Levels Of NO3 Research Articles

Water Quality and Plankton Population Abundance Affected by Earthen Ponds Management

The study was conducted in two earthen ponds fish farming systems located at (El-Rayed area- Kafer El-Shiak governmentEgypt); namely, feed and fertilizer fish farming systems. Each system was replicated in four ponds (8000m2 each), to determine water quality, phytoplankton and zooplankton abundance. Nile tilapia (Orechromis niloticus); mullet (Mugil cephalus) and catfish (Clarias garipinus) were cultured in each pond at initial weight of 2, 30 and 50 g, respectively. The present study aimed to evaluate two fish farming systems differing in pond management procedures in the Nile Delta regions. Results apparent insignificant differences between the two fish farming systems in terms of water temperature (ranged 12.7 to 30.9°C from winter to summer months), salinity, EC and total hardness. Whilst, fertilizer fish farm had significantly high levels of pH, DO, secchi disc, total alkalinity, orthophosphate, TAN, NO2, NO3, algal abundance and chlorophyll “a” n water compared to those of feed fish farm. Significant increase (P<0.05) in phytoplankton and zooplankton abundance were observed in fertilizer fish farm compared to feed fish farm, this was due the high organic manure inputs to pond water during all seasons including winter at one ton per feddan every 10 days.

Nitrogen limitation prevents the effects of iron or dust additions on biological carbon fixation in the Gulf of California

This paper reports the effect of dissolved iron (dFe) and dust additions on the Biological Carbon Fixation (BCF) rates in the surface layer of the central Gulf of California (GC). Two on deck experiments were conducted in the summer of 2016 at an oceanographic station located in the Guaymas Basin. Each experiment consisted in the incubation of natural phytoplankton assemblages collected at three distinct depths within the upper 50 m layer and amended either with iron (FeCl3) or dust leachate, followed by the quantification of BCF rates using the 13C assimilation method. A very warm (∼30 °C) water column strongly stratified and with reduced phytoplankton biomass (<1 mg chlorophyll a m−3) was indicative of an oligotrophic environment. In addition, the surface levels of NO3−+NO2− (<0.1 μM), dFe (1.71 ± 1.04 nM), as well as the Fe:N (78 ± 47 nmol μmol−1) and N:P (0.04 ± 0.01) ratios revealed that phytoplankton was under conditions of inorganic nitrogen limitation. BCF rates measured during the experiments ranged between 0.46 ± 0.04 and 6.24 ± 0.34 mg C m−3 h−1 with the highest values at the maximum of fluorescence and their vertical distribution was associated with the carbon biomass of picophytoplankton and diatoms. Despite the oligotrophic condition that predominated during the cruise, most of the Fe or dust additions did not show a significant effect (p > 0.05) on the magnitude of BCF rates, which was attributed to the fact that N, rather than Fe, was the limiting nutrient for phytoplankton production. However, Fe limitation cannot be completely ruled out as two samples (one for each treatment) showed a significant increase (p < 0.05) in BCF rates. We suggest that atmospheric supply of dust during the summer could play a relevant biological role maintaining high concentrations of dFe (and other bioactive metals) in the surface waters of central GC.

Enhancement of iron-based nitrogen removal with an electric-magnetic field in an upflow microaerobic sludge reactor (UMSR).

Traditional denitrification often produces high operating costs and excessive sludge disposal expenses due to conventional carbon sources. A novel electric-magnetic field (MF) 48 mT with Fe0 and C-Fe0 powder in an upflow microaerobic sludge reactor (UMSR) improved nitrogen removal from wastewater without organic carbon resources and gave richness to the heterotrophic bacterial community. In the current study, the reactor was operated for 78 ± 2days, divided into five stages (without Fe0, with Fe0, coupling with MF, without coupling with MF, and coupling with MF again), at a hydraulic retention time (HRT) of 2.5h, with an influent loading of ammonium (NH4+-N) 50 ± 2mg/L, at 25-27°C, and less than 1.0mg/L dissolved oxygen (DO). The results demonstrated nitrogen removal efficiency enhanced after coupling with MF on the levels of NO3--N by 76% with an effluent concentration of 8.7mg/L, NH4+-N by 72% with an effluent concentration of 13.6mg/L, and total nitrogen removal (TN) by 76%, respectively. After coupling the MF with the reactor, the microbial community data analysis showed the dominant abundance of ammonia-oxidizing bacteria, heterotrophic nitrifying bacteria, and denitrifying bacteria on the level of Anaerolineaceae_uncultured 2%, which is capable of denitrification that uses Fe2+ as an electron source, Gemmatimonadaceae_uncultured 4%, Hydrogenophaga 4% which is capable of catalyzing hydrogenotrophic denitrification and correlating to nitrate removal, denitrification and desulfurization bacteria SBR1031_norank 18%, anammox-bacteria Saccharimonadales_norank 2%, and (AOM) Limnobacter 3% in the sludge.

Changes in NO3 Radical and Its Nocturnal Chemistry in Shanghai From 2014 to 2021 Revealed by Long‐Term Observation and a Stacking Model: Impact of China's Clean Air Action Plan

AbstractNitrate radical (NO3), an important nocturnal tropospheric oxidant, was observed continuously in the eastern Chinese megalopolis of Shanghai from July 2018 to August 2021using differential optical absorption spectroscopy equipped with LED lamp. To assess changes in NO3 radical during the implementation of China's Clean Air Action Plan, a stacking model was developed to predict historical NO3 radical from 2014 to 2018 with good performance. Combining the observed and predicted data sets, the highest concentration of NO3 exceeded 300 pptv in 2021, while the highest monthly mean of 36.2 ± 30.9 pptv occurred in summer 2017. The impact of meteorology, precursors, and emissions on the evolution of nocturnal NO3 was quantified using the Kolmogorov‐Zurbenko filter. The rapid increase in annual NO3 from 2014 to 2017 was caused by a combination of persistently high precursor O3 concentrations, insufficient SO2‐represented primary pollutant reductions, and meteorological conditions favorable to NO3. As China's clean air actions advanced further, significant CO‐represented and SO2‐represented emission reductions overcame the impact of meteorological conditions and significantly lowered the NO3 levels between 2018 and 2021. These efforts drastically affected nocturnal NO3 chemistry, reducing NO3 loss rates by approximately 30% in both spring and summer in 2021 compared to 2014, although the NO3 levels were comparable between the 2 years. In addition, substantial reductions in CO‐represented and SO2‐represented primary pollutants, as well as effective management of NO2 and PM2.5, resulted in varying decreases in the rates of direct (removal by reactions with VOCs, etc.) and indirect (removal by heterogeneous consumption of N2O5) losses, thereby moderating secondary aerosol formation.

Magnesium alleviates aluminum-induced growth inhibition by enhancing antioxidant enzyme activity and carbon–nitrogen metabolism in apple seedlings

Previous studies have determined that magnesium (Mg) in appropriate concentrations prevents plants from suffering from abiotic stress. To better understand the mechanism of Mg alleviation of aluminum (Al) stress in apple, we investigated the effect of Mg on plant growth, photosynthetic fluorescence, antioxidant system, and carbon (C) and nitrogen (N) metabolism of apple seedlings under Al toxicity (1.5 mmol/L) via a hydroponic experiment. Al stress induced the production of reactive oxygen in the leaves and roots and reduced the total dry weight (DW) by 52.37 % after 20 days of treatment relative to plants grown without Al, due to hindered photosynthesis and alterations in C and N metabolism. By contrast, total DW decreased by only 11.07 % in the Mg-treated plants under Al stress. Supplementation with 3.0 mmol/L Mg in the Al treatment decreased Al accumulation in the apple plants and reduced Al-induced oxidative damage by enhancing the activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase) and reducing the production of H2O2 and malondialdehyde (MDA). Under Al stress, the Mg-treated plants showed a 46.17 % higher photosynthetic rate than the non-treated plants. Supplementation with Mg significantly increased the sucrose content by increasing sucrose synthase (SS) and sucrose-phosphate synthase (SPS) activities. Moreover, Mg facilitated the transport of 13C-carbohydrates from the leaves to roots. Regarding N metabolism, the nitrate reductase (NR), glutamine synthase (GS), and glutamate synthase (GOGAT) activities in the roots and leaves of the Mg-treated plants were significantly higher than those of the non-treated plants under Al stress. Compared with the non-treated plants under Al stress, the Mg-treated plants exhibited a significantly high level of NO3- and soluble protein content in the leaves, roots, and stems, but a low level of free amino acids. Furthermore, Mg significantly improved nitrogen accumulation and enhanced the transport of 15N from the roots to leaves. Overall, our results revealed that Mg alleviates Al-induced growth inhibition by enhancing antioxidant capacity and C-N metabolism in apple seedlings.

Spatiotemporal variability and control factors of NO3− in a polluted karst water system of an agricultural wetland in South China

Nitrate (NO3−) pollution in karst water is an important environmental issue in intensive agricultural regions worldwide. The integrated understanding of the spatiotemporal variability and control factors of NO3− pollution in karst water is imperative for controlling the diffuse pollution caused by agricultural activities. In this study, 49 water samples were collected from surface water (SW) and groundwater (GW) in the Huixian karst wetland (HKW) and analyzed using hydrogeochemical and isotopic data (δ18O–NO3–, δ15N–NO3– and δ13CDIC) in combination with a Bayesian mixing model to investigate the spatiotemporal distribution and control factors in NO3−-polluted karst water. The results showed that approximately 40.82% of the karst water samples exceeded the natural threshold value of 3 mg/L for NO3−-N, and 32.14% of the GW samples exceeded the permissible limit for drinking water established by WHO (10 mg/L as NO3−-N), indicating that high levels of NO3− were mainly found in GW samples from the agricultural core area, especially in the dry season. The NH4+-synthetic fertilizer (NHF) and soil organic nitrogen (SON) were the dominant factors controlling pollution sources in the HKW, accounting for 36.13% ± 4.66% and 28.68% ± 4.75% of the karst GW NO3− concentration, respectively. However, the seasonal differences in NO3− pollution sources were not significant in GW. Microbial nitrification was the main process affecting the NO3− levels in GW, whereas the occurrence of denitrification did not significantly affect NO3− concentration in the HKW due to the relatively low rate. Moreover, the HNO3 produced from NH4+ via microbial nitrification facilitated carbonate weathering, thereby controlling NO3− enrichment in karst GW. Our results suggest that NHF should be controlled to prevent further GW pollution in the HKW. Our study also provides a scientific basis for understanding the factors controlling the NO3− concentrations in karst water systems.

Elevated CO2 significantly increases N2 fixation, growth rates, and alters microcystin, anatoxin, and saxitoxin cell quotas in strains of the bloom-forming cyanobacteria, Dolichospermum

The effect of rising CO2 levels on cyanobacterial harmful algal blooms (CHABs) is an emerging concern, particularly within eutrophic ecosystems. While elevated pCO2 has been associated with enhanced growth rates of some cyanobacteria, few studies have explored the effect of CO2 and nitrogen availability on diazotrophic (N2-fixing) cyanobacteria that produce cyanotoxins. Here, the effects of elevated CO2 and fixed nitrogen (NO3−) availability on the growth rates, toxin production, and N2 fixation of microcystin, saxitoxin, and anatoxin-a - producing strains of the genus Dolichospermum were quantified. Growth rates of all Dolichospermum spp. were significantly increased by CO2 or both CO2 and NO3− with rates being highest in treatments with the highest levels of CO2 and NO3−for all strains. While NO3− suppressed N2 fixation, diazotrophy significantly increased when NO3−-enriched Dolichospermum spp. were supplied with higher CO2 compared to cultures grown under lower CO2 levels. This suggests that diazotrophy will play an increasingly important role in N cycling in CO2-enriched, eutrophic lentic systems. NO3− significantly increased quotas of the N-rich cyanotoxins, microcystin and saxitoxin, at ambient and enriched CO2 levels, respectively. In contrast, elevated CO2 significantly decreased cell quotas of microcystin and saxitoxin, but significantly increased cell quotas of the N-poor cyanotoxin, anatoxin. N2 fixation was significantly negatively and positively correlated with quotas of N-rich and N-poor cyanotoxins, respectively. Findings suggest cellular quotas of N-rich toxins (microcystin and saxitoxin) may be significantly reduced, or cellular quotas of N-poor toxins (anatoxin) may be significantly enhanced, under elevated CO2 conditions during diazotrophic cyanobacterial blooms. Finally, in the future, ecosystems that experience combinations of excessive N loading and CO2 enrichment may become more prone to toxic blooms of Dolichospermum.

Synergistic Interaction between Copper and Nitrogen-Uptake, Translocation, and Distribution in Rice Plant.

Interactions among nutrients have been widely recognized in plants and play important roles in crop growth and yield formation. However, the interplay of Cu and N in rice plants is not yet clear. In this study, rice plants were grown with different combinations of Cu and N supply. The effects of Cu-N interaction on the growth, yield production, Cu and N transport, and gene expression levels were analyzed. The results showed that the effect of N supply on rice growth and yield formation was more pronounced than that of Cu supply. The Cu supply significantly improved the uptake of N (by 9.52–30.64%), while the N supply significantly promoted the root-to-shoot translocation of Cu (by 27.28–38.45%) and distributed more Cu (1.85–19.16%) into the shoots and leaves. The results of qRT-PCR showed that +Cu significantly up-regulated the expression levels of both NO3− and NH4+ transporter genes OsNRTs and OsAMTs, including OsNRT1.1B, OsNRT2.1, OsNRT2.3a, OsNRT2.4, OsAMT1.2, OsAMT1.3, and OsAMT3.1. Meanwhile, +N significantly up-regulated the expression levels of Cu transporter genes OsHMA5 and OsYSL16. In addition, the supply of Cu up-regulated the expression levels of OsGS1;2, OsGS2, and OsNADH-GOGAT to 12.61-, 6.48-, and 6.05-fold, respectively. In conclusion, our study demonstrates a synergistic effect between Cu and N in rice plants. It is expected that our results would be helpful to optimize the application of N and Cu fertilizers in agriculture.

SRB-based bioelectrochemical system: A potential multipollutant combatant for enhanced landfill waste stabilization

Due to the lower proportion of organic matter and higher toxicity of the aged landfill, most of the advanced treatment technologies are not effective from economic, environmental, and social perspectives. This study evaluates the potential of sulfate-reducing bacteria (SRB) based bioelectrochemical-system (BES) in the decontamination of landfill wastes by reducing GHGs emissions and levels of soluble pollutants. The landfill waste (solid/leachate) collected from the Pirana Landfill site was assessed for economical long-term treatment and scaling up the feasibility of the designed system. The present system demonstrated significant improvement in volumetric hydrogen production of 3.1:1 (H2:CH4) by suppressing methanogenesis with a significant reduction in heavy metals concentration and other organic components. Despite being amended with 0.1 N ammonia, the treated leachate level of NO3 (2.350 ± 1.077 mg/L) was reduced by 5.3 times, hence reducing further groundwater pollution from landfill leaching. The BES-treated solid waste was more stabilized as shown by a fivefold increase in surface area and can be potentially applied for leachate immobilization and bio-fortification of agricultural fields. The vector arrangement and magnitude with differences in magnitudes for both leachate and solid waste supported the on-site applicability of BES treatment. Concerning the affinity in various treatment systems, the dendrogram clearly showed Ca and Fe placed far from each other (3506.08), in comparison to Fe and Mg (1186.6), followed by Fe and Cu (1544.6). Voltammograms proved the efficacy of the enriched electrochemically active bacteria (EAB), to support the treatment of landfill solid waste and leachate sustainably.

Citizen Science as a Co-Creative Measure to Water Quality: Chemical Data and Local Participation in a Rural Territory

It is becoming increasingly clear that the threat to the use of natural landscapes and persistent droughts are affecting the water quality of rural communities. The socio-ecological fit emerges as an aid to advance in the search for solutions to environmental problems in rural communities. Consequently, between May 2016 and September 2021, an interdisciplinary study of community-based water quality monitoring (CWQM) was implemented at a coastal catchment in the Ñuble region, Central Chile. The objective of the study was to involve the participation of local communities in initiatives to control the water quality of various parameters [pH, total iron (FeT), alkalinity as CaCO3, hardness (Ca2+ and Mg2+), sodium (Na+) and potassium (K+), water temperature, sulfate (SO42−) chloride (Cl−), and nitrate (NO3-)] in groundwater, share local knowledge, and apply co-creative measures for improving water conservation. In situ chemical data were also analyzed in the laboratory to check data quality. The PHREEQC hydrogeochemical model is used to characterize hydrogeochemical parameters of groundwater and to know about hydrogeochemical processes related to water quality. High levels of NO3− and FeT are recorded in 75% of the groundwater samples, mainly when water scarcity is higher during the summer. According to Chilean standards, nitrate levels exceed the maximum permissible limits for drinking water. A type of mainly Ca (Mg)–HCO3− carbonated water was recorded with Ca2+, Na+, Mg2+, and HCO3− as dominant ions. This study demonstrated the opportunity of a rural community group to help fill spatial data gaps in water quality monitoring and reassess water quality protection, especially considering the decrease in water availability in the region. Therefore, the community together with researchers can respond with an early alert system to water quality to collaborate with the implementation of rural drinking established on a community-based water quality monitoring. Moreover, to prioritize the level of urgency of rural water, minimize water pollution and improve the perception of the water and the resilience of their social–ecological system.

Successive corn stover and biochar applications mitigate N2O emissions by altering soil physicochemical properties and N-cycling-related enzyme activities: A five-year field study in Northeast China

As the most important source of commodity grain in China, Northeast China plays a crucial role in guaranteeing national food security. The application of biochar in agricultural ecosystems has shown immense potential in ensuring crop yields while mitigating N2O emissions. However, the long-term impacts and mechanisms of successive application of corn stover and its derived biochar on soil N2O emission in the corn monocropping region, such as Northeast China, remain unclear. A five-year field experiment was conducted in Northeast China to fill this research gap regarding the soil nitrogen (N) cycle. Three experimental treatments were established: a control with no corn stover or biochar application (CK), corn stover returned yearly at a rate of 7.5 t ha−1 (ST), and biochar added yearly at a rate of 2.6 t ha−1 (BC) corresponding to 35% of the stover addition rate in ST. Identical mineral fertilizers were applied in all three treatments. The total accumulated N2O emissions across five analyzed growing seasons within the CK, ST, and BC treatments were 260.2, 184.0, and 151.0 mg N2O m−2, respectively, with significant 29.3% and 42.0% decreases observed in ST and BC treatments, respectively, compared with the control. Based on the annual average from 2013 to 2017, ST and BC treatments significantly increased soil pH and total N (TN) content and significantly decreased the levels of NO3––N, NH4+-N, and soil bulk density (BD). Additionally, BC treatment remarkably lowered the average NH4+-N content than that under ST treatment by 24.1%. Both ST and BC showed a significant inhibitory effect on nitrate reductase (NR), nitrite reductase (NiR), and hydroxylamine reductase (HyR) activities related to denitrification. Soil N2O emission was significantly positively correlated with BD, NO3–-N, NH4+-N, NR, NiR, and HyR activities. Path analysis suggested that N2O emissions were primarily driven by NR and HyR activities and NO3–-N content. Overall, the applications of corn stover and its derived biochar are a feasible means of mitigating soil N2O emissions in the context of continuous corn cropping systems in mid-latitude regions like Northeast China, with biochar being more beneficial than stover application.

Simulation of the dispersed fluorescence spectrum of the NO[formula omitted][formula omitted] origin vibronic band

A vibronic Hamiltonian and transition dipole operator parametrized by high-level equation-of-motion coupled-cluster calculations are used as a basis for predicting the dispersed fluorescence spectrum of the B̃−X̃ origin band in the nitrate radical (NO3). The position and intensities of transitions to ground state vibrational levels observed in the photodetachment spectrum of the NO3 anion have previously been predicted to high fidelity with this Hamiltonian; it is expected that it also offers a basis for accurate prediction of the dispersed fluorescence spectrum. Comparison to experimental spectra provides considerable insight into various assignments. Significantly, this work joins a growing body of research that supports reassignment of the ground state ν3 vibrational fundamental to the region between 1050–1060 cm−1, which is more than 400 cm−1 below the feature to which it has traditionally been assigned. The in-plane vibrational levels below 2000 cm−1 are reviewed, with theory and experiment agreeing to within 25 cm−1 for all that have been observed experimentally. Finally, the various vibronic coupling mechanisms that affect the ground state energy levels of NO3 are summarized, and a discussion is provided about how the Lanczos algorithm can be used to efficiently calculate the dispersed fluorescence spectrum of the B̃−X̃ origin band.

Influence of velocity distribution conditions of coastal aquifer on nitrate contamination and seawater intrusion in the presence of subsurface physical barriers

The velocity distribution is an important factor that affects seawater intrusion (SI) and nitrate (NO3−) pollution. However, there are few studies on the impact of subsurface physical barriers (SPBs) on the velocity distribution of the whole aquifer and the impact of velocity distribution on SI and NO3− pollution. Especially, the quantitative method of velocity distribution has not been studied. By the methods of laboratory experiments and numerical simulations, effects of the NO3− concentrations of the pollution source, hydraulic gradients (HGs), the location of the SPB and relative heights of SPBs (HP’) on the SI, NO3− pollution levels and velocity in the presence of SI and SPBs were investigated. The velocity distribution was first quantified to better describe the relationships between the velocity and degrees of SI and NO3− pollution. The results showed that the HG and HP’ were the main factors that affected the velocity, NO3− pollution and SI. The higher the HG, the smaller the HP’, and the decreased SI inferred a more serious NO3− pollution. The influence of SPBs on NO3− pollution and SI was mainly affected by the changes in the velocity distribution in the aquifer. With increasing HGs, for the region with flow rate less than 0.5 m/d (A0.5), the smaller its distribution area is, the smaller the relative area of SI (TLs') is. With an increase in the HG or decrease in the HP’, the relative area of NO3− pollution (Ns') is proportional to the distribution area where the flow velocity is greater than 1 m/d (A1). When the flow velocity distribution condition was A′1 (the relative area of A1) > A′0.5-1 (A′0.5-1 is the ratio of the area where the flow velocities are greater than 0.5 m/d and less than 1 m/d to the total area of the aquifer) > A′0.5 (the relative area of A0.5), NO3− pollution was serious; when the flow velocity distribution condition was A′0.5 > A′0.5-1 > A′1, the levels of NO3− pollution were the lowest.

Feasibility Assessment of the Application of Groundwater Remediation Techniques in Rural Areas: A Case Study of Rural Areas in the Soutpansberg Region, Limpopo Province, South Africa

Groundwater contribution towards human health and livelihood depends on the contaminants level in groundwater. Many people in rural communities are being exposed to waterborne diseases resulting from drinking untreated contaminated groundwater. This study argues that the lack of implementation of available groundwater remediation methods and associated high costs are exposing rural communities to health risks. This study assessed 22 years of groundwater quality data from 12 boreholes and 2 springs to understand the contaminants level in the Soutpansberg region. A feasibility assessment of the application and design of a sustainable groundwater remediation technique was carried out based on individual- and community-based groundwater remediation types. The assessment considered groundwater management, cost and risk of theft and damage to infrastructure model for rural settings. This study determined that groundwater was not suitable for drinking purposes in some parts due to high concentration levels of NO3− and F−. The feasibility assessment indicated that community-based groundwater remediation schemes are more sustainable in rural areas when compared to individual household remediation. In this study, it is recommended that groundwater remediation plans must be included in any proposed water supply or drought intervention project in rural communities.

Effects of Agricultural Nutrients Influx on Water Quality in Thiba River basin, a sub-catchment of Tana River Basin in Kirinyaga County, Kenya

Excessive enrichment of waters with nutrients and the associated adverse biological effects leads to eutrophication, which is one of the major environmental problems across the world. Various studies have revealed the overuse of inorganic fertilizers to increase agricultural productivity in Kenya contributes to pollution of water bodies. In order to meet increasing demand for clean water, sustainable use and conservation of available water resources is therefore paramount. This study was done to find out effects of agricultural nutrient pollution in Thiba River, a sub-catchment of Tana River Basin, located in Kirinyaga County, Kenya. The study area was divided into four distinct agro-ecological zones based on different anthropogenic activities. Ecological survey design was used in the study. Sampling was done during the wet and dry season. Water samples were analysed for temperature, transparency, pH, electrical conductivity (EC), salinity, total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD), phosphates, nitrates, nitrites, ammonia, and toxic microalgae. All parameters showed both spatial and temporal variations with statistically significant differences (p˂0.01). Temperature of the river ranged from 14.57 0C to 28.08 0C due to climatic changes along the agro-ecological zones. The pH ranged from 7.02 to 8.51. The DO values decreased from the highlands to lowland within the range of 9.00 mg/l at the reference site to 5.43 mg/l at the most polluted site. EC ranged from 20.54 µScm-1 at the reference site during the wet season to 251.2 µScm-1 at the rice irrigation scheme site during dry season. The TDS ranged from 16.9 ppm at the reference site to 167.05 ppm at the most polluted site. Salinity also had a high variation with a range of 0.01 ppt at the reference site to 0.07 ppt at the most polluted site. The highest values of BOD (3.49 mg/l) were recorded at the rice irrigation scheme during the wet season and the lowest (0.22 mg/l) at the forest edge reference site. The lowest levels of NH4, P, NO2 and NO3 were recorded at the forest edge reference site at 1.088 µg/l, 1.177 µg/l, 0.217 µg/l and 0.148 µg/l respectively during the dry season while the highest values for the same nutrients were recorded at the rice irrigation site at 11.439 µg/l, 4.933 µg/l, 1.518 µg/l and 2.721 µg/l in the same order. There was a high peak of all nutrient levels at the rice irrigation scheme zone which was attributed to the extensive use of inorganic fertilizers. Dam water samples were analysed for members of Cyanobacteria group of microalgae which are bio-indicators of eutrophic waters. Out of the seven members of this group that were identified four were toxic genera. These were Nostoc, Oscillatoria, Anabaena and Microcystis. During the wet season Nostoc had the highest population followed by Oscillatoria and Anabaena. No Microcystis was observed during the wet season. There was a steady increase of all the genera during the dry season with Microcystis making appearance. Microcystis and Oscillatoria had a very high correlation. This study concludes that various anthropogenic activities especially agriculture along the study site are the main factors of Thiba River pollution hence a major threat to human, livestock and aquatic organisms. Environmental protection laws should be enforced by the government

Ecological Study of an Artificial Saline Lake Ecosystem in Wadi Al-Shatti, Libya

This study provided the first data related to the ecosystem of Ain Al-Mashashiya Lake. It is likely the new apperance of a saline artificial lake formed from agricultural drainage water from surounded local farms, small lakes provide an opportunity to understand intra-ecosystem connectivity and its dynamics. Water samples were collected representing two stations along edges and at the middle of the lake and other samples surrounded soil and vegetation. Lake depth was &gt; 5 meters, the pH was found to be relatively high at edge of the lake (7.46 &amp; 7.44) compared to at middle of the lake (7.38 &amp; 7.32). Highly saline water, i.e., 129.79 &amp; 125.48 dS/m &amp; 126.82 &amp; 133.74 dS/m at edge and middle of the lake respectively. The average level of PO4 and NO3 during winter is slightly lower than summer. The water cations abundances were typically Na &gt; K &gt; Ca &gt; Mg, where were for anions, Cl &gt; SO4 &gt; HCO3 &gt; PO4 &gt; NO3. The lake is valuable for biodiversity and provide habitat for many species. Five phytoplankton types have been registered, i.e., Cocconeis, Notholca Pandorina, Oscillatoria, Chlamydomonas. The most common species were Pandorina &amp; Oscillatoria. Soils of the study zone were classified as sandy loam, with a porosity of 44.53%. and saturated hydraulic conductivity (Ks) values was 4×10-3 cm/h and 6.4% of OM content. The soil reaction (pH) was 7.24 and its EC value was 19.42 dS/m that indicated high saline affected soil. The concentrations of Na, Ca &amp; Mg, were as high as 193, 48 &amp; 14.4 mg/kg, respectively, with low NO3 content 0.293 mg/kg. Tamarix (Tamarix aphylla) commonly found along the lake edges. The dry desert climate of the area played a main role in imposing the lake ecosystems.

Selective and Efficient Reduction of Nitrate to Gaseous Nitrogen from Drinking Water Source by UV/Oxalic Acid/Ferric Iron Systems: Effectiveness and Mechanisms

Nitrate (NO3−) reduction in water has been receiving increasing attention in water treatment due to its carcinogenic and endocrine-disrupting properties. This study employs a novel advanced reduction process, the UV/oxalic acid/ferric iron systems (UV/C2O42−/Fe3+ systems), in reducing NO3− due to its high reduction efficiency, excellent selectivity, and low treatment cost. The UV/C2O42−/Fe3+ process reduced NO3− with pseudo-first-order reaction rate constants of 0.0150 ± 0.0013 min−1, minimizing 91.4% of 60 mg/L NO3− and reaching 84.2% of selectivity for gaseous nitrogen after 180 min at pHini. 7.0 and 0.5 mg/L dissolved oxygen (DO). Carbon dioxide radical anion (CO2•−) played a predominant role in reducing NO3−. Gaseous nitrogen and NH4+, as well as CO2, were the main nitrogen- and carbon-containing products, respectively, and reduction pathways were proposed accordingly. A suitable level of oxalic acids (3 mM) and NO3− (60 mg/L) was recommended; increasing initial iron concentrations and UV intensity increased NO3− reduction. Instead, increasing the solution pH decreased the reduction, and 0.5–8.0 mg/L DO negligibly affected the process. Moreover, UV/C2O42−/Fe3+ systems were not retarded by 0.1–10 mM SO42− or Cl− or 0.1–1.0 mM HCO3− but were prohibited by 10 mM HCO3− and 30 mg-C/L humic acids. There was a lower reduction of NO3− in simulated groundwater (72.8%) than deionized water after 180 min at pHini. 7.0 and 0.5 mg/L DO, which meets the drinking water standard (&lt;10 mg/L N-NO3−). Therefore, UV/C2O42−/Fe3+ systems are promising approaches to selectively and efficiently reduce NO3− in drinking water.

Combined inorganic nitrogen sources influence the release of extracellular compounds that drive mutualistic interactions in microalgal‒bacterial co-cultures

We investigated the role of extracellular metabolites released during mutualistic interactions in co-cultures of a microalga, Tetradesmus obliquus IS2 or Coelastrella sp. IS3, and a bacterium, Variovorax paradoxus IS1, grown with varying levels of NO3–N and NH4–N. Both NO3–N and NH4–N were added to modified Bold’s basal medium at 16:0, 12:4, 8:8; 4:12 and 0:16 molar ratios by keeping a final N:P ratio of 16:1. Monocultures of microalgae grown with nitrate alone showed enhanced growth (> twofold) than ammonium, while the bacterial strain cultured with ammonium alone exhibited a > 1.3-fold increase in growth than nitrate. Co-culturing performed higher growth at combined nitrate and ammonium supply as compared to the single cultures. The same ratio of nitrate and ammonium resulted in superior growth of microalgae (> 1.7-fold) and the bacterium (> 4.1-fold) as compared to the monocultures. Uptake of NO3–N, NH4–N and PO4–P by monocultures or co-cultures depended on the ratio of two inorganic nitrogen sources used. The composition of organic acids, amino acids and simple sugars in exudates from monocultures varied with the ratios of nitrate and ammonium in the medium. Thus, the present novel study demonstrates that the release of exudates is affected both qualitatively and quantitatively during mutualistic interactions in microalgal‒bacterial co-cultures under the impact of inorganic nitrogen sources. Our results suggest that the variables such as inorganic nitrogen sources and extracellular metabolites released need to be considered while using co-cultures for effective bioremediation of wastewaters.

Groundwater quality evaluation in relation to nitrate pollution in the Jam river basin at Nashik and Ahmednagar district, Maharashtra, India

The hydro chemical investigation was undertaken at the Jam river basin to ascertain the state of groundwater and its evaluation related to nitrate pollution. During this study, sixty (60) representative samples of the ground water were taken from the Sinnar, Sangamner and Kopargaon tehsil, bore wells and dug wells which are used for irrigation and drinking reasons and samples were analyzed during pre and post monsoon 2021. The different physicochemical parameters like pH, EC, TDS, cations viz. Ca, Mg, Na, K and anions include HCO3, CO3 , SO4 , PO4, NO3, F and Cl were determined. In the study, it was found that the samples from irrigated agricultural areas made up the majority have NO3 levels that are higher than 45 mg/l. For groundwater from irrigated land usage, the Cl- /NO3 - ratio is

Source apportionment and health risk assessment of nitrate in foothill aquifers of Western Ghats, South India

The present research reports the level of nitrate (NO3-), associated health risks and possible sources of contamination in groundwater from south India. Many samples (32%) are above or approaching the recommended level of NO3- for safe drinking water. The correlation analysis indicates different sources of NO3- contamination in different regions rather than a common origin. The isotopic measurements provide information about potential nitrogen sources contributing NO3- to the groundwater. Based on isotope analysis, the sources of NO3- in the groundwater of this region are likely to be from (a) septic sewage (b) organic nitrogen (animal and livestock excreta) (c) sewage (domestic & chemical fertilizers). Among the sample analyzed sewage, manure and septic sewage contribute 46%, 23% and 31% NO3- to groundwater. The HQ > 1 indicates non-carcinogenic health risk due to consumption of high NO3- in drinking water. Among the studied age groups, infants are exposed to higher risk than children and adults. Results indicate that groundwater of this region is polluted with NO3- due to anthropogenic activities. Continuous consumption of such water may pose serious health risk to the residents.