Publication Date:
2021-05-19
Description:
Concern has been raised about the contribution of atmospheric deposition to the nutrient flux of Lake Victoria. A few studies on the atmospheric deposition over the African Great Lakes have shown that the atmospheric deposition is a significant source of Total Nitrogen (TN) and Total Phosphorus (TP) to lakes and in fact by far the highest contributor of N and P on the lake surface. This has been attributed to the large scale destruction of soil cover as a result of changes in the land use system, improper agricultural practices and transport from other regions through regional and global air circulation. The objective of this study was to estimate the amount of TP and TN coming from the atmosphere and to compliment measurement from the catchment in order to estimate a nutrient mass balance for Winam Gulf. Two stations were selected for this study, Kadenge and Kisumu. Both wet and dry atmospheric samples were collected in an acid rinsed bucket mounted on a metal structure 1.5m from the ground and analysed for TP and TN using standard methods. It was observed that the annual dry deposition rates for both TP and TN were higher than the wet ones. Dry TP. 575.2 tonnes/year, wet TP. 472.8 tonnes/year giving a total of 1048 tonnes/year with dry P accounting for 55% and wet P 45%. Dry TN. 10289.98 tonnes/year, wet TN. 12133.6 tonnes/year and a total of 22423.6 tonnes/year and dry N accounting for 46% and wet N 54 %. Compared with estimates of TP and TN from the catchment studies these represent about 38% TP and about 70% TN to the Winam Gulf (Kenyan side of L.Victoria) If these rates are applied to the whole lake surface assuming that there is no major difference in deposition rates across the lake, it was estimated that 17515.5 tonnes of TP and 373727.2 tonnes of TN was deposited per year with dry P accounting for more than 50% of TP and dry N accounts for more than 50% of TN. These estimates have been made from two land-based stations and therefore there is need for the inshore stations to be established. It is therefore necessary as a management strategy to eutrophication in Lake Victoria, to address the atmospheric deposition alongside other sources of nutrients to the lake.
Description:
Published
Keywords:
Phosphorus
;
Nitrogen
;
Water quality
;
Eutrophication
Repository Name:
AquaDocs
Type:
Book Section
,
Not Known
Format:
pp.80-101 [Chapter 4]
Permalink
