ABSTRACT

The study assessed the physicochemical properties and heavy metals (chromium (Cr), zinc (Zn), cadmium (Cd), and copper (Cu)) levels in sawdust, soil and plants at Ahiaeke timber market, Umuahia, Nigeria using Flame Atomic Absorption Spectrometer (AAS) in order to ascertain the impact of timber market on the surrounding environment. Sawdust was collected randomly from fifteen different sampling points in four cardinal points (i.e. three sampling points each at north (N), south (S), east (E), west (W), and at the center (C) of the dumps from three dump. Soil samples were collected randomly from twelve different sampling points at 0-10, 11-20, and 21-30 cm soil depth with well cleaned Dutch soil auger in four cardinal points (i.e. two sampling points each at north (N), south (S), east (E) and west (W) of 20, 40, 60 and 80 m from the center of the sawdust wastes each dumpsite, and control was taken 500 m away from dumpsite. Plant samples were also collected at the same point where soil was sampled. The highest values of P (1.103±0.12 %), Organic carbon (27.98 ± 0.021%) and K (2.2± 0.04 %) of sawdust particles were obtained at sawdust dump 2 and these values are significantly (P< 0.05) higher than their corresponding values in sawdust dump 1 (0.805±0.013, 24.15±0.165 and 1.83±0.061 %) and sawdust dump 3 (0.94±0.050, 25.614±0.785 and 2.073±0.006 %).  The mean values of soil pH ranges from 6.03±0.115 to 3.67±0.28 indicating that the soil is acidic. The highest concentration of Zn (51.00±1.84 mg/kg) and Cr (0.170±0.014 mg/kg) was observed at the sawdust dump 2; Cu (8.24±0.60 mg/kg) was obtained at the sawdust dump 1 while Cd (4.72±0.071 mg/kg) occurred at the sawdust dump 3. The values of the highest concentration of Zn (119.7±7.02 mg/kg), Cu (75.85±4.80 mg/kg) and Cd (22.39±3.30 mg/kg) in soil were observed in 0-10 cm depth at the distance of 20 m. The values of Zn (119.7±7.02 mg/kg) and Cd (22.39±3.30 mg/kg) in soil is above the maximum permitted levels of 60 mg/kg (Zn) and 0.1 mg/kg (Cd) established by the Codex Alimentarius Commission. The highest concentration of Zn (34.70±7.05 mg/kg), Cu (5.34±0.11 mg/kg) and Cd (2.94±0.515) in plants was assimilated by Centrosema pubescence. The level of Cd in plants is well above the permissible limit (PL) 0.3 mg/kg set by FAO/WHO for vegetables and herbs. Consumption of such contaminated C. pubescence can be a route of entry of Cd in grazing animals’ vis-à-vis the people who depend on such herbivores for protein.