Chronological Study of Metallic Pollution Using Tree Rings at Tema Industrial Area

Tree rings have been used to reconstruct past climates as well as to assess the effects of recent climatic and environmental changes on tree growth. Industrial emission is one of the major sources of pollutants in the atmosphere. This study determined heavy metals pollution chronologies from industrial emissions in the atmosphere of the Tema industrial area of Ghana using tree-rings as bio-indicators. Swietenia mahagoni (Mahogany) tree was bored and the rings counted and age determined to be 50 years spanning from 1968 to 2018. Tree growth rates were calculated through ring width measurements and related to annual precipitation data spanning over the sampling period. It was observed that wet seasons correlate with high growth rates of trees while low precipitation seasons correspond to low or no growth rate of trees. Energy Dispersive X-ray fluorescence (EDXRF) was used to investigate the presence and concentration of the four heavy metals (Cu, Zn, Fe and Pb). Concentration of Cu, Zn, Fe and Pb ranged from (1.92—6.70 mg/kg), (5.37 – 13.9 mg/kg), (0.10 – 0.36 mg/kg) and (12.13—90.13 mg/kg), respectively. Surprisingly, an increasing trend in concentration was observed for Zn and Cu with levels higher than the WHO guideline for heavy metals in the plant.