Recording chemical changes in an urban environment: A dendrochemical study of Ceiba speciosa (A. St.-Hil.) Ravenna (Malvaceae) in the Atlantic Forest

Abstract

Trees are capable of recording in their wood the environmental conditions they experience, earning them recognition as environmental archives. Dendrochemistry relates wood chemistry to environmental chemistry and internal biological processes that influence the absorption and incorporation of chemical elements into growth rings. We evaluated the annual concentrations of chemical elements fixed in the wood of Ceiba speciosa (A. St.-Hil.) Ravenna (Malvaceae) at two Atlantic Forest locations, representing low and high urbanization, in the city of Rio de Janeiro, Brazil. The samples used had been dated in a previous dendrochronological study and each growth ring was subjected to energy dispersive X-ray fluorescence (EDXRF). Eleven chemical elements were detected in the growth rings of Ceiba speciosa at both study sites. Concentrations varied among evaluated years and between sites, showing a positive relationship between concentrations accumulated in wood and concentrations present in the soil where the plants develop. The levels of potentially toxic elements in the wood increased significantly at the urban site, mainly since the end of the 1980s. The increase in the concentration of potentially toxic chemical elements in the xylem due to urbanization is a process little discussed for tropical species. In this sense, the dendrochemical study of Ceiba speciosa in the city of Rio de Janeiro represents an important historical environmental report for the Atlantic Forest. The present results, combined with those obtained previously in relation to cambial activity and wood anatomy and tree growth rates of wood and trees in urban environments, indicate that Ceiba speciosa has potential as an important biomarker in environmental monitoring studies.