Effect of Fe (III) on acid degradation of methylparathion
A study was undertaken to determine the transformation kinetic of methylparathion (O, O, -dimethyl O-4 nitrophenylphosphorotioate) in the presence of Fe(III) between pH 2 and 7. The Fe(III) was not electroactive under the conditions used in this study, and polarographic signals were exhibited by methylparathion and main degradation product only. Data suggest that hydrolysis of methylparathion in an acid medium is catalyzed by Fe(III) and the pesticide did not degrade in this medium without this cation. Methylparathion degradation was observed at all the pHs studied and was independent of the predominant chemical form of Fe(III) in the aqueous medium. The reaction was first-order with pH-dependent rate constant (k) values ranging from 3.3 × 10− 3 h− 1 to 7.0 × 10− 3 h− 1. The k values increased as pH decreased, suggesting that Fe(III) acted as an electrophile in the reaction mechanism.
Scotland's Rural College Kinetic Study of the Biodegradation of Acephate by Indigenous Soil Bacterial Isolates in the Presence of Humic Acid and Metal Ions
Many bacteria have the potential to use specific pesticides as a source of carbon, phosphorous, nitrogen and sulphur. Acephate degradation by microbes is considered to be a safe and effective method. The overall aim of the present study was to identify acephate biodegrading microorganisms and to investigate the degradation rates of acephate under the stress of humic acid and most common metal ions Fe(III) and copper Cu(II). Pseudomonas azotoformanss strain ACP1, Pseudomonas aeruginosa strain ACP2, and Pseudomonas putida ACP3 were isolated from acephate contaminated soils. Acephate of concentration 100 ppm was incubated with separate strain inoculums and periodic samples were drawn for UV—visible, FTIR (Fourier-transform infrared spectroscopy) and MS (Mass Spectrometry) analysis. Methamidophos, S-methyl O-hydrogen phosphorothioamidate, phosphenothioic S-acid, and phosphenamide were the major metabolites formed during the degradation of acephate. The rate of degradation was applied using pseudo-first-order kinetics to calculate the half-life (t1/2) values, which were 14.33–16.72 d−1 (strain(s) + acephate), 18.81–21.50 d−1 (strain(s) + acephate + Cu(II)), 20.06 –23.15 d−1 (strain(s) + acephate + Fe(II)), and 15.05–17.70 d−1 (strains + acephate + HA). The biodegradation efficiency of the three bacterial strains can be ordered as P. aeruginosa > P. putida > P. azotoformans. The present study illustrated the decomposition mechanism of acephate under different conditions, and the same may be applied to the removal of other xenobiotic compounds.
Intoxicación aguda por plaguicidas
Objective. To describe the epidemiologic pattern of acute pesticide poisoning (APP) in a general hospital in Merida, Yucatan, Mexico. Material and methods. From 1994 to 1998, 33 patients 13 years of age or older with diagnosis of APP were studied. Descriptive statistics were used to analyze information. Results. Males were frequently affected (82%), specially those coming from rural areas (60%). The mean age of the group was 34 ± 15.8 years. In 79% of the cases, pesticides were used to commit suicide and 33% of poisoning cases were due to organophospate pesticides. The mortality rate was 12%. Conclusions. In this small sample, acute poisoning from pesticides in the agricultural setting may be underestimated, since it was less frequent than in the general population. APP was more commonly used by indigent people to commit suicide.