Sankhajit Roy

Degradation dynamics of alachlor in maize ecosystem

Alachlor (CAS No. 15972-60-8) was developed by Monsanto Company (USA) and introduced in 1967 for pre-emergence or pre-plant control of broad spectrum of grass, sedge and broad-leaf weeds in corn, soybeans, dry beans, cotton, grain sorghum, sunflowers, peanuts and other crops. Ramesh et al. (2002) investigated the dissipation of alachlor in soil and plant in field condition (cotton cropping system), and in soil, water and fish in simulated model ecosystem. At harvest, cotton lint and seed samples were found to contain alachlor well below the detectable level. However, trace amounts of residues were found in cotton oil. The green leafy vegetable samples did not show any toxic symptoms of alachlor residues. The objectives of this research are the concise enumeration of the gas-liquid chromatographic (GC-ECD) separation methods used for the determination of residual fate, dissipation pattern and degradation behaviour of alachlor in maize crop and in its soil substrates.

PERSISTENCE OF CHLORFLUAZURON IN CABBAGE UNDER DIFFERENT AGRO-CLIMATIC CONDITIONS OF INDIA AND ITS RISK ASSESSMENT

A multilocational field trial was conducted at 4 locations in India-Rajasthan, Gujarat, Madhya Pradesh, and West Bengal-to determine the persistence in cabbage of chlorfluazuron applied twice at 75 and 150 g active ingredient ha-1 . Cabbage head samples were collected from each replicated plot on 0 (2 h after spraying), 1, 3, 5, 7, 10, and 15 d after final insecticide application, including an untreated control. Chlorfluazuron residue in cabbage and field soil was estimated by high-performance liquid chromatography using a photo diode array detector. The limit of determination and limit of quantification of the method were recorded as 0.05 and 0.10 μg g-1 , respectively. Results revealed that chlorfluazuron dissipated linearly with progress of time, following first-order kinetics. The mean (± standard deviation) half-life value of chlorfluazuron in cabbage was found to be 7.18 ± 0.71 d, considering different locations and treatments. The residue was below the level of quantification in the harvested cabbage and soil samples. Harvesting cabbage in the experimental location, at least on day 7, after 2 applications of chlorfluazuron at the recommended dose, may not pose any ill effect for Indian adults. Environ Toxicol Chem 2017;36:3028-3033.

Photodegradation of Oryzalin in aqueous isopropanol and acetonitrile.

ABSTRACT The phototransformation of Oryzalin was studied under UV light (λmax ≥ 290 nm) and sunlight (λmax ≥ 250 nm) in aqueous isopropanol and acetonitrile solution in absence and presence of TiO2 as sensitizer. The rate of photodegradation of Oryzalin in different solvent system followed first-order kinetics, and calculated half-lives were found to be in the range of 23.52-53.75 h for UV light and 41.23-61.43 h for sunlight. From this study, total 12 photoproducts were identified and characterized on the basis of column chromatography and Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved was hydrolysis, breaking of sulfonic bond, and loss of amino and sulfonic acid group.