Land use patterns influence the distribution of potentially toxic elements in soils of the Usangu Basin, Tanzania

• Published in: Chemosphere (Oxford) Vol. 284; p. 131410
• Main Authors: Mng'ong'o, Marco, Comber, Sean, Munishi, Linus K., Ndakidemi, Patrick A., Blake, William, Hutchinson, Thomas H.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2021
• Subjects: Agriculture; agroecosystems; aqua regia; basins; bioavailability; cadmium; chromium; community forestry; copper; corn; environmental assessment; Hazard assessment; Irrigation; land use; lead; paddies; Paddy farming; Risk management; Tanzania; Toxic elements; toxicity; Tanzania; Irrigation; Agriculture; Risk management; Hazard assessment; Paddy farming; Toxic elements
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.131410

Spatial distribution of Potentially Toxic Elements (PTEs) in agricultural soils in Usangu Basin (Mbeya Region)-Tanzania were conducted. The study included three land-use types (paddy farming, maize farming, and conserved community forest areas). About 198 soil samples were collected from November to December 2019 across contrasting land management schemes (Group I dominated by agricultural areas versus Group II dominated by residential and agricultural areas). Total (aqua regia extracts) and bioavailable (Mehlich 3 extracts) PTEs concentrations were analyzed. For Group I and II areas, total and bioavailable concentrations (mg/kg dry weight, mean values) of some PTEs were: chromium 1662 ± 5.2 μg/kg for Group I and 1307 ± 3.9 μg/kg for Group II (Total), 55.1 ± 37.1 μg/kg for Group I and 19.2 ± 21.6 μg/kg for Group II (bioavailable); and lead 5272 ± 1650 μg/kg for Group I and 6656 ± 1994 μg/kg for Group II (Total), 1870 ± 800 μg/kg for Group I and 1730 ± 530 μg/kg for Group II (bioavailable). Soil total PTEs such as cadmium and lead were generally lower in Group I areas than in Group II areas. The reverse scenario was observed for copper. Farming areas had high PTEs concentration than non-farming areas because of anthropogenic activities. Overall, soil total concentrations of Fe (99.5%), As (87%), Se (66%), and Hg (12%) were above Tanzanian Maximum Allowable Limits. This study provides essential baseline information to support environmental risk assessment of PTEs in Tanzanian agro-ecosystem. •Agricultural intensification is likely to increase environmental contamination, including Potentially Toxic Elements (PTEs).•The spatial distribution of PTEs in surface soils has been investigated in Usangu Basin-Tanzania.•Total and bioavailable PTEs determined in 3 land use.•Farming areas had higher PTEs concentration than non-farming areas because of anthropogenic activities and intensification.•Soil total concentrations of Fe, As, Hg and Se were above permissible limits.