Different Concentrations Of Nitrate Research Articles

Unraveling the two-sided effect of nitrate on aerobic granulation

Aerobic granular sludge (AGS) is a promising technology in wastewater treatment which has gained considerable attention. This study aims to unravel the two-sided effect of nitrate on AGS granulation. By feeding different concentrations of nitrate (30 and 66 mg/L), better granulation was achieved in experimental groups compared to control group without nitrate feeding. However, after three-months cultivation, the mean granule size of control group drastically exceeded the nitrate-feeding groups where disintegration of granules occurred. The variation in extracellular polymeric substances (EPS) was consistent with the trend of granulation, suggesting its important role in AGS granulation. An in-depth analysis indicated that this two-sided effect of nitrate was rooted in denitrification, which had been promoted by nitrate feeding. The short-term promoting effect of granulation was due to the alkalinity generated by denitrification, which was beneficial for calcium retention, thereby providing micronuclei for granule growth and promoting EPS secretion. The inhibiting effect of granulation stemmed from the suppressive concentration of c-di-GMP caused by denitrification, and it became pronounced under long-term cultivation, inducing a decline in EPS. In microbial level, nitrate significantly affected the denitrifying and EPS-producing bacteria, such as Micropruina, Thauera and Flavobacterium. The changes in these two types of bacteria were related to denitrification and EPS variation. This given further evidence for the two-sided effect of nitrate on AGS granulation. This study has highlighted the potential effects of nitrate on aerobic granulation and provided references for utilizing AGS in nitrate-containing wastewater.

Removing nutrients in recirculating aquaculture system wastewater from Nile tilapia culture via Spirulina cultivation: Optimizing sodium bicarbonate concentration and micronutrient supplementation

Recirculating aquaculture system (RAS) wastewater from Nile tilapia (Oreochromis niloticus) culture raises environmental concerns, necessitating proper treatment prior to discharge. Phytoremediation using Spirulina offers a promising solution by enabling the simultaneous removal of nutrients from wastewater while also producing valuable biomass. This study aimed to optimize the sodium bicarbonate (NaHCO3) concentrations (3.36, 8.40, and 16.80 g/L) for achieving maximum nutrient treatment efficiency and Spirulina production in RAS wastewater from Nile tilapia culture, without external nitrogen and phosphorus supplementation. Additionally, this study examined the effect of different concentrations of nitrate (10 to 120 mg NO3-N/L) that are naturally present in RAS wastewater and Zarrouk's micronutrient supplementation on Spirulina production and nutrient treatment efficiency. The optimal NaHCO3 concentration for achieving maximum Spirulina production and effective nutrient treatment efficiency was found to be 8.40 g/L. At this concentration, high nitrate treatment efficiencies, reaching up to 80%, were observed specifically in RAS wastewater containing 10 to 50 mg NO3-N/L, while excellent phosphate treatment efficiencies, up to 99%, were found across all nitrate concentrations. Moreover, Spirulina biomass (X) reach a saturated growth of 0.398 g DW/L (6.09 mg Chl a/L) in RAS wastewater with a nitrate concentration of 50 to 120 mg NO3-N/L. Furthermore, the Pearson correlation coefficients revealed that the factor determining Spirulina growth in RAS wastewater with nitrate 10–50 mg NO3-N/L was nitrate, whereas in RAS wastewater with nitrate 80–120 mg NO3-N/L, it was NaHCO3. By supplementing Zarrouk's micronutrient at 25% to RAS wastewater containing 120 mg NO3-N/L and 16.80 g/L of NaHCO3, Spirulina biomass could be enhanced to reach 1.525 g DW/L (6.09 mg Chl a/L), while achieving a nitrate treatment efficiency of 86%.

A Turbidity-Compensation Method for Nitrate Measurement Based on Ultraviolet Difference Spectroscopy

To solve the problem that turbidity in water has a significant effect on the spectra of nitrate and reduces the accuracy of nitrate detection, a turbidity-compensation method for nitrate measurement based on ultraviolet difference spectra is proposed. The effect of turbidity on the absorption spectra of nitrate was studied by using the difference spectra of the mixed solution and a nitrate solution. The results showed that the same turbidity had different effects on the absorbance of different concentrations of nitrate. The change in absorbance due to turbidity decreased with an increase in the nitrate concentration at wavelengths from 200 nm to 230 nm, although this change was constant when the wavelength was greater than 230 nm. On the basis of this characteristic, we combined the residual sum of squares (RSS) and interval partial least squares (iPLS) to select wavelengths of 230-240 nm as the optimal modeling interval. Furthermore, the turbidity-compensation model was established by the linear fitting of the difference spectra of various levels of turbidity. The absorption spectra of the nitrate were extracted by subtracting the turbidity-compensation curve from the original spectra of the water samples, and the nitrate concentration was calculated by using a partial least squares (PLS)-based nitrate-prediction model. The experimental results showed that the average relative error of the nitrate predictions was reduced by 50.33% to 1.33% by the proposed turbidity-compensation method. This indicated that this method can better correct the deviation in nitrate's absorbance caused by turbidity and improve the accuracy of nitrate predictions.

Nitrogen Application Alleviates the Adverse Effects of Defoliation Stress on Lolium perenne L. by Enhancing the Antioxidant System and Promoting Photosynthesis

Perennial grasses undergo compensatory growth after defoliation. Nitrate is the main nitrogen source for the growth of perennial ryegrass and plays a significant role in plant resistance to stress. The aim of the study was to understand the physiological mechanism of ryegrass in response to defoliation stress under different nitrate supplies and to explore possible ways to alleviate defoliation stress. We performed pot experiments where 12-week-old ryegrass plants grown in low (0.05 mM KNO3) or moderate nitrate (5 mM KNO3) conditions were defoliated and subsequently supplied with different concentrations of nitrate following defoliation treatments. During the regrowth stage, the regrowth rate, biomass, photosynthetic parameters, and the response of the antioxidant system to low or moderate nitrate supply of ryegrass were investigated. The results showed that moderate nitrate supply after defoliation increased the content of photosynthetic pigments in ryegrass and improved its photosynthetic efficiency. In addition, adding moderate nitrate after defoliation increased the activity of antioxidant enzymes and the accumulation of osmotic regulating substances, thereby enhancing plant resistance, effectively reducing the damage to plants caused by defoliation stress, and promoting plant regrowth, especially for plants grown in a low nitrate environment before defoliation. Therefore, this study showed that the addition of exogenous nitrate could counteract some of the adverse effects of defoliation stress on the growth and development of ryegrass.

Growth and Mineral Relations of Beta vulgaris var. cicla and Beta vulgaris ssp. maritima Cultivated Hydroponically with Diluted Seawater and Low Nitrogen Level in the Nutrient Solution

There is an increasing interest in the use of seawater in horticulture. The objective of this study was to evaluate Beta vulgaris var. cicla (Swiss chard) and its wild ancestor B. vulgaris spp. maritima (sea beet) as potential crop species for seawater hydroponics or aquaponics. Both species were grown in a floating system for leaf production with recurrent harvests. The nutrient solutions contained different concentrations of nitrate (1 and 10 mM) and a synthetic sea salt (0 and 10 g L−1), in a factorial design, where the saline solution with a low nitrate level intended to mimic the typical nutritional conditions of saltwater aquaponics. In both species, increasing the salinity or reducing the N level in the nutrient solution reduced the crop yield and total dry biomass. In both Swiss chard and sea beet, the use of saline water resulted in a lower leaf concentration of K, Ca, Cu, and Mn, and a greater content of Na and Cl. In Swiss chard, an increase in Na and Cl and a decrease in K leaf content were found in successive harvests. On average, sea beet showed a higher leaf production and accumulation of nitrate than Swiss chard.

Investigating the Molecular Mechanism of Optimized Bio Denitrification by Thiobacillus denitrificans in the Presence of Metal Nanostructures in Bioreactor

Nitrate contamination of groundwater and surface water has become a serious problem. Zero-capacity iron (Fe0) nanoparticles are of great interest for the purification of toxic compounds from water. The aim of this study was to synthesis and optimize starch-coated “St” and carbon quantum dot-coated “CQD” Fe0 nanoparticles (St-Fe0 and CQD-Fe0) and investigate their role in bio denitrification and expression of nirS, narH and recA genes using the q-PCR technique. This study has a non-treatment control. The structural and morphological characteristics of nanoparticles were determined by XRD, TEM, FE-SEM and FTIR. Two important operating parameters including temperature (̊C) and nanoparticles concentration (g l−1) influencing the bio denitrification process of Thiobacillus denitrificans in the presence of nanoparticles were optimized by the response surface method (RSM). The FTIR spectrum confirmed the formation of CQD-Fe0 bonds. The average diameter of CQD-Fe0 nanoparticles was in the range of 29.31 to 38.32 nm. Denitrification in the presence of St-Fe0 and CQD-Fe0, with increasing temperature (35 C°) and nanoparticle concentration (1 g l−1), was 71.42% and 73.43%, respectively. After determining the optimal conditions, bio denitrification in the presence of nanoparticles at different concentrations of nitrate was investigated in a moving bed bioreactor. According to the results, in the discontinuous conditions, bio denitrification efficacy of Thiobacillus denitrificans in the presence of St-Fe0 and CQD-Fe0 nanoparticles was 80.10% and 79.83%, respectively. While in the bioreactor, denitrification efficacy in the presence of St-Fe0 and CQD-Fe0 was increased to 94.07% and 95%, respectively. In other words, bio denitrification of microorganisms in the moving bed bioreactor in the presence of CQD-Fe0 was higher compared to St-Fe0. The results of this study showed that the expression of all three genes nirS, narH and recA in cells treated with St-Fe0 and CQD-Fe0 significantly increased compared to the control group, which indicates the high impact of these nanoparticles, especially CQD-Fe0 on bio denitrification of this microorganism.

Metagenomic analysis of denitrifying phosphorus removal in SBR system: Comparison of nitrate and nitrite as electron acceptors

Denitrifying phosphorus removal (DPR) is a novel technology for removing phosphorus and nitrogen with low energy requirements. Still, the metagenomic analysis comparing the effect of different electron acceptors on DPR has not been studied clearly. In this study, Nitrate-DPR and Nitrite-DPR were established using different concentrations of nitrate and nitrite as electron acceptors. The results showed that the nitrogen and phosphorus removal efficiency of Nitrite-DPR could reach 99%, which was significantly higher than that of Nitrate-DPR. The sludge settling ability of Nitrite-DPR was also enhanced. The high-throughput sequencing analysis indicated that unclassified_g_Thauera, Chloroflexi_bacterium, Betaproteobacteria_bacterium, and Gammaproteobacteria_bacterium were the main functional bacteria in Nitrate-DPR, while in the Nitrite-DPR, Candidatus_Contendobacter_sp., unclassified_g_Thauera, Candidatus_Competibacteraceae_bacterium, Rhodocyclaceae_bacterium, and Xanthomonadaceae_bacterium were the main ones. Metagenome sequencing analysis further revealed the superior performance of Nitrite-DPR. A series of functional genes, for example, ActP, ACK, PTA and ACS (dominated the synthesis and decomposition of intracellular carbon source), Nir, Nor and Nos (dominated nitrogen metabolism), along with ppk, adk and ppx (dominated phosphorus cycle), were all significantly increased in nitrite-electron acceptor system. It is noted that T6SS functional genes, related to the resistance of microorganisms to environmental stress, were also increased in Nitrite-DPR significantly, which accounted for the significant increase in tightly bound extracellular polymeric substances (TB-EPS) protein in Nitrite-DPR to some extent. The DPR mechanism was deeply explored in this study, and a theoretical basis for the practical application was established.

Development of a spectroscopic approach for non-destructive and rapid screening of cucumbers based on maximum limit of nitrate accumulation

In this research, a non-destructive and low-cost approach based on Vis/NIR spectroscopy was developed for rapid measurement of nitrate concentrations in cucumbers and screening of the samples based on maximum limit of nitrate accumulation. Vis/NIR spectra of intact cucumbers including both field and greenhouse samples with different concentrations of nitrate were analyzed. PLS models were developed based on the pre-processed spectra and reference measurements. Moreover, PCA-DA classification models with different methods of linear, quadratic and Mahalanobis were developed to discriminate the samples based on maximum limit of nitrate accumulation according to Iranian National Standardization Organization (INSO) and World Health Organization (WHO), as well as based on the type. The best PLS model for prediction of nitrate concentrations in the cucumbers was achieved using D2 pre-processing method (rp =0.87, SEP=60.92 mg kg−1, RPD=2.07). It was concluded that Vis/NIR spectroscopy is adequate for screening the cucumbers based on their nitrate concentrations. The results also confirmed that this technology combined with PCA-DA is appropriate (accuracy=72.22%, sensitivity=76.74%, specificity=54.55%) and fairly suitable (accuracy=64.81%, sensitivity=59.26%, specificity=70.37%) for screening of the cucumbers based on maximum limit of nitrate accumulation according to INSO and WHO, respectively. It was excellent technology for classification of the cucumbers based on their type (accuracy=94.44%, sensitivity=93.55%, specificity=95.65%). Consequently, the proposed spectroscopic approach can be used for safety assessment of cucumbers as a rapid method with easy and out-of-laboratory usability.

Co-culturing Hyphomicrobium nitrativorans strain NL23 and Methylophaga nitratireducenticrescens strain JAM1 allows sustainable denitrifying activities under marine conditions.

BackgroundHyphomicrobium nitrativorans strain NL23 and Methylophaga nitratireducenticrescens strain JAM1 are the principal bacteria involved in the denitrifying activities of a methanol-fed, fluidized-bed marine denitrification system. Strain NL23 possesses the complete denitrification pathway, but cannot grow under marine conditions in pure cultures. Strain JAM1 is a marine bacterium that lacks genes encoding a dissimilatory nitrite (NO2−) reductase and therefore cannot reduce NO2−. Here, we report the characterization of some of their physiological traits that could influence their co-habitation. We also perform co-cultures to assess the potential synergy between the two strains under marine and denitrifying conditions.MethodologyAnoxic planktonic pure cultures of both strains were grown with different concentrations of nitrate (NO3−). Anoxic planktonic co-cultures could only be cultured on low NaCl concentrations for strain NL23 to grow. Biofilm co-cultures were achieved in a 500-mL bioreactor, and operated under denitrifying conditions with increasing concentrations of NaCl. NO3− and NO2− concentrations and the protein content were measured to derive the denitrification rates. The concentrations of both strains in co-cultures were determined by quantitative PCR (qPCR). Ectoine concentration was measured by mass spectrometry in the biofilm co-culture. The biofilm was visualized by fluorescence in situ hybridization. Reverse-transcription-qPCR and RNA-seq approaches were used to assess changes in the expression profiles of genes involved in the nitrogen pathways in the biofilm cultures.ResultsPlanktonic pure cultures of strain JAM1 had a readiness to reduce NO3− with no lag phase for growth in contrast to pure cultures of strain NL23, which had a 2-3 days lag phase before NO3− starts to be consumed and growth to occur. Compared to strain NL23, strain JAM1 has a higher µmax for growth and higher specific NO3− reduction rates. Denitrification rates were twice higher in the planktonic co-cultures than those measured in strain NL23 pure cultures. The biofilm co-cultures showed sustained denitrifying activities and surface colonization by both strains under marine conditions. Increase in ectoine concentrations was observed in the biofilm co-culture with the increase of NaCl concentrations. Changes in the relative transcript levels were observed in the biofilm culture with genes encoding NapA and NapGH in strain NL23. The type of medium had a great impact on the expression of genes involved in the N-assimilation pathways in both strains.ConclusionsThese results illustrate the capacity of both strains to act together in performing sustainable denitrifying activities under marine conditions. Although strain JAM1 did not contribute in better specific denitrifying activities in the biofilm co-cultures, its presence helped strain NL23 to acclimate to medium with NaCl concentrations >1.0%.

Physiological and transcriptomic response of soybean seedling roots to variable nitrate levels

AbstractNitrate is the main nitrogen source for plant growth and development. Increasing evidence indicates that nitrate plays an important role in root growth and development. However, the effects of different concentrations of nitrate on the physiological and transcriptional response of soybean [Glycine max (L.) Merr.] root development at the seedling stage are not well understood. In this study, we found that both high and low concentrations of nitrate inhibited the growth and development of the soybean root system compared with optimal nitrate supply at the seedling stage. Using transcriptome sequencing technology, we identified 1,654, 1,283, and 2,083 significantly differentially expressed genes in soybean root grown under the low nitrate concentration, optimal nitrate concentration, and high nitrate concentration conditions, respectively. These genes were enriched in the Gene Ontology terms of metabolic process, catalytic activity, and membrane. The genes enriched in the pentose and glucuronate interconversions and glutathione metabolism pathways may play important roles during soybean root response to different concentrations of nitrate. In addition, the expression of 18 nitrate transporter genes changed significantly under different nitrate concentrations. Among them, the expression of two GmNPF6.3 genes was upregulated under the NL condition but downregulated under the NH condition, whereas six GmNPF7.3 genes exhibited opposite expression patterns. Taken together, our physiological data can enable a better understanding of the soybean root response under different nitrate concentrations, and the transcriptome data provide a list of candidate genes for further investigation of the mechanisms of root response under different nitrate concentrations.

A Quantitative Analysis on the Effect of Varying Nitrate Concentrations on pH levels on the Growth of Algae

The objective of this experiment was to determine what nitrate concentration and pH would provide the most optimal growth for algae. In order to determine this, algae from the American River was taken and grown in solutions with different concentrations of nitrate, and H+ ions. It was hypothesized that the algae would grow best in solutions with neutral pH levels or solutions with high nitrate concentrations. Different amounts of sodium nitrate were added to beakers with similar amounts of water and algae in order to create environments with varying concentrations of nitrate. Different amounts of NaOH and acetic acid were added to beakers with similar amounts of water and algae in order to simulate environments with varying pH levels. This experiment was conducted in order to determine how fertilizer runoffs affect algal growth. Fertilizer run offs carry nitrate ions into rivers and lakes, which cause algal blooms to form. It was hypothesized that as the concentration of nitrate increases, the growth rate of the algae would also increase. This is due to the fact that the literature supports the idea that as nitrate is added to rivers and lakes the number of algae present increases. The results from the experiment demonstrated that the most optimal concentration of nitrate in the water for algal growth was in between 1-2 Molar and that the most optimal pH for algal growth was in between 7-8.

EFFECT OF NITRATE AND PHOSPATE CONCENTRATION ON Spirulina platensis WITH INDOOR SCALE

One of the microalgae that are widely used in the industrial world is Spirulina platensis which has high nutritional content of protein, fatty acids, vitamins and antioxidants. In its growth, this microalgae requires media and the addition of macronutrients nitrate and phosphate which greatly affect the growth and productivity of S. platensis biomass. This study aims to determine the effect of nitrate and phosphate concentrations on S. platensis biomass on an indoor scale and to determine the optimal nitrate and phosphate concentrations to achieve maximum biomass. This research was conducted in August 2020 as an experimental method, with culturing S. platensis with the addition of different concentrations of nitrate and phosphate. The design used in this study was a Completely Randomized Design consisting of 5 treatments that are 0 ppm, 10 ppm, 20 ppm, 30 ppm, and 40 ppm, each treatment with 3 repetitions. The source of nitrate and phosphate used is NPK. Water quality parameters during culture with temperatures ranging from 29-30oC, salinity 25-26 ppt, and pH 8. The optimal concentrations of nitrate and phosphate to achieve the maximum biomass is in treatment C (30 ppm) with a total of biomass 0,43 g. Whereas in treatment D (40 ppm) the biomass did not show a significant increase because the dose was too high with a total of biomass only 0,299 g

Bradyrhizobium arachidis mediated enhancement of (oxy)matrine content in the medicinal legume Sophora flavescens.

Effect of rhizobial inoculation and nitrate application on the content of bioactive compounds in legume plants is an interesting aspect for interactions among microbes, plants and chemical fertilizers, as well as for cultivated practice of legumes. In this study, nitrate (0, 5 and 20mmoll-1 ) and Bradyrhizobium arachidis strain CCBAU 051107T were applied, individually or in combination, to the root rhizosphere of the medicinal legume Sophora flavescens Aiton (SFA). Then the plant growth, nodulation and active ingredients including (oxy)matrine of SFA were determined and compared. Rhizobial inoculation alone significantly increased the numbers and fresh weight of root nodules. Nodulation was significantly inhibited due to nitrate (5 and 20mmoll-1 ). Only oxymatrine was detected in the control plants without rhizobial inoculation and nitrate supplement, while both oxymatrine and matrine were synthesized in plants treated with inoculation of B. arachidis or supplied with nitrate. The content of oxymatrine was the highest in plants inoculated solely with rhizobia and was not significantly altered by additional application of nitrate. Combinations of B. arachidis inoculation and different concentrations of nitrate did not significantly change the concentrations of (oxy)matrine in the plant. In conclusion, sole rhizobial inoculation was the best approach to increase the contents of key active ingredients oxymatrine and matrine in the medicinal legume SFA.

Beetroot juice intake with different amounts of nitrate does not change aerobic exercise-mediated responses in heart rate variability in hypertensive postmenopausal women: A randomized, crossover and double-blind study

Background/ObjectiveTo compare the acute effects of a single dose of beetroot juice (BJ) with different concentrations of nitrate (NO3−) on heart rate variability (HRV) in postmenopausal hypertensive women. MethodsThirteen hypertensive postmenopausal women (58.1 ± 4.6 years of age and 27 ± 4 kg/m2 of BMI) completed the protocol that consisted of three visits with different beverage intakes in a randomized and crossover design. The three beverages were BJ with a high content of nitrate (high-NO3-), BJ with a low content of nitrate (low-NO3-), and an orange flavored non-caloric drink (OFD). Heart rate (HR) were evaluated during 20 min after sitting rest at 7:20 a.m. (baseline), after they drank one of the drinks, and remained at sitting rest for 120 min and then performed 40 min of aerobic exercise at 65–70% of the HR reserve on a treadmill. HR was recorded for 90 min after exercise for time, frequency, and non-linear domains of HRV index analysis. ResultsTwo-way ANOVA showed that there were no interaction effects (time∗sessions) in any of the HRV indexes after exercise in all three sessions. HRV indexes increased after exercise (p = <0.05) similarly in all three sessions when compared with the baseline time point. ConclusionTherefore, a single dose of BJ, independent of NO3− content, does not change aerobic exercise-mediated responses in HRV indexes in hypertensive postmenopausal women.

Autotrophic denitrification via nitrate as an effective approach for removal of dissolved sulfide in anaerobic reactors.

This work assessed the effect of adding different concentrations of nitrate (50-300 mg NO3 -·L-1) on the removal of dissolved and gaseous sulfide in an anaerobic reactor treating synthetic effluent containing sulfate (100 mg SO4 2-·L-1) and organic matter (1 g COD·L-1). Autotrophic denitrification, stimulated by the addition of nitrate, was demonstrated to be a very effective approach for removal of dissolved sulfide even in the presence of a high concentration of organic matter (complete removal with 50 mg NO3 - mg·L-1). However, it had a minor effect on H2S(g). Sulfide remained partially oxidized to elemental sulfur even with excess nitrate (100-300 mg NO3 - mg·L-1). Therefore, the competition for this electron acceptor between the autotrophic and heterotrophic denitrification pathways may have prevented the conversion of the generated sulfide into sulfate again. No evidence of inhibition of methanogenesis and sulfidogenesis was found during nitrate supplementation.

An Evaluation of Carbon Steel Corrosion in Nitrate Solution Using Electrochemical and Solution Analysis Methods

Nuclear power reactors offer a long term, cost efficient and sustainable method to produce electricity with very low greenhouse gas emissions. As nuclear reactors age and their lifetimes are extended, accurate assessment of the integrity and longevity of the reactor structural materials is increasingly important. Corrosion in the vicinity of a nuclear reactor core happens in the presence of high energy, ionizing radiation, which needs to be considered. In particular, the potential for accelerated (galvanic) corrosion attack on carbon steel (CS) adjacent to the dissimilar metal weld between CS (SA 36) and stainless steel (SS) (Type 304L) at the periphery of the annular gap must be addressed.The initial environment inside the gap of structural support for End Shield Cooling (ESC) System could be humid due to trapped water in its annular gap. The pH of the ESC System water is adjusted to around 10.4, but when it condenses onto the weld region the pH might change. The oxygen level, the humidity, and many other factors will change with time. In addition, ionizing radiation decomposes water into a range of redox active species ranging from highly oxidizing (e.g., •OH and H2O2) to highly reducing (e.g., •eaq -) whose concentrations evolve with time (1-4). Humid-air radiolysis produces nitric acid (HNO3), that can dissolve into the water (5). The radiation products will lower the pH of the water in the droplet.In this work, corrosion of CS is evaluated carefully, and the effect of all solution reactions on interfacial charge transfer reactions is considered.The effect of [NO3 -] and solution pH is studied by using potentiodynamic polarization experiments and corrosion potential measurements (Figure 1), along with solution analysis. The results of polarization measurements in the presence of 0.01 M and 0.1 M [NO3 -] (with initial pH 2.0) show that the oxidation reactions are implicitly influenced by the mass transfer of metal cations from the CS surface into the solution. Also, the comparison of the rate of corrosion measured using Tafel extrapolation method and those obtained from ICP measurements suggests that the Tafel extrapolation method enormously underestimate the corrosion rate (in this case by about 100 times for 8 h corrosion) and must be applied more carefully.In order to study the effect of pH, we have compared the electrochemical results in pH 2.0 and pH 6.0 obtained in different concentrations of nitrate. The results show that solution pH is a rate controlling factor and the metal oxidation is limited by the metal transfer even at potentials close to/at the corrosion potential, and this influence the rate of corrosion.The results of this work imply that solution reactions can alter the corrosion behavior of carbon steel and hence, its galvanic coupling with stainless steel.

Growth, lipid content, and fatty acid profile of freshwater cyanobacteria Dolichospermum affine (Lemmermann) Wacklin, Hoffmann, &amp; Komárek by using modified nutrient media

In this study, Dolichospermum affine was cultivated under starvation and limitation conditions, using six different concentrations of nitrate (NaNO3) and phosphate (K2HPO4) in BG-11 medium. The biomass, pigments, proteins, carbohydrates, lipids, triacylglycerol-TAG, and fatty acid responses to different modified media were examined in terms of cell density, dry biomass, optical density, growth rate, chlorophyll-a, carotene content, and lipid productivity. Molecular characterization of D. affine isolates was performed using Fourier transform–infrared spectroscopy (FT-IR) and polymerase chain reaction (PCR). In the 20-day batch culture period, one of the modified media, %50 N and P limitation (N-PLimitation), exhibited higher values than the others in terms of cell density (1.41 × 107 cells/mL), dry biomass (1.68 gL−1), optical density (1.26), growth rate (0.48 day−1), chlorophyll-a (3.76 μg L−1), and total carotenoid (12.99 μg L−1). The maximum percentage lipid content of D. affine was obtained in the control group at 10.67%. Fatty acid profiles have been investigated in six conditions and consisted of 10 fatty acids. The basic saturated fatty acid palmitic acid was (C16:0) for all conditions, and its rate was 40.61% for starvation of N and P (N-PDeprivation) conditions. Oleic acid (C18:1) rate was detected in all groups, but the highest rate was found in the control group with 33.72%. In all conditions, TAG values were found similar, but the highest value was determined at 50% P and 100% N (PLimitation-NControl) (27.5%) modified media. Carbohydrate content (20.37%) was found to be high under N and P starvation (N-PDeprivation), while protein content (66.92%) was high under 50% N and 100% P (NLimitation-PControl) conditions. The results obtained from this study showed that nitrogen and phosphorus starvation and limitation affecting the biomass, valuable secondary metabolites and lipid accumulation and affected the fatty acid composition of D. affine cultures.

Transcriptome analysis of tobacco root response to different concentrations of nitrate

AbstractWe aimed to explore genes and transcription factors (TFs) in tobacco (Nicotiana tabacum L.) that were closely related to responses to different concentrations of nitrate (NO3−) in tobacco root. Cultivar K326 was used in this study. The RNA sequence data generated from K326 treated with high or low concentration of NO3− supplied at different time points (0, 6, 12, and 24 h) were analyzed to determine the transcriptome response of tobacco root to NO3− supply. The expression of numerous genes was altered after high and low NO3− treatment. Further analysis revealed 1981 and 3573 differentially expressed genes (DEGs) from low and high NO3− treatment groups, respectively. Comparative analysis identified 567 low‐NO3−‐specific, 2159 high‐NO3−‐specific, and 1414 commonly expressed genes. Combining short time‐series expression miner (STEM) and weighed gene co‐expression network analysis (WGCNA) results, 136 and 416 DEGs were identified from low and high NO3− groups, respectively, among which, 12 were TFs. In the constructed protein−protein interaction (PPI) network, three DEGs in high NO3− group (LOC107807186, LOC107792457, and LOC107786314) exhibited highest degrees. Within low NO3− group, LOC107798206, LOC107815159, and LOC107779796 had highest degrees. Among the 12 TFs, LOC107778750, LOC107810552, and LOC107804260 had the highest degrees. Our data provides valuable information about genes, especially the 12 TFs, which were induced by different concentrations of NO3− in tobacco root. These findings may be useful for identification of high or low NO3− treatment‐induced genes and TFs, as well as for understanding potential gene regulation mechanisms in response to NO3− supply in tobacco.

The effects of nitrate and phosphate on growth of algae, Ulva rigida

Abstract: The nutrients especially nitrate and phosphate are of the main limiting factors of algae growth in the aquatic ecosystems. The present study was conducted to examine the effects of different concentrations of nitrate and phosphate on growth of macro algae, Ulva rigida. For this purpose, algae were fed by various concentrations of nitrate and phosphate during 28 days in 300 l tanks in form of 4 experimental treatments with three replicates. The experimental treatments were: T1: 10 mg/l No3+5 mg/l Po4, T2: 20 mg/l No3+10 mg/l Po4, T3: 30 mg/l No3+15 mg/l Po4, T4: 40 mg/l No3+20 mg/l Po4 and one control treatment were considered. According to the results, all experimental treatments showed increased growth compared to the control treatment (P 0.05). The highest values of gain weight (88.02±0.74 g, nearly 17 times more than initial weight) and daily growth percent (60.57±1.29 %) were observed in algae of T3 and then T4 (daily growth percent: 42.95±1.56 %). In conclusion, our results suggest that a concentration of 30 mg/l No3+15 mg/l Po4 is more suitable for growth of macro algae, Ulva rigida.

Nitrate acute toxicity to post larvae and juveniles of Macrobrachium amazonicum (Heller, 1862).

The objective was to determine the median lethal concentration (LC50) of nitrate for post-larvae and juveniles of Macrobrachium amazonicum exposed for 96 h, and to identify histopathological alterations in the gills of juveniles exposed to nitrate. Post-larvae and juveniles of M.amazonicum were exposed to seven different concentrations of nitrate (0, 50, 100, 500, 1000, 1500 and 2000 mg.L-1) with four replicates (n = 10 prawn/experimental unit). The degree of damage to the branchial structure of juveniles was evaluated using standard histological processing with hematoxylin and eosin (H&E), subjected to the Organ Index (Iorg). LC50 values at 24, 48, 72 were estimated by the Trimmed Spearman Karber Method software and were respectively 1574, 638, 237, and 194 mg.L-1 for post-larvae and 1070, 286, 185 and 155 mg.L-1 for juveniles, respectively. From these results, the safety level of nitrate was estimated at 157, 64, 24 and 19 mg.L-1 for post-larvae and 107; 27; 18 and 16 mg.L-1 for juveniles, respectively for 24 h, 48 h, 72 h and 96 h. Damage to the gills in treatments with 100% mortality for nitrate corresponded to the high occurrence of progressive, regressive, circulatory and inflammatory damages. The other treatments, which caused lower mortality, mainly resulted in inflammation and regressive damage, whose occurrence increased with increasing concentration of nitrate. However, in closed systems, the use of anaerobic denitrifying filters or aquatic macrophytes is necessary to provide suitable water quality for the best productive performance, avoiding the negative influence of the accumulated nitrate.