Browsing by Author "Senkondo, Yasin H."

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Copper bioavailability to beans (phaseolus vulgaris) in long-term cu-contaminated soils, uncontaminated soils, and recently cu-spiked soils
(Taylor & Francis, 2015-01-13) Senkondo, Yasin H.; Semu, Ernest; Tack, Filipi M. G.
Copper solubility and its bioavailability to Phaseolus vulgaris in long-term coppercontaminated soils, uncontaminated soils, and copper-spiked soils were studied. The role of plant factors, total copper load in soils, and/or the aging effect on the uptake of copper was explored so as to assess health risks through contamination of the food chain associated with growing the crop on such soils. Contaminated soils and clean soils were collected from coffee-growing fields in Kilimanjaro and Arusha, Tanzania. Two bean seeds were sown per pot, replicated three times, and arranged in a randomized design in a glass house. Copper spiking significantly increased extractable copper, as expected. For all of the treatments except for the Mwanga and Arumeru control soils, the addition of CuSO4 did not significantly increase the humic-acid-bound copper, but it significantly increased the fulvic-acid-bound copper (p = 0.05). Moshi soils had significantly higher concentrations of copper in the bean shoots than was the case with other treatments (p = 0.05). For the respective soil types, there was no significant difference in the concentrations of copper in bean leaves between spiked and unspiked treatments (p =0.05). Bean shoots did not accumulate copper beyond the normal concentrations.
Vertical distribution of copper in copper-contaminated coffee fields in Kilimanjaro, Tanzania
(Taylor & Francis, 2015) Senkondo, Yasin H.; Semu, Ernest; Tack, Filipi M. G.
Soils in coffee farms may be contaminated with copper (Cu) due to intensive and long-term use of Cu-based fungicides. This legacy of Cu contamination may pose risks for contaminating lower soil layers and underground water, or contamination of food crops cultivated on these soils. High concentrations of Cu, strongly exceeding international standard levels, were found within the top 30 cm of affected soils. There was only a limited mobility of Cu below 30 cm layers, suggesting a low risk of contaminating lower soil layers. The Cu mobility in fallow soils was more limited than in tilled soils. There was a positive correlation between silt content and the concentrations of Cu. Potentially mobile Cu fractions, which decreased with soil depth, were greater in contaminated soils than in uncontaminated soils and were greater in top layers than in lower layers, implicating greater Cu availability and consequently higher toxicity risks.