Seasonal Variation of Volatile Poly Aromatic Hydrocarbons (PAHs) Released from Different Sources in South Cairo

Based on a year-round data-set (from January to November 2014), an intensive air sampling program was conducted during 2014 in four different function sites in South El-Tabbin city to study the temporally and spatially characteristics of Poly Aromatic Hydrocarbons (PAHs) in the gaseous and particulate phases. This area is considered as one of the most polluted areas in Egypt as it includes heavy industrial plants, as well as it is bounded by heavy traffic. A total of 48 atmospheric samples were collected by a high-volume active air sampler. The gaseous and particulate phases of PAHs were extracted and analyzed using Gas chromatography/mass spectrometry together. The total concentrations of the sixteen PAHs (which tagged the United States Environmental Protection Agency priority) in the air of the study area ranged from 76.48 ± 19.44 μg/m 3 to 26995.86 ± 2835.91 μg/m 3 . The average PAHs concentration in the coke production site was ~ 355 times of that in the residential area site. For the whole study area; 4, 5, and 6 rings PAHs were dominant and accounting for ~66% – ~84%. The total concentrations of combustion derived PAHs were ranged from 63.24 ± 17.35 μg/m 3 to 17546.97 ± 1848.55 μg/m 3 covering 65% − 83% of total PAHs which Environmental Management and Sustainable Development ISSN 2164-7682 2020, Vol. 9, No. 2 93 indicating large amounts of combustion sources existed from them in South El-Tabbin city. Seasonal trends of PAHs concentrations were observed with a high concentration in winter and low in summer where the average concentration of PAHs in winter was ~1.6 times higher than that in summer.


Introduction
Air with high concentrations of PAHs causes many adverse effects on different types of organisms, including plants, birds, and mammals. Some studies reported that there is a significant positive correlation between mortality by lung cancer in humans and exposure to PAHs from the exhaust from coke ovens, roofing-tar, and cigarette smoke. Some PAHs have been demonstrated to be carcinogenic in humans and experimental animals, and they are classified as carcinogenic materials by many organizations, including the United States Agency for Toxic Substances and Disease Registry (US ATSDR), the International Agency for Research on Cancer (IARC), the Department of Health and Human Services (DHHS), the National Occupation Safety and Health Administration (OSHA), and the USEPA. Light Molecular Weight (LMW) PAHs, except naphthalene, usually are associated with relatively lower toxicity (cancer risk) than Light Molecular Weight (HMW) PAHs with 5 or 6 aromatic rings. In other words, as molecular weight increases, the carcinogenicity of PAHs also increases with reducing acute toxicity. However, the most potent PAHs carcinogens have been identified to include anthracene (ANT), benzo[a]anthracene (BaA), benzo[a]pyrene (BaP), dibenz [a,h]anthracene (DBahA), chrysene (CHR), fluorine (FLO), and pyrene (PYR) (Armstrong et al., 2004;Bach et al., 2003;Public Health England, 2018; Canadian Council of Ministers of the Environment (CCME), 2010; Delgado-Saborit et al., 2011;Environmental Programs Directorate, 2011).
There is much information on the multi-ringed heavier PAHs but have left the lighter vapor-phase PAH components rather neglected. Although these lighter compounds have weaker carcinogenic/mutagenic properties, they are the most abundant in the urban atmosphere and react with other pollutants to form more toxic derivatives (Park et al., 2002). Thus, the implication of human exposure to mixtures of PAHs, rather than to individual substances, is important. The levels of individual PAHs vary over several orders of magnitude and are generally in the range of several ng/m3 to several µg/m3, which making an assessment on a regional scale difficult (Pandit et al., 2006;Singh et al., 2011).
The main objectives of this work can be summarized in the following points; 1) Measuring the concentration levels of ambient PAHs in gaseous and particulate phases, 2) Study the spatial and temporal variations of ambient PAH levels and their possible relationships with meteorological parameters, and 3) Identify and allocate possible sources of PAHs using diagnostic ratio. Results of this work obtained from an approximately 1-year sampling/analysis campaign of particulate and gaseous PAHs in different seasons during 2014 at four different sites in the city of El-Tabbin which considered one of the most polluted areas in Egypt.

Description of the Study Area
The study area for this study is located in the south of El-Tabbin city, as shown in Figure 1, with geographical coordinates of 29°44'59.92" N to 29°47'35.12" N latitude and31°17'35.45" Environmental Management andSustainable Development ISSN 2164-7682 2020, Vol. 9, No. 2 94 E to 31°20'12.13" E longitude, and a total area of 25 km2. The selected sampling area is surrounded by a mixture of urban, industrial, commercial and traffic activities as they are possible sources of PAHs especially the coke production plant. Furthermore, this area represents a large urban industrialized area in El-Tabbin city and even in Helwan city where metallurgical, chemical, coal, petrochemical, bricks and cement-producing plants are located. Acronyms, coordinates, and activities of sampling sites are indicated in Table 1. Distances between these sites are indicated in Figure 2.

Applied Methodology
The applied methodology in this study is originated from the US EPA Method TO-13A (Compendium Method for determination of PAHs in ambient air), (US EPA, 1999). Concisely, the method is based on using a High-Volume Air Sampler (Andersen Instruments Inc., 500 Technology Ct., Smyrna, GA) for the collection of PAHs from ambient air onto the sampling module that consists of particle filter and high-volume collection tube containing adsorbent media (i.e. sorbent cartridge). This system is capable of pulling ambient air through the filter/sorbent cartridge at a flow rate of approximately 225 l/min (i.e. 0.225 m 3 /min) to obtain a total sample volume of greater than 300 m 3 over a 24-hour period. Moreover, this method provides an efficient collection of most PAHs involving two-member rings or higher either in a particulate phase or in a gaseous phase through the utilization of quartz fiber filter with adsorbent cartridge consists of both polyurethane foam (PUF) and XAD-2® resin as a sorbent media where XAD-2® is intermediated between two layers of PUF in sandwiching configuration in order to minimize breakthrough of highly volatile PAHs. The sampling module inside the high-volume sampler is consists of metal filter holder capable of holding a 102-mm circular particle filter supported by a 16-mesh stainless-steel screen and attaching to a metal cylinder capable of holding a 65-mm outer diameter (OD) and 60-mm inner diameter (ID) x 125-mm in height borosilicate glass sorbent cartridge containing the adsorbent media (PUF and XAD-2®). The Gas Chromatography/Mass Spectroscopy (GC/MS) instrument is combined of two parts: GC that separates the chemicals in the sample and MS that identifies and quantifies the chemicals., for general specifications for Shimadzu -GCMS-QP5050A, it is a benchtop quadrupole mass spectrometer features an extended mass range to 900 Daltons and optional positive and negative chemical ionization (PCI and NCI). This wide variety of ionization modes and the ability to analyze high molecular weight compounds make the GCMS-QP5050A the answer to different application requirements. Furthermore, The Environmental Management and Sustainable Development ISSN 2164-7682 2020 GCMS-QP5050A can detect 100 pg of methyl stearate at S/N better than 60 in scan mode 'Single (or Selected) Ion Monitoring (SIM) mode is even more sensitive'. Scan speeds of up to 6,750 AMU/sec. are achieved with unit mass resolution. The MS is paired with GC-17A gas chromatograph, which uses Advanced Flow Control (AFC) for rapid, reproducible results. Additionally, all ion source parts can be accessed from the front of the instrument for easy maintenance. The efficient 150 L/sec turbomolecular pump and rotary pump quickly achieve a high vacuum in less than 5 minutes and this will reflect in minimal downtime. For developing calibration curve for GC/MS analysis, the stock standard solution of 16 PAHs mixed in methylene chloride: methanol (50:50) at the concentration of 2000 µg/ml (Sigma Aldrich Chemical Co. Inc. USA) was diluted first to the concentration of 25 ng/µL by taking 125 µL of the stock PAH standard and diluting with hexane in a 10-mL volumetric flask. After that, five concentration levels of PAH standards (i.e., 2.50 ng/µL, 1.25 ng/µL, 0.50 ng/µL, 0.25 ng/µL, and 0.10 ng/µL) were prepared prior GC/MS analysis, each 1 mL aliquot of the five calibration standards as well as 1mL portion of the sample extracts are spiked with 10 µL at concentration of 50 ng/ µL (after 1:40 dilution) of the mixture of deuterated PAH internal standard (Isotopically labeled PAH isomers at the concentration of 2000 µg/mL mixed in methylene chloride, Sigma Aldrich Chemical Co. Inc. USA), to yield a final concentration of 0.5 ng. This internal standard was used to quantify and correct the amounts of specific PAHs found in the samples.

Identification and Quantification of PAHs
Identification of PAHs compounds was based on comparing the measured mass spectra and retention times to reference standards. It was calculated by using eq. 1.
Where, A x = area response for the compound to be measured, counts A is = area response for the internal standard, counts. I s = amount of internal standard, ng/µL. RRF i = the mean RRF from the most recent initial calibration, dimensionless.
V i = volume of air sampled, std m 3 .
V t = volume of final extract, µL. D f = dilution factor for the extract. If there was no dilution, D f equals 1. If the sample was diluted, the D f is greater than 1.

Results and Discussion
In this study 16 PAHs were analyzed including includes Naphthalene (NAP), Acenaphthene difference in population, traffic density, and industry distribution, the PAH contribution from anthropogenic inputs varied in different function zones (Lodovici et al., 2003, Kong et al., 2010, Kim et al., 2013. The summary of the atmospheric PAHs mass concentrations for different sampling sites and seasons under study are provided in Tables (2): (5). As can be seen, the total amounts of analyzed PAHs (i.e. Total ∑16 PAHs) in the area under study varied from 76.48 ± 19.44 µg/m 3 in RA site to 26995.86 ± 2835.91 µg/m 3 in the CK site with a mean concentration of 7085.08 ± 773.98 µg/m 3 . PAHs concentrations demonstrate that the area under study is influenced by regional sources. In the nutshell, the total ∑16 PAHs concentrations, as well as the average concentrations of ∑16 PAHs over the seasonal sampling period in the different functional zones of the study area can be ordered as follow: CK site (at the border of On the other hand, Kong et al. (2010) concluded that PAHs concentrations associated with PM 2.5 in ten sites in five cities covering different city zones of Liaoning Province exhibit the following order as residential/commercial site (1900.89 ng/m 3 ) > commercial site (1053.83 ng/m 3 ) > industrial/commercial site (923.01 ng/m 3 ) > residential site (300.41 ng/m3) > urban background site (227.01 ng/m 3 ) > industrial site (75.32 ng/m 3 ). It should be noted that the industrial site is located in a coastal city where the air quality is well than the other four cities.
.  ISSN 2164-7682 2020 For the sake of illustration, Figure 3 shows the measured total PAH concentrations (i.e. Total ∑16 PAHs) over the seasonal sampling period for the different sampling sites, while Figure 4 shows the measured total PAHs concentrations for each compound (∑i PAHs) over the seasonal sampling period for each sampling site. Obviously from both figures, the highest mass concentrations of PAHs among the four sampling sites (either for Total ∑16 PAHs or ∑i PAHs) are found in the Coke samples whereas the lowest values are found in the Residential Area samples.   ISSN 2164-7682 2020 Kim et al. (2013) also indicated that the highest values for atmospheric PAHs are generally found when industrial, rather than traffic or residential, contributions are dominant. On the other hand, Zhang and Tao (2009) concluded that biofuel; wildfire, domestic coal combustion, coke production, and open straw burning are the most important sources for global atmospheric PAHs, accounting for 56.7%, 12.4%, 11.7%, 7.0%, and 2.7%, respectively. However, the combustion derived PAHs (COMPAHs), including FLA, PYR, CHR, BbF, BkF, BaA, BaP, IcdP, BghiP (Bourotte et al., 2005;Kong et al., 2010) can be used to identify the influence of combustion sources on PAHs. The total concentrations of COMPAHs in this study for the different sampling sites are ranged from 63.24 ± 17.35 µg/m 3 to 17546.97 ± 1848.55 µg/m 3 accounting for 65% − 83% of total PAHs with the highest mass percentages occurred in RA. The calculated COMPAH/ΣPAH ratios for different sampling sites are 0.65, 0.61, 0.75 and 0.83 for CK, TIMS, AAS, and RA, respectively. Wu et al. (2014) demonstrated that the total concentrations of COMPAHs cover 42% -84% and 75%-82% of PAHs associated with PM 2.5 and PM 10 , with the highest mass percentages found in Dongsheng (DS) site of sampling area of E'erduosi city in china. This site represents a residential site at the central urban adjacent to a heavy-traffic road.
However, results for the ring distribution of PAHs are comparable to others where 2-and 3-ring PAHs are the dominant form of the PAHs measured in coke manufacturing (Khalili et al., 1995;Yang et al., 1998). You (2008) concluded that 4-ring PAHs were most abundant Environmental Management and Sustainable Development ISSN 2164-7682 2020 during coal combustion, accounting for about 80%, 70% and 90% at three individual sampling points. The same conclusion was made by Arditsoglou et al., (2004) that the PAHs were dominated by 4-ring species (48-62%) followed by 3-ring compounds (38-41%) in fly ashes samples from lignite-fired power plants. 5-ring PAHs exhibited equal or even higher contribution respect to 3-and 4-ring species in coke oven stacks (Manoli et al., 2004). Additionally, Ravindra et al., (2006) indicated that the major source for 3-and 4-ring PAHs is coal combustion, while the major source for HMW PAHs (BaP, BbF, BghiP, and Ind) is gasoline vehicles. Therefore, PAHs at the four sites may come mainly from atmospheric transport of the coal combustion and vehicle emissions as both dominated the PAH sources. Regardless, as shown in Figure 5, the total PAHs concentrations (i.e. Total ∑16 PAHs) over the seasonal sampling period for the different sampling sites are well correlated with ∑LMW-PAHs, ∑MMW-PAHs, ∑HMW-PAHs, ∑COMPAHs, ∑C-PAHs over the seasonal sampling period for the different sampling sites with the correlation coefficients higher to 0.99. Incidentally, it is worth pointing out that the results of PAHs concentrations for this study are generally higher than most of the data reported for some urban areas or even areas proximity to the industrial complexes throughout the world. Table 6 comparing the average PAHs concentrations for some urban areas throughout the world with the data of the RA site.