Reconstructing historical trends of polycyclic aromatic hydrocarbon deposition in a remote area of Spain using herbarium moss material

Herbarium mosses from 1879–1881, 1973–1975 and 2006–2007 were used to investigate the historical changes of atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) at a remote site in Northern Spain. Natural abundance of nitrogen and carbon isotopes was also measured in order to assess the evolution of emissions from anthropogenic sources. Nitrogen and PAH concentrations as well as δ13C and δ15N ratios were significantly higher in 19th century samples compared to present century samples. Moreover, PAH distribution varied over the centuries, with the trend towards enrichment in light PAHs. The carbon, nitrogen and PAH concentrations measured in the mosses tally with the historical evolution of anthropogenic emissions in the area, mainly influenced by changes in economic activities, domestic heating and road traffic density. Mosses provided by herbaria seem to offer the possibility of studying long-term temporal evolution of atmospheric PAH deposition.