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Composition of extractable organic matter in aerosols from urban areas of Rio de Janeiro city, Brazil
Atmospheric Environment 33 (1999) 4987}5001
Composition of extractable organic matter in aerosols from urban areas of Rio de Janeiro city, Brazil DeH bora de Almeida Azevedo*, Larissa Silveira Moreira, Denilson Soares de Siqueira Instituto de Qun& mica, Universidade Federal do Rio de Janeiro, Centro de Tecnologia, Bl. A, Sala 607, Ilha do FundaJ o, Rio de Janeiro, Brazil Received 19 October 1998; accepted 11 May 1999
Abstract The hydrocarbon compositions of atmospheric particulate matter from urban areas of Rio de Janeiro city have been studied to assess the di!erent pollution levels. Samples were acquired using a standard high-volume air sampler (Hi-Vol), extracts were prepared and fractionated into aliphatic and aromatic compounds. High-resolution gas chromatography and GC coupled to mass spectrometry (GC}MS) were used for the analysis of the organic matter. The results show that all samples contain n-alkanes, but the distributions are di!erent for each sample, re#ecting both the biogenic (vascular plant wax input) and fossil fuel contamination sources (vehicular exhaust). The fossil fuel biomarkers, hopanes and steranes, were also observed in all samples except in the Tijuca Forest, which is a mountain forest in the midst of the sea-level city. A decrease in the level of pollution was observed in the sequence for Rebouc7 as Tunnel'Cinela( ndia (downtown)'Quinta da Boa Vista Park'Tijuca Forest, as expected from the tra$c density. Unfortunately, all sites are polluted mainly from vehicular emissions, but at di!erent degrees, with the lowest levels in Tijuca Forest. ( 1999 Elsevier Science Ltd. All rights reserved. Keywords: Urban air pollution; PAH; Hydrocarbons; Air quality; Particulate matter
1. Introduction The transport of pollutants through the atmosphere often gives rise to the direct uncontrolled exposure of large populations to toxic substances. This is especially relevant in urban areas where the levels of several pollutants is higher and the proximity between humans and pollutant sources is closest. Thus, a direct cause}e!ect relationship between the atmospheric release of allergenic products and urban asthma outbreaks, has been documented. In addition, many organic compounds, i.e. polyaromatic hydrocarbons (PAH), found in urban air, have been proved to be mutagens or carcinogens. It has been demonstrated, for example that mutagens a!ecting
* Corresponding author. E-mail address: [email protected] (D. de Almeida Azevedo)
S. typhimurium are present in particle samples from urban combustion sources, including catalyst-equipped auto exhaust, non-catalyst auto exhaust, diesel truck exhaust, wood smoke, distillate fuel oil combustion aerosol, and natural gas combustion aerosol (Hannigan et al., 1994). The subfractions that contain unsubstituted PAH are responsible for a considerable portion of the mutagenic potency of the whole atmospheric sample (Hannigan et al., 1998). Hydrocarbons are widespread components, which belong to the carbon cycle of the environment. Natural aliphatic and aromatic hydrocarbons (HCs) produced by continental and marine plants, are generally encountered at trace levels, with characteristic components or distributions re#ecting their origin. Anthropogenic HCs are widely distributed, originating from petroleum products and from the combustion of fuels, like crude or re"ned petroleum derivatives, coal, wood, etc. Thus, the source of anthropogenic HCs is mostly over the industrialized
1352-2310/99/$ - see front matter ( 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 2 7 0 - 8
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regions of continents, associated with industrial and urban activities (Rogge et al., 1993a,b; Schauer et al., 1996). Detailed studies of the atmospheric levels of PAHs and of total suspended particulate matter have been investigated in Rio de Janeiro in 1984 and 1986, but with an emphasis on carbonaceous and sulfate components (Daisey et al., 1987; Miguel, 1991; Lopes and Andrade, 1996 and references therein). Since then, only the total suspended particulate matter, SO , NO (Feema, 1995 2 2 the Brazilian Environmental Council) and acetaldehyde (Grosjean et al., 1990) have been measured in Rio de Janeiro. Aliphatic hydrocarbons have not been analyzed before. Recently, some studies have been carried out in Sa8 o Paulo, where several classes of natural and anthropogenic organic compounds such as carboxylic acids (Souza and Carvalho, 1997), PAH and aliphatic hydrocarbons (Vasconcellos et al., 1998) have been identi"ed. Other studies were carried out in the Amazon Basin (Simoneit et al., 1990; Vasconcellos et al., 1998) and also simulation of the urban atmosphere chemistry polluted by alcohol fueled automobiles (Pimentel and Arbilla, 1997), as Brazil has unique vehicular emissions from ethanol and ethanol enriched fuels. With this in mind, the necessity to study the atmosphere in large cities is clear, especially in Brazil, where this kind of study is only a beginning. It is particularly important to evaluate pollution level and sources to provide more complete information on the chemical composition of the Rio de Janeiro aerosol. The present study reports the lipid compositions of extracts of aerosol particulate samples from four distinct sites of Rio de Janeiro polluted at di!erent levels: Cinela( ndia (downtown); Rebouc7 as Tunnel; Quinta da Boa Vista Park and Tijuca Forest.
pounds (ketones, alcohols) were visualized by exposure to iodine vapor in conjunction with the coelution of a standard compound mixture (lupene, acenaphthylene and perylene). The bands corresponding to these three fractions were scraped o! the TLC plate, eluted with methylene chloride, concentrated by rotary evaporation, nitrogen blowdown, and transferred to vials (Azevedo et al., 1994; Aquino Neto et al., 1992). The fractions were then subjected to high-resolution gas chromatographic (GC) and high-resolution gas chromatographic}mass spectrometric (CG}MS) analyses. The GC and GC}MS operating conditions were as follows: Hewlett-Packard 5890 gas chromatograph and HP5972 mass spectrometry detector, ionization 70 eV, 30 m]0.25 mm i.d. capillary column coated with DB-5; d "0.25 lm (J and W Scienti"c, Folsom, CA), temper& ature program 603C}3003C at 63C/min, held isothermal at 3003C for 20 min. Helium was used as the carrier gas for GC}MS and hydrogen for the GC analyses. Structural assignments were performed by comparison with authentic standards where possible or with the help of the Wiley 138 standard library. For components whose mass spectrum was unavailable, interpretations of mass spectrometric fragmentation patterns were used and relative GC retention times considered, especially in the case of homologous compound series. Quanti"cation was performed by GC using perdeuterated n-tetracosane (Cambridge Isotope Lab., Inc., Andover, MA, USA) and perylene (Supelco Inc., Bellefonte, USA) or pyrene (Cambridge Isotope Lab., Inc., Andover, MA, USA) as internal standards. A PAH standard solution (Hewlett-Packard) analysis by GC}MS was also utilized for the aromatic fractions.
3. Results and discussion 2. Experimental
3.1. Description of the area
Aerosol samples were collected from four urban sites (10 m inside Rebouc7 as Tunnel } RT; Tijuca Forest } TF; Quinta da Boa Vista Park } QBV; Cinela( ndia-downtown } CN) by "ltration of the ambient air through a high volume air sampler (`Hi-Vola) "tted with quartz "ber "lters (20]25 cm surface, Gelman Sciences Inc., Ann Arbor, MI) at a #ow rate of 1.5 m3/min. Filters were extracted using ultrasonic agitation for four 20-min periods with fresh 50 ml of methylene chloride: methanol (9 : 1-Omnisolv, Merck) each time. The "ltrate was "rst concentrated on a rotary evaporator followed by a stream of nitrogen gas to a reduced volume (Abas et al., 1995). The extracts were subjected to thin-layer chromatography (TLC) using silica-gel plates and eluted with hexane. The TLC elution regions corresponding to aliphatic and aromatic hydrocarbons and polar com-
The State of Rio de Janeiro is the second economic center of the country and highly urbanized. Of the metropolitan areas in Brazil, Rio de Janeiro is the most densely populated, with approximately 1700 inhabit/km2 (with about 11 million inhabitants distributed over a 6500 Km2), one of the largest urbanization degrees in the world (96.8%) (Feema, 1995). The urban atmosphere in Rio de Janeiro is in#uenced by several factors, such as the uneven topography, the irregular occupation of space, the presence of open sea and of the Guanabara Bay, factors that result in a complex regime for the winds and in resulting irregular distribution and dispersion of pollution. Vehicles, buses and oil boilers are the main sources of gaseous pollution. The main sources for the particulate emissions are linked to industrial sources. Sources of atmospheric pollutants include heavy motor vehicle
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tra$c, construction, resuspension of soil, stone masonry, various manufacturing activities (cement, glass, chemicals, etc.). Anhydrous ethyl alcohol produced from sugar cane is used as fuel and a gasoline fuel additive. The air quality in a place or area is dependent on a complex interaction between local factors, pollution sources and atmospheric conditions. Rio de Janeiro is a worst case example. Besides its varied urban characteristics, it presents an uneven topography, that creates natural microclimates, a!ecting, signi"cantly and in a diversi"ed way, the ventilation regime and, consequently, the transport mechanisms and dispersion of the pollution. Climatological evaluation of the wind patterns in Rio de Janeiro shows a larger frequency of occurrences of south-southeast to north-northwest winds in practically every month of the year, with average wind speeds of 8 Km/h. Therefore, considering the geographical position of Rio de Janeiro in relation to the predominant wind direction, the sea shore neighborhoods are swept by natural ventilation which tends to transport the pollution inland (north), where physical barriers, as for example mountains and high buildings, do not hinder the air #ow (Feema, 1995). Some characteristics of the sampling sites are shown in Table 1 and a partial map of Rio de Janeiro with sites location are presented in Fig. 1. 3.2. Aliphatic hydrocarbon fractions Gas chromatography and gas chromatography}mass spectrometry are extremely powerful tools for the characterization of complex environmental mixtures. One example of the utilization of GC and GC}MS in environmental research is the characterization of biogenic and
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petrogenic (derived from fossil fuels) organic matter in the atmosphere. Molecular marker analysis can be utilized for the purpose of source identi"cation. In this manner, comparisons are possible between known sources and the observed atmospheric organic carbon mixtures. Bulk parameters of the solvent}soluble extracts of organic aerosol that can be measured include: determination of carbon number maximum (Cmax) for the homologous compound series; carbon preference index (CPI) for the n-alkane series; unresolved to resolved (U : R) mass ratios. These bulk features can be obtained from gas chromatograms supplemented with minimal molecular con"rmation achieved using GC}MS analyses. It is possible to assign biogenic signatures to n-alkane homologue distribution exhibiting C *27; mixed bio.!9 genic and petrogenic signatures for C '23 and (26; .!9 and petrogenic signatures from n-alkanes homologue distribution with maxima (23. The determination of C for n-alkanes gives the strongest indication of an.!9 thropogenic versus natural recent biological input. Biologically synthesized n-alkanes show an oddto-even carbon number predominance. Hence, if the concentration ratio of odd-to-even numbered homologues is de"ned as the Carbon Preference Index (CPI), organic matter of recent biogenic origin will have CPI values of 6}9 and more. In general, CPI values greater than about 3 indicate that the n-alkanes observed are from predominantly biological materials, and that CPI values near unity signify the presence of n-alkanes derived from petroleum products or from partial thermal alteration (i.e., incomplete combustion) of petroleum or recent biological materials. Based on CPI data, the hydrocarbon (n-alkanes) fractions typically carry the
Table 1 Characteristics of the sampling sites Sample designation
Location
Elevation above Altitude ground (m) (m)
Date sampled
Site description
RT
Rebouc7 as Tunnel
2
Sea level
Jan/97
CN QBV
Cinela( ndia Quinta da Boa Vista Park
4 1
Sea level Sea level
Sep/97 Sep/97
TF
Tijuca Forest
1
&700
Jan/97
10 m inside a tunnel (2048 m longer; L2 galleryNorth-South) with heavy tra$c; 3.542 vehicles/h! Downtown, heavy tra$c; 3.193 vehicles/h! Zoo and park (560.500 m2) in the middle of the city, in one of the most polluted places of Rio de Janeiro. Surrounded by industry and tra$c of 1.595 vehicles/h! `Cascatinha Taunaya. A leisure place. National Park of Tijuca Forest is a great forest (5.650.525 m2) situated in the middle of the city but surrounded by truck and automotive tra$c of 844 vehicles/h!
!Monitored at the peak tra$c.
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Fig. 1. Urban regional map of Rio de Janeiro city showing major freeways, streets, airports, parks and the location of the air sampling sites. Numbers refer to: (1) Rebouc7 as Tunnel; (2) Cinela( ndia; (3) Quinta da Boa Vista Park; (4) Tijuca Forest. (Iplanrio, 1992).
greatest imprint of pollutants (Abas and Simoneit, 1997). Typical distributions for n-alkanes in Rio de Janeiro aerosols are shown in Figs. 2c and g and Fig. 3 and they range from about C }C . 15 37 The hydrocarbon fractions from Tijuca Forest and Quinta da Boa Vista Park consist predominantly of n-alkanes with homologues 'n-C , superimposed on 23 a background level of n-alkanes (nC }nC ) from crude 15 35 oil derivatives. These distributions show carbon number maxima (C ) at C /C which is characteristic of wax .!9 29 31 from plants (Simoneit and Mazurek, 1982; Simoneit et al., 1988,1991a,b). The CPI values for these two sites are 1.9 and 2.1, respectively, and are also indicative of a mixed input. It can be observed from Table 2 and Fig. 5, C for n-alkanes at C for RT, C for CN, C for .!9 24 23 29 QBV Park and TF (Table 3). Di!erent distributions of n-alkanes are observed in the Rebouc7 as Tunnel and Cinela( ndia samples analyzed. They are characteristic of petroleum-derived fuels, which can be veri"ed by the
distribution range (C }C ) and no carbon number pre15 35 dominance (CPI&1.0) (Fig. 5). In the industrialized modern world, there are many sources responsible for n-alkane release into the atmosphere. Anthropogenic sources typically include combustion of fossil fuels, wood and agricultural debris or leaves. Biogenic sources include particles shed from the epicuticular waxes of vascular plants and from direct suspension of pollen, microorganisms (e.g. bacteria, fungi and fungal spores) and insects. The relative distribution of n-alkanes between homologues of di!ering molecular weight, provides some insight into the likely sources that contribute to an ambient sample. Biosynthetic n-alkanes exhibit a strong odd carbon number predominance (e.g. C , C , C n-alkanes are more abundant in plant 29 31 33 waxes than the C , C and C homologues). The 28 30 32 n-alkane distribution found in plant waxes shows C and C as dominant homologues which often con29 31 tribute up to 90% of all para$ns found in them (Rogge et al., 1993a; Schauer et al., 1996).
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Fig. 2. Aliphatic hydrocarbon fraction of Rebouc7 as Tunnel sample: (A) total ion current; (B) mass fragmentogram (m/z 95) indicator for the naphthenes (i.e. UCM); (C) mass fragmentogram (m/z 85) characteristic of n-alkanes; (D) mass fragmentogram (m/z 191) for triterpanes (peaks are of the 17a(H), 21b(H)-hopane series); Aliphatic hydrocarbons fraction of Tijuca Forest sample: (E) total ion current; (F) mass fragmentogram (m/z 95) indicator for the naphthenes (i.e. UCM); (G) mass fragmentogram (m/z 85) characteristic of n-alkanes; (H) mass fragmentogram (m/z 191) for triterpanes. * Impurity.
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Fig. 3. Gas chromatogram of the aliphatic hydrocarbons from the: (IS"internal standard). (A) Cinela( ndia sample; (B) Quinta da Boa Vista Park sample.
The plant wax alkanes can be separated from the fossil component as follow: since it is known that n-alkanes of petroleum generally have a CPI of one, especially 'nC2 , we carried out a subtraction of the corresponding 4 n-alkane concentrations of CPI"1 as follows to determine the distribution signatures of the residual plant wax alkanes. The concentrations of the wax n-alkanes were calculated by subtraction of the average of the next higher and lower even numbered carbon homologues (Simoneit et al., 1991a,b): Wax C "[C ]![(C )#(C )]/2. n n n`1 n~1 Negative values of C were taken as zero. These results n are presented at Table 2 as petroleum residues and biogenic hydrocarbons. It can be seen that the summation of plant wax concentrations are almost the same for all samples, although percentages di!er signi"cantly. A greater percentage of biogenic hydrocarbons would be expected in FT than in QBV. The data, to the contrary, may be a result of wind directions that come from the Atlantic Ocean through Guanabara Bay, reaching QBV and then returning to the Tijuca site (Feema, 1995). Only
2.5% (RT) and 9.8% (CN) of biogenic hydrocarbons were observed. The concentrations of individual and average total n-alkanes in the RT and CN samples are comparable (same order of magnitude) to the ones observed in Barcelona (BC1, Rosell et al., 1991). Some results are better compared with data from another analysis also in Barcelona } BC2 (Aceves and Grimalt, 1992). These results are summarized in Table 4. The envelope of unresolved hydrocarbons (branched and cyclic } the `humpa or UCM"unresolved complex mixture) can be used as an approximate measure of the level of contamination by petroleum residues. Natural hydrocarbons derived from higher vascular plants exhibit no UCM. Auto exhaust exhibits a narrow UCM, maximizing at about C , which can also be plotted by 26 the m/z 95 mass fragmentogram, an ion typical in the mass spectra of naphthenic hydrocarbon mixtures. Gasoline does not contain unresolved hydrocarbons, but diesel fuels do show UCM in varying amounts and usually at a lower carbon number maximum (C ). UCM in 19 urban atmospheres come from lubricating oils of internal combustion engines with unburned fuels (Simoneit, 1984;
22.5}26 TF
26 27 CN QBV
!U : R"ratio of unresolved to resolved hydrocarbons. CPI"Carbon Preference Index: for n-alkanes it is expressed as a summation of the odd carbon number homologues over a range divided by a summation of the even carbon number homologues over the same range. "Wax C "[C ]![(C )#(C )]/2. n n n`1 n~1
2160 3.7 15.4;16 81.4;84 29 1.57 23 1.9 96.8 27
720 2160 67.6 4.9 23.3;9.8 14.7;25 213.8;90.2 43.7;75 23 29 1.05 1.96 26 29 4.4 2.1 237.1 58.3 348 227
270 85.9 14.3; 2.5 566.9;97.5 24 1.06 28 4.6 581.2 33.5
Rebouc7 as Tunnel Cinela( ndia Quinta da Boa Vista Park Tijuca Forest RT
332
Ambient temperature (3C) Location Sample designation
Table 2 Sample analytical results
Total particles (lg/m3)
Total aliphatic hydrocarbons (ng/m3)
U : R!
UCM C .!9
CPI (C }C ) 23 33
C .!9
Petroleum residues (ng/m3; %)
Biogenic Hydrocarbons" (ng/m3; %)
Total Aromatic Hydrocarbons (ng/m3)
Volume Sampled (m3)
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Simoneit and Mazurek, 1982; Simoneit et al., 1988; Rogge et al., 1993b). UCM (Fig. 2b for RT sample) observed for Rebouc7 as Tunnel (with maximum at C ), 28 Cinela( ndia (C ) and QBV Park (C ), indicate the pres26 28 ence of vehicular exhaust. A less-abundant UCM with a maximum at C is observed for Tijuca Forest, indica23 tive of minor contamination from vehicular emissions (Fig. 2f). This observation is not surprising as truck and automotive tra$c surrounds Tijuca Forest. Another diagnostic parameter that can be used to assess the magnitude of petroleum contributions to atmospheric aerosols is the ratio of the unresolved to the resolved hydrocarbon components (U : R). U : R values for rural, mixed and urban western United States samples, for example, are 0.2}4, 1.4}3.4 and 0.9}25, respectively. Generally, urban aerosols contain the largest ratio of petroleum-derived compounds. The hump: n-alkane ratios (U : R) are determined from the gas chromatogram by the area of unresolved material above the background (measured by planimetry or integration) divided by the sum of the GC area of resolved n-alkanes and other major components (Simoneit, 1984; Abas and Simoneit, 1997). The U : R values for the particulate samples from RT (4.6) and CN (4.4) imply that the major sources of nalkanes in these samples can be attributed to fossil fuel combustion. On the other hand, the U : R values for QBV (2.1) and TF (1.9) imply in a mixed origin for these n-alkanes. These values are comparable to the ones observed at Ibadan (4.3), Sokoto (4.0) and Maiduguri (3.9) in Nigeria, Africa (Simoneit et al., 1988) and also these at the Sugarpine Pt State Park (1.9), D and D Ranch (1.8) and Sierra Ski Ranch (2.0) in the United States (Simoneit, 1984). Molecular markers have been utilized as con"rmation indicators for petroleum residues, for higher plant wax and resin residues, and for pyrogenic components, which comprise the solvent}soluble organic matter of aerosols. Examples are the extended tricyclic terpanes, the 17a(H), 21b(H)-hopanes, the steranes and the isoprenoids, pristane and phytane. They con"rm an origin from petroleum, e.g., an unburned fuel component such as diesel. The identi"cation of these compounds is based primarily on their mass spectra and GC retention times. The hopanes occurrence is usually at low concentrations, but their overall distribution signatures within samples can be easily determined by CG}MS and utilized for comparison purposes. This is based on the m/z 191 ion intensity in the GC}MS data, which is the base peak of most of the triterpanes and the extended tricyclic terpanes. The presence of the hopane molecular markers con"rms an input source from fossil fuel utilization (i.e., vehicular tra$c) (Simoneit, 1984; Abas and Simoneit, 1997). The triterpane distribution patterns for the aerosol samples are shown in Figs. 2d, h, 4a and d. The 17H(a),
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Table 3 Aliphatic hydrocarbons identi"ed and quanti"ed in the particulate matter of the aerosol samples collected in four areas of Rio de Janeiro No
Compound
Diagnostic ion (m/z)
RT (ng/m3)
CN (ng/m3)
QBV (ng/m3)
TF (ng/m3)
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
n-Tetradecane n-Pentadecane n-Hexadecane n-Heptadecane Pristane n-Octadecane Phytane n-Nonadecane n-Eicosane n-Heneicosane n-Docosane n-Tricosane n-Tetracosane n-Pentacosane n-Hexacosane n-Heptacosane n-Octacosane n-Nonacosane n-Triacontane n-Hentriacontane n-Dotriacontane n-Tritriacontane n-Tetratriacontane n-Pentatriacontane n-Hexatriacontane n-Heptatriacontane 18a(H)-22,29,30-trisnorneohopane(Ts) 17a(H)!22,29,30-trisnorhopane (Tm) 17a(H),21b (H)-30-norhopane Triterpene 17a(H),21b(H)-hopane 17a(H),21b(H)-homohopane (22S) 17a(H),21b(H)-homohopane(22R) 17a(H),21b(H)-bishomohopane (22S) 17a(H),21b(H)-bishomohopane (22R) 17a(H),21b(H)-trishomohopane(22S) 17a(H),21b(H)-trishomohopane(22R) 17a(H),21b(H)-tetrahomohopane(22S) 17a(H),21b(H)-tetrahomohopane(22R) 17a(H),21b(H)-pentahomohopane(22S) 17a(H),21b(H)-pentahomohopane(22R) steranes C aaa 27 steranes C aaa 28 steranes C aaa 29 steranes C abb 27 steranes C abb 28 steranes C abb 29
85/198 85/212 85/226 85/240 183/268 85//254 183/282 85/268 85/282 85/296 85/310 85/324 85/338 85/352 85/366 85/380 85/394 85/408 85/422 85/436 85/450 85/464 85/478 85 85 85 191/370 191/370 191/398 191/410 191/412 191/426 191/426 191/440 191/440 191/454 191/454 191/468 191/468 191/482 191/482 217/372 217/386 217/400 218/372 218/386 218/400
0.89 0.61 0.98 1.6 1.01 3.05 2.48 8.10 23.17 30.02 57.15 70.35 72.92 72.13 69.67 38.73 13.30 20.63 9.5 10.09 3.08 2.51 4.34 1.93 1.14 # # 8.86 26.19 ! 14.42 6.75 4.77 0.39 0.44 n.a. n.a. n.a. n.a. n.a. n.a. tr tr tr tr tr tr
! # # # # # # # 6.67 6.98 17.21 26.56 22.54 25.43 13.93 23.45 19.09 24.52 14.91 18.70 6.80 5.81 2.89 1.13 0.52 # # # # ! # # # # # # # # # # # # # # # # #
! tr tr ! tr ! tr tr # 2.07 1.82 1.75 2.15 3.59 3.53 4.08 5.55 13.60 4.34 7.51 2.51 2.75 1.19 0.93 0.57 0.38 # # # ! # # # # # # # # # # # # # # # # #
0.13 0.98 2.35 2.04 0.81 1.56 1.49 1.5 3.69 5.3 7.1 6.58 13.99 5.54 2.38 3.13 2.65 15.10 2.98 4.44 2.24 2.62 1.79 1.53 1.01 # # ! # 3.88 # # # ! ! ! ! ! ! ! ! ! ! ! ! ! !
Note: *"RT, CN, QBV, TF, see Table 1.#"identi"ed. !"not identi"ed. tr"identi"ed in trace quantities. n.a."not analyzed. aaa"5a(H),14a(H),17a(H)-steranes. abb"5a(H),14b(H),17b(H)-steranes.
21H(b)-hopane series is present in CN, RT, and QBV samples ranging from C to C (typical of a petroleum 27 35 input to the aerosols; Simoneit, 1984), whereas for Tijuca
Forest they are present only at trace levels. Steranes and diasteranes are additional molecular markers commonly found in petroleum generally at a concentration lower
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Table 4 Comparison of selected hydrocarbon concentrations in Barcelona and Rio de Janeiro cities
n-tridecane n-heptadecane n-nonadecane Total aliphatic hydrocarbons PHE FLU PY B[ghi]P Total PAH
BC1! (ng/m3)
BC2" (ng/m3)
RT (ng/m3)
CN (ng/m3)
65 27 32 625 1.3 4.3 5.5 7.7 80
16 16 16 160 2.6 10 15 12 220
70 39 21 581 1.0 1.7 3.4 0.5 86
27 24 24 237 4.6 12 18 10 67
Note: PHE"phenanthrene; FLU"#uoranthene; PY"pyrene; B[ghi]P"benzo[ghi]perylene. !Rosell et al. (1991). "Aceves and Grimalt (1992).
Fig. 4. Aliphatic hydrocarbon fraction of the Cinela( ndia sample: (A) mass fragmentogram m/z 191, characteristic ion for terpanes (peaks are of the 17a(H), 21b(H)-hopane series); (B) mass fragmentogram (m/z 217) characteristic of aaa R/S steranes (aaa R/S"5a(H), 14a(H), 17a(H)-steranes, 20R or S); (C) mass fragmentogram (m/z 218) characteristic of abb R/S steranes (abb R/S"5a(H), 14b(H), 17b(H)steranes 20R or S). Aliphatic hydrocarbon fraction of the Quinta da Boa Vista Park sample: (D) mass fragmentogram m/z 191, characteristic ion for the terpanes (peaks are of the 17a(H), 21b(H)-hopane series): (E) mass fragmentogram (m/z 217) characteristic of aaa R/S steranes; (F) mass fragmentogram (m/z 218) characteristic of abb R/S steranes.
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than that of hopanes. These hydrocarbons are not present in contemporary biogenic materials and are found in engine lubricants but not in gasoline or diesel fuel. They are introduced into the atmosphere from vehicular emissions. Steranes are only present in aerosols at trace levels. The distribution signature in GC}MS data of, for example, the m/z 217 and m/z 218 ion peaks for steranes, are again useful supporting evidence for a petroleumderived input (Simoneit, 1984). Typical sterane fragmentograms are shown in Fig. 4b}e for aaa steranes and Fig. 4c}f for abb steranes. The Tijuca Forest sample did not contain detectable amounts of these compounds. The presence of hopanes and steranes in the hydrocarbon fractions of RT, CN and QBV con"rms an input source from fossil fuel utilization. They were introduced into the atmosphere from vehicular emissions (engine lubricants but not in gasoline or diesel fuels). These results are similar to the hopanes and steranes ambient concentrations measured in the Los Angeles atmosphere. Their presence were also attributed mainly to vehicular exhaust emissions, although fossil fuel markers can be emitted from other sources (Simoneit, 1984). All aliphatic hydrocarbons identi"ed and quanti"ed in the particulate matter of these aerosol samples are shown in Table 2, Table 3 and Fig. 5. Much higher total aliphatic hydrocarbons concentrations are obvious for
Rebouc7 as Tunnel and Cinela( ndia sites as compared to Quinta da Boa Vista Park and Tijuca Forest. The petroleum contamination is signi"cantly greater in these urban areas as can be seen from the petroleum residue and hump to normal ratio data in Table 2. The RT and CN sites exhibit high petroleum residues, but the plant wax components are not completely suppressed, as observed also in the Los Angeles air basin (Simoneit, 1984). Even a heavily contaminated aerosol has a slight predominance of C , C and C , the plant wax components. 25 27 29 To summarize, coupling C , CPI, in some cases U : R .!9 values, and molecular marker identi"cation allow the classi"cation of natural biogenic and anthropogenic components of atmospheric aerosols. The determination of C provides the strongest indication of contempor.!9 ary biogenic components in aerosols, mainly in the nalkanes serie. The CPI is a diagnostic parameter, where a high CPI ('3) indicates a major incorporation of recent biological constituents into the aerosol sample. The admixture of anthropogenic contaminants reduces the CPI such that values of about one re#ect the dominant input of anthropogenic fossil fuel compounds. Moreover, the hydrocarbon fractions typically carry the greatest imprint of pollutants. Molecular marker analysis provides supportive evidence for such assessments. Vehicular exhaust, for example, can be distinguished from
Fig. 5. n-Alkane concentration distributions for all the samples.
D. de Almeida Azevedo et al. / Atmospheric Environment 33 (1999) 4987}5001
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Table 5 Aromatic hydrocarbons identi"ed and quanti"ed in the particulate matter of the aerosol samples collected in four areas of Rio de Janeiro N3
Compound
Diagnostic ion (m/z)
RT (ng/m3)
CN (ng/m3)
QBV (ng/m3)
TF (ng/m3)
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
Acenaphthylene Acenaphthene 9H-#uorene Isopropyldimethylnaphthalene (cadalene) Phenanthrene Methylphenanthrenes Dimethylphenanthrenes Fluoranthene Pyrene Norsimonellite Benzo[ghi]#uoranthene Simonellite Retene Trimethylphenanthrenes Benz[a]anthracene Chrysene/triphenylene Benzo#uoranthenes (b#k) Benzo[e]pyrene Benzo[a]pyrene Indeno[7,1,2,3!cdef]chrysene Indeno[1,2,3!cd]pyrene Benzo[ghi]perylene Coronene Monoaromatic 8,4-secohopane C 29 Monoaromatic 8,4-secohopane C 30 Monoaromatic 8,4-secohopane C R 31 Monoaromatic 8,4-secohopane C S 31
152 154 166 183/198 178 192 206 202 202 223/238 226 237/252 219/234 220 228 228 252 252 252 276 276 276 300 365/394 365/408 365/422 365/422
4.29 2.20 ! 2.70 4.63
5.32 # 0.005 ! 1.00 tr # 1.65 3.39 tr ! tr # tr 2.01 10.71 15.46 # 10.67 2.24 4.69 9.98 # # # ! !
0.012 ! 0.0049 # 0.085 # # 0.15 0.18 # # # # # 0.073 0.754 1.54 ! 0.876 0.48 0.226 0.516 # tr tr ! !
0.065 ! ! # 0.21 # # 0.36 0.33 0.41 tr 0.59 0.42 tr # 0.03 0.31 ! 0.19 0.24 0.46 0.18 ! ! ! ! !
12.07 18.19 6.09 13.42 4.97 8.65 # 2.11 2.43 ! ! 0.58 ! ! 0.49 ! 2.42 0.65 # #
Note: *"RT, CN, QBV, TF, see Table 1. #"identi"ed. !"not identi"ed. tr"identi"ed in trace quantities.
natural background (plant wax and resin residues) by the presence of petroleum tracers such as steranes and hopanes (Abas and Simoneit, 1997). The basic results are clear; vehicular tra$c with the associated fuels and lubricants emit petroleum residues comprised of n-alkanes with no carbon number predominance, unresolvable hydrocarbons components (hump) and molecular indicators to the ambient atmosphere. From our data, it can be observed that RT and CN have a dominant contribution of n-alkanes from petroleum (97.5% and 90.2%, respectively) and QBV Park and TF have a signi"cant contribution from vascular plant wax (25% and 16%, respectively). 3.3. Aromatic hydrocarbon fractions The usual series of polycyclic aromatic hydrocarbons (PAH), consisting of phenanthrene, #uoranthene, pyrene,
benzanthracene, benzo#uoranthenes, benzopyrenes and indenopyrenes are present in the four samples, but in the Tijuca Forest sample they are observed only at trace levels (Table 5). The composite fragmentograms from selected PAH in RT and CN are illustrated in Fig. 6 and summarized in Fig. 7. The concentrations of some individual and total average PAH in the RT and CN samples are comparable to the ones observed in Barcelona city } BC1 (Rosell et al., 1991). Some results are better compared with data from another analysis also in Barcelona } BC2, Table 4 (Aceves and Grimalt, 1992). In order to assess the di!erent sources and origins of PAH present in the aerosols, a comparison can be made between characteristic ratios calculated and measured for the present aerosols. The comparison of the values listed in Table 6 with those associated with the PAH pro"les sampled in the
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Fig. 6. Composite fragmentograms (sum of molecular or fragment ion intensities of the dominant PAH) for the aromatic fractions in the aerosols. For numbers, see Table 5: (A) CN; (C) RT (m/z 152, 178, 183, 192, 206, 202); (B) CN; (D) RT (m/z 226, 228, 252, 276, 300, 365).
D. de Almeida Azevedo et al. / Atmospheric Environment 33 (1999) 4987}5001
city areas con"rms their usefulness for the di!erentiation of the sources discussed above. From the comparison of Tables 6 and 7 it can be concluded, once more, that the main source contributing to the aerosol PAH mixture is vehicle emissions (car emissions and used motor or lubricating oils). Values of the ratio #uoranthene/pyrene are close to those observed in used motor oil and car emission in all sites. In addition, the ratio Bz(a)an/ (Bz(a)an#Chr#Try) to RT con"rms the contribution of lubricating oil. A decrease in the abundance of some PAH such as phenanthrene, #uoranthene and pyrene (Fig. 7) can be observed from RT'CN'QBV'TF. This trend is true for the total aromatic hydrocarbons (Table 5) and also for the total suspended particulate matter (TSP, Table 2). The TSP shows elevated levels for samples CN}RT}QBV ('227 lg/m3) as compared with the WHO (World Health Organization) regulation limits (150}230 lg/m3) and also the Brazilian Regulation limits (Resolution Conama no. 03; Feema, 1995). Only TF shows a low TSP value (27 lg/m3). The concentrations of TSP measured during this study were a little higher in
4999
comparison to the range of concentrations reported previously for Rio de Janeiro (Feema, 1995), unless for TF. A series of monoaromatic 8,4-secohopanes (C }C ) 29 31 was also observed for the three more polluted sites, although for QBV Park only at trace levels. As often found for D-ring monoaromatic 8,14- secohopanoids in crude oils, the C and C components were dominant in the 29 30 samples analyzed, although traces of the C isomeric 31 pair were also detected (see Fig. 6d, components 71}73). The C compound was a dominant peak in the aromatic 29 fraction of the sample from Rebouc7 as Tunnel. The presence of these compounds was con"rmed by their mass spectra and the m/z 365 key ion. They have been reported in crude oils from South Texas and various oil shales (Killops, 1991). These compounds found in the TSP of aerosol samples would originate from petroleum fuel used in vehicles and are characteristic of petroleum used in Brazil. The presence of secohopanoids in the aerosol particulate matter con"rms emissions from vehicles using petroleum products containing these biomarkers.
4. Conclusions It could be veri"ed that almost the same level of pollution exists in RT and CN. This observation was based on Table 2, all the data analysis and also the presence of hopanes and steranes. The QBV site, despite being located in a polluted district, presents an intermediate level of pollution as evidenced by the smaller U : R, CPI, and total PAH and n-alkanes. Furthermore, presents the greatest biogenic hydrocarbons percentage (25%). The TF sample shows smaller U : R, a greater percentage of n-alkanes from plant wax, the hopane series only in trace quantities, no steranes and PAH at
Table 7 Ratios derived from the PAH composition of the aerosols collected in Rio de Janeiro
Fig. 7. Selected PAH concentration distributions. (ACY" acenaphthylene; PHE"phenanthrene; FLT"#uoranthene; PY"pyrene; CHR"chrysene; BaP"benzo[a]pyrene; BghiP" benzo[ghi]perylene).
Fl/(Fl#Py) Bz(a)an/(Bz(a)an#Chr#Try)
RT
CN
QBV
TF
0.40 0.47
0.34 0.15
0.45 *
0.52 *
Table 6 Characteristic ratios from the PAH composition of some potential source inputs to urban atmosphere (Sicre et al., 1987)
Fl/(Fl#Py) Bz(a)an/(Bz(a)an#Chr#Try)
Crude oil
Used motor oil
Car emissions (gasoline)
Wood soot
0.18$0.06 0.16$0.12
0.36$0.08 0.5
0.43$0.08 *
* 0.40$0.09
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D. de Almeida Azevedo et al. / Atmospheric Environment 33 (1999) 4987}5001
trace levels. It was observed that RT, CN and QBV Park are polluted by emissions from incomplete combustion of petroleum fuels as con"rmed by the biomarker patterns (hopanes, steranes, n-alkanes). For RT and CN, a higher U : R and CPI&1.0 was also observed. The emissions originate from the heavy tra$c. The Tijuca Forest site presented low pollution levels, despite the fact that it is surrounded by the city. This can be attributed to the dilution e!ect of a large area (5.650.525 m2) devoid of pollution sources, cleaning (sink) e!ect of the luxurious vegetation and the wind regimes of the site. We suggest that there is a decrease in the degree of pollution in the order RT'CN'QBV'TF, as expected from the traf"c density (3542, 3192, 1595, 844 vehicles/hour in the surrounding area, respectively). Unfortunately all the sites are polluted, with the lowest level in Tijuca forest.
Acknowledgements We would like to thank CNPq, FUJB, FAPERJ for "nancial support, CET-RIO for tra$c data and the reviewers, especially Dr. B.R.T. Simoneit, for all the comments and suggestions.
References Abas, M.R.B., Simoneit, B.R.T., Elias, V., Cabral, J.A., Cardoso, J.N., 1995. Composition of higher molecular weight organic matter in smoke aerosol from biomass combustion in amazonia. Chemosphere 30 (5), 995}1015. Abas, M.R.B., Simoneit, B.R.T., 1997. Gas chromatographic and gas chromatographic-mass spectrometric characterization of biogenic and petrogenic organic matter in the atmosphere. Malaysian Journal of Analytical Science 3 (1), 9}23. Aceves, M., Grimalt, J.O., 1992. Gas chromatographic screening of organic compounds in urban aerosols. Selectivity e!ects in semi-polar columns. Journal of Chromatography 607, 261}270. Aquino Neto, F.R., Triguis, J., Azevedo, D.A., Rodrigues, R., Simoneit, B.R.T., 1992. Organic geochemistry of geographically unrelated tasmanites. Organic Geochemistry 18 (6), 791}803. Azevedo, D.A., Aquino Neto, F.R., Simoneit, B.R.T., 1994. Extended saturated and monoaromatic tricyclic terpenoid carboxylic acids found in Tasmanian tasmanite. Organic Geochemistry 22 (6), 991}1004. Daisey, J.M., Miguel, A.H., Andrade, J.B., Pereira, P.A.P., Tanner, R.L., 1987. An overview of the Rio de Janeiro aerosol characterization study. Journal of Air Pollution Control Association 37 (1), 15}23. Feema, 1995. Qualidade do Ar na Regia8 o Metropolitana do Rio de Janeiro, 76p. Grosjean, D., Miguel, A.H., Tavares, T.M., 1990. Urban air pollution in Brazil: acetaldehyde and other carbonyls. Atmospheric Environment 24B (1), 101}106.
Hannigan, M.P., Cass, G.R., La#eur, A.L., Longwell, J.P., Thilly, W.G., 1994. Bacterial mutagenicity of urban organic aerosol sources in comparison to atmospheric samples. Environmental Science Technology 28 (12), 2014}2024. Hannigan, M.P., Cass, G.R., Penman, B.W., Crespi, C.L., La#eur, A.L., Busby Jr., W.F., Thilly, W.G. Simoneit, B.R.T., 1998. Bioassay-directed chemical analysis of Los Angeles airborne particulate matter using a human cell mutagenicity assay. Environmental Science Technology 32 (22); 3502}3514. Iplanrio, 1992. AnuaH rio EstatmH stico da Cidade do Rio de Janeiro, 1991. IPLANRIO, Rio de Janeiro, 312p. Killops, S.D., 1991. Novel aromatic hydrocarbons of probable bacterial origin in a Jurassic lacustrine sequence. Organic Geochemistry 17 (1), 25}36. Lopes, W.A., Andrade, J.B., 1996. Fontes, formac7 a8 o, reatividade e quanti"cac7 a8 o de hidrocarbonetos policmH clicos aromaH ticos (HPA) na atmosfera. Quimica Nova 19 (5), 497}516. Miguel, A.H., 1991. Environmental pollution research in South America. Environmental Science Technology 25 (40), 590}594. Pimentel, A.S., Arbilla, G., 1997. Simulac7 a8 o da qumH mica da atmosfera polumH da por automoH veis movidos a aH lcool. Quimica Nova 20 (3), 245}251. Rogge, W.F., Mazurek, M.A., Hildemann, L.M., Cass, G.R., Simoneit, B.R.T., 1993a. Quanti"cation of urban organic aerosols at a molecular level: identi"cation, abundance and seasonal variation. Atmospheric Environment 27A (8), 1309}1330. Rogge, W.F., Mazurek, M.A., Hildemann, L.M., Cass, G.R., Simoneit, B.R.T., 1993b. Sources of "ne organic aerosol. 2. Noncatalyst and catalyst-equipped automobiles and heavyduty diesel trucks. Environmental Science Technology 27 (4), 636}651. Rosell, A., Grimalt, J.O., Rosell, M.G., Guardino, X., AlbaigeH s, J., 1991. Biomonitoring of environmental hydrocarbons. The composition of volatile and particulate hydrocarbons in urban air. Fresenius Journal of Analytical Chemistry 339, 689}698. Schauer, J.J., Rogge, W.F., Hildemann, L.M., Mazurek, M.A., Cass, G.R., Simoneit, B.R.T., 1996. Source apportionment of airborne particulate matter using organic compounds as tracers. Atmospheric Environment 30 (22), 3837}3855. Sicre, M.A., Marty, J.C., Saliot, S., Aparicio, X., Grimalt, J., Albaiges, J., 1987. Aliphatic and aromatic hydrocarbons in di!erent sized aerosols over the mediterranean sea: occurrence and origin. Atmospheric Environment 21 (10), 2247}2259. Simoneit, B.R.T., 1984. Organic matter of the troposphere } III. Characterization and sources of petroleum and pyrogenic residues in aerosols over the western United States. Atmospheric Environment 18 (1), 51}67. Simoneit, B.R.T., Mazurek, M., 1982. Organic matter of the troposphere } II. Natural background of biogenic lipid matter in aerosols over the rural western United States. Atmospheric Environment 16 (9), 2139}2159. Simoneit, B.R.T., Cox, R.E., Standley, L.J., 1988. Organic matter of the troposphere } IV. Lipids in Harmattan aerosols of Nigeria. Atmospheric Environment 22 (5), 983}1004. Simoneit, B.R.T., Cardoso, J.N., Robinson, N., 1990. An assessment of the origin and composition of higher molecular
D. de Almeida Azevedo et al. / Atmospheric Environment 33 (1999) 4987}5001 weight organic matter in aerosols Amazonia. Chemosphere 21, 1285}1301. Simoneit, B.R.T., Sheng, G., Chen, X., Fu, J., Zhang, J., Xu, Y., 1991a. Molecular marker study of extractable organic matter in aerosols from urban areas of China. Atmospheric Environment 25A (10), 2111}2129. Simoneit, B.R.T., Crisp, P.T., Mazurek, M.A., Standley, L.J., 1991b. Composition of extractable organic matter of aerosols from the blue mountains and southeast coast of Australia. Environmental International 17, 405}419.
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Souza, S.R., Carvalho, L.R.F., 1997. Determinac7 a8 o de aH cidos carboxmH licos na atmosfera urbana de Sa8 o Paulo. Uma abordagem analmH tica e ambiental. Quimica Nova 20 (3), 238}244. Vasconcellos, P.C., Artaxo, P.E., Ciccioli, P., Cicinato, A., Brancaleoni, E., Frattoni, M., 1998. Determinac7 a8 o dos hidrocarbonetos saturados e policmH clicos aromaH ticos presentes no material particulado da atmosfera amazo( nica. Quimica Nova 21 (4), 385}393.
Composition of extractable organic matter in aerosols from urban areas of Rio de Janeiro city, Brazil DeH bora de Almeida Azevedo*, Larissa Silveira Moreira, Denilson Soares de Siqueira Instituto de Qun& mica, Universidade Federal do Rio de Janeiro, Centro de Tecnologia, Bl. A, Sala 607, Ilha do FundaJ o, Rio de Janeiro, Brazil Received 19 October 1998; accepted 11 May 1999
Abstract The hydrocarbon compositions of atmospheric particulate matter from urban areas of Rio de Janeiro city have been studied to assess the di!erent pollution levels. Samples were acquired using a standard high-volume air sampler (Hi-Vol), extracts were prepared and fractionated into aliphatic and aromatic compounds. High-resolution gas chromatography and GC coupled to mass spectrometry (GC}MS) were used for the analysis of the organic matter. The results show that all samples contain n-alkanes, but the distributions are di!erent for each sample, re#ecting both the biogenic (vascular plant wax input) and fossil fuel contamination sources (vehicular exhaust). The fossil fuel biomarkers, hopanes and steranes, were also observed in all samples except in the Tijuca Forest, which is a mountain forest in the midst of the sea-level city. A decrease in the level of pollution was observed in the sequence for Rebouc7 as Tunnel'Cinela( ndia (downtown)'Quinta da Boa Vista Park'Tijuca Forest, as expected from the tra$c density. Unfortunately, all sites are polluted mainly from vehicular emissions, but at di!erent degrees, with the lowest levels in Tijuca Forest. ( 1999 Elsevier Science Ltd. All rights reserved. Keywords: Urban air pollution; PAH; Hydrocarbons; Air quality; Particulate matter
1. Introduction The transport of pollutants through the atmosphere often gives rise to the direct uncontrolled exposure of large populations to toxic substances. This is especially relevant in urban areas where the levels of several pollutants is higher and the proximity between humans and pollutant sources is closest. Thus, a direct cause}e!ect relationship between the atmospheric release of allergenic products and urban asthma outbreaks, has been documented. In addition, many organic compounds, i.e. polyaromatic hydrocarbons (PAH), found in urban air, have been proved to be mutagens or carcinogens. It has been demonstrated, for example that mutagens a!ecting
* Corresponding author. E-mail address: [email protected] (D. de Almeida Azevedo)
S. typhimurium are present in particle samples from urban combustion sources, including catalyst-equipped auto exhaust, non-catalyst auto exhaust, diesel truck exhaust, wood smoke, distillate fuel oil combustion aerosol, and natural gas combustion aerosol (Hannigan et al., 1994). The subfractions that contain unsubstituted PAH are responsible for a considerable portion of the mutagenic potency of the whole atmospheric sample (Hannigan et al., 1998). Hydrocarbons are widespread components, which belong to the carbon cycle of the environment. Natural aliphatic and aromatic hydrocarbons (HCs) produced by continental and marine plants, are generally encountered at trace levels, with characteristic components or distributions re#ecting their origin. Anthropogenic HCs are widely distributed, originating from petroleum products and from the combustion of fuels, like crude or re"ned petroleum derivatives, coal, wood, etc. Thus, the source of anthropogenic HCs is mostly over the industrialized
1352-2310/99/$ - see front matter ( 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 2 7 0 - 8
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regions of continents, associated with industrial and urban activities (Rogge et al., 1993a,b; Schauer et al., 1996). Detailed studies of the atmospheric levels of PAHs and of total suspended particulate matter have been investigated in Rio de Janeiro in 1984 and 1986, but with an emphasis on carbonaceous and sulfate components (Daisey et al., 1987; Miguel, 1991; Lopes and Andrade, 1996 and references therein). Since then, only the total suspended particulate matter, SO , NO (Feema, 1995 2 2 the Brazilian Environmental Council) and acetaldehyde (Grosjean et al., 1990) have been measured in Rio de Janeiro. Aliphatic hydrocarbons have not been analyzed before. Recently, some studies have been carried out in Sa8 o Paulo, where several classes of natural and anthropogenic organic compounds such as carboxylic acids (Souza and Carvalho, 1997), PAH and aliphatic hydrocarbons (Vasconcellos et al., 1998) have been identi"ed. Other studies were carried out in the Amazon Basin (Simoneit et al., 1990; Vasconcellos et al., 1998) and also simulation of the urban atmosphere chemistry polluted by alcohol fueled automobiles (Pimentel and Arbilla, 1997), as Brazil has unique vehicular emissions from ethanol and ethanol enriched fuels. With this in mind, the necessity to study the atmosphere in large cities is clear, especially in Brazil, where this kind of study is only a beginning. It is particularly important to evaluate pollution level and sources to provide more complete information on the chemical composition of the Rio de Janeiro aerosol. The present study reports the lipid compositions of extracts of aerosol particulate samples from four distinct sites of Rio de Janeiro polluted at di!erent levels: Cinela( ndia (downtown); Rebouc7 as Tunnel; Quinta da Boa Vista Park and Tijuca Forest.
pounds (ketones, alcohols) were visualized by exposure to iodine vapor in conjunction with the coelution of a standard compound mixture (lupene, acenaphthylene and perylene). The bands corresponding to these three fractions were scraped o! the TLC plate, eluted with methylene chloride, concentrated by rotary evaporation, nitrogen blowdown, and transferred to vials (Azevedo et al., 1994; Aquino Neto et al., 1992). The fractions were then subjected to high-resolution gas chromatographic (GC) and high-resolution gas chromatographic}mass spectrometric (CG}MS) analyses. The GC and GC}MS operating conditions were as follows: Hewlett-Packard 5890 gas chromatograph and HP5972 mass spectrometry detector, ionization 70 eV, 30 m]0.25 mm i.d. capillary column coated with DB-5; d "0.25 lm (J and W Scienti"c, Folsom, CA), temper& ature program 603C}3003C at 63C/min, held isothermal at 3003C for 20 min. Helium was used as the carrier gas for GC}MS and hydrogen for the GC analyses. Structural assignments were performed by comparison with authentic standards where possible or with the help of the Wiley 138 standard library. For components whose mass spectrum was unavailable, interpretations of mass spectrometric fragmentation patterns were used and relative GC retention times considered, especially in the case of homologous compound series. Quanti"cation was performed by GC using perdeuterated n-tetracosane (Cambridge Isotope Lab., Inc., Andover, MA, USA) and perylene (Supelco Inc., Bellefonte, USA) or pyrene (Cambridge Isotope Lab., Inc., Andover, MA, USA) as internal standards. A PAH standard solution (Hewlett-Packard) analysis by GC}MS was also utilized for the aromatic fractions.
3. Results and discussion 2. Experimental
3.1. Description of the area
Aerosol samples were collected from four urban sites (10 m inside Rebouc7 as Tunnel } RT; Tijuca Forest } TF; Quinta da Boa Vista Park } QBV; Cinela( ndia-downtown } CN) by "ltration of the ambient air through a high volume air sampler (`Hi-Vola) "tted with quartz "ber "lters (20]25 cm surface, Gelman Sciences Inc., Ann Arbor, MI) at a #ow rate of 1.5 m3/min. Filters were extracted using ultrasonic agitation for four 20-min periods with fresh 50 ml of methylene chloride: methanol (9 : 1-Omnisolv, Merck) each time. The "ltrate was "rst concentrated on a rotary evaporator followed by a stream of nitrogen gas to a reduced volume (Abas et al., 1995). The extracts were subjected to thin-layer chromatography (TLC) using silica-gel plates and eluted with hexane. The TLC elution regions corresponding to aliphatic and aromatic hydrocarbons and polar com-
The State of Rio de Janeiro is the second economic center of the country and highly urbanized. Of the metropolitan areas in Brazil, Rio de Janeiro is the most densely populated, with approximately 1700 inhabit/km2 (with about 11 million inhabitants distributed over a 6500 Km2), one of the largest urbanization degrees in the world (96.8%) (Feema, 1995). The urban atmosphere in Rio de Janeiro is in#uenced by several factors, such as the uneven topography, the irregular occupation of space, the presence of open sea and of the Guanabara Bay, factors that result in a complex regime for the winds and in resulting irregular distribution and dispersion of pollution. Vehicles, buses and oil boilers are the main sources of gaseous pollution. The main sources for the particulate emissions are linked to industrial sources. Sources of atmospheric pollutants include heavy motor vehicle
D. de Almeida Azevedo et al. / Atmospheric Environment 33 (1999) 4987}5001
tra$c, construction, resuspension of soil, stone masonry, various manufacturing activities (cement, glass, chemicals, etc.). Anhydrous ethyl alcohol produced from sugar cane is used as fuel and a gasoline fuel additive. The air quality in a place or area is dependent on a complex interaction between local factors, pollution sources and atmospheric conditions. Rio de Janeiro is a worst case example. Besides its varied urban characteristics, it presents an uneven topography, that creates natural microclimates, a!ecting, signi"cantly and in a diversi"ed way, the ventilation regime and, consequently, the transport mechanisms and dispersion of the pollution. Climatological evaluation of the wind patterns in Rio de Janeiro shows a larger frequency of occurrences of south-southeast to north-northwest winds in practically every month of the year, with average wind speeds of 8 Km/h. Therefore, considering the geographical position of Rio de Janeiro in relation to the predominant wind direction, the sea shore neighborhoods are swept by natural ventilation which tends to transport the pollution inland (north), where physical barriers, as for example mountains and high buildings, do not hinder the air #ow (Feema, 1995). Some characteristics of the sampling sites are shown in Table 1 and a partial map of Rio de Janeiro with sites location are presented in Fig. 1. 3.2. Aliphatic hydrocarbon fractions Gas chromatography and gas chromatography}mass spectrometry are extremely powerful tools for the characterization of complex environmental mixtures. One example of the utilization of GC and GC}MS in environmental research is the characterization of biogenic and
4989
petrogenic (derived from fossil fuels) organic matter in the atmosphere. Molecular marker analysis can be utilized for the purpose of source identi"cation. In this manner, comparisons are possible between known sources and the observed atmospheric organic carbon mixtures. Bulk parameters of the solvent}soluble extracts of organic aerosol that can be measured include: determination of carbon number maximum (Cmax) for the homologous compound series; carbon preference index (CPI) for the n-alkane series; unresolved to resolved (U : R) mass ratios. These bulk features can be obtained from gas chromatograms supplemented with minimal molecular con"rmation achieved using GC}MS analyses. It is possible to assign biogenic signatures to n-alkane homologue distribution exhibiting C *27; mixed bio.!9 genic and petrogenic signatures for C '23 and (26; .!9 and petrogenic signatures from n-alkanes homologue distribution with maxima (23. The determination of C for n-alkanes gives the strongest indication of an.!9 thropogenic versus natural recent biological input. Biologically synthesized n-alkanes show an oddto-even carbon number predominance. Hence, if the concentration ratio of odd-to-even numbered homologues is de"ned as the Carbon Preference Index (CPI), organic matter of recent biogenic origin will have CPI values of 6}9 and more. In general, CPI values greater than about 3 indicate that the n-alkanes observed are from predominantly biological materials, and that CPI values near unity signify the presence of n-alkanes derived from petroleum products or from partial thermal alteration (i.e., incomplete combustion) of petroleum or recent biological materials. Based on CPI data, the hydrocarbon (n-alkanes) fractions typically carry the
Table 1 Characteristics of the sampling sites Sample designation
Location
Elevation above Altitude ground (m) (m)
Date sampled
Site description
RT
Rebouc7 as Tunnel
2
Sea level
Jan/97
CN QBV
Cinela( ndia Quinta da Boa Vista Park
4 1
Sea level Sea level
Sep/97 Sep/97
TF
Tijuca Forest
1
&700
Jan/97
10 m inside a tunnel (2048 m longer; L2 galleryNorth-South) with heavy tra$c; 3.542 vehicles/h! Downtown, heavy tra$c; 3.193 vehicles/h! Zoo and park (560.500 m2) in the middle of the city, in one of the most polluted places of Rio de Janeiro. Surrounded by industry and tra$c of 1.595 vehicles/h! `Cascatinha Taunaya. A leisure place. National Park of Tijuca Forest is a great forest (5.650.525 m2) situated in the middle of the city but surrounded by truck and automotive tra$c of 844 vehicles/h!
!Monitored at the peak tra$c.
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Fig. 1. Urban regional map of Rio de Janeiro city showing major freeways, streets, airports, parks and the location of the air sampling sites. Numbers refer to: (1) Rebouc7 as Tunnel; (2) Cinela( ndia; (3) Quinta da Boa Vista Park; (4) Tijuca Forest. (Iplanrio, 1992).
greatest imprint of pollutants (Abas and Simoneit, 1997). Typical distributions for n-alkanes in Rio de Janeiro aerosols are shown in Figs. 2c and g and Fig. 3 and they range from about C }C . 15 37 The hydrocarbon fractions from Tijuca Forest and Quinta da Boa Vista Park consist predominantly of n-alkanes with homologues 'n-C , superimposed on 23 a background level of n-alkanes (nC }nC ) from crude 15 35 oil derivatives. These distributions show carbon number maxima (C ) at C /C which is characteristic of wax .!9 29 31 from plants (Simoneit and Mazurek, 1982; Simoneit et al., 1988,1991a,b). The CPI values for these two sites are 1.9 and 2.1, respectively, and are also indicative of a mixed input. It can be observed from Table 2 and Fig. 5, C for n-alkanes at C for RT, C for CN, C for .!9 24 23 29 QBV Park and TF (Table 3). Di!erent distributions of n-alkanes are observed in the Rebouc7 as Tunnel and Cinela( ndia samples analyzed. They are characteristic of petroleum-derived fuels, which can be veri"ed by the
distribution range (C }C ) and no carbon number pre15 35 dominance (CPI&1.0) (Fig. 5). In the industrialized modern world, there are many sources responsible for n-alkane release into the atmosphere. Anthropogenic sources typically include combustion of fossil fuels, wood and agricultural debris or leaves. Biogenic sources include particles shed from the epicuticular waxes of vascular plants and from direct suspension of pollen, microorganisms (e.g. bacteria, fungi and fungal spores) and insects. The relative distribution of n-alkanes between homologues of di!ering molecular weight, provides some insight into the likely sources that contribute to an ambient sample. Biosynthetic n-alkanes exhibit a strong odd carbon number predominance (e.g. C , C , C n-alkanes are more abundant in plant 29 31 33 waxes than the C , C and C homologues). The 28 30 32 n-alkane distribution found in plant waxes shows C and C as dominant homologues which often con29 31 tribute up to 90% of all para$ns found in them (Rogge et al., 1993a; Schauer et al., 1996).
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Fig. 2. Aliphatic hydrocarbon fraction of Rebouc7 as Tunnel sample: (A) total ion current; (B) mass fragmentogram (m/z 95) indicator for the naphthenes (i.e. UCM); (C) mass fragmentogram (m/z 85) characteristic of n-alkanes; (D) mass fragmentogram (m/z 191) for triterpanes (peaks are of the 17a(H), 21b(H)-hopane series); Aliphatic hydrocarbons fraction of Tijuca Forest sample: (E) total ion current; (F) mass fragmentogram (m/z 95) indicator for the naphthenes (i.e. UCM); (G) mass fragmentogram (m/z 85) characteristic of n-alkanes; (H) mass fragmentogram (m/z 191) for triterpanes. * Impurity.
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Fig. 3. Gas chromatogram of the aliphatic hydrocarbons from the: (IS"internal standard). (A) Cinela( ndia sample; (B) Quinta da Boa Vista Park sample.
The plant wax alkanes can be separated from the fossil component as follow: since it is known that n-alkanes of petroleum generally have a CPI of one, especially 'nC2 , we carried out a subtraction of the corresponding 4 n-alkane concentrations of CPI"1 as follows to determine the distribution signatures of the residual plant wax alkanes. The concentrations of the wax n-alkanes were calculated by subtraction of the average of the next higher and lower even numbered carbon homologues (Simoneit et al., 1991a,b): Wax C "[C ]![(C )#(C )]/2. n n n`1 n~1 Negative values of C were taken as zero. These results n are presented at Table 2 as petroleum residues and biogenic hydrocarbons. It can be seen that the summation of plant wax concentrations are almost the same for all samples, although percentages di!er signi"cantly. A greater percentage of biogenic hydrocarbons would be expected in FT than in QBV. The data, to the contrary, may be a result of wind directions that come from the Atlantic Ocean through Guanabara Bay, reaching QBV and then returning to the Tijuca site (Feema, 1995). Only
2.5% (RT) and 9.8% (CN) of biogenic hydrocarbons were observed. The concentrations of individual and average total n-alkanes in the RT and CN samples are comparable (same order of magnitude) to the ones observed in Barcelona (BC1, Rosell et al., 1991). Some results are better compared with data from another analysis also in Barcelona } BC2 (Aceves and Grimalt, 1992). These results are summarized in Table 4. The envelope of unresolved hydrocarbons (branched and cyclic } the `humpa or UCM"unresolved complex mixture) can be used as an approximate measure of the level of contamination by petroleum residues. Natural hydrocarbons derived from higher vascular plants exhibit no UCM. Auto exhaust exhibits a narrow UCM, maximizing at about C , which can also be plotted by 26 the m/z 95 mass fragmentogram, an ion typical in the mass spectra of naphthenic hydrocarbon mixtures. Gasoline does not contain unresolved hydrocarbons, but diesel fuels do show UCM in varying amounts and usually at a lower carbon number maximum (C ). UCM in 19 urban atmospheres come from lubricating oils of internal combustion engines with unburned fuels (Simoneit, 1984;
22.5}26 TF
26 27 CN QBV
!U : R"ratio of unresolved to resolved hydrocarbons. CPI"Carbon Preference Index: for n-alkanes it is expressed as a summation of the odd carbon number homologues over a range divided by a summation of the even carbon number homologues over the same range. "Wax C "[C ]![(C )#(C )]/2. n n n`1 n~1
2160 3.7 15.4;16 81.4;84 29 1.57 23 1.9 96.8 27
720 2160 67.6 4.9 23.3;9.8 14.7;25 213.8;90.2 43.7;75 23 29 1.05 1.96 26 29 4.4 2.1 237.1 58.3 348 227
270 85.9 14.3; 2.5 566.9;97.5 24 1.06 28 4.6 581.2 33.5
Rebouc7 as Tunnel Cinela( ndia Quinta da Boa Vista Park Tijuca Forest RT
332
Ambient temperature (3C) Location Sample designation
Table 2 Sample analytical results
Total particles (lg/m3)
Total aliphatic hydrocarbons (ng/m3)
U : R!
UCM C .!9
CPI (C }C ) 23 33
C .!9
Petroleum residues (ng/m3; %)
Biogenic Hydrocarbons" (ng/m3; %)
Total Aromatic Hydrocarbons (ng/m3)
Volume Sampled (m3)
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Simoneit and Mazurek, 1982; Simoneit et al., 1988; Rogge et al., 1993b). UCM (Fig. 2b for RT sample) observed for Rebouc7 as Tunnel (with maximum at C ), 28 Cinela( ndia (C ) and QBV Park (C ), indicate the pres26 28 ence of vehicular exhaust. A less-abundant UCM with a maximum at C is observed for Tijuca Forest, indica23 tive of minor contamination from vehicular emissions (Fig. 2f). This observation is not surprising as truck and automotive tra$c surrounds Tijuca Forest. Another diagnostic parameter that can be used to assess the magnitude of petroleum contributions to atmospheric aerosols is the ratio of the unresolved to the resolved hydrocarbon components (U : R). U : R values for rural, mixed and urban western United States samples, for example, are 0.2}4, 1.4}3.4 and 0.9}25, respectively. Generally, urban aerosols contain the largest ratio of petroleum-derived compounds. The hump: n-alkane ratios (U : R) are determined from the gas chromatogram by the area of unresolved material above the background (measured by planimetry or integration) divided by the sum of the GC area of resolved n-alkanes and other major components (Simoneit, 1984; Abas and Simoneit, 1997). The U : R values for the particulate samples from RT (4.6) and CN (4.4) imply that the major sources of nalkanes in these samples can be attributed to fossil fuel combustion. On the other hand, the U : R values for QBV (2.1) and TF (1.9) imply in a mixed origin for these n-alkanes. These values are comparable to the ones observed at Ibadan (4.3), Sokoto (4.0) and Maiduguri (3.9) in Nigeria, Africa (Simoneit et al., 1988) and also these at the Sugarpine Pt State Park (1.9), D and D Ranch (1.8) and Sierra Ski Ranch (2.0) in the United States (Simoneit, 1984). Molecular markers have been utilized as con"rmation indicators for petroleum residues, for higher plant wax and resin residues, and for pyrogenic components, which comprise the solvent}soluble organic matter of aerosols. Examples are the extended tricyclic terpanes, the 17a(H), 21b(H)-hopanes, the steranes and the isoprenoids, pristane and phytane. They con"rm an origin from petroleum, e.g., an unburned fuel component such as diesel. The identi"cation of these compounds is based primarily on their mass spectra and GC retention times. The hopanes occurrence is usually at low concentrations, but their overall distribution signatures within samples can be easily determined by CG}MS and utilized for comparison purposes. This is based on the m/z 191 ion intensity in the GC}MS data, which is the base peak of most of the triterpanes and the extended tricyclic terpanes. The presence of the hopane molecular markers con"rms an input source from fossil fuel utilization (i.e., vehicular tra$c) (Simoneit, 1984; Abas and Simoneit, 1997). The triterpane distribution patterns for the aerosol samples are shown in Figs. 2d, h, 4a and d. The 17H(a),
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Table 3 Aliphatic hydrocarbons identi"ed and quanti"ed in the particulate matter of the aerosol samples collected in four areas of Rio de Janeiro No
Compound
Diagnostic ion (m/z)
RT (ng/m3)
CN (ng/m3)
QBV (ng/m3)
TF (ng/m3)
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
n-Tetradecane n-Pentadecane n-Hexadecane n-Heptadecane Pristane n-Octadecane Phytane n-Nonadecane n-Eicosane n-Heneicosane n-Docosane n-Tricosane n-Tetracosane n-Pentacosane n-Hexacosane n-Heptacosane n-Octacosane n-Nonacosane n-Triacontane n-Hentriacontane n-Dotriacontane n-Tritriacontane n-Tetratriacontane n-Pentatriacontane n-Hexatriacontane n-Heptatriacontane 18a(H)-22,29,30-trisnorneohopane(Ts) 17a(H)!22,29,30-trisnorhopane (Tm) 17a(H),21b (H)-30-norhopane Triterpene 17a(H),21b(H)-hopane 17a(H),21b(H)-homohopane (22S) 17a(H),21b(H)-homohopane(22R) 17a(H),21b(H)-bishomohopane (22S) 17a(H),21b(H)-bishomohopane (22R) 17a(H),21b(H)-trishomohopane(22S) 17a(H),21b(H)-trishomohopane(22R) 17a(H),21b(H)-tetrahomohopane(22S) 17a(H),21b(H)-tetrahomohopane(22R) 17a(H),21b(H)-pentahomohopane(22S) 17a(H),21b(H)-pentahomohopane(22R) steranes C aaa 27 steranes C aaa 28 steranes C aaa 29 steranes C abb 27 steranes C abb 28 steranes C abb 29
85/198 85/212 85/226 85/240 183/268 85//254 183/282 85/268 85/282 85/296 85/310 85/324 85/338 85/352 85/366 85/380 85/394 85/408 85/422 85/436 85/450 85/464 85/478 85 85 85 191/370 191/370 191/398 191/410 191/412 191/426 191/426 191/440 191/440 191/454 191/454 191/468 191/468 191/482 191/482 217/372 217/386 217/400 218/372 218/386 218/400
0.89 0.61 0.98 1.6 1.01 3.05 2.48 8.10 23.17 30.02 57.15 70.35 72.92 72.13 69.67 38.73 13.30 20.63 9.5 10.09 3.08 2.51 4.34 1.93 1.14 # # 8.86 26.19 ! 14.42 6.75 4.77 0.39 0.44 n.a. n.a. n.a. n.a. n.a. n.a. tr tr tr tr tr tr
! # # # # # # # 6.67 6.98 17.21 26.56 22.54 25.43 13.93 23.45 19.09 24.52 14.91 18.70 6.80 5.81 2.89 1.13 0.52 # # # # ! # # # # # # # # # # # # # # # # #
! tr tr ! tr ! tr tr # 2.07 1.82 1.75 2.15 3.59 3.53 4.08 5.55 13.60 4.34 7.51 2.51 2.75 1.19 0.93 0.57 0.38 # # # ! # # # # # # # # # # # # # # # # #
0.13 0.98 2.35 2.04 0.81 1.56 1.49 1.5 3.69 5.3 7.1 6.58 13.99 5.54 2.38 3.13 2.65 15.10 2.98 4.44 2.24 2.62 1.79 1.53 1.01 # # ! # 3.88 # # # ! ! ! ! ! ! ! ! ! ! ! ! ! !
Note: *"RT, CN, QBV, TF, see Table 1.#"identi"ed. !"not identi"ed. tr"identi"ed in trace quantities. n.a."not analyzed. aaa"5a(H),14a(H),17a(H)-steranes. abb"5a(H),14b(H),17b(H)-steranes.
21H(b)-hopane series is present in CN, RT, and QBV samples ranging from C to C (typical of a petroleum 27 35 input to the aerosols; Simoneit, 1984), whereas for Tijuca
Forest they are present only at trace levels. Steranes and diasteranes are additional molecular markers commonly found in petroleum generally at a concentration lower
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Table 4 Comparison of selected hydrocarbon concentrations in Barcelona and Rio de Janeiro cities
n-tridecane n-heptadecane n-nonadecane Total aliphatic hydrocarbons PHE FLU PY B[ghi]P Total PAH
BC1! (ng/m3)
BC2" (ng/m3)
RT (ng/m3)
CN (ng/m3)
65 27 32 625 1.3 4.3 5.5 7.7 80
16 16 16 160 2.6 10 15 12 220
70 39 21 581 1.0 1.7 3.4 0.5 86
27 24 24 237 4.6 12 18 10 67
Note: PHE"phenanthrene; FLU"#uoranthene; PY"pyrene; B[ghi]P"benzo[ghi]perylene. !Rosell et al. (1991). "Aceves and Grimalt (1992).
Fig. 4. Aliphatic hydrocarbon fraction of the Cinela( ndia sample: (A) mass fragmentogram m/z 191, characteristic ion for terpanes (peaks are of the 17a(H), 21b(H)-hopane series); (B) mass fragmentogram (m/z 217) characteristic of aaa R/S steranes (aaa R/S"5a(H), 14a(H), 17a(H)-steranes, 20R or S); (C) mass fragmentogram (m/z 218) characteristic of abb R/S steranes (abb R/S"5a(H), 14b(H), 17b(H)steranes 20R or S). Aliphatic hydrocarbon fraction of the Quinta da Boa Vista Park sample: (D) mass fragmentogram m/z 191, characteristic ion for the terpanes (peaks are of the 17a(H), 21b(H)-hopane series): (E) mass fragmentogram (m/z 217) characteristic of aaa R/S steranes; (F) mass fragmentogram (m/z 218) characteristic of abb R/S steranes.
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than that of hopanes. These hydrocarbons are not present in contemporary biogenic materials and are found in engine lubricants but not in gasoline or diesel fuel. They are introduced into the atmosphere from vehicular emissions. Steranes are only present in aerosols at trace levels. The distribution signature in GC}MS data of, for example, the m/z 217 and m/z 218 ion peaks for steranes, are again useful supporting evidence for a petroleumderived input (Simoneit, 1984). Typical sterane fragmentograms are shown in Fig. 4b}e for aaa steranes and Fig. 4c}f for abb steranes. The Tijuca Forest sample did not contain detectable amounts of these compounds. The presence of hopanes and steranes in the hydrocarbon fractions of RT, CN and QBV con"rms an input source from fossil fuel utilization. They were introduced into the atmosphere from vehicular emissions (engine lubricants but not in gasoline or diesel fuels). These results are similar to the hopanes and steranes ambient concentrations measured in the Los Angeles atmosphere. Their presence were also attributed mainly to vehicular exhaust emissions, although fossil fuel markers can be emitted from other sources (Simoneit, 1984). All aliphatic hydrocarbons identi"ed and quanti"ed in the particulate matter of these aerosol samples are shown in Table 2, Table 3 and Fig. 5. Much higher total aliphatic hydrocarbons concentrations are obvious for
Rebouc7 as Tunnel and Cinela( ndia sites as compared to Quinta da Boa Vista Park and Tijuca Forest. The petroleum contamination is signi"cantly greater in these urban areas as can be seen from the petroleum residue and hump to normal ratio data in Table 2. The RT and CN sites exhibit high petroleum residues, but the plant wax components are not completely suppressed, as observed also in the Los Angeles air basin (Simoneit, 1984). Even a heavily contaminated aerosol has a slight predominance of C , C and C , the plant wax components. 25 27 29 To summarize, coupling C , CPI, in some cases U : R .!9 values, and molecular marker identi"cation allow the classi"cation of natural biogenic and anthropogenic components of atmospheric aerosols. The determination of C provides the strongest indication of contempor.!9 ary biogenic components in aerosols, mainly in the nalkanes serie. The CPI is a diagnostic parameter, where a high CPI ('3) indicates a major incorporation of recent biological constituents into the aerosol sample. The admixture of anthropogenic contaminants reduces the CPI such that values of about one re#ect the dominant input of anthropogenic fossil fuel compounds. Moreover, the hydrocarbon fractions typically carry the greatest imprint of pollutants. Molecular marker analysis provides supportive evidence for such assessments. Vehicular exhaust, for example, can be distinguished from
Fig. 5. n-Alkane concentration distributions for all the samples.
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Table 5 Aromatic hydrocarbons identi"ed and quanti"ed in the particulate matter of the aerosol samples collected in four areas of Rio de Janeiro N3
Compound
Diagnostic ion (m/z)
RT (ng/m3)
CN (ng/m3)
QBV (ng/m3)
TF (ng/m3)
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
Acenaphthylene Acenaphthene 9H-#uorene Isopropyldimethylnaphthalene (cadalene) Phenanthrene Methylphenanthrenes Dimethylphenanthrenes Fluoranthene Pyrene Norsimonellite Benzo[ghi]#uoranthene Simonellite Retene Trimethylphenanthrenes Benz[a]anthracene Chrysene/triphenylene Benzo#uoranthenes (b#k) Benzo[e]pyrene Benzo[a]pyrene Indeno[7,1,2,3!cdef]chrysene Indeno[1,2,3!cd]pyrene Benzo[ghi]perylene Coronene Monoaromatic 8,4-secohopane C 29 Monoaromatic 8,4-secohopane C 30 Monoaromatic 8,4-secohopane C R 31 Monoaromatic 8,4-secohopane C S 31
152 154 166 183/198 178 192 206 202 202 223/238 226 237/252 219/234 220 228 228 252 252 252 276 276 276 300 365/394 365/408 365/422 365/422
4.29 2.20 ! 2.70 4.63
5.32 # 0.005 ! 1.00 tr # 1.65 3.39 tr ! tr # tr 2.01 10.71 15.46 # 10.67 2.24 4.69 9.98 # # # ! !
0.012 ! 0.0049 # 0.085 # # 0.15 0.18 # # # # # 0.073 0.754 1.54 ! 0.876 0.48 0.226 0.516 # tr tr ! !
0.065 ! ! # 0.21 # # 0.36 0.33 0.41 tr 0.59 0.42 tr # 0.03 0.31 ! 0.19 0.24 0.46 0.18 ! ! ! ! !
12.07 18.19 6.09 13.42 4.97 8.65 # 2.11 2.43 ! ! 0.58 ! ! 0.49 ! 2.42 0.65 # #
Note: *"RT, CN, QBV, TF, see Table 1. #"identi"ed. !"not identi"ed. tr"identi"ed in trace quantities.
natural background (plant wax and resin residues) by the presence of petroleum tracers such as steranes and hopanes (Abas and Simoneit, 1997). The basic results are clear; vehicular tra$c with the associated fuels and lubricants emit petroleum residues comprised of n-alkanes with no carbon number predominance, unresolvable hydrocarbons components (hump) and molecular indicators to the ambient atmosphere. From our data, it can be observed that RT and CN have a dominant contribution of n-alkanes from petroleum (97.5% and 90.2%, respectively) and QBV Park and TF have a signi"cant contribution from vascular plant wax (25% and 16%, respectively). 3.3. Aromatic hydrocarbon fractions The usual series of polycyclic aromatic hydrocarbons (PAH), consisting of phenanthrene, #uoranthene, pyrene,
benzanthracene, benzo#uoranthenes, benzopyrenes and indenopyrenes are present in the four samples, but in the Tijuca Forest sample they are observed only at trace levels (Table 5). The composite fragmentograms from selected PAH in RT and CN are illustrated in Fig. 6 and summarized in Fig. 7. The concentrations of some individual and total average PAH in the RT and CN samples are comparable to the ones observed in Barcelona city } BC1 (Rosell et al., 1991). Some results are better compared with data from another analysis also in Barcelona } BC2, Table 4 (Aceves and Grimalt, 1992). In order to assess the di!erent sources and origins of PAH present in the aerosols, a comparison can be made between characteristic ratios calculated and measured for the present aerosols. The comparison of the values listed in Table 6 with those associated with the PAH pro"les sampled in the
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Fig. 6. Composite fragmentograms (sum of molecular or fragment ion intensities of the dominant PAH) for the aromatic fractions in the aerosols. For numbers, see Table 5: (A) CN; (C) RT (m/z 152, 178, 183, 192, 206, 202); (B) CN; (D) RT (m/z 226, 228, 252, 276, 300, 365).
D. de Almeida Azevedo et al. / Atmospheric Environment 33 (1999) 4987}5001
city areas con"rms their usefulness for the di!erentiation of the sources discussed above. From the comparison of Tables 6 and 7 it can be concluded, once more, that the main source contributing to the aerosol PAH mixture is vehicle emissions (car emissions and used motor or lubricating oils). Values of the ratio #uoranthene/pyrene are close to those observed in used motor oil and car emission in all sites. In addition, the ratio Bz(a)an/ (Bz(a)an#Chr#Try) to RT con"rms the contribution of lubricating oil. A decrease in the abundance of some PAH such as phenanthrene, #uoranthene and pyrene (Fig. 7) can be observed from RT'CN'QBV'TF. This trend is true for the total aromatic hydrocarbons (Table 5) and also for the total suspended particulate matter (TSP, Table 2). The TSP shows elevated levels for samples CN}RT}QBV ('227 lg/m3) as compared with the WHO (World Health Organization) regulation limits (150}230 lg/m3) and also the Brazilian Regulation limits (Resolution Conama no. 03; Feema, 1995). Only TF shows a low TSP value (27 lg/m3). The concentrations of TSP measured during this study were a little higher in
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comparison to the range of concentrations reported previously for Rio de Janeiro (Feema, 1995), unless for TF. A series of monoaromatic 8,4-secohopanes (C }C ) 29 31 was also observed for the three more polluted sites, although for QBV Park only at trace levels. As often found for D-ring monoaromatic 8,14- secohopanoids in crude oils, the C and C components were dominant in the 29 30 samples analyzed, although traces of the C isomeric 31 pair were also detected (see Fig. 6d, components 71}73). The C compound was a dominant peak in the aromatic 29 fraction of the sample from Rebouc7 as Tunnel. The presence of these compounds was con"rmed by their mass spectra and the m/z 365 key ion. They have been reported in crude oils from South Texas and various oil shales (Killops, 1991). These compounds found in the TSP of aerosol samples would originate from petroleum fuel used in vehicles and are characteristic of petroleum used in Brazil. The presence of secohopanoids in the aerosol particulate matter con"rms emissions from vehicles using petroleum products containing these biomarkers.
4. Conclusions It could be veri"ed that almost the same level of pollution exists in RT and CN. This observation was based on Table 2, all the data analysis and also the presence of hopanes and steranes. The QBV site, despite being located in a polluted district, presents an intermediate level of pollution as evidenced by the smaller U : R, CPI, and total PAH and n-alkanes. Furthermore, presents the greatest biogenic hydrocarbons percentage (25%). The TF sample shows smaller U : R, a greater percentage of n-alkanes from plant wax, the hopane series only in trace quantities, no steranes and PAH at
Table 7 Ratios derived from the PAH composition of the aerosols collected in Rio de Janeiro
Fig. 7. Selected PAH concentration distributions. (ACY" acenaphthylene; PHE"phenanthrene; FLT"#uoranthene; PY"pyrene; CHR"chrysene; BaP"benzo[a]pyrene; BghiP" benzo[ghi]perylene).
Fl/(Fl#Py) Bz(a)an/(Bz(a)an#Chr#Try)
RT
CN
QBV
TF
0.40 0.47
0.34 0.15
0.45 *
0.52 *
Table 6 Characteristic ratios from the PAH composition of some potential source inputs to urban atmosphere (Sicre et al., 1987)
Fl/(Fl#Py) Bz(a)an/(Bz(a)an#Chr#Try)
Crude oil
Used motor oil
Car emissions (gasoline)
Wood soot
0.18$0.06 0.16$0.12
0.36$0.08 0.5
0.43$0.08 *
* 0.40$0.09
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trace levels. It was observed that RT, CN and QBV Park are polluted by emissions from incomplete combustion of petroleum fuels as con"rmed by the biomarker patterns (hopanes, steranes, n-alkanes). For RT and CN, a higher U : R and CPI&1.0 was also observed. The emissions originate from the heavy tra$c. The Tijuca Forest site presented low pollution levels, despite the fact that it is surrounded by the city. This can be attributed to the dilution e!ect of a large area (5.650.525 m2) devoid of pollution sources, cleaning (sink) e!ect of the luxurious vegetation and the wind regimes of the site. We suggest that there is a decrease in the degree of pollution in the order RT'CN'QBV'TF, as expected from the traf"c density (3542, 3192, 1595, 844 vehicles/hour in the surrounding area, respectively). Unfortunately all the sites are polluted, with the lowest level in Tijuca forest.
Acknowledgements We would like to thank CNPq, FUJB, FAPERJ for "nancial support, CET-RIO for tra$c data and the reviewers, especially Dr. B.R.T. Simoneit, for all the comments and suggestions.
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