Lead isotopes in marine surface sediments reveal historical use of leaded fuel† Martin M. Larsen, * ac Jerzy S. Blusztajn, b Ole Andersen c and Ingela Dahll€ of d Received 17th July 2012, Accepted 30th August 2012 DOI: 10.1039/c2em30579h Analyses of lead (Pb) isotopes have been performed in terrestrial and fresh water environments to estimate historical uses of leaded fuel, but so far this method has not been employed in studies of world- wide marine surface sediments. We analyzed Pb and its isotopes in 23 surface sediments from four continents collected during the Galathea 3 expedition in 2006–2007. To enhance the anthropogenic signal, a partial digestion using nitric acid was performed. The concentrations of Pb, Th, U and Al were determined with an ICP-Quadrupole MS, and Pb-isotope ratios with an ICP-multi-collector MS. The samples could be divided into three groups: Harbor areas in larger cities with concentrations of 150 to 265 mg kg 1 dry weight, smaller towns with concentrations between 20 and 40 mg kg 1 dry weight, and remotely located sites with concentrations below 15 mg kg 1 dry weight. Pb-isotope ratios were compared to literature values for gasoline and local or geological background values, and the contribution of leaded-gasoline to total concentrations was calculated for contaminated sites using both a one-dimensional and a novel two-dimensional (vector) method. The North American sites had Pb-isotope ratios corresponding to the US leaded gasoline, with 24–88% of the Pb from leaded gasoline. Samples from Oceania showed Pb-isotope ratios corresponding to Australian gasoline, with 60% attributed to leaded gasoline in Sydney and 21% in Christchurch. Outside Cape Town, 15 to 46% of Pb in sediments was from leaded gasoline. 1. Introduction The emissions of lead (Pb) from leaded gasoline have been esti- mated to be a factor of 10–100 times larger than other sources of anthropogenic and natural environmental inputs during the 1950’s to 1980’s, 1 with an average estimated emission of Pb from leaded gasoline of 10 5 tons per year. The catalytic converter introduced in cars in the 1970’s was incompatible with leaded gasoline, and in the late 1980’s leaded gasoline was banned in the US. A ban was enforced in the EU in 2000, in Australia from 2002, 2 and in Africa from 2006. 3 Today, only six countries still use leaded gasoline: Afghanistan, North Korea, Myanmar, Algeria, Iraq and Yemen. These countries are expected to elim- inate leaded gasoline by 2013 according to the UN. 4 In spite of these bans, the main source of anthropogenic Pb in the environment is still leaded gasoline. Pb has four stable isotopes: 204 Pb (1.4%), 206 Pb (24%), 207 Pb (23%) and 208 Pb (52%). 204 Pb is the only non-radiogenic isotope, as the other isotopes are produced by the radioactive decay of 238 U to 206 Pb (decay half-time of the parent isotope t 1/2 ¼ 4.466  10 9 a Aarhus University, Department of Bioscience, Frederiksborgvej 399, DK-4000 Roskilde, Denmark. E-mail: mml@dmu.dk; Tel: +45 8715 5000 b Woods Hole Oceanographic Institution, 266 Woods Hole Rd. MS# 25 Woods Hole, Ma. 02543, USA. E-mail: jblusztajn@whoi.edu c Roskilde University, Department of Science, Systems and Models, Universitetsvej 1, 4000 Roskilde, Denmark. E-mail: oa@ruc.dk d Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden. E-mail: ingela. dahllof@gu.se † Electronic supplementary information (ESI) available: More information on lead isotopes, correlation between Th/Pb and U/Pb and lead isotope ratios and example calculation of leaded gasoline contribution. See DOI: 10.1039/c2em30579h Environmental impact This world-wide survey shows that the historical use of leaded fuel is still a major source of lead in surface sediments near larger cities on at least 3 of 4 continents. Data on isotope patterns in leaded fuel from Europe, USA, Mexico and Australia were collected from the literature and used to assess the contribution of leaded fuels to lead content in 9 locations around the world. A more elaborate calculation method for source-appointment is suggested, and compared to the usual method of single isotope ratio calculation. The use of non-total digest is less sensitive to the geological background, as indicated by comparison of lead isotope signatures from volcanic and continental sites with expected geological signatures of basalt and crustal rocks. This journal is ª The Royal Society of Chemistry 2012 J. Environ. Monit. Dynamic Article Links C < Journal of Environmental Monitoring Cite this: DOI: 10.1039/c2em30579h www.rsc.org/jem PAPER Downloaded by Aarhus University Library on 05 October 2012 Published on 06 September 2012 on http://pubs.rsc.org | doi:10.1039/C2EM30579H View Online / Journal Homepage