Dr. Joyce Gatiiria Njagi-Kithure

Abstract

This work investigates a possible electrocatalytic degradation of tetrachlorvinphos pesticide in acetonitrile-water media using cyanocobalamin as the catalyst. The catalyst and its derivatives are employed in some organic synthesis due to their ability to form and selectively cleave Co-C bonds. There is inadequate data from previous related works. This study explores possible electrocatalytic route for degradation of tetrachlorvinphos using the catalyst at temperature of 24 ± 1° by cyclic voltammetry method. Tetrachlorvinphos exhibited two consecutive reduction peaks at ~-0.710 ± 0.004 V and ~ -1.096 ± 0.029 V Versus Ag/AgCl. The second reduction peak registered a diffusion coefficient value of 3.68 x 10-5 cm2s-1 and current density of be 5.83 x 10-5 A/cm2. The reduction potential for tetrachlorvinphos in presence of cyanocobalamin was observed to be -0.923 ± 0.03 V versus Ag/AgCl. The diffusion coefficient and current density value was reported at 3.37 x 10-5 cm2s-1 and 2.56 X 10-5 A/cm2 respectively for an electro-reduction process. This implies that, catalytic reduction of the pesticide occurred at a significantly lower potential compared to direct reduction. The over potential saving of about 0.168 V is an indication of the catalyst efficiency on the pesticide degradation.

Description
A study was conducted to estimate current status of physico-chemical characteristics of effluents emanating from three paint factories within the main industrial area of Nairobi County. The effluents were analysed for temperature, pH, oil and grease, total suspended solids (TSS), chemical oxygen demand (COD), total phosphorus, total nitrogen, total sulphur and heavy metal ions and compared to Kenyan effluent discharge standards. The results were as follows: pH 6.48-6.89, temperature 28.07-28.30 oC, COD 916.77-1881.20 mg/L, total phosphorus 145.00-149.32 mg/L, TSS 6382.33-7395.33 mg/L, oil and grease 3525.00-6374.33 mg/L, total sulphur 72.62-73.41 mg/L, total nitrogen 1586.67-4442.67 mg/L. Heavy metal concentrations were 3.03-4.18 mg/L, 2.07-3.04 mg/L and 5.38-17.21 mg/L respectively for cadmium, chromium and lead. Adsorbent was made from waste rubber tyres and tested for its suitability in removing three heavy metal ions namely cadmium, lead and chromium from the effluent samples by varying adsorbent dosage, pH and contact time.

Water covers 70.9% of the Earth's surface (WFB, 2008), and is vital for all known forms of life (WFB, 2008). The specific contaminants leading to pollution in water include a wide spectrum of chemicals like Persistent Organic Pollutant 1(POPs), pesticides and pathogens. Chlorpyrifos is an organophosphate insecticide used to kill variety of insects, especially ticks and was introduced in Kenya in 1965 (Meister, 1992). This study set out to determine the chlorpyrifos concentration residue levels in some selected samples from the upper Tana River, to confirm their state of contamination. Water, sediment and weed samples obtained from the upper Tana River in Kenya were screened for chlorpyrifos and found to be contaminated. The river profile was divided into three sections representing upstream, middle stream and downstream. Water samples were sampled using the amber bottles while the sediment samples were collected by scooping it with a shovel. Weed samples were plucked using hands, while the hard ones were cut with a clean stainless steel knife. The extraction of water samples was done by liquid-liquid partitioning method using dichloromethane, while sediment samples were extracted in acetone and hexane solvents by soxhlet extraction method. The extraction of weed samples was done using an orbital shaker in acetone. The analysis of the pesticides was done using Gas chromatography-mass spectrometer (GC-MS) and the data analysis conducted using Microsoft excel, 2ANOVA and Pearson’s correlation Statistical Package for Social Scientists, (SPSS). Chlorpyrifos mean residue levels found in water samples 3(BDL to 6.73µg/L), were generally higher than those detected in weed samples of BDL-2.57 1.43 µg/kg, while sediment samples had the lowest levels of BDL and 1.43 µg/kg, as shown in Figure 1. The mid-stream samples had higher levels than both the up stream and the down stream, as can be observed in Figure 2, probably due to intense industrialisation and farming activities at the midstream.
- See more at: http://www.open-science-repository.com/dynamics-of-chlorpyrifos-in-water-from-upper-tana-river-in-kenya.html#sthash.EDmUfs2a.dpuf

Abstract Vegetables provide vital minerals and other nutrients to our bodies.
However, pests destroy vegetables. This as lead to rampant use of pesticides on
vegetables in Kenya. The pesticides that are commonly used on vegetables in
Kenya are the pyrethroids which include; deltamethrin, lambda-cyhalothrin and
chismethrin. In this study deltamethrin was analysed in selected vegetables which
include; kales, cabbages and tomatoes during the dry and wet seasons. The
vegetables were bought from some markets in Nairobi city in Kenya.
Deltamethrin residues were extracted from the samples using organic solvents.
The residues were then determined by high performance liquid chromatography
1
(HPLC). The results shows that the deltamethrin mean residue levels ranged
between 0.0700±0.0200 and 0.2000±0.1000 mg/kg during the dry season and
between 0.0080±0.0500 and 0.0400±0.0001 mg/kg during the wet season. The
deltamethrin residue levels were significantly higher during the wet season than
during the wet season in most of the samples.
Keywords: Vegetables, pyrethroids, deltamethrin, residues and HPLC