Heavy Metals in Blanket Dam and Downstream Weirs, and the Associated Risk to Human Health
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ORIGINAL ARTICLE
Heavy Metals in Blanket Dam and Downstream Weirs, and the Associated Risk to Human Health Qaphelani Ngulube1 · Champaklal T. Parekh1 · Stephen Majoni2 Received: 18 June 2020 / Accepted: 14 October 2020 © The Tunisian Chemical Society and Springer Nature Switzerland AG 2020
Abstract A variety of natural phenomena and anthropogenic activities close to waterways result in heavy metals accumulating in water bodies. It is therefore imperative to determine the levels, and evaluate the health risk indices (HRI), of heavy metals in water bodies that are at risk of heavy metal pollution. In this study, water samples from a dam and three downstream weirs in a town with rampant illegal mining activities were studied. To get a representation of the water accessed by animals and humans, the water samples were collected within half a meter from the edges of the reservoir and dam wall. Levels of heavy metals (Cd, Pb, Fe, Zn, Hg, Au, Cu and Ni) and HRI of Pb, Cd, and Fe were evaluated. Dissolved metal analysis was done by Flame Atomic Absorption Spectrometry (FAAS)—Direct Aspiration Method while mercury was analysed using a mercury analyser. Levels of Cd, Pb, and Fe were above the maximum contaminant level standards for WHO, SAZ and USEPA while levels of Cu, Au, Hg, Ni, and Zn were below. Cd and Pb had high HRI indicating considerable human health risk to the exposed local population. HRI for Fe were within the safe range for human health. Consistently high levels of Cd and Pb and the associated high health risk indices dictates that the water from the water bodies need to be treated before use for domestic purposes. Keywords Water pollution · Metal toxicity · Drinking water · Human risk index
1 Introduction Heavy metals are amongst the most notorious contaminants that can be found in the environment as they are highly toxic even at low concentrations, causing severe harm to both animal and plant life. Natural methods of pollution removal such as degradation are not applicable to heavy metals thus they are not easy to remove from the environment [1]. The term heavy-metals is loosely defined [2], but in environmental pollution chemistry it is a general collective term used for the group of metals and metalloids with atomic densities greater than 4 g/cm3. Heavy metals include metals such as cadmium, chromium, copper, mercury, lead, zinc, arsenic, * Stephen Majoni [email protected] 1
Department of Applied Chemistry, National University of Science and Technology, P.O. Box AC939, Ascot, Bulawayo, Zimbabwe
Department of Chemical and Forensic Sciences, Botswana International University of Science and Technology, P. Bag 16, Palapye, Botswana
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boron and the platinum group metals [2]. In minute amounts, some of the heavy metals are necessary to support life, but in large amounts they are toxic [3, 4]. Unlike most environmental pollutants (such as agricultural chemicals and their metabolites, and domestic and industrial organic wastes), heavy metals occur naturally in the earth’s crust. Metals can be intr
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