Nitrite Concentrations Research Articles

A novel coupling process to replace the traditional multi-stage anammox process-sulfur autotrophic denitrification coupled anammox system.

A novel coupling process to replace the traditional multi-stage anammox process-sulfur autotrophic denitrification (SAD) coupled anaerobic ammonium oxidation (anammox) system was designed, which solved problems of nitrate produced in anammox process and low nitrate conversion rate caused by nitrite accumulation in SAD process. Different filter structures (SAD filter and anammox granular sludge) were investigated to further explore the excellent performance of the novel integrated reactor. The results of sequential batch experiments indicated that nitrite accumulation occurred during SAD, which inhibited the conversion of nitrate to dinitrogen gas. When SAD filter and anammox granular sludge were added to packed bed reactor simultaneously, the nitrate removal rate increased by 37.21% and effluent nitrite concentration decreased by 100% compared to that achieved using SAD. The stratified filter structure solved groove flow. Different proportion influence of SAD filter and anammox granular sludge on the stratified filter structure was evaluated. More suitable ratio of SAD filter to anammox granular sludge was 2:1. Proteobacteria (57.26%), Bacteroidetes (20.12%) and Chloroflexi (9.95%) were the main phyla. The dominant genera of denitrification functional bacteria were Thiobacillus (39.80%), Chlorobaculum (3.99%), norank_f_PHOs-HE36 (2.90%) and Ignavibacterium (2.64%). The dominant genus of anammox bacterium was Candidatus_Kuenenia (3.05%).

Impact of the near-physiological temperature on the in vitro maturation of bovine oocytes: A comparative proteomic approach

In vivo, the temperature inside preovulatory follicles of cows is approximately 1 °C lower than rectal temperature. However, standard bovine oocyte in vitro maturation (IVM) protocols use 38.5 °C based on rectal temperature. This study evaluated the effect of reducing IVM temperature to 37.5 °C on the proteomic profile of oocytes compared to the routine 38.5 °C. Nuclear maturation rate and cumulus cell (CC) expansion (30 COCs per group, 21 replicates) were assessed by observing the first polar body and using a subjective scoring method (0–4). Total nitrite concentrations in the culture medium were measured using the Griess method. Differential proteomics was performed using LC-MS/MS on pooled oocyte samples (500 matured oocytes per group, three replicates), followed by gene ontology enrichment, protein-protein interaction, and putative miRNA target analyses. No significant differences were observed between the groups in nuclear maturation, CC expansion, or nitrite concentration (P > 0.05). A total of 806 proteins were identified, with 7 up-regulated and 12 down-regulated in the treatment group compared to the control. Additionally, 12 proteins were unique to the control group, and 8 were unique to the treatment group. IVM at 37.5 °C resulted in the upregulation of proteins involved in protein folding and GTP binding, and the downregulation of enzymes with oxidoreductase activity and proteins involved in cytoskeletal fiber formation. Furthermore, 43 bovine miRNAs potentially regulating these genes (DES, HMOX2, KRT75, FARSA, IDH2, CARHSP1) were identified. We conclude that IVM of bovine oocytes at 37.5 °C induces significant proteomic changes without impacting nuclear maturation, cumulus cell expansion, or nitrite concentration in the IVM medium.

The effect of biofertilizers on nickel accumulation, nitrogen metabolism and amino acid profile of corn (Zea mays L.) exposed to nickel stress.

The issue of heavy metal pollution such as nickel poses a significant environmental concern, exerting detrimental effects on the growth and viability of plant life. Plants have various mechanisms to effectively manage heavy metal stress, including the ability to modify their amino acid type and content. This adaptive response allows plants to mitigate the detrimental effects caused by excessive heavy metal accumulation. The aim of this study was to investigate the effect of biofertilizers on nickel accumulation, nitrogen metabolism and amino acid profile of corn (Zea maysL.) cv. 'PL438' exposed to Ni stress. After disinfecting and soaking in water for 24 h, corn seeds were primed with bacterial biofertilizers (T2: NPK + FZ), fungal biofertilizers (T3: Arbuscular mycorrhizal fungi (AMF) + Trichoderma (T)), or a combination of them (T4: NPK + FZ + AMF + T) and were cultured by the hydroponic method in completely controlled conditions. Then, they were simultaneously exposed to nickel chloride at various rates (0, 75, or 150 µM) at the three-leaf stage. They were harvested two weeks later and were subjected to the measurement of Ni content, nitrate and nitrite content, nitrate reductase activity, and amino acid profile by high-performance liquid chromatography. The results showed that the application of Ni at higher rates increased Ni, nitrate, and nitrite contents and nitrate reductase activity. The study of Ni accumulation and TF revealed that Ni accumulated in the roots to a greater extent than in the shoots and TF was < 1 in all treatments. The shoot amino acid profile showed that the treatment of Ni+2 increased som amino acids such as aspartic acid, asparagine, serine, histidine, and glycine versus the control, whereas T4Ni+2 increased aspartic acid, glutamic acid, threonine and arginine. The change in amino acids in Ni-treated plants may play a key role in their adaptation to Ni stress. The findings indicate that biofertilizers played a crucial role in mitigating the negative impacts of Ni on corn plants through alterations in amino acid composition and decreased absorption and translocation of Ni.

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

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

Detection and Distribution of Residues and Additives in Meat and Meat Products in Zenica-Doboj Canton, Bosnia and Herzegovina

Objectives: Many additives are of essential importance for the taste and quality of products, however, many of them pose a danger to human health, and are subject to daily routine quality control of products intended for human consumption. In addition to additives, residues represent a major challenge as possible contaminants of products from the field to the dining table. Methods: Through the research, 85 samples of meat products (salami, sausages, dried meat products) were processed and all were analyzed for the presence of aflatoxin B1 (AFL B1), as well as for chlorides, nitrites and heavy metals (cadmium and lead). Results: The average content of AFL B1 in the meat samples was 0.048 µg/kg (0.019 to 0.105 µg/kg). Chloride content was detected in the range from 0.000 to 9.955 %m/m (average concentration 2.377 %m/m). The average nitrite content was 8.330 mg/kg (min. 0.550 – max. 45.705 mg/kg). Among the 85 processed samples, lead and cadmium were detected in 79 and 29 products (92.94% and 34.11%), with an average of 0.136 and 0.042 mg/kg, respectively. Lead was detected in the range from 0.000 to 3.474 mg/kg, and cadmium from 0.000 to 2.544 mg/kg. Conclusions: The results show the need for continuous monitoring of the amount of additives in meet products on the market, and regular monitoring of residues in products intended for human consumption. It is necessary to stick to proper hygienic practices during the preparation of the product at all stages from the field to the dining table. Keywords: residues, additives, lead, cadmium, public health

A novel probiotic formula, BLLL, ameliorates chronic stress-induced depression-like behaviors in mice by reducing neuroinflammation and increasing neurotrophic factors.

Introduction: Probiotics have been recognized for their various biological activities, including antioxidant and anti-inflammatory properties. This study investigates the therapeutic effect of a novel probiotic formula, BLLL, consisting of Bifidobacterium breve, Lactobacillus plantarum, Lactobacillus paracasei, and Lactobacillus helveticus, on chronic stress-induced depression-like behaviors in mice. Methods: The BLLL formula or phosphate-buffered saline (PBS) was given orally at a dose of 2, 4, or 8 × 1010 CFU/kg once daily for 10days in mice treated with chronic unpredictable stress (CUS) treated or vehicle. Depression-like behaviors were assessed using the sucrose preference test (SPT), the forced swimming test (FST), and the tail suspension test (TST). The mRNA and/or protein expression of interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), IL-4, IL-10, and chitinase-3-like protein 3 (CHI3L1, also known as Ym-1), as well as the concentration of nitrite, malondialdehyde (MDA), glutathione (GSH), and brain-derived neurotrophic factor (BDNF) in the hippocampus and medial prefrontal cortex were examined. Results: The BLLL formula treatment at a dose of 8 × 1010 CFU/kg, but not at a dose of 2 or 4 × 1010 CFU/kg, improved CUS-induced depression-like behaviors in mice, as shown by the decrease in immobility time in the TST and FST and the increase in sucrose intake in the SPT. Further analysis revealed that BLLL treatment suppressed the CUS-induced increase in IL-1β, IL-6, and TNF-α mRNA and protein levels, as well as the CUS-induced decrease in IL-4, IL-10, and Ym-1 mRNA and/or protein levels in the hippocampus and medial prefrontal cortex. In addition, treatment with the BLLL formula countered the CUS-induced increase in nitrite and MDA levels and the CUS-induced decrease in GSH content and BDNF concentration in the hippocampus and medial prefrontal cortex. Conclusion: These results demonstrate that the novel probiotic formula BLLL ameliorates chronic stress-induced depression-like behavior in mice by suppressing neuroinflammation and oxido-nitrosative stress in the brain.

Neuroprotective effect of cinnamic alcohol: A bioactive compound of Cinnamomum spp. essential oil

Cinnamic alcohol (CA) is a phenylpropanoid found in the essential oil of the bark of the genus Cinnamomum spp. Schaeff. (Lauraceae Juss.), known as cinnamon. To evaluate the neuroprotective effect of CA and its possible mechanism of action on mice submitted to the pentylenetetrazole (PTZ) induced epileptic seizures model. Behavioral, neurochemical, histomorphometric and immunohistochemistry analysis were carried out. The administration of CA (50–200 mg/kg, i.p., 30 min prior to PTZ and 0.7–25 mg/kg, i.p., 60 min prior to PTZ) increased the latency to seizure onset and the latency to death. The effects observed with CA treatment at 60 min were partially reversed by pretreatment with flumazenil. Furthermore, neurochemical assays indicated that CA reduced the concentration of malondialdehyde and nitrite, while increasing the concentration of reduced glutathione. Finally, histomorphometric and immunohistochemistry analysis revealed a reduction in inflammation and an increase in neuronal preservation in the hippocampi of CA pre-treated mice. Taken together, the results suggest that CA seems to modulate the GABAA receptor, decrease oxidative stress, mitigate neuroinflammation, and reduce cell death processes.

Regime shift in a coastal pelagic ecosystem with increasing human-induced nutrient inputs over decades

Human-induced nutrient inputs to global coastal waters are leading to increasing nutrients and escalating eutrophication. However, how aquatic ecosystem functioning responds to these changes remains insufficiently studied. Here we report the long-term changes in the nutrient regime and planktonic ecosystem functioning in the Daya Bay, a typical subtropical semi-enclosed bay experiencing rapid economic and social development for several decades. Time-series (from 1991 to 2018) data with a mostly quarterly resolution were collected to depict long-term changes in dissolved inorganic nutrients and plankton abundances, based on which we constructed simplified abundance size spectra (SASS) and plankton abundance ratios to describe the functioning of the planktonic ecosystem. The results revealed a long-term increase in system productivity but a decrease in integrated energy transfer efficiency of the planktonic ecosystem, with rising concentrations of dissolved inorganic nitrogen (DIN). Shifts in the nutrient regime and planktonic ecosystem functioning were detected at a tipping point or threshold around 2006–2007. The shifts were characterized by abrupt changes in the trends of nutrient (phosphate, ammonia, nitrite) concentrations, nutrient ratios (DIN/phosphate, silicate/phosphate), plankton abundance, and total plankton biomass. Compared to the nutrient regime, the planktonic ecosystem functioning shifted several years later. Overall, this study indicates that the pelagic ecosystem regime can shift significantly in response to long-term increasing input of human-induced nutrients in coastal waters such as the Daya Bay. The regime shifts may have profound implications for fishery production, and ecosystem management in the bay.

Enhanced electrochemical detection of nitrite and nitrate in water using Chitosan-Copper phthalocyanine nanocomposite

In this investigation, we study the behavior of a hybrid nanomaterial system combining chitosan-based tetrasulfonated copper phthalocyanine catalyst (Chit/Ts-CuPc) modified carbon screen-printed electrodes (CSPE) for the determination of nitrite and nitrate. Under optimal experimental conditions defined by cyclic voltammetry (CV) and square wave voltammetry (SWV) surveys, the functionalized CSPE exhibited significant catalytic activity towards nitrite and nitrate with a considerable enhancement of the cathodic-anodic peak currents. The Chit/Ts-CuPc nanocomposite enabled the sensors to have a broad linear detection range, which allows quantifying analytes at various concentrations, from 40 to 100 µM for nitrite and 1 to 10 µM for nitrate. Low detection limits (3Sb/m) have been achieved, which are 0.06 µM and 0.05 µM for nitrite and nitrate ions, respectively. Moreover, the proposed modified electrode showed its applicability by measuring the concentration of nitrite and nitrate ions with interfering species and in real water samples.

Alterations in Soil Bacterial Community and Its Assembly Process within Paddy Field Induced by Integrated Rice–Giant River Prawn (Macrobrachium rosenbergii) Farming

Integrated rice–aquatic animal farming has become a vital strategy for enhancing food security. To assess the effects of integrated rice–giant river prawn (Macrobrachium rosenbergii) farming (IRPF) on agricultural ecosystems, we used 16S rRNA gene sequencing to analyze soil bacterial communities in comparison with traditional rice monoculture (RM). Our study revealed that the IRPF did not significantly affect the diversity of the soil bacterial community. However, during the initial culture stage, IRPF markedly increased the relative abundance of the phylum candidate division NC10 and the genus Candidatus Methylomirabilis, enhancing nitrogen-cycling-related functions within the bacterial community. Additionally, IRPF reduced the complexity and stability of these communities in the early to middle culture stages. While stochastic processes usually dominate the assembly of these communities, IRPF restricted bacterial migration and reduced the influence of these stochastic processes. Furthermore, IRPF had a significant impact on environmental factors within paddy soils, strongly correlating with shifts in bacterial communities, particularly through variations in soil nitrite concentration. In conclusion, the influence of IRPF on the bacterial community in paddy soils was primarily observed during the early and middle culture stages, and the impacts of IRPF on the soil bacterial community were primarily driven by environmental changes, especially soil nitrite concentration. These findings provide theoretical insights and a reference for understanding the microbiological impacts of different integrated rice–fish farming systems on agricultural ecosystems.

Effects of pellet inorganic nitrogen on nitrous oxide emissions from cattle manure compost pellets

ABSTRACT Manure compost pellets (MCPs) emit more nitrous oxide (N2O) when applied to soils than loose manure compost or inorganic fertilizer, but pellets of N-enriched manure compost (N+MCP), a by-product of deodorizing manure during composting, emit less N2O than MCPs. To investigate why N+MCPs emit less N2O than MCPs, I studied the effect of inorganic N content, which differs clearly between MCP (2 mg NO3 − g−1, 0.2 mg NH4 + g−1) and N+MCP (17 mg NO3 − g−1, 4 mg NH4 + g−1). MCPs made from cattle manure composts were incubated with various concentrations of nitrate-N (2, 3.5, 5, 10, 20 mg g−1) as KNO3 and ammonium-N (0, 2, 4 mg g−1) as (NH4)2SO4. N2O emissions and related chemical properties were measured during incubation for 14 days. N2O emission peaked at 1 day, and the peak height was significantly lower when nitrate (MCP-NO3_20) and nitrate plus ammonium (MCP-NO3+NH4) contents were raised to the same levels as in N+MCP than in MCP (no added N). Nitrite contents in pellets at 1 day were also lower in both treatments than in MCP. Total N2O emissions during incubation were significantly lower from MCP-NO3+NH4 than from MCP. Emission factors of MCP-NO3_20 and MCP-NO3+NH4 were significantly lower than that of MCP. Pellet nitrate content was negatively correlated with total N2O emission during incubation (p < 0.05). These results suggest that the inorganic N content is important in suppressing N2O emissions from N+MCP.

The combination of non-electrolytic hypochlorite water and ultrasonic treatment on the cleaning and preservation of baby cabbage

In the present study, the synergistic effect of non-electrolytic hypochlorite water (NEHW, 50 mg/L, pH, 5.8) immersion combined with ultrasonic treatment (US, 32 kHz) on the inactivation of bacteria and the maintenance of quality in baby cabbage (Brassica pekinensis) was evaluated. Baby cabbage was treated with tap water immersion, tap water immersion combined with ultrasonic treatment, NEHW immersion combined with ultrasonic treatment and nontreatment (as the control group), and be stored at 4 °C. The results showed that NEHW immersion combined with ultrasonic treatment improved the sensory freshness of baby cabbage, slowed down the rise of weight loss rate and relative conductivity, reduced the number of natural bacteria, yeast and mold, inhibited the rise of nitrate and nitrite content and inhibited the loss of Vitamin C (VC), total phenol and soluble sugar. It is suggested that the shelf life of baby cabbage can be effectively extended with the treatment of NEHW immersion combined with ultrasonic.

Exogenous inoculation with heavy metal-immobilizing bacteria roused the key rhizosphere bacterial community and metabolites of wheat to inhibit cadmium absorption

Rhizosphere functional microorganisms play an important role in the bioremediation of heavy metal-polluted farmlands, however, further research is needed to investigate the effects of exogenous inoculation of functional strains on key bacterial communities and metabolites in cadmium (Cd)-polluted wheat farmlands. This study investigated the effects of the urease-producing bacterium Enterobacter bugandensis TJ6 combined with polyamine-producing bacterium Serratia marcescens X43 on Cd uptake by wheat and its microbiological and soi biolological mechanisms. The results showed that strains TJ6+X43 reduced (95.1 %) the Cd content by secreting urease and polyamines and inducing the precipitation of Cd to form CdCO3 and Cd(OH)2. The combined strains increased (22.7 %) the dry weight and reduced (37.2 %) the Cd content in wheat grains. Moreover, the DTPA-Cd content, the NH4+/NO3- ratio and the urease activity were increased in the presence of strains TJ6+X43. The combined strains reduced the diversity of bacterial communities, but increased the relative abundances of key strains such as Gemmatimonas, Ramlibacter, Sporacetigenium, Pseudomonas, Microvirga, and Nitrospira in the wheat rhizosphere soil. In addition, the contents of glutamate, glutathione, L-ribulose, arginine, nitrite, spermine, isocitrate, and D-xylulose were also increased. More importantly, glutamate metabolism was roused to induce rhizosphere metabolites and functional bacterial communities to synergistically inactivate Cd. The results showed that inoculation with heavy metal-immobilizing bacteria can result in the activation of key functional bacteria and the regulation of metabolite production in wheat rhizosphere soil to immobilize heavy metals, which has broad potential in the bioremediation of wheat fields and ensuring food security.

Ultrasound-induced structural changes in partial nitrification sludge: Unravelling the mechanism for improved nitrogen removal

Low-intensity ultrasound, as a form of biological enhancement technology, holds significant importance in the field of biological nitrogen removal. This study utilized low-intensity ultrasound (200 W, 6 min) to enhance partial nitrification and investigated its impact on sludge structure, as well as the internal relationship between structure and properties. The results demonstrated that ultrasound induced a higher concentration of nitrite in the effluent (40.16 > 24.48 mg/L), accompanied by a 67.76% increase in the activity of ammonia monooxygenase (AMO) and a 41.12% increase in the activity of hydroxylamine oxidoreductase (HAO), benefiting the partial nitrification. Based on the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theoretical analysis, ultrasonic treatment enhanced the electrostatic interaction energy (WR) between sludge flocs, raising the total interaction energy from 46.26 kT to 185.54 kT, thereby causing sludge dispersion. This structural alteration was primarily attributed to the fact that the tightly bonded extracellular polymer (TB-EPS) after ultrasound was found to increase hydrophilicity and negative charge, weakening the adsorption between sludge cells. In summary, this study elucidated that the change in sludge structure caused by ultrasonic treatment has the potential to enhance the nitrogen removal performance by partial nitrification.

Bottom water quality plasticity in the northern gulf of Mexico hypoxic zone

The growth of the now ubiquitous hypoxic zones found throughout the global coastal ocean are primarily a consequence of nutrient enrichment in surface waters increasing organic production that sinks into bottom waters where oxygen is depleted faster than it is replenished. Hypoxic zones may increase or decline in number because of future climate changes. Here we summarize the summertime variations of dissolved inorganic silicate (DSi), phosphate (DIP), nitrogen (DIN; nitrate + nitrite and ammonium) and ammonium concentrations in the bottom waters of the northern Gulf of Mexico continental shelf from 1985 to 2022. The concentrations of all three are strongly correlated to oxygen concentrations, but not in the same way. At zero oxygen concentration, the annual concentrations of DSi, DIP, and ammonium changed over 38 years at a rate of 1.6 % y−1, 2.0 % y−1 and -1.7 % y−1, respectively. However, the nitrate + nitrite concentrations at zero oxygen concentrations did not change over the same interval. The silicate efflux from anoxic sediments is directly related to warming temperatures and is co-related to phosphate concentrations. The bottom water DSi:DIN molar ratios increased over three decades as DIN:DIP molar ratios decreased, suggesting strong nitrogen limitation compared to silicate and phosphate, and reveal significant plasticity in regeneration rates in the bottom waters that may be dependent on changes in the surface waters. Hypoxia and food web models based on a stationary equipoise of these amounts and ratios in surface and bottom waters will likely be deficient as coastal waters warm, acidification increases, and river water quality changes. Data refreshment and improved understanding of food web changes and warming futures are recommended.

Effect of plasma-activated water on planktonic and biofilm cells of Vibrio parahaemolyticus strains isolated from cutting board surfaces in retail seafood markets.

This research aimed to analyze cutting board surfaces in seafood markets to find Vibrio parahaemolyticus, assess the isolates' ability to form biofilms, generate and evaluate characteristics of plasma-activated water (PAW), and compare the effect of PAW on planktonic and biofilm cells of the isolated V. parahaemolyticus strains. A total of 11V. parahaemolyticus strains were isolated from 8.87% of the examined cutting boards. Biofilm-forming ability was evaluated for these isolates at temperatures of 10°C, 20°C, and 30°C using crystal violet staining. Four strains with the highest biofilm potential were selected for further analysis. The pH of the PAW used in the study was 3.41±0.04, and the initial concentrations of hydrogen peroxide, nitrate, and nitrite were 108±9.6, 742±61, and 36.3±2.9µM, respectively. However, these concentrations decreased significantly within 3-4 days during storage at room temperature. PAW exhibited significant antimicrobial effects on V. parahaemolyticus planktonic cells, reducing viable bacteria up to 4.54 log CFU/ml within 20 min. PAW also reduced the number of biofilm cells on stainless steel (up to 3.55 log CFU/cm2) and high-density polyethylene (up to 3.06 log CFU/cm2) surfaces, although to a lesser extent than planktonic cells. PAW exhibited significant antibacterial activity against V. parahaemolyticus cells, although its antibacterial properties diminished over time. Furthermore, the antibacterial activity of PAW against biofilm cells of V. parahaemolyticus was less pronounced compared to the planktonic cells. Therefore, the actual effectiveness of PAW in seafood processing environments can be affected by biofilms that may form on various surfaces such as cutting boards if they are not cleaned properly.

Possible causes of high nitrite levels in some processed leafy vegetables

Nitrate is a compound that accumulates in the leaves of some leafy vegetables such as spinach, lettuce and rocket, and the European Regulation No. 2023/915 establishes maximum limits, due to some health effects. Nitrite should be absent or present only in traces in leafy vegetables. However, some recent studies demonstrated that not negligible concentrations of nitrite (higher than 50 mg kg−1) may be quantified in leafy vegetables such as spinach and lettuce. In this work, several possible sources of nitrite formation in leafy vegetables, agronomic, environmental, microbiological, and processing have been investigated to evaluate the main factors which led to this accumulation. Microbiological contamination, particularly Enterobacteriaceae, of “fresh-cut” samples of spinach, Swiss chard and wild rocket, has been ascertained as the main source of nitrite accumulation, regardless of other considered factors (agronomic, environmental, processing, etc.). The correlation between Enterobacteriaceae count and nitrite concentration was assessed at 0.98, confirming this one as the main source of nitrite increase, also at very high levels, in processed leafy vegetables.

Study of Eco-Enzyme Application in Reducing Nitrite Concentration and Ph Value in Water Sample

The number of high fruit loss must be resolved immediately. East Java produces the highest number of banana and orange. To prevent the fruit loss, as mitigation, the fruit loss can be used to make eco-enzymes as biodegradable agents which was made from nature to treat contaminated water from nitrite contamination and high pH value. Contaminations such as nitrite in water pose significant risks, particularly to organisms. Nitrite contamination can adversely affect humans by reacting with hemoglobin, leading to the formation of methemoglobin, which hampers the blood's ability to bind with oxygen and transport it to body tissues. Eco-enzymes serve as biocatalysts to accelerate the nitrification process, converting ammonia into nitrate with nitrite as an intermediate product. This study was conducted on a laboratory scale, using water samples comprised of distilled water and nitrite standard solution. Two types of eco-enzymes, derived from banana and orange waste, were applied at a 5% concentration to reduce nitrite levels and pH values in the water samples. The results indicated that the orange eco-enzyme reduced nitrite concentrations by 73.2% and pH values by 38.42%, while the banana eco-enzyme achieved a reduction of 93.89% in nitrite concentrations and 23.15% in pH values. As an application of this study, the 5% eco-enzyme solution holds promise for use in biological treatment within wastewater treatment plants, particularly in aeration tanks, to enhance the nitrification process, thereby aiding in the reduction of nitrite concentrations and pH values in wastewater.

Environmental factors influencing the abundance and spatial distribution of modern dinoflagellate cysts in Izmir Bay (Eastern Mediterranean)

We analyzed surface sediments from 12 stations located in Izmir Bay to determine the impact of anthropogenic pollution on dinoflagellate cysts. Forty-three dinoflagellate cyst taxa and two cyst assemblage zones were identified. Zone 1 is characterized by the dominance of cysts of Gymnodinium nolleri, Selenopemphix nephroides, and Operculodinium centrocarpum from the oligotrophic part of Izmir Bay. Zone 2 is in the highly productive inner part of the bay and is characterized by the high abundances of Lingulodinium machaerophorum, Spiniferites ramosus, cysts of Scrippsiella spp., cysts of Polykrikos spp. and Quinquecuspis concreta. We used multivariate statistical analysis (DCA and CCA) on dinoflagellate cysts and environmental variables to support the identification of Zones 1 and 2. Our analyses also revealed that summer and winter chlorophyll-a as well as elevated nitrate and nitrite concentrations are significant parameters in controlling dinoflagellate cyst distribution in Izmir Bay.

Development of an accurate hand-held sensing platform for nitrite detection based on nitrogen-doped carbon dots

As is well known, excessive nitrite can seriously pollute the environment and can harm human health. Although existing methods can be used to determine nitrite content, they still have some drawbacks, such as relatively complicated operation and expensive equipment. Herein, a hand-held sensing platform (HSP) for NO2− determination was developed. First, ammonia-rich nitrogen-doped carbon dots with orange-yellow emission were designed and synthesised, which were suitable as fluorescent probes because of their good optical properties and stability. Then, the HSP based on fluorescence using photoelectric conversion technology was designed and manufactured using three-dimensional printing technology. Under optimum conditions, the voltage (V/V0) of the proposed HSP showed good linearity for NO2− detection in the range of 10–500 μM, with a detection limit of 1.95 μM. This portable sensor showed good stability, accuracy and reliability in detecting actual water and meat samples, which may ensure food safety in practical applications. Moreover, the HSP is compact, portable and easily assembled and is suitable for on-site real-time detection, which shows great application potential and prospects.