Polycyclic aromatic hydrocarbons in ambient air

2010.01.24 ( V14b )

Polycyclic aromatic hydrocarbons in ambient air at four urban locations in Seoul, Korea

Ashish Anthwal1, Kweon Jung2, Hyun Jeong Kim2, Il-Sang Bae2, Ki-Hyun Kim1*

1Department of Earth & A ; Environmental Sciences, Sejong University Seoul, 143- 747 Korea

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2Seoul Metropolitan Institute of Public Health and Environment, Seoul, 137-734 Korea

Abstraction

This paper reports the monitoring consequences of 17 polycyclic aromatic hydrocarbon ( PAH ) compounds made at four urban locations in Seoul, Korea from February to July 2009. The average concentrations of PAH in gas plus atom stages were computed as 19.0 ( Jong Ro: JR ) , 17.7 ( Gwang Jin: GJ ) , 22.2 ( Gang Seo: GS ) , and 25.9 ng m-3 ( Yang Jae: YJ ) . The partitioning form of single PAH constituents were greatly differentiated between gas and atom stages. Despite such differences, phenanthrene ( PHN ) , pyrene ( PYR ) , and fluoranthene ( FLT ) were identified as the most abundant species ( about 55 % of the all PAHs ) at all sites. The overall consequences of this survey, if drawn by such attacks as the analysis of diagnostic ratios and chief constituent analysis ( PCA ) , suggest that the distribution of PAH at these urban sites is controlled by a combined consequence of such procedures as vehicle emanations, route dust, and coal burning.

Keywords: Polycyclic aromatic hydrocarbons ( PAHs ) ; Emission ; Factor analysis ; Anthropogenic

1. Introduction

A The major elements of megacities including the big sizes ( or graduated tables ) of population, energy ingestion, transit, and industries play a cardinal function in the emanation and conveyance of manmade airborne pollutants. The form of air pollution can be affected by diverse factors ( clime, local energy construction, and even populating manners of people ) in association with a assortment of combination among different beginning procedures. Populations populating in the megacities can be exposed more often to the risky air pollutants than those populating in the distant or rural countries. Harmonizing to the WHO, 4-8 % of deceases happening yearly in the universe are related to air pollution [ 1 ] Kathuria, 2002 V. Kathuria, Vehicular pollution control in Delhi, Transport Res. D-Tr E 7 ( 2002 ) , pp. 373-387. Article | PDF ( 203 K ) | View Record in Scopus | Cited By in Scopus ( 11 ) .

Polycyclic aromatic hydrocarbons ( PAHs ) are omnipresent organic pollutants that are formed from carbonous stuffs due to burning procedures at high temperature [ 2-4 ] and volatilization of uncombusted crude oil [ 5 ] . As PAHs are the most stable signifier of hydrocarbons happening in the signifier of complex mixtures, they can be present both in the gaseous and particulate stages in air [ 6 ] . Although natural beginnings ( such as forest fires and vents ) can lend to their atmospheric burden, the bulk of input is identified as anthropogenetic birthplace [ 7 ] . The United States Agency for Toxic Substances and Disease Registry ( ATSDR ) [ 8 ] put a sum of 17 PAHs on precedence list based on their toxicological profile ( 1995 ) . Note that some of these 17 members are classified as suspected carcinogens, while others are associated with ague and chronic wellness effects. Furthermore, transmutation of PAHs on atoms such as nitro-PAHs is more toxic than their parent PAHs [ 9 ] .

Enormous surveies conducted over the past three decennaries made PAHs identified as one of the most relentless toxic substances in cardinal and northeast Asia ( Region V11 ) based on the Stockholm convention [ 10 ] . As northeast Asia is the universe ‘s largest coal ingestion part [ 11 ] , PAH emanations and its eventful impacts are expected to be important. Sing that Seoul, Korea is one of the megacities in Northeast Asia with 10 million dwellers and 2.5 million vehicles, it is postulated to bring forth and let go of considerable sums of airborne pollutants including PAHs. In add-on, because of geographical location of South Korea ( in the locality of China ) , the long-range conveyance of airborne pollutants is besides anticipated to exercise big impacts on the regional PAH budget [ 12 ] .

A In this work, a comprehensive study on the ambient PAH degrees has been carried out from four urban residential locations in Seoul, Korea. The aims of this survey were ab initio set to at the same time measure the position of PAH pollution in multiple residential locations in a megacity. Then, the distribution and behaviour of PAHs in the ambient air were investigated farther to depict the basic belongingss of their beginning processes with regard to temporal and spacial standards selected in this survey.

2. Material and Methods

2.1.Field site and sampling

In this research, four trying sites Jong Ro ( JR ) , Gwang Jin ( GJ ) , Gang Seo ( GS ) , and Yang Jae ( YJ ) were selected to mensurate the PAH concentrations in ambient air in Seoul ( Fig. 1 ) . All of these trying sites represent air quality monitoring Stationss in residential countries where the basic air quality is monitored on a everyday footing. During the survey period, three single day-to-day samples were collected over 3 back-to-back yearss per month intervals to cover a period from February to July 2009. The aggregation of day-to-day PM samples started from 3 PM and ended by the same clip of the following twenty-four hours. Both atom and gas stage samples for PAH analysis were collected utilizing a high volume sampling station at a flow rate of 800 L min-1 ( HV-1000F, Sibata, Japan ) . The aggregation of entire suspended atoms ( TSP ) for particulate PAHs was made on a quartz filter. On the other manus, more volatile PAH constituents were taken by a glass cartridge which contained a 5-cm polyurethane froth ( PUF ) stopper, a 3 centimeter XAD-2 rosin, and a 2 centimeter PUF stopper. These PUF cartridges were so treated for consecutive extractions. During the sampling clip, the basic meteoric parametric quantities ( i.e. , including ambient temperature, comparative humidness, and wind speed/direction ) were recorded at the same time.

2.2.Chemical analysis for PAH

After concluding deliberation, all quartz filters and glass cartridges were placed individually in accelerated dissolver extractor ( Dionex 200 ) with Soxhlet extractors for extraction with methylene chloride. The infusion was so concentrated under a rotary evaporator, cleaned, and reconcentrated with ultrapure N to precisely 1 milliliter. For the analysis of PAHs, the gas chromatograph with MSD ( Agilent GC/MSD, model 7890A/5975C ) was employed. The separation of single PAHs shown in Table 1 was made by a capillary column ( DB-5MS, 30 m x 0.25 MM x 0.25 Aµm movie thickness ) . The mass selective sensor was operated in electron impact manner ( 70 electron volt ) . The chromatographic conditions were as follows: injector temperature, 2800C ; interface temperature 2900C ; and temperature plan ( 800C held for 5 min, 80-3000C at 60C min-1, 3000C for 5 min ) . The flow rate of bearer gas ( He ) was maintained at 1.5 mL min-1. Entire volume of 1 AµL was injected into GC/MSD with splitless manner. The analytical method was based on the US EPA Method TO-13 ( US EPA, 1999 ) .

A A The GC system was calibrated by known criterions of PAH mix ( 4s-8743, Supelco ( EPA 610 ) ) . Working criterions incorporating 17 mark analytes were prepared at three concentration degrees in a ( 50:50 ) methyl alcohol: methylene chloride solution. PAH working criterions prepared at each concentration degree were analyzed in triplicate. As portion of the basic quality confidence ( QA ) , field and laboratory space samples were analyzed. Blank samples ( including precleaned PUF stoppers and a quartz filter ) were prepared, treated, and analyzed in the same mode as the existent samples. Blank degrees of single compounds were usually really low and in most instances undetectable. The method sensing bounds ( MDL ) , if determined based on the instrumental sensing bounds for the PAH analysis, was in the scope of ~ & lt ; 1.0 pg m-3 ( 0.2 – 1.0 nanogram in absolute mass ) .

3. Consequences and treatment

3.1General features of PAHs

The aggregation of samples for the day-to-day measurings of ambient PAH degrees in air was made from four trying sites of JR, GJ, GS, and YJ in Seoul ( Fig. 1 ) . A sum-up of the environmental conditions measured at the same time for the whole survey period ( February to July 2009 ) is presented in Fig. 2. As our measurings of PAH were made to cover both particulate and gas stages, all informations were examined both as ( 1 ) single constituents of each ( or both ) stage: gas ( PAHg ) , atom ( PAHp ) , and gas plus atom ( PAHg+p ) and ( 2 ) amount of those single compounds: SPAHg, SPAHp, and SPAHg+p. A sum-up of the PAH is therefore derived for both two stages ( g and P ) and their combination ( g+p ) , as shown in Table 2.A The amount concentrations in the gas stage ( SPAHg ) at JR, GJ, GS, and YJ were computed as 10.4 A± 5.46, 8.89 A± 5.09, 12.0 A± 8.57, and 14.2 A± 15.2 ng m-3, severally. Their atom opposite numbers ( SPAHp ) were somewhat reduced but more variables with values of 8.63 A± 7.03, 8.79 A± 6.49, 10.2 A± 8.41, and 11.8 A± 11.5 ng m-3, severally. The concentrations of SPAHg+p measured were 19.0 A± 11.7 ( scope: 7.58 – 42.0 ) , 17.7 A± 11.0 ( 4.20 – 36.7 ) , 22.2 A± 16.5 ( 4.65 – 50.7 ) , and 25.9 A± 26.1 ng m-3 ( 3.54 – 88.5 ) , severally. Harmonizing to this comparing, the highest concentrations of all different PAH fractions were found systematically from YJ trying site ( Fig 3 ) . Examination of these informations at all four sites besides indicates that PHN was the most abundant species in the gas stage, whereas BBF, BAP and BGP were in the atom stage. If the consequences are compared for PAHg+p stage, PHN, FLT, and PYR were the most abundant species at all sites accounting for about 55 – 56 % of the all PAHs.

To meaningfully measure the position of PAH pollution in the survey country, our informations can be compared with those of other studies.A In a recent study made by our survey group [ 13 ] , we measured 7 heavy PAHs ( CHY, BAA, BBF, BKF, BAP, ICP, and DBA ) from 32 Stationss dispersed all across Korea ( Feb. 2006 to Jan. 2008 ) .A Despite the restriction in the selected mark compounds, that survey besides covered two residential ( Do Gok and Gu Ui ) and one commercial territory in Seoul ( Seoul train station ) out of all 32 Stationss [ 13 ] . If we compute the average concentrations of SPAHg+p for the corresponding 7 constituents in the present survey, these values ( 5.71 A± 0.51 ng m-3 ) are extremely comparable to those of 3 sites for the old survey ( 5.31 A± 6.30 ng m-3 ) . The consequences of the present survey can farther be compared with our recent study made inside the two traffic tunnels in Seoul [ 14 ] . The SPAHg+p information for the 16 precedence compounds ( 114.5 A± 9.21 ng m-3 ) , measured at two tunnel sites, were 4 – 5 times higher than the corresponding constituents in our mark residential sites. It therefore suggests that spacial gradients in PAH degrees can be developed in association with distance from the direct beginning activities ( e.g. , vehicles ) .

A To do a more meaningful rating of PAH informations, gas/particle ( G/P ) stage ratio of the single PAH compounds is besides assessed. The gas stage concentrations were below sensing bounds for most heavy PAHs ( 5-6 rings ) , while light PAHs ( e.g. , 2 – 3 pealing PAHs ) are abundant in the vapour stage due to a low boiling point and high volatility. As a consequence, depositions of light PAHs on atom surfaces occur less efficaciously comparative to heavy PAHs [ 15, 16 ] . However, as light PAHs are significantly enriched in gas stage, their part is more dominant in PAHg+p stage than heavy PAHs [ 17, 18 ] . Likewise, the comparative part of atom stage to the PAHg+p decreased with increasing volatility. Because of these alone belongingss, the partitioning form of PAH is extremely distinguishable between gas/particle stage in conformity with old studies [ 18-20 ] .A

The G/P ratios calculated at 4 sites differed greatly between visible radiation (& lt ;3 rings ) and heavy PAHs (& gt ;4 rings ) . Although the ratios for the former were 6.90 ( GJ ) to 10.3 ( JR ) , those of the latter varied in a much reduced scope of 1.60 ( GJ ) to 2.28 ( GS ) . As such, comparative laterality of PAH is greatly distinguished in relation to their molecular weights ( Fig 4 ) . The comparative ordination of PAH concentrations in all stages were reasonably consistent such as GJ & lt ; JR & lt ; GS & lt ; YJ site, with some exclusions. If the differences in the PAH degrees are checked by the pupil ‘s t-test, the laterality of YJ over other locations is important systematically in all stages ( P & lt ; 0.001 ) .

3.2.Temporal fluctuation in PAH concentration

If the temporal fluctuations of the PAH degrees in each stage are compared by their day-to-day values at the 4 survey sites ( Fig. 5 ) , the forms exhibit big similarities between different sites. Although the peak concentrations of PAH tend to happen in spring months ( either February or March ) , they decreased bit by bit until June at all sites. For illustration, at the YJ site, the values PAHg+p peaked in March with 51.9 and 36.6 ng m-3, severally, while their values in June experienced dramatic beads to 2.05 and 1.81 ng m-3, severally. Although the aggregation of TSP samples in this survey was confined to the limited periods of February through July, the consequences can be compared for seasonal differences over winter, spring, and summer. The seasonal forms of gas and atom stage are consistent plenty to enter the extremum in winter and lower limit in summer at all trying sites. In old surveies, the wintertime laterality of PAHs has normally been recognized in urban countries of Korea and Hong Kong [ 3, 21, 22 ] . If the winter/summer ratios are derived for each single PAH in atom stage ( PAHp ) , their average values tend to fall in the scope of 9.14 A± 5.61 ( JR ) , 7.55 A± 6.84 ( GJ ) , 11.3 A± 9.17 ( GS ) , and 11.4 A± 7.37 ( YJ ) . The PAHp ratios of 1 to 48 rich persons besides been reported for samples collected in Hong Kong [ 22 ] . In contrast, the winter/summer ratios for PAHg+p were 7.64 ( JR ) , 6.48 ( GJ ) , 9.86 ( GS ) , and 12.5 ( YJ ) . These ratios appear to be extremely comparable to those reported antecedently in Europe and in USA where PAHp or PAHg+p were by and large higher in winter by a factor of 1.5-10 than in summer [ 23-26 ] . Likewise, such ratios for PAHg+p were determined as 7.5 and 8.6 at two sites in the metropolis of Hong Kong [ 22 ] .

3.3.Appraisal of PAH beginnings

PAHs are relentless and toxic substances produced by a assortment of burning beginnings. Although half lives of these compounds vary in the ambiance [ 27, 28 ] , their atmospheric profiles are by and big affected by such meteoric parametric quantities as UV visible radiation and temperature [ 29 ] . Because of alone fractional processs between PAHs, their concentration informations are frequently used as a fingerprint of their emanation beginnings [ 30, 31 ] . The concentrations of several marker compounds and their ratios can hence supply some penetrations into the comparative function of different PAH beginning processes [ 32, 33 ] . The calculation of the PAH ratios, particularly between different responsivenesss is extremely utile to measure non merely their source/sink procedures but besides the ripening of the air mass [ 34-36 ] .

In this research, the ratios of BAA/CHY, BAA/BAP, BAP/BGP, and FLT/ ( FLT+PYR ) were calculated for both warming ( winter ) and non-heating periods ( spring and summer ) . The findings of higher PAHg+p ratio in BAA/CHY and BAA/BAP indicate comparatively small consequence of photochemical processing ( of the air mass ) but of import parts from local beginnings. On the other manus, their reduced ratios are likely to reflect the aging consequence on PAH distribution [ 36 ] . Lohmann et Al. [ 34 ] stated that BAA/CHY ratio above 0.40 should reflect newly emitted pollution. In this survey, BAA/CHY and BAA/BAP ratios in PAHg+p are high during heating season ( 1.46 and 1.20, severally ) than non-heating season ( 0.88 and 0.96, severally ) . Comparison of these ratio values therefore confirms that air multitudes sampled during the non-heating season should be more fresh than their opposite numbers. In our survey, the ratio values for BAA/CHY were variable plenty to bespeak pyrolytic input ( & gt ; 0.90 ) during the winter season [ 37 ] and the usage of gasolene ( 0.28 – 1.20 ) during the non-heating season [ 2, 38 ] . Furthermore, Li and Kamens [ 31 ] observed that the ratio of BAA/BAP for gasolene fumes was 0.5, while those of Diesel and wood burning were 1.0. In this work, BAA/BAP ratio for heating season ( 1.16 ( GS ) to1.20 ( YJ ) ) is much higher than non-heating season ( 0.85 ( GS ) to 0.96 ( YJ ) ) . These observations therefore systematically suggest the comparative laterality of Diesel and wood burning as beginning signature of the survey countries. Comparison of these ratios among all 4 sites indicates that YJ site maintained the highest ratios ( BAA/BAP and BAA/CHY ) of all sites, irrespective of seasons.

The differences in BGP/BAP ratio between non-heating ( 1.03 – 1.35 ) and heating season ( 0.82 – 0.98 ) in our survey sites can besides be interpreted to stress the major function of route dust as their beginning processes [ 39 ] . The ratio of FLT/ ( FLT+PYR ) was besides used as an index of burning beginnings [ 40 ] , uncomplete burning of coal and crude oil [ 41 ] , and gasolene engines [ 42 ] . Their ratios were 0.4 for gasolene engines [ 2, 42 ] , while & gt ; 0.5 for Diesel engines [ 2, 43, 44 ] . As these ratios for 4 sites in our survey fell in the scope of 0.55 to 0.58, it besides suggests more effectual function of Diesel engines. The consequences of this diagnostic analysis are by and large co-occuring with the comparative laterality of Diesel beginning signature for PAH. In add-on, it is besides found that YJ site is affected by more complicated beginning procedures than others.

3.4.Factors impacting the environmental behaviour of PAH in air

Under the existent universe conditions, emanations from vehicles do non wholly represent homogeneous burning of fossil fuels, as they besides release unburned fuel and pyrolysis of simple hydrocarbons and additives [ 29 ] . Sing the complicated nature of PAH beginning processes, a correlativity analysis was conducted to better history for the factors and processes commanding the behaviour of PAHs in the residential locations investigated in this survey. The presence of important correlativities was foremost found between standards pollutants measured at the same time with PAH such as between SO2 and NO2 ( P & lt ; 0.01 for all four sites ) or between SO2 and CO ( P & lt ; 0.01 at JR and YJ ) . The comparative copiousness of strongly correlated brace among SO2, NO2, and CO informations suggests that these pollutants should hold been affected likewise by beginning procedures of each country [ 45 ] .A

If the PAH informations are compared with those environmental parametric quantities, they tend to exhibit most important correlativities with SO2. For case, at GJ site, the compatibility with SO2 is found at P values less than 0.01 ( CHY, BBF, and ICP ) or 0.05 ( FLT and PYR ) . At the JR and GS site, SO2 is besides strongly correlated with such constituent as: BBF or ICP ( P & lt ; 0.05 ) . In contrast, the consequences at YJ do non exhibit such strong correlativities with SO2. This difference in correlativity forms between sites ( YJ vs. all the others ) should be closely associated with those observed from such attacks as diagnostic ratios. Similarly to the instance of SO2, a high correlativity of the particulate PAH constituents has besides been observed from such pollutant as CO in many types of wayside sites [ 46, 47 ] . In conformity with such findings, PAH information measured at the GS site showed reasonably strong correlativities with CO ( P & lt ; 0.01 and p & lt ; 0.05 ) . Such relationship was besides found at the YJ site, with BBF ( P & lt ; 0.05 ) or ICP ( P & lt ; 0.01 ) . In contrast, correlativities were non important plenty between those parametric quantities at GJ site.

A In Table 3, the consequences of correlativity analysis are organized to distinguish the comparative copiousness of strongly correlated instances. To let the comparing between different fiting braces, the consequences were randomly classified into three classs, i.e. , group I ( the least important instances ( p = 0.05 ) , II ( P & lt ; 0.05 ) , and III ( P & lt ; 0.01 ) . Harmonizing to this categorization strategy, the frequence of significantly correlated brace was greatly distinguished on the order of: ( 1 ) YJ: 129 instances ( III ) and 7 instances ( II ) , ( 2 ) Junior: 125 ( III ) and 6 ( II ) instances, ( 3 ) Gram: 118 ( III ) and 11 ( II ) instances, and ( 4 ) GJ: 122 ( III ) and 4 ( II ) instances.

To further depict the likely beginnings of the atmospheric pollutants, chief constituent analysis ( PCA ) was applied to the PAH and relevant parametric quantities [ 3, 48, 49 ] . As the concentrations of PAHs can be affected greatly by their beginning belongingss, the PAHg+p informations were capable to factor analysis along with all the relevant parametric quantities ( 12 standards pollutants, 16 metal species, and 9 ionic species ) . The consequences are so classified by such standard as characteristic root of a square matrixs & gt ; 1 and discussed below harmonizing to the basic information of single beginning profiles.

The consequence of vehicular emanations can be assessed by such constituents as SO2, NO2, CO, and TSP [ 50, 51 ] . Likewise, mixture of gasolene and Diesel emanations can be represented by such PAH constituents as ACL, FLT, PYR, CHY, BKF, BBF, PYR, BAP, and BGP [ 2, 23, 52-54 ] . Factors 1 and 2 at three Stationss ( JR, GJ, and GS ) or factors 1 and 4 at YJ appear to be represented by the above beginning constituents. Many metals ( Zn, Cu, Cd, Mn, Fe, Cr, and Pb ) and ionic species ( NO3- , SO42- , Cl- , Na+ , and Ca2+ ) originate from resuspended route dust or oil combustion/road traffic activities [ 53, 55-58 ] . On the other manus, a group of ionic species including ( NO3- , SO42- , and NH4+ ) is representative of secondary aerosol [ 59 ] . Hence, high burdens in factor 1 at three sites ( JR, GJ, and GS ) and factor 2 ( at YJ ) should be affected by route dust ( as their beginnings ) . Factor 3 of YJ site with high burdens of NO3- , SO42- , and NH4+ along with Ca2+ besides suggest the of import function of secondary aerosol.

A As coal combustion releases PAHs, a figure of PAH species ( such as ICP, DBA, BGP, FLT, FLR, BBF, and BKF ) can be designated as the marker species for such procedures [ 60-62 ] . Likewise, some ionic and metallic constituents ( e.g. , F- , Cl- and As ) are besides reported as tracers of coal burning [ 53, 59, 63 ] . As seen in factors 2 ( JR and GS ) and 3 ( GJ ) or factors 1 and 5 ( YJ ) , PAH emanations appear to be affected by coal combustion processes. It is besides acknowledged that Ni and V are chiefly emitted from oil burning [ 25, 53 ] . Banerjee [ 64 ] and Karar et Al. [ 65 ] reported that the presence of Zn in ambient air is associated with wear and tear of gum elastic tyres or lubricating oil. As is factor 4 at JR site ( high burden of Ni ) , oil burning can besides function as the powerful beginning of PAH ( factor 6 at YJ site ) .

4. Decision

In order to measure the degree of PAH pollution from 4 urban residential locations in Seoul, TSP samples were collected daily for 3 back-to-back yearss per month footing from February to July 2009. The consequences of our survey have been analyzed to place the factors and procedures impacting PAH behaviour in the ambient air in the urban residential countries in Seoul, Korea. The PAH concentrations in gas plus atom stage ( PAHg+p ) averaged 19.0 ( JR ) , 17.7 ( GJ ) , 22.2 ( GS ) , and 25.9 ng m-3 ( YJ ) . Harmonizing to the analysis of seasonal forms of these PAH informations, extremely consistent tendency was observed from all sites with the extremum values during winter. Comparison of fractional process form besides indicated that PHN was the most abundant species in the gas stage, whereas BBF, BAP, and BGP were in their atom opposite number. As it was seen from the average PAH concentrations in each stage, the winter/summer ratios of single ( or the amount ) PAH constituents were the highest at YJ. The YJ site was besides distinguished from others because of its alone diagnostic ratios between different PAHs. The being of the alone tendency at YJ site may be attributed, at least partly to the out-of-door incinerations in add-on to the traffic activities at this specific site.

Harmonizing to the consequences of PCA, the beginnings of PAH in all 4 urban sites should be dominated by diverse beginning processes including vehicular emanations ( mixture of Diesel and gasolene ) , secondary aerosol, resuspended route dust, coal burning, and open-field incinerations. In line with grounds collected in this survey, the urban ambiance can be capable to the overpowering influence of PAH pollution. To let more elaborate analysis on the consequence of diverse beginning procedures and their impacts, one may necessitate to go on attempts to depict the possible functions of such procedures on the distribution of PAH and to better their direction strategy.

Recognition

This work was supported by the National Research Foundation of Korea ( NRF ) grant funded by the Ministry of Education, Science and Technology ( MEST ) ( No. 2009-0093848 ) .

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