U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Impact of 70 years urban growth associated with heavy metal pollution

Rodríguez Martín, J.A., De Arana, C., Ramos-Miras, J.J., Gil, C., Boluda, R.
Environmental pollution 2015 v.196 pp. 156-163
aluminum, arsenic, botanical gardens, cadmium, calcium, chromium, combustion, copper, fuels, heavy metals, herbaria, humans, interspecific variation, iron, lead, leaves, magnesium, manganese, nickel, pollution, sodium, urbanization, zinc
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.