PRELIMINARY STUDY OF EXTRACTABLE ORGANIC MATTER IN AEROSOLS FROM BEIJING AND GUIYANG, CHINA

SHENG GUOYINGI, FU JIAMOI, ZHANG JIAN1, XU YUPINGI and B.R.T. SIMONEIT2*

1lnstitute of Geochemistry, Academia Sinica, Guiyang, Guizhou, P.R. China 2Environmental Geochemistry Group, College of Oceanography, Oregon State University,

Corvallis, Oregon 97331, U.S.A.

ABSTRACT

The solvent-extractable compounds (lipids) of four samples, which were collected from a western suburb of Beijing and in the city of Guiyang, P.R. China, respectively, using a standard high volume air sampler, were investigated to determine the distributions of hydrocarbon compounds. The preliminary results show that all samples contain aliphatic hydrocarbons including n-alkanes, steranes and terpanes, probably derived from either biogenic sources (vascular plant wax input) and/or fossil fuel contamination (coal, crude oil, etc.). However, b-carotane found in the Guiyang aerosol samples may originate from geological or petroleum sour-ces. Polynuclear aromatic hydrocarbons, which are considered to be combustion products from fossil fuels such as petroleum and, especially in this case, coal burning, are also widely distributed in all samples. Furthermore, some apparent fractionation phenomena of organic compounds are observed in samples from different heights above ground.

Keywords: Beijing, Guiyang, aerosol, hydrocarbons, b-carotane, petroliferous source, microbial source

INTRODUCTION

The comprehensive analysis of solvent-ex-tractable compounds (lipids) that are as-sociated with carbon-containing aerosols can provide discriminating evidence for the as-sessment of human impact on the lower tropospheric environment. Lipids have been characterized for organic matter in aerosols over urban, rural, remote and oceanic areas (e.g. Cox et al., 1982; Gagosian et al., 1982, 1987; Simoneit, 1984, 1986, 1987; Mazurek and Simoneit, 1984; Simoneit et al., 1983, 1988). However, such reports are rare for samples from China (Lamb et al., 1980).

Presented here is a preliminary study on the aliphatic and aromatic hydrocarbon fractions of extracts of selected aerosol samples from Beijing and Guiyang (Fig. 1).

EXPERIMENTAL

Samples

Four aerosol samples from the western suburb of Beijing and Guiyang, China (Fig. 1) were obtained with a standard high volume air sampler made in Qindao, China, on quartz fiber filters (diameter: 5 cm). The quartz fiber filters were cleaned by heating

* Corresponding author

78

ORGANIC MATTER IN AEROSOLS

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Fig. 1. Geographical map showing the location of Beijing and Guiyang, P.R. China, where the aerosol samples were collected.

prior to use. After sample acquisiton they were folded and stored in precleaned glass jars with 3-5 ml methylene chloride (CH2Cl2) solvent. The sampler was also cleaned by wiping and rinsing with solvent (CHZCI2).

Analytical method

The filter samples were extracted in the jars with benzene, benzene/chloroform (2:1 v/v) and benzene/chloroform (1:2 v/v), respectively, using ultrasonic agitation for fifteen minutes and the extracts were then

combined. Total extracts were separated by standard thin layer chromatography to yield the aliphatic and aromatic hydrocar-bon fractions. All glassware used was cleaned prior to use by annealing at 550° C for three hours. The hydrocarbon fractions were subjected to gas chromatographic (GC) and computerized gas chromato-graphy—mass spectrometric (C—GC—MS) analyses. The C—GC—MS analyses were carried out on a FinniganMAT model 4515 C—GC—MS system. More detailed analyti-cal descriptions have been reported pre-viously (Fu et al., 1986).

RK-1 RK-2 GY-1 GY-2

1.5 4.5 1.5 4.5

2.2 1.6 1.6 1.3

n-C29 II-C24 n-C26 II-C24

Beijing Beijing Guiyang Guiyang

C16-C33 C19-C31 C14-C36 C11-C35

ORGANIC MATTER IN AEROSOLS 79

For comparison, the analytical results of sample PK-1 are used. This sample was separated and analyzed by the Environ-mental Geochemistry Group, College of Oceanography, Oregon State University, as described elsewhere (Simoneit et al., 1988).

RESULTS AND DISCUSSION

Pk-1 had an extract yield of 1715 lg, which corresponds to 48 ig of lipid matter per m3 of air. This is a rather high burden of organic matter for an urban aerosol com-pared to similar data for some other cities (e.g. typical ranges: Los Angeles 3-4 m&'m3

and Ibadan, Nigeria - 6 Mg/m3 (Simoneit, 1984, 1986; Cox et al., 1982)). Thus it is of interest to differentiate the natural and anthropogenic sources.

Normal alkanes

The normal alkane distribution ranges and their relative concentrations are given in Table 1 and Fig. 2. The n-alkane distribu-tion featuresof the Beijing samples are the bimodal patterns with CmaX of C21 and C29 for PK-1 and C24 and C29 for RK-2, both ranging from <C20 to C33. A marked odd-over-even carbon number predominance is observed in the range of C23—C33, with CPI

values of 2.2 (RK-1) and 1.6(RK-2). In com-parison, the Guiyang samples are unimodal with a C max at C26 or C27 and range from C11 to C36. CPI values are 1.3 (sample collected 4.5 m above ground) and 1.6 (sample col-lected 1.5 m above ground). The alkane dis-tributions of the Beijing suburban samples give a strong indication for mainly vascular plant wax input and the maximum at lower carbon numbers may indicate an input from microbial or petroliferous sources (Simoneit, 1979, 1984, 1985, 1986) . The Guiyang samples show fewer characteris-tics of higher plant wax input and more sig-nificant input of petroliferous hydrocarbons (wider range of n-alkanes from C11—C20). This correlates well with the urban environ-ment where the samples were obtained.

Acyclic isoprenoid hydrocarbons

Three of four samples show a phytane over pristane predominance and the presence of these isoprenoid hydrocarbons confirms a petroleum component in the aerosols.

Cyclic isoprenoid hydrocarbons

Steranes and triterpanes are present in these aerosols indicating an input of fossil fuel residues. The sterane distributions

TABLE 1

Sample Locations and Analytical Results for n-Alkanes

Elevation n-Alkanes* Sample above No. ground (m) Location Range of carbon number CmaX CPI

*Parameter definitions are found in Mazurek and Simoneit (1984).

C29

C27

C31

6 i J I T

80 ORGANIC MATTER IN AEROSOLS

m/ z

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99

C29

C31

C24

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m/z GY-1

99

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C17 Pr C15

m/ z

C24

C27

C21

Ph

Fig. 2. Mass fragmentograms for m/z 99, indicator for n-alkanes (carbon numbers of n-alkanes are indicated, Pr = pristane, Ph = phytane): (a) PK-1 (Beijing); (b) PK-2; (c) GY-1 (Guiyang); (d) GU-2.

show differences between the Beijing and Guiyang samples, such as the relative abundance sequence of C29 > C27 C28 ver-sus C29 > C28 > C27 for both sets of samples, respectively (cf. Fig. 3) . The relative con-centrations of steranes in the Beijing

samples is lower than in the Guiyang samples. Full series of 17a(H),21(3(H)-hopane homologs (C27—C 33, except C2 ) were found in the samples from both cities (Fig. 4). The source of both biomarker series is inferred to be from mainly petroleum

C29

~

C29

217_

m/z

f

C28

L

J

GY-1

C27

ORGANIC MATTER IN AEROSOLS 81

Fig. 3. Mass fragmentograms for m/z 217 and 218, key ions for sterane hydrocarbons. (a,b) PK-1; (c,d) GY-1.

residues, since these sterane and hopane distribution patterns are analogous to those reported by Simoneit (1984, 1985). In this case, these biomarkers may also be source indicators of fossil fuel hydrocarbons derived from coals and other geological materials, in addition to petroleum.

It is worthwhile to note that (3-carotane was detected in small amounts in the Guiyang aerosol samples (Fig. 5). This com-poundfurther indicates a fossil fuel source, possibly from petroleum products refined from crude oils of the Kalamayi Field, where (3-carotane is a dominant component

Fig. 5. Total ion current trace for the total saturated hydrocarbons in sample GY-2 (carbon numbers of the n-alkanes are indicated, Pr = pristane, Ph = phytane).

C31 C32 C33

C27

m/ z

191 C29

G Y-1

82 ORGANIC MATTER IN AEROSOLS

C30

C29

C30

Fig. 4. Mass fragmentograms for m/z 191, key ion for triterpane hydrocarbons for two examples (shaded peaks are the 17a(H),21~3(H)-hopanes typical of petroleum): (a) PK-1; (b) GY-1.

24 2627

23 25 29

22

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31

30

33

21 28

35 b — Carotane \.

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15 Ph

ORGANIC MATTER IN AEROSOLS 83

of the total hydrocarbons (Jiang and Fowler, 1986). Alternatively, a geological source may be the origin since Guiyang is located in a small basin which is sur-rounded by outcrops of Permian—Jurassic carbonate—clastic formations, including coal-bearing facies, that could introduce particulate matter containing b-carotane to the urban aerosol. This latter source is probably less likely.

Polynuclear aromatic hydrocarbons

Major polynuclear aromatic hydrocar-bons (PAH) identified in the aerosol samples are naphthalene and phenanth-rene, with their alkyl derivatives, as well as pyrene and methylpyrene. Long chain alkylbenzenes and naphthalenes are also found occasionally. In addition, there are aromatic sesquiterpenoids (e.g. cadalene, 5,6,7,8-tetrahydrocadalene and calamen-ene) and terrestrial aromatic diterpenoids derived from the abietane skeleton (e.g. retene (Fig. 6);18-norabieta-8,11,13-triene; etc.), and lesser amounts of benzofluoran-thene and cuparene. These sesquiterpenoid aromatic hydrocarbons can be considered to originate from geological sources, especial-ly coal. The aromatic diterpenoids may originate from coal and wood combustion and/or by natural emissions from conifer-ous trees (Simoneit, 1979, 1984, 1986; Sim-oneit and Mazurek, 1982). Pyrene, methyl-pyrene and benzofluoranthene found in Guiyang aerosols are presumed to also originate from burning of coal, which is the major fuel for the people living in that city.

It is of interest to note that there is a cer-tain relationship between the aromatic hydrocarbon composition and sampling height in both Beijing and Guiyang. Only phenanthrene and its alkyl derivatives

were detected near ground level in both cities (Fig. 6), and pyrene, methylpyrene and benzofluoranthese were observed in the Guiyang samples near ground level as well. But in the aerosols obtained from 4.5 m above ground there are only traces of naphthalene and its alkyl derivatives rather than the previous homologs. In addi-tion, the CPI of the wax n-alkanes is greater for the elevated sampled, indicating a higher wax concentration at higher levels, or conversely a greater fossil fuel com-ponent at lower levels. This may be due to a volatility difference among the comp-ounds or their differential association with particles during the injection mechanism from the sources.

CONCLUSION

Aliphatic hydrocarbons including nor-mal alkanes, steranes and terpanes are widely distributed in solvent-extractable lipid matter of aerosols from Chinese urban areas. Their distribution patterns show evidence for both a biogenic origin (vascular plant wax input) and fossil fuel contamina-tion (coal, crude oil etc.) .

PAH and alkyl—PAH are observed and derive mainly from fossil fuels, especially coal burning and petroleum sources. b-Carotene found in the Guiyang aerosol samples may also originate from petroleum sources.

Certain fractionation phenomena of or-ganic compounds are apparent in samples derived from different heights above the ground. For instance, particle-associated compounds originating from emissions of fos-sil fuel combustion as, for example, phenan-threne homologs, pyrene, benzofluoranthese, etc., are found mainly in samples nearer ground level and vascular plant waxes are more enhanced at elevated levels.

206

22 0

2 34

(b) m/z

178_

—Re

_-w~

G U-1

A t 1

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192_

1

206_

220

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84 ORGANIC MATTER IN AEROSOLS

ACKNOWLEDGEMENTS

We wish to thank Dr. Jan i N. Cardoso for technical training of one of us (S.G.) and Dr. Wan Gucun, Mrs. Qiu Huoqing and Mr. Yang Qiaohong for collecting the samples.

We also acknowledge Mrs. Liu Zhichun, Mr. Xiang, Tongshou and Mr. Li Zhenye for GC—MS analyses. One of us (B.R.T.S.) thanks the National Science Foundation for partial financial support (Atmospheric Research Section, Grant ATM-8509184).

192 ,Li

,

Fig. 5. Mass fragmentograms for the phenanthrene homologs (m/z 178, 192, 206, 220 and 234), Re = retene: (a) RK-1; (b) GY-1.

ORGANIC MATTER IN AEROSOLS 85

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