Arch. Environ. Contam. Toxicol. 49, 457–470 (2005) DOI: 10.1007/s00244-004-0002-7
Sources of Organic Compounds in Fine Soil and Sand Particles During Winter in the Metropolitan Area of Riyadh, Saudi Arabia Ahmed I. Rushdi,1 Khalid Al-Mutlaq,2 Bernd R. T. Simoneit1 1
Environmental and Petroleum Geochemistry Group, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA 2 College of Food and Agriculture Science, King Saud University, Riyadh 11451, Saudi Arabia
Received: 8 January 2004 /Accepted: 30 April 2005
Abstract. Major advances have been made in molecular marker analysis to distinguish between natural and anthropogenic organic matter inputs to the atmosphere. Resuspension of soil and sand by wind is one of the major mechanisms that produces particle dusts in the atmosphere. Soil and sand samples from the Riyadh area were collected in winter 2002, sieved to remove coarse particles and extracted with a mixture of dichloromethane and methanol (3:1, v:v). The total extracts were analyzed by gas chromatography–mass spectrometry in order to characterize the contents and identify the potential sources of the organic components. The major organic compounds of these extracts were derived from natural biogenic and anthropogenic sources. Organic compounds from natural sources, mainly vegetation, were major in samples from outside the city of Riyadh and included n-alkanes, n-alkanoic acids, n- alkanols, methyl alkanoates, and sterols. Anthropogenic inputs were significant in the fine particles of soil and sand samples collected from populated areas of the city. They consisted mainly of n-alkanes, hopanes, UCM (from vehicular emissions), and plasticizers (from discarded plastics, e.g., shopping bags). Carbohydrates had high concentrations in all samples and indicate sources from decomposed cellulose fibers and/or the presence of viable microbiota such as bacteria and fungi.
Natural emissions of terrestrial plant wax and marine lipids, smoke from biomass burning, urban/industrial emissions from fossil fuel use, and secondary products derived from the oxidation of atmospheric organic matter are the major sources of organic compounds in urban atmospheres (Fraser et al. 1997, 1998a,b; Matsumoto and Hanya 1980; Mazurek et al. 1989; Rogge et al. 1991, 1993 a–e, 1994, 1996, 1997a,b, 1998; Simoneit 1977, 1980, 1984). Biogenic and anthropogenic organic compounds including lipids, soot, and humic and fulvic acids are documented to be a major carbonaceous fraction in the
Correspondence to: Ahmed I. Rushdi; email:
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global atmosphere (Barbier et al. 1981; Broddin et al. 1980; Cass et al. 1993; Gagosian and Peltzer 1986; Ketseridis et al. 1976; Marty and Saliot 1982; Schauer et al. 1996; Simoneit 1977, 1980, 1984, 1986, 1989; Simoneit and Mazurek 1982, 1989). These compounds include (1) fatty acids, sterols, and other lipids from terrestrial higher plants, marine biota, and cooking; (2) n-alkanes and n-alkanols from higher plant waxes; (3) sugar derivatives, methoxyphenols, and resin acids from biomass burning; (4) polynuclear aromatic hydrocarbons (PAH) from combustion processes, and (5) dicarboxylic acids and other polar oxidation products (Abas and Simoneit 1996, Abas et al. 1995, Gagosian et al. 1981, 1987, Rogge et al. 1991, 1993a–e, 1994, 1996, 1997a, 1997b, 1998, Simoneit 1980, 1984, 1986, 1989; Simoneit and Mazurek 1982; Simoneit et al. 1988, 1990, 1991a, 1991b, 1991c, 1993; Standley and Simoneit 1987). An additional input of biogenic and anthropogenic matter to the atmosphere is from soil resuspension occurring by natural, as well as man-made processes (e.g., Rogge et al. 1993a; Simoneit 1980). Resuspension of dust can occur on various scales, such as local particle resuspension, agriculture and construction related operations, road dust in urban and rural areas, as well as transport from desert and semiarid regions such as on the Arabian Peninsula. Dust particles remain suspended in the atmosphere for a considerable time, and they become deeply imbedded in human lung tissue, causing respiratory problems and other cardiovascular diseases (Morgan 1986; Meijer et al. 2001). The occurrence of pollutants in dust not only affects atmospheric chemistry but also the health of humans and vegetation of the area (ATS 1997; Berny et al. 1994; Gerr et al. 2000; Guieu 2002; Ridgwell 2002; Plumlee and Ziegler 2004). The effects of pollutants and toxic substances on animals and plants vary widely (Ridgwell 2002; Saad et al. 2003). In humans, they range from body temperature change and abnormal skin color to damage to the immune system and ultimately death (Morgan 1986). Surface soils, sands, and road dusts contain organic matter derived from many sources. These have not been characterized for the Arabian Peninsula region. Thus, the major purpose of this article is to identify the higher molecular weight organic tracers in fine particles of soil and sand from the Riyadh area, Kingdom of Saudi Arabia. It is a first attempt to evaluate the potential sources of the organic matter.
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Table 1. Locations and descriptions of soil and sand samples collected in November 2002 from the Riyadh metropolitan area, Saudi Arabia. Sample code (see Fig. 1)
Location
Description
O—R OF—R MoH CC—R Az—R SD
Outside the city, close to highway traffic Outside the city, from palm tree farm Ministry of Health locale, in the city City center Azizia market place in the city Sand dune about 50 miles north of the city (vicinity of picnic area)
Mostly sand Mostly soil Mixture of soil and sand Mixture of soil and sand Mixture of soil and sand All sand
Fig. 1. Map showing the collection locations of the sand and soil samples
Experimental Methods Sampling and Extraction Procedure Six soil and sand samples were collected in November 2002 from the metropolitan area of Riyadh in Saudi Arabia to characterize their organic matter contents by gas chromatography–mass spectrometry (GC-MS) analysis. The locations and descriptions of the samples are given in Table 1 and shown in Figure 1. All samples, except SD, were collected in Riyadh and represent urban areas ranging from populated with different human activities such as public markets (Az-R, CCR) and governmental (MoH) sites to rural areas where human activities are limited (O-R and OF-R). The SD sand sample was collected about 50 km northeast of Riyadh, where only sand dunes were dominant and no vegetation was observed. Each sample was sieved to obtain fine particles (C20) in the lipids (e.g., Fig. 3c,d), with primarily only the even carbon number homologs. The nalkanoic acids (
