity whereas the isolated intervals are dominated by taxa thriving in low-salinity conditions such as Spiniferites cruciformis and Pyxidinopsis psilata. In several of these assemblages, S. cruciformis is so prevalent that it forms almost monospecific assemblages. The low salinity dinocyst assemblages are reported for the first time outside the Ponto-Caspian region and they show a close affinity to modern assemblages from the Black Sea, Caspian Sea and Marmara Sea. The alternations between marine and brackish conditions recorded in the Gulf of Corinth reflect changes in surface water salinity (SSS) and temperature (SST), in response to the Quaternary glacial-interglacial cycles. These seem to be in good agreement with regional and global marine isotope and sea-level records. Our findings suggest that the study region sensitively responds to climate forcing at orbital time scales and that local factors most likely drive shifts in dinoflagellate species composition and diversity.

Salinization of stream water and groundwater at daily to decadal scales in a temperate climate

AbstractElevated salt concentrations in streams draining developed watersheds are well documented, but the effects of hydrologic variability and the role of groundwater in surface water salinization are poorly understood. To characterize these effects, we use long‐term data (12–19 yr) and high‐frequency specific conductance (SPC) data collected from 13 streams across New Hampshire, USA. Concentration–discharge (C–Q) relationships for chloride (Cl−) derived from high‐frequency SPC showed distinct seasonal variability. Diluting behavior was common, but flushing behavior occurred in autumn and winter, suggesting that both groundwater and surface runoff contribute salts to streams. Long‐term data show that although extreme flood events initially reduced salt concentrations in groundwater and rural streams, concentrations recovered to preflood conditions in about a decade. Chronic Cl− exceedances occurred in urban streams during all seasons. This research suggests that variation in stream flow, extreme events and application of deicing agents play a role in freshwater salinization.

Vertical redistribution of principle water masses on the Northeast Greenland Shelf

The Northeast Greenland shelf (NEGS) is a recipient of Polar Water (PW) from the Arctic Ocean, Greenland Ice Sheet melt, and Atlantic Water (AW). Here, we compile hydrographical measurements to quantify long-term changes in fjords and coastal waters. We find a profound change in the vertical distribution of water masses, with AW shoaling >60 m and PW thinning >50 m since early 2000's. The properties of these waters have also changed. AWis now 1 °C warmer and the salinity ofsurface waters and PW are1.8 and 0.68 lower, respectively. The AW changes have substantially weakened stratification south of ~74°N, indicating increased accessibility of heat and potentially nutrients associated with AW. The Atlantification earlier reported for the eastern Fram Strait and Barents Sea region has also propagated to the NEGS. The increased presence of AW, is an important driver for regional change leading to a likely shift in ecosystem structure and function.

A Review of Current Capabilities and Science Gaps in Water Supply Data, Modeling, and Trends for Water Availability Assessments in the Upper Colorado River Basin

The Colorado River is a critical water resource in the southwestern United States, supplying drinking water for 40 million people in the region and water for irrigation of 2.2 million hectares of land. Extended drought in the Upper Colorado River Basin (UCOL) and the prospect of a warmer climate in the future pose water availability challenges for those charged with managing the river. Limited water availability in the future also may negatively affect aquatic ecosystems and wildlife that depend upon them. Water availability components of special importance in the UCOL include streamflow, salinity in groundwater and surface water, groundwater levels and storage, and the role of snow in the UCOL water cycle. This manuscript provides a review of current “state of the science” for these UCOL water availability components with a focus on identifying gaps in data, modeling, and trends in the basin. Trends provide context for evaluations of current conditions and motivation for further investigation and modeling, models allow for investigation of processes and projections of future water availability, and data support both efforts. Information summarized in this manuscript will be valuable in planning integrated assessments of water availability in the UCOL.

Sustainability of fresh groundwater resources in fifteen major deltas around the world

Population growth, urbanization and intensification of irrigated agriculture in the world’s deltas boost the demand for fresh water, with extensive groundwater extraction as a result. This, in turn, leads to salt water intrusion and upconing, which poses a threat to freshwater and food security. Managing fresh groundwater resources in deltas requires accurate knowledge about the current status and behaviour of their fresh groundwater resources. However, this knowledge is scarcely present, especially for groundwater at larger depths. Here, we use three-dimensional variable-density groundwater model simulations over the last 125 ka to estimate the volume of fresh groundwater resources for 15 major deltas around the world. We estimate current volumes of onshore fresh groundwater resources for individual deltas to vary between 1010 m3 and 1012 m3. Offshore, the estimated volumes of fresh groundwater are generally smaller, though with a considerably higher variability. In 9 out of 15 simulated deltas, fresh groundwater volumes developed over thousands of years. Based on current groundwater extraction and recharge rates, we estimate the time until in-situ fresh groundwater resources are completely exhausted, partly leading to groundwater level decline and mostly replacement with river water or saline groundwater. This straightforward analysis shows that 4 out of 15 deltas risk complete exhaustion of fresh groundwater resources within 300 m depth in 200 years. These deltas also suffer from saline surface water which means their groundwater resources will progressively salinize. With a fourfold increase in extraction rates, seven deltas risk a complete exhaustion within 200 years. Of these seven deltas, six suffer from saline surface water. We stress that the groundwater of these six vulnerable deltas should be carefully managed, to avoid non-renewable groundwater use. The progressive exhaustion of fresh groundwater resources in these deltas will hamper their ability to withstand periods of water scarcity.

Mapping the Changjiang Diluted Water in the East China Sea during summer over a 10-year period using GOCI satellite sensor data

The Changjiang River loads freshwater into the East China Sea (ECS) and the Yellow Sea (YS). A low-salinity plume known as Changjiang Diluted Water (CDW) is formed by mixing with saline ambient waters; it disperses toward Jeju Island and the East/Japan Sea due to the dominant southerly wind and tide during summer. To map the offshore surface CDW in the ECS, a proxy was developed using surface water beam attenuation (c) and salinity from 18 annual summer cruises matched with synchronous Geostationary Ocean Color Imager (GOCI) satellite data. We followed a two-step empirical approach. First, a relationship between in situ salinity and c was obtained from hydrographic cruises (1998, 2003–2018, and 2021). Second, in situ c was matched with GOCI remote-sensing reflectance (Rrs) band ratios of all available blue-to-green wavelengths (2011–2018). Finally, satellite-derived surface salinity was determined directly by combining the two empirical relationships, providing a robust estimate over a range of salinities (22–34 psu). Our algorithm was then compared and validated with five previous satellite-derived salinity algorithms based on colored dissolved organic matter and particle concentrations. In the first step, surface salinity was matched and well correlated with c using an 18-year full conductivity–temperature–depth (CTD) dataset (N = 1,345, R2 = 0.93). In the second step, c was synchronously matched and well correlated with GOCI Rrs band ratios using an 8-year summer CTD dataset (N = 391, R2 = 0.93). The satellite-derived surface salinity based on the GOCI was compared with five other approaches and validated using an 8-year summer CTD dataset (2011–2018, N = 707, RMSE = 0.43, bias = 0.053, mean ratio = 1.002). We mapped satellite-derived surface salinity using monthly GOCI images during the summer from 2011 to 2020. The spatial patterns of the CDW were connected to the Changjiang River mouth and extended to the east–northeast during summer. Saline water was confined to the warm current and the upper slope in the eastern part of the study area. Anomalous dispersion of the CDW occurred in August 2016, 2017, and 2020, and limited dispersion occurred in August 2014 and 2019.

Mercury photoreduction and photooxidation kinetics in estuarine water: Effects of salinity and dissolved organic matter

Net photoreduction of divalent mercury (Hg(II)) and volatilization of photoreduction products (i.e., elemental mercury (Hg(0))/dissolved gaseous mercury (DGM)) is a mechanism by which mercury burdens in ecosystems are lessened. The effects of salinity on mercury photoreactions were investigated while controlling the concentration of DOM (>1 kDa) using natural surface water from the tidal Jijuktu'kwejk (Cornwallis River) and processed with a tangential ultrafiltration-dilution technique. Pseudo first-order rate constants in estuarine water salinity dilutions ranged between 0.22 h−1 and 0.73 h−1. The amount of mercury available for photoreduction (Hg(II)RED) ranged between 67.2 and 265.9 pg. Pseudo first-order rate constants decreased with increasing salinity treatments (0–13.5 g L−1), with minimal change in rate constants occurring in higher salinity treatments (e.g. 20.3 or 26.8 g L−1), while Hg(II)RED increased with salinity. In lower salinity treatments, DOM was more photoactive. Taken together, results suggest changes in the mercury photoreduction mechanism from DOM-bound electron transfer to photochemically produced secondary reduction products with increasing salinity. Experiments examining photooxidation showed decreases in Hg (0) with longer exposure time, suggesting transformation of Hg(II)RED into a non-reducible form. This research highlights the importance of salinity and DOM interactions in estuarine surface water and their effects on mercury photochemistry.

Estuary boundary based on waters surface salinity in cimandiri estuary and cisadane estuary, indonesia.

Estuary is an exclusive system and have an important role but also have vulnerabilities that can threaten life in the estuary region, so it is necessary to have knowledge of estuarine boundaries so that conservation can be maintained. This study aims to analyze the boundaries of the Cimandiri Estuary and the Cisadane Estuary based on surface water salinity, and analyze the relationship of estuarine surface water salinity with rainfall, sea surface currents and tides in the Cimandiri Estuary and Cisadane Estuary. The variables used in this study are salinity, rainfall, sea surface currents, and tides. The research method use the Cimandiri Algorithm by processing OLI Landsat 8 Imagery in 2018 and 2019. The results of this study are estuary boundaries divided into 3 estuary boundary classes specifically Mexo-oligohaline (0.5-5 ‰), Mexo-mesohaline (5-18 ‰), and Mexo-polyhaline (18-30 ‰). Cimandiri’s salinity value is strongly affected by season, then by tides and last by the currents, it is because the Cimandiri Estuary has a deep waters. Meanwhile in the Cisadane Estuary, the salinity value is strongly influenced by season, then by the currents and tides, and also influenced by freshwater from land, it is because the Cisadane Estuary has a shallow water.

Hydrogeochemical processes controlling the salinity of surface water and groundwater in an inland saline-alkali wetland in western Jilin, China

Understanding the hydrochemical evolutionary mechanisms of surface water and groundwater in saline-alkali wetlands in arid and semi-arid regions is necessary for assessing how wetland water resource utilization and restoration processes may affect the natural interface between wetland salinity and water. The Momoge National Nature Reserve (MNNR) is an inland wetland in northeastern China that is mainly fed by irrigation water and floods from the Nenjiang River. The purpose of the present study is to describe the spatial distribution characteristics of surface water and groundwater hydrochemistry and salinity in the MNNR and analyze the main processes controlling these parameters. The composition of stable isotopes (δ2H and δ18O) and water chemistry, including the levels of Na, K, Ca, Mg, HCO3, SO4, and Cl, of 156 water samples were analyzed. The results show that the lake water in the MNNR is at a risk of salinization owing to a high degree of evaporation. The analysis of the ion ratio and mineral saturation index showed that the ions in water are primarily derived from aquifer leaching, and the precipitation of Ca2+ and Mg2+ resulted in lower Ca2+ and Mg2+ levels in lake water than in groundwater. Hydrogen and oxygen stable isotope and deuterium excess analyses show that evaporation is the dominant factor controlling the hydrochemistry and salinity of lake water in the MNNR. Long-term effective monitoring of lake water and groundwater must be developed to provide an early warning for the salinization of lake water and a scientific basis for the protection and restoration of wetland ecosystem functions within the MNNR.

Irrigation water quality in the Salinas-MG region, Brazil

This study aimed to evaluate the risk of salinity and sodicity of surface and underground water used for irrigation purposes on rural properties in the municipality of Salinas/MG, Brazil. The water samples were collected at a catchment point used by irrigators, and the physical-chemical parameters evaluated were: pH, sodium (Na) content, calcium (Ca) content, magnesium (Mg) content, electrical conductivity (CE), and sodium adsorption ratio (SAR). The latter was calculated to classify water as a function of risk of salinity and soil sodification. Groundwater was rated as class C3 (high salinity) while surface water as C1 (low salinity). As for soil sodification risk, groundwater was moderate, while the other samples were severe.

The Atlantic Ocean landscape: A basin-wide cluster analysis of the Atlantic near seafloor environment

Landscape maps based on multivariate cluster analyses provide an objective and comprehensive view on the (marine) environment. They can hence support decision making regarding sustainable ocean resource handling and protection schemes. Across a large number of scales, input parameters and classification methods, numerous studies categorize the ocean into seascapes, hydro-morphological provinces or clusters. Many of them are regional, however, while only a few are on a basin scale. This study presents an automated cluster analysis of the entire Atlantic seafloor environment, based on eight global datasets and their derivatives: Bathymetry, slope, terrain ruggedness index, topographic position index, sediment thickness, POC flux, salinity, dissolved oxygen, temperature, current velocity, and phytoplankton abundance in surface waters along with seasonal variabilities. As a result, we obtained nine seabed areas (SBAs) that portray the Atlantic seafloor. Some SBAs have a clear geological and geomorphological nature, while others are defined by a mixture of terrain and water body characteristics. The majority of the SBAs, especially those covering the deep ocean areas, are coherent and show little seasonal and hydrographic variation, whereas other, nearshore SBAs, are smaller sized and dominated by high seasonal changes. To demonstrate the potential use of the marine landscape map for marine spatial planning purposes, we mapped out local SBA diversity using the patch richness index developed in landscape ecology. It identifies areas of high landscape diversity, and is a practical way of defining potential areas of interest, e.g. for designation as protected areas, or for further research. Clustering probabilities are highest (100%) in the center of SBA patches and decrease towards the edges (< 98%). On the SBA point cloud which was reduced for probabilities <98%, we ran a diversity analysis to identify and highlight regions that have a high number of different SBAs per area, indicating the use of such analyses to automatically find potentially delicate areas. We found that some of the highlights are already within existing EBSAs, but the majority is yet unexplored.

The novel mangrove environment and composition of the Amazon Delta

Both freshwater floodplain (várzeas and igapós) forests and brackish-saline mangroves are abundant and well-described ecosystems in Brazil.1 However, an interesting and unique wetland forest exists in the Amazon Delta where extensive mangroves occur in essentially freshwater tidal environments. Unlike the floodplain forests found upriver, the hydrology of these ecosystems is driven largely by large macro-tides of 4-8m coupled with the significant freshwater discharge from the Amazon River. We explored these mangroves on the Amazon Delta (00°52' N to 01°41' N) and found surface water salinity to be consistently <5; soil pore water salinity in these mangrove forests ranged from 0 nearest the Amazon mouth to only 5-11 at the coastal margins to the north (01°41' N, 49°55' W). We also recorded a unique mix of mangrove-obligate (Avicennia sp., Rhizophora mangle) and facultative-wetland species (Mauritia flexuosa, Pterocarpus sp.) dominating these forests. This unique mix of plant species and soil porewater chemistry exists even along the coastal strands and active coastlines of the Atlantic Ocean. Part of these unique mangroves have escaped current global satellite mapping efforts, and we estimate that they may add over 180km2 (20% increase in mangrove area) within the Amazon Delta. Despite having a unique structure and function, these freshwater-brackish ecosystems likely provide similar ecosystem services to most mangroves worldwide, such as sequestering large quantities of organic carbon, protection of shoreline ecosystems from erosion, and habitats to many terrestrial and aquatic species (monkeys, birds, crabs, and fish).

Multifaceted Assessment of Wastewater-Based Epidemiology for SARS-CoV-2 in Selected Urban Communities in Davao City, Philippines: A Pilot Study.

Over 60 countries have integrated wastewater-based epidemiology (WBE) in their COVID-19 surveillance programs, focusing on wastewater treatment plants (WWTP). In this paper, we piloted the assessment of SARS-CoV-2 WBE as a complementary public health surveillance method in susceptible communities in a highly urbanized city without WWTP in the Philippines by exploring the extraction and detection methods, evaluating the contribution of physico-chemical–anthropogenic factors, and attempting whole-genome sequencing (WGS). Weekly wastewater samples were collected from sewer pipes or creeks in six communities with moderate-to-high risk of COVID-19 transmission, as categorized by the City Government of Davao from November to December 2020. Physico-chemical properties of the wastewater and anthropogenic conditions of the sites were noted. Samples were concentrated using a PEG-NaCl precipitation method and analyzed by RT-PCR to detect the SARS-CoV-2 N, RdRP, and E genes. A subset of nine samples were subjected to WGS using the Minion sequencing platform. SARS-CoV-2 RNA was detected in twenty-two samples (91.7%) regardless of the presence of new cases. Cycle threshold values correlated with RNA concentration and attack rate. The lack of a sewershed map in the sampled areas highlights the need to integrate this in the WBE planning. A combined analysis of wastewater physico-chemical parameters such as flow rate, surface water temperature, salinity, dissolved oxygen, and total dissolved solids provided insights on the ideal sampling location, time, and method for WBE, and their impact on RNA recovery. The contribution of fecal matter in the wastewater may also be assessed through the coliform count and in the context of anthropogenic conditions in the area. Finally, our attempt on WGS detected single-nucleotide polymorphisms (SNPs) in wastewater which included clinically reported and newly identified mutations in the Philippines. This exploratory report provides a contextualized framework for applying WBE surveillance in low-sanitation areas.

Salinity impacts on irrigation water-scarcity in food bowl regions of the US and Australia

Irrigation water use and crop production may be severely limited by both water shortages and increased salinity levels. However, impacts of crop-specific salinity limitations on irrigation water scarcity are largely unknown. We develop a salinity-inclusive water scarcity framework for the irrigation sector, accounting for crop-specific irrigation water demands and salinity tolerance levels and apply it to 29 sub-basins within two food bowl regions; the Central Valley (CV) (California) and the Murray–Darling basin (MDB) (Australia). Our results show that severe water scarcity (levels >0.4) occurs in 23% and 66% of all instances (from >17 000 monthly crop-specific estimates) for the CV and MDB, respectively. The highest water scarcity levels for both regions occurred during their summer seasons. Including salinity and crop-specific salinity tolerance levels further increased water scarcity levels, compared to estimations based on water quantity only, particularly at local sub-basin scales. We further investigate the potential of alleviating water scarcity through diluting surface water with lower saline groundwater resources, at instances where crop salinity tolerance levels are exceeded (conjunctive water use). Results from the CV highlights that conjunctive water use can reduce severe water scarcity levels by up to 67% (from 946 monthly instances where surface water salinity tolerance levels were exceeded). However, groundwater dilution requirements frequently exceed renewable groundwater rates, posing additional risks for groundwater depletion in several sub-basins. By capturing the dynamics of both crops, salinity and conjunctive water use, our framework can support local-regional agricultural and water management impacts, on water scarcity levels.

Determination of Marine Biotoxins Contamination Level of Mussel (Perna Perna) (Linne, 1758) from the Mamelles Bay, Dakar

This study evaluating marine biotoxins contamination level of mussel ( Perna Perna ) in the Mamelles Bay (Ouakam) of Dakar is the first report in Senegal. It took place over one year (from March 2018 to February 2019). Liquid chromatography with mass spectrometry (LC-MS-MS) reference method (Regulation (EC) 15/2011 of 10 January 2011) was used to quantify marine biotoxins. Okadaic acid (OA) and its esters are the most problematic of all the researched biotoxins. They are present throughout most of the year, except September and November, with an average monthly concentration of 163 µg/kg, slightly above the regulatory limit (160 µg/kg). The sanitary status of the mussel shows two peaks of contamination, the first of which occurs in the rainy season (August) and the second in the cold season (December), with values equal to 654 and 802 µg/kg respectively 4 to 5 times higher than the regulatory threshold set by Regulation (EC) No 853/2004 of 29 April 2004 supplemented by Regulation (EU) No 786/2013 amending its Annex III and Senegalese Order No 07951 of 12 May 2017. These two peaks coincide with (i) the wintering period, marked by continental land-based inputs due to rainwater runoff, but also with the temperature rise, or (ii) the cold period with the appearance of upwelling (upwelling of cold water, rich in nutrient salts). In addition to the chemical analyses carried out on the mussel, the research work on phytoplankton and the surveys of physicochemical parameters carried out on the water at the collection site show (i) the existence of toxic algae of the Dinophysis genus and Gambierdiscus , in June, i.e., one to two months before the first peak of contamination of the Perna perna by AO; (ii) also a coincidence between the appearance of these phenomena and variations in surface water temperature and salinity, which are determining factors in the appearance and development of harmful algal blooms. Concerning the other biotoxins investigated, in particular AZA and yessotoxins, it was noted that AZA was absent throughout the year, unlike yessotoxins, which were found in the flesh of Perna perna at concentrations below the regulatory limit set at 3750 µg/kg. The maximum being 51 µg/kg obtained in June, i.e., 73 times lower than the regulatory threshold. In the light of the results obtained, it appears that the periods of high contamination are the winter period and the upwelling period, which could lead to closure measures to guarantee the safety of the mussels. It would be interesting to extend the study to all other bivalve mollusks and gastropods, to carry out an inventory and quantify the toxic microalgae present in the water. To this end, the effectiveness of purification techniques would be tested. Keywords: Mussel ( Perna perna ), Marine biotoxins, Toxic microalgae, Mamelles, Dakar. DOI: 10.7176/FSQM/117-04 Publication date: July 31 st 2022

Application of random forest for modelling of surface water salinity

Modeling surface water quality using artificial intelligence-based models is essential in projecting suitable mitigation measures. However, it remains a challenge and requires further research to enhance the modeling accuracy. For this aim, this article presents a methodology to optimize the modeling inputs and reduce the associated complexity. The proposed approach employs Random Forest for modeling surface water salinity in terms of electrical conductivity (EC) and total dissolved solids (TDS) in the upper Indus River basin, one of the major rivers in Asia. Various water quality parameters measured monthly over a historical 30-year period were utilized in the modeling process. Various statistical indicators were used to evaluate the model performance. Random Forest process is suitable technique to simulate the salinity of surface water bodies, and effective tool in minimizing the modeling complexity and elaborating proper management and mitigation measures.

Determining the Effectiveness of Street Cleaning with the Use of Decision Analysis and Research on the Reduction in Chloride in Waste

Waste from street cleaning is usually of a fine fraction below 10 mm and varies greatly in both quantity and composition. It may be composed of chlorides, especially for that resulting during winter due to the use of street de-icing agents. Chlorides can cause the salinization of surface water and groundwater, and the salinization of soils, which in turn lead to the deterioration of water purity and a decrease in biodiversity of aquatic organisms, changes in microbiological structure, and increases in toxicity of metals. Therefore, it is very important to determine the level of salinity in stored waste and its impact on the environment. The present study was conducted in a city of about 55,000 inhabitants. The highest chloride concentrations were observed after winter in waste from street and sidewalk cleaning around the sewer gullies, amounting to 1468 mg/dm3. The lowest chloride concentration in this waste occurred in summer and amounted to 35 mg/dm3. The multi-criteria analysis indicated that the most beneficial form of street cleaning and, thus, of reductions in chloride concentration in the waste from street cleaning, would be sweeping and daily washing. The objective of this research was to determine the amount of chlorides in sweepings on an annual basis in order to determine the potential risks associated with their impact on select aspects of the environment and to evaluate the frequency of necessary cleaning for city streets, considering the effects. The methodology used was a multi-criteria evaluation, which as a decision analysis, allowed us to determine the frequency of cleaning and washing of streets, in such a way that an ecological effect is achieved with simultaneous economic efficiency.