Abstract
The levels, speciation of elements, and toxicity of selected trace metals as well as other parameters in selected surface water, shallow groundwater sources, landfill leachate, and associated surface runoff in the Lake Victoria basin, Uganda, were studied. The WHO guidelines, Ugandan standards, Canadian guidelines and Swedish EPA were used for assessment. The shallow groundwater was acidic with pH values below 6.5. The pH, dissolved organic carbon, flouride, and sulphate levels for all springs were below the guideline values although 52.8% was contaminated with nitrates while 39% was contaminated with chloride ions. Some surface water samples had levels of major elements, such as iron, chromium, aluminium, and manganese, above the guideline values. Speciation studies showed that 74% of the metal ions was bound to dissolved organic matter in surface water, whereas in landfill leachates, the dominant ionic species was metal hydroxides or fulvic acid bound. Risk analysis based on the Swedish EPA showed varied risks of negative effects in 30%–76% of the sample sites ranging from high to increased risk in surface water, whereas the results from modelling sorption data using the Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+, and Pb2+ in 15.3%–30.8% surface water samples and 8.3%–62.5% groundwater samples.
Highlights
The presence of heavy metals and other pollutants in the aquatic systems has become a serious problem for environmental scientists in many developing countries and for agencies engaged in environmental production [1].Freshwater resources constitute only about 2.5% of the total volume of water on Earth (∼1.4 million·km3), and only about 0.01% (200,000 km3) of all the water on Earth is usable freshwater for ecosystems and humans [2]
Otherwise continued discharge of untreated surface runoff, wastewater, and leachate will negatively impact the shallow groundwater when the soil water is laden during the rainy season; the surface water interacts with the groundwater in shallow aquifers without reacting with the soil chemicals and thence groundwater contamination
Of the metal ions in the landfill leachates and 25% of the metal ions in urban streams are bound to dissolved organic matter (DOM) and were not available as free metal ions
Summary
Freshwater resources constitute only about 2.5% of the total volume of water on Earth (∼1.4 million·km3), and only about 0.01% (200,000 km3) of all the water on Earth is usable freshwater for ecosystems and humans [2]. Uganda is a developing country that is home to the source of the River Nile which is the longest river in the world that moves 6,850 km to the Mediterranean Sea from. Lake Victoria is the second largest freshwater lake in the world with a surface area of 68,800 km and a volume of 2,760 km3 [5]. The Nile river basin covers almost 10% of the total area of the African continent with an area of 3,100 km2 [6]. There are eleven countries that make up the Nile River drainage basin, namely, Rwanda, Burundi, Democratic Republic of Congo, Uganda, South
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
