Concentrations of heavy metals in Eucalyptus and Pinus wood sawdust and smoke, Copperbelt province, Zambia
MADERAS : Ciencia y Tecnología
The bulk of exotic forest plantations and sawmills in Zambia are within the reach of air pollutants from mines on the Copperbelt province. Up to 60% of every cubic meter of the timber processed is waste, of which 0,12 m 3 is sawdust. Sawdust is largely used for various surface amendments and as a source of energy, but the dangers it poses to users are not known. Heavy metals assimilated by trees or adsorbed by sawdust from the environment may be a health hazard at certain levels. The amount of
... els. The amount of heavy metals in Eucalyptus and Pinus sawdust was evaluated on samples from Kitwe and Ndola to establish if the use of sawdust for energy and surface amendments was safe. Composite samples for each wood type were collected from each site and digested. The ensuing solution was filtered and analyzed by flame emission Atomic Absorption Spectroscopy for heavy metals. Smoke from a burning test was trapped on Whateman 41 filter paper and the particulate matter that was trapped was extracted. The extract mixture was centrifuged to obtain a clear solution which was then analyzed for heavy metals by AAS. The heavy metal concentrations in Eucalyptus sawdust were 11,5-61,1 mg Pb/kg; 3,3-7,9 mg Cd/kg; 4,9-56,9 mg Cr/kg and 20,2-43,4 mg Ni/kg while that in Pinus sawdust were 17,1-32,8 mg Pb/kg; 5,1-8,6 mg Cd/kg; 9,9-28,2 mg Cr/kg and 18,7-67,4 mg Ni/kg. The concentrations of chromium and cadmium in both wood types from Kitwe exceeded the limit, and so the sawdust was deemed unsuitable for surface applications. This was the same for nickel in Pinus sawdust. The study showed that sawdust from both wood types was not safe for mulching, composting and animal bedding. The annual exposure limits of 0,2 μg Cr/m 3 , 180 μg Ni/m 3 and 0,2 μg Cd/m 3 set by the World Health Organization were not exceeded by the smoke from both wood types. This suggested that heavy metals embedded on particulate matter from Eucalyptus and Pinus sawdust which has been in storage for about two years in conditions found in Kitwe is unlikely to have adverse short-term health effects associated with heavy metals. Aksoy, A.; Sahin, U.; Duman, F. 2000. Robinia pseudoacacia L. as a possible biomonitor of heavy metal pollution in Kayseri. Turkish Journal of Botany 24(5): 279-284. Ambulkar, N.M.; Chutke, N.L.; Aggarival, A.L.; Garg, A.N. 1994. Multi elemental analysis of ambient air dust particulate from a cement factory by Neutron activation. Sci Total Environ 141: 93-101. Audu, A.A.; Lawal, A.O. 2005. Variation in metal contents of plants in vegetable garden sites in Kano metropolis. Journal of Applied Science and Environmental Management 10(2): 105-109. Baltrenaite, E.; Butkus, D.; Booth, C. 2010. Comparative of three tree-ring sampling methods for trace metal analysis. Journal of Environmental Engineering and Landscape Management 18(3): 170-178. British Standard Institution. BSI. 2012. Specification for the requirements and test methods for processing waste wood. Publicly Available Specification. London Butcher, S.S.; Sorenson, E.M. 1979. A study of wood stove particulate emissions. Journal of the Air Pollution Control Association 29(7): 724-728. Cambra, K.; Martnez, T.; Urzelai, A.; Alonso, E. 1999. Risk analysis of a farm area near a lead and cadmium-contaminated industrial site. Journal of Soil Contamination 8(5): 527-540. Chaiyo, U.; Garivait, S.; Wilairat, D. 2011. Trace element and carbon content in particulate emission from tropical deciduous forest fire Chiangmai. A summary of the emissions characterisation and noncancer respiratory effects of wood smoke. O. o. A. Q. P. Standards, US Environmental Protection Agency. Kord, B.; Mataji, A.; Babaie, S. 2010. Pine (Pinus eldarica Medw.) needles as indicator for heavy metals pollution. International Journal of Environmental Science and Technology 7(1): 79-84.