High Nitrate Concentrations Research Articles

Concurrent elimination of arsenic and nitrate from aqueous environments through a novel nanocomposite: Fe3O4-ZIF8@eggshell membrane matrix

The high concentration of nitrate and arsenic as potentially toxic elements (PTEs) with carcinogenic properties in many groundwater sources worldwide is a concern for health and the environment. This work checked the capacity of a novel nanocomposite, Fe3O4-ZIF8@eggshell membrane matrix (F-ZIF8@EMM) for concurrently eliminating arsenic and nitrate, two of the most encountered hazardous pollutants in drinking water. Contact time (30–120 min), pH (3–10), initial arsenic concentration (25–100 μg/L), initial nitrate concentration (60–120 mg/L) and adsorbent dose (0.25–5 mg/L) as various operating influences were investigated on the co-adsorption of arsenic and nitrate from water by a new nanocomposite thru diverse experimental tests. Characteristics of F-ZIF8@EMM were determined through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) analyses. Taguchi model was used to determine the optimal co-adsorption conditions. The results revealed that the optimal conditions for the simultaneous adsorption of 94.32 % of these two elements were at pH = 7, adsorbent dose 1 mg/L, primary nitrate concentration 120 mg/L, initial arsenic concentration 100 μg/L, and contact time 90 min. Correspondingly, the simultaneous adsorption of arsenic and nitrate best fit the Langmuir isotherm, and the pseudo-second-order (PSO) model was the best model that fitted with experimental kinetic data (R2 = 1). The maximum experimental adsorption capacity of F-ZIF8@EMM was 128.5 mg/g. This study indicated that the efficiency of nanocomposite F-ZIF8@EMM in the co-adsorption of arsenic and nitrate was promising.

Evaluating Biocompounds in Discarded Beetroot (Beta vulgaris) Leaves and Stems for Sustainable Food Processing Solutions.

The current trend focuses on reducing food waste, with scientific studies exploring the nutritional value of discarded food components to identify potential health benefits. Beetroot (Beta vulgaris L.) is highly consumed, but its stems and leaves are often discarded. This work aims to characterize the chemical properties and bioactive compounds in beet stems and leaves and assess their applicability in food products. The stems and leaves were subjected to different drying temperatures (50 to 70 °C) to determine the optimal temperature for preserving their bioactive compounds. They are then nutritionally and physiochemically characterized and incorporated into a food matrix. The optimal drying temperature was 60 °C. The leaves and stems contain approximately 30 and 15 g/100 g of protein, 30 and 32 g/100 g of dietary fiber, 4 and 0.45 g/100 g of lipids, and 24 and 25 g/100 g of ash, respectively. Both provide approximately 50% of the amino acid requirements established by the WHO/FAO/UNU and are rich in iron and potassium. The stems presented 53% more betalainic compounds (0.58 mg/g) and a higher nitrate content (359 mg/kg) than did the leaves, which presented a higher polyphenol content. The incorporation of flour from beet stems and leaves into food products is economical, reduces food waste, and enhances nutrition and health.

Novel Nanocatalysts for Simultaneous Ammonia Oxidation and Nitrate Reduction

Throughout recent years, nitrate reduction to ammonia has gained popularity in the scientific world to produce a carbon-free fuel [1]. However, research has primarily focused on low-concentration nitrate reduction, specifically for wastewater remediation. High-concentration effluents, such as ANSOL (Ammonium Nitrate), have emerged as a significant waste byproduct and a threat [2], with explosive characteristics and increasing production rates over the years [3]. This research seeks solutions to incorporate onsite waste treatment for generating electrical power, emphasizing the integration of waste streams as a distinctive opportunity. The integration aims to facilitate both power generation and the provision of clean water, with a focus on developing prototype systems designed to convert challenging Department of Defense (DoD) waste streams containing ANSOL into usable fuels for onsite energy generation.In this presentation, results from two distinct systems employing nanoparticle catalysts for the reduction of nitrates to ammonia, while simultaneously oxidizing ammonia to nitrogen and hydrogen, are discussed. This is particularly relevant in the presence of a high concentration of ammonium nitrate in waste (>0.5 M) with industrially relevant electrochemical performance (>300 mA/cm2 with Faradaic Efficiencies higher than 50%). The initial approach involves the integration of CuNi/C and Pt3Ir/C catalysts for reduction and oxidation, respectively [4]. The subsequent approach underscores pulsed electrodeposition of CuNi [5] for nanoparticle synthesis in the reduction process, coupled with the use of Pt3Ir/C catalyst for oxidation. The effect of different applied potentials was studied for the conversion of NO3 - to NH3 and subsequent H2 production. Electrode stability and process integration were investigated.[1] Kani, N. C., Nguyen, N. H. L., Markel, K., Bhawnani, R. R., Shindel, B., Sharma, K., Kim, S., Dravid, V. P., Berry, V., Gauthier, J. A., Singh, M. R., “Electrochemical Reduction of Nitrates on CoO Nanoclusters-Functionalized Graphene with Highest Mass Activity and Nearly 100% Selectivity to Ammonia,” Adv. Energy Mater. 2023, 13, 2204236.[2] United States Occupational Safety and Health Administration, Bureau of Alcohol, Tobacco, Firearms and Explosives, Environmental Protection Agency, "Chemical Advisory: Safe Storage, Handling, and Management of Solid Ammonium Nitrate Prills," EPA 550-F-15-001, June 2015.[3] Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESTCP), "Conversion of Ammonium Nitrate Solutions to Useful Products," SERDP and ESTCP Website, April 5, 2021. [Online].[4] Hariri, M.B., and Botte, G.G., "Simultaneous Removal of Ammonia and Nitrate from Wastewater Using a Pulse Electrolysis Technique," Journal of The Electrochemical Society 170.5. 2023.[5] I. Baskaran, T.S.N. Sankara Narayanan, and A. Stephen, "Pulsed electrodeposition of nanocrystalline Cu–Ni alloy films and evaluation of their characteristic properties," Materials Letters, vol. 60, no. 16, pp. 1990-1995, July 2006.

Electrochemical treatment of 4-chlorophenol by three-dimensional electrode reactors packed with plastic particles electrodes

The three-dimensional electrode reactors (TDER) filled with surface-modified plastic particles electrodes, was much more effective on electrolyzing 4-chlorophenol wastewater than by conventional electrolysis. The experimental results indicated that about 96.8 % of 4-chorophenol was degraded effectively, it was possibly decomposed into aromatic organic compounds and small-molecular organic acids by hydroxyl radicals generated on the surfaces of electrodes, and the biodegradability of treated 4-chlorophenol wastewater was also much more improved than that of the untreated, which would be more easily biologically degraded by the subsequent conventional activated sludge process. Furthermore, the 4-chorophenol wastewater could be co-degraded with high-concentration nitrate effectively, both 2-chlorophenol and 2,4-dichorophenol wastewaters were also similarly decomposed.

Modulation of soil nitrous oxide emissions and nitrogen leaching by hillslope hydrological processes

Soil nitrous oxide (N2O) emissions and nitrogen (N) leaching are key pathways for soil N loss in hillslope ecosystem, with potential implications for global warming and water body eutrophication. While soil N loss in hillslope ecosystem has been extensively studied, there is limited understanding of the spatiotemporal distribution patterns and factors driving soil N2O emissions and N leaching from a hillslope hydrology perspective. This study investigated N concentrations in leachate and soil N2O fluxes and their responses to soil hydrological factors on a tea plantation (TP) hillslope and a bamboo forest (BF) hillslope. Four distinct precipitation patterns—spring rainfall (SR), plum rain (PR), summer flood rain (SF), and drought period (DR)—were identified based on precipitation intensity, duration, and cumulative precipitation. Results showed that, soil N2O flux and leachate N concentrations were 8.2 times and 18.0 times higher On TP hillslope compared to the BF hillslope. The greatest soil N2O fluxes occurred during the PR period, while the lowest were observed during the DR period. Precipitation increased soil water content (SWC) and water-filled pore space, stimulating soil N cycling for N2O production. Fertilization activities and precipitation led to peak N concentration in leachate during the SR period. Additionally, soil wetness index (SWI) shaped spatial patterns of SWC, resulting in distinct spatial patterns of N2O emissions and nitrate leaching. Locations with higher SWI exhibited greater soil N2O flux and higher nitrate concentrations in leachate. This study emphasizes the significant effect of soil hydrological processes on soil N2O emissions and N leaching in hillslope ecosystems, providing valuable insights for N management in these environments.

Sustainable catalytic hydrogenation of high concentration nitrate to ammonia over Ruthenium-based catalysts

Elevated nitrate levels in natural water bodies significantly disrupt the global nitrogen cycle and pose a substantial environmental and human health risk. This study investigates the selective conversion of nitrate to ammonia via catalytic hydrogenation. This highly efficient and selective process offers a sustainable alternative to traditional ammonia production methods while simultaneously addressing nitrate pollution. Ruthenium (Ru) catalysts supported on ceria (CeO2), titania (TiO2), and tin dioxide (SnO2) were synthesized using a simple impregnation method, incorporating oxygen vacancies and low Palladium (Pd) loadings (0.25–0.5 wt%) to enhance catalytic performance. Ru-Pd/CeO2 exhibited superior activity and selectivity, maintaining near 100 % ammonia selectivity across various nitrate concentrations. At 75 °C, complete conversion of 2000 ppm nitrate to ammonia was achieved within 80 min using Ru-Pd/CeO2, and the yield of ammonia can reach up to 16440 mg•h−1•gRu-1. Subsequent ammonia enrichment through evaporation yielded pure ammonia solutions up to 3.6 wt%. Characterization and theoretical calculations suggest that abundant oxygen vacancies on the CeO2 surface and efficient hydrogen spillover from Pd nanoparticles synergistically contribute to the Ru-Pd/CeO2 catalyst’s superior performance. The catalyst exhibited excellent stability and reusability, maintaining high activity and selectivity over four cycles. This research presents a promising strategy for addressing nitrate pollution in water bodies while offering a sustainable and environmentally friendly route for ammonia synthesis. The findings of this study lay the foundation for further advancing and potentially implementing catalytic hydrogenation technology for nitrate pollution remediation and ammonia synthesis.

Bioremediation of Nitrate and Nitrite on the Rehabilitation of Contaminated Jatibarang Landfill and the Application of Calla Lily

Currently, waste processing is a problem because it is not yet optimal. The high content of nitrates and nitrites results in environmental pollution which can cause losses because it affects health and biodiversity. One effort to control environmental pollution is phytoremediation using calla lily (Zantedeschia aethiopica) to remediate nitrate and nitrite levels that do not comply with quality standards so that pollution can be minimized. This research aims to determine the effectiveness of calla lily as a phytoremediation agent for landfill leachate nitrate and nitrite. This experimental research method uses a Completely Randomized Design (CRD) which consists of three treatment levels, namely variations in calla lily biomass of 0 grams, 200 grams, and 400 grams with 3 repetitions, and measurements of nitrate and nitrite levels are carried out on day 1, day 2. 3, and 7. The results showed that the most optimal percentage reduction in leachate nitrate levels occurred in the P1 on the day 7, namely 45%, while the most optimal percentage reduction in leachate nitrite levels occurred in the P1 on the day 7, it was 53%. The final nitrate content after the research was in accordance with the quality standards of PP RI No.22 of 2021, while the leachate nitrite content after treatment still exceeded the quality standards of PP RI No.22 of 2021. Calla lily has the potential to reduce nitrate and nitrite levels due to landfill leachate pollution.

Removal of calcium from phosphoric acid produced by the nitric acid process using solvent extraction with TCHDGA and stripping with water

The phosphoric acid produced by the nitric acid method cannot be used as an industrial-grade product as a result of the high calcium nitrate content. It can only be used for fertilizer production due to difficulty of complete removal of calcium nitrate. Herein, an efficient approach for the removal of calcium nitrate from the phosphoric acid produced by the nitric acid process was studied. The proposed process is based on solvent extraction with N, N, N′, N′-tetracyclohexyl-3-oxyglutaramide (TCHDGA). The effects of time, diluent, temperature, impurity ions, and the concentrations of extractant and nitric acid on the extraction of Ca2+ were considered. A series of characterization tests involving FT-IR spectroscopy, XPS analysis, slope analysis and X-ray single crystal diffracted analysis revealed that the stoichiometry of the complex is (Ca(NO3)2)(TCHDGA)3. The concentration of Ca2+ in phosphoric acid drops below 5 mg/L a three-stage cross-current extraction process. The stripping efficiency of calcium nitrate in the organic phase by water is above 99.9%. The extraction efficiency of Ca2+ by TCHDGA remained above 96.8% after ten extraction-stripping cycles, realizing the efficient removal of calcium nitrate in the phosphoric acid produced by nitric acid process without changing the traditional production conditions.

Variations in photoperiods and their impact on yield, photosynthesis and secondary metabolite production in basil microgreens

BackgroundThe effects of different photoperiods on plant phytochemical synthesis can be improved by adjusting the daily light integral. Photoperiod is one of the most important environmental factors that control growth, plant’s internal rhythm and the synthesis of secondary metabolites. Information about the appropriate standard in terms of photoperiod for growing basil microgreens as one of the most important medicinal plants is limited. In this study, the effects of five different photoperiods, 6 (6 h × 3 cycles), 8 (8 h × 2 cycles), 16, 18, and 24 h day− 1 on the yield, photosynthesis and synthesis of secondary metabolites of three cultivars and one genotype of basil microgreens in floating system were evaluated. The purpose of this research was to determine the feasibility of using permanent light in growing basil microgreens and to create the best balance between beneficial secondary metabolites and performance.ResultsThe results showed that the effects of photoperiod and cultivar on all investigated traits and their interaction on photosynthetic pigments, antioxidant capacity, total phenolic compounds, proline content and net photosynthesis rate were significantly different at the 1% level. The highest levels of vitamin C, flavonoids, anthocyanins, yield and antioxidant potential composite index (APCI) were obtained under the 24-h photoperiod. The highest antioxidant capacity was obtained for the Kapoor cultivar, and the highest total phenolic compound and proline contents were measured for the Ablagh genotype under a 24-h photoperiod. The highest yield (4.36 kg m− 2) and APCI (70.44) were obtained for the Ablagh genotype. The highest nitrate content was obtained with a photoperiod of 18 h for the Kapoor cultivar. The highest net photosynthesis rate was related to the Violeto cultivar under a 24-hour photoperiod (7.89 μmol CO2 m− 2 s− 1). Antioxidant capacity and flavonoids had a positive correlation with phenolic compounds and vitamin C. Yield had a positive correlation with antioxidant capacity, flavonoids, vitamin C, APCI, and proline.ConclusionsUnder continuous light conditions, basil microgreens resistance to light stress by increasing the synthesis of secondary metabolites and the increase of these biochemical compounds made basil microgreens increase their performance along with the increase of these health-promoting compounds. The best balance between antioxidant compounds and performance was achieved in continuous red + blue light. Based on these results, the use of continuous artificial LED lighting, due to the increase in plant biochemical with antioxidant properties and yield, can be a suitable strategy for growing basil microgreens in floating systems.

Treatment of low-C/N nitrate wastewater using a partial denitrification-anammox granule system: Granule reconstruction, stability, and microbial structure analyses

Industrial wastewater discharged into sewer systems is often characterized by high nitrate contents and low C/N ratios, resulting in high treatment costs when using conventional activated sludge methods. This study introduces a partial denitrification-anammox (PD/A) granular process to address this challenge. The PD/A granular process achieved an effluent TN level of 3.7 mg/L at a low C/N ratio of 2.3. Analysis of a typical cycle showed that the partial denitrification peaked within 15 min and achieved a nitrate-to-nitrite transformation ratio of 86.9%. Anammox, which was activated from 15 to 120 min, contributed 86.2% of the TN removal. The system exhibited rapid recovery from post-organic shock, which was attributed to significant increases in protein content within TB-EPS. Microbial dispersion and reassembly were observed after coexistence of the granules, with Thauera (39.12%) and Candidatus Brocadia (1.25%) identified as key functional microorganisms. This study underscores the efficacy of PD/A granular sludge technology for treating low-C/N nitrate wastewater.

The impact of environmental factors and contaminants on thyroid function and disease from fetal to adult life: current evidence and future directions.

The thyroid gland regulates most of the physiological processes. Environmental factors, including climate change, pollution, nutritional changes, and exposure to chemicals, have been recognized to impact thyroid function and health. Thyroid disorders and cancer have increased in the last decade, the latter increasing by 1.1% annually, suggesting that environmental contaminants must play a role. This narrative review explores current knowledge on the relationships among environmental factors and thyroid gland anatomy and function, reporting recent data, mechanisms, and gaps through which environmental factors act. Global warming changes thyroid function, and living in both iodine-poor areas and volcanic regions can represent a threat to thyroid function and can favor cancers because of low iodine intake and exposure to heavy metals and radon. Areas with high nitrate and nitrite concentrations in water and soil also negatively affect thyroid function. Air pollution, particularly particulate matter in outdoor air, can worsen thyroid function and can be carcinogenic. Environmental exposure to endocrine-disrupting chemicals can alter thyroid function in many ways, as some chemicals can mimic and/or disrupt thyroid hormone synthesis, release, and action on target tissues, such as bisphenols, phthalates, perchlorate, and per- and poly-fluoroalkyl substances. When discussing diet and nutrition, there is recent evidence of microbiome-associated changes, and an elevated consumption of animal fat would be associated with an increased production of thyroid autoantibodies. There is some evidence of negative effects of microplastics. Finally, infectious diseases can significantly affect thyroid function; recently, lessons have been learned from the SARS-CoV-2 pandemic. Understanding how environmental factors and contaminants influence thyroid function is crucial for developing preventive strategies and policies to guarantee appropriate development and healthy metabolism in the new generations and for preventing thyroid disease and cancer in adults and the elderly. However, there are many gaps in understanding that warrant further research.

Hemispherical scale mechanisms of nitrate formation in global marine aerosols

Nitrogen oxides (NOx) in the atmosphere directly affect air quality; however, their oxidation products (e.g., nitrate) are essential nutrients in terrestrial and marine ecosystems. To date, the mechanism and rate of nitrate formation in the global-scale marine boundary layer remains uncertain. Herein, aerosol nitrate isotopes covering the global ocean were analysed and observations indicated that nitrate formation was dominated by the proportion between the hydroxyl radical (daytime) and ozone (nighttime) pathways in the Northern Hemisphere (NH), whereas it changed to the BrO (Antarctic iceberg emission) pathway in the Southern Hemisphere (SH). These differences in the pathways suggested that the NOx removal (nitrate formation) efficiency was higher in the NH, which could be responsible for the much higher nitrate concentrations in the NH than in the SH (over twice). This study can assist in formulating effective policies to mitigate global NOx pollution and improve our understanding of the impact of increasing NOx concentrations on global ocean productivity.

Iron-based mixotrophic denitrification for enhancing nitrate removal from municipal secondary effluent: Performance, microbial community dynamics, and economic feasibility

High nitrate content limits the recycling of the secondary effluent of wastewater treatment plants. In the research, one biomass-iron mixture (BIM) filter material based on mixotrophic denitrification mode (heterotrophic and iron-driven autotrophic denitrification) was developed and used to construct a novel denitrification biological filter (BIM-DNBF) for the nitrogen removal of secondary effluent. BIM-DNBF had a short start-up time (approximately 9 days), and high total nitrogen removal (81 %-89 %) without external addition of organic carbon sources during the whole operation. The coexistence of dominant heterotrophic-denitrification-like Pseudomonas and Erysipelothrix as well as iron-driven autotrophic-denitrification-like Citrobacter, Acidovorax, etc. were found in the BIM-DNBF. Moreover, biomass was recognized as one key player in promoting the reduction of Fe3+ to Fe2+, thereby facilitating the occurrence of iron-driven autotrophic denitrification. In addition, BIM-DNBF was assessed to be affordable. These findings provide evidence that BIM-DNBF can be an efficient technology for nitrogen removal of secondary effluent.

Exploring the interplay between water quality parameters and aquatic fauna in a human-dominated stream network in Iran

Rivers and streams are dynamic linear features that undergo numerous disturbances from nearby human activities. This is particularly evident in Iranian arid regions, where agricultural activities are concentrated along these water bodies to harness their freshwater resources. This study utilized 12 stations in the Maharlu stream network to assess the impact of human activities on its water quality and aquatic fauna. Results indicated that severe nutrient pollution attributed to a high mean nitrate concentration (67.77 ± 79.72 mg/L). By employing PCA analysis, three main principal components were extracted, explaining a variance of 82.61%. PC1 exhibited high positive loadings for dissolved oxygen (DO), while PC2 showed an elevated salt concentration. Midges and non-biting mosquitoes, predominantly from the Chironomidae family, emerged as the dominant taxon, contributing to over 98% of the total species abundance. Furthermore, integrated PCA–CCA analysis revealed downstream shifts in species composition toward more tolerant species, driven by decreasing DO levels and increasing salt concentrations. These shifts in trends found in water quality parameters and species composition were linked to agricultural runoff carrying substantial amounts of fertilizers, pesticides, and organic matter from livestock farming. Consequently, there is an urgent need to implement conservation measures to mitigate their adverse effects.

Enhanced Biological Nitrate Removal from Groundwater in Humid Tropical Regions Using Corn Cob-Based Permeable Reactive Barriers: A Case Study from Panama

Nitrate contamination in groundwater is a global concern due to its widespread presence and consequential social, environmental, and economic ramifications. This study investigates the efficacy of biological denitrification in a humid tropical setting, utilizing corn cob in batch and column tests to assess nitrate removal under varying conditions. Batch tests demonstrated the nitrate removal efficiencies of 93.14%, 91.58%, 90.77%, and 98.74% for initial concentrations of 22.18 ± 2.82 mg/L, 27.3 mg/L, 69.1 ± 1.2 mg/L and 115.08 ± 1.88 mg/L, respectively. In the column test, the removal efficiency was 99.86%, 87.13%, and 74%, and the denitrification rate was 32.82, 53.43, and 83.53 mg NO3−-N/L d, for a hydraulic retention time (HRT) of 24 h, 16 h, and 7 h, respectively. Predominantly, nitrate removal occurred via biological denitrification, particularly favoring a 24 h HRT. The corn cob effectively removed high nitrate concentrations of up to 115 mg NO3−-N/L. Scanning electron microscopy and Fourier transform infrared spectroscopy revealed surface characteristic changes of the carbon source pre- and post-denitrification. This research sheds light on the potential of biological denitrification using corn cob in humid tropical environments, offering a promising avenue for addressing nitrate contamination challenges in groundwater systems.

Characteristics of late summer Arctic brash sea ice and its melting effect on the surface-water biogeochemistry of the Chukchi Shelf and Canada Basin

To understand the impact of the melting of late summer Arctic brash ice on the surface waters of the Chukchi Sea, we collected sea-ice samples during 2021. Floating sea ice was collected by a wire mesh pallet cage from the side of the R/V Mirai. We measured physical and biogeochemical parameters such as salinity, oxygen stable isotopic ratios, turbidity, and concentrations of chlorophyll-a and nutrients. The samples of brash ice were multiyear ice based on satellite back-trajectory analysis. Comparison of nutrient concentrations in brash ice with those of seawater samples from the temperature minimum layer similar to the water in the sea ice originated suggested that the characteristics of the brash ice were greatly affected by biogeochemical processes such as remineralization. The extremely high turbidity and concentrations of chlorophyll-a observed in the brown/green ice samples reflected the impact of sediment as well as the influence of biological activities. The N:P ratios were less than 1 because of the high phosphate concentrations, even though the ammonium concentrations were high. We hypothesized that this low N:P ratio reflected the combined effects of the accumulation of nutrients due to remineralization in the biofilm and differences of remineralization rate and adsorption features of nitrogen and phosphorus. Based on the high nitrate and ammonium concentrations in the sea-ice samples, we postulated a marked impact of sea-ice meltwater on the nitrogen cycle in the nitrate-depleted surface waters of the Chukchi Sea during late summer. We estimated that meltwater nitrogen could support 0.3%–2.6% of primary production in the northern Chukchi Sea. Our results suggest that high-turbidity ice will play an important role as a source of nutrients to the ocean during melting of sea ice, and understanding its distribution, amount, and geochemical characteristics is vital.

Assessing the Effects of Environmental Flows on Water Quality for Urban Supply

This paper analyses the effects of environmental flows on water quality within a highly regulated basin, focusing on the Turia River basin in the eastern Iberian Peninsula. Through water management and water quality models, a series of simulations were conducted, introducing variations in the outflows of the Loriguilla reservoir to evaluate the effects of different environmental flow scenarios on water quality, particularly at the location of the intake for the water supply to Valencia. Three environmental flow scenarios were analyzed, alongside an alternative management scenario, considering their implications on water quality and reliability of water demand. The findings of this paper, particularly the nitrate (NO3−) concentration evolution, highlight the influence of minimum e-flow and e-flow regimes on water quality within the basin. These results suggest that while modifying the current flow regime can lead to some improvements in nitrate concentrations at the Valencia supply intake point, the primary cause of high nitrate concentrations is attributed to irrigation return flow and the pre-existing contamination of the aquifer. This analysis offers valuable insights into the complexities of water quality management in regulated basins, emphasizing the need for a multi-faceted approach to address the diverse factors influencing water quality and demand supply reliability.

Influence of Inorganic Nitroge N-Nutrients on Copper Toxicity in <I>Anacystis nidulans</I> and Cyanophage As-I Resistant Mutant

The effect of different nitrogen sources on growth and copper toxicity was studied in the unicellular cyanobacterium Anacystis nidulans and Gyanophage AS-1 resistant mutant (An/AS-1). The mutant An/AS-1 was characterised by slow growth rate but was more senstitive to copper than its parent. In both the strains, the presence of high nitrate concentrations, which supported better growth of algae, reduced the algicidal effect of copper. However, other inorganic nitrogen sources such as nitrite and ammonium caused more inhibition and reduced the specific growth rate.

Deep soil desiccation hinders nitrate leaching to groundwater in the global largest apple cultivation area

Massive use of N fertilizer in apple orchards aids China’s Loess Plateau (CLP) to become the largest region of apple production in the world, but it also leads to substantial nitrate accumulation in the vadose zone, posing a potential environmental risk. However, a holistic understanding of the spatial patterns and controls of soil nitrate in the vadose zone of apple orchards remains understudied, which is unfavorable for the formulation of a science-based N application strategy. To this end, we collected a total of 2852 paired data across apple orchards on the CLP from 52 published literature and 1000 paired data from our field sampling. We found that residual nitrate accumulation primarily occurred in the top 4–8.8 m soil layer, and it varied according to mean annual precipitation (MAP) and stand age; the accumulation peaked in sites with MAP of 500–600 mm and declined with a decrease in MAP; and among various stand ages, the highest nitrate content was observed in the 25-yr-old orchard. It was found that MAP and N fertilizer application amounts dominated nitrate accumulation in the soil. Furthermore, the desiccation index of the soil layer below the maximum cumulative depth was identified as the main factor influencing soil nitrate maximum accumulation depth . This means that deep soil desiccation hinders nitrate leaching towards deeper layers and reduces the risk of groundwater contamination. The findings here may provide insights into sustainable nitrogen and water management in apple orchards on the CLP and potentially in other similar regions.

Human health risk associated with nitrates in some vegetables: A case study in Gonabad

Vegetables are vital parts of the human diet, however, they also may contain substances such as nitrate which can affect human health. This cross-sectional research was conducted with the objective to assess the health risk of citizens in Gonabad from nitrate exposure through the consumption of some vegetables. Common vegetables namely, cucumber, carrot, tomato, potato, lettuce, cauliflower, onion and mushroom were analyzed for nitrate contents. The values of the estimated daily intakes (EDIs), target hazard quotients (HQs) were computed to estimate the non-carcinogenic health risk. Nitrate concentrations in the selected vegetables ranged from 25 to 2100 mg/kg (fresh weight). The highest concentration of nitrate was found in lettuce (2100 mg/kg). The EDI values in some vegetables exceeded the acceptable daily intake of nitrate. The calculated HQ values of carrot, potato, lettuce, onion and mushroom were HQ ≥ 1 for children, signifying non-carcinogenic health risk to the age group. For teenagers group, the HQ values for lettuce and onion was ≥ 1. Furthermore, potato, lettuce and onion were unsafe considering HQ values related to nitrate concentration in adults. Therefore, the control of possible contamination sources and minimization of vegetable nitrate concentration are recommended.