[show abstract][hide abstract] ABSTRACT: Experiments were conducted to determine the fate of bensulfuron-methyl (BSM) and imazosulfuron (IMS) under paddy conditions.
Initially, laboratory experiments were conducted and the photolysis half-lives of the two herbicides were found to be much
shorter than their hydrolysis half-lives in aqueous solutions. In the aerobic water–soil system, dissipation followed first-order
kinetics with water half-lives of 9.1 and 11.0days and soil half-lives of 12.4 and 18.5 days (first phase) and 35.0 and 44.1
days (second phase) for bensulfuron-methyl and imazosulfuron, respectively. However, the anaerobic soil half-lives were only
12.7 and 9.8days for BSM and IMS, respectively. The values of K
d were determined to be 16.0 and 13.8 for BSM and IMS, respectively. Subsequent field measurements for the two herbicides revealed
that dissipation of both herbicides in paddy water involved biphasic first-order kinetics, with the dissipation rates in the
first phase being much faster than those in the second phase. The dissipation of bensulfuron-methyl and imazosulfuron in the
paddy surface soil were also followed biphasic first-order kinetics. These results were then used as input parameters for
the PCPF-1 model to simulate the fate and transport of BSM and IMS in the paddy environment (water and 1-cm surface soil layer).
The measured and simulated values agreed well and the mass balance error during the simulation period was −1.2 and 2.8% of
applied pesticide, respectively, for BSM and IMS.
KeywordsDissipation–Sulfonylureas–Photolysis–Biphasic first-order kinetic–Model simulation
Paddy and Water Environment 01/2012; · 1.03 Impact Factor
[show abstract][hide abstract] ABSTRACT: Diphenylarsinic acid, phenylarsonic acid, methylphenylarsinic acid (MPAA), dimethylphenylarsine oxide (DMPAO), and methyldiphenylarsine oxide (MDPAO) in soil and rice were extracted, separated by reversed-phase chromatography, and quantified by ICPMS with a membrane desolvating system. For the extraction of arsenicals from rice grain and straw, 68% HNO3 provided better extraction efficiency than water, 50% methanol, or 2.0 mol L(-1) trifluoroacetic acid. For the extraction from soil, 68% HNO3 provided better extraction efficiency than H2O, 1 mol L(-1) H3PO4, or 1 mol L(-1) NaOH. The contaminated soil contained all five aromatic arsenicals along with inorganic arsenicals as main species (5.86 +/- 0.19 microg of As kg(-1): 60.8 +/- 2.0% of total extracted As). After pot experiments, rice straw contained mainly DMPAO (7.71 +/- 0.48 microg of As kg(-1): 60.5 +/- 3.7%), MDPAO (0.91 +/- 0.07 microg of As kg(-1): 7.2 +/- 0.5%), and inorganic As (2.85 +/- 0.20 microg of As kg(-1): 22.3 +/- 1.6%). On the other hand, rice grain contained mainly MPAA (1.17 +/- 0.04 microg of As kg(-1): 86.7 +/- 2.7%). The root uptake of each species from the soil and transport from straw to grains were significantly related to the calculated log K(ow) values.
[show abstract][hide abstract] ABSTRACT: The cholinesterase (ChE)-inhibiting activity of water and the concentrations of representative inhibitors were monitored in the Tone canal, Japan, during April to December 2006. The ChE-inhibiting activity, measured by using horse serum as enzyme source, increased from late April to early June, and from September to October. Although the trends in the ChE-inhibiting activity of the samples were consistent with concentration changes of organophosphorus pesticides, ChE-inhibiting activity was not observed in samples replicated on the basis of the chemical concentrations detected. The water samples were treated with chlorine to enhance the ChE-inhibiting activity by conversion of thiophosphate pesticides to phosphate pesticides. The ChE-inhibiting activity increased in almost all the chlorine-treated samples, although organophosphorus pesticides were either not detected or detected in traces in the samples by gas chromatographic-mass spectrometric analysis. These results suggested that assay of ChE-inhibiting activity is important for evaluating the ecotoxicity of environmental water, because toxicological investigations based solely on inhibitor concentrations may underestimate the contamination. Furthermore, the combined method of oxidation by chlorination and the ChE assay is very effective for screening and monitoring of organophosphorus pesticides in environmental water.
[show abstract][hide abstract] ABSTRACT: We found that aquatic crustaceans, decapoda; atyidae (Caridina multidentata, Neocaridina denticulate, and Paratya compressa), metabolize pyrene to a new conjugation product. The results of deconjugation treatments indicated that glucose and sulfate combined with 1-hydroxypyrene. Further analysis by LC/ESI-MS/MS showed that the molecular weight of the product was 460 (m/z 459; deprotonated ion), and that it has a glucose-sulfate moiety (m/z 241; fragment ion). These results indicated that the new metabolite was the glucose-sulfate conjugate of 1-hydroxypyrene. The glucose-sulfate conjugate is a phase II product that has not been reported previously from any organism. Several studies have demonstrated that sulfation is an important pathway for metabolism of xenobiotics in aquatic invertebrates. Thus, glucose-sulfate conjugates may add an important signal for excretion or sequestration of xenobiotics for aquatic invertebrates.
Biochemical and Biophysical Research Communications 09/2007; 360(2):490-5. · 2.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: The objective of this study was to clarify the adsorption and desorption characteristics of several herbicides in sediment. Five herbicides, esprocarb, thiobencarb, dimethametryn, pretilachlor, and simetryn were examined in this study. The adsorption ratio on the sediment increased in the following order: pretilachlor < dimethametryn < simetryn < thiobencarb < esprocarb. On the other hand, the adsorption ratio on the sediment without organic matter increased in the following order: thiobencarb < esprocarb < pretilachlor < dimethametryn < simetryn. Furthermore, the amounts of simetryn, dimethametryn, and pretilachlor adsorbed on the sediment without organic matter increased, while those of esprocarb and thiobencarb decreased in comparison to the original sediment. These results strongly suggested that the mineral surface in the sediment was very important as the adsorption site for the herbicide, especially in the case of simetryn, dimethametryn, and pretilachlor. All the adsorption and desorption data fitted well with the Freundlich equation. The hysteresis in the adsorption-desorption phenomena in the sediment was observed for all the herbicides, and it was affected by the organic matter in sediment, especially in the case of dimethametryn and pretilachlor.
Journal of Environmental Science and Health Part B 02/2007; 42(1):1-8. · 1.21 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aquatic crustacean Daphnia magna is an important species for ecotoxicological study, and is often used as a test organism for environmental risk assessment. However, the mechanism of xenobiotic metabolism by this species has not been studied in detail. In the present study, pyrene was used as model substance to investigate the mechanism of xenobiotic metabolism in D. magna. The results of 24-h exposure experiments showed that D. magna could metabolize pyrene and biotransform it into water-soluble metabolites. On the other hand, the metabolism of pyrene was significantly inhibited by SKF-525A as the cytochrome P450 (CYP) inhibitor. These observations indicated that oxidation by CYP participated in the biotransformation of pyrene by D. magna. We also identified the pyrene metabolites formed by D. magna by HPLC with an electrospray ionization triple quadrupole mass spectrometry detector (LC/ESIMS/MS) and de-conjugation by sulfatase, beta-glucuronidase, and beta-glucosidase. One of the metabolites was ionized in ESI negative mode and formed a dominant mass of m/z 297 (MS) with the product ion of m/z 217 (MS2). Furthermore, this metabolite formed 1-hydroxypyrene on treatment with sulfatase. This metabolite was considered to be a sulfate conjugate of oxidized pyrene (1-hydroxypyrenesulfate). Furthermore, we quantified the deconjugated 1-hydroxypyrene formed by the above enzyme treatment. It showed that 52% of the total metabolized pyrene was biotransformed into 1-hydroxypyrene-sulfate, and more than 73% was biotransformed into oxidized pyrene conjugate. These results indicated that CYP and several conjugation enzymes participate in its biotransformation, and sulfation is important in D. magna for metabolism and elimination of xenobiotics.
[show abstract][hide abstract] ABSTRACT: This work describes the analytical performance of the enzyme-linked immunosorbent assay (ELISA) for the fungicide chlorothalonil to effectively exploit as a simple and rapid detection system for pesticide residue on the scenes of the agricultural production and distribution. This ELISA represents the satisfactory analytical characteristics (I50 value, 0.34 ng/g; limit of detection, 0.052 ng/g) to detect chlorothalonil at the regulatory values or thereabout in a sample. Noticeable cross-reactivities were shown with two fungicides, fthalide (58.8%) and pentachloronitrobenzene (quintozene) (20.0%), and some non-agrochemicals such as tetrachloroterephthalonitrile (96.8%) and tetrachlorophthalonitrile (68.3%). The influence of three organic solvents (methanol, acetone, and acetonitrile) used as extractants for chlorothalonil residue was evaluated, with the result that methanol was the most suitable solvent for the ELISA, and the final concentration in the well could be up to 5% (v/v) without any negative influence on the ELISA. It has been possible to directly analyze chlorothalonil residue only by giving dilution of each sample extract with water prior to the ELISA analysis. The average recovery values from the spiked samples by the ELISA were between 101.7 and 113.6% with the average coefficients of variation between 2.6 and 5.9%. Although the results obtained from the ELISA correlated well with those from the reference GC/MS methods for all agricultural samples (r>0.98), the linear function inclined to the ELISA results because of loss during complex sample preparations for GC/MS analysis. Nevertheless, the results demonstrated that the proposed ELISA is a reliable, cost-effective, and rapid quantitative method for chlorothalonil residue.
Journal of Chromatography 10/2006; 1129(2):273-82. · 4.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: Lolitrems are neurotoxins found in endophyte-infected perennial ryegrass. Lolitrems, primarily lolitrem B, are the causative agents of ryegrass staggers in livestock. To guarantee the safety of meat produced from cattle consuming endophyte-infected perennial ryegrass, lolitrem B concentrations in tissues of Japanese Black cattle were determined using high-performance liquid chromatography. Lolitrem B was not detected in muscle, liver, kidney, or cerebrum of a Japanese Black cow with signs of ryegrass staggers. In contrast, perirenal fat contained 210 ppb lolitrem B. Three cows that received half as much perennial ryegrass straw as the cow with ryegrass staggers showed no clinical signs of ryegrass staggers. However, low concentrations of lolitrem B (less than 150 ppb) were detected in their fat tissue. These observations indicate that human exposure to the neurotoxic effect of lolitrem B through beef is unlikely. The amount of lolitrem B consumed by cattle can be estimated by the determination of lolitrem B in fat tissue.
Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc 08/2004; 16(4):340-2. · 1.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effects of herbicide (mefenacet and pretilachlor) applications on soil microbial communities in rice paddy soil were investigated in a laboratory study using phospholipid fatty acid (PLFA) profiles. Soils with or without herbicide application were incubated separately under oxidative or reductive conditions for 30 d. Half-life (DT50) of mefenacet was 14 d under oxidative conditions and 9.8 d under reductive conditions. DT50 of pretilachlor was 17 d under oxidative conditions and 8.8 d under reductive conditions. PLFA contents did not seem to be affected by the residual levels of herbicides. The composition of PLFAs under in both the oxidative and reductive conditions fluctuated during the incubation period. However, the effects of applications of herbicides (mefenacet and pretilachlor) under oxidative and reductive conditions in rice paddy soil did not affect appreciably the soil microbial biomass and the structure of the soil microbial communities, as determined by PLFA profiles. Fluctuations in the composition of PLFAs during the incubation period were rather conspicuous.
Soil Science and Plant Nutrition. 02/2004; 50(3):349-356.
[show abstract][hide abstract] ABSTRACT: Direct determination of cadmium in rice flour by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is described. This superior quantitative method needs no conventional laborious sample pretreatment such as decomposition and extraction. To construct the calibration line and estimate the detection limit, three certified reference materials for rice flour, NIES nos. 10a, 10b and 10c, were used and contaminated with three different concentrations of cadmium (0.023, 0.32 and 1.82 mg kg−1, respectively). These three kinds of rice flour were finely ground and pressed into disks for analysis. The calibration line showed good linearity in the range 0.023–1.82 mg kg−1. The determination did not require internal standardization and no significant interference was observed.
[show abstract][hide abstract] ABSTRACT: We present evidence that the rice receptor for N-acetylchitooligosaccharide elicitor does not couple to heterotrimeric G-protein (G-protein), one of the most important signal transducers from the cell surface to down-stream effectors in various cellular responses of many organisms. Using mutant rice cells lacking functional G-protein α-subunit, cellular responses of suspension-cultured rice cells derived from Daikoku dwarf (d1) mutants that were shown to contain mutations in the coding region of the G-protein α-subunit (Fujisawa et al. 1999) to N-acetylchitooligosaccharide (oligochitin) elicitor were compared with those of the corresponding parent cell lines. All the elicitor-induced cellular responses, such as medium alkalinization, generation of reactive oxygen species, expression of early responsive genes, PAL and PR genes, and production of phytoalexin, were basically identical in the mutant and wild type cell lines. Considering the reported presence of a single copy gene for the G-protein α-subunit in many plant species including rice, these results strongly support the above conclusion.
Physiologia Plantarum 10/2002; 116(3):373 - 382. · 3.66 Impact Factor