title: Impact of 70 years urban growth associated with heavy metal  pollution.
abstract: Historical trends in trace element deposition were analyzed using herbaria specimens. We determined Al, Fe, Mg, Mn, Ca, Na, P, K, S, As, Cd, Cr, Cu, Ni, Pb and Zn contents in leaves of eight specimens collected in 1941. To assess changes, we collected the same plants from a botanical garden in 2012. The concentrations of major elements showed large species variability. However, temporal trends were predominately detected for heavy metals. The Cd, Ni and Cr contents in the 2012 leaves were 10, 13 and 16 times higher, respectively, than in 1941. Urban activities have substantially raised the levels of these metals in urban atmospheres due to changes in human activities over 70 years of urban growth. Nevertheless, Pb has decreased (126%) in recent decades thanks to controlled lead fuel combustion. In short, metal deposition trend to increase Cr, Ni and Cd levels.
authors.affiliation: Dept. Environment, Instituto Nacional de Investigacion y Tecnología Agraria y Alimentaria (I.N.I.A), Ctra. de A Coruna 7.5, 28040 Madrid, Spain. rmartin@inia.es
authors.forename: J A
authors.initials: JA
authors.lastname: Rodríguez Martín
authors.forename: C
authors.initials: C
authors.lastname: De Arana
authors.forename: J J
authors.initials: JJ
authors.lastname: Ramos-Miras
authors.forename: C
authors.initials: C
authors.lastname: Gil
authors.forename: R
authors.initials: R
authors.lastname: Boluda
mesh_terms: D002947:Cities / Q000706:statistics & numerical data*; D004784:Environmental Monitoring / Q000379:methods*; D004787:Environmental Pollution / Q000706:statistics & numerical data*; D006801:Humans; D008670:Metals; D019216:Metals, Heavy / Q000032:analysis*; D011158:Population Growth; D014131:Trace Elements / Q000032:analysis
chemical_list: D008670:Metals; D019216:Metals, Heavy; D014131:Trace Elements