Persistence and Metabolism of Imidacloprid in Rice

Imidacloprid is a systemic insecticide which gives effective control of plant and leaf hoppers in rice. The persistence and metabolism of imidacloprid in paddy leaves, rice grains, bran, straw and husk were studied following two applications of imidacloprid (Confidor 17.8 SL) @ 20 and 80 g a.i. ha^?1 at an interval of 10 days. Samples of paddy leaves were collected at various time intervals. The samples of rice grains, bran, straw and husk were collected at the time of harvest. The limit of quantification of imidacloprid and its metabolites was worked out to be 0.01 mg kg^?1. The maximum residues of imidacloprid and its metabolites in paddy leaves after 0 day (1 h after last spray) of its application @ 20 and 80 g a.i. ha^?1 were found to be 4.57 and 13.94 mg kg^?1, respectively. These residues could not be detected after 60 and 90 days following last application of imidacloprid at lower and higher dosages, respectively. In rice, olefin metabolite was found to be the main constituent, followed by nitroguanidine, urea, 5-hydroxy, chloronicotinic acid and nitrosimine. The samples of rice grains, bran, straw and husk did not reveal the presence of imidacloprid or its metabolites following its application at both the dosages at harvest.     

Persistence and Metabolism of Fipronil in Rice (Oryza sativa Linnaeus) Field

Rice is one of the most important food crops worldwide. However, it is also a valuable tool in assessing toxicity of organic and inorganic compounds. Fipronil insecticide has been widely used to control rice pests. The research was conducted to evaluate the fate of fipronil in rice-field. Persistence and metabolism of fipronil in rice is studied by applications of Regent 0.3G @ 45 and 180 g a.i. ha^?1 was made 7 days after transplanting of paddy. Samples of paddy plants were collected at 7, 15, 30, 45, 60, 90 and 120 days after the application of insecticide. The samples of rice grains, bran, husk and straw were collected at the time of harvest. The samples were extracted and cleaned up by following a standardized methodology. Fipronil and its metabolites were quantified by gas liquid chromatography and confirmed by gas chromatography mass spectrometer. The total residues of fipronil and its metabolites in paddy plants after 7 days of its application at recommend and four times of recommend doses were found to be 6.60 and 19.85 mg kg^?1, respectively. Among fipronil metabolites, sulfone derivative had maximum residue concentration followed by other metabolites viz. sulfide, amide and desulfinyl. The residues were reached below the detectable limit (0.01 mg kg^?1) after 45 and 90 days at recommend and four time of recommend doses, respectively. At harvest, the samples of paddy straw, rice grains, bran and husk did not reveal the presence of fipronil and its metabolites.     

Fate of Fipronil and its Metabolites in/on Grape Leaves, Berries and Soil Under Semi Arid Tropical Climatic Conditions

Fate of fipronil and its major metabolites fipronil sulfide (MB 45950), fipronil-desulfinyl (MB 46513) and fipronil sulfone (MB 46136) were studied in/on grape leaves, berries and soil. As initial residue deposits on the leaves the major component was that of fipronil, while all the 3 metabolites were also present. Among metabolites residues of MB 46513 was highest followed by MB 46136 and MB 45950. In leaves fipronil degraded faster than its metabolites. The residues of fipronil in leaves degraded at the half-life of 9.6 and 18.3 days and that of total fipronil (sum of fipronil and its metabolites) at 13.6 and 20 days, from treatment at recommended and double the recommended dose, respectively. At the time of harvest in leaves, grape berries and soil residues of fipronil and all its metabolites were below the quantifiable limit of 0.01 mg kg^?1.     

Estimation of Quizalofop Ethyl Residues in Black Gram (Vigna mungo L.) by Gas Liquid Chromatography

Quizalofop ethyl, a phenoxy propionate herbicide is used for post emergence control of annual and perennial grass weeds in broad-leaved crops in India. The experiments were designed to study the harvest time residues of quizalofop ethyl in black gram for two seasons. At harvest time, the residues of quizalofop ethyl on black gram seed, foliage and soil were found to be below the determination limit of 0.01 mg kg^?1 following a single application of the herbicide at 50 and 100 g a.i. ha^?1 for both the periods. Application of the herbicide is quite safe from a consumer and environmental point of view.     

Degradation Dynamics of Emamectin Benzoate on Cabbage Under Subtropical Conditions of Punjab, India

Emamectin benzoate (Proclaim 5 SG) was applied to cabbage at 8.5 and 17 g a.i. ha^?1, during the head initiation stage. A high performance liquid chromatography (HPLC) analytical method, for the determination of emamectin benzoate in cabbage, was developed. Average recoveries of emamectin benzoate ranged from 92 % to 96 % at different fortification levels (0.05, 0.25 and 0.50 mg kg^?1). The initial deposits, 0.11 and 0.21 mg kg^?1 of emamectin benzoate at 8.5 and 17 g a.i. ha^?1, dissipated below the determination limit of 0.05 mg kg^?1 in 3 and 5 days, respectively.     

Persistence Behavior of Imidacloprid and Carbosulfan in Mango (Mangifera indica L.)

Imidacloprid was sprayed on mango cv. Dashehari at 0.3 mL L^?1 of water during pre-bloom stage with 6–8 cm panicle size (first week of March) to control hopper and carbosulfan was sprayed at 2.0 mL L^?1 of water in the trees of mango hybrid (H-1000) during fruit development stage (first week of May) to control leaf webber. Residues of both the insecticides were analysed in peel, pulp and fruit at different stages of fruit development and maturity. The initial residues of imidacloprid, after 30 days of spraying, were 1.21, 0.56 and 1.77 mg kg^?1 in peel, pulp and whole fruit, respectively. The residues persisted in peel for 60 days and in pulp for 50 days and dissipated with a half-life of 38 days. Mature Dashehari fruits at harvest (after 85 days of spraying) were free from imidacloprid residues. Carbosulfan in mango peel dissipated from 5.30 mg kg^?1 (after 1 h of spraying) to 0.05 mg kg^?1 at the time of harvest (after 45 days of spraying). Carbosulfan residue in pulp was very low (0.08 mg kg^?1) after 1 h of spraying, which increased gradually to 0.90 mg kg^?1 after 10 days and finally came down to 0.04 mg kg^?1 after 26 days of spraying. The insecticide residue was not detected in the pulp at the time of harvest. The residues persisted in pulp for 26 days and in peel for 45 days and degraded with a half-life of 7 days. The dissipation of both imidacloprid and carbosulfan followed first order rate kinetics in whole fruit (peel + pulp). Therefore, the safe pre-harvest intervals were suggested to be 55 days for imidacloprid and 46 days for carbosulfan before consumption of mango fruits after spraying of these insecticides.     

Dissipation of Residues of Mancozeb and Metalaxyl in Tomato (Solanum lycopersicum L.)

Dissipation of mancozeb and metalaxyl in tomato was estimated following four applications of a combination formulation Ridomil MZ (mancozeb 64% + metalaxyl 8%) at 0.25 and 0.50% at 10 days interval by carbon disulphide evolution method and gas liquid chromatography with nitrogen phosphorous detector, respectively. Half-life periods for mancozeb were 3.76 and 4.14 days, whereas for metalaxyl these values were 1.29 and 0.41 days at single and double the application rates, respectively. Residues of mancozeb dissipated below limit of quantification (LOQ) of 0.25 mg kg^?1 after 10 and 15 days at single and double the application dosage, respectively. Similarly, residues of metalaxyl took 3 and 5 days to reach LOQ of 0.02 mg kg^?1, at single and double dosages, respectively.     

Dissipation and Persistence of Flubendiamide and Thiacloprid in/on Tomato and Soil

Flubendiamide, a phthalic acid diamide protects the plants against a broad range of economically important lepidopterus pests and thiacloprid a second generation neonicotinoid is effective against the sucking insects, white flies and jassids. To estimate the residues of flubendiamide and thiacloprid on tomato, analytical methods were validated by conducting recovery studies, residues were quantified by using HPLC on C₁₈ column and PDA at 260 λ. Residues of flubendiamide declined below detectable level of 0.01 mg kg^?1 after 5 and 7 days of application at lower and higher dose with RL₅₀ of 0.72 and 1.32 days, respectively. Thiacloprid residues reached below its detectable level of 0.01 mg kg^?1 after 5 and 7 days of its lower and higher dose with RL₅₀ of 0.83 and 1.79 days, respectively.     

Persistence and Dissipation of Quinalphos in/on Cauliflower and Soil Under the Semi Arid Climatic Conditions of Karnataka, India

Persistence and dissipation of quinalphos residues in/on cauliflower was studied after giving spray applications at 2 concentrations, i.e. recommended dose of 500 g a.i. ha^?1 and double the recommended dose of 1,000 g a.i. ha^?1. Residue analysis of cauliflower curds was carried out after the third spray over a period of 15 days. Initial residues of quinalphos on cauliflower from the two treatments were 1.19 and 1.842 mg kg^?1. The residues persisted up to 15 days from both the treatments. The residues of quinalphos dissipated from both treatments with the half-life of 4.8 and 5.3 days. Based on the persistence study and maximum residue limit value of 0.05 mg kg^?1 the safe pre-harvest interval was worked out as 17 and 22 days from treatment at the recommended and double the recommended dose, respectively. Analysis of soil samples was carried out on the 15th day of sampling and residues were found to be 0.013 and 0.044 mg kg^?1.     

Accumulation and Distribution Characteristics of Zinc and Cadmium in the Hyperaccumulator Plant Sedum plumbizincicola

Accumulation and distribution of Zn and Cd in the hyperaccumulator plant Sedum plumbizincicola were investigated in a hydroponic experiment. Mean Cd and Zn concentrations in shoots (7,010 and 18,400 mg kg^?1) were about sevenfold and fivefold higher than those in roots (840 and 3,000 mg kg^?1) after exposure to 100 μM CdSO₄ and 600 μM ZnSO₄, respectively. Cd and Zn concentrations in young leaves (4,330 and 9,820 mg kg^?1) were about sixfold and twofold higher than those in mature leaves (636 and 2,620 mg kg^?1), respectively. MicroPIXE analysis showed that Zn was predominantly localized in epidermal cells in both young and mature leaves, but large amounts of Zn occurred in mesophyll cells in young leaves. Leaf tissue fractionation showed that soluble and cell wall fractions were different at the two stages of leaf growth. Young and mature leaves of S. plumbizincicola also showed different accumulation and distribution characteristics for Zn and Cd.     

Biodegradation of Imidacloprid by Consortium of Two Soil Isolated Bacillus sp.

Imidacloprid degradation potential of bacterial cultures from sugarcane growing soils was studied in liquid culture and Bacillus aerophilus and Bacillus alkalinitrilicus showed maximum potential to degrade imidacloprid. Hence, into a clay loam soil imidacloprid was added at 50, 100, and 150 mg kg^?1 along with 45 × 10⁷ cells g^?1 soil of both species under autoclaved and unautoclaved conditions. Under autoclaved conditions imidacloprid residues were degraded after 56 days to 3.18, 5.83 and 10.48 mg kg^?1 and under unautoclaved conditions to 5.17, 6.23 and 10.31 mg kg^?1. 6-chloronicotinic acid, nitrosimine and imidacloprid-NTG metabolites were detected in measurable concentrations under both conditions. Dissipation pattern of imidacloprid did not follow first order kinetics under both sets of conditions. The half life value of imidacloprid ranged from 13 to 16 days after bacterial inoculation. This is first report of use of mixed culture of native soil bacterial isolates for remediation of imidacloprid contaminated soils.     

Concentrations of Arsenic and Boron in Water,Sediment and the Tissues of Fish in Emet Stream (Turkey)

In this study, the concentrations of arsenic and boron were determined in the water and the sediment, as well as in the muscle tissues of Squalius cephalus, Alburnoides bipunctatus, Barbus plebejus and Capoeta tinca from Emet Stream. The fish samples were caught in May 2011 and September 2012. The metal concentrations in the water samples were as follows: arsenic was 137.1–1002 µg L^?1, and boron was 2421–14490 µg L^?1. The metal concentrations in the sediment samples were as follows: arsenic was 14.51–3317.1 mg kg^?1, and boron was 14.22–1014.01 mg kg^?1. The mean tissue concentration of arsenic was lower than the TFC and WHO limits. Boron has been identified in fish tissues at concentrations between 0.26 and 2.96 mg kg^?1. The bioaccumulation in the muscle tissues of all fish species caught from Emet Stream did not exceed the limit values.     

Arsenic Toxicity on Ludwigia octovalvis in Spiked Sand

Wilting, especially of the leaves, was observed as an initial symptom of arsenate [As(V)] to Ludwigia octovalvis (Jacq.) P. H. Raven. The plants tolerated As(V) levels of 39 mg kg^?1 for as long as 35 days of exposure. After 91 days, the maximum concentration of As uptake in the plant occurred at As(V) concentration of 65 mg kg^?1 while As concentration in the stems, roots and leaves were 6139.9 ± 829.5, 1284.5 ± 242.9 and 1126.1 ± 117.2 mg kg^?1, respectively. In conclusion, As(V) could cause toxic effects in L. octovalvis and the plants could uptake and accumulate As in plant tissues.     

Tungsten (W) bioavailability in paddy rice soils and its accumulation in rice (Oryza sativa)

The aim of this study was to investigate the accumulation characteristics of tungsten (W) by different indica rice cultivars from the soil and to assess the potential risks to human health via dietary intake of W in rice consumption. A total of 153 rice (ear) samples of 15 cultivars and the corresponding surface soil samples were collected from 7 cities in Fujian Province of southeastern China. The available soil W were extracted using H₂C₂O₄·2H₂O-(NH₄)₂C₂O₄·H₂O at pH 3.3). Results showed that the total soil W ranged from 2.03 mg kg^?1 to 15.34 mg kg^?1 and available soil W ranged from 0.03 mg kg^?1 to 1.61 mg kg^?1. The W concentration in brown rice varied from 7 μg kg^?1 to 283 μg kg^?1 and was significantly correlated with the available soil W. The highest mean TF_avail (transfer factor based on available soil W) was 0.91 for Te-you 627 (hybrid, indica rice), whereas the lowest was 0.08 for Yi-you 673 (hybrid, indica rice). The TF_avail decreased with the increase in available soil W, clay content, and cation exchange capacity. The consumption of the brown rice produced from the investigated areas in some cultivars by the present study may cause risks to human health.     

Exposure Assessment to Glyphosate of Two Species of Annelids

Adult mortality, biomass, fecundity and viability of cocoons were studied in Eisenia fetida and Octolasion tyrtaeum, in response to glyphosate exposure in soil. Exposure tests were carried out following USEPA procedure, with five concentrations of glyphosate in soil and a control. O. tyrtaeum was more sensitive to the highest concentration of glyphosate (50,000 mg kg^?1), with 100 % mortality by day 7 of exposure, compared with 71 % for E. fetida. Although biomass of O. tyrtaeum was significantly different between the control and 5,000 mg kg^?1 dose at day 14, E. fetida was not affected at that concentration, and only showed a significant weight loss after 7 days of exposure to 50,000 mg kg^?1. Adverse effects upon adult fecundity and cocoon viability were observed at glyphosate concentrations of 5,000 mg kg^?1 and above. Adverse effects were observed at concentrations that greatly exceeded the recommended field application rates of glyphosate.     

Identification of Heavy Metal Pollution Derived From Traffic in Roadside Soil Using Magnetic Susceptibility

The study integrates surface and vertical distribution of magnetic susceptibility and heavy metal contents (Pb, Cu, Zn and Fe) to characterize the signature of vehicle pollutants in roadside soils at Linfen city, China. Sites with reforestation and without vegetation cover were investigated. The results showed that magnetic susceptibility and heavy metal contents were higher at the roadside without trees than in the reforest belt. The variations of magnetic susceptibility and heavy metal contents decreased both with distance and with depth. The maximum value was observed at 5–10 m away from the roadside edge. The vertical distribution in soil revealed accumulation of pollutants in 0–5 cm topsoils. The average contents were higher than the background values and in the order Fe (107.21 g kg^?1), Zn (99.72 mg kg^?1), Pb (90.99 mg kg^?1), Cu (36.14 mg kg^?1). Coarse multi domain grains were identified as the dominating magnetic particles. Multivariate statistical and SEM/EDX analyses suggested that the heavy metals derived from traffic sources. Trees act as efficient receptors and green barrier, which can reduce vehicle derived pollution.     

Concentration and Bioaccumulation of Cyanobacterial Bioactive and Odorous Metabolites Occurred in a Large,Shallow Chinese Lake

The distributions of cyanobacterial bioactive and odorous metabolites were investigated in the fifth largest lake in China in the fishing season 2012. The highest microcystins (MCs) concentration in water reached 3.4 µg L^?1. A high β-ionone concentration reached 35.6 ng L^?1 in water. Mean MCs concentration in muscle was highest in omnivorous Carassius auratus (20.9 ng g^?1 dry weight), followed by phytoplanktivorous Hypophthalmichthys molitrix (7.4 ng g^?1 DW) and carnivorous Coilia ectenes (3.0 ng g^?1 DW). The maximum off-flavor concentrations kept 9.5 µg kg^?1 wet weight for geosmin (C. auratus), 5.5 µg kg^?1 WW for β-cyclocitral (C. ectenes) and 25.5 µg kg^?1 WW for β-ionone (C. ectenes). Positive correlation was found between the off-flavor and fat contents in C. ectenes. To be different with MCs, β-cyclocitral content was highest in fore-gut contents (87.6 µg kg^?1 WW) in H. molitrix. It should not be reliable to predict odorous compounds level in fish muscle by only measuring the off-flavor in lake water only.     

Modelling the Long-Term Fate of Mercury in a Lowland Tidal River. II. Calibration and Comparison of Two Models with Field Data

This study presents results of the application of two-one-dimensional/dynamic-deterministic models developed to evaluate and predict mercury contamination of a lowland river, the River Yare, Norfolk, UK. As a general indication of model performance, MODEL 1 produced a prediction of the overall mass balance of mercury in the River Yare that was 6% lower than an estimate, based on measurements, and 10% lower than the prediction provided by MODEL 2. The mercury surficial sediment concentrations calculated by MODEL 1 varied from 0.46 mg kg^?1 in 1995 (Reach 3) to 3.55 mg kg^?1 in 1986 (Reaches 6 and 7), whereas the minimum mercury concentration calculated by MODEL 2 was 0.42 mg kg^?1 in 1995 (Reach 3) and the maximum was 8.45 mg kg^?1 in 1986 (Reach 5). Average mercury concentrations experimentally measured in surficial sediments ranged from 0.47 mg kg^?1 in 1995 (Reach 3) to 8.10 mg kg^?1 in 1986 (Reach 6). MODEL 2 gave an excellent prediction of mercury in fish flesh compared with the results obtained from the actual analysis of fish flesh. Both models demonstrated good ability to simulate actual values determined for all compartments, water, surficial sediments, bottom sediments, and fish.     

Persistence Behaviour of Fungicide Tebuconazole in a Viticulture Application

Dissipation pattern and risk assessment of tebuconazole in grapes was studied following two application rates (250 and 500 mL ha^?1) under tropical humid climatic condition of West Bengal during 2009–2010. Residues of tebuconazole were confirmed by liquid chromatography–mass spectrometry. The average recoveries were found 87.53 % and 89.67 % for grapes and cropped soil respectively. Following the first order kinetics the fungicide dissipates in grapes with a half-life (T_1/2) value ranges between 2.62 and 2.86 days irrespective of seasons and doses. No residues of tebuconazole were detected in harvest grapes and soil samples which refers that, tebuconazole does not possess any background contamination property in grapes. So it may be concluded from the study that tebuconazole does not possess any toxicological property when applied at the recommended dose.     

Persistence Behaviour of Thiacloprid Residues in/on Green Tea Leaves,Processed Tea and Tea Infusion

Thiacloprid residues were estimated in green tea leaves, processed tea and tea infusion by HPLC-Diode Array detection. The average initial deposits of thiacloprid (Alanto 240 SC) on the green tea leaves were found to be 3.72 and 6.77 μg g^?1 at single and double doses, respectively. The results showed that thiacloprid dissipated faster in green tea leaves following a first order reaction kinetics at both application rates. The amount of dissipation in 14 days was 93.37 % and 91.62 % for single and double doses respectively. Half life (T_1/2) for degradation of thiacloprid in green tea leaves were observed to be 3.34 and 3.58 days at single and double doses respectively. Thiacloprid residues in processed tea ranged from 0.16 to 0.63 μg g^?1 on seventh day and no residues could be detected on 14th day at single dose. Infusion study indicated that thiacloprid did not infuse into tea liquor from processed tea. The limit of determination was found to be 0.05 μg g^?1.