δ13C variations in tree rings as an indication of severe changes in the urban air quality

Abstract

Annual growth rings sampled from three free-standing trees (Platanus hybrida sp.), grew in the metropolitan area of Palermo (Italy) and covering a 118 years time span (1880-1998), have been studied for their 13C/12C carbon isotope ratios. It has been found that the 13C/12C tree ring record, during the study time interval, decreased of -3.6‰, from -26.4‰ in 1880 to -30‰ in 1998. Such a progressive depletion has been attributed to the addition of anthropogenic 13C depleted carbon dioxide to the local atmosphere. The observed 13C/12C decrease has been used to infer some possible pathways of atmospheric CO2 change in the study urban area.