Hydrology: Current Research

Plant species such as Thlaspi caerulescens Viola calaminaria, Euphorbia prostrata, Arundo donax, Brassica
juncea, Helianthus annuus, Festuca arundinacea, Populus species etc. are long known for their ability to extract
heavy metals from soil and waste water. Various attempts at increasing efficiency of extraction by phytoremediation
include adding micro- organisms, co-cropping various species and using genetically engineered species. So far, the
effect of levels of concentration of heavy metals on extraction efficiency of these plants has not been investigated.
The purpose of this study is to test for the hypothesis that the concentration of heavy metals in soils affects the
efficiency of phytoremediation. Nine samples of Typha latifolia were planted under controlled environment. Plants
were irrigated by wastewater of industrial effluents diluted with different amounts of clean water, while providing
protection from rainwater. The soil in the planters was tested for heavy metals to obtain levels of contamination
already present in the soil and after plants was fully grown, using X-Ray Fluorescence Spectrometry, while the
wastewater used for irrigation was tested using Atomic Absorption Spectrometry. The amount of heavy metals
already present in the soil and that introduced by irrigation was compared to the amount left behind in the soil
after maturity of plants, were compared to test the hypothesis. The results suggested that rate of extraction of
heavy metals using phytoremediation was indeed affected by the level of concentration of heavy metals in the soil
and irrigation water, however, owing to the small number of samples, the relationship between extraction rate and
concentration levels could not be established. The study provides enough evidence to support the stated hypothesis
and opens a new avenue of research to optimize the extraction efficiency of Typha latifolia and other species.

The study was conducted between January and December, 2018. The objective of the study was to assess the current status of physicochemical water quality parameters of Lake Hayq. An integrated water sampling method was used. Water quality parameters such as Dissolved Oxygen, pH, Temperature, conductivity, turbidity and Secchi-disk depth were measured in situ using digital water quality parameters and Secchi disk. Other nutrients, Nitrate, Ammonia, Total Phosphorous, Soluble Reactive Phosphorus, Silicon dioxide, Chlorophyll-a, and total alkalinity were
analyzed in Addis Ababa University Limnological laboratory. Ammonium ion was analyzed in the Addis Ababa University Isotope laboratory. The collected data were analyzed using Two Way ANOVA through the application of SPSS Version 16 Software. In Lake Hayq, the mean physicochemical water quality parameters, temperature (23°C), pH (8.8), Secchi disk depth (3.5m), turbidity (4.5 NTU), total alkalinity (8.8 meqL-1),Total Phosphorous (39 μgL-1), Soluble Reactive Phosphorus (8.3 μgL-1), Nitrate (160.90 μgL-1), Ammonium ion (210 μgL-1), Silicon dioxide (142.3 μgL-1), Chlorophyll-a (4.03 μgL-1), and conductivity (920 μS cm-1) were recorded. Based on Carlson’s index of
trophic state (TSIC), Lake Hayq is mesotrophic (TSIC= 40.03). Lake Hayq has more inorganic nutrient value due to nutrient enrichment through runoff, siltation and point source of pollution from nearby Lodges which will accelerate the eutrophication process in the lake shortly. Therefore, integrated waste management and watershed management should be implemented to minimize the nutrient load and restore Lake Hayq.