Background levels of polybrominated diphenyl ethers (PBDEs) in soils from Mount Meru area, Arusha district (Tanzania)

• PBDEs contamination in mountain soils from Mount Meru, Tanzania, was measured.
• Moderate PBDE levels showing relationship with altitude were found.
• Mount Meru PBDE levels were similar to those from other high mountain areas.
• Levels were comparable to those found in mountain soils from the northern hemisphere.

This study investigates the contamination by 13 polybrominated diphenyl ether (PBDE) congeners in an altitudinal soil transect on Mt. Meru area, Northern Tanzania. A ∑13PBDEs mean concentration of 386 ± 200 pg/g d.w. (4900 ± 3500 pg ∑13PBDEs/g soil organic matter — SOM) was measured, pointing out that, in a prevalently agricultural area from the southern hemisphere, PBDE contamination can be even higher than in similar semi-remote environment of industrialized country of the northern one. The Mt. Meru PBDE pattern of contamination was characterized by the prevalence of intermediate brominated congeners (tetra- and penta-BDEs). Among the detected compounds, BDE-47 was the main congener, followed by BDE-99, BDE-190 and BDE-100. The distribution of PBDEs confirmed that organic carbon had a substantial impact on their accumulation in Tanzanian soils. The altitudinal profile of PBDEs (log TOC-normalized concentrations) fitted a second order polynomial model with altitude, with an initial concentration decrease, interpreted as a dilution effect from local/regional sources, and a following consistent increase with altitude according to the cold condensation theory. Evidences of distillation effect among PBDE congeners were also observed.