High Levels Of Nitrate Research Articles

Multiple isotopes reveal the driving mechanism of high NO3– level and key processes of nitrogen cycling in the lower reaches of Yellow River

The continuous increase of nitrate (NO3–) level in rivers is a hot issue in the world. However, the driving mechanism of high NO3– level in large rivers is still lacking, which has limited the use of river water and increased the cost of water treatment. In this study, multiple isotopes and source resolution models are applied to identify the driving mechanism of high NO3– level and key processes of nitrogen cycling in the lower reaches of the Yellow River (LRYR). The major sources of NO3– were sewage and manure (SAM) in the low-flow season and soil nitrogen (SN) and chemical fertilizer (CF) in the high-flow season. Nitrification was the most key process of nitrogen cycling in the LRYR. However, in the biological removal processes, denitrification may not occur significantly. The temporal variation of contributions of NO3– sources were estimated by a source resolution model in the LRYR. The proportional contributions of SAM and CF to NO3– in the low-flow and high-flow season were 32.5%-52.3%, 44.2%-46.2% and 36.0%-40.8%, 54.9%-56.9%, respectively. The driving mechanisms of high NO3– level were unreasonable sewage discharge, intensity rainfall runoff, nitrification and lack of nitrate removal capacity. To control the NO3– concentration, targeted measures should be implemented to improve the capacity of sewage and wastewater treatment, increase the utilization efficiency of nitrogen fertilizer and construct ecological engineering. This study deepens the understanding of the driving mechanism of high nitrate level and provides a vital reference for nitrogen pollution control in rivers to other area of the world.

Three main nitrate reservoirs in the mammalian body

Nitric oxide (NO) is a free radical with multiple functions in virtually all cells. In mammals, NO is generated by nitric oxide synthase from arginine and by reduction of nitrate/nitrite by tissue xanthine oxidoreductase (XOR) or microbiome. Previously, we reported in several mammalian species, including human, that skeletal muscle is a major nitrate reservoir in the body and that nitrate from this reservoir is systemically available and used to generate nitrite and NO. In our recent large animal study, we found that there are similar levels of nitrate stored in bone and skin. In our prior study, skeletal muscle showed a high level of nitrate at 57±39 nmol/g, relative to other tissues, such as liver and plasma at 15±5 nmol/g and 34±19 nmol/g, respectively. Here, we found that the average level of nitrate in the bone is 45±17 nmol/g and in the skin 41±19 nmol/g.Considering that the skeletal muscle, skin and skeleton are three largest organs in mammals, forming about 35-50%, 21% and 14% of body weight, respectively, these results highlight the importance of skeletal muscle as a main nitrate reservoir and the role of skin and bone as new auxiliary nitrate reservoirs. Along with skeletal muscle, the bones and skin likely play an important role in maintaining homeostasis of the nitrate-nitrite-nitric oxide pathway.Also, important from therapeutic point of view, all three organs are well responding to dietary nitrate interventions by increasing their respective nitrate levels, which leads to general increase of systemic and local NO availability and perhaps could be used as one of the ways to increase NO availability in some diseases. 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 2023 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.

Environmental Parameters And Phytoplankton Community Quality: Implications For Food Safety In Coastal Communities

This study aimed to evaluate environmental parameters and phytoplankton quality as well as the implications for the food safety of seafood-consuming coastal communities. The study was conducted in coastal waters of South Sulawesi, Indonesia at four sites (three stations/site): Pangkep (PK), Kuri (KR), Maros (MR), and Tallo (TL) during June, August, and October 2020. Observations formed three spatial clusters: MR1, PK; MR2, MR3, TL; KR (92.5 % similarity), and two temporal clusters: June 2020; August and October 2020 (87.9 % similarity). PCA showed parameters most strongly characterizing TL, KR, and MR (except MR1) were high levels of salinity, nitrate, nitrite, ammonium, silicate, temperature, pH, and abundance of both phytoplankton that can form harmful algal blooms (HABs) and non-HAB forming phytoplankton (non-HABs), with low current velocity. PK was characterized by high current velocity, non-HABs, orthophosphate, ammonium, nitrite, and turbidity with low nitrate and HABs. Main characterizing parameters in the temporal PCA were high current velocity and HABs with low orthophosphate in June 2020; high nitrate, ammonium, orthophosphate, and non-HABs with even lower HABs in August 2020; high turbidity, temperature, and salinity with low pH, nitrite, silicate, and HABs in October 2020. Current velocity (low at TL, KR, MR and high at PK) influenced both non-HABs and HABs. The results indicate that faster currents may have impeded HABs development so that the phytoplankton quality was still good. Therefore, the fish from these waters can be considered safe for human consumption, thereby contributing to maintaining the health of coastal communities.

Changes in growth, physiology, and photosynthetic capacity of spinach (Spinacia oleracea L.) under different nitrate levels.

Nitrate content is an essential indicator of the quality of vegetables but can cause stress at high levels. This study aimed to elucidate the regulatory mechanisms of nitrate stress tolerance in spinach (Spinacia oleracea L.). We studied the effects of exogenous application of 15 (control), 50, 100, 150, 200, and 250 mM NO3- on spinach growth, physiology, and photosynthesis. The results showed that all the nitrate treatments inhibited the growth of the aerial parts of spinach compared to the control. In contrast, low nitrate levels (50 and 100 mM) promoted spinach root formation, but this effect was inhibited at high levels (150, 200, and 250 mM). Treatment with 150 mM NO3- significantly decreased the root growth vigor. Low nitrate levels increased the chlorophyll content in spinach leaves, whereas high levels had the opposite effect. High nitrate levels also weakened the net photosynthetic rate (Pn), the actual photochemical efficiency of PSII Y(II), and increased non-photochemical quenching (NPQ), reducing photosynthetic performance. Nitrate stress increased the activity of nitrate reductase (NR) and promoted the accumulation of nitrate in spinach leaves, exceeding the health-tolerance limit for nitrate in vegetables, highlighting the necessity of mitigating nitrate stress to ensure food safety. Starting with the 150 mM NO3- treatment, the proline and malondialdehyde content in spinach leaves and roots increased significantly as the nitrate levels increased. Treatment with 150 mM NO3- significantly increased soluble protein and flavonoid contents, while the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were significantly reduced in leaves. However, spinach could resist nitrate stress by regulating the synthesis of osmoregulatory substances such as proline, thus showing some nitrate tolerance. These results provide insights into the physiological regulatory mechanisms of nitrate stress tolerance and its mitigation in spinach, an essential vegetable crop.

Selected hematological parameters and oxidative stress in red blood cells (RBCs) after accidental cases of nitrate toxicity in the goat fed cabbage

ABSTRACT Nitrate poisoning due to the consumption of cabbages was diagnosed in a small goat flock, in Qena city, Egypt. The methylene blue 1% antidote (1 mg/kg BW) was given intravenously to the poisoned goats. Nitrate poisoning was confirmed in blood plasma, saliva, urine, and cabbage dry matter samples. The dark brown blood and methemoglobin fraction were 47.25 ± 0.58%. Green cabbage containing 7.1% nitrate on dried materials was fed to the goats. The nitrate concentration in the saliva was (59.50 ± 4.67), compared to the healthy goats reared in the same area and tested positive in the plasma and urine of intoxicated goats. Intoxication induced a significant decline in the Red Blood Cells count, hemoglobin concentration, and HCT % (P < 0.001), while the WBC count (P < 0.001), neutrophils (P < 0.001), and monocyte percentage were elevated (P < 0.002) in intoxicated goats, while the lymphocyte % (P < 0.01) significantly decreased when compared to the control. For the oxidative stress in the red blood cells, nitrate toxicity caused a significant elevation in the concentration of Malondialdehyde, (P < 0.001) while Superoxide Dismutase, Glutathione, and Glutathione S-Transferase levels were significantly reduced (P < 0.001) compared to the control. In this current report, the ingestion of goat to cabbage containing a high level of nitrate exhibited nitrate-nitrite intoxication.

Crosstalk Between miRNA and Protein Expression Profiles in Nitrate-Exposed Brain Cells.

Growing evidence reported a strong association between the nitrate ingestion and adverse health consequences in humans, including its detrimental impact on the developing brain. The present study identified miRNAs and proteins in SH-SY5Y human neuroblastoma cells and HMC3 human microglial cells using high-throughput techniques in response to nitrate level most prevalent in the environment (India) as X dose and an exceptionally high nitrate level as 5X dose that can be reached in the near future. Cells were exposed to mixtures of nitrates for 72 h at doses of X and 5X, 320 mg/L and 1600 mg/L, respectively. OpenArray and LCMS analysis revealed maximum deregulation in miRNAs and proteins in cells exposed to 5X dose. Top deregulated miRNAs include miR-34b, miR-34c, miR-155, miR-143, and miR-145. The proteomic profiles of both cell types include proteins that are potential targets of deregulated miRNAs. These miRNAs and their targeted proteins involve in multiple functions, including metabolic processes, mitochondrial functions, autophagy, necroptosis, apoptosis, neuronal disorders, brain development, and homeostasis. Furthermore, measuring mitochondrial bioenergetics in cells exposed to nitrate revealed that a 5X dose causes a significant reduction in oxygen consumption rate (OCR) and other bioenergetic parameters in both cell types. In summary, our studies have demonstrated that a 5X dose of nitrate significantly alters cellular physiology and functions by deregulating several miRNAs and proteins. However, X dose of nitrate has not caused any adverse effects on any cell type.

High-Nitrate-Supply-Induced Transcriptional Upregulation of Ascorbic Acid Biosynthetic and Recycling Pathways in Cucumber

Nowadays open field and protected vegetable cultivation practices require and use genotypes which are precisely tailored to their intended growth environments. Variability of this kind provides a rich source of material to uncover molecular mechanisms supporting the necessarily divergent physiological traits. In this study, typical field-optimized and glasshouse-cultivated cucumber F1 hybrids were investigated, and displayed slower growth ('Joker') and faster growth ('Oitol') in seedlings. Antioxidant capacity was lower in 'Joker' and higher in 'Oitol', pointing to a potential redox regulation of growth. The growth response of seedlings to paraquat treatment indicated stronger oxidative stress tolerance in the fast-growing 'Oitol'. To test whether protection against nitrate-induced oxidative stress was also different, fertigation with increasing potassium nitrate content was applied. This treatment did not change growth but decreased the antioxidant capacities of both hybrids. Bioluminescence emission revealed stronger lipid peroxidation triggered by high nitrate fertigation in the leaves of 'Joker' seedlings. To explore the background of the more effective antioxidant protection of 'Oitol', levels of ascorbic acid (AsA), as well as transcriptional regulation of relevant genes of the Smirnoff-Wheeler biosynthetic pathway and ascorbate recycling, were investigated. Genes related to AsA biosynthesis were strongly upregulated at an elevated nitrate supply in 'Oitol' leaves only, but this was only reflected in a small increase in total AsA content. High nitrate provision also triggered expression of ascorbate-glutathion cycle genes with stronger or exclusive induction in 'Oitol'. AsA/dehydro-ascorbate ratios were higher in 'Oitol' for all treatments, with a more pronounced difference at high nitrate levels. Despite strong transcriptional upregulation of ascorbate peroxidase genes (APX) in 'Oitol', APX activity only increased significantly in 'Joker'. This suggests potential inhibition of APX enzyme activity specifically in 'Oitol' at a high nitrate supply. Our results uncover an unexpected variability in redox stress management in cucumbers, including nitrate inducibility of AsA biosynthetic and recycling pathways in certain genotypes. Possible connections between AsA biosynthesis, recycling and nitro-oxidative stress protection are discussed. Cucumber hybrids emerge as an excellent model system for studying the regulation of AsA metabolism and the roles of AsA in growth and stress tolerance.

Assessment of groundwater quality and human health risks of nitrate and fluoride contamination in a rapidly urbanizing region of India

Groundwater contamination studies are important to understand the risks to public health. In this study, groundwater quality, major ion chemistry, sources of contaminants, and related health risks were evaluated for North-West Delhi, India, a region with a rapidly growing urban population. Groundwater samples collected from the study area were analysed for physicochemical parameters - pH, electrical conductivity, total dissolved solids, total hardness, total alkalinity, carbonate, bicarbonate, chloride, nitrate, sulphate, fluoride, phosphate, calcium, magnesium, sodium and potassium. Investigation of hydrochemical facies revealed that bicarbonate was the dominant anion while magnesium was the dominant cation. Multivariate analysis using principal component analysis and Pearson correlation matrix indicated that major ion chemistry in the aquifer under study is primarily due to mineral dissolution, rock-water interactions and anthropogenic factors. Water quality index values showed that only 20% of the samples were acceptable for drinking. Due to high salinity, 54% of the samples were unfit for irrigation purposes. Nitrate and fluoride concentrations ranged from 0.24 to 380.19 mg/land 0.05 to 7.90mg/l, respectively due to fertilizer use, wastewater infiltration and geogenic processes. The health risks from high levels of nitrate and fluoride were calculated for males, females, and children. It was found that health risk from nitrate is more than fluoride in the study region. However, the spatial extent of risk from fluoride is more indicating that more people suffer from fluoride pollution in the study area. The total hazard index for children was found to be more than adults. Continuous monitoring of groundwater and application of remedial measures are recommended to improve the water quality and public health in the region.

Prediction of ground water quality in western regions of Tamil Nadu using deep auto encoders

The main objective of this research is the prediction of ground water quality in western regions of Tamil Nadu. Groundwater pollution by nitrates is a worldwide issue that must be addressed with technological and regulatory solutions. Many regions of the world have discovered that their groundwater contains dangerously high levels of nitrates. The development of ecologically friendly nitrate treatment and removal methodologies, as well as an increased knowledge of the processes of nitrate formation and pollution in groundwater, have been the focus of current research efforts. However, the impacts of nitrate and chloride contaminant are not well analyzed in the previous works with proper evaluations. In this paper, the research analyses the presence of nitrate and chloride contaminant in ground water. The presence of nitrate and chloride contaminant is collected from western regions of Tamil Nadu and the quality is determined initially using Water quality indicator (WQI). The deep auto encoder is proposed in this research to estimate if the quality obtained is influenced by the presence of various contaminant in that region. The performance of the proposed approach is evaluated and compared with the existing state of art models using various parameters like accuracy, recall, precision, and F1-score.

Groundwater fluoride and nitrate contamination and associated human health risk assessment in South Punjab, Pakistan.

Consumption of high fluoride (F-) and nitrate (NO3-) containing water may pose serious health hazards. One hundred sixty-one groundwater samples were collected from drinking wells in Khushab district, Punjab Province, Pakistan, to determine the causes of elevated F- and NO3- concentrations, and to estimate the human health risks posed by groundwater contamination. The results showed pH of the groundwater samples ranged from slightly neutral to alkaline, and Na+ and HCO3- ions dominated the groundwater. Piper diagram and bivariate plots indicated that the key factors regulating groundwater hydrochemistry were weathering of silicates, dissolution of evaporates, evaporation, cation exchange, and anthropogenic activities. The F- content of groundwater ranged from 0.06 to 7.9mg/L, and 25.46% of groundwater samples contained high-level fluoride concentration (F- > 1.5mg/L), which exceeds the (WHO Guidelines for drinking-water quality: incorporating the first and second addenda, WHO, Geneva, 2022) guidelines of drinking-water quality. Inverse geochemical modeling indicates that weathering and dissolution of fluoride-rich minerals were the primary causes of F- in groundwater. High F- can be attributed to low concentration of calcium-containing minerals along the flow path. The concentrations of NO3- in groundwater varied from 0.1 to 70mg/L; some samples are slightly exceeding the (WHO Guidelines for drinking-water quality: incorporating the first and second addenda, WHO, Geneva, 2022) guidelines for drinking-water quality. Elevated NO3- content was attributed to the anthropogenic activities revealed by PCA analysis. The high levels of nitrates found in the study region are a result of various human-caused factors, including leaks from septic systems, the use of nitrogen-rich fertilizers, and waste from households, farming operations, and livestock. The hazard quotient (HQ) and total hazard index (THI) of F- and NO3- showed high non-carcinogenic risk (> 1) via groundwater consumption, demonstrating a high potential risk to the local population. This study is significant because it is the most comprehensive examination of water quality, groundwater hydrogeochemistry, and health risk assessment in the Khushab district to date, and it will serve as a baseline for future studies. Some sustainable measures are urgent to reduce the F- and NO3- content in the groundwater.

Characterization of Enrichment Cultures of Anammox, Nitrifying and Denitrifying Bacteria Obtained from a Cold, Heavily Nitrogen-Polluted Aquifer

Anammox bacteria related to Candidatus Scalindua were recently discovered in a cold (7.5 °C) aquifer near sludge repositories containing solid wastes of uranium and processed polymetallic concentrate. Groundwater has a very high level of nitrate and ammonia pollution (up to 10 and 0.5 g/L, respectively) and a very low content of organic carbon (2.5 mg/L). To assess the potential for bioremediation of polluted groundwater in situ, enrichment cultures of anammox, nitrifying, and denitrifying bacteria were obtained and analyzed. Fed-batch enrichment of anammox bacteria was not successful. Stable removal of ammonium and nitrite (up to 100%) was achieved in a continuous-flow reactor packed with a nonwoven fabric at 15 °C, and enrichment in anammox bacteria was confirmed by FISH and qPCR assays. The relatively low total N removal efficiency (up to 55%) was due to nonstoichiometric nitrate buildup. This phenomenon can be explained by a shift in the metabolism of anammox bacteria towards the production of more nitrates and less N2 at low temperatures compared to the canonical stoichiometry. In addition, the too high an estimate of specific anammox activity suggests that N cycle microbial groups other than anammox bacteria may have contributed significantly to N removal. Stable nitrite production was observed in the denitrifying enrichment culture, while no "conventional" nitrifiers were found in the corresponding enrichment cultures. Xanthomonadaceae was a common taxon for all microbial communities, indicating its exclusive role in this ecosystem. This study opens up new knowledge about the metabolic capabilities of N cycle bacteria and potential approaches for sustainable bioremediation of heavily N-polluted cold ecosystems.

Hydrogeochemical Characteristics and Groundwater Quality Assessment of a Relatively- Pristine Agricultural Basin (Palas Basin)

This study investigates the spatial and temporal changes in groundwater levels and quality in the Palas Basin, a relatively-pristine semi-arid agricultural basin in T . Although groundwater is solely used as irrigation and drinking potable water resource throughout the basin, measurements regarding the dynamics and quality of groundwater were quite rare. The analyses were based on data collected from 12 water quality monitoring wells and 15 groundwater level monitoring wells during June 2019-May 2020. Water samples were analyzed for pH, electrical conductivity, temperature, nitrate, nitrite, ammonium, total nitrogen, total hardness, alkalinity, chloride,sulfate, phosphate, total organic carbon, calcium, magnesium, sodium, potassium, and arsenic. Data analyses included hydrogeochemical analysis and multivariate statistical analysis such as principal component analysis and cluster analyses. Results showed that water quality in the basin is mostly controlled by natural factors, however, anthropogenic impacts from agriculture activities were apparent in some regions. The basin shows significant changes in water levels throughout the year due to irrigation activities. The groundwater quality was classified as either Ca-Mg-HCO3and Ca-Mg-SO4 type. In the majority of the basin, water quality was suitable for irrigation and drinking water uses, however, a few sampling sites had very high electrical conductivity, sulfate, nitrate, and arsenic levels. The high levels of nitrates were detected in areas, where agriculture is intense, indicating that agricultural activities might be affecting water quality. High sulfate, electrical conductivity, and arsenic levels could be related to the hydrogeological setting of the basin. This study showed that agricultural activities and natural factors were effective on the hydrogeochemical characteristics of the Palas Basin.

Attenuation of mercury phytotoxicity with a high nutritional level of nitrate in alfalfa plants grown hydroponically

Mercury (Hg) is one of the most dangerous pollutant heavy metals to the environment, which causes several toxic effects in plants upon accumulation, such as induction of oxidative stress. Nitrate (NO3) is the prevalent form to incorporate nitrogen (N) in higher plants, through its reduction to nitrite (NO2) by the enzyme nitrate reductase (NR). We studied the physiological alterations caused by Hg (0, 6 and 30 µM) in alfalfa plants grown at two different levels of NO3: low, (2 mM; LN), and high (12 mM; HN) for one week using a semi-hydroponic culture system. Several parameters of oxidative stress such as lipid peroxidation, chlorophyll content, biothiol concentration, and ascorbate peroxidase (APX) and glutathione reductase (GR) activities showed that HN plants were less affected by Hg. Nitrate reductase activity and NO3 concentration were also altered under Hg stress, with lower impact in plants nourished with high NO3. Our results highlight the importance of the NO3 nutritional status to improve tolerance to toxic metals like Hg.

Assessment of Water Quality of Mahanadi and It's Tributary Katha Jodi River, Cuttack District, Odisha

For all living things, water is one of the most important sources. Despite being a renewable resource, clean water scarcity is a major problem in many regions of the world. We require water for a variety of things, including food production, personal hygiene, electrical generation, fire control, and most importantly, survival. Nine sampling stations were chosen at various locations along the Mahanadi and its tributary, the Katha Jodi River, in the Cuttack area (S1-S9). To collect a tiny amount of water from the water source for water analysis and to look at the physico-chemical components that are present in the water, sampling is done. Our study sites' dissolved oxygen concentrations range from 3.9 to 5.8 mg/lit, and the water samples from all of the sites are only mildly alkaline. All study sites have alkalinities below 150 mg/lit, ranging from 129 mg/lit to 162 mg/lit. All of the study sites' water conductivities are within the typical range of river water, or 200 to 1000 mhos/cm. All of the study locations, with the exception of our study sites 1 and 2, have high nitrate levels of greater than 100 mg/lit. Our study sites had phosphate concentrations between 0.8 and 2.0 mg/lit, and a river shouldn't have more phosphates than 0.1 mg/L. Over these limits, phosphorus can be quite hazardous.

Electrochemical process for removing nitrate from drinking water by Taguchi model

The use of nitrogenous fertilizers, detergents, the food industry, the power industry, and nuclear fuels are all man-made causes of nitrate pollution. High nitrate levels in drinking water (>50 mg/L) cause blue baby syndrome (methemoglobinemia), particularly in children, as well as the development of carcinogenic nitrosamines. The goal of this applied-analytical research is to see how well a batch electrochemical (E) reactor with monopolar electrode mode can remove nitrate from urban drinking water. The effects of several operational factors on nitrate removal were investigated, including current density, electrode material, pH, and time. The efficacy of nitrate removal is investigated under various working conditions including current density (1–8 mA/cm2), electrode material (aluminum, copper, iron, steel, and zinc), pH (6–8), and time (5–40 min). The amount of nitrate in the body is measured using a process outlined in standard standards (4500-NO3-B). At comparable experimental circumstances, As–As anode–cathode electrodes generate the lowest nitrate removal (0.1%), whereas Zn–Cu anode–cathode electrodes provide the maximum nitrate removal (100%). Batch tests revealed that employing zinc–copper as the anode–cathode electrode configuration resulted in the most nitrate elimination. The increase in current density from 1 to 8 mA/cm2 at the optimal electrode and pH resulted in a 62%–100% improvement in nitrate removal. The increase in duration from 5 to 40 min at the optimal electrode and pH resulted in a 33%–100% increase in nitrate removal. The researchers discovered that increasing current density, electrolysis duration, and pH improved nitrate removal efficiency. As a result of batch tests, the electrochemical reactor seems to be effective in removing nitrate from drinking water and might be regarded a viable method for treating nitrate-polluted water. It was suggested that a bio- electrochemical reactor be investigated.

PH affects the aqueous-phase nitrate-mediated photooxidation of phenolic compounds: implications for brown carbon formation and evolution.

Brown carbon (BrC) is known to have important impacts on atmospheric chemistry and climate. Phenolic compounds are a prominent class of BrC precursors that are emitted in large quantities from biomass burning and fossil fuel combustion. Inorganic nitrate is a ubiquitous component of atmospheric aqueous phases such as cloudwater, fog, and aqueous aerosols. The photolysis of inorganic nitrate can lead to BrC formation via the photonitration of phenolic compounds in the aqueous phase. However, the acidity of the atmospheric aqueous phase adds complexity to these photonitration processes and needs to be considered when investigating BrC formation from the nitrate-mediated photooxidation of phenolic compounds. In this study, we investigated the influence of pH on the formation and evolution of BrC from the aqueous-phase photooxidation of guaiacol, catechol, 5-nitroguaiacol, and 4-nitrocatechol initiated by inorganic nitrate photolysis. The reaction rates, BrC composition and quantities were found to depend on the aqueous phase pH. Guaiacol, catechol, and 5-nitroguaiacol reacted substantially faster at lower pH. In contrast, 4-nitrocatechol reacted at slower rates at lower pH. For all four phenolic compounds, the initial stages of photooxidation resulted in an increase in light absorption (i.e., photo-enhancement) in the near-UV and visible range due to the formation of light absorbing products formed via the addition of nitro and/or hydroxyl groups to the phenolic compound. Greater photo-enhancement was observed at lower pH during the nitrate-mediated photooxidation of guaiacol and catechol. In contrast, greater photo-enhancement was observed at higher pH during the nitrate-mediated photooxidation of 5-nitroguaiacol and 4-nitrocatechol. This indicated that the effect that the aqueous phase pH has on the composition and yields of BrC formed is not universal, and will depend on the initial phenolic compound. These results provide new insights into how the atmospheric aqueous phase acidity influences the reactivities of different phenolic compounds and BrC formation/evolution during photooxidation initiated by inorganic nitrate photolysis, which will have significant implications for how the atmospheric fates of phenolic compounds and BrC formation/evolution are modeled for areas with high levels of inorganic nitrate.

Seasonal Fluctuations in Nitrate Levels Can Trigger Lead Solder Corrosion Problems in Drinking Water.

After a utility switched its source water from ground to surface water in 2017, first draw water lead levels spiked due to increased lead solder corrosion that could not be explained by existing knowledge. When lead release was not adequately reduced with a 90:10 orthophosphate/polyphosphate corrosion inhibitor blend or even high levels of 100% orthophosphate, an in-depth investigation of possible causes revealed a strong correlation between 90th percentile lead and seasonal fluctuations in surface water nitrate levels. Complementary bench-scale studies that tested new copper coupons with lead solder and harvested pipes from a worst case home verified a strong relationship between nitrate and elevated lead. Lead release in the presence of nitrate became increasingly erratic with time, resulting in the spalling of large lead solder particulates up to 7 mm in length into the water. Lead levels were occasionally >1000 ppb in homes and >100000 ppb in the bench experiments with harvested pipe. Orthophosphate was unable to sufficiently reduce lead levels below the action level during periods with high nitrate levels in the bench studies. Water utilities and regulators should proactively consider possible unintended consequences of higher nitrate levels on lead release when changing source waters or during seasonal runoff events.

Agricultural nitrate export patterns shaped by crop rotation and tile drainage

Excessive agricultural nitrate export to aquatic systems degrades water quality and causes downstream ecological crises. Limited understanding of their underlying mechanisms and controls hinders mitigation measures. Here we analyzed observations of nitrate concentration (C) and discharge (Q) in 83 intensively managed agricultural watersheds across the central U.S. Midwest (37.0–44.5 N, 97.5–80.0 W), which reveals a regionally consistent pattern in C∼Q relationships: C∼Q relationship is chemodynamic at low flows and chemostatic at high flows, i.e., C increases with Q until a threshold beyond which C levels off. Motivated by this universal pattern, we developed a coupled model at the event scale that involves mixing of quick flow with high nitrate levels coming from shallow soils and the slow flow with low nitrate levels coming from deeper soils. Its implementation in combination with seasonal patterns of hydrology and agricultural practices explains observed patterns in the C∼Q relationship across broad spatial and temporal scales and quantifies their main driving factors. Agricultural practices (i.e., corn fraction, nitrogen fertilizer use) explain 49% of spatial variability of C in quick flow during peak season, whereas tile drainage explains another 25%. Scenario analysis of changing area fraction of tile and corn using model projections sheds light on plausible pathways to assess and implement nutrient loss reduction goals.

Metagenomics reveals the increased antibiotics resistome through prokaryote rather than virome after overuse of rare earth element compounds

Rare earth elements (REE) are extensively exploited in the agricultural ecosystems due to their various beneficial roles on plant growth. However, the ecotoxicological effects and environmental risk of REE are poorly assessed. Here, we investigated the effects of lanthanum and cerium nitrate on soil prokaryote and viral metal resistance genes (MRGs) and antibiotics resistance genes (ARGs) using a metagenomic-based approach. We found that relative abundances of prokaryote phyla Bacteroidetes and Chloroflexi decreased with increasing of both REE compounds. In addition, low level REE nitrate (0.05 and 0.1 mmol kg−1 soil) inhibited the viral family Phycodanaviridae, Rudiviridae, Schitoviridae, whereas high level (0.16 and 0.32 mmol kg−1 soil) REE nitrate suppressed the viral family Herelleviridae, Iridoviridae, Podoviridae. ARGs were not significantly affected by low level of REE nitrate. However, high level of both REEs nitrate increased the abundances of dominant prokaryote genes resisting to most of the drug classes, such as aminoglycoside, elfamycin, fluoroquinolone, macrolide, rifamycin. Abundance of MRGs in prokaryote did not change consistently with REE nitrate compound type and input rate. MRGs were only partially detected in the virome in some of the treatments, while ARGs was not detected in virome. Together, we demonstrated that overuse of REE nitrate in agriculture would increase the risk of dissemination of ARGs through prokaryotes but not virus, although viral community was substantially shifted.

Assessment of nitrogen interaction with temperature on the growth and toxin production of mat-forming toxin-producing Anagnostidinema carotinosum.

Global warming and eutrophication contribute to the severity of cyanobacteria blooms. However, it is unclear how these factors influence the growth and toxin production of Anagnostidinema carotinosum. Based on morphological and molecular analysis, this is the first time A. carotinosum was identified in South Korea. The interactive effect of temperature (25, 30 or 34°C) and nitrogen (2.5, 3.5 or 4.5mg NO3 -N l-1 ) on A. carotinosum growth and toxin production was studied. Increasing nitrogen limitation reflects reduced growth and chlorophyll-a content at all temperatures. However, the growth was effective under nitrogen limitation when temperatures exceeded 25°C. The maximum growth was found at 30°C, followed by 34°C under higher nitrate levels (3.5 and 4.5mg l-1 ). In addition, the cell microcystin and anatoxin-a quota increased significantly at 25°C with increasing nitrate limitation, decreasing considerably at 30°C in the same nitrate gradient. These results suggested temperatures stimulate A. carotinosum growth at 30 and 34°C and cellular toxin quota at 25 and 34°C with increasing NO3 -N levels. These findings imply that limiting nitrogen input alone can effectively reduce biomass; however, controlling A. carotinosum and its toxins at higher temperatures under nitrate limitation is necessary for water quality.