Abstract Soil and sand fine particles, which may be resuspended as fine dust in the atmosphere, contain a variety of anthropogenic and natural organic compo- nents. Samples of fine soil and sand particles (sieved to <125 lM) were collected from the Riyadh area in the summer of 2003 and extracted with a mixture of dichloromethane and methanol (3:1, v:v). The deriva- tized total extracts were analyzed by gas chromatog- raphy–mass spectrometry in order to characterize the composition and sources of the organic components. Both anthropogenic and natural biogenic inputs were the major sources of the organic compounds in these extracts. Discarded plastics and vehicular emission products were the major anthropogenic sources in the fine particles from populated areas of the city. Their tracers were plasticizers, UCM, n-alkanes, hopanes and traces of steranes. Vegetation was the major natural source of organic compounds in samples from outside Riyadh and included n-alkanols, n-alkanoic acids, n- alkanes, methyl alkanoates, sterols and triterpenoids. Carbohydrates had high concentrations (42–54%) in all samples and indicate sources from decomposition of cellulose and/or the presence of viable microbiota such as bacteria and fungi. The results were also compared with the data obtained in winter 2002 and showed that anthropogenic inputs were higher in summer than in winter, whereas the opposite trend was observed for natural inputs. Keywords Biomarkers Carbohydrates Lipids Petroleum residues Plasticizers UCM Introduction Urban and industrial emissions from fossil fuel use, smoke from biomass burning, inputs from natural terrestrial plant wax and marine lipids, and secondary products derived from the oxidation of atmospheric organic matter are major sources of organic compounds in urban areas (Brooks and Maxwell 1974; Simoneit 1977, 1980, 1984, 1985; Matsumoto and Hanya 1980; Gagosian and Peltzer 1986; Mazurek et al. 1989; Rogge et al. 1993a; Schauer et al. 1996; Fraser et al. 1997, 1998a, b; Al-Mutlaq et al. 2002). Anthropogenic and biogenic organic compounds including lipids, soot, and humic and fulvic acids are also documented to be a major carbonaceous fraction in various ecosystem compartments (Ketseridis et al. 1976; Simoneit 1977, 1980, 1984, 1986, 1989; Broddin et al. 1980; Barbier et al. 1981; Marty and Saliot 1982; Simoneit and Mazurek 1982, 1989; Gagosian and Peltzer 1986; Cass et al. 1993; Schauer et al. 1996). These organic compounds include fatty acids, sterols and other lipids from terrestrial higher plants, marine biota and cooking; n-alkanes and n-alkanols from higher plant waxes; sugar-derivatives, methoxyphenols and resin acids from biomass burning; polynuclear aromatic hydrocarbons (PAH) from com- bustion processes; pesticides and herbicides from agri- cultural activities; and dicarboxylic acids and other K. Al-Mutlaq Department of Plant Protection, College of Food and Agriculture Science, King Saud University, Riyadh, Saudi Arabia A. I. Rushdi (&) B. R. T. Simoneit Environmental and Petroleum Geochemistry Group, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA e-mail: arushdi@coas.oregonstate.edu Environ Geol (2007) 52:559–571 DOI 10.1007/s00254-006-0487-7 123 ORIGINAL ARTICLE Organic compound tracers of fine soil and sand particles during summer in the metropolitan area of Riyadh, Saudi Arabia Khalid Al-Mutlaq Ahmed I. Rushdi Bernd R. T. Simoneit Received: 21 July 2006 / Accepted: 23 August 2006 / Published online: 19 September 2006 Ó Springer-Verlag 2006