Heavy metals in soil of three agroforestry systems: a preliminary study for source identification and ecological risk

The contamination of heavy metals in agroforestry soils around the industrial area, Bangladesh is drawing more and more attention. This study investigates the concentration of chromium (Cr), nickel (Ni), copper (Cu), arsenic (As), cadmium (Cd), lead (Pb), manganese (Mn), and zinc (Zn) in soils of three agroforestry systems and their role on the soil ecology in a tropical moist deciduous forest in Tangail, Bangladesh. Heavy metals in soil samples were analysed by inductively coupled plasma mass spectrometer following acid digestion. The soils in the agroforestry practiced field increased organic matter content. In soil samples, the pH was ranged from 5.33 to 6.35, the electrical conductivity was ranged from 0.89 to 1.22 dS/m, CEC was ranged from 12.1 to 23.5 (Cmol kg-1) and the range of organic carbon was 1.05-2.02%. Average value of trace elements (mg/kg) in soil samples were listed in decreasing order of Mn (121.7) > Zn (80.9) > Cu (42.0) > Ni (28.6) > Cr (18.1) > Pb (16.0) > As (9.7) > Cd (1.9). The ecological risk index indicates that soils in the agroforestry systems had considerable to high ecological risk. Therefore, it is essential to develop functional concepts of urban-agroforestry systems with land-uses soils adapted to Bangladesh's current circumstances and ecosystem services to protect the ecology of the largest shal forest.