Trace metal speciation trends in Mazowe dam, Zimbabwe, a typical sub-tropical dam ecosystem impacted by gold mining and agriculture

• Published in: Environmental geochemistry and health Vol. 46; no. 9; p. 348
• Main Authors: Mandizha, Naume Tivirayi, Kugara, Jameson, Mombeshora, Edwin T., Zaranyika, Mark Fungayi
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-09-2024; Springer Nature B.V
• Subjects: Agricultural ecosystems; Agriculture; Aluminum; Aquatic ecosystems; Cadmium; Chemical speciation; Chromium; Cobalt; Copper; Correlation analysis; Correspondence; Earth and Environmental Science; Ecosystem; Environment; Environmental Chemistry; Environmental Health; Environmental impact; Environmental Monitoring - methods; Geochemistry; Geologic Sediments - chemistry; Gold; Gold mines & mining; Heavy metals; Iron; Lead; Manganese; Mercury; Mercury (metal); Metals - analysis; Metals, Heavy - analysis; Mining; Nickel; Public Health; Sampling; Sediment; Sediments; Soil Science & Conservation; Speciation; Species; Terrestrial Pollution; Trace Elements - analysis; Trace metals; Trends; Visual observation; Water circulation; Water column; Water Pollutants, Chemical - analysis; Zimbabwe; Zinc; Zimbabwe; Metal species correlation; Sequential extraction; Trace metal speciation; Geochemical computer modelling; Aquatic ecosystem; Trace metals
• ISSN: 0269-4042; 1573-2983; 1573-2983
• DOI: 10.1007/s10653-024-02117-w

The present study aimed to assess trace metal speciation trends in the water and sediments of Mazowe Dam, a typical sub-tropical dam ecosystem impacted by gold mining and agriculture in Zimbabwe. The elements studied include Al, As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, and Zn. Elemental speciation in the water column was determined using Visual MINTEQ version 3.1 geochemical computer modelling, while speciation in the sediment phase was determined using sequential extraction techniques. For each element, the data obtained were subjected to extensive correlation analysis to identify intra- and inter-metal species interactions in the water column and the sediment phase, as well as across the water–sediment interface. Possible mechanisms to account for the observed species interactions are proposed. In the water column, Co was predicted to have the highest number of chemical species (9), Cd and Zn (8), Mn and Fe (7), Ni (6), Pb (5), Al and Cu (3), Cr, Hg, and As have the least (2). In the sediment, Al, As, Co, Cr, Cu, Fe, Ni and Fe mainly exist in the residual fraction, while Zn and Mn concentrations in fractions vary per sampling site, with no fraction that is dominant across the sampling sites. Equilibrium exchange reactions across the water–sediment interface were observed e.g., for Cd species /FA
2
Cd (aq) and Co species /FACo
+2
G (aq), and /FA
2
Co (aq). This study is valuable in highlighting trace metal speciation in a tropical dam ecosystem in Africa and adds to the growing knowledge about the behaviour of trace metals in aquatic ecosystems in the region and globally.