Analysis of Nitrate Levels in the South East Coastal Areas of Lake Tana using UV-Visible Spectrophotometer

Abstract

Nitrogen compounds added to the terrestrial environment from agricultural sources impact fresh water ecosystems. Nitrate contamination resulting from deposition of nitrates onto soils and plants, with subsequent leaching out of the water shade may enhance the harmful processes of eutrophication in Lake Tana. The aim of this research is to analyze the level of nitrates in Lake Tana. The level of nitrate (NO₃^-) in samples from different sites within the Lake was determined in dry season with standard method using Uv-Visible spectrophotometer during March/April. Nitrate (NO₃^-) values for water samples in Lake Tana ranged from 0.24- 2.21 mg/L NO₃^-. The average nitrate concentrations of the different sites in mg/L Nitrate are as follows; Rib =2.21 ± 0.21, Gumara = 2.09 ± 0.26, Gelda = 2.12 ± 0.20, Mehal Zegie = 0.24 ± 0.12, and Enfraz =1.32 ± 0.17. The value of nitrate (NO₃^-) was higher in the sites of east coastal river mouths of Lake Tana (Gumara, Gelda, and Rib).The southern part of the Lake has lower concentration of nitrates than those on the east coast.  Agricultural practice in the east and urbanization in the south of the lake must have contributed for higher nitrate levels in these areas.Appropriate pollution control measures should be taken in our agricultural practices and urban waste disposal systems in the lake catchments though the levels encountered in this work for now are within the regulatory threshold set by EPA (45 mg/L NO₃^-).

Key words: Nitrate, Euthrophication, Met hemoglobin, Phenol disulphonopic acid.