Degradation Of Fipronil Research Articles

Environmental behavior of the chiral insecticide fipronil: Enantioselective toxicity, distribution and transformation in aquatic ecosystem

The enantioselective environmental behaviors of the chiral insecticide fipronil and its metabolites in lab-scale aquatic ecosystems were studied and the toxicity of fipronil enantiomers and the metabolites to non-target organisms Lemna minor (L. minor) and Anodonta woodiana (A. woodiana) was also investigated in this work. Water-sediment, water-L. minor, water-A. woodiana, and water-sediment-L. minor-A. woodiana ecosystems were set up and exposed to fipronil through a 90-day period. The results showed fipronil could be degraded significantly faster (half-life of 4.6 days) in the complex water-sediment-L. minor-A. woodiana ecosystem. A. woodiana played a crucial role in the dissipation of fipronil, and the microorganisms in the sediment also made great contribution to the degradation of fipronil in aquatic ecosystems. All the three metabolites fipronil desulfinyl, fipronil sulfide and fipronil sulfone were detected in the ecosystems and were more persistent than fipronil. Enantioselective degradation of fipronil was observed with S-fipronil being preferentially degraded in sediment and L. minor, while R-fipronil was metabolized preferentially in A. woodiana. EC50 for L. minor was obtained using 7-day exposure, and for A. woodiana was obtained using 72-h exposure. S-fipronil was more toxic to A. woodiana, while R-fipronil showed higher toxicity to L. minor. Moreover, the three metabolites were found more toxic than fipronil indicating significant environment risks due to their persistence. The present study might have important implications for the risk assessment of fipronil and its metabolites in real aquatic environment.

Degradation and sorption of fipronil and atrazine in Latossols with organic residues from sugarcane crop

ABSTRACT: Organic residues from sugarcane crop and processing (vinasse, boiler ash, cake filter, and straw) are commonly applied or left on the soil to enhance its fertility. However, they can influence pesticide degradation and sorption. The objective of this study was to assess the effect of adding these organic residues on the degradation and sorption of fipronil and atrazine in two soils of the State of Mato Grosso do Sul, MS, Brazil. The degradation experiment was carried out with laboratory-incubated (40 days; 28°C; 70% field capacity) soils (0-10cm). The batch equilibration method was used to determine sorption. Fipronil (half-life values of 15-105 days) showed to be more persistent than atrazine (7-17 days). Vinasse application to the soil favored fipronil and atrazine degradation, whereas cake filter application decreased the degradation rates for both pesticides. Values for sorption coefficients (Kd) were determined for fipronil (5.1-13.2mL g-1) and atrazine (0.5-1.5mL g-1). Only straw and cake filter residues enhanced fipronil sorption when added to the soil, whereas all sugarcane residues increased atrazine sorption.

The toxicity, bioaccumulation, elimination, conversion of the enantiomers of fipronil in Anodonta woodiana

The enantioselective bioaccumulation and elimination of fipronil in Anodonta woodiana (A. woodiana) were studied and the main metabolites fipronil desulfinyl, fipronil sulfide and fipronil sulfone were determined. The acute toxicity of the enantiomers of fipronil and the three metabolites were also investigated. In the bioaccumulation process, fipronil in A. woodiana reached equilibrium after 11days with BCF value of 0.2, and the enantiomeric fraction (EF) values showed that the bioaccumulation was enantioselective with enantioenrichment of S-fipronil. The degradation of fipronil in A. woodiana fitted first-order kinetics model with half-lives of the enantiomers were 5.8 d for R-fipronil and 7.6 d for S-fipronil, and the EF values decreasing from 0.5 gradually indicating the R-enantiomer was preferentially degraded. The degradation of single enantiomers was also performed and the results revealed a fast conversion of R-fipronil to S-fipronil by A. woodiana. The three metabolites were all detected in A. woodiana-water system, in which fipronil sulfone and fipronil sulfide had higher concentration levels. According to the 72-h LC50 values, S-fipronil was much more toxic than the racemate and R-fipronil. Moreover, the metabolites were more toxic than the parent fipronil. The results suggested the individual enantiomers of chiral pollutants and the metabolites should be considered in the risk assessments.

Degradation of fipronil by Stenotrophomonas acidaminiphila isolated from rhizospheric soil of Zea mays.

Fipronil is a widely used insecticide in agriculture and can cause potential health hazards to non-target soil invertebrates and nearby aquatic systems. In the present study, a fipronil degrading bacterium was isolated from fipronil contaminated soil, i.e. rhizospheric zone of Zea mays. Morphological, biochemical and molecular characterization of strain indicated that it clearly belongs to Stenotrophomonas acidaminiphila (accession no. KJ396942). A three-factor Box–Behnken experimental design combined with response surface modeling was employed to predict the optimum conditions for fipronil degradation. The optimum pH, temperature and total inocula biomass for the degradation of fipronil were 7.5, 35 °C and 0.175 g L−1, respectively. The bacterial strain was able to metabolize 25 mg L−1 fipronil with 86.14 % degradation in Dorn’s broth medium under optimum conditions. Metabolites formed as a result of fipronil degradation were characterized with gas liquid chromatograph. A novel fipronil degradation pathway was proposed for S. acidaminiphila on the basis of metabolites formed. Non-sterilized soil inoculated with S. acidaminiphila was found to follow first order kinetics with a rate constant of 0.046 d−1. Fipronil sulfone, sulfide and amide were formed as the metabolites and were degraded below the quantifiable limit after 90 days of time period. Given the high fipronil degradation observed in the present study, S. acidaminiphila may have potential for use in bioremediation of fipronil contaminated soils.

Bioaccumulation of Legacy and Emerging Organochlorine Contaminants in Lumbriculus variegatus.

Freshwater sediment-dwelling Lumbriculus variegatus is known to serve as a vector for the transfer of contaminants from sediments to higher trophic level organisms, but limited data exist on the bioaccumulation of chemicals associated with sediments containing high total organic carbon(TOC). In the current study, sediments from the north shore area of Lake Apopka (Florida, USA), containing very high TOC [39% (w/w)], were spiked with four chemicals-p,p'-dichlorordiphenyldichloroethylene (p,p'-DDE), dieldrin, fipronil, and triclosan-individually or in a mixture of the four and then used for bioaccumulation studies. Tissue concentrations of chemicals in L. variegatus were measured at 2, 7, 14, 21, and 28days of exposure, and the bioaccumulation potential was evaluated using biosediment accumulation factors [BSAF (goc/glipid)]. Increase in total body burdens of all four chemicals in L. variegatus was rapid at day 2 and reached a steady-state level after 7days in both single and mixture experiments. Tissue concentrations of fipronil peaked after 2days and then decreased by 70% in sediment experiments suggesting that in addition to the degradation of fipronil that occurred in the sediment, L. variegatus may also be able to metabolize fipronil. The calculated 28-day BSAF values varied among the chemicals and increased in the order fipronil (1.1)<triclosan (1.4)<dieldrin (21.8)<p,p'-DDE (49.8) in correspondence with the increasing degree of their hydrophobicity. The relatively high BSAF values for p,p'-DDE and dieldrin probably resulted from lower-than-expected sorption of chemicals to sediment organic matter either due to the nature of the plant-derived organic matter, as a result of the relatively short equilibration time among the various compartments, or due to ingestion of sediment particles by the worms.

Photocatalytic degradation of fipronil in water by silver-modified lithium vanadium phosphate spheres under visible light irradiation

A novel visible light-driven photocatalyst, lithium vanadium phosphate sphere (LVPS), was prepared by a ball-milling method. For enhancing the photocatalytic performance, LVPS was further modified with silver (ALVPS) by a UV-light photoreduction method. After modification, the crystalline phase of LVPS did not change, however, the UV-Vis diffuse reflectance spectrum of ALVPS was extended to 656 nm, which greatly improved its photoabsorptivity for visible light and enhanced its electron donating capacity. Under the irradiation of sunlight or visible light (>400 nm), ALVPS can rapidly remove fipronil (a persistent organic pollutant, 5 mg L−1) from aqueous solution. More than 99.7% of fipronil was removed by ALVPS after 0.5 h of irradiation, yielding a much higher removal rate than those achieved by nano-TiO2 and Bi2O3. Photo-generated carrier trapping experiments were conducted to elucidate the photocatalytic degradation mechanism further. Hydrogen peroxide and potassium bromate suppressed the photocatalytic activity of ALVPS, while superoxide dismutase and sodium azide reinforced it, verifying that photo-generated electrons played a key role in the photochemical reaction.

Stormwater-related transport of the insecticides bifenthrin, fipronil, imidacloprid, and chlorpyrifos into a tidal wetland, San Francisco Bay, California

Suisun Marsh, in northern San Francisco Bay, is the largest brackish marsh in California, and provides critical habitat for many fish species. Storm runoff enters the marsh through many creeks that drain agricultural uplands and the urban areas of Fairfield and Suisun City. Five creeks were sampled throughout a major storm event in February 2014, and analyzed for representatives of several major insecticide classes. Concentrations were greatest in creeks with urban influence, though sampling was done outside of the primary season for agricultural pesticide use. Urban creek waters reached maximum concentrations of 9.9ng/l bifenthrin, 27.4ng/l fipronil, 11.9ng/l fipronil sulfone, 1462ng/l imidacloprid, and 4.0ng/l chlorpyrifos. Water samples were tested for toxicity to Hyalella azteca and Chironomus dilutus, and while few samples caused mortality, 70% of the urban creek samples caused paralysis of either or both species. Toxic unit analysis indicated that bifenthrin was likely responsible for effects to H. azteca, and fipronil and its sulfone degradate were responsible for effects to C. dilutus. These results demonstrate the potential for co-occurrence of multiple insecticides in urban runoff, each with the potential for toxicity to particular species, and the value of toxicity monitoring using multiple species. In the channels of Suisun Marsh farther downstream, insecticide concentrations and toxicity diminished as creek waters mixed with brackish waters entering from San Francisco Bay. Only fipronil and its degradates remained measurable at 1–10ng/l. These concentrations are not known to present a risk based on existing data, but toxicity data for estuarine and marine invertebrates, particularly for fipronil's degradates, are extremely limited.

Enantioselective toxicity and degradation of the chiral insecticide fipronil in Scenedesmus obliguus suspension system.

Fipronil is an effective insecticide, but it presents highly toxic effects in nontarget aquatic organisms. The present study examined the enantioselective toxicity and degradation of fipronil enantiomers in a freshwater algae Scenedesmus obliguus suspension. There was a substantial difference in the acute toxicity of the enantiomers to S. obliguus, with 72-h median effective concentrations (EC50s) of 0.29 mg L(-1) and 1.50 mg L(-1) for the R-fipronil and S-fipronil, respectively. The influences on the concentration of chlorophyll a, chlorophyll b, and carotenoids were determined, and the effects of fipronil on the concentration of chlorophyll a and chlorophyll b were also enantioselective. The degradation of fipronil in algae suspension was enantioselective, with half-lives for R-fipronil and S-fipronil of 2.9 d and 3.2 d, respectively, and the enantiomer fraction reaching 0.65 at the day 17. The enantiomeric differences should be taken into consideration for fipronil risk assessment.

Effective Degradation of Fipronil Using Combined Catalytic Ozonation Processes

Effective removal of Fipronil, an agricultural pollutant, was studied here by coupling heterogeneous catalyst (Degussa P-25 TiO2 nanopowder) with molecular ozone. Compared to molecular ozone alone (74%), enhanced activity (89%) was noted with a coupled TiO2/O3 system at 40 min, which is due to the generation of active superoxide ion species by surface adsorption and reaction of TiO2 with the molecular ozone. The catalytic activity quantification was followed by liquid chromatography with electrospray ionization-tandem mass spectrometry.

Enantioselective toxicity, bioaccumulation and degradation of the chiral insecticide fipronil in earthworms (Eisenia feotida)

The enantioselective acute toxicity to earthworms of racemic fipronil and its individual enantiomers was studied. R-(−)-fipronil was approximately 1.5 times more toxic than the racemate and approximately 2 times more toxic than S-(+)-fipronil after 72 and 96h of exposure, respectively. Assays of fipronil enantiomer bioaccumulation and degradation in earthworms were conducted. The bio-concentration factors (BCFs) were slightly different between the two enantiomers. The enantiomeric fraction (EF) values in earthworms in the bioaccumulation period were approximately 0.5, which indicated there was no enantioselective bioaccumulation. In contrast, the degradation of fipronil in earthworms was enantioselective: the t1/2 values for R- and S-fipronil were 3.3 and 2.5days, respectively, in natural soil, and 2.1 and 1.4days, respectively, in artificial soil. The results of soil analyses showed that the degradation of fipronil was not enantioselective, which suggested that the enantioselectivity of fipronil in earthworms results from the organism's metabolism. The study also demonstrated that the presence of earthworms could accelerate the degradation of fipronil in soil.

Toxicity of the Insecticide Fipronil and Its Degradates to Benthic Macroinvertebrates of Urban Streams

Fipronil is a phenylpyrazole insecticide with increasing urban use. Sixteen urban waterways and municipal wastewater were sampled for fipronil, its environmental degradates, and pyrethroid insecticides. Because findings could not be interpreted with existing data on fipronil degradate toxicity, EC50s and LC50s for fipronil and its sulfide and sulfone derivatives were determined for 14 macroinvertebrate species. Four species were more sensitive than any previously studied, indicating fipronil's toxicity to aquatic life has long been underestimated. The most sensitive species tested, Chironomus dilutus, had a mean 96-h EC50 of 32.5 ng/L for fipronil and 7-10 ng/L for its degradates. Hyalella azteca, a common testing species, was among the least sensitive. The typical northern California creek receiving urban stormwater runoff contains fipronil and degradate concentrations twice the EC50 of C. dilutus, and approximately one-third the EC50 for a stonefly, a caddisfly, and two mayfly species. The present study substantially increases data available on toxicity of fipronil degradates, and demonstrates that fipronil and degradates are common in urban waterways at concentrations posing a risk to a wide variety of stream invertebrates.

Bioremediation of fipronil by a Bacillus firmus isolate from soil

Persistence of fipronil, a new molecule in extensive use against various insect pests is causing serious problems to the environment. Bacillus firmus was isolated by selective enrichment from soil samples collected from sugar fields with known history of pesticide usage and evaluated for metabolization of fipronil in clay loam soil. Soil samples in 50g aliquotes were fortified with fipronil @ 0.50–1.50mgkg−1 and inoculated with B. firmus cells (45×107CFUmL−1) and incubated at 25°C. Each sample in triplicates was drawn periodically up to 56d and residual fipronil contents analyzed by gas liquid chromatograph. Fipronil residues were not detected after 35d at lower doses of fipronil (@ 0.50, 0.75 and 1.00mgkg−1). However, at higher doses (@ 1.25 and 1.50mgkg−1) than this total metabolization of fipronil could be observed after 35 and 42d, respectively. Thus whereas, B. firmus proved its potential in efficient metabolization of fipronil, the period required for the same was dose dependent. Amongst various metabolites of fipronil degradation, fipronil sulfide was found to be the main metabolite followed by fipronil sulfone and fipronil amide. Though, desulfinyl metabolite earlier reported as one of the main metabolite of fipronil degradation, the existence of the same was not detected in any of the treatment.

Fipronil decomposition in aqueous semiconductor suspensions using UV light and solar energy

The photocatalytic degradation of fipronil in drinking water was studied using zinc oxide (ZnO) and titanium dioxide (TiO2) as photocatalyst under irradiation by solar and artificial light. Photocatalytic experiments showed that the addition of semiconductors in tandem with the oxidant (Na2S2O8) strongly enhances the degradation rate of fipronil in comparisons carried out with photolytic experiments under artificial light. However, under solar irradiation, the photocatalytic decomposition of fipronil occurs very slowly. The residual levels of fipronil for ZnO/Na2S2O8 and TiO2/Na2S2O8 after 60min of illumination at a constant volumetric rate of photon absorption in the photoreactor were 0.8 and 1.5μg/L, respectively. The main intermediates (fipronil-sulfone, fipronil-sulfide, fipronil-desulfinyl and fipronil-carboxamide) detected during the degradation of fipronil in water were identified.

Persistence of fipronil and its metabolites in soil under field conditions

Fipronil belongs to phenylpyrazole class of chemical compounds. Degradation of fipronil in sandy loam soil was investigated under field conditions by applying fipronil (Regent 5% SC) at 50 (T 1) and 100g a.i. ha(-1) (T 2) in field. Samples were drawn periodically in triplicate on 0 (1h after treatment), 1, 3, 7, 10, 15, 30, 60, and 90days after treatment and analyzed on GC-ECD system equipped with capillary column. The residues of fipronil in both the doses dissipated in the range of 93.33-100% in 90days. Limit of detection (LOD) and limit of determination (LODe/LOQ) were 0.0003 and 0.001mgkg(-1), respectively. Dissipation followed a biphasic first-order kinetics with half-life values of 10.81 and 9.97days for fipronil alone and 8.14 and 13.05days for fipronil along with metabolites in soil at (T 1) and (T 2) treatments, respectively.

Microbial degradation of fipronil by Bacillus thuringiensis

Fipronil, a phenyl pyrazole insecticide has been found to be effective for the control of various insect pests. Due to its higher persistence in soil bioremediation is a promising approach to degrade the pesticide from soil. Isolation and identification of soil microbes was conducted for bioremediation of fipronil contaminated soils. Soil samples collected from different sugarcane growing fields in Gurdaspur district with extensive use of pesticide history served as a source of pesticide degrading microbes. The microbe cultures were grown in Luria broth and maintained at 28°C. After that Dorn's broth enrichment culture supplemented with fipronil was used and Bacillus thuringiensis were isolated. Clay loam soil samples were fortified with fipronil @ 0.50, 0.75, 1.00, 1.25 and 1.50mgkg−1 along with 45×107 microbe cells. Each treatment was replicated thrice and from each fortified (insecticide+microbes) sample, 50g soil sample was taken at 7, 14, 28, 35, 42, 49 and 56 days after initiation of this experiment. Residues were not detected after 28, 35, 35, 35 and 42 days in soil samples after fortification with fipronil @ 0.50, 0.75, 1.00, 1.25 and 1.50mgkg−1. Among metabolites, sulfide was found to be the main metabolite followed by sulfone and amide. Desulfinyl metabolite was not produced in any of the sample. Total fipronil residues were not found to follow the first order kinetics.

Effect of pH on the degradation of imidacloprid and fipronil in paddy water

Effect of pH on the degradation of imidacloprid and fipronil in paddy water

Enantioselective bioaccumulation of soil-associated fipronil enantiomers in Tubifex tubifex

Enantioselective behavior of chiral pesticides in the aquatic environment has been a subject of growing interest. In this study, the enantioselective bioaccumulation of fipronil enantiomers in Tubifex tubifex (Oligochaeta, Tubificida) was detected in both spike–water and spike–soil systems, respectively. For the spike–water treatment, a 9-day exposure experiment was employed and the enantiomer fraction in tubifex tissue was maintained approximately at 0.58 during the experiment. In addition, a 14-day bioaccumulation period was chosen for the spike–soil treatment and a more significant deviation of enantiomer fraction from 0.5 in tubifex tissue was detected, with concentrations of the R-form higher than that of the S-form. Therefore, the bioaccumulation of fipronil was enantioselective in tubifex tissue for the two treatments and the magnitude of enantioselectivity may be influenced by different exposure conditions. For the spike–soil treatment, the concentrations of fipronil in verlying water and soil were also determined. With the presence of tubifex worms, higher concentrations of fipronil in overlying water and lower concentrations in soil were detected than that in the absence of tubifex treatment during the whole 14-day exposure period. This means that tubifex has positive functions in fipronil's diffusion from soil to overlying water and in the degradation of the soil-associated fipronil.

Biodegradation of Fipronil by Paracoccus sp. in Different Types of Soil

In the present studies potential of microorganisms isolated from the cotton fields was explored for the bioremediation of fipronil contaminated soils. The cultures of microbes were grown in Luria broth as shake culture maintained at 28°C. After that Dorn's broth enrichment culture supplemented with fipronil was used and isolated two bacterial cultures viz. Paracoccus sp. and Gamma Proteobacteria. The performance of both bacteria was evaluated for degradation of fipronil in soil. Paracoccus sp. was found better than the Gamma Proteobacteria as far as degradation of fipronil in soil is concerned. The samples of soil were extracted and cleaned up by following a standardized methodology. Fipronil was quantified by gas liquid chromatography and confirmed by gas chromatography mass spectrometer. The limit of quantification of fipronil was worked out to be 10 μg kg(-1). By using this methodology, the mean recoveries of fipronil in different types of soil were found to be more than 85%. The residues of fipronil were found to persist only up to 10 days in soils fortified with fipronil @ 20 μg kg(-1) and amended with Paracoccus sp. while in the soils fortified @ 80 μg kg(-1) fipronil, residues persisted up to 20, 30 and 30 days in loamy sand, sandy loam and clay loam, respectively. Therefore, the use of Paracoccus sp. can further be explored for the bioremediation of fipronil contaminated soils.

Adsorption, transport and degradation of fipronil termiticide in three Hawaii soils

The behavior of the termiticide fipronil in soils was studied to assess its potential to contaminate ground and surface water. This study characterizes (1) adsorption of fipronil in three different soils, (2) transport of fipronil through leaching and runoff under simulated rainfall in these soils and (3) degradation of fipronil to fipronil sulfide and fipronil sulfone in these soils. The adsorption experiments showed a Freundlich isotherm for fipronil with K(oc) equal to 1184 L kg(-1) . In the leaching experiments, the concentration of fipronil and its metabolites in leachate and runoff decreased asymptotically with time. The concentration of fipronil in the leachate from the three soils correlated inversely with soil organic carbon content. The degradation experiment showed that the half-life of fipronil in the soils ranged from 28 to 34 days when soil moisture content was 75% of field capacities, and that 10.7-23.5% of the degraded fipronil was transformed into the two metabolites (fipronil sulfide and fipronil sulfone). Fipronil showed large losses through leaching but small losses via runoff owing to low volumes of runoff water generated and/or negligible particle-facilitated transport of fipronil. The half-life values of fipronil in all three soils were similar.

Degradation of Chlorpyrifos and Fipronil in Rice from Farm to Fork and Risk Assessment

Degradation of pesticide residues (chlorpyrifos and fipronil) in rice from farm to fork and risk assessment for human health were studied to reveal the magnitude of risks faced by different populations of interest, so that appropriate measures can be taken to control the risks, and to refine and update the human health risk assessment data while helping to determine the maximum residue level (MRL) value and harvest interval. Different dosages and treatments were used in field trials for the harvest residue test. Residue levels of postharvest-applied chlorpyrifos and fipronil during storage, exposure to sunlight, washing and boiling processes (boiled rice) were investigated for brown rice. The dietary exposure evaluation model (DEEM) was employed to estimate acute and chronic risks faced by different populations of interest. Percent of reference dose (POR) and margin of exposure (MOE) were calculated. A positive correlation between pesticide residues and the dosage and application frequency of pesticide was found in the field trials. Risk quotients indicate that multiple applications and double dosages of chlorpyrifos increase the risks to the entire population and prolong exposures to toxic concentrations. The concentration of pesticide residues decreased as a function of time, after sunlight exposure, storage, washing, and boiling processes. 91.6 and 96.16% degradations were achieved at the end of the experimental period for fipronil and chlorpyrifos, respectively. The boiling process played an important role in the degradation of these pesticides. The result of risk assessment to human health showed that harvest residues of chlorpyrifos in rice and acute dietary risks of chlopyrifos were of concern. The acute dietary (food only) risk estimated for chlorpyrifos as percent of acute population adjusted dose (aPAD) was frequently over 100%. The risk faced by boys under the age of 14 was higher than that for girls of the same age. For the subpopulation above age 14, the risk reversed. The chronic dietary risk from food alone showed that dietary exposures with fipronil were below the level of concern for the entire population, including children. The risk faced by rural residents was more serious than that for urbanite residents with the most sensitive populations being children and male residents who faced higher acute dietary risk than the other subpopulation groups. The harvest interval was found to be the critical measure to mitigate risk for all populations for safe rice eating. All risk levels decreased to acceptable levels when the harvest interval was extended to 14 d. To address these risks, a number of measures including reduced application rates (should not be doubled at single application), increased retreatment intervals (longer than 7 d) and extended interval of harvest (at least 14 d) will be needed. The MRL for fipronil in rice is recommended to be 0.01 mg kg −1 in accordance with Codex (ref).