Nitrate In Water Research Articles

Prenatal exposure to nitrate from drinking water and the risk of preterm birth: A Danish nationwide cohort study.

Background:Evidence is emerging that preterm birth (PTB, birth before 37 completed weeks of gestation), a risk factor for neonatal mortality and future morbidity, may be induced by maternal nitrate () exposure from drinking water. The objective of this study is to assess the association between maternal exposure to nitrate and the risk of PTB in a nationwide study of liveborn singletons.Methods:We estimated maternal nitrate exposure from household tap water for 1,055,584 births in Denmark to Danish-born parents during 1991–2015 by linkage of individual home address(es) with nitrate concentrations from a national monitoring database. Nitrate exposure during pregnancy was modeled using four categories and continuously. Logistic models adjusted for sex, birth year, birth order, urbanicity, and maternal age, smoking, education, income, and employment, with generalized estimating equations were used to account for sibling clusters.Results:A total of 1,009,189 births were included, comprising 51,747 PTB. An increase in the risk of PTB was seen across categories of exposure (P < 0.001) with an odds ratio (OR) in the uppermost category (>25 mg/L nitrate) of 1.05 (95% confidence interval [CI] = 1.00, 1.10). Evidence of an exposure–response relationship was observed in models using continuous nitrate (OR = 1.01 [95% CI = 1.00, 1.03] per 10 mg/L nitrate). In sensitivity analyses, results were robust to the addition of variables for short inter-pregnancy interval (<1 year between births), maternal pre-pregnancy body mass index, paternal socioeconomic status and age, season of birth, and inclusion of post-term births. Results were virtually unchanged when the analysis was restricted to women exposed to less than the current European Union standard of 50 mg/L.Conclusion:We observed an increasing risk of PTB with increases in nitrate in household tap water. These findings add to a growing body of evidence of adverse effects from nitrate in drinking water at levels below current regulatory levels.

Evaluation of surface water quality using correlation matrix in Lower Lake, Bhopal, India

The most affordable supply of drinkable water for rural, semi-urban, and metropolitan communities in India is lake water. The ecosystem and lake water supplies are polluted by the numerous sources. The current study attempts to determine the level of surface water pollution in close proximity to Lower Lake in Bhopal, India. For the purpose of collecting samples around Lower Lake's edge, three sampling locations were chosen for the study. Twelve physico-chemical parameters, including air and water temperatures, pH, transparency, electrical conductivity, free CO2, dissolved oxygen, phosphate, nitrate, chloride, total hardness, and total alkalinity, were examined seasonally for a period of one year (Nov 2020–Oct 2021) in order to evaluate the surface water quality of Lower Lake. Following statistical analysis, it became evident that there were both positive and negative co-relationships between the attributes. It was discovered that the Lower Lake`s surface water is tainted and unfit for direct consumption.

Calcium leaching from cement hydrates exposed to sodium sulfate solutions

Calcium leaching from cement hydrates to pore solution increases the porosity and reduces the bonding strength of cement hydrates, accelerating the degradation of concrete. Calcium leaching can be quantified by solid–liquid equilibrium curves, which have been studied in deionized water or ammonium nitrate. The research of solid–liquid equilibrium curve of calcium under sulfate attack is limited and its mechanism is poorly understood. Reported here provide insights into the dissolution process of calcium from cement hydrates exposed to the sodium sulfate solution. The experimental programme examines the effects of sulfate ion concentration and temperature. An external sulfate attack (ESA) model considering the influence of calcium leaching is established and validated. The results show that, compared to deionized water, sulfate ions impact strongly the leaching process. Qualitatively, the dissolution of calcium in cement hydrates is accelerated by increasing the concentration of sulfate ions and decreasing the environmental temperature. Quantitatively, the presence of sulfate ions modifies the equilibrium curve describing calcium leaching in deionized water. In addition, the prediction results of the ESA model considering the influence of calcium leaching are in good agreement with the experimental results.

Nitrogen dynamics in small watersheds in the Atlantic Forest and Cerrado in Northeastern Brazil

The aim of this study was to determine concentrations of nitrogen (N) in two biomes, Atlantic Forest (AF) and Cerrado (CR), at the interface between terrestrial and aquatic ecosystems. This involved evaluating N in vegetation (litterfall), soil and water in small watersheds in environmental protection areas in northeastern Brazil. Soil chemical and physical analyzes were performed and mineralization and nitrification rates were determined. The forms of organic, inorganic and particulate nitrogen in water were determined by spectrophotometry. Two collections were carried out, one in the dry season (October and November 2019) and another in the rainy season (February and March 2020), in two environmental preservation areas, Estação Veracel Private Natural Heritage Reserve - (Atlantic Forest) and Chapada Diamantina National Park (Cerrado), with five small watersheds sampled in each biome. The N concentration in litterfall was similar in both biomes, with averages of 0.69%. In relation to soil and water, N concentrations were higher in AF compared to CR, with concentrations of 0.95 ± 0.40 and 0.59 ± 0.14 µg.Ng-1 of nitrate in the soils of AF and CR, respectively, and 3.53 ± 2.51 µM of nitrate in water in AF and 0.76 ± 0.78 µM in CR.

Distribution patterns of macrophytes in shallow lakes of the lower Paraná River floodplain: Associations with environmental conditions

Abstract Macrophytes play key functional and structural roles in floodplain shallow lakes (SL), determining the maintenance of ecosystem functions and sustaining several productive activities. We assessed the relationship between macrophyte community structure (composition, species abundance, and plant diversity) and environmental features (SL dynamics, connectivity, morphometry, flood frequency, and water and sediment physical and chemical variables) in the Lower Paraná River floodplain. Our main hypothesis was that SL macrophyte distribution depends on direct and indirect environmental controls operating at multiple scales. The SL dynamics during the April–November 2017 Paraná River pulse were described according to their coverage changes (vegetation, and turbid or clear open water), which were assessed with supervised classifications on Landsat 8‐OLI scenes. Twenty‐five SL of the Lower Paraná River floodplain were selected to represent all the SL dynamics identified. Ten SL were permanently connected and 15 were disconnected from watercourses. Water and sediment physical and chemical characteristics, macrophyte assemblage composition, and plant species abundance were surveyed at each site in the 2018 summer. Also, SL morphometric parameters and flood frequency were estimated from ancillary geographic data. The direct controlling factors of macrophyte assemblages were water ammonium and water nitrate concentrations, turbidity, and flood frequency. No clear effects of environmental conditions on macrophyte diversity were found. The connectivity of SL with watercourses affected their water and sediment physical and chemical features. Also, SL dynamics during the 2017 pulse were related to flood frequency. As connectivity to watercourses affects SL chemical and physical variables, and SL dynamics were associated with flood frequency, connectivity and SL dynamics indirectly influenced macrophyte assemblage composition. This study improved our understanding of macrophyte distribution patterns in the study area, which was related to several environmental variables operating at different scales. Our results highlight the importance of the variability of hydrological connectivity in promoting environmental heterogeneity in river floodplain systems, which is central to their functioning, and the high biodiversity that characterises these environments.

Reductions in soil water nitrate beneath a perennial grain crop compared to an annual crop rotation on sandy soil

Nitrate (NO3--N) leaching into groundwater as a result of high nitrogen (N) fertilizer rates to annual crops presents human health risks and high costs associated with water treatment. Leaching is a particularly serious concern on sandy soils overlying porous bedrock. Intermediate wheatgrass (IWG) [Thinopyrum intermedium (Host.) Barkw. &amp;amp; D.R. Dewey], is a perennial grass that is being bred to produce agronomically and economically viable grain, which is commercially available as Kernza®. Intermediate wheatgrass is a low-input crop has the potential to produce profitable grain and biomass yields while reducing NO3--N leaching on sandy soils compared with common annual row crop rotations in the Upper Midwest. We compared grain yields, biomass yields, soil solution NO3--N concentration, soil extractable NO3--N, soil water content, and root biomass under IWG and a conventionally managed corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation for 3 years on a Verndale sandy loam in Central Minnesota. Mean soil solution NO3--N was 77–96% lower under IWG than the annual crop rotation. Soil water content was greater under annuals compared to IWG early in the growing season, suggesting greater water use by IWG during this time. Interactions between crop treatments and depth were observed for soil water content in Year 3. Root biomass from 0 to 60 cm below the soil surface was five times greater beneath IWG compared to soybean, which may explain differences in soil extractable and solution NO3--N among crops. With irrigation on coarse structured soils, IWG grain yields were 854, 434, and 222 kg ha−1 for Years 1–3 and vegetative biomass averaged 4.65 Mg ha−1 yr−1; comparable to other reports on heavier soils in the region. Annual crop grain yields were consistent with local averages. These results confirm that IWG effectively reduces soil solution NO3--N concentrations even on sandy soils, supporting its potential for broader adoption on land vulnerable to NO3--N leaching.

Understanding the performance of graphdiyne membrane for the separation of nitrate ions from aqueous solution at the atomistic scale

A molecular dynamics simulation study is conducted to investigate the capability of the pristine graphdiyne nanosheet for nitrate ion separation from water. The removal of nitrate ion contaminants from water is of critical importance as it represents an environmental hazard. The graphdiyne is a carbon-based membrane with pore density of 2.4 × 1018 pores/m2 and incircle radius of 2.8 Å. We show that the efficient water flow is accurately controlled through fine regulation of the exerted hydrostatic pressure. The high water permeability of 6.19 L.Day−1cm−2MPa−1 with 100% nitrate ions rejection suggests that the graphdiyne can perform as a suitable membrane for nitrate separation. The potential of mean force analysis of the single water molecule and nitrate ion indicated the free energy barriers for nitrate of about 4 times higher than that of water molecules. The results reveal the weak interaction of the water molecules and the membrane which aid to high water flux.

Charge Distribution Controls On‐Target Separation of Low Nucleophilicity Anions in Layered Double Hydroxides

AbstractHost–guest chemistry principles and mechanisms have been exploited to separate harmful and valuable ionic species. However, separating low nucleophilicity anions using these protocols is difficult due to weak host–guest interactions. Herein, using layered double hydroxides (LDHs), it is demonstrated that guest–guest interactions considerably influence the separation of a low nucleophilicity nitrate. LDHs exhibit considerably low nitrate ion storage capacities due to the co‐precipitation synthesis method. Hence, a topochemical reaction is applied to control the cation arrangement in the LDHs. Structural analyses determine that a hexagonal cation arrangement is facilitated. Isotherm analysis reveals that the obtained LDHs improve the capacity up to 250% of that of typical less‐ordered LDHs. Finally, further isotherm analysis in combination with theoretical calculations, it is revealed that the hexagonal arrangement effectively facilitates a stable guest–guest interactions—hydrogen‐bond between the interlayer nitrate ions and water molecules, which contributes to high ion‐storage.

Citizen Science as a Co-Creative Measure to Water Quality: Chemical Data and Local Participation in a Rural Territory

It is becoming increasingly clear that the threat to the use of natural landscapes and persistent droughts are affecting the water quality of rural communities. The socio-ecological fit emerges as an aid to advance in the search for solutions to environmental problems in rural communities. Consequently, between May 2016 and September 2021, an interdisciplinary study of community-based water quality monitoring (CWQM) was implemented at a coastal catchment in the Ñuble region, Central Chile. The objective of the study was to involve the participation of local communities in initiatives to control the water quality of various parameters [pH, total iron (FeT), alkalinity as CaCO3, hardness (Ca2+ and Mg2+), sodium (Na+) and potassium (K+), water temperature, sulfate (SO42−) chloride (Cl−), and nitrate (NO3-)] in groundwater, share local knowledge, and apply co-creative measures for improving water conservation. In situ chemical data were also analyzed in the laboratory to check data quality. The PHREEQC hydrogeochemical model is used to characterize hydrogeochemical parameters of groundwater and to know about hydrogeochemical processes related to water quality. High levels of NO3− and FeT are recorded in 75% of the groundwater samples, mainly when water scarcity is higher during the summer. According to Chilean standards, nitrate levels exceed the maximum permissible limits for drinking water. A type of mainly Ca (Mg)–HCO3− carbonated water was recorded with Ca2+, Na+, Mg2+, and HCO3− as dominant ions. This study demonstrated the opportunity of a rural community group to help fill spatial data gaps in water quality monitoring and reassess water quality protection, especially considering the decrease in water availability in the region. Therefore, the community together with researchers can respond with an early alert system to water quality to collaborate with the implementation of rural drinking established on a community-based water quality monitoring. Moreover, to prioritize the level of urgency of rural water, minimize water pollution and improve the perception of the water and the resilience of their social–ecological system.

Responses of aboveground litterfall respiration to unexpected snowfall events in Ailao subtropical forests in Southwest China

Soil respiration, the second largest CO2 flux in terrestrial ecosystems, involves the microbial respiration of litter from aboveground sources, belowground litter and root respiration, from rhizodeposition. In the subtropical forests of the Ailao Mountain, a chamber with automated CO2 efflux was set up with two treatments: a control treatment with litterfall to measure the total soil respiration (RT) and a litter removal treatment to measure aboveground litterfall respiration (RL). This study aimed to examine the responses of RL to unexpected heavy snowfall events and soil temperature (ST), soil moisture (SM), rainfall (RF), total litterfall (TL), litter water content (LWC), nitrate nitrogen (NO3−-N), and ammonium nitrogen (NH4+-N). The period of the study was divided into two: before the heavy snowfall event (BS) and during and after the heavy snowfall event (AS). The rate of RL was slightly decreased in AS (1.18 ± 0.03 μmol CO2 m−2 s−1) compared with that in BS (1.19 ± 0.02 μmol CO2 m−2 s−1). The relationships between RL and ST, SM, RF, and LWC, respectively, were all statistically significant (p < 0.05) in both periods. However, the relationships between RL and TL and NH4+-N, respectively, were not statistically significant for either period. The relationship between RL and NO3−-N was statistically significant for AS but not for BS. The relationship between RL and RF was statistically significant from 2011 to 2018. The temperature dependence of soil respiration was higher in BS than in AS, and the effect of litter removal was 2.55 % and 2.32 % for AS and BS respectively. The results indicate that current global terrestrial models underestimate RL trends for the feedback of global climate change in subtropical forests.

PSXVI-5 Rumen Parameters and Microbial Population Changes in Fattening Holstein Heifers fed with Nitrate-Contaminated Water

Abstract The aim of this study was to evaluate the effect of drinking water nitrate concentration on rumen parameters and its microbial population that may affect greenhouse gases in fattening cattle. Holstein heifers (n = 24; 161 ± 19.9 kg of initial BW, and 183 ± 25.3 d of age) were housed individually and fed ad libitum. Animals were assigned to 4 treatments according to nitrate concentration in drinking water: 1) Control (n=6), without NO3-; 2) Low (n=6), with 44 mg/L of NO3-; 3) Moderate (n=6), with 110 mg/L of NO3-, and 4) High (n=6), with 220 mg/L of NO3-. After 14 and 168 days the ruminal content was sampled to determine pH, volatile fatty acids (VFA), nitrate and nitrite concentration, and rumen microbiota (except for Moderate). To assess the rumen microbiota, DNA-based qPCR of total bacterial population (16S rRNA), dissimilatory sulfate-reducing prokaryotes (aprA), ammonia-oxidizing bacteria and archaea (amoA-AOB and amoA-AOA), typical complete denitrifiers (nosZ-clade I linked to the transformation of N2O to N2), and anammox bacteria (hzo) was determined. Rumen pH, VFA, nitrate and nitrite were analyzed with a mixed effects model. Rumen microbial populations were statistically treated by analysis of variance applying pairwise comparisons (Fisher's least). Rumen pH, VFA, nitrate and nitrite were not affected by nitrate concentration in drinking water; however, rumen nitrite concentrations were greater (P &amp;lt; 0.01) in d 14 than in d 168 (32.1 vs. 6.3 ± 4.20 mg/L, respectively). Nitrate drinking water concentration did not affect rumen microbial populations, except for complete-denitrifying population (nosZ-clade I) which were slightly greater (P=0.01) in High than in Control in d 168. In conclusion, nitrate-contaminated water did not show a significant impact on rumen parameters and microbial populations but increased the bacterial denitrifying potential after a long term, which could decrease ruminal N2O emissions and nitrite ruminal accumulation in fattening heifers.

Drinking water nitrate and risk of pregnancy loss: a nationwide cohort study

BackgroundNitrate contamination is seen in drinking water worldwide. Nitrate may pass the placental barrier. Despite suggestive evidence of fetal harm, the potential association between nitrate exposure from drinking water and pregnancy loss remains to be studied. We aimed to investigate if nitrate in drinking water was associated with the risk of pregnancy loss.MethodsWe conducted a nationwide cohort study of 100,410 pregnancies (enrolled around gestational week 11) in the Danish National Birth Cohort (DNBC) during 1996–2002. Spontaneous pregnancy losses before gestational week 22 were ascertained from the Danish National Patient Registry and DNBC pregnancy interviews. Using the national drinking water quality-monitoring database Jupiter, we estimated the individual and time-specific nitrate exposure by linking geocoded maternal residential addresses with water supply areas. The nitrate exposure was analyzed in spline models using a log-transformed continuous level or classified into five categories. We used Cox proportional hazards models to estimate associations between nitrate and pregnancy loss and used gestational age (days) as the time scale, adjusting for demographic, health, and lifestyle variables.ResultsNo consistent associations were found when investigating the exposure as a categorical variable and null findings were also found in trimester specific analyses. In the spline model using the continuous exposure variable, a modestly increased hazard of pregnancy loss was observed for the first trimester at nitrate exposures between 1 and 10 mg/L, with the highest.adjusted hazard ratio at 5 mg/L of nitrate of 1.16 (95% CI: 1.01, 1.34). This trend was attenuated in the higher exposure ranges.ConclusionNo association was seen between drinking water nitrate and the risk of pregnancy loss when investigating the exposure as a categorical variable. When we modelled the exposure as a continuous variable, a dose-dependent association was found between drinking water nitrate exposure in the first trimester and the risk of pregnancy loss. Very early pregnancy losses were not considered in this study, and whether survival bias influenced the results should be further explored.

Iron‐Based Nanocatalysts for Electrochemical Nitrate Reduction

Nitrate has a high level of stability and persistence in water, endangering human health and aquatic ecosystems. Due to its high reliability and efficiency, the electrochemical nitrate reduction reaction (NO3 RR) is regarded as the best available option for mitigating excess nitrate in water and wastewater, especially for the removal of trace levels of nitrate. One of the most critical factors in the electrochemical reduction are the catalysts, which directly affect the reaction efficiency of nitrate removal. Iron-based nanocatalysts, which have the advantages of nontoxicity, wide availability, and low cost, have emerged as a promising electrochemical NO3 RR material in recent years. This review covers major aspects of iron-based nanocatalysts for electrochemical NO3 RR, including synthetic methods, structural design, performance enhancement, electrocatalytic nitrate reduction test, and reduction mechanism. The recent progress of iron-based nanocatalysts for electrochemical NO3 RR and the mechanism of functional advantages for modified structures are reviewed from the perspectives of loading, doping, and assembly strategies, in order to realize the conversion from pollutant nitrate to harmless nitrogen or ammonia and other sustainable products. Finally, challenges and future directions for the development of low-cost and highly-efficient iron-based nanocatalysts are explored.

Energy, environmental and economic assessment of waste-derived lemon peel oil intermingled with high intense water and cetane improver

Waste-to-energy and its utilization in the commercial field have received wider attention in recent years. Lemon peel oil (LPO), a food waste by-product is used for this study to produce bioenergy, and a novel approach has been attempted to improve energy and environmental efficiency. The LPO was blended with different percentages of water and 2-Ethylhexyl nitrate (EHN) and the energy, environmental and economic assessments were carried out. The outcomes show that LPO dominates the normal diesel in all aspects, except for NOx emission, and 10% of water in LPO (10WLPO) improves the overall performance. Meanwhile, this trend is reversed for 20% water in LPO (20WLPO) due to a longer ignition delay period and low cetane numbers. EHN plays a vital role in fuel modification and EHN blended 20WLPO significantly improves the engine characteristics, and the engine behavior is identical to 10WLPO. The cost-benefit analysis shows that 10WLPO fuel significantly reduces the running cost compared to LPO, and the cost is further reduced to 12% while the LPO is blended with EHN.

Construction of bidirectional electron transfer biofilms via periodic polarity reversal

Bioelectrochemical denitrification has been widely applied to remove nitrate in water. Thereinto, bidirectional electron transfer biofilm removes nitrate effectively without nitrite accumulation. However, it is critical to maintain bidirectional electron transfer capability of biofilm. In this study, periodic polarity reversal strategy was applied to cultivate bidirectional electron transfer biofilm. The nitrate removal was observed at 93 ± 5.9 % in bidirectional electron transfer system (R1) cultivated by periodic polarity reversal strategy. High bio-community similarity was observed in anode and R1 biofilm with Geobacter sp. as dominant bacteria, indicating that the periodic polarity reversal strategy sustained anodic respiring bacteria. The exoelectrogens (Geobacter pickeringii) and denitrifiers (Chryseobacterium sp., Acidovorax sp. and Stenotrophomonas sp.) exhibited a positive correlation, implying interspecies mutualistic growth. Electroactive sites in R1 and anode biofilm derived from turnover CVs and DPVs were within the same range, indicating that the sustained anodic respiring bacteria also played essential role in cathodic electron transfer. Periodic polarity reversal utilized the “Bio-pseudocapacitance” feature of electroactive biofilm, making it possible to donate stored electrons (at anode period) for nitrate reduction in cathode period. The detailed contributions of direct electron transfer (DET) and mediated electron transfer (MET) were investigated to reveal the electron transfer mechanism at the bacteria-electrode interface. Different electron transfer pathway was suggested for electron donating and extracting process in this bidirectional electron transfer biofilm. Generally, periodic polarity reversal strategy provides an effective way to regulate bidirectional electron transfer biofilm and utilize the “Bio-pseudocapacitance” feature of biofilm to facilitate bioelectrochemical nitrate reduction.

Distinguishing and quantifying the fate of nitrate in irrigation water and nitrate produced by ammonium nitrification.

When the sources of nitrogen include not only ammonium (NH4+) fertilizer (ANF) but also nitrate (NO3-) from groundwater and rainfall (NRI), if the proportions of various types of NO3- are still based on the amount of ANF, the corresponding calculation method may be complicated. This paper established a water flow-nitrogen migration transformation model for the unsaturated zone in grain-planting and vegetable-planting areas, and studied the migration and transformation of NH4+ and NO3- in the unsaturated zone when ANF and NRI coexist. This paper proposed for the first time the proportional coefficient method (PCM) and hypothetical assignment method (HAM) to distinguish and quantify the fate proportions of NO3- from NO3- produced by NH4+ nitrification (NNR) and NRI. The results showed that the PCM was more practical than the HAM in quantifying the fate of NO3- from different sources. If only the root absorption ratio was used to evaluate the degree of nutrient supply to crops, the ratios of root absorption were as high as 40% (44.75-50.85%). NRI provided more nutrients in grain-growing areas than those in vegetable-growing areas. If the sum of the proportion of other fates was regarded as the degree of groundwater NO3- mitigation through irrigation in the unsaturated zone, except for the ratio of NO3- leaching to groundwater, the proportion of NO3- pollution mitigation was as high as 57.89% (57.89-92.99%), and the mitigation ability of groundwater NO3- pollution in grain-growing areas was higher than that in vegetable-growing areas.

Impact of long-term agricultural farming on soil and water chemical properties: A case study from Al-Batinah regions (Oman)

Long term intensive agricultural farming has impacted negatively the soil health, especially in arid climates. This study aimed to investigate the impact of long-term (1993 to 2020) farming practices on the chemical and biological properties of soil and water of Al-Batinah region. Soil and water samples were collected from eight farms and characterized for their chemical and biological soil properties. The results of soil samples indicated significant (p ≤ 0.05) changes in average soil chemical and biological properties over time. Soil electrical conductivity (ECe) increased from 'low salinity' (1.5 dS m −1 ± 0.49) to 'highly saline' (6.6 dS m −1 ± 1.35), and soil pH decreased from 8.4 to 7.5. The organic matter increased from 'very low' (0.2%) to 'medium' (1.9%), and the Olsen phosphorus increased from deficient (6.5 mg kg −1 ± 0.9) to excessive (76 mg kg −1 ± 10.4). Sodium, magnesium, chloride, and sulfate ions were also significantly increased during this period, while no significant differences was observed in soil potassium, and calcium concentration. The soil (ECe) showed significant positive correlation with soil sodium, magnesium, chloride, sulfate, potassium, calcium, and water electrical conductivity (EC), nitrate, sodium, potassium, and significant negative correlation with soil pH. Soil organic matter showed significant a positive correlation with soil phosphorus. Soil sodium showed significant positive correlations with soil magnesium, chloride, sulfate, potassium, calcium, and water electrical conductivity (EC), nitrate, sodium, and potassium. The Al-Batinah region soils showed some positive changes including an increase in organic matter, and a decrease in soil pH. Also, negative changes occurred such an excessive increase of soil phosphorus, sodium, magnesium, chloride, and sulfate ions. Our findings can be used to inform the public policies and strategies for a more sustainable soil and agricultural management in Oman..

Larvicidal activity of acetone extract and green synthesized silver nanoparticles from Allium sativum L. (Amaryllidaceae) against the dengue vector Aedes aegypti L. (Diptera: Culicidae)

Mosquito vectors of major human diseases are currently controlled using chemical and biological products. Extensive insecticide use has led to resistance development and human/environmental health risks, and alternative sustainable control options are needed; in this study, activity of an extract of garlic (Allium sativum; Amaryllidaceae), and silver nanoparticles (AgNPs) synthesized from the extract, were evaluated against 2nd and 3rd instar larvae of the yellow fever mosquito, Ae. aegypti (Diptera: Culicidae). Synthesis of AgNPs was confirmed using UV–Vis spectroscopy, and characterised using powdered X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Larvae were exposed to five concentrations (50, 100, 150, 200, 250 ppm) of garlic extract or synthesized AgNPs, with distilled water and silver nitrate solution (1 mM) as controls. The mortality of larvae was recorded after 6, 12, 24, 36, and 48 h following addition of the respective extracts. Dose- and time-dependent toxicity were recorded in both treatment groups with no mortality in control groups. Exposure to AgNPs at 250 ppm for 48 h yielded 100% mortality for both larval instars, with corresponding LC50 values of 44.77 (2nd) and 62.82 ppm (3rd). Exposure to garlic extract resulted in similar 48-hour mortality (99 ± 0.77% (2nd) and 98 ± 1.10% (3rd), but consistently higher LC50 values after all exposure times compared to AgNPs (e.g. 48-hour exposure: 108.42 ppm (2nd), 129.11 ppm (3rd), suggesting that AgNPs may potentially be used at lower concentrations for Ae. aegypti control.

Nitrate removal in saline water by photo-reduction using natural FeTiO3 as catalyst

As climate change progresses, there is an increasing interest on the use of non-conventional water sources such as brackish or saline waters. Nowadays, the main threat in Europe detected in these waterbodies is nitrate contamination. Within the multiple available methods studied for nitrate reduction, photocatalysis presents promising results, but this technology has not yet been tested in saline water. This work tackles the elimination of nitrate ([NO3−] =50 mg/L) in brackish and saline water ([sea salt] = 5–33 g/L) using ilmenite as photocatalyst and oxalic acid as an environmental-friendly reducing agent. The main challenge when working in saline water is to overcome oxalic acid scavenging by Ca2+ present in the water matrix. This can be solved either working at over stoichiometric concentrations of oxalic acid (≈300% stoich. dose) or acidifying the reaction media. The addition of hydrochloric acid ensures the protonation of oxalic acid, reducing drastically its precipitation as CaC2O4. Working at [C2O42−] = 180 mg/L, [FeTiO3] = 450 mg/L and [HCl 37%] = 13 mM, 73% total nitrogen (TN) elimination was reached after 420 min. Reaction temperature was also evaluated in the range of 20–80 °C, which allowed to calculate the Ea=9.8 kJ/mol. Finally, the effect of dissolved O2 on the TN reduction was assessed. Overall, photocatalytic nitrate reduction presents itself as a feasible technology regardless of the water salinity.

Simultaneous Removal of Nitrate and Tetracycline by an Up-Flow Immobilized Biofilter

The removal of nitrate (NO3−-N) and antibiotics in aquaculture tail water is urgent and necessary. A lab-scale up-flow immobilized biofilter (I-BF) filled with polyurethane foam (PUF) carriers and a microbial consortium was developed for simultaneous removal of nitrate and tetracycline (TC). The denitrification and TC removal performance of the I-BF reactor was investigated under different TC concentrations (0, 10, 50, 100 mg·L−1), carbon/nitrogen (C/N) ratio (2, 4, 5, 6) and hydraulic retention times (HRT) (4, 8, 12 h). Simultaneous removal of nitrogen and TC was achieved by the I-BF reactor. Low TC concentration (≤50 mg·L−1) had little effect on nitrogen removal. The denitrification performance of the I-BF reactor was inhibited at high TC load, which may be attributed to the damage of cell membranes and the inhibition of the intracellular denitrification enzymes’ activities. The optimal C/N ratio and HRT were 5 h and 8 h with almost complete denitrification and high TC removal efficiency (73.46%) at influent NO3−-N and TC concentrations of 100 mg·L−1 and 50 mg·L−1, respectively. The I-BF reactor proposed in this study has promising applications such as the treatment of piggery wastewater, aquaculture tail water and pharmaceutical wastewater co-contaminated with nitrate and antibiotics.