Polycyclic aromatic hydrocarbons PAH

Table 42.2 reports the aerial content of individual PAH in downtown Algiers and Oued Smar. Two "diagnostics ratios" referring to PAH are also reported, i.e.:

• [FA]/([FA]+[PY]): [Fluoranthene]/([Fluoranthene]+[Pyrene]) and

• [IPY]/([IPY]+[BPE]):[Indenopyrene]/([Indenopyrene]+[benzoperylene])

The total PAH concentrations recorded recently in downtown Algiers varied from 13 to 29 ng m"3, and maximum levels were recorded in winter. PAH reached concentration levels similar to those recorded in the atmosphere of Prato, Italy (Cincinelli et al., 2007), but lower than those found in Thessaloniki, Greece (Manoli et al., 2004). The concentrations of benzo(a)pyrene, often used as PAH indicator and regarded by the WHO as index for PAH-associated carcinogenicity (Yassaa et al., 2005), were in the range of 0.31~0.71 ng m"3 in downtown Algiers during 2005-2006, respectively, meeting the air quality guidelines of 1 ng m"3 (WHO, 2000). The rates reached by benzo(a) pyrene-equivalent carcinogenic power associated with airborne particulates (BaPE) were also calculated. This index, similar to TCDD-equivalence index defined for dioxin-like compounds, has been proposed to parameterize aerosol carcinogenicity better than having recourse to the benzo(a)pyrene alone. This approach seems suitable as far as sources do not emit BaPY at extents comparable to other "carcinogenic" PAH, or the same compound is decomposed much more extensively than congeners.

Table 42.2 Seasonal average PAH concentrations (ng m 3 of air) and some characteristic ratios in downtown Algiers and waste landfill. For compound identification, see the text.

Site

Downtown Algiers

Waste landfill

Year

1998-

1999

2005-

2006

1998-

1999

2005-2006

Compound

Sum.

Wint.

Sum.

Wint.

Sum.

Wint.

Sum.

Wint.

FL

n.ev.

n.ev.

2.47

1.31

n.ev.

n.ev.

5.07

0.27

Phe

n.ev.

n.ev.

1.14

1.99

n.ev.

n.ev.

42.38

4.41

Ant

n.ev.

n.ev.

0.23

0.50

n.ev.

n.ev.

18.23

0.27

Me-PHE/AN (S)

*

*

2.04

3.18

*

*

26.96

5.66

FA

1.0

5.9

1.22

1.54

1.6

17.5

12.69

4.45

PY

0.9

7.9

1.39

1.76

1.7

14.7

18.68

3.11

Me-FA/PY (X)

*

*

1.37

4.52

*

*

3.77

1.79

CPPY

0.2

5.6

0.08

0.25

0

4.8

0.24

0.63

BaA

0.5

2.9

0.60

1.32

1.0

7.8

1.28

1.31

Chr

1.1

4.0

0.38

1.18

3.1

13.8

1.90

1.26

BFA

1.4

4.9

1.35

1.57

1.8

11.7

2.45

2.94

BePY

0.7

2.4

0.57

1.14

1.1

3.9

1.04

0.95

BaPY

0.4

2.3

0.36

0.71

0.3

3.9

0.65

1.17

Pery

1.1

3.6

0.06

0.28

0.3

2.7

0.09

0.14

3-Me-CH

*

*

n.d

n.d

*

*

0.64

1.03

IcdPY

0.7

1.4

0.50

1.12

0.1

2.0

0.93

1.29

DahA

0

0.1

0.02

n.d

0

0.3

0.47

0.65

BghiP

n.ev.

n.ev.

0.91

1.78

n.ev.

n.ev.

1.55

1.68

CO

n.ev.

n.ev.

0.53

1.13

n.ev.

n.ev.

1.09

1.16

DBPY (S)

n.ev.

n.ev.

0.00

0.97

n.ev.

n.ev.

1.48

1.50

Total met-alkyl-PAH

5.4

19.0

3.4

7.7

13.8

53.5

31.37

8.48

TOTAL

13.4

60

15.2

26.2

24.8

136.6

141.6

35.7

[FA]/([FA]+[PY])

0.54

0.43

0.47

0.47

0.48

0.54

0.37

0.59

[IPY]/([IPY]+[BPY])

0.35

0.49

0.35

0.39

0.21

0.50

0.33

0.55

n.d: not detected, n.ev.: not evaluated, total met-alkyl-PAH: total methyl-alkylated PAH, FL: Fluo-rene, Phe: Phenanthrene, Ant: Anthracene, Me-PHhe/AN (S): Methyl-phenanthrene/anthracene (Sum), FA: Fluoranthene, PY: Pyrene, Me-FA/PY (S): Methyl-fluoranthene/pyrene, CPPY: Cyclopen-tapyrene, BaA: Benzo(a)anthracene, Chr: Chrysene, BFA: Benzofluoranthene = sum of Ben-zo(b)fluoranthene, Benzo(k)fluoranthene, Benzo(a)fluoranthene, BePY: Benzo(e)pyrene, BaPY: Ben-zo(a)pyrene, Pery: Perylene, 3-Me-CH: 3-methylcholanthrene, IcdPY: Indeno(1,2,3-cd)pyrene, AahA: Dibenzo(a,h)anthracene, BghiP: Benzo(ghi)perylene, CO: Coronane, DBPY (S): Dibenzopyrene =SDibenzo(a,l)pyrene + Dibenzo(a,e)pyrene + Dibenzo(a,i)pyrene + Dibenzo(a,h)pyrene).

BaPE was calculated by using the following formula, drawn from the National Toxicological Committee for Italy in 1991 on the basis of carcinogenic potency studies:

[BaPE] = [BaPY] + 0.06 * [BaAN] + 0.07 * [BF] + 0.08 * [IPY] + 0.6 * [DahA].

The BaPE values in downtown Algiers in 2005-2006 ranged from 0.41 to 0.99, with the highest ones corresponding to winter samples. These values were similar to those observed previously in 1998-1999 (Yassaa et al., 2005), but lower than those recorded in Oued Smar in 1998-1999 and 2002-2003 (Ladji et al., 2007) and in urban atmosphere of Guangzhou, China (Bi et al., 2003).

The approach of "diagnostic ratios" between selected PAH congeners (DRPAH) was attempted in the aim of drawing information about the nature of airborne particulates sources in Algiers. This approach relies on the peculiarity of ratio rates with respect to the kind of emission and the concurrent influence of atmospheric reactivity versus target pollutants. Unfortunately no DRPAH exists, so peculiar and even so independent of ambient conditions, to certainly identify the PAH source; this is the reason why recently some criticism has been moved to that methodology. Nevertheless, the use of more DRPAH involving congeners of similar volatility and ambient inertness allows drawing enough insights to distinguish petrogenic from wood and coal-associated fuels, and concerning the aging of air parcels holding particulates. For instance, [FA]/([FA]+[PY]) rates close to 0.40, 0.48, 0.55, 0.67, and 0.9 were calculated for electric power plant, motor vehicle, biomass burning, coke plant, and urban refuse incinerator exhausts, respectively. In Oued Smar samples of 2002-2003, the ratio [FA]/([FA]+[PY]) was around 0.37 and 0.55 in summer and in winter, respectively.

Thus, it was similar to that of the tailpipe emission, especially from old motor vehicles and very close to that of biomass burning. This seems to indicate that while self-combustion of mixed wastes remains the main source of PAH, the influence of the automobile source (trucks and machines used in the landfill) onto the Oued Smar ambient air cannot be neglected. Several studies reported that the ratio of indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene+benzo[ghi]perylene) ([IPY]/ ([IPY]+[BPE])) depends upon the kind of combustion source. Documented values of this ratio are 0.18 for gasoline exhausts, 0.37 for diesel particulates, 0.56 for coal soot, and 0.62 for wood-burning emissions (Gogou et al., 1996). In downtown Algiers the recent value (2005-2006) of the [IcdP]/([IcdP]+[BghiP]) ratio was all-the-time equal to 0.36±0.3, emphasizing the importance of diesel emissions in Algiers atmosphere. This finding was further confirmed by the rates calculated for the fluoranthene/(fluoranthene+pyrene) [FLT]/([FLT] + [PY]) ratio (Cincinelli et al., 2007), equal to 0.46 ± 0.02 in downtown Algiers in 2005-2006 investigations.

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