ASSESSING HEAVY METAL POLLUTION OF GROUNDWATER USING ROOT GROWTH KINETICS OF ALLIUM CEPA AS A BIO-INDICATOR

Abstract

Groundwater, one of the major sources of potable water in rural areas may contain heavy metals with potential cytotoxic and genotoxic effects. These rural areas are often characterized by the unavailability of advanced testing methods. This study investigates the use of Allium cepa as an economical short-term alternative in bioassay for the assessment of heavy metals in rural groundwater. Two species of onions; Allium cepa L. and Allium cepa b. were first sprouted for 24 hrs in a control groundwater sample and then subjected to different concentrations of heavy metals (cadmium, iron, chromium and lead) induced in the groundwater sample. Consequently, the mean daily root growths were measured after 24 hrs, 48 hrs, 72 hrs and 96 hrs while the percentage root growth inhibition was calculated with respect to the control. Other physical changes to the roots of both Allium cepa species were noted and recorded. Results obtained indicate that increase in concentration of the heavy metals in the groundwater sample and duration of exposure led to increase in growth inhibition of Allium cepa L roots. The Allium cepa b. specie did not give a similar response; although there was a general root growth inhibition, but no trend was observed in Allium cepa. b. However, the roots of the Allium cepa b. species subjected to different metal concentrations exhibited physical changes that were peculiar to the different metals. Thus, this study recommends the use of both species to assess the presence, and determine the extent of contamination by heavy metals in rural groundwater as a short-term alternative in rural areas where advanced testing techniques are not available or not within reach area.

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KEYWORDS:  Alluim cepa, Bioassay, Potable water, Pollutants, Water treatment