Total Nitrate Concentrations Research Articles

Groundwater remediation techniques around Kodungaiyur dump yard

Abstract The groundwater around the Kodungaiyur dump yard, in Tamil Nadu, India, is polluted due to the percolation of leachate from the dumpsite. This paper proposes three remedial techniques to make the groundwater drinkable for the people living near the Kodungaiyur trash yard. Twelve bore wells around the Kodungaiyur dumpsite provided water samples for which the physicochemical parameters were measured. Moderately high concentrations of Total Hardness (TH), Total Alkalinity (TA), Chloride, Sulphate, Nitrate, Sodium, and Total Dissolved Solids (TDS) are present in the groundwater around the dump yard. The Physicochemical parameters of the samples tend to deviate from the standards prescribed by WHO and BIS. Therefore, remedial measures such as solar distillation, Activated Charcoal, and the Phytoremediation process are suggested to reduce the contaminants in the groundwater. The activated charcoal removes the unpleasant color of the water completely and makes the water clear and transparent through filtration. The solar distillation process does not affect the pH value and is reduced by 4.5% in the phytoremediation technique. Similarly, the level of chlorides is reduced by 99% in solar distillation and by 56% in the phytoremediation technique. Total hardness is reduced by 89.88% in the solar still process and 56.65% in the phytoremediation technique. Sodium is reduced by 99.88% in solar still and 57.03% in the phytoremediation technique. The economical and eco-friendly nature of the suggested techniques makes it sustainable for future generations.

Removal of Per- and Polyfluoroalkyl Substances (PFAS) in fixed bed anion exchange reactors: Factors determining PFAS uptake capacity and models predicting PFAS breakthrough

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants with adverse environmental and public health effects. Anion exchange (IX) processes can effectively remove many PFAS from water. Objectives of this research were to (1) quantify the effects of PFAS structure and background water matrix constituents [dissolved organic matter (DOM) and major inorganic anions (bicarbonate, chloride, sulfate, and nitrate)] on PFAS uptake capacity of IX resins (KIX), and (2) develop models that predict PFAS breakthrough in packed bed IX columns from PFAS structure and background water matrix characteristics. Rapid small-scale column tests were conducted with two IX resins and 18 water matrices to determine breakthrough curves and KIX values for 23 PFAS. A quantitative structure-property relationship (QSPR) was developed that predicts KIX for different PFAS from a newly developed concept, the normalized chain length (NCL). NCL for each PFAS was calculated using a group contribution method, in which the contributions of PFAS structural fragments to NCL were normalized to that of -CF2-, which was assigned a value of 1.00. Relative to -CF2-, contributions of the structural fragments -O-, -CH2-, >CF-CF3, -CHF-, and -SO3H to NCL for the purposes of KIX prediction were 0.34, -1.87, 1.70, 0.00, and 3.65, respectively. DOM and nitrate adversely impacted PFAS removal, while chloride, sulfate, and bicarbonate, when added at concentrations of up to 3 meq/L above native background levels, had negligible effects on KIX. Based on the obtained water matrix effects, pseudo-single solute models were developed for the two tested IX resins, with which PFAS breakthrough curves for fixed bed IX columns can be predicted using only the NCL and the total organic carbon and nitrate concentrations of the influent water.

Growth performance of critically endangered Hypselobarbus pulchellus in biofloc system: Influence of carbon sources on immune response, enzyme and antioxidant activity

We investigated the effect of various carbon sources on the production performance of critically endangered Hypselobarbus pulchellus in biofloc system. The experimental setup comprised four biofloc treatment groups with various carbon sources (jaggery, tapioca, rice and corn flour) and a control group. Healthy early fry (0.0068 g) was randomly stocked at 100 individuals per m3 into 15 circular fibre reinforced plastic (FRP) tanks (1000 l) and raised for 90 days. All the tested carbon sources significantly influenced weight gain, weight gain (%) and specific growth rate (SGR), with the jaggery treatment displaying the best growth performance (p<0.05). Fingerling survival rates varied from 93 to 95.67% (p>0.05). Compared to the control, the biofloc groups had significantly lower concentrations of nitrogen compounds, specifically total ammonia nitrogen, nitrite and nitrate concentrations were significantly lowered (0.29, 0.35 and 1.32 mg l-1, respectively) in jaggery treatment (p<0.05). In addition, the treatment using jaggery had a higher amount of plankton biomass and an abundance of the Bacillariophyceae group (80%). All biofloc groups displayed enhanced immune and antioxidant activity compared to the control. The jaggery treatment had elevated levels of lysozyme activity than other treatments (p<0.05). Furthermore, fingerlings raised in BFT treatments had significantly higher amylase, protease and lipase activity (p<0.05). Overall, this study’s findings suggest that the addition of various carbon sources significantly improves the production performance, with jaggery as the best carbon source for critically endangered H. pulchellus fingerling production in biofloc system to ensure sustainability. Keywords: Antioxidant activity, Fingerling, Heterotrophic bacteria, Jaggery, Specific growth rate, Sustainability

Long-term contamination of decabromodiphenyl ether reduces sediment multifunctionality: Insights from nutrient cycling, microbial ecological clusters, and microbial co-occurrence patterns

Despite the widespread detection of polybrominated diphenyl ethers in aquatic ecosystems, their long-term effects on sediment multifunctionality remain unclear. Herein, a 360-day microcosm experiment was conducted to investigate how decabromodiphenyl ether (BDE-209) contamination at different levels (0.2, 2, and 20 mg/kg dry weight) affects sediment multifunctionality, focusing on carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) cycling. Results showed that BDE-209 significantly increased sediment total organic carbon, nitrate, ammonium, available phosphorus, and sulfide concentrations, but decreased sulfate. Additionally, BDE-209 significantly altered key enzyme activities related to nutrient cycling. Bacterial community dissimilarity was positively correlated with nutrient variability. Long-term BDE-209 exposure inhibited C degradation, P transport and regulation, and most N metabolic pathways, but enhanced C fixation, methanogenesis, organic P mineralization, inorganic P solubilization, and dissimilatory sulfate reduction pathways. These changes were mainly regulated by microbial ecological clusters and keystone taxa. Overall, sediment multifunctionality declined under BDE-209 stress, primarily related to microbial co-occurrence network complexity and ecological cluster diversity. Interestingly, sediment C and N cycling had greater impacts on multifunctionality than P and S cycling. This study provides crucial insights into the key factors altering multifunctionality in contaminated sediments, which will aid pollution control and mitigation in aquatic ecosystems.

Tracing nitrogen and phosphorus pollution in urban runoff: Insights from isotopic tracers and SWMM modeling

Water contamination in certain rivers during rainfall necessitates the evaluation of pollutant levels within pipelines and the identification of their sources to ensure effective pollution control. In this study, we assess pollutant concentrations during runoff from surfaces, pipelines, and channels, identify pollutant sources within pipelines, and analyze sewage leakage contributions to channel pollution in residential areas in Wuxi City, China. The results showed that the event mean concentrations of total nitrogen (TN), total phosphorus (TP), ammonium (NH4+-N), and nitrate (NO3−-N) in the drainage outlet runoff were 3.4, 1.1, 8.8, and 14.9 times higher than in impervious surface runoff. The predominant forms of nitrogen and phosphorus in runoff shift from organic to inorganic as they move from the surface to pipelines. The pipeline load and contribution were further estimated by combining water quantity calculations from the calibrated and verified Storm Water Management Model (SWMM) with measured nitrogen and phosphorus concentrations in the runoff. TN, NH4+-N, NO3−-N, and PO43--P within the pipelines accounted for 59%, 83%, 90%, and 77% of the discharge loads, respectively. The application of the Stable Isotope Analysis in R (SIAR) package (MixSIAR) revealed that the domestic sewage and soil organic N were the predominant sources of pollutants within drainage pipelines, contributing 23.7% and 32.6% of NO3−-N, respectively. Additionally, the sewage leakage accounted for 33.7% and 66.9% of NO3−-N in drainage runoff and channels, respectively. Unlike existing methods, this study quantitatively highlights the significant impact of pipeline pollutants and sewage leakage on urban river water quality, providing essential insights for developing effective strategies to mitigate non-point source water pollution.

Reduction with zinc — Impact on the determination of nitrite and nitrate ions using microfluidic paper-based analytical devices

We used a microfluidic paper-based analytical device (μPAD) to investigate the influence that zinc reduction exerts on the determination of nitrite and nitrate ions in natural water samples. The μPAD consists of layered channels for the reduction of nitrate to nitrite with zinc powder and the subsequent detection of nitrite with Griess reagent. The amount of zinc, number of layers, and reaction time for the reduction were optimized to obtain an intense signal for nitrate. Initially, the sensitivity to nitrate corresponded to 55% that of nitrite, which implied an incomplete reduction. We found, however, that zinc decreased the sensitivity to nitrite in both the μPAD and spectrophotometry. The sensitivity to nitrite was decreased by 48% in spectrophotometry and 68% in the μPAD following the reaction with zinc. One of the reasons for the decreased sensitivity is attributed to the production of ammonia, as we elucidated that both nitrite and nitrate produced ammonia via the reaction with zinc. The results suggest that the total concentration of nitrite and nitrate must be corrected by constructing a calibration curve for nitrite with zinc, in addition to developing curves for nitrate with zinc and for nitrite without zinc. Using these calibration curves, the absorbance at different concentration ratios of nitrite and nitrate ions could be reproduced via calculation using the calibration curves with zinc for nitrite and nitrate. Eventually, the developed μPAD was applied to the determination of nitrite and nitrate ions in natural water samples, and the results were compared with those using a conventional spectrophotometric method. The results of the μPAD are in good agreement with those of conventional spectrophotometry, which suggests that the μPAD is reliable for the measurement of nitrite and nitrate ions in natural water samples.

Integrated cultivation of tambaqui (Colossoma macropomum) with coriander (Coriandrum sativum L.) grown at different plant density

The present study aimed to evaluate an aquaponic bioeconomic model integrating the cultivation of tambaqui (Colossoma macropomum) with coriander (Coriandrum sativum) at different densities of 32, 72, 128, and 512 cells m−2 for 19 days. The hydroponic bed was configured on a bench with a capacity of 100 L (1.62 m-long, 0.72 m-width, and 0.1 m-depth) and was coupled to a plastic tank with the fish. The coriander seeds were irrigated for four days until germination, when they were transferred to the hydroponic beds. Two hundred forty tambaqui juveniles (113.5 ± 0.15 g and 19.6 ± 0.20 cm) were distributed in 12 tanks (1000-L capacity) in aquaponic units, totaling 20 fish per unit. The fish were fed commercial feed (36% protein and 7% lipids), and water quality variables were monitored daily. At 5, 10, and 15 days after transplanting to the hydroponic bed, the leaf number (LN) and plant height (PH, in cm) of the coriander were determined. Additionally, total fresh mass (TFM, in g), leaf fresh mass (LFM, in g), root fresh mass (RFM, in g), total dry mass (TDM, in g), leaf dry mass (LDM, in g), root dry mass (RDM, in g), leaf length (LL, in cm), root length (RL, in cm), yield of total fresh mass (YTFM, in kg m−2), and the nutritional composition of macro and micronutrients were determined, as well as fish growth performance. A density of 512 cells m−2 reduced the electrical conductivity (0.097 ± 0.001 dS m−1) of the water. The pH, dissolved oxygen, and temperature did not differ significantly between the densities. The total ammonia nitrogen (28.81 ± 2.26 mg L−1) and nitrate (51.07 ± 0.81 mg L−1) concentrations were greater at a density of 32 cells m−2. At the end of the 19-day period, the fish growth indices did not significantly differ (p > 0.05) as a function of coriander cultivation density. Density significantly influenced coriander growth. All variables (PH with root, LL, RL, LFM, TFM, LDM, TDM, RFM, RDM, and YTFM) were significantly influenced (p < 0.05) as a function of cultivation density. YTFM (1.82 ± 0.45 kg m−2), PH (30.39 ± 0.61 cm), and LL (16.62 ± 0.53 cm) were significantly higher (p < 0.05) at a density of 512 cells m−2. RL was significantly higher (p < 0.05) at densities of 72 and 32 cells m−2, of the order of 15.98 ± 0.43 and 18.79 ± 1.01 cm, respectively. Boron was significantly greater at a density of 512 cells m−2 (39.70 ± 1.04 mg kg−1) than at 32 cells m−2 (29.93 ± 4.66 mg kg−1). Similarly, sodium was significantly more abundant at a density of 512 cells m−2 (5975.54 ± 783.82 mg kg−1) when compared to the densities of 128 and 72 cells m−2, which were 4179.97 ± 287.31 and 3760.60 ± 224.31 mg kg−1, respectively. Aquaponic production in the equatorial Amazon region accelerated, and the optimal density for coriander integrated with tambaqui without compromising plant growth performance was 128 cells m−2.

Chronic exposure to drinking water nitrate and trihalomethanes in the French CONSTANCES cohort

Trihalomethanes (THMs) and nitrate are widespread chemicals in drinking water. Chronic exposure has been associated with increased cancer risk despite inconclusive evidence, partly due to the challenges in long-term exposure assessment and potential exposure misclassification.We estimated concentrations of nitrate and THMs in drinking water using a public regulatory monitoring database (SISE-Eaux) for CONSTANCES, a French population-based prospective cohort.We obtained 26,322,366 measurements of drinking water parameters from 2000 to 2020. We excluded missing, implausible and duplicated measurements; we corrected or imputed missing geocodes of sampling locations; we calculated the annual median concentration of nitrate and THMs by surveillance area. To predict missing annual median concentrations, linear mixed models with random intercept using surveillance area as a clustering variable were developed for each region for nitrate and the four THM components (chloroform, chlorodibromomethane, bromodichloromethane and bromoform) separately. Concentrations in the nearest surveillance area from the household were merged per year among 75,462 participants with residential history geocoded for 2000–2020. Estimated concentrations resulting from this approach were compared with measured concentrations in 100 samples collected in Paris, Rennes and Saint-Brieuc in 2021.Median annual concentrations of total THMs and nitrate at study participants’ homes for 2000–2020 were, respectively, 15.7 μg/l (IQR: 15.2) and 15.2 mg/l (IQR: 20.8). Among these, 35% were based on measurements for nitrate (16% for THMs), 44% (46%) were predicted using on linear mixed models, and 21% (38%) were based on distribution unit median values. Conditional R2 predictive models ranged from 0.71 to 0.91 (median: 0.85) for nitrate, and from 0.48 to 0.80 for THMs (median: 0.68).These concentrations will allow future association analyses with risk of breast and colorectal cancer. Our cleaning process introduced here could be adapted to other large drinking water monitoring data.

Total Nitrite and Nitrate Concentration in Human Milk and Saliva during the First 60 Days Postpartum-A Pilot Study.

Nitric oxide (NO) in human milk may have important functions in lactation and infant health. This longitudinal pilot cohort study investigated the total nitrite and nitrate (NOx) concentration in human milk and maternal saliva during the first 60 days postpartum. Additionally, we explored the association between selected breastfeeding variables and milk and saliva NOx concentration. Human milk and maternal saliva samples were collected on days 2, 5, 14, 30, and 60 postpartum and analyzed for NOx concentration. Breastfeeding data were collected through self-assessed questions. Data analyses were performed using mixed models. The concentration of NOx in milk was significantly higher during the first 30 days compared to day 60, and there was a positive association between milk and saliva NOx concentrations throughout the entire study period. In absolute numbers, partially breastfeeding mothers had a lower concentration of NOx in milk on day 2 compared to exclusively breastfeeding mothers (8 vs. 15.1 μM, respectively). Partially breastfeeding mothers reported a later start of secretory activation and fewer mothers in this group started breastfeeding within the first hour after birth. Due to the small numbers, these differences could not be statistically evaluated. Further research is warranted to elucidate the role of NO in lactation success and breastfeeding outcomes.

Bacterial Community Characteristics and Roles in Nitrogen Transformation in Industrial Farming Systems of Litopenaeus vannamei

Industrial farming is one of the main farming systems used for L. vannamei, and it is also the main direction of development in the future. To investigate the role of the bacterial community in nitrogen transformation in industrial L. vannamei farming systems, we studied the concentration of nitrogen compounds, the bacterial community using 16S rRNA sequencing, and nitrogen cycling genes’ abundance using absolute quantitative PCR in aquaculture water (using seawater (WD) and groundwater mixed with seawater (CY)) and analyzed the correlations between them using a person analysis. The results showed that the bacterial α-diversity index (ACE, Shannon, and Sobs) significantly changed during culture in WD but not in CY. Bacterial community species composition analysis and linear discriminant analysis effect size (LEfSe analysis) revealed that Cyanobiaceae and Microbacteriaceae were the dominant bacteria and biomarkers in WD. Vibrionaceae, Ateromonadaceae, Microbacteriaceae, Saprospiraceae, and Cryomorphaceae were the dominant bacteria and biomarkers in CY. A functional annotation of procaryotic taxa (FAPROTAX) analysis revealed that the bacterial community in WD exhibited a greater phototrophic activity at early culture stages, while at the same stage, CY exhibited strong nitrate reduction. A correlation analysis of nitrogen cycling genes and environmental factors revealed that napA, narG, ureC, amoA, and nirK were significantly correlated with the concentrations of total ammonia nitrogen (TAN), nitrite (NO2−-N), nitrate (NO3−-N), and total nitrogen (TN) in WD. In CY, amoA was positively correlated and napA and nirK were negatively correlated with TAN and TN concentrations. A correlation analysis between bacterial abundance and environmental factors revealed that Flavobacteriaceae, Saprospiraceae, Cryomorphaceae, Cyanobiaceae, Halieaceae, and Cyclobacteriaceae were significantly correlated with the concentrations of TAN and NO2−-N. The above results indicated that the bacterial community in industrial shrimp farming systems changed under different conditions, with consequent changes in the abundance of genes being involved in the nitrogen cycle and in this biogeochemical process in the water. Our study facilitates further understanding of microbes and their functions in nitrogen cycling in industrial shrimp farming systems.

Comparing Nitric Oxide Generation Pathways using Dietary L-Arginine and Dietary Nitrate: A 15N tracer study in Wistar Rats

Mammals generate nitric oxide (NO) through two main pathways. In the direct production pathway, endogenous nitric oxide synthase (NOS) enzymes catalyze the reaction of L-arginine with oxygen, producing nitric oxide and citrulline. When oxygen accessibility is low, the reductive pathway supplies nitric oxide through the nitrate-nitrite-NO reduction cascade. Additional research is needed to understand whether the two NO generation pathways interact and what effects the two pathways have on the body and each other. We investigated how dietary supplementation of 15N-L-arginine (0.5 g/kg), 15N-nitrate (0.013 g/kg), or a combination of L-arginine and nitrate influences nitrate concentrations in plasma, skeletal muscle, and liver tissue from Wistar rats. We administered treatments via oral gavage. Two hours after treatment administration, we euthanized the rats and collected tissue samples. The nitrate concentrations were measured using chemiluminescence, and future mass spectrometry analysis for 15N/14N ratios will be performed. The calculated concentrations were compared between treatment groups using single factor analysis of variance. Firstly, we observed that nitrate administration significantly increased total nitrate levels in plasma, liver, and muscle tissues compared to the control group. Interestingly, L-arginine alone did not result in a significant rise in total nitrate concentrations. Notably, liver tissue from the L-arginine-treated group had slightly lower concentrations of nitrate than the control group. The combination of L-arginine and nitrate showed no statistically significant difference when compared with the nitrate-treated group in all three tissues. These results suggest that a bolus of L-arginine does not have a substantial short-term effect (within 2 hours after ingestion) on total nitrate concentrations in rat tissues. Future mass spectrometry analysis will indicate how the tissues handle acute ingestion of two different NO sources: L-arginine and nitrate. Further research must be performed for a more detailed understanding of the kinetics of arginine and nitrate, as well as for the effects of these dietary supplements on improving NO homeostasis. This work was supported by intramural NIDDK/NIH grant ZIA DK 025104-15 to Alan N. Schechter. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Spatio-Temporal Variations in Nitrate Sources and Transformations in the Midstream of the Yellow River Determined Based on Nitrate Isotopes and Hydrochemical Compositions

Nitrate pollution is a major environmental problem threatening rivers, and nitrogen and oxygen isotopes have proved to be an effective means of analyzing the sources and transformations of nitrate in rivers. However, a low monitoring frequency cannot accurately reflect the changes in nitrate. In this study, the sources and transformations of nitrate in the middle reaches of the Yellow River and its tributaries during the dry season and the wet season were analyzed based on water quality parameters and nitrate isotopes. Stable isotope analysis conducted using the R (SIAR) model was used to estimate the proportions of different nitrate sources. The results showed that the main nitrate sources in the main stream were soil nitrogen (40.95–45.83%) and domestic sewage and manure (30.93–32.60%), respectively, with little variation between the dry season and wet season because of the large flow of the Yellow River. During the dry season, the nitrate sources of the two tributaries were mainly domestic sewage and manure (45.23–47.40%), followed by soil nitrogen (31.35–34.00%). However, the primary nitrate source of T2 (Qin River) became soil nitrogen (40.05%) during the wet season, a phenomenon that was mainly caused by the significant increase in river discharge and in soil erosion in the basin. During the wet season, the concentrations of total nitrogen (TN) and nitrate (NO3−) significantly decreased in the main stream and tributaries, and nitrification and denitrification processes occurred in both the main stream and tributaries of the Yellow River. In addition, the T2 tributary (Qin River) was also significantly affected by mixed dilution. High-frequency sampling can reflect the isotopic information of nitrate in the river more comprehensively, which helps us to understand the conversion process of nitrate more accurately.

Spatial and temporal distribution of nutrients in the Ciliwung River, DKI Jakarta

The Ciliwung River, one of the largest rivers to run through Jakarta, is particularly important for its water quality because it travels through the city’s center and several settlements, highly populated housing areas, and slums. The growth of algae and macrophytes, or aquatic plants, is dependent on the nutrients in the streams. These plants serve as major food sources for fish and other small invertebrates. This study aimed to describe the distribution of nutrients (ammonia, nitrite, nitrate, total nitrogen, and total phosphate) in the Ciliwung River, DKI Jakarta, in terms of both space and time. Water quality was monitored under rainy (February and June 2021) and dry (August and September 2021) conditions. The research area, which included 18 observation stations, was situated in the DKI Jakarta sector along the Ciliwung River. Geographically, all river regions’ concentrations of total nitrogen, nitrate, and total phosphate exceeded the quality criteria; however, ammonia and nitrite tended to be high and did not meet norms across the Ciliwung River area, DKI Jakarta. While ammonia concentrations were greater during the dry season and nitrate concentrations were higher during the rainy season, there was a temporary difference in the concentrations of nitrite, total nitrogen, and total phosphate between the seasons.

Influence of Nutrient Solutions in an NGS® Soilless System on the Yield, Quality and Shelf Life of Fresh-Cut Commercial Mint at Different Harvest Times

The optimal fertilizer concentration for Mentha plants is contingent on the growing systems and harvest time, serving as operational solutions to control and enhance quality and yield. This study aimed to determine the effects of three macronutrients concentration in hydroponic nutrient solution (HNS) during three harvest times on the growth, quality, yield, and shelf life of three mint species (M. spicata L. var. viridis (MV); M. piperita L. (MP); M. spicata L. var. rubra (MR)) grown in a New Growing System (NGS®). Total dry matter (DM), nitrate (NO3−), phosphate (PO43−), and calcium carbonate (CaCO3) concentrations were increased with the addition of higher levels of nutrient fertilization in three species. When the ion concentration of the HNS was increased, total fresh yield decreased. The highest total bacterial count (TBC) was obtained in MR species in the three harvests in all the levels of HNS. The lowest browning potential (BP) and soluble o-quinone (So-Q) levels were observed at second harvest in the MR species with the application of one of the two HNS high in nitrogen (N). In conclusion, the combination of optimal HNS ion concentration and appropriate species is considered essential to obtain suitable yield, quality, and ensure shelf life of mint.

Two-stage leaching of calcium and vanadium from high-calcium steelmaking slag

ABSTRACT Vanadium (V) is a critically important element in many industries. A widely used recovery process is a combination of roasting and leaching. However, roasting is an energy-intensive stage. Generally, basic oxygen furnace (BOF) slag is high in calcium (Ca) but low in V. Ca content and its chemical nature can prevent V leaching. This study presents a potential two-stage leaching process for Ca and V from BOF slag. The method is environmentally friendly using low temperatures and enabling leachate recycling. Furthermore, the utilisation rate of the slag can be higher due to Ca recovery. Ca is first leached using ammonium nitrate and nitric acid solution. The V-containing residue is directed to the second stage, where V is leached using ammonium carbonate ((NH4)2CO3). Ca leaching efficiency was 71% achieved with a low temperature (40°C) and in 20 min. > 99% of the dissolved element was Ca. Increasing the total nitrate concentration increased the leaching efficiency. Reducing the L/S ratio improved selectivity. The solid material was analysed after the leaching stages and a clear change was observed after the Ca-stage. The V leaching efficiency was 50%. > 88% of dissolved element was V (L/S 8, [(NH4)2CO3] 200 g/L, 60°C, and 60 min). Increasing [(NH4)2CO3] and L/S ratio slightly improved the leaching efficiency but decreased selectivity. The studied process implements circular economy principles and has been developed for side streams with low V concentrations. However, further optimisation and developments are required regarding the effectiveness of the process.

Land cover, stream discharge, and wastewater effluent impacts on baseflow sediment and nutrient concentrations in SW Ohio streams

AbstractElevated nutrient and suspended sediment concentrations often result in negative environmental impacts within freshwater environments. Studies that directly compare suspended sediment and bioavailable nutrients between predominantly agricultural and predominantly urban watersheds during baseflow conditions are largely lacking. The purpose of this study was to determine the impacts of land cover, stream discharge, and wastewater treatment plant (WWTP) discharge on nutrient and sediment concentrations, across a large land cover gradient in Southwest Ohio streams. Weekly baseflow samples were collected from eight streams over 1 year from November, 2016 through November, 2017. Total suspended sediment, nitrate, and phosphate concentrations were measured. Results indicate that agricultural land cover and WWTPs increase nitrate and phosphate concentrations in the study area. Total suspended sediment and nitrate concentrations increased with discharge, and discharge was a relatively weak predictor of phosphate concentrations. Seasonal water quality trends varied by parameter and land use also had unique impacts on seasonal water quality trends. Results suggest that to improve water quality in the study area, efforts should focus on improving WWTP effluent treatment and agricultural land management.

Ecological evolution of algae in connected reservoirs under the influence of water transfer: Algal density, community structure, and assembly processes

Reservoir connectivity provides a solution for regional water shortages. Understanding the water quality of reservoirs and the response of algal communities to water transfer could provide the basis for a long-term evolutionary model of reservoirs. In this study, a water-algal community model was established to study the effects of water transfer on water quality and algal communities in reservoirs. The results showed that water transfer significantly decreased total nitrogen and nitrate concentrations. However, the water transfer resulted in an increase in the CODMn concentration and conductivity in the receiving reservoir. Additionally, the algal density and chlorophyll-a (chl-a) concentration showed an increase with water transfer. Bacillariophyta, Cyanophyta, and Chlorophyta were the dominant algal phyllum in all three reservoirs. Water transfer induced the evolution of the algal community by driving changes in the chemical parameters of the receiving reservoir and led to more complex relationships within the algal community. The effects of stochastic processes on algal communities were also enhanced in the receiving reservoirs. These results provide specific information for water quality safety management and eutrophication prevention in connected reservoirs.

Particulate-bound alkyl nitrate pollution and formation mechanisms in Beijing, China

Abstract. Fine particulate matter (PM2.5) samples were collected between November 2020 and October 2021 at the Minzu University of China in Beijing, and the n-alkyl nitrate concentrations in the PM2.5 samples were determined to investigate n-alkyl nitrate pollution and formation mechanisms. C9–C16 n-alkyl nitrate standards were synthesized, and the n-alkyl nitrate concentrations in PM2.5 were determined by gas chromatography triple quadrupole mass spectrometry. Temporal trends in and correlations between particulate-bound n-alkyl nitrate, ozone, PM2.5, and nitrogen dioxide concentrations were investigated to assess the relationships between particulate-bound n-alkyl nitrate concentrations and gas-phase homogeneous reactions in the photochemical process and speculate the particulate-bound n-alkyl nitrates' formation mechanisms. The n-alkyl nitrate concentrations in the PM2.5 samples were 9.67–2730 pg m−3, and the mean was 578 pg m−3. The n-alkyl nitrate homologue group concentrations increased as the carbon chain length increased; i.e., long-chain n-alkyl nitrates contributed more than short-chain n-alkyl nitrates to the total n-alkyl nitrate concentrations in PM2.5. The n-alkyl nitrate concentrations clearly varied seasonally and diurnally, the concentrations decreasing in the order winter &gt; spring &gt; autumn &gt; summer and the mean concentrations being higher at night than in the day. The particulate-bound n-alkyl nitrate and ozone concentrations significantly negatively correlated despite gas-phase alkyl nitrate and ozone concentrations previously being found to positively correlate. This indicated that long-chain alkyl nitrates may not be produced during gas-phase homogeneous reactions. The particulate-bound n-alkyl nitrate concentrations followed the same trends as and significantly positively correlated with the PM2.5 and nitrogen dioxide concentrations. Nitrogen dioxide is an important contributor of nitrates in particulate matter. This indicated that particulate-bound n-alkyl nitrates may form through non-homogeneous reactions between alkanes and nitrates on particulate matter surfaces. As secondary pollutants, particulate-bound alkyl nitrates are important components of PM2.5 during haze events and strongly affect haze pollution and atmospheric visibility.

Growth, Biomass Production, Pollutant Removal Capacity of Chlorella Vulgaris Cultivated in Water Polluted with Phosphates, Nitrates, Cadmium and Lead Ions; A Possible Strategy for Bioremediation, Carbon Dioxide Utilization and Simultaneous Biodiesel Productivity

The main objective of the work reported herein was to study the possibility of simultaneous use of microalgae for bioremediation and biodiesel production. Determination of optimum nitrate and phosphate concentrations for the maximum algal growth in the presence of heavy metal ions in the growth media was the other objective. In this regard, Chlorellavulgaris, a microalga, was cultivated separately for 30 days at ~28 °C in the presence and absence of known cadmium, lead, phosphate ion concentrations in growth media containing an optimum nitrate ion concentration. The concentrations of these ions in the growth media, dry algal biomass and extractable algal-oil percentage after 30 days of their growth were determined. According to the study, the optimum total nitrate and total phosphate concentrations required for the maximum algal growth were 200 mg L-1 and 10 mg L-1, respectively. The maximum tolerable Pb2+ and Cd2+ concentrations were 8 mg L-1 and 2.5 mg L-1, respectively. The results revealed that Chlorellavulgaris has a high capacity for both removing these ions (&gt; 70%) from the growth medium, and generating algal biomass, simultaneously. Moreover, the algal biomass generated under these harsh conditions yields algal-oil (~41% in terms of dry algal biomass) that is free from these ions.

Legacy of salmon-derived nutrients on riparian soil chemistry and soil fertility on the Central Coast of British Columbia, Canada

Every year, salmon return to their natal streams to spawn. Their return represents an ecosystem subsidy of nutrients and energy from the sea to the land; these materials feed into terrestrial food webs, plant communities, and forest soils. Here we test the long term effects of salmon inputs on soil fertility by sampling soils from Haíɫzaqv (Heiltsuk) Nation territory on the Central Coast of British Columbia, Canada. A total of 20 soil chemical properties were assessed via two sampling methodologies: first, across 23 watersheds representing a regional gradient of salmon density (kg of salmon per meter of stream reach per year); and second, at four sites above and below waterfalls that blocked salmon migration. At each sampling point, soil material at two depths was collected. Multivariate analysis regional gradient showed salmon density, the moss community, and the shrub community to be significant factors related to soil chemistry. Similarly, being above or below the waterfall, the moss community, and the tree community were significant in the waterfall comparison. Generalized linear mixed models along regional salmon density gradient showed an increase in nitrate (NO3−) correlated with salmon inputs (p &amp;lt; 0.05), and moderately significant (p &amp;lt; 0.1) increases in ammonium (NH4+), phosphorus (P), aluminum (Al), and copper (Cu). Net cation exchange capacity (CEC) did not change; however, magnesium (Mg) significantly decreased along these gradients (p &amp;lt; 0.05), while sodium (Na) had a declining tendency and calcium (Ca) had an increasing tendency. Being below salmon-blocking waterfalls or the salmon density below falls was a factor in higher total nitrogen, nitrate, ammonium, phosphorus, total sulfur (S), magnesium, and sodium concentrations; below falls sites also had lower pH and aluminum. Exploratory analysis of the regional gradient data using a random forest model apportioned high importance to soil depth, the moss community, the shrub community, salmon density and distance from the stream. These results show that salmon inputs are correlated with a number of changes in recipient soils, and these are consistent with an interpretation of improved fertility at these sites.