Mark F. Zaranyika

Nonconventional Methods of Modification of Starch

Publisher Summary This chapter presents the nonconventional methods for the modification of starch. Starch is the most readily available and abundant pure carbohydrate. Native starch forms a complex matrix and water plays an important role in its construction. It is widely accepted that water fills capillaries of the matrix as well as participates in the strengthening of the amylose helices in the granule. The observation indicates that water cooperates with high pressure in causing deterioration of the starch matrix. Simultaneously, the ascending portions of the compressibility curves show that the resistance of the starch matrix toward compression decreases as the volume of added water increases. It is observed that solid starch changes its electrical conductivity on compression. At constant temperature and humidity, there is a positive correlation between the tamping of starch layers in cylinders, containers, and silos and their electrical conductivity. For the irradiation of amylose, it has been shown that the solvent may stabilize the irradiated matrix. As with starch, monosaccharides and oligosaccharides exhibit peculiar behavior in their formation of free radicals on irradiation. It is suggested that the effect of irradiation on starch gels is generally monitored by the changes in viscosity, reducing power, and reaction with iodine.

UPTAKE OF NI, ZN, FE, CO, CR, PB, CU AND CD BY WATER HYACINTH (EICHHORNIA CRASSIPES) IN MUKUVSI AND RIVERS, ZIMBABWE

Abstract The levels of Ni, Zn, Fe, Co, Cr, Pb, Cu and Cd were determined in water hyacinth and water samples collected from Mukuvisi and Manyame rivers in Zimbabwe. Metal concentrations in the plants were much higher than in the water, and bioconcentration factors of 1 to 4 orders of magnitude were obtained depending on the element. In addition the levels of most elements studied were significantly higher in the roots than the tops of the plants.

Uptake of Zn, Co, Fe and Cr by water hyacinth (Eichhornia crassipes) in Lake Chivero, Zimbabwe

Abstract The levels of Zn, Co, Fe, Ni, Cu, Pb and Cr were determined in water hyacinth growing in Lake Chivero, Zimbabwe, as well as in the water of the lake. Except for Ni, for which levels tended to be similar both in the tops and roots of the plant, levels of the other elements studied were significantly higher in the roots than in the tops. The concentrations of the elements in the plants were much higher than those in the water. Concentration factors of up to 33, 1.7 × 102, 7 × 102 and 8.9 × 103 in the tops, and 1.7 × 102, 2.7 × 102, 2 × 103 and 1.5 × 104 in the roots were found for Co, Zn, Cr and Fe, respectively.

Metal-metal interactions in biological systems. Part IV. Freshwater snail Bulinus globosus

The toxicity against title snails of all Al, Cd, Co(II), Cr(III), Cu(II), Fe (III), Mg, Mn(II), Mo(VI), Ni(II), Pb(II), Se(VI), V(V) and Zn ions was checked in 96 h tests in the water of Kariba Lake. Based on the mortality — concentration relationship the toxicity order of the above ions against Bulinus globosus is Cu(II) > Ni(II) > Cd > Pb(II) > Zn > Al > V(V)> Cr(III)> Se(VI) > Fe(III) =Co(II)> Mn(II) > Mg > Mo(VI). Only Mg, Pb(II), Cu(II), Cd, Zn and Ni(II) ions are harmful to these snails as their mortality is observed at the naturally occuring concentrations. Other metal ions cause lethality at naturally unrealistic concentrations. The following pairs of metal ions were also checked for mutual interactions: Cd-Al, Cd-Co, Cd-Cr, Cd-Cu, Cd-Fe, Cd-Mg, Cd-Mn, Cd-Mo, Cd-Ni, Cd-Pb, Cd-Se, Cd-V, Cd-Zn, Cu-Al, Cu-Co, Cu-Cr, Cu-Fe, Cu-Mg, Cu-Mn, Cu-Mo, Cu-Ni, Cu-Pb, Cu-Se, Cu-V, Cu-Zn, Ni-Al, Ni-Co, Ni-Cr, Ni-Fe, Ni-Mg, Ni-Mn, Ni-Mo, Ni-Pb, Ni-Se, Ni-V, Ni-Zn, Pb-Al, Pb-Co, Pb-Cr, Pb-Fe, Pb-Mg, Pb-Mn, Pb-Mo, Pb-Se, Pb-V, Pb-Zn, Zn-Al, Zn-Co, Zn-Cr, Zn-Fe, Zn-Mg, Zn-Mn, Zn-Mo, Zn-Se, Zn-V. Synergism and antagonism were several times observed in various combinations of ions. The effect of metal-metal interactions on an accumulation of those metals in the flesh and shells of snails was also observed and measured.

Cyanide ion concentration in the effluent from two gold mines in Zimbabwe and in a stream receiving effluent from one of the goldmines

Abstract Cyanide ion levels were measured in the effluent from two gold mines in Zimbabwe where the gold is extracted by the cyanide process, and at points along a stream receiving effluent from one of the Mines. Cyanide ion levels in the mine effluent were 2.1 x 10‐1g/L and 2.6 g/l at the two Mines. The levels in the stream were much lower at 2.6 x 10‐6g/L and <2.6 x 10‐7g/L about 500 meters and 1 km below the point were effluent enters the stream. The plot of log [CN‐] vs sampling point shows a rapid drop in cyanide concentration along the stream. Possible processes leading to the drop in levels of CN in the stream are discussed.

Organochlorine pesticide residues in the sediments of selected river bays in Lake Kariba, Zimbabwe

Abstract Sediment samples from seven of the major river bays on the Zimbabwe side of Lake Kariba were analysed for organochlorine pesticide residues by capillary gas chromatography and electron capture detection. The results obtained confirm contamination of most of the bays by DDT and its metabolites, endosulphan, aldrin, dieldrin, endrin and heptachlor.

Degradation of oxytetracycline in the aquatic environment: a proposed steady state kinetic model that takes into account hydrolysis, photolysis, microbial degradation and adsorption by colloidal and sediment particles

Environmental context Pollution of the aquatic environment by oxytetracycline can lead to microbial resistance thereby compromising the efficacy of current medication regimes. Adsorption by colloidal and sediment particles reduces the rate at which oxytetracycline degrades, whereas the longer the antimicrobial remains in the aquatic environment, the greater the danger of microbial resistance. There is need therefore for a fuller understanding of the kinetics of degradation of oxytetracycline in aquatic ecosystems before measures for mitigating pollution by the antimicrobial can be designed. Abstract The persistence of oxytetracycline in an aquatic microcosm and distilled water control experiments, was studied over a period of 90 days. An immediate 35% loss as a result of adsorption by the sediment was observed in the microcosm experiment soon after charging. Subsequently triphasic linear rates of oxytetracycline degradation were observed for both the water phase (3.1×10–2, 5.8×10–3 and 1×10–3µgg–1day–1) and sediment phase (4.8×10–2, 6.5×10–3 and 2×10–4µgg–1day–1). Degradation is attributed to photolysis and microbial degradation of the free oxytetracycline in solution, and microbial degradation of the colloidal and sediment particle adsorbed speciation forms. The distilled water control exhibited biphasic zero order kinetics attributed to hydrolysis (2×10–6µgg–1day–1) and microbial degradation (2.7×10–3µgg–1day–1) under dark conditions, and monophasic zero order kinetics attributed to photolysis (6.9×10–3µgg–1day–1) under sunlight exposure. A kinetic model that takes into account hydrolysis, photolysis, microbial degradation and adsorption of the antibiotic by colloidal and sediment particles, is presented to account for the monophasic, biphasic and triphasic zero order kinetics observed in the control and microcosm experiments. Possible remediation strategies for mitigating aquatic environments polluted by the antimicrobial are discussed.

Interference Effects from Easily Ionizable Elements in Flame AES and ICP‐OES: A Proposed Simplified Rate Model Based on Collisional Charge Transfer Between Analyte and Interferent Species

Abstract The effects of excess Na and K on K and Mg atom line emission in the air‐acetylene flame and of excess Li and K on Ca, Mg, and Sr atom and ion lines in inductively coupled plasma spectroscopy were studied using emission signal ratios, I′/I as probes, where I′ and I are the emission readings in the presence and absence of the interferent respectively. The I′/I plots as a function of analyte concentration in the test solution for the ICP experiments were similar to those obtained for the flame experiments in the analytical range 0–10 mg/L. A simplified rate model based on analyte excitation via charge transfer between analyte ions and activated interferent atoms is proposed to account for the emission signal enhancement observed at low analyte concentrations (<1 mg/L) for both ICP‐AES and flame atomic emission spectroscopy (AES). Data are presented showing good agreement between experimental E′ calibration curves and theoretical E′ calibration curves computed using the simplified rate model.

Effect of excess sodium on the excitation of potassium in an air-acetylene flame: a steady state kinetic model which takes into account collisional excitation

SummaryThe effects of excess Na on the ionization and excitation of K in an air-acetylene flame were studied using absorbance signal and emission signal ratios, A′/A and E′/E respectively, as probes, where A′ and E′ are the line absorbance and line emission readings in the presence of excess Na interferent, and unprimed quantities represent readings in the absence of the interferent. An emission signal enhancement which increases exponentially as the ratio of interferent to analyte increases (up to about 2000), was observed irrespective of whether measurements were made from the primary or secondary reaction zones of the flame, while a similar line absorbance signal enhancement was observed only when measurements were made from the primary reaction zone. For both line emission and line absorbance, the maximum enhancements observed are in excess of those predicted on the basis of complete suppression of ionization of analyte atoms as a result of the increased partial pressure of electrons. A steady state kinetic model is presented, which takes into account radiative recombination collisional excitation of K+ ions and collisional charge transfer between the heavy particles, and whose predictions are consistent with the observed interference effects.

Degradation of Fenamiphos, Chlorpyrifos and Pirimiphos-Methyl in the Aquatic Environment: A Proposed Enzymatic Kinetic Model That Takes Into Account Adsorption/Desorption of the Pesticide by Colloidal and Sediment Particles

© 2012 Zaranyika and Mlilo, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Degradation of Fenamiphos, Chlorpyrifos and Pirimiphos-Methyl in the Aquatic Environment: A Proposed Enzymatic Kinetic Model That Takes Into Account Adsorption/Desorption of the Pesticide by Colloidal and Sediment Particles