Agricultural Runoff Water Research Articles

A Theoretical Study on Doped-NiOOH Catalysts for Enhanced Urea Oxidation Reaction

Urea is a common waste specie in agricultural runoff water and has been considered as a promising oxidizable molecule for substitution of oxygen evolution reaction (OER) to save energy. However, the overpotential of electrochemical urea oxidation reaction (UOR) is still high due to the complicated six-electron transfer process on most metal catalysts and the competition with OER further limits catalyst options for UOR. The most promising and studied catalysts for UOR are Ni-based catalysts. Previous theoretical and experimental research works have focused on NiOOH step-edges as active sites for UOR. In this work, we focus on gaining atomic-level insight into the role of basal-type sites in UOR, which represent the largest surface area of NiOOH catalysts. We study the effects of vacancies as well as metal doping on the transformation from Ni(OH)2 to NiOOH active phase and the UOR pathway using density functional theory (DFT) calculations. By investigating various Ni(OH)2 and NiOOH (001) surfaces with vacancies and dopants such as Fe, Co and Cu, we are able to examine how the active sites influence the Ni-catalysts transformation and the urea oxidation. This work sheds light on the structure-property relationship of Ni(OH)2/NiOOH in urea oxidation and offers design principles for functional Ni-based materials, which will help accelerate the development of efficient UOR catalysts.

Assessment of seasonal fluctuation in heavy metal contamination in sediments and surface water of Narmada River, India

ABSTRACT This study aimed to assess the seasonal fluctuation of heavy metal contamination in the sediments and surface water of the Narmada River. In this context, samples were gathered from six stations along the river in 2021–2022 and their concentrations were determined by utilizing Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The results in sediments, the average concentrations of As, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were 0.05, 1.03, 2.47, 1.64, 750.17, 17.75, 0.54, 0.13, and 1.12 mg/kg and in water, the average concentrations of Co, Fe, Ni, and Zn were 0.03 μg/l, 0.01 mg/l, 0.08 μg/l, and 0.39 μg/l. Seasonal fluctuation in sediments revealed that concentration of metals As, Cu, Fe, Ni, and Zn peaked during the rainy climate, while Co and Cr peaked during the post-monsoon and Mn and Pb peaked during the summer climate. Seasonal fluctuation in water, Co, Ni, and Zn exhibits their highest concentrations during the post-monsoon. The finding of pollution indices revealed that the contamination level was low to moderate. Cluster analysis revealed anthropogenic and agricultural runoff water as a contributor to contamination. The findings of this research enhance comprehension of heavy metal contamination in sediment and water of the Narmada River.

Efficient adsorptive removal of 2,4-dichlorophenoxyacetic acid (2,4-D) using biomass derived magnetic activated carbon nanocomposite in synthetic and simulated agricultural runoff water

This study focused on evaluating the efficacy of a magnetic activated carbon material (CPAC@Fe3O4) derived from pods of copper pod tree in adsorbing the toxic herbicide, 2,4- (2,4-D) from aqueous solutions. The synthesized CPAC@Fe3O4 adsorbent, underwent various characterization techniques. FESEM images indicated a rough surface, incorporating iron oxide nanoparticles, while EDS analysis confirmed the presence of elements like Fe, O, and C. Notably, the CPAC@Fe3O4 exhibited high surface area (749.10 m2/g) and pore volume (0.5351 cm³/g), confirming its mesoporous nature. XRD investigations identified distinct signals associated with graphitic carbon and magnetite nanoparticles, while VSM analysis verified its magnetic properties with a high magnetic saturation value (2.72 emu/g). The adsorption process was exothermic, with a decrease in adsorption capacity at higher temperatures. Freundlich isotherm provided the best fit for the adsorption, and the pseudo-second-order equation effectively described the kinetics. Remarkably, the maximum adsorption capacity ranged from 246.43 to 261.03 mg/g, surpassing previously reported values. The ΔH° value (−8.67 kJ/mol) suggested a physisorption mechanism, and the negative ΔG° values established the spontaneous nature. Furthermore, the synthesized adsorbent demonstrated exceptional reusability, allowing for up to five cycles of adsorption-desorption operations. When applied to simulated agricultural runoff, CPAC@Fe3O4 showcased a significant adsorption capacity of 160.71 mg/g for 50 mg/L 2,4-D, using a 0.2 g/L dosage at pH 2. This study showcased the transformation of copper pod biomass into a valuable magnetic nanoadsorbent capable of efficiently eliminating the noxious 2,4-D pollutant from aqueous environments.

Hydrochar Derived from Sewage Sludge and Water Hyacinth and Its Characterization

Population and urbanization increase the sewage generation. Sewage treatment plant (STP) generates the sewage sludge. Agricultural runoff and sewage water discharge into water bodies proliferates the growth of water hyacinth and creates environmental issues. Managing the sewage sludge and water hyacinth are difficult task because of high water content, environmental concerns, regulatory measures and high operational cost. Hydrothermal carbonization (HTC) converts the wet biomass into condensed solid product called hydrochar at moderate temperature range of 180 – 250°C under auto generated pressure. Through HTC process, the sewage sludge and water hyacinth were mixed and converted into hydrochar @ temperature of 200℃ and 4h resident time with L/S ratio of 9:1. The produced hydrochar showed desired functional groups viz., CH – methyl groups, C-O-C – alcohol groups, esters, ethers and Oxygenic functional groups (-C=O, -OH, -CO-O, C-O-C) with particle size of 494.8 nm, BET surface area of 369.70 m2 g-1, Zeta Potential of -27.9 mV. The hydrochar recorded slightly acidic pH (5.8) with appreciable levels of C (24.4%), N (2.51%), P (0.44%), K (0.98%), Ca (1.24%), Mg (0.68%). These properties of sewage sludge and water hyacinth derived hydrochar exhibits its potential use in agricultural and environmental applications.

Pharmaceutical Attenuation Differs within Woodchip-Based Lignocellulose Bioreactors across Nitrate- and Sulfate-Reducing Conditions

Lignocellulosic bioreactors use solid-phase substrates such as woodchips to sustain microbial respiration and have been applied to treat agricultural runoff, stormwater, and other impaired waters. Here, we query how respiration of different soluble electron acceptors impacts the degradation of environmentally relevant pharmaceuticals associated with treated municipal wastewater discharge. Laboratory-scale columns containing a mixture of woodchips and alfalfa were manipulated across nitrate- and sulfate-reducing conditions using residence time and influent composition. Under steady-state conditions, bioreactors dominated by nitrate reduction harbored a distinct phylogenetic profile containing the genera Denitratisoma and increases in the denitrification gene nirS. In contrast, bioreactors where sulfate reduction dominated exhibited increased relative abundance of fermenters (e.g., Obscuribacteriales) and putative sulfate reducers (e.g., Desulfobulbus). Atenolol attenuation and biotransformation to carboxy-metoprolol accelerated under nitrate-reducing conditions; in contrast, trimethoprim attenuation and biotransformation to desmethyl trimethoprim was nearly an order of magnitude faster under sulfate-reducing conditions. Modest sulfamethoxazole attenuation occurred under all tested conditions. Denitrification-associated rate constants for atenolol were comparable to those reported in constructed wetlands and aquifer recharge, suggesting commonality in biotransformation mechanisms. Collectively, results suggest that manipulation of biogeochemical gradients during nature-based treatment can be applied to attenuate nitrate and trace quantities of pharmaceuticals.

Modelling the removal of nitrogen and sediment by a constructed wetland system in north Queensland, Australia

This study of a multi-component 2.5 ha constructed wetland system near Mackay, north Queensland was established to determine the efficacy of these types of wetlands for improving water quality entering the Great Barrier Reef lagoon. To do this a water balance model was developed using water depth measurements made in the wetland inlet basin, between 25 December 2018 and 30 September 2020. The water balance model allowed daily values of run-in and drainage to be calculated, which were combined with a nitrogen balance model to derive a value for the amount of total nitrogen (TN) removed by the wetland of 83 kg ha−1 year−1, or 37% of the nitrogen input to the wetland. The nitrogen balance model used a mean inflow TN concentration of 5060 (± 1734) μg L−1 derived from TN concentration measurements (automatic and grab) made during four high flow events. The largest losses of nitrogen where via drainage with 49% leaving as outflow and 14% as groundwater seepage. Outflow carried 38% of the sediment and particulate nitrogen (PN) out of the wetland, which means that 62% settled to the bottom of the wetland. Dissolved nitrogen (DN) removal in Bakers Creek is mainly (89%) due to the relatively long residence time of water in its biodiversity pond component, the largest and deepest part of this wetland system which always contained water, even during the dry season. This illustrates the value of large, permanent deep pools in a wetland system, whether they are constructed or natural. Wetlands constructed downstream of areas generating sediments and nutrients should therefore be able to improve the quality of water entering the Great Barrier Reef lagoon. However, to do this they need to retain water for significant amounts of time, which they may do in comparatively low rainfall areas. In higher rainfall areas open, flow through wetlands may not be able to do this, so wetlands constructed in these regions need to be designed to retain water in order to have significant N removal capacity. Proper monitoring of future constructed wetlands is vital in order to derive robust design criteria for systems that can remove significant nitrogen from agricultural run-off water.

Determination of urea, phosphate, and potassium in agricultural runoff waters using electrochemical impedance spectroscopy.

Large-scale use of chemical fertilizers has resulted in the contamination of agricultural runoff waters by soil macronutrients NPK, whose detection is of significant interest. This work reports the determination of macronutrients in the form of urea (N), orthophosphate PO43- (P), and potassium K+ (K) in simulated agricultural runoff waters. Their solutions were prepared by extracting water-soluble constituents of soil. This'base' solution contains high concentrations of various species, including Cl-, SO42-, NO3-, PO43-, Na+, K+, and NH4+ along with natural organic matter. Predetermined amounts of urea (4 to 22.5 ppm), PO43- (7 to 50 ppm), and potassium K+ (25 to 250 ppm) were added to the base simulated runoff water to prepare standard stock solutions. Using stainless steel working and counter electrodes, a small AC perturbation (±10 mV vs. OCP, vs. Ag/AgCl) was applied and the frequency response of the working electrode-solution interface was measured from 1 Hz to 1 MHz. The interface itself was modeled as a suitable equivalent electrical circuit, and the magnitudes of its components were fitted from experimental data using nonlinear regression. It is observed that PO43- concentration is a linear function of charge transfer resistance arising from redox reaction, K+ concentration is a quadratic function of double-layer capacitance arising from its higher mobility, and urea concentration can be correlated as a linear function of constant phase element arising from its polarization in the presence of an applied electric field. The sensor exhibits good sensitivity, repeatability, and excellent performance against interfering species. These preliminary results show significant potential for development of a real-time or on-site sensing device.

Ternary metal-organic framework/multi-walled carbon nanotube/iron oxide nanocomposite for removal of butachlor pesticide

BackgroundButachlor (BUT) as an organochlorine pesticide (OCP) that prevents weeds from growing has been used in the agriculture field. It remains in the environment for a long time and causes mutagenicity and cancer.ResultsIn the current study, magnetic multi-walled carbon nanotube with zeolitic imidazolate frameworks-67 (Fe3O4–MWCNT–ZIF67) was used as adsorbent to remove BUT from the aqueous solution. The characteristics and the chemical composition of the adsorbent were evaluated using FE-SEM, TEM, MAP, EDX, FTIR, BET, TGA and VSM. The response surface methodology (RSM) as a method for the design of experiment was applied to optimize variables such as the initial concentration of BUT, adsorbent dosage, contact time and temperature in the batch experiment by central composite design (CCD). The optimum adsorption condition predicted by RSM was pH = 4.5, initial concentration = 5.75 ppm, dosage = 0.07 g and contact time = 95 min. The results showed that maximum removal efficiency for the butachlor is 86%.ConclusionsDifferent adsorption isotherms were evaluated using adsorption equilibrium data and results showed that Temkin model has the best compatibility with the experimental data. In addition, the adsorption kinetics data were closer with pseudo-second-order model. Thermodynamic study showed that the adsorption process was spontaneous, endothermic and physical. This composite can be effectively used for the remediation/clean-up of groundwater and agricultural run-off water which are contaminated with harmful pesticides.Graphical

Molecular characterization of dissolved organic nitrogen and phosphorus in agricultural runoff and surface waters

Agricultural runoff is a significant contributor to nitrogen (N) and phosphorus (P) pollution in water bodies. Limited information is available about the molecular characteristics of the dissolved organic N (DON) and P (DOP) species in the agricultural runoff and surface waters. We employed Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry (FT-ICR-MS) to investigate the changes in the molecular characteristics of DON and DOP at three watershed positions (upstream water, runoff from agricultural fields, and downstream waters). Across three watershed locations, more-bioavailable compounds (such as amino sugars, carbohydrates, lipids, and proteins) accounted for <5% of DON and 4–31% of DOP molecules, whereas less-bioavailable compounds (such as lignin, tannins, condensed hydrocarbons, and unsaturated hydrocarbons) were >95% of DON and 69–96% of DOP. Of the dissolved organic matter, runoff waters from agricultural fields contained the greatest proportion of DON formulas (20–25%) than upstream (18%) and downstream (13–14%) waters, indicating the presence of a greater diversity of DON species in the runoff. Various nutrient sources present in agricultural fields such as crop residues, soil organic matter, and transformed fertilizers likely contributed to the diverse composition of DON and DOP in the runoff, which were likely altered as the surface water traversed along the flow pathways in the watershed. The presence of more-bioavailable molecules detected in upstream compared to agricultural runoff and downstream waters suggests that photochemical and/or microbial processes likely altered the characteristics of DON and DOP compounds. The findings of this study increase our understanding of DON and DOP compounds lability and transformations in runoff and surface waters , which may be useful in quantifying the contribution of organic N and P sources to water quality impairment in aquatic ecosystems.

Endocrine disrupting chemicals (EDCs) in environmental matrices: Occurrence, fate, health impact, physio-chemical and bioremediation technology

Endocrine disrupting chemicals (EDCs) are an emerging category of toxicity that adversely impacts humans and the environment's well-being. Diseases like cancer, cardiovascular risk, behavioral disorders, autoimmune defects, and reproductive diseases are related to these endocrine disruptors. Because these chemicals exist in known sources such as pharmaceuticals and plasticizers, as well as non-point sources such as agricultural runoff and storm water infiltration, the interactive effects of EDCs are gaining attention. However, the efficiency of conventional treatment methods is not sufficient to fully remediate EDCs from aqueous environments as the occurrence of EDC bioremediation and biodegradation is detected in remediated drinking water. Incorporating modification into current remediation techniques has to overcome challenges such as high energy consumption and health risks resulting from conventional treatment. Hence, the use of advanced psychochemical and biological treatments such as carbon-based adsorption, membrane technology, nanostructured photocatalysts, microbial and enzyme technologies is crucial. Intensifying environmental and health concerns about these mixed contaminants are primarily due to the lack of laws about acute concentration limits of these EDCs in municipal wastewater, groundwater, surface water, and drinking water. This review article offers evidence of fragmentary available data for the source, fate, toxicity, ecological and human health impact, remediation techniques, and mechanisms during EDC removal, and supports the need for further data to address the risks associated with the presence of EDCs in the environment. The reviews also provide comprehensive data for biodegradation of EDCs by using microbes such as fungi, bacteria, yeast, filamentous fungi, and their extracellular enzymes.

The Historical Development of Constructed Wetlands for Wastewater Treatment

Constructed wetlands (CWs) for wastewater treatment are engineered systems that are designed and operated in order to use all natural processes involved in the removal of pollutants from wastewaters. CWs are designed to take advantage of many of the same processes that occur in natural wetlands, but do so within a more controlled environment. The basic classification is based on the presence/absence of wastewater on the wetland surface. The subsurface flow of CWs can be classified according to the direction of the flow to horizontal and vertical. The combination of various types of CWs is called hybrid CW. The CWs technology began in the 1950s in Germany, but the major extension across the world occurred during the 1990s and early 2000s. The early CWs in Germany were designed as hybrid CWs; however, during the 1970s and 1980s, horizontal subsurface flow CWs were mostly designed. The stricter limits for nitrogen, and especially ammonia, applied in Europe during the 1990s, brought more attention to vertical subsurface flow and hybrid systems. Constructed wetlands have been used to treat various types of wastewater, including sewage, industrial and agricultural wastewaters, various drainage and runoff waters and landfill leachate. Recently, more attention has also been paid to constructed treatment wetlands as part of a circular economy in the urban environments: it is clear that CWs are a good fit for the new concept of sponge cities.

Sizing an open-channel woodchip bioreactor to treat nitrate from agricultural tile drainage and achieve water quality targets

Abstract Woodchip bioreactors are capable of removing nitrate from agricultural runoff and subsurface tile drain water, alleviating human health hazards and harmful discharge to the environment. Water pumped from agricultural tile drain sumps to nearby ditches or channels could be cost-effectively diverted through a woodchip bioreactor to remove nitrate prior to discharge into local waterways. Sizing the bioreactor to achieve targeted outlet concentrations within a minimum footprint is important to minimizing cost. Determining the necessary bioreactor size should involve a hydrological component as well as reaction type and rates. We measured inflow and outflow nitrate concentrations in a pumped open-channel woodchip bioreactor over a 13-month period and used a tanks-in-series approach to model hydrology and estimate parameter values for reaction kinetics. Both zero-order and first-order reaction kinetics incorporating the Arrhenius equation for temperature dependence were modeled. The zero-order model fit the data better. The rate coefficients (k = 17.5 g N m−3 day−1 and theta = 1.12 against Tref = 20 °C) can be used for estimating the size of a woodchip bioreactor to treat nitrate in agricultural runoff from farm blocks on California's central coast. We present an Excel model for our tanks-in-series hydrology to aid in estimating bioreactor size.

A Review on Constructed Treatment Wetlands for Removal of Pollutants in the Agricultural Runoff

Constructed wetland (CW) is a popular sustainable best management practice for treating different wastewaters. While there are many articles on the removal of pollutants from different wastewaters, a comprehensive and critical review on the removal of pollutants other than nutrients that occur in agricultural field runoff and wastewater from animal facilities, including pesticides, insecticides, veterinary medicine, and antimicrobial-resistant genes are currently unavailable. Consequently, this paper summarized recent findings on the occurrence of such pollutants in the agricultural runoff water, their removal by different wetlands (surface flow, subsurface horizontal flow, subsurface vertical flow, and hybrid), and removal mechanisms, and analyzed the factors that affect the removal. The information is then used to highlight the current research gaps and needs for resilient and sustainable treatment systems. Factors, including contaminant property, aeration, type, and design of CWs, hydraulic parameters, substrate medium, and vegetation, impact the removal performance of the CWs. Hydraulic loading of 10–30 cm/d and hydraulic retention of 6–8 days were found to be optimal for the removal of agricultural pollutants from wetlands. The pollutants in agricultural wastewater, excluding nutrients and sediment, and their treatment utilizing different nature-based solutions, such as wetlands, are understudied, implying the need for more of such studies. This study reinforced the notion that wetlands are effective for treating agricultural wastewater (removal &gt; 90%) but several research questions remain unanswered. More long-term research in the actual field utilizing environmentally relevant concentrations to seek actual impacts of weather, plants, substrates, hydrology, and other design parameters, such as aeration and layout of wetland cells on the removal of pollutants, are needed.

(Invited) H2-Free, Highly-Selective Electrocatalytic Reduction of Nitrates to Ammonia with Solar-to-Ammonia Efficiency >5%

Direct electrochemical reduction of dinitrogen to NH3 is not efficient due to higher mass transfer resistances (owing to lower solubility of N2) and the competing hydrogen evolution reaction (HER). However, electrochemical reduction of NO3 - to NH3 is less challenging than direct N2 reduction to NH3 due to lower dissociation energy of N = O bond (204 kJ/mol) as compared to N ≡ N (941 kJ/mol). Efficient conversion of NO3 - can aid in sustainable metallurgical, agricultural, and water purification applications. For instance, NO3 - is mined directly from saltpeter mines and it is an industrial waste byproduct from metal finishing facilities and uranium purification and processing its byproducts. NO3 - contamination in ground water by the agricultural runoff water is a major problem, whereas its contamination in drinking water can lead to methemoglobinemia in infants and several types of cancers in adults.Here we show theory-guided search of efficient transition metals to identify the most active catalyst for the electrochemical nitrate reduction to NH3. Experimental investigations corroborated with the theoretical findings, leading to the identification of transition metals that yielded highest NH3 Faradaic efficiency (FE). We will also show the effect of morphology and oxidation state of efficient catalyst on NH3 current density and FE. Effect of operating conditions such as pH, concentration of nitrates, and applied potential will be also discussed. A maximum NH3 FE of 68.13 % at -0.6 V vs RHE (pH = 14) and NH3 current density of 245.34 mA/cm2 was observed at -0.8 V vs RHE (pH = 14) with a lowest onset potential of 0.1 V vs RHE. The oxide-derived metal catalyst was found to be stable for the test period of 24 h with an average solar-to-ammonia efficiency of >5%. Control studies were also performed using N-15 nitrates to confirm that the source of NH3 produced.

A modified sensitive palladium-copper oxide and multiwalled carbon nanotubes electrochemical sensor for detection of ametridione pesticide

Glassy carbon electrode modified sensitive Pd-CuO/MWCNTs electrochemical nanosensor was used for detection of ametridione pesticide in water samples. The morphology characteristics of Pd-CuO/MWCNTs are examined by scanning electron microscopy and EDX. The ametridione pesticide under voltammetric investigation involves irreversible, 4e? electron reduction based on the protonation of the two carbonyl groups (&gt;C=O). The voltammetric method was applied for the detection of ametridione in BR buffer solution at pH 5.0 as a supporting electrolyte. The detection limit, limit of quantification and concentration ranges of the proposed method were 0.0796 ?g?mL?1 (signal/noise=3), 0.5560 ?g?mL?1 and 0.1 to 10.0 ?g?mL?1, respectively. The electrochemical sensor was successfully applied for the detection of ametridione in tap, agricultural run-off and river water samples showing &gt;98% mean recoveries.&#x0D; &#x0D;

Removal of nitrate and phosphate from simulated agricultural runoff water by Chlorella vulgaris

Microalgae such Chlorella vulgaris can effectively absorb nitrate and phosphate from contaminated water. This work characterized nitrate and phosphate removal from simulated agricultural runoff using C. vulgaris. Statistically designed experiments were used to model the following responses: (1) algal growth; (2) nitrate removal; (3) phosphate removal; (4) protein in the algal biomass; (5) chlorophyll content of the biomass; (6) the biomass phenolics content; and (7) the free radical scavenging antioxidant activity of the biomass. These response were modelled for the following key experimental factors: initial nitrate concentration in the simulated runoff (1080–3240 mg L−1, as NaNO3), initial phosphate concentration (20–60 mg L−1, as K2HPO4), photoperiod (8–24 h of light/day) and culture duration (5–15 days). The validated models were used to identify the factor levels to maximize the various responses. Nitrate removal was maximized at 85.6% when initial nitrate and phosphate concentrations were 2322 mg L−1 and 38 mg L−1 (N:P atom ratio ≈ 125:1), respectively, with a 17.2 h daily photoperiod in a 13-day culture. Phosphate removal was maximized at 95% when the initial nitrate and phosphate concentrations were 1402 mg L−1 and 56.7 mg L−1 (N:P ≈ 51:1), respectively, with a 15.7 h daily photoperiod in a 14.7-day culture. At least ~14 h of a daily photoperiod and a ~11-day culture period were required to maximize all the studied responses. C. vulgaris is edible and may be used as animal feed. Nutritional aspects of the biomass were characterized. Biomass with more than 24% protein could be produced. Under the best conditions, the chlorophyll (potential food colorants) content of the biomass was 8.5% and the maximum level of total phenolics (antioxidants) in the biomass was nearly 13 mg gallic acid equivalent g−1.

A novel sensitive aptamer-based nanosensor using rGQDs and MWCNTs for rapid detection of diazinon pesticide

An optical apta-nanosensor was designed and developed based on reduced graphene quantum dots (rGQDs) and multi-walled carbon nanotubes (MWCNTs) and applied for the selective detection of diazinon as one of the most widely used organophosphorus pesticides. Considering the GQDs and rGQDs high fluorescence emission and optical stability, efficient optical transducers could be designed and precise detection methods could be developed based on such transducers. Herein, by using rGQDs, diazinon specific aptamer, and MWCNTs, a simple economical fluorescence method has been introduced to detect and measure diazinon with the detection limit of 0.4 nM (0.1 µg/L) in the range of 4–31 nM, meeting the specifications and standards set by the European Union and World Health Organization. To assess apta-nanosensor performance, the real application of the novel apta-nanosensor was then validated by detecting and quantifying diazinon in real samples, including tap water, urine, river water, and agricultural runoff water. The obtained results revealed that, due to the lack of binding affinity for the diazinon specific aptamer, the emission recoveries were kept intact in the presence of other pesticides and thereby, the designed apta-nanosensor was able to promptly detect diazinon pesticide with high accuracy and selectivity in real samples. Accordingly, the accurate apta-nanosensor developed in this study provides a sensitive, inexpensive, fast, and portable device for selective detection of diazinon over other pesticides in contaminated regions. The introduced innovative method could also be applied for other pesticides, providing a practical on-site detection approach for real samples of multi pesticides.

An ultra-sensitive and selective AChE based colorimetric detection of malathion using silver nanoparticle-graphene oxide (Ag-GO) nanocomposite

Herein, we propose rapid, precise acetylcholinesterase (AChE) inhibition-based sensing strategy for malathion detection in the presence of Ag-GO and acetylthiocholine (ATCh). The biosensing method was developed with a nanocomposite of citrate stabilized AgNPs anchored on the GO sheets (Ag-GO). The physical and chemical properties of the prepared Ag-GO composite were analyzed with various characterization techniques, including XRD, FT-IR, XPS, UV–Visible spectroscopy, and HR-TEM. The positively charged thiocholine (TCh) produced by enzyme hydrolysis triggers the AgNPs aggregation on GO sheets, which ultimately decreases the intensity of the corresponding SPR absorption peak. While the addition of malathion into the sensing system hindered the AChE activity and limited the TCh production, and thus inhibits the decrease in the SPR band intensity. The designed sensing system displayed linearity in the broad range of malathion concentrations (0.01 pM–1000 pM) with a limit of detection and the limit of quantification values of 0.01 pM, and 0.035 pM, respectively. The application of the designed biosensing system was extended to determine the malathion in actual samples namely, tap water, agricultural runoff water, lake water, and grape extract, which resulted in almost 100% recovery rates in all the spiked samples.

Efficient Electrochemical Nitrate Reduction to Ammonia Via Electrolyte Engineering

Nitrate-containing fertilizers are prolific in the agricultural industry due to the ease with which nitrates can be used as a nutrient source by plants.1 Concentrated forms of nitrates can be found in industrial waste streams such as those originating from uranium purification and processing,2 saltpeter mines,3 and agricultural runoff water.4 These nitrates often appear in the form of cation-containing salts, which can themselves be used as fertilizers. However, nitrate salts are generally avoided due to possible buildup of cations in the soil. Accumulation of ions such as sodium and calcium can break down soil structure, affect water intake by plants, and decrease plant metabolism, all of which lower crop yield.1 Consequently, a technology with the ability to convert various nitrate sources to a form of fertilizer that is less detrimental to crop growth is desirable. Direct electrochemical conversion of nitrates to ammonia is attractive due to its feasibility under a wide variety of electrolyte conditions, as well as its potential to be coupled to renewable electricity sources. While many studies have focused on electrochemical reduction of nitrates to environmentally-benign N2,5-7 recycling these nitrates into a chemical commodity such as ammonia could provide a means of producing a valuable fertilizer, ammonium nitrate, that is less potentially harmful to crop health than mineral- and metal-containing nitrate salts. To this end, a titanium-based cathode was used to electrochemically reduce NO3 - to ammonia. Applied potential, electrolyte pH, and nitrate concentration were varied to map selectivity toward ammonia under a variety of electrode/electrolyte conditions. Selectivity varied depending on proton and nitrate anion availability, with a maximum Faradaic efficiency (FE) toward NH3 of 78% occurring at a pH of 1 and 0.4 M NO3 - under an applied potential of -1 V vs RHE and current density of 23 mA/cm2. We observed titanium hydride formation on the surface of the electrode during electrolysis experiments and found that pre-treating the cathode may improve FE toward NH3. Additionally, the cathode was stable over 8 hours and demonstrated 50% FE toward ammonia, suggesting titanium is reasonably stable under peak selectivity conditions. Our preliminary technoeconomic analysis suggests that, at our total cell voltage of 1 V and the above selectivity toward ammonia, there may be an opportunity to produce ammonium nitrate, a typical fertilizer product, at or below the USDA cost range of NH4NO3. References Day, A. D.; Ludeke, K. L., Soil Alkalinity. In Plant Nutrients in Desert Environments, Springer Berlin Heidelberg: Berlin, Heidelberg, 1993; pp 35-37.Holleman, A. F.; Wiberg, E.; Wiberg, N.; Eagleson, M.; Brewer, W., Inorganic Chemistry. Academic Press: 2001.Gustafson, A. F., Handbook of Fertilizers - Their Sources, Make-Up, Effects, And Use. Read Books Limited: 2013.Davidson, E. A.; David, M. B.; Galloway, J. N.; Goodale, C. L.; Haeuber, R.; Harrison, J. A.; Howarth, R. W.; Jaynes, D. B.; Lowrance, R. R.; Nolan, B. T.; Peel, J. L.; Pinder, R. W.; Porter, E.; Snyder, C. S.; Townsend, A. R.; Ward, M. H., Excess Nitrogen in the U.S. Environment: Trends, Risks, and Solutions. Issues in Ecology 2012, 12, 1-1.Katsounaros, I.; Kyriacou, G., Influence of the concentration and the nature of the supporting electrolyte on the electrochemical reduction of nitrate on tin cathode. Electrochimica Acta 2007, 52 (23), 6412-6420.Dortsiou, M.; Katsounaros, I.; Polatides, C.; Kyriacou, G., Influence of the electrode and the pH on the rate and the product distribution of the electrochemical removal of nitrate. Environmental Technology 2013, 34 (3), 373-38.Dima, G. E.; de Vooys, A. C. A.; Koper, M. T. M., Electrocatalytic reduction of nitrate at low concentration on coinage and transition-metal electrodes in acid solutions. J Electroanal Chem 2003, 554-555, 15-23. Figure 1

Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland

A surface flow constructed wetland (CW) was set in the Lerma gully to decrease nitrate (NO3−) pollution from agricultural runoff water. The water flow rate and NO3− concentration were monitored at the inlet and the outlet, and sampling campaigns were performed which consisted of collecting six water samples along the CW flow line. After two years of operation, the NO3− attenuation was limited at a flow rate of ~2.5 L/s and became negligible at ~5.5 L/s. The present work aimed to assess the feasibility of using rural waste products (wheat hay, corn stubble, and animal compost) to induce denitrification in the CW, to assess the effect of temperature on this process, and to trace the efficiency of the treatment by using isotopic tools. In the first stage, microcosm experiments were performed. Afterwards, the selected waste material was applied in the CW, and the treatment efficiency was evaluated by means of a chemical and isotopic characterization and using the isotopic fractionation (ε) values calculated from laboratory experiments to avoid field-scale interference. The microcosms results showed that the stubble was the most appropriate material for application in the CW, but the denitrification rate was found to decrease with temperature. In the CW, biostimulation in autumn-winter promoted NO3− attenuation between two weeks and one month (a reduction in NO3− between 1.2 and 1.5 mM was achieved). After the biostimulation in spring-summer, the attenuation was maintained for approximately three months (NO3− reduction between 0.1 and 1.5 mM). The ε15NNO3/N2 and ε18ONO3/N2 values obtained from the laboratory experiments allowed to estimate the induced denitrification percentage. At an approximate average flow rate of 16 L/s, at least 60% of NO3− attenuation was achieved in the CW. The field samples exhibited a slope of 1.0 for δ18O-NO3− versus δ15N-NO3−, similar to those of the laboratory experiments (0.9–1.2). Plant uptake seemed to play a minor role in NO3− attenuation in the CW. Hence, the application of stubble in the CW allowed the removal of large amounts of NO3− from the Lerma gully, especially when applied during the warm months, but its efficacy was limited to a short time period (up to three months).