Molecularly imprinted polymers for the detection of benomyl residues in water and soil samples

Benomyl is a benzimidazol fungicide used against various crop pathogens. Although banned in many countries, it is still widely used worldwide and is listed in different monitoring programs among the substances to be monitored to assess human exposure to pesticide residues. The assessment of benomyl is mainly based on the analysis of the residues of its most important metabolite, carbendazim. Existing methods often lack of selectivity and display a limited performance because of the presence of co-extracted compounds. Molecularly imprinted polymers (MIPs) offer an alternative methodology, adsorbing preferentially those target molecules for which the polymers are specifically prepared. In this study, we optimized the synthesis of a polymer imprinted with benomyl. Tests of specificity recognition showed a good performance for carbendazim compared with other similar pesticides. The mean recovery of benomyl (measured as carbendazim) from water samples was estimated to be 90% for MIPs while with real soil samples collected in Morocco the recovery efficiency was 62%. Preliminary tests also suggest that this MIP can implement traditional SPE techniques for assessing benomyl residual concentrations in environmental samples.     

Development of controlled release nanoformulations of carbendazim employing amphiphilic polymers and their bioefficacy evaluation against Rhizoctonia solani

Controlled release nanoformulations of carbendazim (Methyl 1H-benzimidazol-2-ylcarbamate), a systemic fungicide, have been prepared using laboratory synthesized poly(ethylene glycols) (PEGs)-based functionalized amphiphilic copolymers. The release kinetics of carbendazim from developed controlled release (CR) formulations was studied and compared with that of the commercially available 50% Wettable Powder (WP). Further, the bioefficacy evaluation of developed formulations was done against plant pathogenic fungi Rhizoctonia solani by the poison food technique method. The release of maximum amount of carbendazim from developed formulations was dependent on the molecular weight of PEGs and was found to increase with increasing molecular weights. The range of carbendazim release was found to be between 10th to 35th day as compared to commercial formulation which was up to 7th day. The diffusion exponent (n value) of carbendazim in water ranged from 0.37 to 0.52 in the tested formulations. The half-release (t_1/2) values ranged between 9.47 and 24.20 days, and the period of optimum availability (POA) of carbendazim ranged from 9.15 to 26.63 days. Also, ED₅₀ values of the developed formulations vary from 0.40 to 0.74 mg L^?1. These formulations can be used to optimize the release of carbendazim to achieve disease control for the desired period depending on the matrix of the polymer used.     

Control of ammonia and urea emissions from urea manufacturing facilities of Petrochemical Industries Company (PIC), Kuwait

Petrochemical Industries Company (PIC) in Kuwait has mitigated the pollution problem of ammonia and urea dust by replacing the melting and prilling units of finished-product urea prills with an environmentally friendly granulation process. PIC has financed a research project conducted by the Coastal and Air Pollution Program’s research staff at the Kuwait Institute for Scientific Research to assess the impact of pollution control strategies implemented to maintain a healthy productive environment in and around the manufacturing premises. The project was completed in three phases: the first phase included the pollution monitoring of the melting and prilling units in full operation, the second phase covered the complete shutdown period where production was halted completely and granulation units were installed, and the last phase encompassed the current modified status with granulation units in full operation. There was substantial decrease in ammonia emissions, about 72%, and a 52.7% decrease in urea emissions with the present upgrading of old melting and prilling units to a state-of-the-art technology “granulation process” for a final finished product. The other pollutants, sulfur dioxide (SO₂), nitrogen oxides (NO_x), and volatile organic compounds (VOCs), have not shown any significant change, as the present modification has not affected the sources of these pollutants.

Implications: Petrochemical Industries Company (PIC) in Kuwait has ammonia urea industries, and there were complaints about ammonia and urea dust pollution. PIC has resolved this problem by replacing “melting and prilling unit” of final product urea prills by more environmentally friendly “granulation unit.” Environmental Pollution and Climate Program has been assigned the duty of assessing the outcome of this change and how that influenced ammonia and urea dust emissions from the urea manufacturing plant.     

The effects of benomyl and its breakdown products carbendazim and butyl isocyanate on the structure and function of tracheal ciliated cells

Abstract

The effects of the fungicide benomyl and its breakdown products, carbendazim and butyl isocyanate, were examined on canine tracheal epithelial tissue in primary culture. Changes in ciliary frequencies were monitored with an optical spectrum analysis system. Serial dilutions of the test compounds were prepared in 100% corn oil and applied to the cell cultures for intervals up to 6 hours and frequencies measured at intervals of 15 minutes to 1 hour. Benomyl and butyl isocyanate caused concentration‐dependent decreases in ciliary beat frequency. Benomyl at 300 μg/ml (3 mM) caused ciliostasis within 75 minutes of exposure. Butyl isocyanate at a molar concentration three times lower than benomyl (1 mM) caused a similar response, although within 30 minutes. The IBC₅₀ for benomyl was 0.75 mM, while for butyl isocyanate it was 0.52 mM. Carbendazim caused a moderate decrease in frequency over a 6 hour exposure period. Benomyl caused moderate to severe swelling of the mitochondria of ciliated epithelial cells with other cell organelles appearing normal. Butyl isocyanate did not cause any noticeable effect on cell ultrastructure and the apparently low rate of penetration of carbendazim into cells made it impossible to obtain an effect which justified ultrastructural analysis. It appears, at least for benomyl and butyl isocyanate, that while the physiological effect of these two compounds (inhibition of ciliary beat) is the same, the sites of action in the cell may be different.     

Spray atomization and deposition patterns of one newtonian and two pseudoplastic formulations after aerial application over a mature conifer forest in Newfoundland

Abstract

Spray atomization and deposition patterns of three formulations were investigated in five aerial spray trials in Newfoundland, to understand the inter‐relationships between physical properties, drop size spectra and recovery of the spray volume at ground level. Diflubenzuron (DFB) was sprayed at 30 g active ingredient in 2.0 L/ha. Futura XLV (Fu‐XLV) and Thuricide® 48LV (Thu‐48LV), spray formulations of Bacillus thuringiensis (B.t.), were both applied undiluted at 30 BIU/ha, but in volume rates of 2.1 L/ha and 2.36 L/ha respectively. Each of the three formulations was applied over a 15 ha plot using a Piper Pawnee aircraft fitted with six Micronair® AU5000 atomizers. Spray drops were sampled with Kromekote® cards and deposits were collected on glass plates. Physical properties measured were: viscosity at variable shear rates, volatility and surface tension. The viscosities increased progressively from low (for DFB), moderate (for Thu‐48LV) to high (for Fu‐XLV) values, showing a gradual increase in pseudoplastic behaviour of the three formulations. The volatility data indicated an inverse relationship to the viscosities, but the surface tensions were similar for all the formulations.

The highly pseudoplastic Fu‐XLV atomized into the least wide drop size spectrum. The Newtonian formulation of DFB, on the other hand, atomized into the widest drop spectrum; and the moderately pseudoplastic Thu‐48LV, into an intermediate drop spectrum. Thus viscosity and volatility were more important factors in liquid atomization and drop deposition, than surface tension. Among the three meteorological factors measured, relative humidity appeared more important in drop deposition than did wind speed and temperature, within the range measured.     

Influence of formulation properties on droplet spectra and soil residues of aminocarb aerial sprays in conifer forests

The influence of formulation properties on spray droplet spectra and soil residues was studied in conifer forests in New Brunswick following aerial application of two oil-based aminocarb formulations of variable viscosities and volatilities. For a given volume rate of application, the formulation of low viscosity and high volatility provided a spectrum of small droplets and a low volume deposit on ground cards. For the same volume rate, the nonvolatile formulation of high viscosity provided a spectrum of larger droplets and consequently a higher volume deposit. Both formulations provided low soil residues, although those obtained with the nonvolatile formulation were much higher and persisted for much longer periods than those obtained with the volatile formulation. However, with both formulations the soil residues decayed to undetectable levels (less than 3 ng/g) within 5 days after spraying, indicating that none of the formulations caused any undue persistence of aminocarb in forest soils.     

Effects of nozzle types and 2,4-D formulations on spray deposition

The objective of this study was to evaluate the effects of nozzle types and 2,4-D formulations on spray deposition on different targets. Two field experiments were carried out in a completely randomized design, and treatments were arranged in a factorial scheme. Species in experiment 1 were Sumatran fleabane (Conyza sumatrensis) and Brazil pusley (Richardia brasiliensis) and in experiment 2 were soybeans (Glycine max) and Benghal dayflower (Commelina benghalensis). For both experiments, the first factor corresponded to spray nozzles with different settings (AD 110.015 – 61 and 105 L ha^?1; AD 015-D – 75 and 146 L ha^?1; XR 110.0202 – 200 L ha^?1; and ADIA-D 110.02 – 208 L ha^?1) and the second factor consisted of two formulations of 2,4-D (amine and choline). The formulation of 2,4-D choline has contained Colex-D? Technology. Similar or higher spray deposition was observed on the leaves and artificial targets when using 2,4-D choline as compared to the 2,4-D amine formulation, and these differences in deposition were more evident for nozzles applying lower spray volumes. Deposition was more affected by nozzle type when amine formulation was used, compared to choline formulation.     

Acetamiprid, carbendazim, diuron and thiamethoxam sorption in two Brazilian tropical soils

Sorption of acetamiprid ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), carbendazim (methyl benzimidazol-2-ylcarbamate), diuron (N-(3,4-dichlorophenyl)-N, N-dimethyl urea) and thiamethoxam (3-(2-chloro-thiazol-5-ylmethyl)-5-methyl-[1,3,5]oxadiazinan-4-ylidene-N-nitroamine) was evaluated in two Brazilian tropical soils, Oxisol and Entisol, from Primavera do Leste region, Mato Grosso State, Brazil. To describe the sorption process, batch experiments were carried out. Linear and Freundlich isotherm models were used to calculate the K(d) and K(f) coefficients from experimental data. The K(d) values were utilized to calculate the partition coefficient normalized to soil organic carbon (K(oc)). For the pesticides acetamiprid, carbendazim, diuron and thiamenthoxan the K(oc) (mL g(- 1)) values ranged in both soils from 98 - 3235, 1024 - 2644, 145 - 2631 and 104 - 2877, respectively. From the studied pesticides, only carbendazim presented correlation (r(2) = 0.82 and p < 0.01) with soil organic carbon (OC) content. Acetamiprid and thiamethoxam showed low sorption coefficients, representing a high risk of surface and ground water contamination.     

In vitro toxicity of selected fungicides from the groups of benzimidazoles and demethylation inhibitors to Cladobotryum dendroides and Agaricus bisporus

Twenty microfungal isolates were collected from diseased fruiting bodies of Agaricus bisporus sampled from Serbian mushroom farms during 2003–2007. Based on morphological characteristics and pathogenicity tests, the isolates were identified as Cladobotryum dendroides. The isolates of C. dendroides and A. bisporusF56 and U3 were tested for sensitivity to several selected fungicides in vitro. C. dendroides isolates were found to be more sensitive to prochloraz manganese and flusilazole + carbendazim than to the other fungicides tested (EC₅₀ values were 0.09 and 0.11 mg L^{? 1}, respectively) and weakly resistant to thiophanate-methyl (EC₅₀ values ranged between 6.53 and 12.09 mg L^{? 1}). Selectivity indexes of the tested fungicides on both C. dendroidesand A. bisporusindicated that thiophanate-methyl, cyproconazole + carbendazim and flusilazole + carbendazim had much less selective fungitoxicity than benomyl, carbendazim and prochloraz manganese.     

Carbendazim sorption-desorption in Vietnamese soils

Four Vietnamese soils (denoted AG, CT, ST and TG) which differed with respect to pH (pH 2.9-5.4), clay (17-50%) and organic matter (0.3-9.8%) content, were selected for sorption and desorption studies of carbendazim using the batch equilibration technique. Sorption increased with increasing organic carbon (OC) and clay content. Kd values for carbendazim sorption on AG, CT, ST, TG soils at initial concentration of 20 microg/g were 12.5, 127, 8.1 and 9.6 ml/g, respectively. The OC partition coefficients (Koc) for AG, CT, ST and TG were 1140, 1300, 2700 and 960 ml/g, respectively. Carbendazim was strongly sorbed and the binding was less reversible in the acid sulfate soil (CT), than in the other soils. The CT soil had both the highest OC content (9.8%) and the highest clay content (49.8%). The influence of pH on carbendazim sorption was studied in the ST and CT soils. Sorption of carbendazim by the sandy ST soil (OC 0.3%; clay content 26.3%) increased as the pH decreased, while sorption of carbendazim by the CT soil decreased as pH decreased.     

Rain‐washing of mimic®, RH‐5992, from balsam fir foliage following application of two formulations

Abstract

Two formulation concentrates of the insecticide, RH‐5992 [N'‐t‐butyl‐N'‐(3,5‐dimethylbenzoyl)‐N‐(4‐ethylbenzoyI) hydrazine], an aqueous flowable (2F) and an emulsion‐suspension (ES), were diluted with water to provide spray mixes containing dosage rates ranging from 35 to 150 g of the active ingredient (AI)/ha. The mixes were sprayed in a laboratory chamber, onto balsam fir branch tips collected from field trees and greenhouse‐grown seedlings. Droplet spectra and spray mass recovery were determined on artificial samplers. Simulated rainfall of two different intensities was applied at different rain‐free periods, and rain droplet sizes were determined. Foliar washoff of RH‐5992 was assessed after application of different amounts of rain, and the increase in soil residues was evaluated.

A direct relationship was indicated between the amount of rainfall and RH‐5992 washoff. The larger the rain droplet size, the greater the amount washed off. Longer rain‐free periods made the deposits more resistant to rain. Regardless of the amount of rainfall, rain droplet size and rain‐free period, foliar deposits of the 2F formulation were washed off to a greater extent than the ES formulation. The increase in soil residues due to foliar washoff was greater for the 2F than for the ES formulation. The deposits of the emulsion‐suspension were consistently more resistant to rain‐washing than those of the aqueous flowable formulation.     

Adsorption, transformation, and bioavailability of the fungicides carbendazim and iprodione in soil, alone and in combination

When studying the effect of mixtures of toxic substances on soil organisms, attention must be paid to peculiarities in exposure to mixtures as opposed to that of single toxicants. The fungicides carbendazim and iprodione compete in the adsorption to soil. The presence of iprodione reduced the adsorption of carbendazim by 30%, while carbendazim reduced the adsorption of iprodione by 70%. Iprodione had little effect on the transformation rate of carbendazim in soil. However, carbendazim retarded the transformation of iprodione in soil by 26%. The concentration of the fungicides in pore water was found to be substantially higher for mixtures than when a fungicide alone was present in the soil. The effect of the additional fungicide on the concentration is especially apparent in the period following the first 1 to 2 weeks of the incubation. The inclusion of copper in the mixture has little additional effect on the concentration of the fungicides in pore water.     

Comparative study of the effects of MCPA, butylate, atrazine, and cyanazine on Selenastrum capricornutum

The herbicides MCPA, butylate, atrazine and cyanazine are extensively used in Canadian agriculture and information regarding their effects on indigenous biota is scarce. Phytotoxicity assessments were conducted in the laboratory on the common green alga Selenastrum capricornutum using both the active ingredient of the herbicides and their formulated products (for MCPA and butylate). Endpoints determined after the 96 h exposure included algal population growth inhibition (IC50-cell counts), percent lethality (LC50-flow cytometry derived) and photosynthetic electron transport inhibition (EC50-fluorescence induction). Pesticide formulations had greater toxic effects than the active ingredient alone. The 96 h IC50 (50% Inhibition Concentration) and LOEC (Lowest Observable Effects Concentration) using cell counts of S. capricornutum were 18.4 and 8.9 mg l(-1) respectively for MCPA-active ingredient and for MCPA-formulated, these were 0.62 and 0.0062 mg l(-1) respectively. Those for butylateactive ingredient were 61.0 and 8.3 mg l(-1) and for butylate-formulated 1.46 and 0.17 mg l(-1), respectively. The triazines active ingredient, which are photosynthetic inhibitors, had greater effects than either the MCPA or butylate. The IC50 for cyanazine and atrazine were 0.059 and 0.026 mg l(-1), respectively. By comparing the IC50 and LC50 values for the tested active ingredients, it was found that the effects of atrazine were algicidal, whereas those of cyanazine, butylate and MCPA were algistatic.     

Acetamiprid,carbendazim, diuron and thiamethoxam sorption in two Brazilian tropical soils

Sorption of acetamiprid ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), carbendazim (methyl benzimidazol-2-ylcarbamate), diuron (N-(3,4-dichlorophenyl)-N, N-dimethyl urea) and thiamethoxam (3-(2-chloro-thiazol-5-ylmethyl)-5-methyl-[1,3,5]oxadiazinan-4-ylidene-N-nitroamine) was evaluated in two Brazilian tropical soils, Oxisol and Entisol, from Primavera do Leste region, Mato Grosso State, Brazil. To describe the sorption process, batch experiments were carried out. Linear and Freundlich isotherm models were used to calculate the K _d and K _f coefficients from experimental data. The K _d values were utilized to calculate the partition coefficient normalized to soil organic carbon (K _oc ). For the pesticides acetamiprid, carbendazim, diuron and thiamenthoxan the K _oc (mL g^{? 1}) values ranged in both soils from 98 – 3235, 1024 – 2644, 145 – 2631 and 104 – 2877, respectively. From the studied pesticides, only carbendazim presented correlation (r² = 0.82 and p < 0.01) with soil organic carbon (OC) content. Acetamiprid and thiamethoxam showed low sorption coefficients, representing a high risk of surface and ground water contamination.     

Residue levels of fenitrothion and aminocarb in the air samples collected from experimental spray blocks in New Brunswick in 1982

Abstract

Fenitrothion and aminocarb formulations were aerially sprayed over mixed coniferous forests near Fredericton and Bathurst, New Brunswick, Canada. Insecticide concentrations inside the spray blocks were measured at intervals of time by trapping the airborne toxicants in a fritted‐glass bubbler containing dimethylformamide (DMF). The residues in DMF were analysed by gas chromatography. Concentrations of the insecticides in the air sampled decreased rapidly with time from peak levels of 1997 ng/m³ (fenitrothion) and 1201 ng/m³ (aminocarb). Concentrations of the two insecticides in the air samplers were dependent upon the nature of the chemicals, type of formulation used, spray timings and other environmental factors.     

Controlled-release formulations of cyromazine-lignin matrix coated with ethylcellulose

An encapsulation system was developed and designed to give long-lasting effectiveness of the insect growth regulator cyromazine. Cyromazine was incorporated in lignin-poly (ethylene glycol) (PE) controlled-release formulations by means of a melting process. The basic formulation [lignin (65%)–PE (20%)–cyromazine (15%)] was coated in a Wurster-type fluidized-bed equipment using two different amounts of ethylcellulose. That of the highest one was modified by the addition of a plasticizer, dibutyl sebacate (DBS). The effect on cyromazine release rate caused by the incorporation of ethylcellulose and DBS in lignin-PE formulation was studied by immersion of the granules in water under static conditions. Using an empirical equation, the time taken for 50% of the active ingredient to be released into water (T₅₀) was calculated. From the analysis of the T₅₀ values, the influence of ethylcellulose appears clearly defined, observing a delay in release rate of cyromazine with respect to the basic lignin-PE formulation. In addition, the granules coated with ethylcellulose and the plasticizer lead the slowest release rate into water. The release of cyromazine into water is controlled by a diffusion mechanism. The thickness and permeability of the coating film are the most important factors that affect cyromazine release.     

Controlled-release formulations of cyromazine-lignin matrix coated with ethylcellulose

An encapsulation system was developed and designed to give long-lasting effectiveness of the insect growth regulator cyromazine. Cyromazine was incorporated in lignin-poly (ethylene glycol) (PE) controlled-release formulations by means of a melting process. The basic formulation [lignin (65%)-PE (20%)-cyromazine (15%)] was coated in a Wurster-type fluidized-bed equipment using two different amounts of ethylcellulose. That of the highest one was modified by the addition of a plasticizer, dibutyl sebacate (DBS). The effect on cyromazine release rate caused by the incorporation of ethylcellulose and DBS in lignin-PE formulation was studied by immersion of the granules in water under static conditions. Using an empirical equation, the time taken for 50% of the active ingredient to be released into water (T(50)) was calculated. From the analysis of the T(50) values, the influence of ethylcellulose appears clearly defined, observing a delay in release rate of cyromazine with respect to the basic lignin-PE formulation. In addition, the granules coated with ethylcellulose and the plasticizer lead the slowest release rate into water. The release of cyromazine into water is controlled by a diffusion mechanism. The thickness and permeability of the coating film are the most important factors that affect cyromazine release.     

Effect of day time climatic conditions associated with different 2,4-D formulations on spray deposition and weed control

Abstract

The aim of this study was to evaluate the effect of time of the day and their associated climatic conditions on spray deposition of two 2,4-D formulations, as well as the influence on weed control. The experiment was installed in the field in complete randomized design. Treatments were arranged in factorial design 8?×?2, with 20 repetitions. First factor corresponded to different application time (1:00, 4:00, 7:00, 10:00, 13:00, 16:00, 19:00, and 22:00) with their respective climatic conditions. The second factor consisted of two formulations of 2,4-D applied at 776?g a.e. ha^?1 (2,4-D amine and 2,4-D choline salt with Colex-D? Technology) + glyphosate (816?g a.e. ha^?1). There was more spray deposition when 2,4-D choline formulation was used, and such differences were more evident for applications performed under adverse climatic conditions. More spray deposition was found in applications performed at times of day with more favorable temperature and humidity of the air conditions. Only the initial control of the evaluated species was affected by the time of application.     

Formation of dioxins during exposure of pesticide formulations to sunlight

Chlorinated pesticides can contain impurities of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and their precursors, as a result of various manufacturing processes and conditions. As precursor formation of PCDD/Fs can also be mediated by ultraviolet light (UV), this study investigated whether PCDD/Fs are formed when currently used pesticides are exposed to natural sunlight. Formulations containing pentachloronitrobenzene (PCNB; n = 2) and 2,4-dichlorophenoxyacetic acid (2,4-D; n = 1) were exposed to sunlight in quartz tubes, and the concentration of 93 PCDD/F congeners were monitored over time. Considerable formation of PCDD/Fs was observed in both PCNB formulations (by up to 5600%, to a maximum concentration of 57 000 μg ∑PCDD/F kg⁻¹) as well as the 2,4-D formulation (by 3000%, to 140 μg ∑PCDD/F kg⁻¹). TEQ also increased by up to 980%, to a maximum concentration of 28 μg kg⁻¹ in PCNB, but did not change in the 2,4-D formulation. Assuming similar yields as observed in the present study as a worst case scenario the use of PCNB in Australia may result in the formation of 155 g TEQ annum⁻¹, contributed primarily by OCDD formation. This warrants detailed evaluations on the contemporary release of PCDD/Fs to the environment after the use of pesticides. Changes in congener profiles (including the ratio of PCDDs to PCDFs (DF ratio)) suggest that pesticide sources of PCDD/Fs after sunlight exposure may not be recognized based on matching source fingerprints established from manufacturing impurities. These changes also provide preliminary insights into the possible formation routes and types of precursors involved.     

The chemical stability of formulations of some hydrolyzable insecticides in aqueous mixtures with hydrolysis catalysts

Abstract

The active ingredients in commercial formulations of malathion, oxamyl, carbaryl, diazinon, and chlorpyrifos diluted to “spray tank”; concentrations with buffered distilled or natural water of pH 4–9 were stable for at least 24 hr. Formulations of trichlorfon were not stable at pH 7 or above but disappearance rates were slower than for the pure chemical in homogeneous solution. Cupric ion was observed to be an effective catalyst for the hydrolysis of a variety of pure organophosphorus insecticides but did not catalyze hydrolysis of the active ingredients of the formulations examined. Increasing the dilution of the formulation increased the susceptibility of malathion, oxamyl, and carbaryl to hydrolysis.