Nitrate In Water Research Articles

Dual-Site W-O-CoP Catalysts for Active and Selective Nitrate Conversion to Ammonia in a Broad Concentration Window.

Environmentally friendly electrochemical reduction of contaminated nitrate to ammonia (NO3 - RR) is a promising solution for large quantity ammonia (NH3 ) production, which, however, is a complex multi-reaction process involving coordination between different reaction intermediates of nitrate reduction and water decomposition-provided active hydrogen (Hads ) species. Here, a dual-site catalyst of [W-O] group-doped CoP nanosheets (0.6W-O-CoP@NF) has been designed to synergistically catalyze the NO3 - RR and water decomposition, especially the reactions between the intermediates of NO3 - RR and water decomposition-provided Hads species. This catalytic NO3 - RR exhibits an extremely high NH3 yield of 80.92mg h-1 cm-2 and a Faradaic efficiency (FE) of 95.2% in 1m KOH containing 0.1m NO3 - . Significantly, 0.6W-O-CoP@NF presents greatly enhanced NH3 yield and FE in a wide NO3 - concentration ranges of 0.001-0.1m compared to the reported. The excellent NO3 - RR performance is attributed to a synergistic catalytic effect between [W-O] and CoP active sites, in which the doped [W-O] group promotes the water decomposition to supply abundant Hads , and meanwhile modulates the electronic structure of Co for strengthened adsorption of Hads and the hydrogen (H2 ) release prevention, resultantly facilitating the NO3 - RR. Finally, a Zn-NO3 - battery has been assembled to simultaneously achieve three functions: electricity output, ammonia production, and nitrate treatment in wastewater.

Copper(II) сomplexes with 2-hydrохy-5-ethylphenylphosphosphonic acid: synthesis, structure, cytotoxicity, and accumulation in HeLa cells

In order to study the physicochemical and biological properties of the coordination compounds of bioactive metal ions with 2-hydroxyphenylphosphonic acid derivatives, the reaction of 2-hydroxy-5-ethylphenylphosphonic acid (Н3L1) with copper(II) perchlorate, sulfate, nitrate, and acetate in water was studied for the first time. It has been established that, regardless of the ratio of reagents, in the case of copper(II) perchlorate, sulfate, and nitrate, a complex of the composition [Cu(H2L1)2(Н2О)2] is formed in high yield, while in the case of using copper(II) acetate a complex [Cu(HL1)(H2O)2] is formed, the composition of which is established on the basis of a combination of elemental analysis data, IR and electronic spectra. Quantum-chemical calculations of the structure of [Cu(H2L1)2(H2O)2] and [Cu(HL1)(H2O)2] complexes were performed for the first time by the density functional theory (DFT) method. The cytotoxic properties of H3L1 acid and copper complexes [Cu(HL1)(H2O)2] and [Cu(H2L1)2(H2O)2] with respect to HeLa tumor cells of human cervical adenocarcinoma were studied. The accumulation of the resulting copper(II) complexes in HeLa cells was proved by laser confocal microscopy.

Temporal and Spatial Distribution Characteristics and Source Analysis of Nitrate in Surface Water of Wuding River Basin

The Wuding River Basin is a first-class tributary of the Yellow River, and the quality of its water ecological environment has a profound impact on the ecological protection and high-quality development of the Yellow River Basin. In order to identify the source of nitrate pollution in the Wuding River Basin, surface water samples of the Wuding River were collected from 2019 to 2021, and the temporal and spatial distribution characteristics and influencing factors of nitrate concentration in surface water in the basin were explored. Nitrogen and oxygen isotope tracer technology and the MixSIAR model were used to qualitatively and quantitatively determine the sources of surface water nitrate and their contribution rates. The results showed that there were significant spatial and temporal differences in nitrate concentrations in the Wuding River Basin. In terms of time, the mean concentration of NO-3-N in surface water in the wet season was higher than that in the flat-water period; spatially, the mean concentration of NO-3-N in the downstream surface water was higher than that in the upstream. The spatial and temporal differences in surface water nitrate concentrations were mainly affected by rainfall runoff, soil types, and land use types. The main sources of nitrates in the surface water of the Wuding River Basin during the wet season were domestic sewage, manure, chemical fertilizers, and soil organic nitrogen, whose contribution rates were 43.3%, 27.6%, and 22.1%, respectively, and the contribution rate of precipitation was only 7.0%. There were differences in the contribution rate of nitrate pollution sources in surface water of different river sections. The contribution rate of soil nitrogen in the upstream was significantly higher than that in the downstream, which was 26.5%. The contribution rate of domestic sewage and manure in the downstream was significantly higher than that in the upstream, which was 48.9%. To provide a basis for the analysis of nitrate sources and pollution control in Wuding River and even rivers in arid and semi-arid regions.

Factors Affecting Nitrate Concentrations and Nitrogen and Oxygen Isotope Values of Effluents from Waste Water Treatment Plant

Urban domestic sewage is one of the important nitrate (NO-3) sources for surface water; however, their NO-3 concentrations and nitrogen and oxygen isotope values (δ15N-NO-3 and δ18O-NO-3) remain unclear, and the factors affecting NO-3 concentrations and δ15N-NO-3 and δ18O-NO-3 values of effluents in the waste water treatment plant (WWTP) are still unknown. Water samples in the Jiaozuo WWTP were collected to illustrate this question. Influents, clarified water in the secondary sedimentation tank (SST), and effluents of the WWTP were sampled every 8 h. The ammonia (NH+4) concentrations, NO-3 concentrations, and δ15N-NO-3 and δ18O-NO-3 values were analyzed to elucidate the nitrogen transfers through different treatment sections and illustrate the factors affecting the effluent NO-3 concentrations and isotope ratios. The results indicated that ① the mean NH+4 concentration was (22.86±2.16) mg·L-1 in the influent and decreased to (3.78±1.98) mg·L-1 in the SST and continuously reduced to (2.70±1.98) mg·L-1 in the effluent of the WWTP. The median NO-3 concentration was 0.62 mg·L-1 in the influent, and the average NO-3 concentration increased to (33.48±3.10) mg·L-1 in the SST and gradually increased to (37.20±4.34) mg·L-1 in the effluent of the WWTP. ② The mean values of δ15N-NO-3 and δ18O-NO-3 were (17.1±10.7)‰ and (19.2±2.2)‰ in the influent of the WWTP, the median values of δ15N-NO-3 and δ18O-NO-3 were 11.9‰ and 6.4‰ in the SST, and the average values were (12.6±1.9)‰ and (5.7±0.8)‰ in the effluent of the WWTP. ③ The NH+4 concentrations of influent had significant differences compared to those in the SST and the effluent (P<0.05). The reduction of NH+4 concentrations in the SST was due to the above nitrification during the aerobic treatment process, which transferred NH+4 to NO-3. The NH+4 concentrations in the SST had no significant differences with that in the effluent of the WWTP (P>0.05). ④ The NO-3 concentrations in the influent had significant differences with those in the SST and the effluent (P<0.05), and minor NO-3 concentrations but relatively high δ15N-NO-3 and δ18O-NO-3 values in the influent were probably due to denitrification during the pipe sewage transportation. The obviously increased NO-3 concentrations (P<0.05) but decreased δ18O-NO-3 values (P<0.05) in the SST and the effluent resulted from water oxygen incorporation during the nitrification. The above results confirmed the impacts of aerobic and anaerobic treatment processes on NO-3 concentrations and isotope ratios of effluent from the WWTP and provided scientific basis for the identification of sewage contributions to surface water nitrate via average δ15N-NO-3 and δ18O-NO-3 values.

KARAKTERISTIK DISTRIBUSI ZAT HARA NITRAT DAN FOSFAT PADA AIR DAN SEDIMEN DI ESTUARIA TANJUNG LIMAU KOTA BONTANG KALIMANTAN TIMUR

This research was conducted in May 2021 - January 2022. The purpose of this study was to determine the distribution of nitrate and phosphate content in water and sediment in the Tanjung Limau estuary, Bontang City, East Kalimantan. Sampling of water and sediment was carried out at 4 research stations using a random method which was then analyzed at the Water Quality Laboratory and Soil Science Laboratory of PPLH Mulawarman University. The results showed that the nitrate content in the water was 0.012-0.018mg/L, 4.20-9.09% in the sediment, while the phosphate in the water was 0.014-0.077 mg/L and the phosphate in the sediment was 0.021-0.030%. The results of the analysis show that the nitrate and phosphate content is higher at Station 1 and lower towards Station 4. There is a significant difference between the nitrate and phosphate content in the water and in the sediment. The content of nitrate and phosphate is mostly sourced from upstream of the river, namely in residential areas and mangrove forests.

Dietary inclusions of black soldier fly (Hermetia illucens) larvae frass enhanced production of channel catfish (Ictalurus punctatus) juveniles, stevia (Stevia rebaudiana), and lavender (Lavaridula angustifolia) in an aquaponic system

In aquaponic systems, adding supplemental nutrients to enhance plant production is common. Frass, which is the manure of insects, can be used to enhance fish and plant production, but no study has yet examined the potential to enhance both using a dietary approach in an aquaponic system. In this 8-week study, channel catfish (Ictalurus punctatus) juveniles were fed diets with, or without, 10% black solider fly (Hermetia illucens) larvae (BSFL) frass in an aquaponic system. Each aquaponic system had two different plant bed types; floating raft or media. Each plant bed consisted of three stevia (Stevia rebaudiana) and three lavender (Lavaridula angustifolia) plants in a 2 × 2 factorial design, with the main effects of dietary frass inclusion and media type. After 8 weeks, channel catfish grew significantly faster when fed a diet containing 10% BSFL frass compared to fish fed the control diet. Further, dietary frass upregulated the hepatic expression of IGFβ, IGF-1 and GHR as well as reduced intestinal inflammation based on histological observations and scoring. The muscle proximate composition of channel catfish was unaffected by diet, while only taurine was significantly reduced by dietary frass. Muscle calcium and phosphorus as well as C14:0 and C15:0 were significantly elevated by dietary frass. For plants, both stevia and lavender had significantly more biomass when frass was added to the system, while plants grown in media beds were larger than plants grown in a floating raft subsystem. Frass significantly increased phosphorus in both stevia and lavender at week 8. The higher water calcium, magnesium, and nitrate levels may have allowed for better plant growth as these are essential nutrients. The significant increase of catfish growth was likely due to the upregulation of genes responsible for growth, mitigating intestinal inflammation, and significantly enhancing diet intake. Thus, it may be recommended that feeding catfish with BSFL frass and culturing stevia and lavender in media beds can substantially improve overall productivity.

Assessment of nitrate, trace elements and bacterial contamination of groundwater in ilora area of southwestern nigeria

Assessments of groundwater pollution parameters were carried out in groundwater samples collected from selected shallow hand-dug wells across Ilora township. The analysed parameters were nitrate, trace elements including, iron, cobalt, chromium, manganese, zinc, arsenic, cadmium and lead, and bacteria count in water; using spectrophotometric method, HM Metalyser 5000 and multiple tube techniques respectively. The pH of the samples was between 6.4 and 7.6 and TDS range was 50 - 640 mg/l. The concentration of nitrate (NO3) in water was 12.8 - 274 mg/l. For trace elements concentrations in µg/l ; iron (Fe): 150 – 880, Cobalt (Co): 1 – 100, Manganese (Mn): 0.01 - 140, Chromium (Cr): 0.01 – 0.31, Zinc (Zn): 1.86 - 9.97, Arsenic (As): 3.11 - 20.80, Cadmium (Cd): 0.71 - 4.76, Lead (Pb): 1.00 – 6.82. Based on the average concentration of the trace elements the order of abundance was Fe &gt; Co &gt; Mn &gt; As &gt; Zn &gt; Pb &gt; Cd &gt; Cr. Total coliform count (TCC) in groundwater samples were between 18 and 370 cfu/100mL. From the evaluation of the degree of association between the parameters, a moderate to strong positive relationship occurred between Fe/Mn (0.59), Fe/Cr (0.85), Fe/TC (0.56), NO3/Co (0.56), NO3/Mn (0.48), NO3/Cd (0.51) and Mn/Pb (0.85). Presence of coliform bacteria in the groundwater samples indicated fecal contamination from surface environment. Comparing the parameters with guideline standards for drinking water, most of the hand-dug wells are contaminated with nitrate, five wells were contaminated with either arsenic and/or cadmium, while water from some of the wells may have objectionable taste due to high iron content. The high values of cadmium and arsenic in some wells are harmful to human health and appropriate treatment is needed. For bacteria contamination, deeper wells are recommended, and the water should to be treated and boiled prior to consumption.&#x0D;

Quality assessment and evaluation of irrigation water and soil used for maize (Zea mays L.) production in Boloso Sore district, southern Ethiopia

Poor quality of irrigation water and soil are among the major factors determining maize productivity in Ethiopia. This study assessed and evaluated the quality of irrigation water and soil under maize production in Soke and Woybo irrigation schemes in Boloso Sore district, Ethiopia. Four water samples per site per season were collected from the first point of the irrigation schemes and farm gate for dry and rainy seasons in 2019/2020. Soil samples of 108 were collected from 36 points, from which 18 composited samples were taken for laboratory analysis. Results show that irrigation water of the two schemes is non-saline (electrical conductivity <0.2 dS m−1) and in the normal pH range (6.5–7.5). Maximum concentration of cations in irrigation water was in the order of sodium (22.3 mg l−1) > potassium (7.3 mg l−1) > calcium (6.2 mg l−1) > magnesium (3.1 mg l−1). Moderate to severe sodicity (sodium adsorption ratio of 10.9) was also recorded. Sulfate, nitrate, and phosphate contents in water were trace, and increased during rainy seasons in downstream. Textural classes of soils are clay loam to clay, and less compact to restrict root penetration (bulk density ≤1.4 g cm−3), have slow infiltration rate (≤0.13 cm h−1), and medium level of total available water (≤178 mm m−1). Soils are strongly acidic to neutral (pH: 5–6.5), salt-free, and have low soil organic carbon (≤2.1%), low total nitrogen (≤0.1%), low available phosphorus and sulfur, and low Ca2+: Mg2+ ratio. It can be concluded that the irrigation water in the study area has cation imbalance (poor quality) which affects soil quality and maize productivity. Likewise, soils of the study area have poor quality. Lime application, efficient fertilizer use, and organic matter applications can be suggested. Further study on optimizing fertilizer rates and irrigation levels has to be conducted to improve maize productivity.

Water quality and financial feasibility analysis of the development of milkfish (Chanos sp.) farms in Pabean Ilir Village, Indramayu, West Java

The tidal flood that occurred in the coastal area of Indramayu in 2020 caused the farmers to fail the Vannamei shrimp harvest in Pabean Ilir Village. After the disaster, the farmers resumed their commodity with milkfish. To analyze if this strategy can compensate for the loss, it is essential to perform the feasibility and profitability of the new farming system. Water quality sampling, which referred to the standard method (APHA), was conducted at several sites in the pond. We elucidated the pattern of several water quality parameters such as water temperature, pH, salinity, dissolved oxygen, nitrite, nitrate, and ammonia, while the financial feasibility was assessed with a cost-benefit analysis. The data to conduct the analysis was collected by arriving series of structured face-to-face interviews and focus group discussions. A sensitivity analysis was carried out to measure the influence of changes in fish production and feed price. It is concluded that the water quality was suitable and safe for milkfish cultivation. We also noticed that the new aquaculture system was financially feasible, as indicated by the calculated net present value, benefit-cost ratio, and internal rate return.

Environmental Quality of Lake Mainit as a Habitat of Indigenous Goby, Glossogobius giuris (Hamilton, 1882) in Northeastern Mindanao, Philippinese

Changes in environmental quality of Lake Mainit could adversely affect the inhabiting organisms like the indigenous goby, Glossogobius giuris or pijanga. Hence, a thorough 16-month (i.e. December 2016 to March 2018) water quality study was undertaken, specifically on obtaining data for water temperature (OC), Dissolved Oxygen (ppm), pH, nitrate (NO3-N, ppm), ammonia (NH3-N, ppm), nitrite (NO2-N, ppm), phosphate (PO4-N, ppm) and light intensity (Lum/ft2) at the seven (7) established sampling stations within the Lake. Standard collection of water samples and their physico-chemical analyses were done and results were compared to DENR standards for freshwater water bodies. Results showed that the water quality of the Lake were still within the desirable range for Class A and Class C waters. This answered the underlying occurrence of fish kills to other factors and not on water quality changes. Highlight of this study is the notable increase of 0.9oC for surface and vertical temperatures of Lake Mainit over a decade and would show a glaring impact of global warming. Based on the 16 months monitoring, turnover occurred once in the Lake, particularly during northeast monsoon, indicating that Lake Mainit is a “monomictic Lake.”

Study on the Treatment of Simulated Recirculating Mariculture Wastewater by Thiosulfate-Based Autotrophic Denitrification

In this study, a sulfur-based autotrophic denitrifying filter (SADF) was developed for the purpose of removing nitrate from simulated recirculating mariculture wastewater. Results showed that over 90% of the nitrate could be effectively eliminated by utilizing thiosulfate as the electron donor, with a molar ratio of thiosulfate-S to nitrate molar ratio of 2:1 or greater. Additional batch tests confirmed that thiosulfate was a suitable sulfur source for nitrate removal even without prior accumulation of the biomass to nitrite. Excess thiosulfate had a minor impact on N-removal efficiency, so an external sulfur source was not required for nitrate removal, however, it could still help to reduce nitrate accumulation and water replacement to some extent. High-throughput sequencing results illustrated that Thiomicrospira and Thioalkalivibrio were the dominant autotrophic denitrifying genera in the SADF, while Thiomicrospira was more significantly affected in the case of insufficient sulfur sources. As the issue of nitrate accumulation in the mariculture recirculating system has been resolved, only a small amount of water needs to be added to the system daily. Therefore, the thiosulfate-based SADF process has the potential to be implemented for nitrate removal in mariculture systems, which could present a promising sustainable solution to the nitrate pollution issue.

Synthesis, X-ray Structure of Two Hexa-Coordinated Ni(II) Complexes with s-Triazine Hydrazine Schiff Base Ligand

The hydrazine s-triazine ligand (E)-4,4’-(6-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1,3,5-triazine-2,4-diyl)dimorpholine (DMPT) was used to synthesize two new Ni(II) complexes via a self-assembly technique. The two complexes were synthesized by a one-pot synthesis strategy and characterized by elemental analysis, FTIR and single-crystal X-ray diffraction analysis to be [Ni(DMPT)(H2O)3](NO3)2.3H2O (1) and [Ni(DMPT)(H2O)3](NO3)2.H2O (2). The structures of both complexes were very similar regarding the coordination sphere and counter anions, but differ only in the number of the crystal water molecules. In the case of complex 1, there are three water molecules instead of one H2O molecule as in complex 2. In the two complexes, the DMPT ligand acts as a neutral tridentate NNN-chelate via three Ni–N coordination interactions. The coordination sphere of the Ni(II) ion is completed by three water molecules. As a result, the two complexes exhibit distorted octahedral geometry. The Hirshfeld surfaces around each entity in both complexes have been computed. Subsequently, their corresponding intermolecular interactions were quantified separately. Because the number of crystal water molecules is different in both complexes, their monomeric units are connected differently in their crystal structures where the crystal water molecules act as both hydrogen bond donor and acceptor. The polar O…H interactions are the most dominant in all entities of both complexes. As a result, strong O…H interactions are the driving force in the crystal packing of both complexes, and this is attributed to the presence of the nitrate anions and water molecules. The antimicrobial activity of the free ligand and complex 1 were determined against two selected fungal species, Gram-negative and Gram-positive bacterial strains. The free ligand was found to be inactive against all microbial species. On the other hand, the Ni(II) complex 1 was found active against the Gram-positive bacterial species Bacillus subtilis and also the Gram-negative bacterial species Escherichia coli. The respective inhibition zone diameter of the Ni(II) complex was 12 and 11 mm, respectively.

Effect of waste disposal sites on physicochemical properties of water in selected states of Southeast Nigeria.

Water bodies are constantly being degraded by leachates from waste disposal sites, particularly in the Nigeria cities. This paper investigates the effect of waste disposal sites on physicochemical properties of water in selected states of Southeast Nigeria. To achieve the main aim of the study, three waste disposal sites were selected from three cities based on their proximity to streams. Wet and dry seasonal effects were also noted. The experiment was laid out in a Randomized Complete Block Design, with four replications for 3years, and data collected was analyzed statistically. The result indicated that biological oxygen demand (BOD) values of 29.31 ± 1.60mg/L, 23.87 ± 2.32mg/L, and 32.73 ± 1.30mg/L at Abakaliki, Enugu, and Awka in the wet period decreased by 2%, 17%, and 10% respectively, relative to the dry season values, and were significantly (p < 0.05) higher relative to the respective controls. The result also proved that values of chemical oxygen demand (COD), nitrate (NO3-), and turbidity in water presented similar results. However, more findings from this study showed an evidence of more pollution loads from the waste disposal sites in the wet period relative to the dry season due possibly to increased leachate and run-off coming out of the sites to the surface water bodies. Based on the findings, the study strongly recommends proper awareness to avoid contamination/pollution of surface water bodies within the vicinity of the waste dump sites among the immediate settlement that make use of the environment in order to safe-guard their lives.

Simulation of water drainage and nitrate leaching at an irrigated maize (Zea mays L.) oasis cropland with a shallow groundwater table

Nitrogen pollution is a serious threat to water resources worldwide, and it poses a particular threat to groundwater in desert oases where the water table is shallow. Leaching loss of nitrogen fertilizer means economic loss and threatens the water quality of phreatic aquifer with a thinner vadose zone thickness, especially in the Hailiutu River catchment, China, where phreatic aquifer is a unique source of local domestic water. The objective of this study was to quantify N leaching for irrigated maize with different fertilizer and irrigation management practices, as well as fluctuating groundwater tables, and to recommend the best management practices for maize. A field experiment was conducted in such a locale for two consecutive years. Maize was grown where nitrogen was introduced at increasing rates (from 38 to 438 kg N ha−1, at intervals of 100 kg N ha−1). The 338 kg N ha−1 represented the conventional fertilization practice (N338), and served as a reference. Unlike the conventional 70 mm irrigation depth applied at each water application, water conserving irrigation was performed by applying only 20 mm at each irrigation — six times in 2017 and four in 2018. The HYDRUS-1D model was first calibrated against measured soil moisture and nitrate in soil water across all soil layers, then independently validated and finally repeatedly run to simulate NO3N leaching under the following simulation conditions: a) increasing N fertilization rate, but fixed 20 mm individual irrigation depth; b) increasing individual irrigation depth (from 10 to 70 mm), but only considering the reference N fertilization rate (N338). In both cases, five different shifts in water table depth were assumed, + 0.10, 0, − 0.10, − 0.20, or − 0.30 m of groundwater table change, respectively. The simulation results suggest that conventional fertilization practices result in nitrogen losses of over 100 kg ha−1, and 238 kg N ha−1 N fertilization, accompanying by a depth of 20 mm for each irrigation is the best combination of management practices. The NO3−N leaching loss was more influenced by the depth of irrigation than the fertilizer application rate. A shallower water table resulted in the greater loss of NO3N by leaching. Such results can help develop improved irrigation and nitrogen fertilization management for desert oasis cropping systems.

Influence of the synthesis method of layered double hydroxides on the textural properties and nitrate removal

Layered double hydroxides were prepared by co-precipitating Mg2+ and Al3+ ions at constant pH. Three different methods of solution additions and two temperatures for synthesis and aging were tested in each method. Through X-ray diffraction, it was confirmed that all the synthesized solids have a hydrotalcite-type structure, obtaining more crystalline compounds when one solution of Mg/Al is added to another whit CO3-/OH- and compounds with greater interlaminar spacing when three different solutions are added (Mg/Al, CO3- and OH-). In addition, the solids obtained by this last method have a higher specific surface area and total pore volume, as confirmed by the N2 adsorption-desorption. A similar trend occurs with synthesis and aging temperatures where better textural properties are obtained at a higher temperature, reaching surface area values of 242 m2/g and pore volume of 0,93 cm3/g. All the synthesized solids were active for removing nitrates in water, obtaining the best results with the samples prepared by dripping three different solutions at 60 °C (26 mgNO3-/g.) This fact demonstrates the correlation between the synthesis method and the textural properties of the material with its potential application in removing contaminants.

Thermophysical properties of n-alkyl-ammonium nitrate ionic liquids (n = 2,3,4) pure and water saturated for energy applications

Phase transition temperatures of three ionic liquids (ILs) with ammonium cations of different alkyl chain length and nitrate common anion were determined in this paper by differential scanning calorimetry. Thermal stability of these ILs in air and nitrogen atmosphere and the maximum operation temperatures of the compounds were also studied using a thermogravimetric analyser. Furthermore, thermophysical properties as density, viscosity, thermal conductivity, and heat capacity against temperature of these pure ionic liquids were determined and compared with the corresponding values for water saturated samples. For this purpose, different techniques were employed: for density and viscosity a rotational automated viscodensimeter; for thermal conductivity measurements a thermal conductimeter that follows the transient hot-wire method; and for heat capacity measurements a microdifferential scanning calorimeter. Different behaviours were observed depending on the analysed thermophysical properties. In case of dried samples, density and thermal conductivity decrease with alkyl chain; for saturated samples, same tendency is observed for density but is the opposite in case of thermal conductivity. Isobaric specific heat and viscosity increase with alkyl chain length in case of dried samples; for saturated samples same tendency is observed for the viscosity, whereas the tendency is the contrary in case of isobaric specific heat.

Defining the sources and the fate of nitrate by using dual isotopes and a Bayesian isotope mixing model: Water–nitrate management in cascade dams of Lancang river

A multi-isotopes approach involving the use of stable nitrate isotopes (δ15N-NO3− and δ18O-NO3−) combined with stable water isotopes (δD-H2O and δ18O-H2O) and SIAR model as tracers can help identify the nitrogen source and understand the transformation process in a river-cascade reservoirs system. In this study, we identify the potential impact of the N source in the Lancang River basin, clarified the seasonal variations in the isotope values and estimated the probability distribution and proportional contribution of multi-terminal NO3−-N sources using Bayesian isotope mixing model. In addition, we investigate the factors that led to the seasonal variations of the stable isotopes and evaluated the relationship between the uncertainty of the contribution ratio of the N sources and isotopic variations in the river-cascade reservoirs system. The NO3−-N is the main component of DIN (dissolved inorganic nitrogen), accounting for 68.1 % of DIN. The ratios of δ15N-NO3− and δ18O-NO3− ranged from +4.2 ‰ to +10.3 ‰, and from +5.9 ‰ to +9.3 ‰ in the Lancang River. The δD-H2O and δ18O-H2O of the surface waters ranged from −109.47 ‰ to −76.44 ‰, and from −15.13 ‰ to −11.61 ‰, respectively. The SIAR model analysis results show that nitrification of livestock and poultry manure is the main source of NO3−-N in the upstream natural reach, accounting for 40.2 %. There is little difference between the wet season and the dry season. Nitrification of soil organic nitrogen is the main source of NO3−-N in the cascade development reach, accounting for 42.3 %. The contribution rate of atmospheric precipitation to nitrate concentration in both sampling periods is low (<5 %). This study provides a useful insight for reservoir water environmental managers to verify cascade development river pollution contributors and to better apply remedial solutions.

A comparative study of data-driven models for runoff, sediment, and nitrate forecasting

Effective prediction of qualitative and quantitative indicators for runoff is quite essential in water resources planning and management. However, although several data-driven and model-driven forecasting approaches have been employed in the literature for streamflow forecasting, to our knowledge, the literature lacks a comprehensive comparison of well-known data-driven and model-driven forecasting techniques for runoff evaluation in terms of quality and quantity. This study filled this knowledge gap by comparing the accuracy of runoff, sediment, and nitrate forecasting using four robust data-driven techniques: artificial neural network (ANN), long short-term memory (LSTM), wavelet artificial neural network (WANN), and wavelet long short-term memory (WLSTM) models. These comparisons were performed in two main tiers: (1) Comparing the machine learning algorithms' results with the model-driven approach; In order to simulate the runoff, sediment, and nitrate loads, the Soil and Water Assessment Tool (SWAT) model was employed, and (2) Comparing the machine learning algorithms with each other; The wavelet function was utilized in the ANN and LSTM algorithms. These comparisons were assessed based on the substantial statistical indices of coefficient of determination (R-Squared), Nash-Sutcliff efficiency coefficient (NSE), mean absolute error (MAE), and root mean square error (RMSE). Finally, to prove the applicability and efficiency of the proposed novel framework, it was successfully applied to Eagle Creek Watershed (ECW), Indiana, U.S. Results demonstrated that the data-driven algorithms significantly outperformed the model-driven models for both the calibration/training and validation/testing phases. Furthermore, it was found that the coupled ANN and LSTM models with wavelet function led to more accurate results than those without this function.

Enhanced Decomposition of H2O2 Using Metallic Silver Nanoparticles under UV/Visible Light for the Removal of p-Nitrophenol from Water

Three Ag nanoparticle (NP) colloids are produced from borohydride reduction of silver nitrate in water by varying the amount of sodium citrate. These nanoparticles are used as photocatalysts with H2O2 to degrade a p-nitrophenol (PNP) solution. X-ray diffraction patterns have shown the production of metallic silver nanoparticles, whatever the concentration of citrate. The transmission electron microscope images of these NPs highlighted the evolution from spherical NPs to hexagonal/rod-like NPs with broader distribution when the citrate amount increases. Aggregate size in solution has also shown the same tendency. Indeed, the citrate, which is both a capping and a reducing agent, modifies the resulting shape and size of the Ag NPs. When its concentration is low, the pH is higher, and it stabilizes the formation of uniform spherical Ag NPs. However, when its concentration increases, the pH decreases, and the Ag reduction is less controlled, leading to broader distribution and bigger rod-like Ag NPs. This results in the production of three different samples: one with more uniform spherical 20 nm Ag NPs, one intermediate with 30 nm Ag NPs with spherical and rod-like NPs, and one with 50 nm rod-like Ag NPs with broad distribution. These three Ag NPs mixed with H2O2 in water enhanced the degradation of PNP under UV/visible irradiation. Indeed, metallic Ag NPs produce localized surface plasmon resonance under illumination, which photogenerates electrons and holes able to accelerate the production of hydroxyl radicals when in contact with H2O2. The intermediate morphology sample presents the best activity, doubling the PNP degradation compared to the irradiated experiment with H2O2 alone. This better result can be attributed to the small size of the NPs (30 nm) but also to the presence of more defects in this intermediate structure that allows a longer lifetime of the photogenerated species. Recycling experiments on the best photocatalyst sample showed a constant activity of up to 40 h of illumination for a very low concentration of photocatalyst compared to the literature.

Contrasting water quality in response to long-term nitrogen fertilization in rainfed and irrigated apple-producing regions on China’s Loess Plateau

Overfertilization prevails in developing apple-producing countries, but its long-term effects on regional water resources are scarcely documented. In this study, a total of 114 water samples, including groundwater, river water, and tap water, were collected from rainfed and irrigated apple-planting regions on China’s Loess Plateau. The primary objectives were to (1) systematically evaluate changes in hydrochemistry using hydrochemical indices and major ion ratios, (2) quantify NO3−-N pollution and its driving factors using δ15N- and δ18O-labeled nitrate and a Bayesian isotope mixing model (MixSIAR), and (3) identify water suitable for drinking using an entropy water quality index and for irrigation by integrating electrical conductivity and Na%. All water samples contained Ca-Mg-HCO3 facies, except for low-elevation water samples in the irrigated region with Na-HCO3 facies. Hydrochemistry changed considerably from the 2000–2020 s in both rainfed and irrigated regions, primarily associated with agricultural activities (e.g., fertilization). Although absent in the rainfed region, NO3−-N pollution was severe in the irrigated region, with 40.0 % of tap water, 25.0 % of river water, and 32.7 % of groundwater samples exceeding the World Health Organization limit of 10 mg L−1. MixSIAR indicated the contribution of chemical fertilizer to NO3− was higher in irrigated than in rainfed regions, regardless of the water source. With the exception of sewage/manure-derived NO3–-N in the rainfed region’s groundwater, chemical fertilizer was the highest contributor to NO3−-N in river water and groundwater, whereas sewage/manure was the most important nitrate source in tap water, whether irrigated or rainfed region. Regression analysis revealed N-fertilizer inputs and water level and well depths were key factors affecting groundwater NO3−-N in the irrigated region compared with those in the rainfed region. Notably, all water samples in the rainfed region were suitable for drinking and irrigation, whereas in the irrigated region, 27.3 % of groundwater samples were unsuitable for drinking and 40.0 % of tap water, 75.0 % of river water, and 63.6 % of groundwater samples were doubtful-to-unsuitable for irrigation. Collectively, overfertilization in long-term apple cultivation changed regional hydrochemistry, with flood irrigation aggravating nitrate pollution and water degradation. The study provides new insights into optimum water–nitrogen management of apple production systems in China and other developing countries with similar problems.