High Levels Of Nitrate Research Articles

Human Health Risk Assessment for Nitrate intake in Lucknow, India

Abstract: It is important to apply the methods to set the standard for drinking water quality and to conduct risk assessments since access to potable water resources exposes people to a variety of chemical pollutants, including nitrate. Drinking water with high nitrate levels can be harmful to health, especially for infants and pregnant women. The main objective of the present study was to determine the distribution levels of nitrate contamination in groundwater and its associated impact on human health risks in Lucknow India. For this 32 groundwater samples were collected randomly during April 2022. Nitrate concentration in groundwater samples ranged from 7 to 108 mg/L, with a mean value of 41.35 mg/L. The geographic information system (ArcGIS 10.7.1) was applied to mapping the nitrate concentration in groundwater resources of the studied area. About 43.75% of the groundwater samples are exceeding the permissible limits of nitrate (45 mg/l). Hence health risk assessment of nitrate has been carried out. Hazard quotient (HQ) values for male, female, children, and infants ranges from 0.14 to 2.07; 0.16 to 2.45; 0.17 to 2.63, and 0.16 to 2.53, respectively. The finding of data showed that HQ value was more than 1 in 53..125% of samples in groups of infants and children, 50% of samples for female, and 43.75% of samples in group of male.

EVALUATION OF THE WATER QUALITY OF ALGERIEN DAMS

This study aims to give an overview of the water quality of forty dams located in the west and eastof Algeria. It included a Physico-chemical characterization to highlight many factors that play arole in determining the quality of these waters such as: pH, Dissolved oxygen (O2), Nitrate (NO3),Nitrite (NO2), Phosphates (PO4), Organic matter (OM), Dry residue (DR), Biochemical OxygenDemand (BOD5) and Chemical Oxygen Demand (COD). The waters of the western dams have veryhigh dry residues, which could be linked to the terrain crossed and the high erodibility of the soilsin these regions. The highest level of nitrate (10 mg/l) was recorded in the BaniBahdel dam in thewest and similarly high values of BOD5 and COD, which show another indicator of water qualitydeterioration water at the dams in the western region. The application of statistical methods,Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) made it possibleto give a classification to these dams according to the degree of water contamination. The resultsplaced the western dams in the medium to very high pollution category. The eastern dams seemless affected by pollution.

FLUORIDE AND CHILDREN’S HEALTH IN INDIA: DISTRICT LEVEL ANALYSIS

Quality issues in water such as presence of high levels of arsenic, nitrates, iron, salinity and fluoride has been witnessed in various parts in India. Presence of fluoride at alarming levels has led to severe threat to human survival. Prolong consumption of contaminated water with an unsafe fluoride level can lead to many diseases. Therefore, using the exogenous variation in fluoride across districts, we try to assess the impact of fluoride contaminated water on health outcomes particularly for children; dental and skeletal diseases. Usingnationally representative dataset for India, greater exposure to fluoride contamination is associated with adverse health outcomes amongst school going children. Our findings suggest that an additional increase in fluoride contamination leads to higher risk of dental (odds ratio-1.196) and skeletal diseases (odds ratio-1.206). Moreover, the intensity and incidence of such diseases (dental-1.398 and skeletal diseases-1.494) has increased drastically over time. Our estimates are also robust to district and time fixed effects. Our findings also suggestchildren who belong to the age group of 7-14 years of age experience such adverse health outcomes relatively more than those who belongs to 0-6 years of age, owing to visibility of fluoride related symptoms at later stages in life. Uniformity of our results holds even after using an alternative measure of estimation, Propensity Score Matching.

Bacterial community of sediments under the Eastern Boundary Current System shows high microdiversity and a latitudinal spatial pattern

The sediments under the Oxygen Minimum Zone of the Eastern Boundary Current System (EBCS) along Central-South Peru and North-Central Chile, known as Humboldt Sulfuretum (HS), is an organic-matter-rich benthic habitat, where bacteria process a variety of sulfur compounds under low dissolved-oxygen concentrations, and high sulfide and nitrate levels. This study addressed the structure, diversity and spatial distribution patterns of the HS bacterial community along Northern and South-Central Chile using 16S rRNA gene amplicon sequencing. The results show that during the field study period, the community was dominated by sulfur-associated bacteria. Indeed, the most abundant phylum was Desulfobacterota, while Sva0081 sedimentary group, of the family Desulfosarcinaceae (the most abundant family), which includes sulfate-reducer and H2 scavenger bacteria, was the most abundant genus. Furthermore, a spatial pattern was unveiled along the study area to which the family Desulfobulbaceae contributed the most to the spatial variance, which encompasses 42 uncharacterized amplicon sequence variants (ASVs), three assigned to Ca. Electrothrix and two to Desulfobulbus. Moreover, a very high microdiversity was found, since only 3.7% of the ASVs were shared among localities, reflecting a highly diverse and mature community.

Overcoming barriers for nitrate electrochemical reduction: By-passing water hardness

Water matrix composition impacts water treatment performance. However, matrix composition impacts have rarely been studied for electrochemical water treatment processes, and the correlation between the composition and the treatment efficiency is lacking. This work evaluated the electrochemical reduction of nitrate (ERN) using different complex water matrices: groundwater, brackish water, and reverse osmosis (RO) concentrate/brine. The ERN was conducted using a tin (Sn) cathode because of the high selectivity towards nitrogen evolution reported for Sn electrocatalysts. The co-existence of calcium (Ca2+), magnesium (Mg2+), and carbonate (CO32−) ions in water caused a 4-fold decrease in the nitrate conversion into innocuous nitrogen gas due to inorganic scaling formation on the cathode surface. XRF and XRD analysis of fouled catalyst surfaces detected brucite (Mg(OH)2), calcite (CaCO3), and dolomite (CaMg(CO3)2) mineral scales formed on the cathode surface. Surface scaling created a physical barrier on the electrode that decreased the ERN efficiency. Identifying these main sources of ERN inhibition was key to devising potential fouling mitigation strategies. For this reason, the chemical softening pre-treatment of a real brackish water was conducted and this significantly increased nitrate conversion and faradaic efficiency during subsequent ERN treatment, leading to a lower electric energy consumption per order. Understanding the ionic foulant composition responsible for influencing electrochemically-driven technologies are the first steps that must be taken to move towards niche applications such as decentralized ERN. Thus, we propose either direct ERN implementation in regions facing high nitrate levels in soft waters, or a hybrid softening/nitrate removal system for those regions where high nitrate and high-water hardness appear simultaneously.

Investigation and management of nitrate poisoning in cattle: a case study

Nitrate poisoning is generally caused by ingestion of high levels of nitrate containing fodder and it usually occurs in late autumn in Bangladesh, mainly during a flush growth of green grasses after a dry period. This case report was based on a suspected nitrate poisoning in two Holstein Friesian (2 years age, pregnant; 3.5 years age milking) cows in a commercial dairy farm at Hathazari, Chattogram. The cows had a history of feeding German grass from grassland that was flooded by a nearby fertilizer company’s wastewater and after 6 hours of feeding of that grass the animals were showing clinical signs of inappetite, diarrhoea, mild dyspnea and distended abdomen. The suspected fodder samples were brought to the Department of Physiology, Biochemistry and Pharmacology laboratory, Chattogram Veterinary and Animal Sciences University, Chattogram for toxicological testing. In diphenylamine test, we detected a high concentration of nitrate in the supplied fodder. However, we could not measure the plasma nitrate concentration of affected animals. The affected cows were treated with slow intravenous administration of 1% methylene blue (20mg/kg body weight) and ascorbic acid (15mg/kg body weight) for every 8 hours until completely remission of all clinical signs. In addition, cattle were medicated liver tonic (15 ml per animals) for a period of one week. Feeding of nitrate containing grass was restricted. After three days of treatment, the animals were recovered.

Dietary Nitrate Does Not Improve Neuromuscular Performance And Match-play Demands In Elite Female Hockey Players.

PURPOSE: Beetroot juice is a commonly used ergogenic aid that contains high levels of inorganic nitrate (NO3-) and that its intake has proven effectivity at increasing blood nitric oxide (NO) concentrations. The ingestion of beetroot juice has shown good evidence of benefits in endurance sports while team sports has been barely studied. In our knowledge, only a few studies have been developed in team sports athletes. The present study was designed to compare the acute effects of beetroot juice supplementation on physical performance and match-play demands in elite female field hockey players METHODS: Eleven well-trained female hockey players (22.78 ± 5.12 years) participated during the preparatory period of their hockey season in this study. Participants were randomly divided into two groups undergoing a neuromuscular test battery with ingestion of 70 mL beetroot juice (6.4 mmol NO3-) or 70 mL placebo (0.04 mmol NO3-) in two separated days with one week between protocols. A neuromuscular test battery consisted in different test such as; countermovement jump (CMJ), isometric handgrip strength (IHS), and repeated sprint ability test (RSA) were realized. Afterwards a simulated hockey match play (2 x 20 minutes) was realized and the data was recorded by Global Positioning System (GPS). RESULTS: No significant improvements were observed in any physical parameters analysed comparing beetroot juice versus placebo ingestion, CMJ (p = 0.776), IHS (p = 0.829), RSA (p = 0.466). Therefore, no differences were reported in any physical match demands measured by GPS (i.e., total distance covered, number of accelerations/decelerations, etc) (p = 0.063-0.941) CONCLUSIONS: Beetroot juice acute supplementation did not produce any statistically significant improvement in physical performance or match-play demands in elite female field hockey players

English

Agriculture, which accounts for 70% of water abstractions worldwide, plays a major role in water pollution. Resulting pollution poses risks to aquatic ecosystems and humans. With the aim of evaluating the saprobic state of four hydro systems subject to pollution from intensive rubber cultivation, the present study was carried out within and around the Hevecam rubber plantation in Niete, South Region of Cameroon. The study was done from September 2019 to December 2020 with monthly sampling, physico-chemical water analysis and determination of ciliate diversity and distribution. Water in the study stations was acidic (6.40±0.31CU), with average temperature (25.20±0.56°C) and conductivity of up to 761.8 µs/cm. Conductivity values coupled with phosphates (up to 29.7 mg/L), herbicide residues are indicators of agricultural pollution on water quality. Station N2 showed the greatest ciliate abundance and species richness. The long dry season of 2020 showed the highest diversity and abundance. The saprobic index indicated moderate to high levels of organic pollution (2.16 to 3.67). Water quality was degraded with the impact of the agricultural pollution due to the presence of herbicide and fertilizer residues at stations N2 and N4. High levels of phosphates and nitrates have resulted in an increased organic load reflected in the saprobic indices; indicating average to high organic pollution.   Key words: Saprobic, Hevecam, organic pollution, anthropogenic, water quality.

Investigation of a Possible Relationship between Anthropogenic and Geogenic Water Contaminants and Birth Defects Occurrence in Rural Nebraska

Relatively high concentrations of anthropogenic (atrazine and nitrate) and geogenic (uranium and arsenic) water contaminants have been found in drinking water in rural Nebraska. This research assessed a potential association between birth defects occurrence and the contaminants mentioned above within selected Nebraska watershed boundaries. The prevalence of birth defects and the mean concentrations of the selected water contaminants were calculated. More than 80% of Nebraska watersheds had birth defect prevalences above the national average (5 cases per 100 live births). In the negative binomial regression analysis, a positive association was observed between higher levels of nitrate in drinking water and the prevalence of birth defects. Similarly, compared to watersheds with lower atrazine levels, watersheds with atrazine levels above 0.00 µg/L had a higher prevalence of birth defects. This study suggested that chronic exposure to the selected waterborne contaminants even below the legislated maximum contaminant levels may result in birth defects. It also highlighted the relationship between anthropogenic activities (agriculture practices), water contamination, and adverse health effects on children. An additional cohort study is recommended to support these findings so that regulations can be implemented in the form of continuous monitoring of water in private wells and improvements to agricultural practices.

Plasma Endothelial and Oxidative Stress Biomarkers Associated with Late Mortality in Hospitalized COVID-19 Patients.

Background: Coronavirus infectious disease 2019 (COVID-19) is a significant public health problem worldwide. COVID-19 increases the risk of non-pulmonary complications such as acute myocardial injury, renal failure, thromboembolic events, and multi-organic damage. Several studies have documented increased inflammation molecules, endothelial dysfunction biomarkers, and dysregulation of coagulation factors in COVID-19 patients. In addition, endothelium dysfunction is exacerbated by the oxidative stress (OxS) promoted by endocrine and cardiovascular molecules. Our objective was to evaluate whether endothelial and OxS biomarkers were associated with mortality in hospitalized COVID-19 patients. Methods: A prospective cohort study was performed. Patients ≥18 years old with confirmed COVID-19 that required hospitalization were included in a prospective cohort study. Endothelium and oxidative stress biomarkers were collected between 3 and 5 days after admission. Results: A total of 165 patients were evaluated; 56 patients succumbed. The median follow-up was 71 days [23–129]. Regarding endothelial dysfunction and OxS biomarkers, patients who did not survive had higher levels of nitrates (0.4564 [0.1817–0.6761] vs. 0.2817 [0.0517–0.5], p = 0.014), total nitrates (0.0507 [−0.0342–0.1809] vs. −0.0041 [−0.0887–0.0909], p = 0.016), sE-Selectin (1.095 [0.86–1.495] vs. 0.94 [0.71–1.19], p = 0.004), and malondialdehyde (MDA) (0.50 [0.26–0.72] vs. 0.36 [0.23–0.52], p = 0.010) compared to patients who survived. Endothelial and OxS biomarkers independently associated with mortality were sE-selectin (HR:2.54, CI95%; from 1.11 to 5.81, p = 0.027), nitrates (HR:4.92, CI95%; from 1.23 to 19.63, p = 0.024), and MDA (HR: 3.05, CI95%; from 1.14 to 8.15, p = 0.025). Conclusions: Endothelial dysfunction (sE-selectin and nitrates) and OxS (MDA) are independent indicators of a worse prognosis in COVID-19 patients requiring hospitalization.

Seasonal patterns of coccolithophores in the ultra-oligotrophic South-East Levantine Basin, Eastern Mediterranean Sea

Coccolithophore seasonality was examined in the southeastern Mediterranean Sea, both at the edge of the coastal shelf and in the open sea offshore Israel during 2018–2019. Oceanographic conditions varied seasonally between markedly stratified and ultra-oligotrophic from April to September and water column-mixing with relatively higher nitrate levels from October to February. Coccolithophores were quantified during the early (April), mid (July) and late (October) stratification period and in the mixing period (January). During stratification, cell densities progressively declined to <1.5 × 104 cells L−1, while both diversity and vertical differentiation of communities markedly increased. Emiliania huxleyi, Umbellosphaera spp., Syracosphaeraceae and Rhabdosphaeraceae as well as holococcolithophores were prevalent in the upper and mid-water layers. Florisphaera profunda characterized deeper sub-euphotic layers. During winter, mixing eroded the vertical zonation of species and coccolithophore density increased up to ~3.5 × 104 cells L−1. Communities became largely dominated by E. huxleyi, coincident with higher nutrient availability. The observed composition of coccolithophore assemblages and succession patterns support previous descriptions that the eastern Mediterranean largely resembles oceanic gyre systems. At the shelf station, the presence of higher fractions of r-selected species, and the rarity of oligotrophic coccolithophores (namely Umbellosphaera irregularis and holococcolithophores), suggest a somewhat greater influence of nutrients towards the shore. Finally, cells from different life-cycle phases were identified for a variety of species, highlighting the clear ecological divergence between coccolithophore life-phases. These data represent important baseline values for this area of the global ocean which is affected by major climate and environmental changes.

FO–MD integrated process for nitrate removal from contaminated groundwater using seawater as draw solution to supply clean water for rural communities

Access to clean water has become a global concern in recent years, especially in rural communities due to the contamination of groundwater induced by intensive anthropogenic activities. The current study proposed a solution for this issue by the evaluation of the feasibility of forward osmosis (FO) coupled with membrane distillation (MD) to treat nitrate-contaminated groundwater using seawater as draw solution. The studied groundwater had high nitrate levels of 150 mg/L. The evaluation of different operating conditions indicated that working at lower FS concentration, higher DS concentration, higher DS temperature and under active layer draw solution (AL-DS) mode had positive effects on FO water flux. However, reverse solute flux and nitrate flux showed an increment with increasing FS concentration, DS concentration and DS temperature. Application of optimal operating conditions on real groundwater using seawater as DS, during 15 h of continuous operating time, led to obtain FO water flux of 6.25 LMH, MD permeate flux of 12.44 LMH, nitrate flux of 0.69 gMH, reverse solute flux of 20.24 gMH, FO rejection rate of 98.34% and MD salt rejection rate of 99.05%. Moreover, FO–MD process produced freshwater with almost free-nitrate content and very low conductivity of 78 µS/cm suitable for drinking and irrigation purposes. Thus, the integrated FO–MD process can be applied efficiently to remove nitrate from contaminated groundwater.

The Effect of Flushing on the Nitrate Content and Postharvest Quality of Lettuce (Lactuca sativa L. Var. Acephala) and Rocket (Eruca sativa Mill.) Grown in a Vertical Farm

Hydroponics is the most widely used technique in closed cultivation environments, and this system is often used for the cultivation of baby leaf vegetables. These species can accumulate high levels of nitrates; for this reason, the control of growing conditions is a crucial factor for limiting their content, especially in protected cultivations. The aim of this work was to reduce nitrate accumulation in leafy vegetables grown in a vertical farm while preserving the quality at harvest as well as during storage. This objective was achieved by completely replacing the nutrient solution with water a few hours before harvest (“flushing”). The trials were carried out on lettuce (Lactuca sativa L. Var. Acephala, cv. Greenet) and rocket (Eruca sativa Mill., cv. Rome). Three independent trials were conducted on lettuce, applying the flushing treatment 24 h and 48 h prior to harvest. One trial was conducted on rocket, applying the treatment 48 h before harvesting. Sampling and related analyses were carried out at harvest and during the storage period to determine chlorophyll, leaf fluorescence, total sugars, chlorophyll (a + b), carotenoids, phenolic index, anthocyanins and nitrate content. Moreover, relative humidity (RH%), O2% and CO2% determination inside the package headspace were monitored during storage. The results obtained indicate that it is possible to reduce the nitrate concentration by up to 56% in lettuce and 61% in rocket while maintaining the product quality of baby leaves by replacing the nutrient solution with tap water before harvest.

ACTIVITY OF NITRO-OXIDATIVE PROCESSES IN PREGNANT WOMEN WITH IDIOPATHIC ARTERIAL HYPOTENSION

Primary violation of vascular tone and reactivity is considered the main hemodynamic link in the pathogenesis of idiopathic arterial hypotension (IAH). Two gaseous messengers - nitric oxide (NO) and hydrogen sulfide (H2S) play an important role in the regulation of vascular tone.&#x0D; The research aims at determining the state of the NO system and the level of H2S in women with IAH and their effect on the uteroplacental blood flow.&#x0D; Material and Methods. A number of 20 pregnant women with IAH at 40-41 weeks of gestation were examined (group I); the second group included 20 pregnant women with normotony at 39-40 weeks of gestation. The concentration of the complex of nitrates and nitrites was determined by the reaction of formation of a colored complex by Griss reagent. The content and production of peroxynitrite in alkali and alkaline earth metals were determined according to the procedure described by Vanuffelen et al. Detection of hydrogen sulfide content in blood plasma was performed by the method of Dombkowski et al. Studies of uteroplacental blood flow were performed on ultrasonic diagnostic device "SA-8000 EX" using color Doppler mapping and pulse mapping dopplerometry of the blood flow in the uterine arteries (UA). The assessment of blood flow velocity curves was carried out by determining the pulsation index (PI) in both arteries taking into account the average value.&#x0D; Results. The results of the study showed that an average level of nitrites and nitrates in pregnant women with IAH was 37.0% higher than in women with normotension, and peroxynitrite values were 2.4 times higher, respectively. In contrast, the concentration of H2S in pregnant women with IAH was almost 1.4 times lower, than in pregnant women with normal blood pressure. Doppler study of blood flow indices in UA showed a moderate increase in PI in 28.0% of pregnant women with IAH. Thus, indices of vascular resistance in UA of pregnant women with IAH were higher, on average, by 19.0% than in pregnant women with normotension.&#x0D; Conclusions. High levels of nitrites and nitrates in pregnant women with IAH form the basis for the development of nitrosatous stress, which is accompanied by increasing concentration of highly toxic peroxynitrite. Significant increase in peroxynitrite is one of the causes of endothelial dysfunction. In pregnant women with IAH due to the low content of H2S - its vasoconstrictive effects are prevalent, which may indicate an indirect interaction between both of these systems of vasoregulation.

Water Pollution from Agriculture and Industry

Continued water quality impairment has introduced serious environmental concerns for health, stream life, agriculture, and industry. In general, water pollution is a resultant of agricultural and industrial activities. We handpicked 150 samples of drinkable water from various parts of the Faisalabad City. The findings revealed that locations fed by industrial waste matter had higher nitrate level, whereas places with superior drainage had lower nitrate content. Almost all the factors in general produced major effects on the leaching of fertilizer (NO3-N) into the soil outline. The current research found that nitrogenous fertilizer in the form of NO3-N was leached up to 150 cm into the soil. In Pakistan, the water table was within 150 cm of the ground surface on 30 percent of the 41 million acres examined. The municipal and industrial wastes of Faisalabad cannot be separated, as industries are situated in residential areas. The mixture is discharged into open land or into drains. None of the samples contained Zn in the tolerance limit (TL refers to the concentration higher than maximum permissible limit). MPL decrease with an increase in distance of the source from the sullage carrier. Fe, Cu and Mn, the results indicate that the sullage carrier has contaminated the ground water up to 300 meters and no water sample was found within TL within 300 meters distance. The results indicate that Fe, Cu, and Mn concentration in ground water has reached to problematic level along unlined section of the sullage carrier. Thus, in this zone a severe Fe, Cu and Mn toxicity has been identified. Pb however, the situation was somewhat different because none of the samples was found within TL after 50 meters distance of source from such sullage carrier. The result of Fe indicates problem in some water samples collected along lined section of sullage carrier. The same situation prevailed for Cu and Mn. Both the metals have contaminated the ground water up to 150 meters. The results of Pb were similar as in case of unlined section of the sullage carrier but it has some problem up to 25 meters. This paper describes some aspects of surface and subsurface water pollution, in addition to best management practices and remedial measures required for minimization environmental hazards.

Nitrogen Cycling Across a Salinity Gradient From the Pearl River Estuary to Offshore: Insight From Nitrate Dual Isotopes

AbstractDual isotope measurements were performed on nitrate (δ15N‐NO3− and δ18O‐NO3−) in the Pearl River Estuary (PRE) and the adjacent northern South China Sea (NSCS) to investigate nitrate sources and its biogeochemical processes during rainy season. Our results indicated that in the PRE, high nitrate levels were associated with the intense human activities in PRE delta, the sources of which included the reduced nitrogen (N) fertilizer (29%), SN (nitrate derived from soil N) (18%), manure and sewage (10%), and atmospheric deposition (7%). In the nearshore area, nitrate was characterized by relatively high δ15N‐NO3− and δ18O‐NO3− values suggestive of incomplete nitrate assimilation. Besides, nitrification might be significant in the intermediate and bottom waters due to ammonia release from remineralization of sinking and sedimented organic matter (OM). In the offshore area, nitrate was depleted due to nearly complete utilization, and δ15N‐NO3− and δ18O‐NO3− showed moderate values. In addition, δ18O‐NO3− exhibited a clear vertical gradient with a decrease from the surface to the bottom. A coupled nitrification‐denitrification process in sediment porewater was supposed, which left isotope imprints in bottom waters of the offshore area. In surface waters from the nearshore to the offshore area, although assimilation was the prominent process, the δ15N‐NO3− and δ18O‐NO3− relationship deviated from the 1:1 line, suggesting significant contribution of atmospheric deposition that increased offshore. Our study suggests the external source of nitrate shifts from anthropogenic nitrogen to atmospheric source in the continuous river–estuary–ocean system, and nitrification‐denitrification become more active as it goes seaward.

Iron release and characteristics of corrosion scales and bacterial communities in drinking water supply pipes of different materials with varied nitrate concentrations

Changes of drinking water quality can lead to iron release in drinking water distribution systems (DWDSs), which is one of the most important reasons for the deterioration of tap water quality. The objective of this study was to investigate the effects of nitrate on the iron release and characteristics of corrosion scales and bacterial communities in DWDSs using simplified pipe section reactors. With nitrate addition, the percentages of goethite (α-FeOOH), hematite (Fe2O3), and lepidocrocite (γ-FeOOH) in scales were decreased, whereas those of magnetite (Fe3O4) were increased. The growth of nitrate-reducing bacteria (NRB) was promoted significantly, with the fractions of 25.70% and 23.79% in the steel and cast iron pipes, respectively. Approximately 3.40% of iron-reducing bacteria (IRB) were reduced in both pipes. Moreover, under higher nitrate levels, iron release was inhibited obviously. The maximum decreased percentages of total iron in the steel and cast iron pipes were 44.90% (with 10.00 mg/L NO3−-N) and 88.29% (with 30.00 mg/L NO3−-N), respectively. This study may be helpful for improving drinking water supply safety.

Nitrogen assimilation-associated enzymes and nitrogen use efficiency of Pyropia yezoensis (Rhodophyta) in nitrate-sufficient conditions

Pyropia yezoensis (Rhodophyta), an economically valuable marine red alga, undergoes changes in nitrogen levels during growth. The increased availability of nitrogen sources in seawater promotes algal growth and increases the photosynthetic pigment content. Results of the experiment for determining nitrate uptake rates showed that the thalli rapidly absorb nitrate in the first two days and accumulate large amounts of nitrate and nitrite on the first and third days, respectively. Interestingly, although the thalli absorbed high levels of nitrate and grew rapidly under nitrate-sufficient conditions, the nitrogen utilization efficiency decreased. In the present study, we cloned nitrogen assimilation-associated enzymes, nitrate reductase, nitrite reductase, and glutamine synthetase. Additionally, results of the reverse transcription-polymerase chain reaction assay indicated that the levels of these enzymes increase at 12 h in response to nitrate sufficiency, while their expression is inhibited at 24 h. We propose that excessive ammonium and amino acids produced through metabolism inhibit the nitrate reduction process. This experiment complements the metabolism and accumulation of nitrate in P. yezoensis under nitrate-sufficient conditions.

Improved lakeshore sediment microenvironment and enhanced denitrification efficiency by natural solid carbon sources

At present, the high level of nitrate in tailwater of wastewater treatment plants (WWTPs) has continued to cause serious environmental problems. In current study, wood chips and bark, serving as natural solid carbon source (NSCS), were applied to enhance the denitrification capacity of lakeshore sediment to remove superabundant nitrate in tailwater. The results show that NSCS had a positive effect on denitrification process for lakeshore sediment and increased the total phosphorus removal capacity by 212%–601%. Comparatively, wood chips were better in enhancing denitrification ability of lakeshore sediment for a longer time. At the 70th day, the nitrate elimination (NEL) of the wood chip-sediment integrated system (WSIS) was 20% and 9% higher than the control system (CS) and bark-sediment integrated system (BSIS), respectively. For the WSIS, the microbial activity and the abundance of nicotinamide adenine dinucleotide (NADH) were significantly increased, and the sediment anaerobic zone was rapidly formed, which were conducive to the denitrification of the sediment. At the DNA level, both groups presented an inconsistency in the abundance of functional denitrification genes with the NEL. At the enzyme level, wood chips significantly increased the nitrate and nitrite reductase activities of the sediment, and promoted denitrification. From the perspective of microbial communities, wood chips highly promoted the abundance of norank_f_BIrii41 Proteobacteria and Ruminclostridum more than other denitrifying and potential denitrifying bacteria in the process of sediment denitrification enhancement.

Heterogeneous HONO formation deteriorates the wintertime particulate pollution in the Guanzhong Basin, China

Despite implementation of strict emission mitigation measures since 2013, heavy haze with high levels of secondary aerosols still frequently engulfs the Guanzhong Basin (GZB), China, during wintertime, remarkably impairing visibility and potentially causing severe health issues. Although the observed low ozone (O3) concentrations do not facilitate the photochemical formation of secondary aerosols, the measured high nitrous acid (HONO) level provides an alternate pathway in the GZB. The impact of heterogeneous HONO sources on the wintertime particulate pollution and atmospheric oxidizing capability (AOC) is evaluated in the GZB. Simulations by the Weather Research and Forecast model coupled with Chemistry (WRF-Chem) reveal that the observed high levels of nitrate and secondary organic aerosols (SOA) are reproduced when both homogeneous and heterogeneous HONO sources are considered. The heterogeneous sources (HET-sources) contribute about 98% of the near-surface HONO concentration in the GZB, increasing the hydroxyl radical (OH) and O3 concentration by 39.4% and 22.0%, respectively. The average contribution of the HET-sources to SOA, nitrate, ammonium, and sulfate in the GZB is 35.6%, 20.6%, 12.1%, and 6.0% during the particulate pollution episode, respectively, enhancing the mass concentration of fine particulate matters (PM2.5) by around 12.2%. Our results suggest that decreasing HONO level or the AOC becomes an effective pathway to alleviate the wintertime particulate pollution in the GZB.