Bentazon Concentration Research Articles

Exploring long-term retention and reactivation of micropollutant biodegradation capacity

The factors limiting micropollutant biodegradation in the environment and how to stimulate this process have often been investigated. However, little information is available on the capacity of microbial communities to retain micropollutant biodegradation capacity in the absence of micropollutants or to reactivate micropollutant biodegradation in systems with fluctuating micropollutant concentrations. This study investigated how a period of 2 months without the addition of micropollutants and other organic carbon affected micropollutant biodegradation by a micropollutant-degrading microbial community. Stimulation of micropollutant biodegradation was performed by adding different types of dissolved organic carbon (DOC)—extracted from natural sources and acetate—increasing 10 × the micropollutant concentration, and inoculating with activated sludge. The results show that the capacity to biodegrade 3 micropollutants was permanently lost. However, the biodegradation activity of 2,4-D, antipyrine, chloridazon, and its metabolites restarted when these micropollutants were re-added to the community. Threshold concentrations similar to those obtained before the period of no substrate addition were achieved, but biodegradation rates were lower for some compounds. Through the addition of high acetate concentrations (108 mg-C/L), gabapentin biodegradation activity was regained, but 2,4-D biodegradation capacity was lost. An increase of bentazon concentration from 50 to 500 µg/L was necessary for biodegradation to be reactivated. These results provide initial insights into the longevity of micropollutant biodegradation capacity in the absence of the substance and strategies for reactivating micropollutant biodegrading communities.Graphical abstract

Bentonite nanoparticles-incorporated ZnO nanofiber mats assembly by electro-centrifuge spinning for efficient photo-degradation of bentazon herbicide: Tuning composition and process optimization

Herein, photocatalytic features and performance of ZnO nanofiber mats spun by electro and electro-centrifuge spinning methods were evaluated by various characterization techniques and the UV-degradation of bentazon herbicide, respectively and then, compared with those of ZnO nanoparticles. Because of higher productivity and more flexibility in loading nanoparticles, the electro-centrifuge spinning method was chosen to fabricate bentonite nanoparticles incorporated ZnO nanofiber mats. The FESEM images clearly indicate the formation of 0D/1D nanoparticle/nanofiber morphologies in samples. XRD, EDX and FTIR analyses confirmed the formation of ZnO and the existence of bentonite. Based on the PL analysis, the bentonite nanoparticles get to inhibit the charge recombination. However, its excessive incorporation causes intense loss of active sites numbers and the surface coverage of ZnO nanofibers which restrict the light absorption as evidenced by FESEM and UV-DRS results. After 2 h irradiation, the efficiency removal of bentazon reached from 85.23% by pure ZnO nanofibers to 100% by composite nanofiber mats containing 5 wt% bentonite (ZnO-Ben5 (NF-ECS)). Nonetheless, the removal efficiency declines upon further increasing the content of incorporated bentonite. The kinetics study disclosed that the photocatalytic bentazon removal was best fitted with the first order model (R2 = 0.9907) with the maximum rate constant of 0.0243 min−1 over ZnO-Ben5 (NF-ECS). Moreover, RSM-CCD analysis was employed to model and optimize the photocatalytic treatment process. A reduced cubic model (Adj. R2 = 0.9934, p-value <0.0001) was proposed for interpreting the system behavior. Under optimal operating conditions (photocatalyst dosage of 0.33 g.L−1, initial solution pH of 8.92, bentazon concentration of 10.11 ppm and irradiation time of 85.78 min), ZnO-Ben5 (NF-ECS) eliminated approximately 83% of bentazon after four-time recycling, reflecting a sustained great activity.

Modeling of Bentazone Leaching in Soils with Low Organic Matter Content.

The aim of this study was to estimate bentazone’s potential to leach to groundwater in the Arenosols developed from sand, Luvisols developed from loamy sand or sandy loam, and Luvisols or Cambisols developed from loess, and to identify the major factors influencing bentazone’s fate in the soils. Potato and maize cultivations were simulated using the FOCUS PELMO 5.5.3 pesticide leaching model. The amount of bentazone reaching groundwater was highly sensitive to degradation parameters, water-holding capacity, evapotranspiration, organic carbon content, and pH. The highest bentazone concentrations in percolate were noted in Arenosols. The risk of bentazone concentration exceeding 0.1 μg/L was low only in Arenosols with high organic carbon content (3.0% for topsoil or higher). In Luvisols developed from loamy sand or sandy loam, the estimated bentazone concentrations in percolate were highly dependent on the climate. In Luvisols or Cambisols developed from loess, concentrations of >0.1 μg/L were the least likely due to the high water-holding capacity and high organic carbon content of these soils. The study also revealed that the FOCUS Hamburg scenario, representing the coarsest soils in the European Union with relatively low organic carbon content, does not reflect the leaching potential of Arenosols and Luvisols.

Neuro-hepatopathological changes in juvenile Oreochromis niloticus exposed to sublethal concentrations of commercial herbicides

The current study estimates the impact of different common herbicides on antioxidant defenses and histological structure of liver and spinal cord of juvenile tilapia. Eighty-four fish were divided into seven groups: group 1 fish acted as controls and the remaining fish were exposed to sublethal concentrations of acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, or quinclorac at sublethal concentrations 2.625, 0.800, 36.00, 2.50, 1.275, and 11.250 mg/l, respectively, for 96 h. Antioxidant parameters changed in response to some test herbicides and the greatest effects were caused by exposure to acetochlor and quinelorac for all antioxidant measurements. Prominent histological changes in liver tissue included loss of liver architecture and the appearance of fatty liver cells, necrotic areas, foci of leukocytic infiltration and many apoptotic cells. The most obvious changes in the spinal cord in all treated fish were degradation of myelinated white matter fibers with the emergence of empty spaces, large aggregation of pyknotic neuroglial nuclei, and damaged areas in the dorsal horn of gray matter. Collectively, the harmful effect of tested herbicides on antioxidant capacity and significant alterations in histological structures of liver and spinal cord of Oreochromis niloticus.

Photocatalytic removal of bentazon by copper doped zinc oxide nanorods: Reaction pathways and toxicity studies

In this study, bentazon herbicide was degraded photocatalytically by copper doped zinc oxide nanorods fabricated by using a facile co-precipitation method. The crystal structure, morphology, surface composition, functional groups on the surface and valence state of the nanorods were investigated by XRD, SEM-EDX, FTIR, and XPS material characterization techniques. Environmental parameters including solution pH, catalyst dose, bentazon concentration, purging gases, H2O2 content, organic compound type and reusability affecting the rate of photocatalytic degradation of bentazon were evaluated. Under the optimal conditions, [Bentazon]0 = 20 mg L−1, Cu–ZnO loading = 0.5 g L−1, H2O2 = 2 mM, pH = 7 and in the presence of oxygen gas, 100% of the herbicide was removed within 60 min. By raising bentazon concentration (10–50 mg L−1), kobs decreased to values between 0.14 and 0.006 min−1 and the calculated electrical energy per order (EEo) increased from 38.16 to 727.27 (kWh m−3), respectively. The degradation removal of the herbicide using the UV/Cu–ZnO method (98.28%) was higher than that of the UV/ZnO method (32.14%) process. Interestingly, the photocatalytic performances in the first and fifth reuse cycles during catalyst recyclability tests were found to be similar. Generally, the efficacy of the method in the decomposition of bentazon in drinking water (78.95%) and actual sewage (46.77%) declined because of the presence of other anions due to their role as a scavenger of photogenerated reactive species. Intermediate products in the photocatalytic degradation of bentazon identified by gas chromatography/mass spectrometry (GC/MS) analysis were 2-amino-N-isopropyl-benzamide, 2-amino-benzoic acid, N-isopropyl-2-nitro-benzamide, and acids such as pentenedioic acid, oxalic acid and propenoic acid. Furthermore, the main mechanism for the photocatalytic removal of bentazon was determined to be via attack by hydroxyl radicals (•OH). The results of toxicity in the photocatalytic removal of bentazon by D. magna showed LC50 and toxicity unit (TU) 48 h equal to 46.10 and 9.56 vol percent.

Biomarkers of exposure and effect in the armoured catfish Hoplosternum littorale during a rice production cycle

Fish cultivation in rice fields is a valuable resource in some rural areas of the world. Fish is a source of protein and an additional source of income for local farmers. However, the use of pesticides may impact fish and consumer health. The aim of this study was to evaluate exposure and effect biomarkers in native fish inhabiting a rice field during a production cycle. Samples of fish, water and sediment from a rice field in Santa Fe, Argentina were collected during a cultivation season (at the beginning: November 2017, in the middle: December 2017 and at the end: February 2018). At each sampling period, fish biomarkers of effect (biometric indices, hematological parameters, energy reserves, oxidative stress and neurotoxicity) were assessed together with pesticide screening in water, sediment, and fish samples. Only herbicides were present in water and sediment samples in agreement with land treatment before rice sowing stage, where only herbicides were applied. In general, the greatest water concentrations of bentazone, glyphosate and aminomethylphosphonic acid (AMPA), and the lowest sediment glyphosate and AMPA levels were observed at the beginning of the farming cycle. Fish bioaccumulated AMPA residues at all sampling periods and showed biological responses to cope with a stressful environment. Alterations in hematological parameters, mobilization of energetic reserves and activation of the antioxidant system were detected. However, no oxidative damage nor neurotoxic effects were present along the production cycle. Under a real exposure scenario, the present work demonstrates that biological changes are induced in fish to cope with stressors present in a rice field. Fish-rice coculture is an efficient and ecologically sustainable approach to increase food supplies, and a better understanding of the effect of this particular environment on fish would allow a greater and safer development of this promising productive activity in South American rice producing countries.

Preparation and Characterization of ZnO & TiO2 Nanocatalysts For Photo Degradation of Bentazon existing in Polluted water

One of the most important scientific research activities in both of energy and environmental sectors is synthesizing of composites such as nanocatalyst powders of zinc oxide and titanium oxide. The reason why is the best to use this combination of composites, as they are available in the market, with low cost, they have powerful optical,electric properties, high stability, and nontoxicity,these composites are classified as one of the best promising photocatalysts. They show high level of light absorption range and wide range of charge transfer from ZnO to TiO2 their composite has a superior photocatalytic activity. The goal of this investigation is to prove the applicability of ZnO–TiO2 composite as a photocatalyst for degradation of Bentazon in polluted water. Many various parameters will be studied, to see their effects on the process of the degradation of the Bentazon, examples of that are the initial catalyst dosage, pH level, initial Bentazon concentration, purging of oxygen gas, adding of hydrogen peroxide of a multiple concentration and total organic compounds on the removal efficiency of Bentazon.The best guaranteed removal of Bentazon is at neutral pH,and the reason for that could be due to the photo-corrosion of ZnO composite for both acidic and basic conditions. While it is noticeable that degradation of the Bentazon decreased in the presence of organic compounds. Removing the Bentazon by UV/ZnO/TiO2 process shows greater Efficiency than that by UV/TiO2 process, UV/ZnO, and UV alone.

Electrochemical Detection of the Pesticide Bentazone Using Shadow-Printed Carbon Electrodes

Pesticides are intensively used in agriculture to increase yield in food production by protecting crops from damaging organisms or competing plants [1]. Although pesticides have helped us meet the growing food demand, the use of pesticides has led to contamination of water resources from which we obtain our drinking water[2]. Bentazone is one of the widely used pesticides for control of crop quality. The compound is highly soluble in water, very mobile in soil and has a tendency to leach from the field into groundwater and surface water. Consequently, the water resources often have bentazone concentrations above the European regulation limit of 0.1 µg/L (0.39 nM)[3]. Monitoring of bentazone in water resources is obligatory. However, due to the complexity of the manual sampling, transport of samples and the need for centralized laboratories to conduct chromatographic analyses of the water, the monitoring is only conducted a few times a year[4]. This means that high concentrations of bentazone in the water may slip in between the samplings and reach the consumers through the water taps[5]. Here we present a simple electrochemical bentazone detection technique that has the potential of being deployed directly in water wells for the continuous monitoring of the water quality. The technique is based on electrochemical measurements using electrodes shadow-printed on a capton substrate. The electrodes consist of carbon and the resulting sensors have been proven to be robust and generate stable signals for at least 25 measurements[6]. We have used the sensors to achieve the selective detection of bentazone in phosphate buffer as the supporting electrolyte. Square wave voltammetry was used to selectively identify bentazone at 0.77 V. A calibration curve for the compound was obtained in the linear range between 0.190 – 50 µM and with a limit of detection of 0.063 µM at pH 7.0. Several other relevant compounds with chemical structures close to bentazone were tested to determine the risk of signal interference. We could demonstrate that the detection method is selective to bentazone, and other similar compounds did not change the target signal. Furthermore, we have spiked lake water and groundwater with bentazone to test the method on real water samples. It was possible to selectively quantify bentazone in the respective waters, despite any unknown chemicals in the samples. The availability of portable potentiostats offer the possibility of on-site detection of bentazone in the fields[7]. The low-cost shadow-printed sensors allow single-use of the sensors for monitoring water resources. Although the method has still not reached the regulation limit, this study is a proof-of-concept showing the possibility of conducting simple, on-site determination of pesticides in water resources.

Evidence of co-metabolic bentazone transformation by methanotrophic enrichment from a groundwater-fed rapid sand filter

The herbicide bentazone is recalcitrant in aquifers and is therefore frequently detected in wells used for drinking water production. However, bentazone degradation has been observed in filter sand from a rapid sand filter at a waterworks with methane-rich groundwater. Here, the association between methane oxidation and removal of bentazone was investigated with a methanotrophic enrichment culture derived from methane-fed column reactors inoculated with that filter sand. Several independent lines of evidence obtained from microcosm experiments with the methanotrophic enrichment culture, tap water and bentazone at concentrations below 2 mg/L showed methanotrophic co-metabolic bentazone transformation: The culture removed 53% of the bentazone in 21 days in presence of 5 mg/L of methane, while only 31% was removed in absence of methane. Addition of acetylene inhibited methane oxidation and stopped bentazone removal. The presence of bentazone partly inhibited methane oxidation since the methane consumption rate was significantly lower at high (1 mg/L) than at low (1 μg/L) bentazone concentrations. The transformation yield of methane relative to bentazone normalized by their concentration ratio ranged from 58 to 158, well within the range for methanotrophic co-metabolic degradation of trace contaminants calculated from the literature, with normalized substrate preferences varying from 3 to 400. High-resolution mass spectrometry revealed formation of the transformation products (TPs) 6-OH, 8-OH, isopropyl-OH and di-OH-bentazone, with higher abundances of all TPs in the presence of methane. Overall, we found a suite of evidence all showing that bentazone was co-metabolically transformed to hydroxy-bentazone by a methanotrophic culture enriched from a rapid sand filter at a waterworks.

Adsorption of bentazon on CAT and CARBOPAL activated carbon: Experimental and computational study

Abstract Removal of the bentazon by adsorption on two different types of activated carbon was investigated under various experimental conditions.Kinetics of adsorption is followed and the adsorption isotherms of the pesticide are determined. The effects of the changes in pH, ionic strength and temperature are analyzed. Computational simulation was employed to analyze the geometry and the energy of pesticide absorption on activated carbon. Concentration of bentazon decreases while increase all the variables, from the same initial concentration. Experimental data for equilibrium was analyzed by three models: Langmuir, Freundlich and Guggenheim–Anderson–de Boer isotherms. Pseudo-first and pseudo-second-order kinetics are tested with the experimental data, and pseudo-second-order kinetics was the best for the adsorption of bentazon by CAT and CARBOPAL with coefficients of correlation R2 = 0.9996 and R2 = 0.9993, respectively. The results indicated that both CAT and CARBOPAL are very effective for the adsorption of bentazon from aqueous solutions, but CAT carbon has the greater capacity.

Factors controlling spatial and temporal patterns of multiple pesticide compounds in groundwater (Hesbaye chalk aquifer, Belgium)

Factors governing spatial and temporal patterns of pesticide compounds (pesticides and metabolites) concentrations in chalk aquifers remain unclear due to complex flow processes and multiple sources. To uncover which factors govern pesticide compound concentrations in a chalk aquifer, we develop a methodology based on time series analyses, uni- and multivariate statistics accounting for concentrations below detection limits. The methodology is applied to long records (1996–2013) of a restricted compound (bentazone), three banned compounds (atrazine, diuron and simazine) and two metabolites (deethylatrazine (DEA) and 2,6-dichlorobenzamide (BAM)) sampled in the Hesbaye chalk aquifer in Belgium. In the confined area, all compounds had non-detects fractions >80%. By contrast, maximum concentrations exceeded EU's drinking-water standard (100 ng L−1) in the unconfined area. This contrast confirms that recent recharge and polluted water did not reach the confined area, yet. Multivariate analyses based on variables representative of the hydrogeological setting revealed higher diuron and simazine concentrations in the southeast of the unconfined area, where urban activities dominate land use and where the aquifer lacks protection from a less permeable layer of hardened chalk. At individual sites, positive correlations (up to τ=0.48 for bentazone) between pesticide compound concentrations and multi-annual groundwater level fluctuations confirm occurrences of remobilization. A downward temporal trend of atrazine concentrations likely reflects decreasing use of this compound over the last 28 years. However, the lack of a break in concentrations time series and maximum concentrations of atrazine, simazine, DEA and BAM exceeding EU's standard post-ban years provide evidence of persistence. Contrasting upward trends in bentazone concentrations show that a time lag is required for restriction measures to be efficient. These results shed light on factors governing pesticide compound concentrations in chalk aquifers. The developed methodology is not restricted to chalk aquifers, it could be transposed to study other pollutants with concentrations below detection limits.

Broad spectrum screening of 463 organic contaminants in rivers in Macedonia

Target screening of 463 organic contaminants in surface water using ultra high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) with direct injection was performed in spring of 2015 in northern Macedonia, at six sampling sites in four rivers belonging to Vardar basin: Kriva, Zletovska, Bregalnica and Vardar. The aim of the study was to differentiate between various types of organic contamination characteristic for different types of anthropogenic activities, such as mining, agriculture, and urbanization. Depending on the studied river, 9–16% of analyzed compounds were detected. The highest total levels of organic contaminants were recorded in agriculturally impacted Bregalnica River (1839–1962ngL−1) and Vardar River downstream from the city of Skopje (1945ngL−1), whereas the lowest level was found in the mining impacted Zletovska River (989ngL−1). The principal organic contaminants of the Bregalnica River were herbicides (45–55% of all detected compounds; 838–1094ngL−1), with the highest concentrations of bentazone (407–530ngL−1) and molinate (84–549ngL−1), common herbicides in rice cultivation. The main organic contaminants in the other rivers were drugs (70–80% of all detected compounds), with antibiotics as a predominant drug class. The highest drug concentrations were measured in the Vardar River, downstream from Skopje (1544ngL−1). Screening of surface water by UHPLC-QTOF-MS was proven as a practical tool for fast collection of comprehensive preliminary information on organic contamination of natural waters, which can present a significant contribution in the monitoring and preservation of good ecological status of freshwater ecosystems.

Adsorption of bentazon on two kinds of granular activated carbons: equilibrium, kinetic and thermodynamic studies

The adsorption of bentazon on two types of granular activated carbons (GACs), VRU F36X16 (VRU) and WS-480 (WS) from aqueous solution was evaluated by kinetics, isotherms, and thermodynamic models in this study. The impacts of initial bentazon concentration, temperature, and initial solution pH were also investigated. The equilibrium adsorption capacity (qe) of each GAC was appreciable under the experimental condition, especially VRU. For either GAC, the adsorption process fitted pseudo-second-order equation best and statistics matched two-step intra-particle diffusion model well. Dubinin–Radushkevich model was the most suitable one for bentazon adsorption on VRU, while Redlich and Peterson model best described bentazon adsorption on WS. Both for VRU and WS, the adsorption process was exothermic and belonged to physisorption. The qe of VRU and WS increased as initial bentazon concentration increased, though the removal rate of bentazon decreased. 25°C was the optimal condition for bentazon adsorption on either GAC, while the qe of both GACs dropped as the temperature increased. Although the increase in pH could hinder bentazon adsorption on GACs significantly, there was a slight change in the adsorption capacities of VRU and WS when initial solution pH was in the range 5–9.

Zero-valent iron (ZVI) activation of persulfate (PS) for oxidation of bentazon in water

Bentazon (BTZ) in water, a broadly used herbicide in agriculture, is toxic to human beings and has a negative impact on ecosystem. In this study, zero-valent iron (ZVI) activation of persulfate (PS) for the oxidation of BTZ was investigated. More active sulfate radicals produced from the system were principally responsible for the BTZ degradation. The BTZ removal well followed a pseudo-first-order (PFO) kinetics pattern. Key factors affecting the treatment were tested, including ZVI concentration, PS dose, initial BTZ concentration, initial solution pH, temperature and common coexisting ions in water. Under the optimal ZVI (4.477mM) and PS (0.262mM) concentrations, 0.021mM BTZ was totally removed at an initial pH⩽7.Generally, lower BTZ concentration, lower pH and higher temperature favored the treatment. Different coexisting ions exhibited different effects. Al3+, Cl− and NO3− improved the treatment; NH4+, Ca2+, and Mg2+ did not significantly influence the BTZ removal; and, Mn2+, Cu2+, CO32−, HCO3−, PO43−, HPO42− and H2PO4− inhibited the BTZ degradation. Most of BTZ were not mineralized, and instead degraded into three major degradation products including 2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide (P1, C7H6N2O3S), 2-aminobenzoic acid (anthranilic acid) (P3, C7H7NO2), and 2-amino-2-sulfobenzoic acid (P5, C7H7NO5S). This study demonstrates that ZVI/PS is a viable alternative for controlling BTZ-induced water pollution.

Synthesis, characterization, and application of ZnO/TiO2 nanocomposite for photocatalysis of a herbicide (Bentazon)

The purpose of this investigation was to study the applicability of ZnO–TiO2 composite as a photocatalyst for degradation of Bentazon. Effects of various parameters such as catalyst dosage, pH, initial Bentazon concentration, oxygen purging gas, hydrogen peroxide concentration and type of organic compounds on the removal efficiency of Bentazon were studied. The results of SEM and FT-IR analysis demonstrated favorable immobilization of zinc oxide nanoparticles onto TiO2. The greatest removal of Bentazon was observed at neutral pH due to photo-corrosion of ZnO on composite in acidic and basic conditions. The pseudo-first-order rate constant (kobs) and electrical energy per order (EEo) were greatly dependent on the Bentazon concentration. Removal efficiency of Bentazon was increased with O2 purging and addition of H2O2, while it was decreased in the presence of organic compounds. Removal efficiency of Bentazon by UV/ZnO/TiO2 process was greater than that by UV/TiO2 process, UV/ZnO, and UV alone. Photocatalytic activity was maintained even after five successive cycles.

Preparation, characterization and application of a CTAB-modified nanoclay for the adsorption of an herbicide from aqueous solutions: Kinetic and equilibrium studies

Abstract In this study, surfactant-modified pillared montmorillonites (MMT) were prepared using cetyltrimethylammonium bromide (CTAB) by the intercalation method and used as adsorbent to remove bentazon from aqueous solutions. The main compositions of MMT and CTAB/MMT were characterized by Fourier transform–infrared spectroscopy (FT–IR), X-ray diffraction (XRD), scanning electron micrography (SEM) and energy dispersive X-ray (EDX) spectroscopy. The removal efficiency of bentazon was studied as a function of adsorbent dosage, pH, initial bentazon concentration and ionic strength (sodium carbonate, sodium bicarbonate, sodium sulfate and sodium chloride). The removal efficiency of bentazon by CTAB/MMT was more than that of MMT in similar conditions. By increasing adsorbent dosage and initial bentazon concentration, the removal efficiency was increased and declined, respectively. The results showed that the maximum adsorption of organo-modified montmorillonite was obtained at pH 3. The maximum adsorption capacity was estimated to be 500 mg/g at pH 3 and room temperature. The study of the adsorption kinetic model revealed that the pseudo-second order model was the best applicable one to describe the adsorption of bentazon onto CTAB/MMT. Adsorption data were analyzed by both Langmuir and Freundlich adsorption isotherms and the results showed that it was better described by the Langmuir model. The adsorption capacities of the samples were found to increase with Na2CO3 anion saturation, while they decreased in the presence of NaHCO3, Na2SO4 and NaCl.

Treatment of bentazon herbicide solutions by vacuum membrane distillation

Experimental investigations were carried out to treat bentazon solutions by the vacuum membrane distillation process (VMD). The effects of several parameters, including feed temperature, feed flow rate, vacuum pressure and initial bentazon feed concentration on flux quality and quantity were studied. The VMD process was found to be effective in the treatment of the bentazon solutions as the permeate was absolutely pure water. Results showed that increasing temperature and flow rate and decreasing vacuum pressure and bentazon concentration enhance permeate flux. Temperature and vacuum pressure were found to be the most important factors for permeate flux. Under the best conditions (a feed temperature of 60°C and a vacuum pressure of 30mbar), a maximum permeate flux of 92.94kg/m2h was obtained. Also, a mathematical model describing the variation of bentazon concentration with time was developed and validated with the experimental results.

Pesticide Health Risk Mapping and Sensitivity Analysis of Parameters in Groundwater Vulnerability Assessment

AbstractThe extensive use of pesticides for increasing the agricultural production is affecting the quality of groundwater. The objectives of this article are to (i) develop pesticide relative leaching ranks for well sites, (ii) develop maps for human health risks due to pesticide applications, and (iii) identify the most significant parameters in pesticide simulations for groundwater vulnerability assessment. The methods include (i) development of acifluorfen relative leaching ranks for 25 well sites using ArcPRZM‐3, (ii) development of health risk maps using model simulated maximum dissolved bentazon concentrations on the basis of USA drinking water quality guidelines, (iii) sensitivity analysis for 14 ArcPRZM‐3 input parameters using the Plackett–Burman method. ArcPRZM‐3 is a user‐friendly system for spatial modeling of pesticide leaching from surface to groundwater. Thirteen acifluorfen relative leaching potential ranks were developed in which the pesticide leaching decrease from 1 to 13. The model predicted ranks for well 34 and well 9 were 2nd and 3rd, respectively, and acifluorfen was detected in both wells during the physical monitoring. The percentages of high health risks in the agricultural areas were 48.38 and 72.72% for Randolph and Independence Counties, respectively. The most significant parameters were thickness of horizon compartment, runoff curve number of antecedent moisture condition II for cropping, soil bulk density, and total application of pesticide. The irrigation, soil permeability, and numerical dispersion could impact the pesticide leaching in soils toward groundwater. The ArcPRZM‐3 system could be efficiently applied for spatial modeling and mapping of pesticide concentrations for groundwater vulnerability assessment on a large scale.

Predicting pesticide leaching under climate change: Importance of model structure and parameter uncertainty

The assessment of climate change impacts on pesticide leaching requires a careful consideration of both parameter uncertainty and model structural error. Our aim was to assess (i) model structure uncertainty, with specific focus on the effects of temperature on pesticide sorption and diffusion, and its relation to parameter uncertainty and (ii) the importance of these sources of uncertainty in long-term predictions of pesticide leaching in the perspective of climate change. We introduced optional functions describing the effects of temperature on sorption and diffusion into the pesticide fate and transport model MACRO5.2, which resulted in four structurally different versions. The generalised likelihood uncertainty estimation (GLUE) method was applied to these four structurally different model versions in order to generate an ensemble of acceptable parameter combinations for long-term predictions of pesticide leaching under climate change. The analysis was performed in a two-step procedure. First, for each model version, 80,000 parameter combinations were tested against a comprehensive field data set of bromide and bentazone concentrations in drainflow and in the soil profile to identify acceptable parameter combinations. In a second step, we performed 30-year predictions based on these acceptable parameter sets for three hypothetical compounds that differed in their sorption strength. The period 1970–1999 was used to represent the current climate for a region in south-west Sweden. The future climate time series was derived for the period 2070–2099 by perturbing the observed time series based on monthly change factors calculated from climate projections of the regional climate model RCA3 with boundary conditions of the global circulation model ECHAM5 forced by the A2-emission scenario. For all three pesticide compounds, total losses were predicted to increase for autumn applications due to projected increases in winter rainfall, but decrease for spring applications. Differences between model versions were found, despite the large uncertainty in parameter estimates. Thus, temperature dependent diffusion was shown to be important for weakly sorbed compounds, while inclusion of temperature dependent sorption significantly affected the predictions for moderately and strongly sorbed compounds. The response to climate change was consistent for the different model versions, but the models that included temperature dependent sorption showed relatively more leaching in a future climate. Our findings stressed the importance of considering temperature dependent processes when modelling future pesticide losses.

Effect of toxic components on microbial fuel cell-polarization curves and estimation of the type of toxic inhibition.

Polarization curves are of paramount importance for the detection of toxic components in microbial fuel cell (MFC) based biosensors. In this study, polarization curves were made under non-toxic conditions and under toxic conditions after the addition of various concentrations of nickel, bentazon, sodiumdodecyl sulfate and potassium ferricyanide. The experimental polarization curves show that toxic components have an effect on the electrochemically active bacteria in the cell. (Extended) Butler Volmer Monod (BVM) models were used to describe the polarization curves of the MFC under nontoxic and toxic conditions. It was possible to properly fit the (extended) BVM models using linear regression techniques to the polarization curves and to distinguish between different types of kinetic inhibitions. For each of the toxic components, the value of the kinetic inhibition constant Ki was also estimated from the experimental data. The value of Ki indicates the sensitivity of the sensor for a specific component and thus can be used for the selection of the biosensor for a toxic component.