Widely-used Herbicide Research Articles

Mineralization of 17β-estradiol in 36 surface soils from Alberta, Canada

Recent column studies suggest that pesticide fate models could be used to estimate the fate of estrogens in soil. Estrogens are detected in livestock manure which is used as a nutrient source on agricultural land. This is the first study to examine estrogen mineralization in a wide range of agricultural soils at the regional-scale. Soil samples were collected from upper and lower landscape positions of 18 agricultural fields in an area spanning 49–60°N longitude and 110–120°W latitude and these samples were used to determine 17β-estradiol mineralization parameters in microcosm experiments. Maximum 17β-estradiol mineralization (Max) ranged from 5.8% to 19.2% and was, on average, significantly (P<0.05) less than the 47.9–61.9% range measured in the same soils for the widely-used herbicide 2,4-D (2,4-dichlorophenoxyacetic acid). Maximum 17β-estradiol mineralization was positively correlated to Kd-17β-estradiol (r=0.62, P<0.001) while 2,4-D maximum mineralization was negatively correlated to Kd-2,4-D (r=−0.52, P<0.01), even though 17β-estradiol and 2,4-D sorption parameters (Kd) were positively correlated (r=0.62, P<0.001), and both Kd-17β-estradiol and Kd-2,4-D values were significantly positively correlated to SOC (r=0.71, P<0.001; and r=0.67, P<0.001, respectively). Hence, the mineralization of 2,4-D decreases as its sorption to soils increases while the mineralization of 17β-estradiol increases as its sorption to soil increases. This suggests that some steps in the 17β-estradiol mineralization process are occurring in the sorbed phase. Equations to predict 17β-estradiol and 2,4-D sorption and mineralization parameters were established using Partial Least Squares regression. Significant models for mineralization (r2 from 0.42 to 0.56) had lower r2 than significant sorption models (r2 from 0.78 to 0.85). Given the poor results of the mineralization regression models, we conclude that probability density functions, rather than regression models, are likely to be more useful for describing pesticide or estrogen mineralization parameters at the regional scale. Based on our findings, agri-environmental policy-analysis in Alberta should use the log–logistic probability density function to describe the mineralization rate (k) of either 17β-estradiol or 2,4-D at the large-scale. Max-17β-estradiol at the large-scale is best described by the extreme values probability density function and Max-2,4-D by the triangular probability density function.

Fluroxypyr triggers oxidative damage by producing superoxide and hydrogen peroxide in rice (Oryza sativa)

The present study has evaluated effect of fluroxypyr concentrations 0-0.8 mg l(-1) (a widely-used herbicide for controlling annual or perennial weeds growth) on selected metabolic and stress-related parameters in Oryza sativa plants after 6 days of exposure. Increasing concentrations decreased shoot growth and accumulation of chlorophylls but had no effect on root biomass. Increasing doses led also to increase in superoxide radical, hydrogen peroxide and proline accumulation, while malondialdehyde, an indicator of lipid peroxidation, was constitutively elevated. Histochemical staining with nitroblue tetrazolium and 3, 3-diaminobenzidine were positively correlated with the generation of superoxide radical and H(2)O(2). The fluroxypyr-induced oxidative stress triggered significant changes in activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase (POD). Activities of the antioxidant enzymes show a general increase at low fluroxypyr concentrations and a decrease at high fluroxypyr levels (except for POD). Analysis of naturing polyacrylamide gel electrophoresis confirmed these results. These data support the observation that fluroxypyr-triggered oxidative stress was responsible for the disturbance of the growth in the rice plants.

Protective effects of a new metalloporphyrin on paraquat-induced oxidative stress and apoptosis in N27 cells

Paraquat (PQ, 1,1'-dimethyl-4,4'-bipyridinium), a widely-used herbicide, has been suggested as a potential etiologic factor for the development of Parkinson's disease. In recent years, many studies have focused on the mechanism(s) of PQ neurotoxicity. In this study, we examined the neuroprotective effect of manganese (III) meso-tetrakis (N,N'-diethylimidazolium) porphyrin (MnTDM), a superoxide dismutase/catalase mimetic, on PQ-induced oxidative stress and apoptosis in 1RB3AN27 (N27) cells, a dopaminergic neuronal cell line. The results indicated that MnTDM significantly attenuated PQ-induced loss of cell viability, glutathione depletion, and reactive oxygen species production. MnTDM also ameliorated PQ-induced morphological nuclear changes of apoptosis and increased rates of apoptosis. In addition, our data provide direct evidence that MnTDM suppressed PQ-induced caspase-3 cleavage, possibly a key event of PQ neurotoxicity. These observations suggested that oxidative stress and apoptosis are implicated in PQ-induced neurotoxicity and this toxicity could be prevented by MnTDM. These findings also proposed a novel therapeutic approach for Parkinson's disease and other disorders associated with oxidative stress.

Fluorescence characterization of the interaction of Al 3+ and Pd 2+ with Suwannee River fulvic acid in the absence and presence of the herbicide 2,4-dichlorophenoxyacetic acid

In an effort to understand the role of environmental metal ions in the interaction of charged pesticides with humic substances, a fluorescence study of the interaction of the widely-used herbicide 2,4-dichlorophenoxyacetic acid (DCPAA) with Al 3+ and Pd 2+ and Suwannee River fulvic acid (SRFA) was undertaken. Initial fluorescence experiments on binary solutions clearly indicated that both Al 3+ and Pd 2+ strongly interact with both SRFA and DCPAA when alone in solution with the metal ion. Titrations of SRFA with Al 3+ at pH values of 4.0, 3.0 and 2.0 revealed decreased degrees of fluorescence emission enhancement (at λ emission, max=424 nm) with decreasing pH, consistent with the expected loss of rigidity in the SRFA–Al 3+ complexes formed as pH is lowered. In contrast, titrations of SRFA with Pd 2+ at all of these pH values resulted in significant fluorescence quenching. Al 3+ additions to solutions of DCPAA at pH values above the p K a (2.64) of DCPAA resulted primarily in significant changes in the wavelength of maximum emission (without significant quenching or enhancement of emission intensity), while Pd 2+ additions to DCPAA solutions resulted primarily in very significant fluorescence quenching. The DCPAA fluorescence results strongly support the formation of an Al 3+–DCPAA complex at pH values above the p K a of DCPAA. The fluorescence results obtained for solutions of Pd 2+ and DCPAA are best explained by a collisional quenching mechanism, that is, energy transfer from excited DCPAA molecules to Pd 2+ following the collision of these two species in solution. Excitation–emission matrix plots obtained on ternary solutions (at environmentally-relevant pH 4.0) containing SRFA, DCPAA and metal ions (i.e., either Al 3+ or Pd 2+) provides evidence (especially for systems containing Al 3+) for the existence of ternary complexes between fulvic acid species, the herbicide DCPAA and metal ion, suggesting (at least at pH 4.0, where the predominant DCPAA species is negatively-charged) that metal ions may function to “bridge” negatively-charged fulvic acids to negatively-charged pesticides.

Quantitative nuclear magnetic resonance spectrometry: II. Purity of phosphorus-based agrochemicals glyphosate ( N-(phosphonomethyl)-glycine) and profenofos ( O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate) measured by 1H and 31P QNMR spectrometry

The purities of the widely-used herbicide glyphosate ( N-(phosphonomethyl)glycine), and the insecticide profenofos ( O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate) were determined by 1 H and 31 P quantitative nuclear magnetic resonance (QNMR) spectrometry using an internal standard. QNMR does not need a standard reference of the same target analyte, in contrast to chromatographic methods, but only a compound containing the nucleus of interest. Sodium acetate and sodium phosphate of known purity were chosen as internal standards for 1 H NMR and 31 P NMR), respectively for the water soluble glyphosate and a single internal standard, trimethyl phosphate for both 1 H and 31 P NMR quantitative analysis of the organic soluble profenofos. These standards have NMR peaks that do not interfere with those of the analyte, they are chemically inert and are soluble in the deuterated solvent. The average purity of glyphosate obtained by 1 H NMR (97.07%, σ=0.68) agreed with that by 31 P NMR (96.53%, σ=0.90; ANOVA, P=0.074) for the five batches provided by the manufacturer according to the procedures for chemical registration in Australia. The standard deviations of seven independent analyses of a single batch by 1 H NMR and 31 P NMR were σ=0.24% and σ=0.33%, respectively, values which confirm the exceptional precision of the method. The purity of profenofos by 1 H NMR (94.63%, σ=0.14) also agreed with that by 31 P NMR (94.62%, σ=0.59; ANOVA, P=0.97). Uncertainty budgets for the measured purities of glyphosate and profenofos show that the uncertainty in the purity of the internal standard is a major contributor to the uncertainty of the result. NMR was also used to establish the impurity profile of both compounds, and quantify the impurities present.