| Abstract: | We determined heavy metal, polycyclic aromatic hydrocarbon (PAH), and polychlorinated biphenyl (PCB) concentrations in 18 topsoils of Uberlândia (420,000 inhabitants, Brazil) and in 3 rural topsoils. Concentrations of Al (11—124 g kg—1) and Fe (13—109 g kg—1) are large because of desilification. Concentrations of Cd (0.1—0.5 mg kg—1), Cr (13—72), Cu (6—154), Mn (28—974), Ni (4—29), Pb (3—26), Zn (4—107), the sum of 20 PAHs (=Σ20PAHs:7—390 μg kg—1), and the sum of 14 PCBs (=Σ14PCBs:0.05—1.25) are comparable to or below background concentrations in temperate soils except for Cu at two sites. More than 67% of the metals are strongly bound in Fe oxides and silicates; metals are more bioavailable in the urban than in the rural soils. The most abundant PAHs in the urban soils, on average, are naphthalene (19.0 ± 13.4% of Σ20PAHs) and the benzo(b+j+k)fluoranthenes (11.4 ± 6.7%); the most abundant PCBs are nos. 138 (23.3 ± 11.0% of Σ14PCBs) and 153 (14.3 ± 6.4%). The rural soils contain larger percentages of low molecular PAHs and up to tetra‒chlorinated PCBs than the urban soils. The different pollutant concentrations and patterns in the studied tropical compared with many temperate soils indicate different sources and fate. |
