School of Pure and Applied Sciences

Permanent URI for this collectionhttps://koha2.tukenya.ac.ke/handle/123456789/862

Browse

Recent Submissions

Now showing 1 - 20 of 52
  • Thumbnail Image
    Item
    SIMULATED MODELING: CONTRASTING Ca/Mg AND Mn+-NATURAL ORGANIC MATTER COMPETITIVE COMPLEXATION IN WATER
    (2015-07-20) Mbugua, John
    Complexing capacities of calcium and magnesium with natural organic matter (NOM)/selected organic chelating agents, in the presence and absence of other major and trace cations in water,were studied by anodic and cathodic square wave stripping voltammetry techniques (ASWSV and CSWSV). Under predetermined and optimized physico-chemical parameters (pH, temperature and ionic strength), calcium-NOM complexation and competitive complexation by other elements of known concentration (Pb, Zn, and Cu) were determined. Voltammetric measurements showed competition between calcium and the other cations for the binding sites of humic substances at depositing, measuring and equilibrating potential of -2V and +1V and scan time of 150 seconds.Two systems were complexed by known concentrations of NOM fractions (Humic acid (HA), 1, 2-dihydroxybenzene (CAT/catechol) and tannic acid (TA)): Mn+-NOM; Mn+Calcium-NOM complexes at different pH conditions. Results show significant differences in peak currents in the order Mn+> Ca/Mn+-TA/HA/CAT > Mn2+-TA/HA/CAT but differed depending on the metal species, type of humic chelant and pH. Visual Minteq and PHREEQC simulations show differences in distribution of scale causing species such as Ca2+, CaOH+, Mg2+ and MgOH+ that are highly dependent on the pH and concentration. This paper presents results of partof the work aimed at providing simulated modeling alternatives in combating scaling as a consequence of cooling water used in industry. It equally provides an assurance on the re-use of the scarce water resources by simulated water experiments and models
  • Thumbnail Image
    Item
    Reactive-transport modeling of fly ash–water–brines interactions from laboratory-scale column studies
    (2015-07-20) Mbugua, John
    Dynamic leaching tests are important studies that provide more insights into time-dependent leaching mechanisms of any given solid waste. Hydrogeochemical modeling using PHREEQC was applied for column modeling of two ash recipes and brines generated from South African coal utility plants, Sasol and Eskom. The modeling results were part of a larger ash–brine study aimed at acquiring knowledge on (i) quantification and characterization of the products formed when ash is in contact with water–brines in different scenarios, (ii) the mineralogical changes associated with water–brine–ash interactions over time, (iii) species concentration, and (iv) leaching and transport controlling factors. The column modeling was successfully identified and quantified as important reactive mineralogical phases controlling major, minor and trace elements’ release. The pH of the solution was found to be a very important controlling factor in leaching chemistry. The highest mineralogical transformation took place in the first 10 days of ash contact with either water or brines, and within 0.1 m from the column inflow. Many of the major and trace elements Ca, Mg, Na, K, Sr, S(VI), Fe, are leached easily into water systems and their concentration fronts were high at the beginning (within 0.1 m from the column inflow and within the first 10 days) upon contact with the liquid phase. However, their concentration decreased with time until a steady state was reached. Modeling results also revealed that geochemical reactions taking place during ash–water–brine interactions does affect the porosity of the ash, whereas the leaching processes lead to increased porosity. Besides supporting experimental data, modeling results gave predictive insights on leaching of elements which may directly impact on the environment, particularly ground water. These predictions will help develop scenarios and offer potential guide for future sustainable waste management practices as a way of addressing the co-disposal of brines within inland ash dams and heaps.
  • Thumbnail Image
    Item
    Application of hydrogeochemical modelling in simulating the transportation of elements in fly ash heap under different disposal systems in South Africa
    (2015-07-20) Mbugua, John
    Ash heap modelling of South African fly ash from Tutuka was carried out and the duration of transportation projected for 20 years based on two disposal scenarios, namely; irrigation of ash with rainwater, and irrigation with brines. The hydrogeochemical modeling code, PHREEQC, was applied in the study which gave insights into the speciation, release and transport of elements from the water and brines–fly ash long term interactions. Tutuka ash–water heap model showed a general sharp decrease of total elemental concentrations released during the first 2.5 years simulation as the pH value dropped from 12.6 to 8.7, after which it remained constant and their concentration remained constant up to 20 years. The elements showing this trend included Ca, Mg, Al, Fe, Sr, Zn, Na, K, Li and C(4). Generally, brines caused sharp increase in released concentration of the elements Ca, Mg, S(6) and C(4) for the first 3 years of heap irrigation whereas with water irrigation an opposite trend was observed in which the elemental concentrations decreased. Much of the release chemistry of the elements was closely related to the phase dissolution/precipitation and formation as the major controlling factors. Generally therefore, the modelled leachate quality results revealed that many elements are mobile and move through the ash heap in a progressive leaching pathway. The model could therefore be used to provide reasonable leachate quality from the modelled Tutuka ash heap which may be reaching the ground water. Overall, the ash heap modelling enhanced the understanding of the environmental impacts of ash–water–brines interactions and demonstrated that leachate composition is determined by the following factors; (i) the mass flows from the pores of fly ash, (ii) the surface dissolution of the mineral phases, (iii) the various chemical reactions involved during the ash–brine and ash–water interactions, (iv) the interactions with a gas phase (atmospheric CO2), (v) the composition of the initial fly ash, and (vi) the leachate flow and hydrodynamics as captured in the conceptual model. Further model validation is recommended with lysimeters to quantatively compare the simulated results against the experimental data and improve on the model.
  • No Thumbnail Available
    Item
  • No Thumbnail Available
    Item
    Declining commercial fish catches in Lake Victoria's Winam Gulf: The importance of restructuring Kenya's aquaculture programme
    (2014) Omwoma, Solomon; Owuor, Philip O; Ongeri, David MK; Umani, Moses; Lalah, Joseph O; Schramm, Karl-Werner
    The total weight of commercial fish (metric tons) caught in the Winam Gulf area of Lake Victoria in Kenya declined from 3300 mt to 760 mt between 1995 and 2009. Associated with this decline, and ranked in descending order, the species richness of the commercial fish catch was limited to seven major groups (Rastrineobola argentea; Lates niloticus; Protopterus aethiopicus; Labeo victorianus; Haplochromis species; Clarias gariaepinus; Bagrus domac). Numerous hypotheses ranging from eutrophication, inadequate control of the exotic water hyacinth and overfishing were advanced to explain this decline. The Kenyan government, working in partnership with international organizations, implemented multiple restoration and management programmes in response, including aquaculture. Unfortunately, success for this implemented programme has been very limited because important socio-economic driving factors were overlooked. To provide a better understanding of the issues, 150 members of the Winam Gulf fishing community, ranging in age from 20 to 40 years, were surveyed. The results of this survey identified poverty and inadequate education as two major issues requiring substantial attention. The survey also suggested that if societal changes are to occur, it will rest upon changing the beliefs of the youth in the Winam Gulf area. Restructuring Kenya's aquaculture programme, with a focus on the youth, provides a pathway for increasing the literacy level of the community, as well as for reducing poverty.
  • No Thumbnail Available
    Item
    Impact of Agronomic Inputs in Sugarcane Farming on Total Heavy Metal Levels in Aquatic Ecosystems and Soils within Lake Victoria Basin, Kenya.
    (Springer, 2014) Omwoma, S; Lalah, JO; Ongeri, DMK; Schramm, Karl-Werner
    Sugarcane farming is the most important cash crop cultivation activity in the Lake Victoria basin of Kenya practised in an area covering approximately 114,000 Ha in total. For better yields, various agronomic inputs including fertilizers and herbicides have been used intensively in the farms, causing serious concerns about their potential impacts on the aquatic ecosystems within the lake basin. In this study, the physicochemical features of surface sediment and water including pH, total organic carbon contents and heavy metal (Cd, Cu, Zn, Pb and Cr) loads in River Kuywa and in runoff canals in sugarcane farms in Nzoia nucleus estate within the lake basin were determined to assess the effects of agronomic activities including agronomic inputs in the form of nitrogenous fertilizers [urea and diammonium phosphate (DAP)], herbicides and sewage sludge used in farming on their levels. The results indicated significant differences (p ≤ 0.05) in the heavy metal levels in sediment and water samples taken before and after the farms, respectively, indicating a positive impact on the concentration levels. The canal water and sediment samples’ heavy metal levels were also significantly higher than those of the river samples showing that the influent sugarcane farm canal waters transfer these contaminants into River Kuywa. Although the levels of these parameters were significantly higher in the canals than in the controls obtained from outside the sugarcane farms, the heavy metal levels in soil samples from within the farms with similar agronomic activities did not differ significantly among the various plots. The turbidity, electrical conductivity, temperature, water and soil pH and total organic carbon values in samples obtained within the sugarcane farms showed significant seasonal variations and differed significantly from the values in the controls showing a significant negative impact of agronomic inputs on water quality.
  • No Thumbnail Available
    Item
    The impact of nitrogenous and phosphorous nutrients from selected point sources in Kisumu City on River Kisat and Nyalenda Wigwa Stream before their discharge into Winam Gulf, Lake Victoria
    (Springer, 2014) Musungu, Patrick Chamula; Lalah, Joseph O; Jondiko, Isaac O; Ongeri, David MK
    Various industrial facilities including a fish-processing factory, a matchbox factory, a flour mill and a landfill, all in Kisumu City in Kenya, were studied and found to discharge significant amounts of NO2 −–N, NO3 −–N, org N, total N and total P into River Kisat and Winam Gulf of Lake Victoria, with % increases in the mean levels at the outlets of these facilities ranging from 9.6 to 200, 5.9 to 43.5, 9.3 to 96.1, 8.1 to 35.5 and 9.7 to 50.5 %, respectively. The concentrations of NO2 −–N, NO3 −–N, NH3–N, org N and total N attributable to these facilities increased by 1,509, 51.1, 112.6, 97.5 and 90.6 %, respectively, at the point of entry into Rive Kisat. The Nyalenda Wastewater Stabilization Ponds reduced the mean levels of NO2 −–N, NO3 −–N, org N, total N and T-P by 50, 10.4, 16.6, 7.8 and 30.8 %, respectively, indicating low efficacy of their removal and potential impact on water quality in Lake Victoria. The efficacy of the Kisat wastewater treatment plant was also found to be very low with % reductions of the analysed nutrients ranging from 2.82 to 41.30 %.
  • No Thumbnail Available
    Item
    The impact of agronomic inputs on selected physicochemical features and their relationships with heavy metals levels in surface sediment and water in sugarcane farms in Nzoia, Kenya
    (Springer, 2014) Omwoma, Solomon; Lalah, Joseph O; Ongeri, David MK; Schramm, Karl-Werner
    Sugarcane farming is the most important cash crop cultivation activity in the Lake Victoria basin of Kenya practised in an area covering approximately 114,000 Ha in total. For better yields, various agronomic inputs including fertilizers and herbicides have been used intensively in the farms, causing serious concerns about their potential impacts on the aquatic ecosystems within the lake basin. In this study, the physicochemical features of surface sediment and water including pH, total organic carbon contents and heavy metal (Cd, Cu, Zn, Pb and Cr) loads in River Kuywa and in runoff canals in sugarcane farms in Nzoia nucleus estate within the lake basin were determined to assess the effects of agronomic activities including agronomic inputs in the form of nitrogenous fertilizers [urea and diammonium phosphate (DAP)], herbicides and sewage sludge used in farming on their levels. The results indicated significant differences (p ≤ 0.05) in the heavy metal levels in sediment and water samples taken before and after the farms, respectively, indicating a positive impact on the concentration levels. The canal water and sediment samples’ heavy metal levels were also significantly higher than those of the river samples showing that the influent sugarcane farm canal waters transfer these contaminants into River Kuywa. Although the levels of these parameters were significantly higher in the canals than in the controls obtained from outside the sugarcane farms, the heavy metal levels in soil samples from within the farms with similar agronomic activities did not differ significantly among the various plots. The turbidity, electrical conductivity, temperature, water and soil pH and total organic carbon values in samples obtained within the sugarcane farms showed significant seasonal variations and differed significantly from the values in the controls showing a significant negative impact of agronomic inputs on water quality.
  • No Thumbnail Available
    Item
    Dioxin-like PCBs and PCDD/Fs in surface sediments near the shore of Winam Gulf, Lake Victoria
    (Elsevier, 2015) Omwoma, Solomon; Lalah, Joseph O; Virani, Munir; Schramm, Karl-Werner; Henkelmann, Bernhard
    Winam Gulf of Lake Victoria is considered to be contaminated with toxic chemicals emanating from anthropogenic activities, especially near large industrial towns such as Kisumu. This has recently caused concerns about its water quality and impact on aquatic organisms and human beings. This study was justified by the need to generate baseline concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in surface sediment from selected sites in the lake and determine the influence of activities on their concentrations and potential risks to fish-eating birds living near the lake. Surface sediments (<30 cm) from three different fish landing beaches, located 200 m from the shore of Winam Gulf of Lake Victoria near Kisumu city, Homa Bay and Mbita (control) towns, were analysed. The total mean concentrations (in pg g−1 dry wt) were found to range from 17.4–812 (Σdl-PCBs), 36.6–813 (ΣPCDDs) and 1.45–46.4 (ΣPCDFs). The calculated Toxic Equivalents (TEQWHO(2005)) ranged from 0.001–0.43 (Σdl-PCBs) and 0.09–31 (ΣPCDD/Fs). The fish landing beaches at Kisumu city were found to be contaminated with respect to dl-PCBs and dioxins, followed by Homa Bay and Mbita. The relatively high levels of octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) influenced the TEQ and the ΣPCDFs/ΣPCDDs ratios indicated chemical processes as partial sources of the dioxins. The levels of contaminants obtained in this study showed potential exposure to aquatic organisms and fish eating birds through food chain transfer
  • No Thumbnail Available
    Item
    Developing Global Leaders for Research, Regulation, and Stewardship of Crop Protection Chemistry in the 21st Century
    (2015) Unsworth, John B; Corsi, Camilla; Van Emon, Jeanette M; Farenhorst, Annemieke; Hamilton, Denis J; Howard, Cody J; Hunter, Robert; Jenkins, Jeffrey J; Kleter, Gijs A; Kookana, Rai S; Lalah, Joseph O; Leggett, Michael; Miglioranza, Karina S. B; Miyagawa, Hisashi; Peranginangin, Natalia; Rubin, Baruch; Saha, Bipul; Shakil, Najam A
    To provide sufficient food and fiber to the increasing global population, the technologies associated with crop protection are growing ever more sophisticated but, at the same time, societal expectations for the safe use of crop protection chemistry tools are also increasing. The goal of this perspective is to highlight the key issues that face future leaders in crop protection, based on presentations made during a symposium titled “Developing Global Leaders for Research, Regulation and Stewardship of Crop Protection Chemistry in the 21st Century”, held in conjunction with the IUPAC 13th International Congress of Pesticide Chemistry in San Francisco, CA, USA, during August 2014. The presentations highlighted the fact that leaders in crop protection must have a good basic scientific training and understand new and evolving technologies, are aware of the needs of both developed and developing countries, and have good communication skills. Concern is expressed over the apparent lack of resources to meet these needs, and ideas are put forward to remedy these deficiencies
  • Thumbnail Image
    Item
    Effects of Zeolite X on Dissipation of Hexazinone from Agricultural Waste Waters in Western Kenya
    (2013) Agoro, David J; Kowenje, Chrispin O; Lalah, Joseph O; Osewe, Elly T; Ogunah, Joanne A
    Dissipation of hexazinone in Zeolite X treated wastewater followed pseudo first-order kinetics giving a calculated half-life of 41 days compared to a half-life of 144 days in untreated wastewater. The herbicide degraded faster (0.0067 h-1) in treated than in nonzeolite-treated wastewater (0.0027 h-1) forming products A, B, C, D and E within the first 12 h. Zeolite X effectively catalyzed the formation of product A compared to the rest. Calculated rate constants for formation of products A, B, D and E were: 8.33 x 10-4 h-1, 5.65 x 10-4 h-1, 5.52 x 10-4 h-1 and 1.38 x10-3 h-1 respectively in non-zeolite-treated wastewater; and 3.988 x 10-3 h-1, 4.875 x 10-4 h-1, 4.745 x 10-4 h-1 and 2.82 x 10-3 h-1 respectively in zeolite-treated wastewater.
  • Thumbnail Image
    Item
    Effects of faujasite X and Y zeolites on the 1,1,1-trichloro-2,2’ bis(p-chlorophenyl)ethane (DDT) degradation during water purification
    (2013) Kowenje, Chrispin Ounga; Osewe, Elly Tetty; Lalah, Joseph O
    The ability of zeolites to abstract and denature organochloride pesticides finds application in water purification practices. In this study, activated faujasite X and Y zeolites were separately exposed to 1, 2 and 4 ppm concentrations of 1,1,1-trichloro-2,2’ bis(p-chlorophenyl) ethane (dichloro dipheny trichloroethane - DDT) water solutions. For the 1 ppm DDT solutions, the resultant degradation products and residual DDT were minimal with concentrations in zeolite treatments reducing to below detection limit (0.005 ppm) in about 2 hours. In addition, the rate of dissipation was found to somewhat depend on the levels of DDT concentration and the type of zeolite used. The main degradation product in samples exposed to faujasite X was dichloro dipheny dichloroethylene (DDE) whereas in the faujasite Y exposed samples, both the DDE and dichloro diphenyl dichloroethane (DDD) were obtained.
  • No Thumbnail Available
    Item
    METRIBUZIN SORPTION DYNAMICS IN ACID SOILS OF NZOIA SUGARCANE ZONE IN WESTERN KENYA
    (2011) Lagat, Silas C; Lalah, Joseph O; Kowenje, Chrispine O; Getenga, Zachary M; Chepkui, Richard
    The adsorption, desorption and leaching of metribuzin in agricultural soil samples taken from Nzoia sugarcane farming area in Kenya were determined using standard methods. The Freundlich adsorption isotherm constants (Kf and 1/n) were found to be 0.54 µg/g and 0.61 µg mL-1, respectively. 94.9% of the residues were recovered after 6 hours of the desorption test and 93.7% of applied dose was found in the leachate after 9 hours of leaching in a soil column. The adsorption curves indicated L-type of adsorption for 0.1, 1.0 and 2 µg L-1 initial pesticide concentrations and S-type for the 5 ppm initial concentration with peak equilibrium adsorption established after 4 hrs of exposure for the 0.1, 1.0, 2.0 µg L-1, respectively, and after 6 hours for the 5 µg L-1 initial concentration. Although the metabolites were not determined, HPLC analysis showed that degradation was rapid and started to occur after 4 hours of exposure, influencing its adsorption isotherms
  • No Thumbnail Available
    Item
    The metabolism and distribution of [14C‐phenyl]‐ethyl parathion in a tropical soil under field conditions
    (1999) Lalah, Joseph O; Wandiga, Shem O
    The persistence, distribution and metabolism of [l4C‐phenyl]‐ethyl parathion applied to soil columns in an agricultural farm were investigated under tropical field conditions. Volatilization, soil microbial activity, moisture levels and pH were found to influence the persistence, distribution and metabolism of this pesticide in the soil. There was rapid distribution of the pesticide in the soil matrix with time resulting in high levels of bound residues which reduced the overall rate of disappearance of parathion residues from the soil. The soil was slightly acidic but the metabolites, paraoxon, p‐nitrophenol and p‐aminophenol were detected in the soil extracts 7 days after pesticide application. After 72 days, 43.7% of the applied pesticide remained in soil composed of 18.9% extractable and 24.8% bound residues. A mechanism for the metabolism of ethyl parathion in this soil is given.
  • No Thumbnail Available
    Item
    Trace metals in Lates niloticus and Rastrineobola argentea samples for human consumption at Winam Gulf of Lake Victoria
    (2009) Ongeri, DMK; Lalah, JO; Wandiga, SO; Schrammc, K.-W; Michalke, B
    Trace metals were determined in the two most abundant fish species in the Winam Gulf of Lake Victoria (Lates niloticus and Rastrineobola argentea). The results show that the concentratios of the metals have no significant difference (p < 0.05) among the different sampling sites for each species. This situation was attributed to the mobility trends of fish. The abundance trend of the metals in L. niloticus was Fe>Cu>Pb>Cd, while that of Rastrineobola argentea was Zn>Fe>Cu>Pb>Cd. The difference in the trends was attributed to the fact that Rastrineobola argentea is consumed wholly, while the internal organs of L. niloticus are gotten rid of before consumption. This same reason explains why the concentrations of the metals were significantly higher in Rastrineobola argentea compared to those in L. niloticus. Rastrineobola argentea was found to be a major source of trace metals intake by humans.
  • No Thumbnail Available
    Item
    Impacts of climate-induced changes on the distribution of pesticides residues in water and sediment of Lake Naivasha, Kenya
    (2013) Otieno, Peter O; Owuor, P. Okinda; Lalah, Joseph O; Pfister, Gerd; Schramm, Karl-Werner
    This study reports evidence of increased chlorpyrifos contamination in sediment and water in Lake Naivasha following its intensive application in the horticultural farms in the catchment area. Analytical results show that levels of chlorpyrifos residues were influenced by climate-induced rainfall pattern with higher levels reported during period of heavy precipitation with significant decrease during low rainfall. On average, the levels ranged between 14.8 and 32.8 ng g−1 in sediment during rainy season compared to a range of 8.5–16.6 ng g−1 in the dry season. Additionally, the mean concentration of chlorpyrifos in water ranged between 8.61 and 22.4 μg L−1 during rainy season and below detection limit (bdl) −13.6 μg L−1 in dry season as quantified by enzyme-linked immunosorbent assay. Meanwhile, independent t test analysis indicated that there was significant difference in concentration at p ≤ 0.05 between the seasons with respect to sediment and water samples. This demonstrated that climate-induced variations had considerable influence on contamination. While diazinon and carbofuran were equally applied intensively, their levels were below the detection limit in the all the samples analyzed. ELISA results were validated by the capillary-HPLC photodiode-array detector instrument analysis, and statistical comparison showed no significant difference between them. It was evident that chlorpyrifos residues determination in water and sediment by ELISA can be a useful strategy in environmental management and monitoring program, and a complimentary analytical tool to high performance liquid chromatography. Levels of chlorpyrifos detected in sediment and water were found to exceed recommended criteria for protection of aquatic life and preservation of water quality and may be hazardous if not regularly monitored.
  • No Thumbnail Available
    Item
    Soil and water contamination with carbofuran residues in agricultural farmlands in Kenya following the application of the technical formulation Furadan
    (2010) Otieno, Peter O; Lalah, Joseph O; Virani, Munir; Jondiko, Isaac O; Schramm, Karl-Werner
  • No Thumbnail Available
    Item
    Behavior of pesticide residues in agricultural soil and adjacent River Kuywa sediment and water samples from Nzoia sugarcane belt in Kenya
    (Springer, 2012) Muendo, Boniface M; Lalah, Joseph O; Getenga, Zachary M
    An inventory survey conducted to determine pesticide usage in a sub-catchment of the Nzoia sugarcane belt found a variety of pesticides used in the sub-catchment, which are reported in this paper. Analysis of soil samples from seven fallow experimental field plots left uncultivated for various periods from 3 to 96 months after cultivation with pesticide application indicated persistence of high concentrations of pesticide residues in the soil, with estimated soil half-lives (in years) ranging from 0.72 to 57.75 for organochlorines and from 1.13 to 8.25 for herbicides. The mean water concentrations (in μg/L) of the pesticide residues in River Kuywa, which flows through the Nzoia Nucleus Estate sugarcane farms, ranged from 0.12 (lindane) to 1.36 (p,p′-DDT) for organochlorines and from 0.14 (atrazine) to 1.75 (diuron) for herbicides during the heavy rains period in August 2008 while the mean sediment concentrations (in μg/g) ranged from 0.28 (lindane) to 1.87 (endrin) for organochlorines and 0.39 (hexazinone) to 4.61 (alachlor) for herbicides. The mean concentrations of residues in water during the light rain period in December 2008 ranged from 0.17 (p,p′-DDT) to 0.71 (aldrin) for organochlorines and 0.01 (atrazine) to 1.74 (alachlor) for herbicides while the sediment concentrations ranged from 0.38 (p,p′-DDT) to 1.145 (aldrin) for organochlorines and 0.74 (atrazine) to 1.98 (alachlor) for herbicides. Although DDT, aldrin, dieldrin, and endrin were not reported in the survey, their presence in the fallow experimental field plot soils and in River Kuywa water and sediment could indicate previous application, lack of recorded data or illegal usage since 1997 when they were banned. Notably, the concentrations of alachlor, diuron, cypermethrin, and hexazinone in the water column were substantial indicating their extensive usage and residual persistence in the sub-catchment, with subsequent wash-off and leaching into River Kuywa. The concentration levels of some of the individual pesticides exceeded the EU limit requirements for drinking water and indicated potential risk to humans and cattle if the water is used without treatment.
  • No Thumbnail Available
    Item
    Analysis of Moss and Topsoil to Monitor Metal Emissions from a Pulp and Paper Mill in Western Kenya
    (2011) Adoli, Florence K; Lalah, Joseph O; Okoth, Alexander O
    The mean concentrations of Zn, Cu, Cd, Cr and FeinmossesaroundWebuyePanPaperfactorywerefound to be significantly higher than in controls taken from Kakamega, indicating atmospheric contribution from the anthropogenic activities within the factory, shown within a radius of 1 km around the factory. The mean concentrations (lg/g dry weight) in the mosses ranged from 60.9–124.5, 22.6–34.2, 13.3–14.7, 20.1–33.3 and 1,822.4– 2,079.2, respectively. The mean concentrations of Pb in mosses sampled from the eastern and western side of the factory were also significantly higher than in controls. The mean concentrations of Zn, Cu, Cd, Cr, Pb and Fe in topsoil samples ranged from 7 (Pb)–2,310 (Fe) mg/kg dry wt, depending on sample means based on site direction, distance from the factory and season. There was no clear variation in metal concentrations in mosses and topsoils with direction from the factory which was consistent with the observed fluctuations in wind direction which changed from south-west in the mornings to north and south-west in the afternoons during sampling.
  • No Thumbnail Available
    Item
    Nutrient reduction in runoff water from sugarcane farms by sedimentation method
    (2012) Omwoma, Solomon; Omwoyo, W. Nyaigoti; Alwala, Joseck O; Ongeri, David MK; Lagat, C. Sylus; Lalah, Joseph O
    Due to intensive use of agronomic inputs in sugarcane farming, runoff water from these farms is loaded with high concentrations of nutrients. These nutrients find their way into rivers, lakes and sinks, eutrophicating them. Reducing the levels of these nutrients in runoff water from sugarcane farms before it is discharged into sinks will help solve the problems that arise out of eutrophication. This study employed a simple sedimentation method of making depressions in canals draining runoff water from sugarcane farms and emptying them fortnightly during the rainy season and monthly during the dry season. The method was found to significantly (p ≤ 0.05) reduce water conductivity (μS/cm), turbidity (Nephelometric Turbidity Units), total phosphates, nitrate–nitrogen, potassium, calcium, magnesium, iron, copper, sodium and zinc (ppm) in the dry season from 52.89, 148.70,0.87, 3.34, 446.00, 420.00, 205.00, 12,941.00, 261.00, 398.00, and 484.00 in untreated canals to 48.33, 30.22, 0.21, 2.95, 120.00, 154.00, 98.00, 456.00, 181.00, 234.00, and 311.00 in treated canals, respectively. And in the wet season, the parameters were reduced from 261.46, 719.30, 820.00, 25.16, 654.00, 549.00, 493.00, 19,230.00, 763.00, 748.00, and 903.00 to 128.67, 365.70, 3.47, 10.12, 136.00, 187.00, 167.00, 654.00, 207.00, 321.00, and 231.00, respectively. Dissolved oxygen significantly (p ≤ 0.05) increased from 5.11 to 8.14 ppm in the dry season and from 3.82 to 7.92 ppm wet season. Acidity reduced in the wet season from pH 5.02 to 6.20. It is, therefore, recommended that sugarcane farmers adopt this method for sustainability of aquatic systems within these zones.