Background. Mancozeb belongs to a group of pesticides known as dithiocarbamates (DTC) that are a non-systemic group of pesticides extensively used in Uganda to protect crops from fungal diseases. Objectives. This study was done in 5 selected districts of Central Uganda with a focus on markets and farms to investigate the current mancozeb concentrations on tomatoes and identify key areas of improvement to minimize human exposure. Methods. Tomato samples were analyzed for mancozeb residue determined as carbon disulfide (CS 2) by gas chromatography-mass spectrometer (GC-MS). Results. All the samples analyzed had detectable concentrations of mancozeb residue. It was observed that farm samples had mean concentrations of 1.03±0.28 mg/kg, while market samples had 0.77±0.49 mg/kg. The study also found that farmers applied 3-6 times the dosage of mancozeb recommended by manufacturers. Furthermore, the observed pre-harvest interval after application of mancozeb was 1-2 days as opposed to 3-7 days set by manufacturers. Conclusions. The observed practices at farms are likely to put farmers and final consumers at a risk of exposure to dithiocarbamates.
Ash (Fraxinus) wood sawdust pyrolysis under nitrogen was conducted using 2, 5, 10, 15 and 20 o C/min heating rates. Friedman and Starink methods were used for kinetic analysis while y(α) master plots were used for pyrolysis mechanisms prediction. The mean activation energy were 198 and 202 kJ/mol for Friedman and Starink respectively. The master plots predicted that the pyrolysis process could be a combination of diffusion, geometrical contraction, nucleation, and reaction order models. The pre-exponential factors were in the range 10 12 to 10 19 s-1. Gibbs free energy was 180-185 kJ/mol. The entropy values were negative up to α = 0.75 indicating high orderliness of products relative to reactants but changed to positive at higher conversions implying likely disorderliness of the products compared to reactants. The calorific value of Ash (Fraxinus) wood sawdust was 18.3MJ/kg.
Carbon monoxide (CO) from the use of biomass solid fuels has caused several fatalities in the United Kingdom. This study was undertaken to evaluate the amount of CO from five species of wood sawdust, and charcoal with a case study of CO in a confined ISO container. Laboratory experiments were conducted at temperatures between 350 and 600 o C under flowing air. Results showed a strong dependence of CO emissions on temperature and airflow. Sawdust emitted CO levels as high as 298 mg/g while charcoal released 495 mg/g as highest. The CO emissions recorded in the ISO container were above the recommended exposure limits due to poor ventilation.
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