Environmental impact assesment on the use of copper based fungicides in coffee farms along Kamiti river
Mwangi, Isaac Waweru
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Copper-based fungicides are extensively used in the control of coffee pests and diseases because they are relatively cheap and effective. This practice has serious environmental implications owing to the toxic nature of copper. An assessment of the effects of the use of copper-based fungicides is carried out on River Kamiti, which flows along coffee growing areas of Kiambu District, Kenya. Water samples were collected at various points along the river from Thika Road Bridge (TRB) to Kamiti Road Bridge (KRB). The levels of copper in the river were determined with total copper being obtained using flame atomic absorption spectrophometry (FAAS) and the labile fraction by differential pulse anodic stripping voltammetry (DPASV) at a glassy carbon electrode. Also Dissolved Organic Carbon (DOC), Fluoride (F), Chloride (CI-), and pH were determined using the standard analytical methods. Total copper was found to range from 0.3 to 2.20 x 10-2 pg/ml with the labile fraction being 49%. The concentration of copper was found to depend on the rainfall, which carried copper to the river from the fields and coffee-harvesting season thus amount of factory discharge. The levels of DOC were found to range between 5.26 - 9.7 x 10 x 10-2 mg/ml, F- 0.4-2.2 x 10-2 mg/ml and Cl- 8.5-17.4 x 10-2 jug/ml therefore can be said to be generally low. Taking glycine, catechol and proline as typical ligands in a water system, speciation modeling showed that at pH<6.5, the fraction of "free" and labile copper species, were observed to increase with decrease in pH. The pH of this water system was found be between 7.4 and 8.14. This implies that copper in the river will be complexed by the host of ligands contributed by the DOC but there will be toxic traces contributed by simple complexes that could easily dissociate. Based on the results obtained in this work, it is concluded that the use of copper compounds in the coffee industry is of environmental concern.