City monuments act as passive samplers, with spectroscopy and crystallography allowing heavy metals to be analyzed at trace levels from surface samples.

Researchers suggest that monuments in cities heavily polluted by vehicle exhausts can act as passive samplers of heavy metal pollution. As proof of principle, infrared spectroscopy and X-ray crystallography were used to quantify platinum and rhodium at trace level from samples taken from the surfaces of monuments. These two metals have become tracers of vehicle emissions since catalytic converters were introduced. Moreover, their presence is important in the conservation of cultural heritage as the metals can have catalytic effects on the decay reactions of construction materials.

• Monuments as sampling surfaces of recent traffic pollution
  L. Rampazzi, B. Giussani, B. Rizzo, C. Corti, A. Pozzi, C. Dossi,
  Environ. Sci. Pollution Res. 2010, 17.
  DOI: 10.1007/s11356-010-0363-6