Nitrate Concentrations Research Articles

Health Risk Assessment of Nitrate, Nitrite, and Fluoride Ions in Water Reservoirs of Mehriz, Iran in 2023

Introduction: High concentrations of nitrate, nitrite, and fluoride in drinking water can cause adverse health effects. This study aims to investigate concentration and health risks assessment of nitrate, nitrite, and fluoride ions in water reservoirs of Mehriz city and Bahadoran district. Materials and Methods: Monthly sampling was done from water reservoirs of Mehriz city and Bahadoran district for 6 months. Nitrate, nitrite, and fluoride concentrations were measured in the samples using a spectrophotometer. Then, health risk assessment and sensitivity analysis were performed on the obtained data using Crystal Ball software and Monte Carlo simulation method. Results: Nitrate, nitrite, and fluoride concentrations were lower than the standard limitation in all of the studied areas. Risk assessment findings indicated that hazard quotient (HQ) values of nitrite in Miankoh-Movahedin, Bidok and Bahadoran water reservoirs were less than 1 for all age groups. HQ values of nitrate were also below 1 for all age groups except children. HQ values of fluoride in Bahadoran water reservoir were below 1 for all age groups except children. Conclusion: Health risk of consuming water containing nitrates and fluorides is high for children. Based on sensitivity analysis, the concentration of nitrate and fluoride in drinking water is the key factor in raising health risks. Reducing nitrate and fluoride concentrations in drinking water can reduce health risks in the population.

Interactions between Sudangrass Lines Selected for Differing Nitrate Expression and Sorghum Aphid

Sudangrass (Sorghum sudanense Stapf) is widely cultivated as a summer annual forage across the southern Great Plains because of its robust forage yield potential. However, the accumulation of nitrates and the potential harm to livestock have restricted the use of Sudangrass for feeding ruminants. Since 2013, the sorghum aphid (SA), Melanaphis sorghi (Theobald) (Hemiptera: Aphididae), has been damaging sorghum and Sudangrass production. However, the interaction between SA feeding and nitrate accumulation in Sudangrass has not been determined. In this study, we evaluated the effect of SA feeding on different Sudangrass lines, comparing them to a susceptible and a resistant sorghum variety and measuring the physiological responses and nitrate concentration after aphid feeding. Additionally, we evaluated the use of these grass lines on SA demographics. Initial infestations of 100 SA per plant that were allowed to feed and proliferate for 20 days increased nitrate concentrations in Sudangrass by more than 60% compared to controls. Concurrently, the Sudangrass lines selected for high nitrate levels drastically reduced SA demographic parameters, comparable to those of the resistant sorghum control. Although the adoption of resistant cultivars is recommended for aphid management, the Sudangrass lines selected may not be the best option for SA management because their accumulation of nitrates in response to herbivory can cause ruminant poisoning.

Application of flow airlift fluidized bed (CAFB) - Aerobic denitrification bioreactor using polycaprolactone (PADR) as organic carbon source and biofilm carrier for synthetic marine aquaculture wastewater treatment

Aerobic denitrification, a novel method for complete nitrate removal process, relies on a constant carbon supply, and carbon availability can be a limiting factor for the process. Three biodegradable polymers - polybutylene succinate (PBS), polycaprolactone (PCL), and polylactic acid (PLA) were used as carbon source of aerobic denitrifying bacteria, Halomonas venusta for treating recirculating aquaculture wastewater in batch tests, respectively. The group utilizing PCL displayed the greatest efficiency in nitrate removal. Afterwards, a continuous flow airlift fluidized bed (CAFB) - aerobic denitrification bioreactor using PCL(PADR) as bio-carriers and carbon source was started up. The effect of shifting temperature on the nitrate removal and microbial community of CAFB-PADR was investigated under different hydraulic retention times (HRT). The results showed that no significant difference was detected in denitrification activity at 25 and 30 °C condition, where the denitrification rate was 1.1–1.8 times higher than that at 15 °C. However, the nitrogen removal efficiency was above 50 % and there was barely accumulation of nitrite at 15 °C, indicating the good nitrate removal performance in CAFB-PADR at all three temperature conditions. Microbial composition analyses revealed that as the temperature decreased, the relative abundance of Gammaproteobacteria increased, while those of Alphaproteobacteria and Bacteroidia diminished decreased. The existence of denitrifying function genera (Marinobacter, Pseudomonas, Halomonas and Hydrogenophaga) ensured the rapid removal of nitrogen in the biofilter. When the temperature dropped to 15 °C, Pseudomonas progressively took the position of Marinobacter, both of which had denitrification and degradation activities. The relative abundance of the denitrifying bacteria Halomonas that we inoculated has been less than 1 % since phase II. Overall, the PCL-supported CAFB-PADR demonstrated in this study shows potential for removing high concentrations of nitrate from recirculating marine aquaculture wastewater.

Low N2O emissions induced by root-derived residues compared to aboveground residues of red clover or grass mixed into soil

The default The Intergovernmental Panel on Climate Change (IPCC) guidelines assume a constant N2O emission factor (EFN2O) for both belowground crop residues (BGR) and aboveground residues (AGR), and that ∼70 % of total N2O emissions following renewal of temporary grasslands come from BGR. However, empirical evidence is lacking, which motivated this study. BGR-free and BGR-rich clay loam collected in grass or red clover leys were incubated alone or mixed with AGR and different doses of nitrate over 107 days. The average EFN2O of BGR was around 18 % of that of AGR, and remained low even when soil nitrate concentration was very high, whereas EFN2O of AGR varied largely and rocketed even with a small increase in soil nitrate. The decomposition of the carbon present in crop residues was critical for N2O emissions. Lower EFN2O of BGR relative to AGR were related to slower C decomposition, which was not predicted by the biochemical characteristics. It is also likely that BGR were less conducive than AGR to develop into hotspots for N2O emission because of the roots’ finer distribution and closer contact with soil particles. Differences in EFN2O among AGR were mostly linked to the availability of N, either derived from residue mineralization or present in the soil. In conclusion, N2O accountings based on present IPCC default methodology likely overestimate the contribution by crops’ BGR.

Joint cultivation of fish and vegetable crops in an aquaponics system using floating beds

Comparative results of the cultivation of Silver crucian carp in conditions of aquarium circulation systems are presented, in one of which aquaponic cultivation of tomatoes and peppers on a floating bed in a fish tank was used. In comparison with the control, a significant improvement in hydrochemical parameters for dissolved oxygen and a group of nitrogen-containing compounds was noted in the experimental aquarium. The ratio of the specific formation as a result of the vital activity of fish and the absorption of nitrates by plants was 0,8 units. The results showed that for 1 kg of ichthyomass, 26 tomato plants or 34 bell pepper bushes can be planted on a floating bed. In the obtained fruits, the nitrate content turned out to be 2 times lower than the MPC for open and 4 times lower than the MPC for protected soil. The increase in the total ichthyomass of crucians in the experiment turned out to be 1,6 times higher, and feed costs 1,5 times lower than in the control. At the same time, the fish productivity of the aquarium with a floating vegetable garden increased by 9,7%.

75-Year dynamics of the Black Sea phytoplankton in association with eutrophication and climate change

Based on a database containing species records obtained from 1948 to 2022 and a hydrochemical database, long-term changes in the biomass and taxonomic structure of phytoplankton in the deep-sea basin of the Black Sea were analysed in the stratified period from April to October. Over 75 years, a significant increase in concentration of nitrate, a weak increase in phosphate and a strong decrease in dissolved silicate were observed in the nutricline. The biomass of diatoms and total phytoplankton increased several times during the peak of eutrophication in 1991–1993, then decreased by the 2000s and has again shown an increasing trend in the last 15 years. The number of species dominant in biomass has halved from the 1940s–60s to the 2010s. The primary beneficiaries were the large- and medium-celled diatoms Pseudosolenia сalcar-avis and Proboscia alata, as well as the coccolithophore Emiliania huxleyi, the main dominant species of the last decade. Most noticeable was the increase in the amplitude and duration of the regular annual May–July bloom of E. huxleyi. Over the past three decades, its biomass has increased by more than an order of magnitude, accounting for about 40 % of the total phytoplankton biomass. Development of the large- and medium-celled diatoms, as well as the decrease in biomass of silicoflagellates, can be, at least partly, associated with the long-term decline in dissolved silicate in the upper layers. The trend towards a decrease in dinoflagellate biomass is probably associated with increased mixing intensity in the water column. Over the study period, the total phytoplankton biomass was positively related to nitrate stock in the water column. Short-term period (from one to several years) interannual variability was influenced predominantly by hydrophysical processes, primarily the intensity of winter convection. After cold winters with intense involvement of deep nutrients in the upper layers, the biomass of diatoms, coccolithophores and total phytoplankton increased. Thus, fluctuations in winter weather or local climate reduced or enhanced the effect of eutrophication, sometimes leading to the time gap between the peak in nitrate stock and phytoplankton biomass. The case of the Black Sea illustrates the complex pattern of the response of a marine ecosystem to the simultaneous impacts of anthropogenic and climate changes, leading to significant alterations in the functioning of the biological carbon pump.

Vertical variation of antibiotic resistance genes and their interaction with environmental nutrients in sediments of Taihu lake

Antibiotic resistance is a growing environmental issue. As a sink for antibiotic resistance genes (ARGs), lake surface sediments are well known for the spread of ARGs. However, the distribution pattern of ARGs and their relationship with environmental factors in vertical sediment layers are unclear. In this study, we investigated the resistome distribution in sediment cores from Taihu Lake using metagenomic analysis. The results showed that the abundance of total ARGs increased by 153% as the sediment depth rose from 0 to 50 cm, and the ARG Shannon index significantly increased. Among all the ARG types, efflux pump genes (e.g., mexT and mexW) were dominant, especially in 40–50 cm sediment. The variation in ARG with depth described above was related to the changes in bacterial adaptation to environmental gradients. Specifically, sulfate and nitrate concentrations decreased with depth, and random forest analysis showed that they were the main factors affecting the changes in ARG abundance. Environmental factors were also found to indirectly impact the distribution of ARGs by affecting the bacterial community. Potential sulfate-reducing gene/nitrate-reducing gene-ARG co-hosts were annotated through metagenomic assembly. The dominant co-hosts, Curvibacter, and Comamonas, which were enriched in deeper sediments, may have contributed to the enrichment of ARGs in deep sediments. Overall, our findings demonstrated that bacterial-mediated sulfate and nitrate reduction was closely related to sediment resistance, which provided new insights into the control of antibiotic resistance.

Enhanced Pollutant Removal and Antifouling in an Aerobic Ceramic Membrane Bioreactor with Bentonite for Pharmaceutical Wastewater Treatment.

This study examined the impact of adding bentonite clay (concentration of 1.5 to 10 g/L) to a pilot-scale aerobic ceramic membrane bioreactor (AeCMBR) for treating pharmaceutical wastewater (PhWW). The hydraulic retention time (HRT) was maintained at 24 h; the dissolved oxygen was between 2 mg/L (on) and 4 mg/L (off) throughout operation. Organic and nitrogen pollution removal rates and heavy metal (Cu, Ni, Pb, Zn) reduction rates were assessed. The chemical oxygen demand (COD) removal efficiency exceeded 82%. Adsorption improved ammonia (NH4+) removal to 78%; the addition of 5 g of bentonite resulted in a 38% improvement compared with the process without bentonite. The average nitrate concentration decreased from 169.69 mg/L to 43.72 mg/L. The average removal efficiencies for Cu, Ni, Pb and Zn were 86%, 68.52%, 46.90% and 56.76%, respectively. Bentonite at 5 g/L significantly reduced membrane fouling. The cost-benefit analysis enabled us to predict that the process will meet the multiple objectives of durability, treatment performance and economic viability. The combination of an AeCMBR and bentonite adsorption has proven to be a valuable solution for treating highly polluted wastewater.

Investigation of Olive Leaf Polyphenol Extract Loaded Silver Nanoparticle Optimization by Box-Behnken Design.

Silver nanoparticles (AgNPs) are synthesized and optimized by reducing and stabilizing them with olive leaf extract. The successful synthesis of AgNPs was verified by UV-vis spectroscopy, SEM imaging, and DLS measurements, demonstrating characteristic features such as a surface plasmon resonance peak, spherical morphology, crystalline structure, and narrow size distribution with good stability. Utilizing Box-Behnken Design (BBD), the optimal synthesis conditions were determined, with a silver nitrate concentration of 1 mM, olive leaf extract volume of 10 mL, and reaction time of 60 minutes, yielding AgNPs with desirable properties. Statistical analysis revealed the significant influence of individual variables and their interactions on AgNP characteristics. Lower concentrations of silver nitrate and olive leaf extract led to smaller particle sizes and higher zeta potentials, while longer reaction times resulted in larger particles and lower zeta potentials. Among the experimental runs, Run 11 exhibited the most favorable properties, with 54 nm particle size, -36 mV zeta potential, and an encapsulation efficiency of 92.28%. ANOVA analysis further elucidated the significant effects of synthesis parameters on zeta potential, particle size, and encapsulation efficiency. In conclusion, the optimized formulation obtained through BBD offers a tailored approach for the synthesis of AgNPs with desired properties, suitable for various applications such as biomedical, catalytic, and sensing applications. The comprehensive understanding of synthesis parameters and their effects provided by this study facilitates the rational design of AgNPs for specific applications, enhancing their potential in diverse fields.

Assessing the effectiveness of SO2, NOx, and NH3 emission reductions in mitigating winter PM2.5 in Taiwan using CMAQ

Abstract. Taiwan experiences higher air pollution in winter when fine particulate matter (PM2.5) levels frequently surpass national standards. This study employs the Community Multiscale Air Quality model to assess the effectiveness of reducing SO2, NOx, and NH3 emissions on PM2.5 secondary inorganic species (i.e., SO42-, NO3-, and NH4+). For sulfate, ∼ 43.7 % is derived from the chemical reactions of local SO2 emission, emphasizing the substantial contribution of regionally transported sulfate. In contrast, nitrate and ammonium are predominantly influenced by local NOx and NH3 emissions. Reducing SO2 emissions decreases sulfate levels, which in turn leads to more NH3 remaining in the gas phase, resulting in lower ammonium concentrations. Similarly, reducing NOx emissions lowers HNO3 formation, impacting nitrate and ammonium concentrations by decreasing the available HNO3 and leaving more NH3 in the gas phase. A significant finding is that reducing NH3 emissions decreases not only ammonium and nitrate but also sulfate by altering cloud droplet pH and SO2 oxidation processes. While the impact of SO2 reduction on PM2.5 is less than that of NOx and NH3, it emphasizes the complexity of regional sensitivities. Most of western Taiwan is NOx-sensitive, so reducing NOx emissions has a more substantial impact on lowering PM2.5 levels. However, given the higher mass emissions of NOx than NH3 in Taiwan, NH3 has a more significant consequence in mitigating PM2.5 per unit mass emission reduction (i.e., 2.43 × 10−5 and 0.85 × 10−5 µg m−3 (t yr−1)−1​​​​​​​ for NH3 and NOx, respectively, under current emission reduction). The cost-effectiveness analysis suggests that NH3 reduction outperforms SO2 and NOx reduction (i.e., USD 0.06 billion yr−1 µg−1 m3, USD 0.1 billion yr−1 µg−1 m3, and USD 1 billion yr−1 µg−1 m3 for NH3, SO2, and NOx, respectively, under the current emission reduction). Nevertheless, the costs of emission reduction vary due to differences in methodology and regional emission sources. Overall, this study considers both the efficiency and costs, highlighting NH3 emissions reduction as a promising strategy for PM2.5 mitigation in the studied environment in Taiwan.

Effect of copper on nitrogen uptake, transportation, assimilation processes, and related gene expression in Chinese cabbage [Brassica campestris L. ssp. Chinensis (L.)] under various nitrate-to-ammonium ratios.

Improving vegetable yield and optimizing its quality through nutrient management have long been central to plant nutrition and horticultural science. Copper (Cu) is recognized as an essential trace element that promotes plant growth and development. However, the mechanisms by which Cu influences nitrogen (N) metabolism remain largely unknown, with limited studies exploring the interaction between Cu and varying nitrate-to-ammonium (nitrate/ammonium) ratios. In this study, Chinese cabbage was exposed to two Cu concentrations (0 and 0.02 mg L-1) in combination with three nitrate/ammonium ratios (10/90, 50/50, and 90/10) under hydroponic conditions. The results showed that Cu application increased plant biomass, nitrate reductase (NR) and glutamine synthetase (GS) enzyme activities, the expression of NR (NIA) and GS2 (Gln2) genes, and N content in both shoots and roots. Additionally, Cu treatment decreased nitrate and free amino acid contents, as well as the expression of nitrate transporters NRT1.1 and NRT2.1 in roots while increasing these four parameters in shoots. Additionally, these effects were significantly modulated by the nitrate/ammonium ratios. In conclusion, Cu may facilitate nitrate transportation, enhance nitrate reduction, promote ammonium assimilation, and influence the transformation of organic N compounds, highlighting its potential role in improving N metabolism in Chinese cabbage.

Numerical Groundwater Model to Assess the Fate of Nitrates in the Coastal Aquifer of Arborea (Sardinia, Italy)

The Arborea plain in Sardinia (Italy) is classified as a nitrate vulnerable zone (NVZ). In the present study, the individual work steps that are necessary to progress from the existing 3D hydrogeological model to a 3D numerical groundwater model using the interactive finite-element simulation system FEFLOW 7.4 are shown. The results of the transient flow model highlight the influence of the drainage network on the overall groundwater management: the total water volume drained by the ditches accounted for approximately 58% of the annual outflow volume. The numerical transport simulations conducted from 2012 to 2020 using hypothetical field-based nitrate input scenarios globally underestimated the high concentrations that were observed in the NVZ. However, as observed in the field, the computed nitrate concentrations in December 2020 still varied strongly in space, from several mg L−1 to several hundreds of mg L−1. The origin of these remaining local hotspots is not yet known. The modeling of rainfall fluctuations under the influence of climate change revealed a general long-term decline in the groundwater level of several tens of centimeters in the long term and, in conjunction with a zero-nitrate scenario, led to a significant decrease in nitrate pollution. Although hotspots were attenuated, the concentrations at several monitoring wells still exceeded the limit value of 50 mg L−1.

QBD approach for green synthesis of Rutin silver nanoparticles- screening for antioxidant, anticancer and anticlastogenic potential

Rutin is a flavonoid glycoside abundant in many plants exhibiting pharmacological activities like antioxidant, anticancer, anti-inflammatory and antimicrobial activities. Plant biomarkers suffer low bioavailability and solubility that lack clinical effectiveness. The smart nanoparticles conversion addresses this limitation with optimal particle size and targeted drug delivery. The present study involves QbD approach for formulation of Rutin silver nanoparticles and evaluation of antioxidant, anticancer and anticlastogenic potential. QbD experimentation involved particle size and drug release as dependent variables over the silver nitrate concentration, methanol and sonication time as independent variables devising 15 formulations (F1 –F15). F12 formulation was found to be optimized with 126.3 nm average size, stable and dispersible characterized by UV, FTIR, SEM and DLS studies. The calibration curve of Rutin was plotted at 352 nm with linearity (LOD = 0.061 μg/ml and LOQ = 0.187 μg/ml). The invitro drug release studies by USP dissolution apparatus I (Basket type) proved the sustained release characteristics with 97.3 % drug release when compared to the Rutin. The pharmacological screening for potential antioxidant and anticancer activity on G361 and MCF 7 cell line of F12 formulation have shown promising results and also enhanced solubility in water compared to Rutin. Anticalstogenic potential as a function of induced micronuclei frequency was evaluated as a characteristic feature in bone marrow cells obtained from mice. Results indicate pre-treatment with the F12 reduced frequency of micronuclei in mouse bone marrow cells caused by Cyclophosphamide (CP) significantly. The protective effect of F12 in suppression was demonstrated at both dosages of 100 and 200 mg/kg. Thus the findings suggest the novel Rutin silver nanoparticles as lead drug serving as antioxidant, anticancer and anticlastogenic agent.

Electrodialysis reversal (EDR) technology: a viable solution for addressing water quality challenges in the dry zone, Sri Lanka

ABSTRACT Chronic Kidney Disease of Unknown Etiology (CKDu) affects rural Sri Lankan agricultural populations, with poor-quality ground and surface water suspected as the root cause. Hence, we conducted this study to explore the effectiveness of Electrodialysis Reversal (EDR) technology in treating water quality issues related to CKDu in dry zone of Sri Lanka. The EDR plant in Kahatagasdigiliya, Anuradhapura district, managed by the National Water Supply and Drainage Board (NWS&DB) was selected. We measured both physical (colour, turbidity, pH) and chemical (electrical conductivity, total dissolved solids, chloride, alkalinity, hardness, nitrate, nitrite, sulfate, fluoride, total phosphate, iron, manganese) parameters of the EDR process. The parameters of the permeate stage of the EDR plant were validated by comparison with data from SLS 614:2013, and removal efficiencies were assessed. The results revealed that all parameters consistently fell within the permissible limits in the permeate stage of the EDR plant. Turbidity (62.65%), sulfate and manganese (50%), colour (47.37%), fluoride (44.19%), and hardness (35.71%) showed high removal efficiencies in the EDR process. The study demonstrated the effectiveness of EDR technology in addressing water quality challenges, validating its potential for groundwater treatment and this contributes to the improvement of groundwater quality in CKDu-prevalent areas.

Multiannual oceanographic studies in the coastal area of Karadag Nature Reserve and Koktebel Bay (northern Black Sea) in 2004–2021

The study presents the results of the first multiannual oceanographic monitoring in the coastal area of Karadag Nature Reserve and adjacent water areas in May and September in the period from 2004 to 2021. Significant and unprecedentedly high increasing trends were detected for salinity in May. Increasing trends in nitrate concentration in Koktebel Bay were noted both for May and for September. The five-day biochemical oxygen demand (BOD5), ammonium and phosphate concentrations demonstrated mostly negative trends for the measurements in May and positive trends in September. Significant decreasing trends in phytoplankton biomass were noted in September, which fit in the range of the larger-scale phytoplankton trends reported in the literature. The position of the extrema of nutrients in the long-term-average and trend slope maps was confined to the areas of increased hydrodynamic and anthropogenic activity. Multivariate analysis showed significant negative correlations of the quantitative phytoplankton characteristics with salinity, which were explained by the effect of the freshened and nutrient-enriched Azov plume. The absence of significant correlations with nutrients was attributed to the non-conservative and stochastic character of the nutrient inflow on the yearly scale and time lag between the nutrient supply and the phytoplankton growth. The large percentage of occurrences of low BOD5 values at any station indicates the unpolluted status of the area under research, which is confirmed by the low trophic index values and appearance of probability distributions of the nutrient concentrations.

Effects of Aquatic Physicochemical Parameters Variation on the Phytoplankton Abundance and Diversity in the Babon River, (Semarang, Central Java, Indonesia)

The Babon River is an integral component of Semarang City's drainage system, which is heavily impacted by the influx of waste, leading to elevated water temperatures caused by global warming and decreased pH levels due to acid rain. The two main environmental factors that affect phytoplankton growth and productivity are temperature and nutrient availability. Nutrients can change the balance of the natural food webs of aquatic ecosystems. Meanwhile, metals are toxic and can accumulate in biota tissues. This study examined how nutrients, pH, temperature, and heavy metals in water affected the diversity and abundance of phytoplankton. Water samples and phytoplankton were collected from 7 observation stations representing the upstream, middle, and downstream rivers. Observations at each station were made 3 times in the months of April-May, June-July, and August-September. Temperature and pH were measured in situ with the HORIBA Water Checker. Analysis of nitrate, phosphate, and heavy metals was carried out with an AAS. The results showed that the dominant phytoplankton in the Babon Rivers consisted of Bacillariophyceae, Chlorophyceae, and Cyanophyceae. There is no diversity against all independent variables (temperature, pH, nitrate, phosphate, Cd, Total Cr, Pb concentrations) and dependent variables (number of genera, abundance, and diversity index of phytoplankton) due to the sampling station's location. However, sampling time caused diversity in nitrate, phosphate, Cd, Total Cr, and Pb concentrations, the sampling location effect was more dominant than sampling time, so the results showed that all independent variables did not contribute significantly to the dependent variables.

Response of the performance and succession of denitrification consortium under the variation of nutritional conditions: Mechanisms and characteristics

In the process of wastewater treatment, biomass was typically subjected to variation of nutrient condition. This study investigated the effects of different nutrient condition on denitrification performance and bacterial communities. The results showed that under carbon-to-nitrogen ratio (C/N) was 4, denitrifying sludge (DS) exhibited excellent denitrification performance with influent nitrate (NO3--N) concentration in the range of 88.8 ± 9.04–297.5 ± 6.63 mg L−1, maintained total nitrogen removal efficiency (TNRE) of 98.1 ± 1.75 %. While, as influent NO3--N concentration reached 408.9 ± 9.56 mg L−1, the denitrification performance was inhibited, and this inhibition was reversible. Under appropriate substrate level (215.0 ± 13.01 mg L−1), the specific denitrification activity (SDA) elevated to 300 % of its original value. Additionally, under starvation stress, although the relative abundance of some starvation-resistant bacteria (such as Actinobacteriota and Lentimicrobium) increased, the TNRE decreased by 7.3 %. During the recovery phase, despite extracellular polymeric substances (EPS) promoted, the TNRE decreased to 78.3 ± 4.7 %. Starvation stress was less favorable to DS for activity recovery than that of feast condition. These findings contribute to elucidating the mechanisms for DS to respond of different nutrient condition.

Statistical evaluation and quality analysis of water resources around quarry site in Abuja Suburban Nigeria

Water resources occupies vital position regarding the lifespan and general wellbeing humans while significant shortfalls on its reserves hinders almost all sustainable development globally. Most host communities to quarry companies without a water treatment plant are greatly affected by the use of water resources within its area. The present study highlights statistical evaluation and quality analysis of water resources around a quarry site in FCT Nigeria. The research engaged biological assay, physiological and chemical analysis to quantify contamination level of the water resources from obtained data which were also subjected to statistical analysis. The statistical tools employed are Pearson's Correlation, descriptive statistics, Levene's test for homogeneity and one–way analysis. The physiochemical analysis revealed the water resources to have high turbidity value in 58.3 % of sampled population while nitrate concentration and electrical conductivity value were very low. The bioassay revealed presence of coliform bacteria in 100 % of sampled population while thermotolerance count discovered disease-causing-pathogens in 41.7 % of sampled population. Chemical analysis revealed that Pb, Cr, Ni and As were 91.7 %, 83.3 % 100 % and 100 % above recommended permissible limits for sampled population. These results suggests that water resources in this study is unsafe and holds a health-treat with regards to the contaminations inherent in them. Statistical evaluation revealed average positive linear relationship between heavy metal concentration suggesting close relationship of contamination source. Observed strong positive linear relationship between lead and copper, nickel and chromium as well as nickel and arsenic in the scatterplot depicts same source of contamination.

Application of the DRASTIC-LU/LC method combined with machine learning models to assess and predict the vulnerability of the Rmel aquifer (Northwest, Morocco)

The Rmel aquifer, located in the Tangier-Tetouan-Al Hoceima region of northwest Morocco, covers approximately 240 km2 and faces increasing pollution threats due to population growth and economic development. This study assesses aquifer vulnerability to pollution, and compares the performance of various machine learning models integrated with the DRASTIC-LU/LC method. The research used a dataset of 52 water samples analyzed for nitrate concentrations, considering eight factors influencing vulnerability: aquifer depth, net recharge, aquifer lithology, soil texture, topography, vadose zone impact, hydraulic conductivity, and land use. An information gain test was applied to evaluate the importance of these factors. Four machine learning algorithms were used with the DRASTIC-LU/LC method: multilayer perceptron (MLP), the bagging algorithm (BA), K-nearest neighbors (KNN), and extremely randomized trees (ERT). Model performance was assessed via the area under the ROC curve (ROC-AUC) to measure accuracy. The ERT model combined with DRASTIC-LU/LC achieved the highest accuracy (AUC = 0.929), followed by BA (AUC = 0.925), MLP (AUC = 0.852), and KNN (AUC = 0.787). In comparison, the original DRASTIC-LU/LC model had an AUC of 0.530. The results highlight significant vulnerability variation across the Rmel aquifer, with high to very high levels in the southern and northwestern regions, and moderate to low levels in the northeast and central areas. Vulnerability maps were validated by comparing the observed nitrate concentrations in the water samples, confirming model accuracy. Groundwater depth, net recharge, and hydraulic conductivity were identified as the most significant factors influencing vulnerability. This study demonstrates the effectiveness of integrating machine learning models with the DRASTIC-LU/LC method for accurate aquifer vulnerability assessment, offering valuable tools for public policy and groundwater management.

Multipurpose Impacts of Silver Nitrate on Direct Organogenesis of Begonia rex cv. DS-EYWA via Transverse Thin Cell Layering (tTCL) Technique

Begonia rex cv. DS-EYWA is an important plant for indoor and outdoor cultivation, and cv. DS-EYWA is a rare unique cultivar with curly, colorful leaves. Due to their importance, applying plant tissue culture techniques for mass and healthy production in a short period of time without seasonal limitation is of immense economic value. Applying several concentrations of silver nitrate (AgNO3) in combination with varied concentrations of cytokinins including 6-benzylaminopurine (BAP), thidiazuron (TDZ) (0, 0.5, 1, 1.5 mgL−1), and 1-naphthaleneacetic acid (NAA) auxin (0, 0.5, 1 mgL−1) via focusing on transverse thin cell layer (tTCL) petiole explants for high-scale production was used to establish an efficient in vitro propagation protocol. Our results showed that even low concentrations (25 mgL−1) can control internal bacterial infection and increase shoot direct regeneration efficiency. A combination of 1.5 mgL−1 BAP, 0.5 mgL−1 NAA, and 25 mgL−1 AgNO3 was the best treatment to increase the number of direct regenerated shoots, and a lower concentration of BAP (0.5 mgL−1) can be suggested for shoot elongation. Elongated shoots were successfully rooted in MS basal medium and acclimatized in a 1:1 peat moss/perlite sterilized pot mixture.