Tea production in the Kenyan Ri Valley uses high rates of nitrogenous fertilizer. Nitrates can be discharged to water bodies through leaching and surface run-off. Nitrate levels above 10 mg/L NO3 − -N cause methemoglobinemia which is fatal. A study to monitor changes in surface water nitrate levels was carried out in ten rivers within a Kenyan tea plantation for three years. Water samples were obtained before and aer fertilizer application in 2004, 2005, and 2006. Nitrate-nitrogen (NO3 − -N) was determined colorimetrically by the cadmium reduction method using HACH-DR 2400 dataloging spectrophotometer. For the three years, the highest nitrate-nitrogen levels were in river Temochewa in 2005 during the �rst fertilizer applications (4.9 mg/L to 8.2 mg/L). ere was no established trend between surface water nitrate levels and the time of fertilizer applications; however, fertilizer application contributed to an increase in nitrate levels. e initial nitrate-nitrogen levels in most of the rivers were high, indicating that contamination could have been upstream; hence, further research is required to establish this. Nitrogen-nitrogen levels in the three years were below the maximum contaminant level of 10 mg/L NO3 − -N; however, the rivers should be monitored frequently.
Amalgam voltammetry has been used to study heavy metal interaction in model lake water in KNO 3 at 23 o C at concentration levels of genuine lake water. The hanging drop amalgam electrode was prepared in situ before exchanging the medium for the sample solution. Half-wave potentials at two metal ion concentrations were measured, one at the actual concentration in the lake while the other at a much lower one. The experimentally determined shifts in half-wave potentials are used to compute several formation constants. At the natural [CO 3 2-] of 0.5 M in the lake, the main contributor to the speciation of cadmium is [Cd(CO 3 Cl 2)] 2-. At high [Cd 2+ ], the DPASV detects the presence of free Cd 2+ ions, hence, potential polluting effect, while the amalgam reports [Cd(CO 3) 2 Cl)] 3to be dominant above [CO 3 2-] = 0.8 M. There is a variation in the number of complexes detected, their stabilities and percentage distribution in the two methods. Cd 2+ ion concentration also affects the number of complexes formed and their stabilities.
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