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A study was conducted to investigate the sediment health and water quality of the River Sagana, Kenya, as impacted by the local tanning industry. Chemical analysis identified the main chemical pollutants (pentachlorophenols and chromium) while a bioassay addressed pollutant bioavailability. The bioassay, exploiting the luminescence response of a lux marked bacterial biosensor, was coupled to a dehydrogenase and Dapnia magna test to determine toxicity effects on sediments. Results highlighted the toxicity of the tannery effluent to the sediments at the point of discharge (64% of control bioluminescence) with gradual improvement downstream. There was a significant increase in dehydrogenase downstream, with the enzyme activity attaining a peak at 600 m, also indicating a gradual reduction of toxicity. Biological oxygen demand (19.56 mg L(-1)) dissolved oxygen (3.97 mg L(-1)) and high lethal dose value (85%) of D. magna also confirmed an initial stress at the point of discharge and recovery downstream. Optical density of surface water demonstrated an increase in suspended particulates and colour after the discharge point, eventually decreasing beyond 400 m. In conclusion, the study highlighted the importance of understanding the biogeochemistry of river systems impacted by industries discharging effluent into them and the invaluable role of a biosensor-based ecotoxicological approach to address effluent hazards, particularly in relation to river sediments.

Arsenic (As)-contaminated irrigation water is responsible for high As levels in soils and crops in many parts of the world, particularly in the Bengal Delta, Bangladesh and West Bengal, India. While arbuscular mycorrhizal (AM) fungi markedly improve phosphorus (P) uptake, they can also alleviate metal toxicity. In this study, the effects of superphosphate and inoculation with the AM fungus Glomus mosseae on P and As uptake of lentil were investigated. Plant height, shoot dry weight, shoot/root P concentration, and shoot P content increased due to mycorrhizal inoculation. However, As concentration in roots/ shoots and root As content were reduced, plant height, shoot dry weight, shoot/root P concentration/ content, and root As concentration and content increased due to superphosphate application. Root P concentration decreased with increasing As concentration. It was apparent that As concentration and content in shoots/roots increased with increasing As concentration in irrigation water. Superphosphate interaction with G. mosseae reduced the role of mycorrhizal infection in terms of enhancing P nutrition and reducing uptake of potentially toxic As into plant parts. The role and relationship of mycorrhizal in respect of P nutrition and As remediation efficiency in plant parts was established. In conclusion, it was worth alluding to that lentil with AM fungal inoculation can reduce As uptake and improve P nutrition. However, in retrospect superphosphate increased P and As uptake and decreased the role of the mycorrhizal association. This resulted in stimulating increased P uptake while decreasing As uptake in lentil.

Fly Ash (FA) is obtained by electrostatic or mechanical precipitation of dust-like particles from the flue gases of furnace fired with coal or lignite at 1100 to 1400°C. About 95-99% of Fly Ash consists of oxides of Si, Al, Fe and Ca, about 0.5 to 3.5% consists of Na, P, K and S and the remainder is composed of trace elements. PFA has also been used as an adsorbing material when applied in treatment effluents. The use of Fly Ash as a chemical conditioner has previously been investigated with results indicating that Fly Ash does facilitate the filtering process since it decreases both specific resistance and capillary suction time. Therefore, the aim of this paper was to assess the potential of PFA as an ameliorant for soil artificially spiked with various Lead compounds (PbSO₄, PbCO₃, PbNO₃ and PbS). Additions of quicklime and Fly Ash to the contaminated soils effectively reduced heavy metal leachability well below the regulatory limits for hazardous wastes. The results showed the effect of PFA on leaching of lead was significant for all the samples. A high interaction value depicting sampling effect over the use of the PFA as an ameliorant was observed. The order of the difference between samples treated with PFA and without PFA was PbNO₃ > PbSO₄ > PbCO₃ > PbS (17 mg L^-1) when compared to that of the control. The results also demonstrated that, effect of filtration and PFA as an ameliorant had a significant effect in reducing toxicity. However, it is important to consider the source of PFA, as certain sources could in essence impart certain toxic elements, defeating the primary purpose of amelioration

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