Metal status of olive trees grown in southeastern marmara region of Turkey

Abstract

Black table olive production is concentrated in the southeastern Marmara Region of Turkey, which is one of the most important agricultural areas of the country with highly fertile soils. Soil pollution has become an important concern for arable lands as a result of intensive agriculture and urban-industrial expansion in the region. This study was conducted to characterize the metal accumulation in the soils, fruits, and leaves of Oleaeuropea L. in the orchards located in southeastern Marmara Region. The research was performed in 64 orchards with cv. Gemlik table olive trees in the towns of. Iznik, Orhangazi, Gemlik, Mudanya, and Nilufer of Bursa Province in the region. To determine levels of pollution, soils and aboveground parts of the trees were sampled and analyzed for iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cobalt (Co), nickel (Ni), chromium (Cr), lead (Pb), and cadmium (Cd). Total amounts of Ni and Cr were found to be excessive in soils. Cadmium, Co, and Cu concentrations were slightly greater than the permissible ranges in a minority of the soils tested The concentrations of these elements, however, were not at the toxic levels in the different plant parts. Because of lack of standard concentrations indicating excessive concentrations of extractable elements, statuses of extractable elements in the soils were not evaluated. Except for Zn in some fruit samples and Cu in some fruit and leaf samples, metal accumulation in the trees were not estimated by both leaf and fruit analysis. Concentration of total and diethylenetriaminepentaacetic acid (DTPA)-extractable metals in the soils did not correlate with the plant content of the metals. Therefore, total and DTPA-extractable metal concentrations were not reliable and descriptive in estimating metal concentrations in olive trees. As a result, the appearance of metals in soils might be due to agricultural activities and parent material. Continuous monitoring and future studies of the olive orchards are recommended to ascertain long-term impacts of pollution on the trees.