Characterization of Major Ion Chemistry and Hydro-Geochemical Processes in Mt. Elgon Trans-Boundary Aquifer and Their Impacts on Public Health

There is a gradual paradox shift from the utilization of surface water to groundwater in both urban and rural Kenya. This is because surface water is both diminishing in quantity due to climate variability and deteriorating in quality due to high levels of anthropogenic contamination. In the quest to attain the Sustainable Development Goal number 6 that aim at ensuring access to safe water by all by 2030, the Government of Kenya is encouraging the development of groundwater resources whose potential is enormous though it has not been quantified. The Inter-governmental Authority on Development (IGAD) supported this research on the shared Mt. Elgon trans-boundary aquifer between Kenya and Uganda aimed at understanding its dynamics. Mt. Elgon is a Tertiary age mountain that straddles the Kenya-Uganda border and has a trans-boundary aquifer. This study investigated the groundwater chemistry and its implication on water management and human health. Physico-chemical parameters of water that included electrical conductivity, pH, and temperature were measured in the field and the major cations and anions were measured at the Central Laboratories of the State Department for Water. Geological mapping and identification of sanitary risks were undertaken during the field work. The study revealed that the concentration of cations and anions in the groundwater varied spatially and temporally.  Abundance of these ions were in the order Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ for most samples and HCO₃⁻ > Cl⁻ > SO₄²⁻ >NO₃⁻. Interpretation of hydro-chemical data suggests that calcium carbonate dissolution, halite dissolution, Ca/Na ion exchange and Mg/Na ion exchange are the major processes that control the ground-water chemistry. Chemical results indicate further that the groundwater is suitable for domestic use but is threatened by both anthropogenic and geological factors. Extensive use of fertilizer and the destruction of the catchment area coupled with low permeability and rock-water interactions in the metamorphic rock terrains are the main threats to groundwater quality in the region. A few water points had water with some ionic composition exceeding WHO and the local KEBS maximum limits for drinking water. Such water pose a risk to human health. Keywords: Transboundary aquifer, groundwater chemistry, Human health, Carbonate dissolution, Mt. Elgo, Kenya DOI: 10.7176/JEES/9-4-06 Publication date: April 30th 201

Tryptophan-like and humic-like fluorophores are extracellular in groundwater: implications as real-time faecal indicators

Fluorescent natural organic matter at tryptophan-like (TLF) and humic-like fluorescence (HLF) peaks is associated with the presence and enumeration of faecal indicator bacteria in groundwater. We hypothesise, however, that it is predominantly extracellular material that fluoresces at these wavelengths, not bacterial cells. We quantified total (unfiltered) and extracellular (filtered at < 0.22 µm) TLF and HLF in 140 groundwater sources across a range of urban population densities in Kenya, Malawi, Senegal, and Uganda. Where changes in fluorescence occurred following filtration they were correlated with potential controlling variables. A significant reduction in TLF following filtration (ΔTLF) was observed across the entire dataset, although the majority of the signal remained and thus considered extracellular (median 96.9%). ΔTLF was only significant in more urbanised study areas where TLF was greatest. Beneath Dakar, Senegal, ΔTLF was significantly correlated to total bacterial cells (ρs 0.51). No significant change in HLF following filtration across all data indicates these fluorophores are extracellular. Our results suggest that TLF and HLF are more mobile than faecal indicator bacteria and larger pathogens in groundwater, as the predominantly extracellular fluorophores are less prone to straining. Consequently, TLF/HLF are more precautionary indicators of microbial risks than faecal indicator bacteria in groundwater-derived drinking water

Real-time indication of faecally contaminated drinking water with fluorescence spectroscopy: towards understanding the causation

Two billion people still consume drinking water contaminated with faeces. To improve this situation, it has been recognised by UNICEF and the WHO that a more rapid approach to detecting faecally contaminated drinking water is necessary. We have previously demonstrated that fluorescence spectroscopy is a significant real-time indicator of the presence/absence and number of faecal indicator bacteria in drinking waters in low-income countries of the tropics. We have also established its potential as an online indicator of faecal contamination of public water supplies in the UK. Outstanding questions remain, however, over the source of the fluorescence and its uniqueness to faecal-indicator bacteria. To address these, we sampled potable groundwater supplies in Kenya, Malawi, Senegal and Uganda across an urbanisation transect from rural Malawi through to the city of Dakar (Senegal) where pollution sources and pressures vary considerably. We report on whether the fluorescence signal in these sources is intracellular or extracellular and, in Senegal and Uganda, the ability of fluorescence spectroscopy to predict total bacteria cells and faecal-indicator bacteria