Impact of fly ash deposition on plants diversity, metal content, and associated risk on grazing ruminants in the vicinity of Morupule power station, Botswana

Abstract

Fly ash (FA) deposition originating from power stations and unprotected dumpsites, have been found to affect plant communities, potentially causing environmental degradation and food chain contamination. An analysis of plant composition, heavy metal concentration in plants and soil within 40 kilometers of the Morupule dumpsite was conducted to evaluate the impact of FA disposal. In addition, risks to the ruminants grazing in this area, were assessed. The windward transect had significantly higher species diversity and richness than the leeward transect, especially in areas closer to the dumpsite. This could be attributed to the inability of some plants to tolerate higher concentrations of toxic metal and alkalinity in areas near the dumpsite. In this study, average concentrations in plants of Cr (546.11 mg kg−1), Mn (905.69 mg kg−1), and Cu (128 mg kg−1) were above toxicity levels of 75-100 mg kg−1 for Cr, 400 mg kg−1 for Mn, and 100 mg kg−1 for Cu. Although the quantities of these metals were above the maximum allowable daily consumption, calculations of the daily plant intake by grazing animals in this area revealed a potential danger of exposure to Cr and Cu. Particularly in areas that were nearest to the FA dumpsite, ruminants grazing on the leeward transect were more exposed to Cu than Cr toxicity. Overall, it was found that FA deposition damaged the plant community and put grazing ruminants at greater danger. However, more investigation is required to pinpoint the precise level of hazardous metals found in the grazing animals in this area.