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Although salinity satellites can provide high-resolution global sea surface salinity (SSS) data, the satellite data still display large errors close to the coast. In this paper, a nonlinear empirical method based on random forest is proposed to correct two Soil Moisture and Ocean Salinity (SMOS) L3 products in the tropical Indian Ocean, including SMOS BEC and SMOS CATDS data. The agreement between in-situ data and the corrected SMOS data is better than that between in-situ data and the original satellite data. The root-mean-square deviation (RMSD) of the satellite SSS data decreased from 0.366 to 0.275 and from 0.367 to 0.255 for SMOS BEC and SMOS CATDS, respectively. The effect of the correction model was better in the Arabian Sea than in the Bay of Bengal. The RMSD of corrected BEC (CATDS) SSS was reduced from 0.44 (0.48) to 0.276 (0.269), and the correlation coefficient was increased to 0.915 from 0.741(0.801) in the Arabian Sea while the correlation coefficient improved less than 0.02 in the Bay of Bengal. The cross-validation results highlight the robustness and effectiveness of the correction model. Additionally, the effects of different features on the correction model are discussed to demonstrate the vital role of geographical information in the correction of satellite SSS data. The proposed method outperformed other machine-learning methods with respect to the RMSD and correlation coefficient.

In order to know the efficiency of sterilization in eliminating parasites and its suitability for environment measurements, samples of the water and sediments was taken from six stations the Euphrates River. The samples were transported in clean and sterile bottles to the laboratory. A sedimentation method was used for parasites. Ten species of parasites isolated from water of the six stations while isolated seven were exists in the sediments of these stations. The water and sediments of the station first were contaminate with parasites rate 25.8% and 13.7%, the water and sediments of the second station are contaminated with parasites rate 12.8% and 20.2%, the water and sediments of the third station are contaminated with parasites rate 4.2% and 18.2%, the water and sediments of the fourth station are contaminated with parasites rate 22.8% and 18%, the water and sediments of the fifth station are contaminated with parasites rate 12.0% and 5.4% and the water and sediments of the sixth station are contaminated with parasites rate 12.9% and 1.7%. Giardia lamblia rate 25.4% it is most found in water while Trichomonas hominis rate 18.4% It is most found in sediments. A result of the study shows significant difference between of the temperature of air and water in all study stations, the air temperature ranged (40.10–15.2°C) and the water temperature between (26.3–9.4°C) while PH was (9.89–7.5), recorded electrical conductivity (5745–2515 μs/cm) and salinity was (4.80–1.56 g/cm) the river's water was of low salinity also dissolved oxygen was (12.9–6.2 mg/L). Date seed used as granular by activated carbon used for purification and remove parasite from water filter and waste water treatment.

This paper explores the transient upward flow of saline water in one-dimensional soil and soil–geosynthetics columns to evaluate preventive measures to mitigate salinity rise. Unsaturated soil concepts are utilised to elucidate the salinity movement through geotextile and geocomposite drain interfaces. The presence of a geotextile layer slowed down the capillary rise of the saline water. However, it did not prevent the breakthrough of the saline water due to the hydrophilicity of the geotextile and the suction at the geotextile base being close to the geotextile's water entry suction value. In contrast, using a geocomposite drain mitigated the upward saline wetting front. It acted as a salinity capillary barrier due to the initial hydrophobicity of its geotextile component and the air gap present in the geonet core.

The quality of the groundwater in the study area was evaluated through various water quality indexes for drinking and irrigation purposes. To evaluate the water quality index, 186 groundwater samples were sampled during 2 different seasons, likely pre-monsoon (PRM) and post-monsoon (POM). The collected samples were measured for physical-chemical parameters like pH, EC, TDS, Na, K, Ca, Mg, Cl, HCO3, PO4, SO4, NO3 and H4SiO4. The research findings indicated that groundwater of the study area is approaching an alarming stage of its suitability for drinking purpose because a major percentage (i. e. 56%: PRM, 46%: POM) of samples are within poor category. Thus, the proper management strategy for water resources must be developed and a preventive management practice to address this issue must be implemented. Various water quality parameters such as electrical conductivity (EC), pH, salinity hazard, sodium hazard and permeability indexes (PI) were considered for irrigation water quality evaluation and it is inferred that the groundwater of the study area is suitable for irrigation. The PRM and POM samples with higher Na + and Cl concentrations were identified. The primary source of groundwater contamination is anthropogenic factors like domestic, agriculture effluents and mining activities. However, the groundwater of these regions is also greatly influenced by geogenic factors like weathering, rock-water interaction and precipitation which results in groundwater water level fluctuation. The research findings suggest the groundwater quality of this region is approaching an alarming stage for drinking purposes. Thus, developing a management strategy for drinking water sources and implementing preventive management practices to address this issue becomes imperative.

The Gulf of Riga is a relatively shallow bay connected to the deeper central Baltic Sea (Baltic Proper) via straits with sills. The decrease in the near-bottom oxygen levels from spring to autumn is a common feature in the gulf, but in 2018, extensive hypoxia was observed. We analyzed temperature, salinity, oxygen, and nutrient data collected in 2018, along with historical data available from environmental databases. Meteorological and hydrological data from the study year were compared with their long-term means and variability. We suggest that pronounced oxygen depletion occurred in 2018 due to a distinct development of vertical stratification. Seasonal stratification developed early and was stronger in spring–summer 2018 than on average due to high heat flux and weak winds. Dominating northeasterly winds in early spring and summer supported the inflow of saltier waters from the Baltic Proper that created an additional deep pycnocline restricting vertical transport between the near-bottom layer (NBL) and the water column above. The estimated oxygen consumption rate in the NBL in spring–summer 2018 was about 1.7 mmolO2m-2h-1, which exceeded the oxygen input to the NBL due to advection and vertical mixing. Such a consumption rate leads to near-bottom hypoxia in all years when vertical mixing in autumn reaches the seabed later than on average according to the long-term (1979–2018) meteorological conditions. The observed increase in phosphate concentrations in the NBL in summer 2018 suggests a significant sediment phosphorus release in hypoxic conditions counteracting the mitigation measures to combat eutrophication. Since climate change projections predict that meteorological conditions comparable to those in 2018 will occur more frequently, extensive hypoxia would be more common in the Gulf of Riga and other coastal basins with similar morphology and human-induced elevated input of nutrients.

Irrigated agriculture has been in a quandary of sustaining its productivity for centuries while attempting to cope with soil and water salinity issues that continue to devastate crop yields. Several of the research gaps associated with current irrigation methods include how to assess leaching requirements and efficiency for different soils, crops, and irrigation regimes. The objective of this project was to test water application methods on salinity leaching efficacy. Three soils of different textures (clay, loam, and sandy soils) were collected from fields. The soils were air-dried and sieved (1.7 mm) and were used to pack the soil columns (10-cm dia. and 30-cm height) for the leaching experiments. Treatments of the column experiments included continuous ponding, intermittent ponding, and unsaturated water application with three replicates per treatment using the three soils. Furthermore, the HYDRUS 1D model was used to analyze the experimental data and to evaluate the leaching efficiency under different irrigation schemes. Our results showed that intermittent ponding was the most effective water application method for salinity leaching in the loamy soil, and that the unsaturated water application was the most effective water application method for salinity leaching in the clay soil by achieving 75% salt removal out of the columns using the least amount of water. The sandy soil had no difference in leaching efficiency among water application methods, therefore continuous ponding is recommended if time is not a limiting factor in water supply. The findings from this research will allow farmers to improve their water management practices and reduce groundwater contamination from excessive irrigation.

This study explores the differences of fish assemblages in three macrotidal estuaries of Man-gyeong River Estuary (MRE), Geum River Estuary (GRE), and Han River Esturay (HRE) with similar ranges of seasonal water temperature that are diked with different levels of disconnection from freshwater discharge. The distribution of major species in the three estuaries could generally be grouped into three distinctive patterns based on their cumulative distribution with respect to the salinity gradient. The MRE was geographically closer to the GRE than to the HRE, but the fish community of the MRE more closely resembled that of the HRE. Increased freshness of the water inside the dike and the limit of coastal fish to the river may have led to this result. The results provide clues to how enclosure patterns of estuarine waters could affect fish communities over a long-term period. In addition, the information may provide guidance for how a fish community may return once environmental conditions are restored.

Water depth, salinity, current, and suspended sediment concentration (SSC) were measured along with the grain size distribution of bed sediment along an estuarine longitudinal section. The floc size increased with increase in the percentage of clay and silt, while decreased with increase in the percentage of sand content of bed sediment. The turbulent shear, G, had a direct effect on floc size with its value increasing with increase in G up to a G value of 15 s−1, while an inverse relation existed between floc size and G at higher G (G > 15 s−1). Further, higher turbulence enabled sand to get resuspended and cause additional shear leading to the break-up of flocs. An attempt was made to modify G to account for the combined effect of water turbulence (G) and shear imparted by sand (Ga) and the impact of the modification of G on the predictability of floc size was evaluated. A new model was developed which explains floc size in terms of sediment concentration (C), salinity gradient (S), and G for different scenarios based on the value of G. Sensitivity analysis was done for observed floc size (FS) and predicted floc size using four approaches: (I) FS α Cx; (II) FS α CxS-y; (III) FS α CxS–yGz for G 15 s−1; and (IV) FS α CxS–yGm–z for G > 15 s−1 and Gm = G + Ga, where x, y, and z are determined by calibration. It was observed that the predictability of the floc size improved when the turbulence was modified to account for shear imparted by sand so that the coefficient of determination was increased from 0.78 for model III to 0.89 for model IV. Further, the settling velocity was expressed as a function of suspended sediment concentration, turbulent shear, and salinity gradient. The predictability of settling velocity was improved (R2 increased from 0.77 to 0.86) when the additional turbulence created by sand was incorporated in the non-dimensional empirical equation. The study highlights the influence of sand in causing the break-up of flocs and suggests that for turbulence shear values high enough to resuspend sand, and G has to be modified to account for the additional shear imparted by sand in mixed sediment estuarine environments.

In mangrove forests, soil salinity is one of the most significant environmental factors determining mangrove forest distribution and productivity as it limits plant water uptake and carbon gain. However, salinity control on mangrove productivity through plant hydraulics has not been investigated by existing mangrove models. Thus, we present a new individual-based model linked with plant hydraulics to incorporate physiological characterization of mangrove growth under salt stress. Plant hydraulics was associated with mangroves nutrient uptake and biomass allocation apart from water flux and carbon gain. The developed model was performed for two-coexisting species of Rhizophora stylosa and Bruguiera gymnorrhiza in a subtropical mangrove forest in Japan. The model predicted that the productivity of both species was affected by soil salinity through downregulation of stomatal conductance, while B. gymnorrhiza trees grow faster and suppress the growth of R. stylosa trees by shading that resulted in a B. gymnorrhiza-dominated forest under low soil salinity conditions (B. gymnorrhiza compared to R. stylosa, leading to an increase in biomass of R. stylosa despite the enhanced salt stress (> 30 ‰). These predicted patterns in forest structures across soil salinity gradient remarkably agreed with field data, highlighting the control of salinity on productivity and tree competition as factors that shape the mangrove forest structures. The model reproducibility of forest structures was also supported by the predicted self-thinning processes, which likewise agreed with field data. In addition, the mangroves morphological adjustment to increasing soil salinity – by decreasing transpiration and increasing hydraulic conductance – was reasonably predicted. Aside from the soil salinity, seasonal dynamics in atmospheric variables (solar radiation and temperature) was highlighted as factors influencing mangrove productivity in a subtropical region. The physiological principle-based improved model has the potential to be extended to other mangrove forests in various environmental settings, thus contributing to a better understanding of mangrove dynamics under future global climate change.

Tremendous benefits of biochar (BC) amendment to soil have been reported, including their role in alleviating the impact of salinity stress in plants. The aim of this study was to evaluate the effects of BC produced at 300 °C (BC300) and 700 °C (BC700) on the germination rate (GR) and selected growth characteristics of corn plants irrigated with salinized water over a growth period of 6 weeks. The experimental treatments included three biochar treatments: BC0 (control, without biochar addition), BC300, and BC700. The treatments also included three salinity levels of irrigation water: 0, 3, and 6 dS·m−1. The biochar was applied at a rate of 3%. The GR decreased with increasing salinity level, which was more evident in the first week. This stress impact was reduced when treated with the BC700 relative to the saline treatments without BC. Both BC treatments demonstrated contrasting effects on corn growth, nutrient uptake, and Na+ and K+ content in plant tissue. The effect of BC700 treatment on plant height and root length was limited, but the impact of salinity stress on chlorophyll meter readings, chlorophyll fluorescence parameter (Fv/Fm), dry matter yield, and N and P uptake were largely mitigated. It also increased K+ and decreased Na+ content in plant tissue. However, the BC300 treatment adversely affected plant growth parameters at each salinity level. Overall, the BC produced at a higher temperature significantly alleviated the impact of salinity stress on plant growth characteristics, which is probably attributed to their higher surface area and porosity, enhancing their salt ion sorption capacity.

In the last decade, there has been an increasing interest in understanding the effects of changing injected water salinity on the performance of oil reservoirs. This paper aims to investigate the effects of injected water salinity on oil recovery of an Egyptian oil reservoir (Bahariya formation). An experimental work program has been performed using 25 core plugs and 5 different water salinities to study the effects of changing water salinity during both secondary and tertiary stages of waterflooding. The objectives of the experimental work were to (1) investigate the effects of the low water salinity on oil recovery and (2) identify the optimum water salinity and the main reservoir parameters for application of low salinity waterflooding project (LSWF) in Bahariya formation. The results revealed that there is an optimum salinity for waterflooding in the secondary flooding stage. However, for the tertiary flooding stage, the results showed that the controlling factor is not decreasing the salinity, but rather changing the salinity (e.g. either increasing or decreasing). It was also clear that applying the optimum salinity in the secondary recovery stage is more effective than applying it in the tertiary recovery stage. Furthermore, the results showed that the positive impact of LSWF may be expected in reservoirs with high amount of kaolinite, high values of CEC, and low amounts of plagioclase feldspar. This study is an original contribution to develop guidelines for designing optimum salinity waterflooding projects in sandstone reservoirs.

Climate change and sea level rise are causing an increase in salinity in coastal salt marshes around the world. These changes may alter the germination dynamics of some halophytes, threatening their conservation. Our study area (Atlantic coast of the southwestern Iberian Peninsula) is currently being affected by sea level rise, and increases in sediment salinity have been recorded. We studied the germination responses during and after a wide range of imposed salinities (0-600 mM) of 5 Asteraceae species; 3 colonizing salt marshes (Artemisia caerulescens, Aster tripolium and Inula crithmoides) and 2 (Dittrichia spp.) inhabiting adjacent non-tidal environments. In addition, habitat characteristics (plant cover, sediment redox potential, electrical conductivity, pH, water content and bulk density) associated with each marsh species were measured and compared with the spatial distribution of the Asteraceae species in the field and their capacity to germinate at different salinities. The germination syndrome of Aster tripolium and Inula crithmoides was characterized as germinating in salinity ranging from fresh water to 600 mM salinity (36 ppt). The rare halophyte A. caerulescens and the 2 non-tidal Dittrichia species presented a germination syndrome based on no germination at high salinities and high recovery germination (55-80%). Considering the high sensitivity of A. caerulescens to salinity during germination, active conservation measures are recommended to promote its preservation in the Mediterranean Basin. These include creating new populations and promoting salt marsh connectivity to facilitate the processes of species mobility and marsh migration to uplands where sediment salinity is lower.

The continuous use of brackish groundwater for irrigation is detrimental for soil and crop attributes. A three-year research study was designed for the wheat crop to assess the effects of brackish groundwater on crop yield and soil health under a surface irrigation system. Three sites were selected in different cropping zones of Pakistan. The treatments comprised of irrigation with moderately brackish water having 0.8, 1.3 & 2.7 dSm−1 of salinity and canal water. The results indicated that EC, SAR, bicarbonates, Ca2+ and Mg2+ levels increased in the soil for consecutive years and this increase was more at site S3 followed by S2 and S1. As soil depth is concerned, the increase was more pronounced in upper layers of soil (0–15 cm) as compared to 15–30 cm depth. Growth and yield were also affected by the consecutive use of this water, the number of plants, plant height, the number of spikes per plant, and yield was reduced at all the three sites. However, the impact was less pronounced at the site S1 whereas S3 was the most affected one. Grain weight and dry matter weight were observed to be maximum at S1. Water productivity was also calculated for all the three sites. Maximum water productivity was observed at S1 followed by S2 & S3. It was concluded that the continuous use of brackish water would have an adverse effect on crop yield and subsequently, soil health is also affected by it significantly.

Soil microbial communities perform vital ecosystem functions, such as the decomposition of organic matter to provide plant nutrition. However, despite the functional importance of soil microorganisms, attribution of ecosystem function to particular constituents of the microbial community has been impeded by a lack of information linking microbial function to community composition and structure. Here, we propose a function-first framework to predict how microbial communities influence ecosystem functions. We first view the microbial community associated with a specific function as a whole and describe the dependence of microbial functions on environmental factors (e.g., the intrinsic temperature dependence of bacterial growth rates). This step defines the aggregate functional response curve of the community. Second, the contribution of the whole community to ecosystem function can be predicted, by combining the functional response curve with current environmental conditions. Functional response curves can then be linked with taxonomic data in order to identify sets of “biomarker” taxa that signal how microbial communities regulate ecosystem functions. Ultimately, such indicator taxa may be used as a diagnostic tool, enabling predictions of ecosystem function from community composition. In this paper, we provide three examples to illustrate the proposed framework, whereby the dependence of bacterial growth on environmental factors, including temperature, pH, and salinity, is defined as the functional response curve used to interlink soil bacterial community structure and function. Applying this framework will make it possible to predict ecosystem functions directly from microbial community composition.

17 pages, 13 figures, 1 table.-- Data availability: The product (Martínez et al., 2019) is freely distributed on the BEC (Barcelona Expert Center) web page (http://bec.icm.csic.es/, last access: 25 January 2022) with the DOI number https://doi.org/10.20350/digitalCSIC/12620 (Martínez et al., 2019) and on the Digital CSIC server: https://digital.csic.es/handle/10261/219679 (last access: 25 January 2022). Data can be downloaded from the FTP service: http://bec.icm.csic.es/bec-ftp-service/ (last access: 25 January 2022). The maps are distributed in the standard grid EASE-Grid 2.0, which has a spatial resolution of 25 km. In addition to the product validated in this work (L3 with temporal resolution of 9 d), L3 products having a temporal resolution of 3 and 18 d and the L2 product are available. These Arctic SSS products cover the period from 2011 to 2019.-- This work represents a contribution to the CSIC Thematic Interdisciplinary Platform PTI Teledetect and PolarCSIC. Argo data were collected and made freely available by the International Argo program and the national programs that contribute to it (https://argo.ucsd.edu, https://www.ocean-ops.org, last access: 25 January 2022). The Argo program is part of the Global Ocean Observing System, Measuring salinity from space is challenging since the sensitivity of the brightness temperature (TB) to sea surface salinity (SSS) is low (about 0.5 K psu−1), while the SSS range in the open ocean is narrow (about 5 psu, if river discharge areas are not considered). This translates into a high accuracy requirement of the radiometer (about 2–3 K). Moreover, the sensitivity of the TB to SSS at cold waters is even lower (0.3 K psu−1), making the retrieval of the SSS in the cold waters even more challenging. Due to this limitation, the ESA launched a specific initiative in 2019, the Arctic+Salinity project (AO/1-9158/18/I-BG), to produce an enhanced Arctic SSS product with better quality and resolution than the available products. This paper presents the methodologies used to produce the new enhanced Arctic SMOS SSS product (Martínez et al., 2019) . The product consists of 9 d averaged maps in an EASE 2.0 grid of 25 km. The product is freely distributed from the Barcelona Expert Center (BEC, http://bec.icm.csic.es/, last access: 25 January 2022) with the DOI number https://doi.org/10.20350/digitalCSIC/12620 (Martínez et al., 2019). The major change in this new product is its improvement of the effective spatial resolution that permits better monitoring of the mesoscale structures (larger than 50 km), which benefits the river discharge monitoring, This work has been carried out as part of the ESA Arctic+Salinity project (AO/1-9158/18/I-BG), which permitted the production of the database, and the Ministry of Economy and Competitiveness, Spain, through the National R&D Plan under L-BAND project ESP2017-89463-C3-1-R. [...] With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The Miandoab Plain has the largest water reserve in the province of West Azerbaijan, northwest Iran. Groundwater resources along with surface-water meet the needs of urban, industrial, and agricultural sectors, and therefore, their quality should be examined. Water quality indices are useful tools for aquifer management. In this research, the groundwater quality of the Miandoab Plain for agricultural purposes was investigated. For this purpose, the concentrations of the ions Mg2+, Ca2+, Na+, Hco3-, So42-, Cl- and the pH level were measured. The indices effective salinity and potential salinity as well as sodium adsorption ratio and electrical conductivity were analyzed to evaluate the salinity. The geostatistical analysis was performed using the GS+ software, and the zoning maps of salinity hazard were prepared using ArcGIS. To prepare the maps, EC, ES, PS, and SAR as well as Mg2+, Ca2+, Na+, Hco3-, So42, and Cl- were selected based on the semi-variogram values ​​and cross-validation technique. The Cl- map was considered as the basis for preparing the groundwater quality maps of the region. The results showed that the groundwater quality in the east of the plain is suitable, in the central part can be recommended under constant supervision, and in the west is unsuitable for agriculture. In other words, according to the geography of the plain, the recharge area is the low-risk part of the plain and the salinity hazard increases toward the discharge area. The results can pave the way for the relevant organizations to plan for the agricultural and environmental sectors.

Argo, an international, global observational array of nearly 4,000 autonomous robotic profiling floats, each measuring ocean temperature and salinity from 0 to 2,000 m on nominal 10-day cycles, has revolutionized physical oceanography. Argo started at the turn of the millennium, growing out of advances in float technology over the previous several decades. After two decades, with well over 2 million profiles made publicly available in real time, Argo data have underpinned more than 4,000 scientific publications and improved countless nowcasts, forecasts, and projections. We review a small subset of those accomplishments, such as elucidating remarkable zonal jets spanning the deep tropical Pacific; increasing understanding of ocean eddies and the roles of mixing in shaping water masses and circulation; illuminating interannual to decadal ocean variability; quantifying, in concert with satellite data, contributions of ocean warming and ice melting to sea level rise; improving coupled numerical weather predictions; and underpinning decadal climate forecasts. Expected final online publication date for the Annual Review of Marine Science, Volume 14 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

This study presents a paleolimnological and paleoclimatological reconstruction based on diatoms and phytoliths of four Pampean shallow lakes (from south to north, La Salada, Sauce Grande, Los Chilenos, and Puan) strategically located along a climatic gradient from arid (south) to semiarid conditions (north). This research aims to identify the main drivers and mechanisms of long-term ecological change, and the main climatic mechanisms behind the regional hydroclimatic variability. It was found that these lakes were initially temporary, with clear waters, and eventually, became permanent with turbid waters. We propose that this change is due to an increase in precipitation in the last ca 1000 years, which resulted in higher lake levels and an increase in surface area, leading to an increased fetch and subsequent resuspension of sediment. This climatic amelioration occurred after ∼910 cal yr BP, first in what is today the arid Pampean region, then in the semiarid region, and finally in the modern humid region at ∼ -9 cal yr BP (1959 CE). Variations in lake's water level were the main driver of ecological change, followed by salinity (in Puan and La Salada) and nutrient load (in Los Chilenos and Sauce Grande). In general, those lakes on the southwest, located closer to the limit of moisture influence originating in the Pacific and Atlantic oceans (Arid Diagonal) were more sensitive to hydroclimatic changes than those located in the central Pampean region.

In the present study, 6 water and 16 sediment samples were collected from Hashilan Wetland (Kermanshah Province, Iran) to specify physio-chemical properties of water and sediment and to evaluate the water pollution load with reference to the water physicochemical parameters. According to the Piper diagram, Ca2+–Mg2+–HCO3− hydrochemical facies is dominant due to calcium carbonate dissolution in the geological formations of the study area. The wetland water had a natural to slightly alkaline pH. Although TDS and EC of the water samples fall under freshwater category, their values were higher downstream of the wetland as a result of stagnant water, low water depth, more evaporation, and impact of agricultural runoff. Based on the water quality index (WQI), all water samples were ‘suitable’ for irrigation purposes, while 50% of the samples were ‘unsuitable’ for drinking. Comprehensive Pollution Index (CPI), and Sodium Adsorption Ratio (SAR) also indicated suitability of the wetland water for irrigation. According to the Wilcox diagram, salinity is higher downstream of the wetland due to introduction of agricultural runoff. It can be concluded that the wetland water could be used for irrigational purposes, but regular monitoring is recommended to promote sustainable use of natural resources and conserve the vulnerable aquatic ecosystem.

Submarine groundwater discharge (SGD) has received increasing attention by studies on coastal areas; however, its effects on biogeochemical zonation have not been investigated to date. The Yellow River Estuary (YRE) is a world class river estuary with high turbidity, and heavy human regulation. This study investigated how SGD is related to the benthic biogeochemistry of the YRE. Based on the distribution of several parameters (e.g., salinity, temperature, dissolved oxygen (DO) levels, pH, radium isotopes, and nutrients), the YRE was subdivided into six different zones, and the SGD fluxes within each zone were quantified and compared. The highest SGD flux was found in the northwest nearshore zone, where it was more than one order of magnitude higher than in the offshore zone. High SGD resulted in low DO and pH, but high nutrient levels in the benthic boundary layer. The southeast nearshore zone was also characterized by high SGD flux, but benthic waters were more oxic because of the dominating inputs by the Yellow River. These data suggest that such a zonation would help to understand benthic biogeochemical processes. High SGD may not only contribute to the estuarine nutrient budget, but may also contribute to the formation of hypoxia and acidification.

Tropical cyclone Amphan is the first super cyclone that happened in the north Indian Ocean in the last 20 years. In this work, multi-platform datasets were used to investigate the responses of the upper ocean to cyclone Amphan. The most striking response was the cold wake left by the cyclone spanning the entire Bay of Bengal with an amplitude up to ∼4°C. Satellite salinity observations revealed that the maximum increase in surface salinity was ∼1.5 PSU on the right side of the track of Amphan. Surface circulation was also observed to be modulated with the passage of a cyclone with a rightward bias in the change in its speed and direction. The currents observed from a moored buoy showed strong inertial oscillations. Argo observations showed that changes induced by the cyclone occurred up to 150 m depth of the cyclone and ocean heat content in the upper 150 m depth decreased due to the passage of the cyclone. There was an enhancement of surface chlorophyll concentration (∼1.5 mg/m3) after the passage of the cyclone, which was centred along the track of the cyclone where the winds were the highest. Mixed layer heat and salinity budget analysis showed that the sea surface cooling and increase in salinity was primarily driven by vertical mixing processes, though horizontal advection contributed meagrely. This study also brings forward the fact that regional differences exist in the responses of the ocean to the forcing of cyclones.

Passive microwave remote sensing of sea surface salinity from space is currently being done with measurements in the 27 MHz wide spectral window at 1.413 GHz (L-band) protected for passive use. Modern L-band instruments, such as the radiometers on Soil Moisture and Ocean Salinity (SMOS) and Aquarius, have demonstrated the feasibility of monitoring surface salinity from space, and they have also demonstrated the need for better accuracy, especially in cold water. Proposals to improve accuracy have largely involved adding measurement at more frequencies. For example, adding lower frequencies to improve the sensitivity to salinity in cold water and adding higher frequencies to enable simultaneous retrieval of sea surface temperature which is needed in the retrieval of salinity. These strategies involve tradeoffs, some obvious such as the effects of interference from anthropogenic sources of radio frequency radiation when operating outside the protected band and the loss of spatial resolution at lower frequencies. But, some are more subtle and arise because of the dependence of the retrieval of salinity on other parameters of the ocean surface, in particular, water temperature and roughness (wind speed). The effect of these interdependencies on the potential accuracy of salinity remote sensing in the frequency range 0.3-3.0 GHz is examined here to gain insight into the potential for future wide bandwidth instruments for remote sensing of salinity and the optimization of their design. There is benefit including the low frequencies, especially for cold water, but a danger of increased error including frequencies above 1.5-2.0 GHz depending on temperature.

The study adopts a number of soil salinity indices by applying geoinformatics techniques in the northeast of the Nile River Delta, based on the different spectral reflectance of soil salinity. The field investigation is carried out by collecting soil samples, and chemically analyzing them in order to compare them with the results of the indices (8 indices), relying on field review so as to capture images indicative of soil salinity and its impact on the land use that is most vulnerable to it, and this is vegetation. This is mainly for the sake of supporting the accuracy of the spectral resolution. It is found that each index relies on different variables of spectral reflectance. Accordingly, the study identifies the most appropriate and effective indices for assessing salinity, both spatially and temporally, in the northeast of the Nile River Delta. This is done through determining the highest degree of correlation between the results of the indices and the results of the chemical analysis of soil samples. Moreover, the study relies on the best indices in determining vegetation, which is EVI, so as to find out the degree to which the vegetation density is affected by soil salinity. This is carried out with the aim of coming up with results that help decision-makers in addressing the problems resulting from soil salinity with the least effort, the lowest cost, and the highest accuracy and realism. المستخلص باللغة العربية اعتمدت الدراسة عدد من أدلة ملوحة التربة عن طريق تطبيق تقنيات الجيوانفورماتيکس شمال شرق دلتا نهر النيل، مستندة على الانعکاسات الطيفية المختلفة لملوحة التربة. وتم التحقق الميداني عن طريق تجميع عينات من التربة وتحليلها کيميائيا، بغرض مقارنتها بنتائج الأدلة (8 مؤشرات)، مع الاعتماد على المراجعة الحقلية لالتقاط الصور المعبرة عن ملوحة التربة وأثارها على أکثر استخدامات الأرض حساسية لها وهو الغطاء النباتي، وذلک لتدعيم دقة التمييز الطيفي. وقد تبين أن کل مؤشر يعتمد على متغيرات مختلفة من الانعکاسات الطيفية، ومن ثم لجأت الدراسة إلى تحديد أفضل المؤشرات المناسبة والفعالة في تقييم الملوحة زمانيا ومکانيا شمال شرق دلتا النيل، وذلک عن طريق تحديد أعلى درجة ارتباط بين نتائج المؤشرات ونتائج التحليل الکيميائي لعينات التربة، کما اعتمدت الدراسة على أفضل المؤشرات في تحديد الغطاء النباتي وهوEVI لمعرفة درجة تأثر کثافة الغطاء النباتي بملوحة التربة، وذلک بهدف الخروج بنتائج تساعد صناع القرار في معالجة المشاکل الناتجة عن ملوحة التربة بأقل جهد وأقل تکلفة وتکون أکثر دقة وواقعية.

Globally, the agricultural soils area where crop yields are affected by salinity has increased. This research aimed to evaluate the outcome of the edaphic application of mineral and organic amendments upon the growth and yield of irrigated rice in saline soils of Yaguachi, Ecuador. INIAP FL-1480 variety was selected for the experiment and grown with conventional cultural practices. A randomized complete block design with leonardite, gypsum, vinasse, compost, sugarcane filter cake, pig manure and control treatments, with four replicates, was used. Results indicated that application of compost was always associated with the highest accumulation of essential macronutrients in the rice grain, whereas no significant differences were found in leaves. Macronutrients were absorbed in the following sequence K = N > Ca > P > = S > Mg, while micronutrients Fe > Mn > Zn > Cu > B. While vegetative growth was not affected; reproductive growth was visibly influenced by the amendments application. Compost, sugarcane filter cake and leonardite induced superior yield values when compared to the control. Participant yield components with significant statistical differences were panicle-length, filled-grain-proportion and mainly a 1000-seed-weight. A non-significant mean harvest index of 0.35 and a grain-straw relationship of 0.65 were obtained for compost. Considering all the evaluations, the response to compost usage was always superior to or not exceeded by any other amendment, which leads to point it out as the best amendment for these soils, maybe because it favors plant soil nutrients availability. Response to amendments confirms their importance for rice crop management in the area.

A novel cycle model of the capacitive salinity/heat engine mainly consisting of nano-porous super-capacitors is established for harvesting mixed free energy caused by salinity difference between the river water and the seawater, and the thermal energy due to the temperature difference. The heat engine is charged and discharged in the cycle of a low temperature brine and a high temperature fresh water, respectively. The analytical expressions of the cyclic work output and efficiency are given. General performance characteristics of the capacitive salinity/heat engine are analyzed. The temperature of the heat reservoir and salt concentration of seawater are optimized to improve the efficiency of the capacitive salinity/heat engine. The optimal selection ranges of several main parameters are provided. When the Stern distance is equal to 1 nm and the charging voltage is equal to 3.5V, the energy conversion efficiency of the capacitive salinity/heat engine is about 40%, while the pure thermal efficiency in the cycle is about 16.9%. The energy conversion efficiency of the capacitive salinity/heat engine is significantly larger than that of the capacitive heat engine. The results obtained can facilitate the application of this technology to real life, which can reduce the consumption of fossil fuels.

The enzymatic pool of the soil is formed for a long time under the influence of many natural factors. Therefore, information on the lability of soil enzymes under the influence of the main abiotic factors is necessary for the diagnosis of the anthropogenic influence on ecosystems. The aim of the study was to determine the variability of the activity of catalase, invertase, and urease in sod-podzolic and grey forest soils in response to the main abiotic factors and model pollution. The studied areas belonged to the subzones of middle and southern taiga and mixed forests, the average annual temperature ranged from 2.9 to 6.6 ℃, and the рНHCl level of extracts from soils was in the range of 4.2-5.6. It is shown that the activity of exozymes in the soil of southern taiga and mixed forests depends most of all on the average annual temperature and pH level. No relationship between the enzyme activity and soil organic carbon was found. Artificial soil salinity led to an increase in the activity of invertase and urease. Soil contamination with zinc (25.5 and 255.0 mg / kg of dry soil) suppressed only the invertase activity. Thus, the influence of natural abiotic factors on the activity of soil enzymes was more often than the chemical load.

Oil spills in the Arctic are becoming more likely as shipping traffic increases in response to climate-related sea ice loss. To improve oil spill detection capability, we used a controlled mesocosm to analyze the multi-polarized C-band backscatter response of oil in newly-formed sea ice. Artificial sea ice was grown in two cylindrical tubs at the University of Manitoba’s Sea-ice Environmental Research Facility. The sea ice physical characteristics, including surface roughness, thickness, temperature, and salinity, were measured before and after oil injection below the ice sheet. Time-series C-band radar backscatter measurements detected the differences in the sea ice evolution and oil migration to the sea ice surface in the oil-contaminated tub, which was compared to uncontaminated ice in a control tub. Immediately prior to the presence of oil on the ice surface, the co-polarized backscatter increased by 13 dB local maximum, while the cross-polarized backscatter decreased by 9 dB. Ice physical properties suggest that the local backscatter maximum and minimum, which occurred immediately before oil migrated onto the surface, were related to a combination of brine and oil upward migration. The findings of this work provide a baseline data interpretation for oil detection in the Arctic Ocean using current and future C-band multi-polarization radar satellites.

Long-chain alkenones (LCAs) produced by phylogenetically classified Groups 1 and 3 Isochrysidales are increasingly used for paleotemperature and/or paleosalinity reconstructions in oligohaline lakes and marine environments. However, there are considerable difficulties in the paleoenvironmental interpretation of LCAs from Group 2 Isochrysidales thriving in saline lakes. The biggest challenge lies in our poor understanding of the complexity and ecological niches of individual Group 2 subclades in saline lakes. Here, we perform comprehensive analysis of haptophyte-specific 18S rRNA sequences and distributions of LCAs, and long-chain alkenoates (LCEs) in surface sediments and suspended particulate matter (SPM) from 37 saline lakes in northern China. These lakes span a large salinity gradient from 0.5 to 308‰. Combined with published genomic data of Group 2 Isochrysidales, our phylogenetic analysis reveals three Group 2 subclades occupying distinct ecological niches: one ice-related bloomer Group 2i and two warm-season bloomers Groups 2w1 and 2w2. Group 2i, the earliest seasonal bloomer, frequently co-occurs with Group 2w1 in sediments from saline lakes with relatively low to intermediate salinity waters, whereas Group 2w2 blooms in hypersaline waters. Based on existing data, C39:4 methyl alkenone is a chemotaxonomic biomarker for Group 2i. %C37:4 (relative abundance of C37:4 to the total C37 alkenones) values in the three Group subclades follow the order: Group 2i > Group 2w2 > Group 2w1. The %C37:4 in sediment cores of saline lakes does not directly record past salinity changes, but instead reflects variable contributions in production by these three subclades. This could indirectly and partially reflect overall salinity changes in some lakes dominated by Groups 2i and 2w1, but can be more complicated in lakes dominated by other assemblages. For our sites, we also demonstrate that direct use of C37 alkenone unsaturation indices ( U 37 K , U 37 K ' , and U 37 K ' ' ) for paleotemperature reconstructions in saline lakes is generally not feasible, except for cases where alkenone-producing Isochrysidales are dominated by one single species/subclade and seasonal production effects can be circumvented. We propose two possible alternative proxies for paleotemperature reconstructions in saline lakes: 1) unsaturation ratios of C41 and C42 alkenones, as these compounds are predominantly produced by a limited number of Group 2 species, such as Isochrysis nuda ( Liao et al., 2020 ); 2) C38Et/C36OEt ratio (ratio of C38 ethyl alkenones and C36 ethyl alkenoates), which appears to have similar temperature sensitivity for Groups 2w1 and 2w2, in lakes with no Group 2i inputs. Our study provides new insights into the phylogenetic classifications of Group 2 Isochrysidales and their ecological/environmental niches, which are fundamental for more quantitative and rigorous applications of LCAs and LCEs in saline lakes as paleosalinity and paleotemperature proxies.

Groundwater is an indispensable source of water due to its substantial use for domestic, irrigation, and industrial purpose. This study is determined to examine the irrigation quality of groundwater in the seasons of pre-monsoon (PRM) and post-monsoon (POM) in the year 2013 at Pennagaram block of Dharmapuri district, Tamilnadu. A few samples of groundwater from the study area are analyzed for their physicochemical parameters (APHA, 1998). The parameters to examine irrigation quality of the samples taken in this study are Cl−/HCO3− ratio, percent sodium (%Na), Index of Base Exchange (IBE), Residual Sodium Carbonate (RSC), Kelly’s ratio (KR), Permeability Index (PI), Sodium Adsorption Ratio (SAR), Potential Salinity (PS), Magnesium Ratio (MR), Salinity Index and Sodicity Index. The classification of groundwater samples for irrigation was identified using the USSL Diagram, Doneen’s plot, and Wilcox diagram. The spatial distribution map gives a clear depiction of the groundwater quality for irrigation purposes, in both seasons. The plot of Cl−/HCO3− versus Cl− indicates that the groundwater samples are strongly affected by salinity. It illustrates the exchangeable mechanism which has one of the responses for the chemical composition of groundwater in the study area. According to %Na, RSC, KR, SAR, PI, MR, Salinity index, and Sodicity index makes the groundwater of the study area was safe for irrigation. According to the results of PS and Sodicity index the groundwater of marginal quality i.e., closely unfit for irrigational purpose.

17 USC 105 interim-entered record; under review. The article of record as published may be found at https://doi.org/10.5194/os-18-29-2022 Substantial amounts of nutrients and carbon enter the Arctic Ocean from the Pacific Ocean through the Bering Strait, distributed over three main pathways. Water with low salinities and nutrient concentrations takes an eastern route along the Alaskan coast, as Alaskan Coastal Water. A central pathway exhibits intermediate salinity and nutrient concentrations, while the most nutrient-rich water enters the Bering Strait on its western side. Towards the Arctic Ocean, the flow of these water masses is subject to strong topographic steering within the Chukchi Sea with volume trans port modulated by the wind field. In this contribution, we use data from several sections crossing Herald Canyon collected in 2008 and 2014 together with numerical modelling to investigate the circulation and transport in the western part of the Chukchi Sea. We find that a substantial fraction of water from the Chukchi Sea enters the East Siberian Sea south of Wrangel Island and circulates in an anticyclonic direction around the island. This water then contributes to the high nutrient waters of Herald Canyon. The bottom of the canyon has the highest nutrient concentrations, likely as a result of addition from the degradation of organic matter at the sediment surface in the East Siberian Sea. The flux of nutrients (nitrate, phosphate, and silicate) and dissolved inorganic carbon in Bering Summer Water and Winter Water is computed by combining hydrographic and nutrient observations with geostrophic transport referenced to lowered acoustic Doppler current profiler (LADCP) and surface drift data. Even if there are some general similarities between the years, there are differences in both the temperature–salinity and nutrient characteristics. To assess these differences, and also to get a wider temporal and spatial view, numerical modelling results are applied. According to model results, high-frequency variability dominates the flow in Herald Canyon. This leads us to conclude that this region needs to be monitored over a longer time frame to deduce the temporal variability and potential trends. The science was financially supported by: US National Science Foundation (Grant Number: GEO/PLR ARCSS 575 IAA#1417888), the Department of Energy (DOE) Regional and Global Model Analysis (RGMA), the Swedish Research Council Formas (contract no. 2018-01398), and the Swedish Research Council (contract nos. 621-2006-3240, 621-2010-4084, and 2012-1680). This work was carried out with logistic support from the Knut and Alice Wallenberg Foundation and from Swedish Polar Research Secretariat. The Department of Defense (DOD) High Performance Computer Modernization Program (HPCMP) provided computer resources. This study was also supported by the Russian Scientific Foundation (grant no. # 21-77-580 30001). The science was financially supported by: US National Science Foundation (Grant Number: GEO/PLR ARCSS 575 IAA#1417888), the Department of Energy (DOE) Regional and Global Model Analysis (RGMA), the Swedish Re search Council Formas (contract no. 2018-01398), and the Swedish Research Council (contract nos. 621-2006-3240, 621-2010-4084, and 2012-1680). This work was carried out with logistic support from the Knut and Alice Wallenberg Foundation and from Swedish Polar Research Secretariat. The Department of Defense (DOD) High Performance Computer Modernization Program (HPCMP) provided computer resources. This study was also supported by the Russian Scientific Foundation (grant no. # 21-77-580 30001).

The K?rklareli Reservoir, located in the Meri?-Ergene River Basin, is an important drinking/industrial freshwater resource of the K?rklareli Province. In order to ensure the sustainable use of this important reservoir, its current situation should be examined periodically and evaluated by multivariate analyses. For this reason, water samples were taken between the dates April 2018 and February 2019 at monthly intervals from 3 different stations. The data on the environmental and physicochemical variables (water temperature, dissolved oxygen, pH, salinity, conductivity, total dissolved solids, chlorophyll-a, light permeability, fluoride, chloride, NO2-N, NO3-N, PO4, SO4 and essential/potentially toxic elements) were measured and evaluated according to the classes of surface water quality control regulation of Turkey. The parameters exceeding first-class water quality values (chlorophyll-a, pH, NO2-N, chloride, selenium) were mapped in GIS using the spline integration approach. In addition, the sodium absorbtion ratio, Kelly index values and magnesium ratio, were calculated to evaluate the water quality for agricultural irrigation water standards. The water quality of the reservoir was evaluated using multivariance analyses (Bray?Curtis similarity index, correspondence analyses, Pearson correlation index). As a result, it was emphasized that the use of the GIS approach is a potential useful method for monitoring the sustainable water quality of the K?rklareli Reservoir, which was determined to have an oligomesotrophic character.

Soil salinization caused by natural and anthropogenic factors is an important environmental hazard especially in arid and semi-arid regions of the world. Accumulation of salts in the soil is a major threat to crop production and global agriculture; therefore, rapid and precise detection of salt-affected lands is highly critical for preserving soil sustainability and supporting food production. Advancement in remote sensing techniques and machine-learning algorithms has started to contribute to fast and large-scale monitoring and mapping of soil salinization throughout the world. This paper aims to analyze the performance of three different machine-learning algorithms to map soil salinity using Landsat-8 OLI, Sentinel-2A satellite images, and ground-based electrical conductivity (EC) measurements with the aid of Google Earth Engine (GEE) platform. Classification and regression trees (CART), random forest (RF), and support vector regression (SVR) methods are implemented to create a correlation between ground measurements and satellite-derived environmental variables or spectral indices. After selecting the optimum five variables including wetness band, three soil salinity indices, and one vegetation index, soil salinity maps are generated in three machine-learning algorithms. The output soil salinity map in RF algorithm demonstrated the most reliable spatial distribution of various soil salinity classes in the selected study area. Despite CART provided slightly better prediction of soil salinity with R-squared (R2) of 0.98 for Sentinel-2A data, and 0.96 for Landsat-8 OLI data in comparison with accuracy results of RF technique with R2 of 0.96 for Sentinel-2A data and 0.94 for Landsat-8 OLI data, the output map of RF model estimated more reliable salinity levels in salt crusts, agricultural lands, drainage areas, and swamps. The corresponding result highly matched with visual interpretation. Soil salinity maps derived from SVR algorithms by using various combinations of input variables displayed relatively poor estimation of soil EC values compared to the other two methods.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.1. Reduction in diversity of both freshwater aquatic and terrestrial ecosystems has been attributed to salinity increase and such increases are a symptom of changes to land use. Hydrological alteration to ground and surface water are likely to be associated with salinity increase and its influence on biodiversity. However the combined effects of salinity and hydrology on aquatic biodiversity have not been elucidated fully in either field or experimental situations.2. The effect of salinity and water regime on the biota in sediments from seven wetlands from inland south-eastern Australia was tested experimentally using germination of aquatic plant seeds (five salinity and two water levels) and emergence of zooplankton eggs (five salinity levels). Salinity levels were

Murray-Darling Freshwater Research CentreMDFRC item.In Australia, many freshwater wetlands are becoming saline. Knowing which elements of a biotic community will persist as wetlands turn saline is relevant to their future management. We simulated gradual and sudden increases in salinity in outdoor mesocosms to test the hypotheses that: (1) aquatic plant and zooplankton communities exposed to a gradient of increasing salinity over time would initially resemble freshwater communities, but as the salinity increased they would resemble communities found in more saline systems; and (2) that a gradual change in salinity over 6 months influences zooplankton and plant communities in the same way as a sudden salinity change. Below 1000 mg L–1, as salinity increased gradually, communities rich in species and numbers of individuals resembled freshwater communities. However, as the salinity exceeded 1000 mg L–1, taxa were progressively lost and communities became less diverse. When salinities exceeded 3000 mg L–1 the diversity decreased rapidly and few taxa remained at 5000 mg L–1. Both sudden and gradual increases in salinity induced similar decreases in diversity. We predict that as natural wetlands become more saline, few freshwater biota will survive once the salinity exceeds 5000 mg L–1. In the long term, such salinised wetlands would need to be recolonised by salt-tolerant taxa for a functional wetland to persist.

Murray-Darling Freshwater Research CentreMDFRC item.1. In this study we compared the emergence of aquatic biota from sediments under 14-daypulses of high (5000 mg L)1) and low (1000 mg L)1) salinity with emergence underfreshwater and equivalent constant salinity levels. We tested the hypothesis that pulses ofhigh salinity and short duration have no impact on the emergence of aquatic plants andzooplankton from wetland sediment.2. The way salt is moved through the landscape may alter the response of biota to increasesin salinity. Under natural hydrological regimes in rivers and floodplains salinity pulsesoccur often at concentrations that exceed predicted tolerance levels for aquatic biota. Theimpacts of natural pulses of high salinity followed by rapid return to fresh conditions maybe used to inform management guidelines for the potential release of non-natural salinewater into river systems with minimal impact.3. For both aquatic plants and zooplankton the abundance and richness of the emergingtaxa decreased at higher salinities kept at constant levels. In contrast, pulses of salinityfollowed by return to freshwater conditions did not have a negative impact on theemergence of aquatic plants or zooplankton. For many taxa of zooplankton a positiveimpact was demonstrated with higher emergence following the salinity pulse.4. The responses of aquatic plant and zooplankton taxa are grouped into five responsetypes. Type 1: negatively impacted by all salt regimes. Type 2: preference for constantsalinities. Type 3: no difference between fresh and either pulse regime. Type 4: preferencefor high concentration pulses. Type 5: emergence higher under a low concentration pulse.5. Although previous studies indicate that constant high-level salinity in rivers andwetlands can decrease the species richness of aquatic communities, this current studyshows pulses may not have the same impact. Our results support the hypothesis thatpulses of high salinity and short duration do not impact on the emergence of aquatic plantsand zooplankton from wetland sediments. For zooplankton, pulses of salt may triggeremergence.6. These trends may be used to explore the potential to use managed water releases to movesalt through the landscape with minimal impact of salinity on aquatic biota. However,before such preliminary results are applied in management of saline water releases weneed to determine the implications for interacting processes in natural ecosystems.

Murray-Darling Freshwater Research CentreMDFRC item.The presence of sulfidic sediments (potential acid sulfate soils) is an emerging problem in the management of inland wetlands. Using data from 81 wetlands in the Murray-Darling Basin, a simple protocol was developed to assess whether a wetland will contain sulfidic sediments at levels that could cause ecological damage. Risk factors include whether or not the wetland receives municipal waste or irrigation return water, elevated salinity in the overlying water (>1750 µS/cm) or sediment (400 µS/cm in a 1:5 soil : water extract) and high levels of sulfate in the water column (>10 mg/L). Neutral or basic sediment pH indicates that, even if the sediment does contain sulfidic sediments, there is a reduced likelihood of acidification if the sediments are oxidized.

We present a geostatistics-based stochastic salinity estimation framework for the Montebello Oil Field that capitalizes on available total dissolved solids (TDS) data from groundwater samples as well as electrical resistivity (ER) data from borehole logging. Data from TDS samples (n = 4,924) was coded into an indicator framework based on falling below four selected thresholds (500, 1,000, 3,000, and 10,000 milligrams per liter (mg/L)). Collocated TDS-ER data from the surrounding groundwater basin were then employed to produce a kernel density estimator to establish conditional probabilities for ER data (n = 8 boreholes) falling below the selected TDS thresholds within the Montebello Oil Field area. Directional variograms were estimated from these indicator coded data, and 500 TDS realizations from conditional indicator simulation were generated for the subsurface region above the Montebello Oil Field reservoir. Simulations were summarized as 3D maps of median TDS, most likely salinity class, and probability for exceeding each of the specified TDS thresholds. Results suggested TDS was below 500 mg/L in most of the study area, with a trend toward higher values (500-1,000 mg/L) to the southwest; consistent with the average regional groundwater flow direction. Discrete localized zones of TDS greater than 1,000 mg/L were observed, with one of these zones in the greater than 10,000 mg/L range; however, these areas were not prevalent. The probabilistic approach used here is adaptable and is readily modified to include additional data and types and can be employed in time-lapse salinity modeling through Bayesian updating. This article is protected by copyright. All rights reserved.

Lake ice phenology is regarded as a good proxy for the past and present climates. Long time series passive microwave radiometry data are used to estimate lake ice phenology variations in the Qinghai–Tibet Plateau (QTP), and a contrasting pattern of phenology change trend is found that the time series trend of lake ice freeze-up or break-up time is obviously reversed for lakes in the QTP. The reason for this contrasting trend of lake ice phenology is discussed based on factors such as salinity, water volume change, and air temperature change. Lake ice phenology data are separated based on lake salinity for the climate study: lake ice phenology of lakes with low salinity can be used as air temperature and climate change indicator, whereas lake ice phenology of lakes with high salinity and a low water volume can be used as an indicator of water volume variation under climate change. Correlation analysis of air temperature and the lake ice phenology show that air temperature is the main driving factor behind lake ice phenology variations. The lake ice phenology results suggest overall rising air temperatures during the period 1987–2017 in all regions of the QTP.

Chlorophyll is a significant biochemical component and can be determined in the laboratory (destructive) and using various chlorophyll content measuring devices (non-destructive). In this study, destructive and non-destructive methods were used to determine chlorophyll content and compared in peanut (Arachis hypogaea cv. NC-7) grown under different soil texture and saline water applications. The experiment was carried out in a complete randomized block design in pots using two soil textures (clay-loam and sandy) and three irrigation water salinity (0.7, 2.1 and 3.3 dS m-1). While the chlorophyll contents (Chl-a , Chl-b, Chl-a+b, Chl-a/b) were determined with the acetone extraction procedure, which is classified as destructive methods under laboratory conditions, the Chlorophyll Content Index (CCI) values were measured with the hand-held chlorophyll meter device (Apogee CCM-200), which is a non-destructive method. While irrigation water salinity decreased all types of chlorophyll contents (Chl-a, Chl-b, Chl-a+b) (mg cm-2), it did not cause a statistical difference in Chl-a/b. Linear and polynomial models were fitted between the different chlorophyll contents and the CCI values under different soil textures and saline water levels. Model performances were slightly better with the polynomial model compared to the linear model in all experimental treatments. Since the difference between model performances is small, it is recommended to use the linear model due to its ease of use. In addition, the total chlorophyll content can be safely estimated under saline conditions by using portable chlorophyll meters.

Direct measurement of methane emissions is cost-prohibitive for greenhouse gas offset projects, necessitating the development of alternative accounting methods such as proxies. Salinity is a useful proxy for tidal marsh CH4 emissions when comparing across a wide range of salinity regimes but does not adequately explain variation in brackish and freshwater regimes, where variation in emissions is large. We sought to improve upon the salinity proxy in a marsh complex on Deal Island Peninsula, Maryland, USA by comparing emissions from four strata differing in hydrology and plant community composition. Mean CH4 chamber-collected emissions measured as mg CH4 m−2 h−1 ranked as S. alterniflora (1.2 ± 0.3) ≫ High-elevation J. roemerianus (0.4 ± 0.06) > Low-elevation J. roemerianus (0.3 ± 0.07) = S. patens (0.1 ± 0.01). Sulfate depletion generally reflected the same pattern with significantly greater depletion in the S. alterniflora stratum (61 ± 4%) than in the S. patens stratum (1 ± 9%) with the J. roemerianus strata falling in between. We attribute the high CH4 emissions in the S. alterniflora stratum to sulfate depletion likely driven by limited connectivity to tidal waters. Low CH4 emissions in the S. patens stratum are attributed to lower water levels, higher levels of ferric iron, and shallow rooting depth. Moderate CH4 emissions from the J. roemerianus strata were likely due to plant traits that favor CH4 oxidation over CH4 production. Hydrology and plant community composition have significant potential as proxies to estimate CH4 emissions at the site scale.

Soil resistivity depends on many overlapping factors, which influence it in various ways. The aim of this study was to determine the effects of some physical and chemical factors on soil apparent resistivity. The results of field, laboratory, and statistical studies revealed a complex relationship between water content, pH, and salinity with soil apparent resistivity. The results showed that water content had a clear effect on apparent resistivity, as it increased significantly when water content value decreased to less than about 5%. The results also showed that increasing the salinity ratio at the expense of water content led to an increase in the apparent resistivity values. The apparent resistivity values also increased significantly when pH values ​​fell below about 7.7. The increase in air temperature caused an increase in water evaporation from the soil, which led to increasing the apparent resistivity. The rise in air temperature also caused an increase in the concentration of salts at the expense of water content; since salts are considered to be insulators, unless they are dissolved in water, they cause an increase in the value of apparent resistivity.

Forest degradation is a worldwide problem, although its causes vary due to geographical and climatic differences and man-made causes. In recent years, the Robinia pseudoacacia forest in the Yellow River Delta has suffered severe degradation. The causative mechanisms were investigated in the field over two years, and the results show that increased forest degradation was reflected by increased tree mortality, high leaf and soil sodium salt levels and groundwater depth. Average tree diameters decreased, and leaf chlorophyll and soil microbial contents decreased. Redundancy discriminate analysis (RDA) showed that degradation of the forest was correlated positively with soil salt content, but negatively with groundwater depth. Correlation analysis showed that 0.79%–0.95% soil salt content and above 1.20 m groundwater depth caused the death of R. pseudoacacia trees due to localized anthropogenic economic activities, such as rice farming, that disrupted the original water–salt balance. Measures are recommended to prevent further degradation and restore degraded forests.

The conservation of protected areas is nowadays one of the concerns of international and national institutions. This study aims to contribute to better conservation of the ichthyological fauna of the lagoon area of the Azagny National Park (PNA). This national park has been dealing with the harmful effects of human activities for years. Thus, from March 2019 to February 2020, sampling campaigns were carried out to characterize this space, for better conservation. The results obtained are based on the analysis of abiotic and biotic (fish) data collected at 6 stations. The physicochemical parameters were measured using a multiparameter and the fish population collected using 10 gillnet batteries of 10, 25, 30, 35, 40 and 50 mm mesh void. The analysis of the ichthyological population of the lagoon area reveals a diversity of 53 species belonging to 30 families and 12 orders. 11 species were newly collected while 31 species previously recorded in these hydrosystems were not captured in the present study. The Shannon (H’> 2) and Equitability (E> 0.5) indices calculated reflect a good organization and stability of the ichthyological population of the hydrosystems of the PNA lagoon zone. The Monte-Carlo test indicates that the variables rate of nitrate, width, rate of dissolved oxygen, water temperature, alkalinity, salinity, rate of dissolved solid and phosphorus are those which discriminate specific richness, abundance and the distribution of the stand.

The groundwater of Awe-Keana saline fields in central Nigeria was studied to investigate physicochemical processes that influence its groundwater chemistry and quality and hence determine its quality for drinking and irrigation purposes. Twenty groundwater samples were collected from hand-dug wells and boreholes for the purpose of identifying the hydrochemical characteristics and assessing the quality of groundwater of the Awe-Keana saline fields. Principal component analysis was performed to identify the hydrochemical controlling processes while water quality index (WQI) was used to determine the overall quality of the water samples. Multiple regression analysis, however, revealed the parameter(s) that impact the overall water quality the most. The results showed that the chemical compositions of the groundwater of the area is influenced by weathering of hostrocks, salinity and anthropogenic activities. Four hydrochemical facies were deciphered (Ca-Mg-HCO3, Na-K-HCO3, Na-K-Cl-SO4, and Ca-Mg-Cl-SO4) and this revealed the diversity in the chemical controlling processes that yield different facies. Two clusters of water groups were identified from cluster analysis, namely, groundwater characterized with very high salinity, high nitrate contamination and high Ca, Cl, Na, and HCO3 ionic concentrations and groundwater with high Mg, K, and SO4 ionic concentrations. Saturation indices in relation to different minerals showed that precipitation and dissolution processes gave rise to the concentrations of different ions in the groundwater. Water quality assessment showed that about 85 % of the groundwater of the area is unsuitable as drinking water but, generally suitable for irrigation. Multiple regression analysis revealed that NO3 ion among the hydrochemical parameters measured was observed to be the major pollutant in the groundwater of the study area.

The effects of sea level rise and coastal saltwater intrusion on wetland plants can extend well above the high-tide line due to drought, hurricanes, and groundwater intrusion. Research has examined how coastal salt marsh plant communities respond to increased flooding and salinity, but more inland coastal systems have received less attention. The aim of this study was to identify whether ground layer plants exhibit threshold responses to salinity exposure. We used two vegetation surveys throughout the Albemarle-Pamlico Peninsula (APP) of North Carolina, USA to assess vegetation in a low elevation landscape (≤ 3.8 m) experiencing high rates of sea level rise (3–4 mm/year). We examined the primary drivers of community composition change using Non-metric Multidimensional Scaling (NMDS) and used Threshold Indicator Taxa Analysis (TITAN) to detect thresholds of compositional change based on indicator taxa, in response to potential indicators of exposure to saltwater (Na, and the Σ Ca + Mg) and elevation. Salinity and elevation explained 64% of the variation in community composition, and we found two salinity thresholds for both soil Na+ (265 and 3843 g Na+/g) and Ca+ + Mg+ (42 and 126 µeq/g) where major changes in community composition occur on the APP. Similar sets of species showed sensitivity to these different metrics of salt exposure. Overall, our results showed that ground layer plants can be used as reliable indicators of salinity thresholds in coastal wetlands. These results can be used for monitoring salt exposure of ecosystems and for identifying areas at risk for undergoing future community shifts.

Seawater intrusion in coastal aquifers is a major concern due to geogenic and anthropogenic activities leading to declining groundwater quality. The present study focuses on deciphering the sea water intruded zones and its extent in the Quaternary alluvial aquifer system in the coastal belt of Digha, West Bengal, India. In this study, 36 groundwater samples were collected during pre-monsoon (2020). Subsequently, an integrated approach of hydrogeological, hydrogeochemistry, bulk magnetic susceptibility, isotopic, multivariate statistical, and geochemical modeling is adopted. Spatial distribution maps of hydrological parameters (salinity, conductivity, TDS) and major ion concentration (Na+, K+, Ca2+, Mg2+, Cl−, SO42−, F−, and Br−) suggest that the northern, south-west, and eastern parts of the study area are largely affected by saltwater intrusion and are corroborated with seawater mixing index (SMI). Based on sodium adsorption ratio (SAR), sodium percentage (Na%), and Permeability index (PI) distribution maps, the same locations are identified under critical condition for the suitability of groundwater for irrigation. The order of concentration of cations and anions in the water samples are Na+ > Ca2+ > Mg2+ > K+ and HCO3− > SO4− > Cl− > Br− > F− respectively. Piper diagram shows three principal hydrochemical water types with water composition changes from fresh (86%) to saline water mix (14%). The hydrochemical facies evolution diagram depicts 81% of water samples are in the freshening phase, and 19% are in the intrusion phase. The various bivariate plots revealed that ion exchange, reverse ion exchange, silicate weathering, seawater mixing, and anthropogenic inputs are the governing factors that control groundwater evolution. R-mode factor analysis, principal component analysis (PCA), and agglomerative hierarchical cluster (AHC) also indicate the influence on groundwater from seawater mixing and/or seawater intrusion. The superlativeness of bulk magnetic susceptibility (χ) analysis of water samples in delineating seawater intruded zones is elaborated. Saturation index (SI) shows that groundwater is saturated (> 0) with calcite, dolomite, and aragonite, plausibly due to seawater ingression. Stable isotopic analysis of δ2H (− 53.979 to − 16.9578‰) and δ18O (− 7.00183 to − 1.37 ‰) suggests precipitation recharge/paleo-water at some locations and evaporation enrichment of groundwater. It is recommended to increase groundwater recharge, reduce groundwater extraction at critically affected locations, and have regular monitoring and management to control seawater intrusion.

The waters of Teluk Lamong are located on the north sea coast of Surabaya, which is directly adjacent to the Gresik Regency. Lamong Bay is famous as a strategic port place on an International scale. Along the coastal waters of Teluk Lamong, some rivers flow in Lamong Bay. These activities can lead to interaction between fresh water and seawater. This interaction affects the pattern of salinity spread and sea surface temperature in the waters of Teluk Lamong. Salinity and Sea Surface Temperature is one of the biggest factors causing corrosion in the sea that will damage the structure of buildings around the sea. It is expected that in this research as information about the waters of Teluk Lamong for data information or database utilization in the field of civil engineering, among others, port maintenance and coastal building planning. Based on this background, research is needed to monitor the spread of salinity values and sea surface temperatures in Lamong Bay using Landsat 8 satellite imagery for the years 2016 and 2020. The result of modeling the algorithm obtained, the model of the algorithm used to process the salinity of the image is the wavelength Band_4 in the Equation Power with the model algorithm y = 25.437x-0.046, and the degree of determination value R² = 0.5825. While sea surface temperature in power equation with algorithm model y = 302.14x0.0029 and determination value R² = 0.4182. The results of an analysis of the T-test and validation test can be qualified. The results of the analysis of imagery data showed salinity distribution ranged from 27.33 (ppm) to 29.9 (ppm), while sea surface temperatures ranged from 303.95 Kelvin to 304.39 Kelvin.