(g hi)pe ry le ne in den o(123-cd. )p yrene dibenz. (a h+ a c)anthrace ne. P ... EMEP Status Report 3/08 "Persistent Organic Pollutants in the Environment" Joint ...
PAHs IN AIR IN VIROLAHTI, FINLAND, IN 2007-2008. SEASONAL VARIATION AND SOURCE APPORTIONMENT
M.VESTENIUS, S. LEPPÄNEN, P. ANTTILA, K. KYLLÖNEN, H.HELLEN AND H. HAKOLA Finnish Meteorological Institute, P.O. BOX 503, FI-00101 HELSINKI, FINLAND
Keywords: PAH, PM10, PMF, AIR QUALITY INTRODUCTION Polycyclic aromatic hydrocarbons (PAH-compounds) are particularly harmful compounds due to their carcinogenic effect on humans. PAH-compounds are formed during incomplete burning of organic material and are emitted into the atmosphere from several natural and anthropogenic emission sources. Natural sources include emissions from volcanic activities and forest fires, whereas anthropogenic sources consist of fossil fuel and biomass burning. (Ravindra et al., 2008). Wood combustion, especially in residential warming is a significant PAH-source in the Northern Europe (Hellen et al., 2008). Long-range transport has also a remarkable effect on air quality in the Nordic countries. In this study, PAH-compounds from particulate matter in air (PM10 samples) were collected at the Virolahti background station located in the south-eastern Finland, near the Russian border. Positive matrix factorization (PMF) –analysis (Paatero et. al., 1997) was applied to the PAH-dataset combined with heavy metals and other pollutants and also with wind direction in order to separate different pollution sources and source areas that have an effect on local air quality in Virolahti. METHODS Daily PM10-samples were collected with a low volume sampler (38 l min-1) on teflon filters. Filter samples were extracted into dichloromethane using soxhlet extraction. Concentrated samples were purified using solid phase extraction and analyzed using gas chromatograph with mass selective detector. 11 of the 16 EPA priority PAH pollutants (phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene/triphenylene, benzo(k+b+j)fluoranthene, benzo(a)pyrene, benzo(ghi)perylene, indeno(123-cd)pyrene and dibenz(ah+ac)anthracene) were analyzed from filter extracts. Daily sample dataset covers approximately two months of sampling from the beginning of January, and two one-week sampling periods in August and October 2007. The weekly sample dataset covers sampling from January 2007 to the end of November 2008.PAH datasets were compared to trace elements and inorganic ion data from same place and time.
RESULTS AND DISCUSSION Figure 1 shows the weekly mean concentrations of PAH compounds in PM 10 fraction together with temperature. Average concentrations of PAH compounds in PM10-fraction are highest in winter due to higher emissions and slower sink reactions then. PAH concentrations in PM 10 are approximately inversely proportional to outdoor temperature. Clear annual variations of concentrations can be seen. Weekly
concentrations of benzo(a)pyrene and PAHs in Virolahti during this measuring period varied between from 0.03 to 1.7 and 0.5 to 25 ng/m3, respectively. 30
benzo(a)pyrene total_PAH 20
Temp/ o C
0 1/0 7 4/0 7 1 0 /0 7 1 2 /0 7 1 4 /0 7 1 6 /0 7 1 8 /0 7 2 0 /0 7 2 2 /0 7 2 4 /0 7 2 6 /0 7 2 8 /0 7 3 0 /0 7 3 2 /0 7 3 4 /0 7 3 6 /0 7 3 8 /0 7 4 0 /0 7 4 2 /0 7 4 4 /0 7 4 6 /0 7 4 9 /0 7 5 1 /0 7 1/0 8 3/0 8 5/0 8 7/0 8 9/0 8 1 1 /0 8 1 3/0 8 1 5/0 8 1 7/0 8 1 9/0 8 2 1/0 8 2 3/0 8 2 5/0 8 2 7/0 8 2 9/0 8 3 1/0 8 3 3/0 8 3 5/0 8 3 7/0 8 3 9/0 8
week of year
Figure 1. Weekly averages of total PAH and benzo(a)pyrene (BaP) concentrations [ng/m3] in PM10and daily mean temperatures in Virolahti, between January 2007 and September 2008 In the daily dataset, total PAH and B(a)P concentrations showed strong positive correlations with PM 2.5 mass, NOx and SO2 (Table 1), but correlation with the wood combustion marker, potassium, was weak. Because ozone removal was not used during sampling, oxidation of particulate PAHs by ozone is one of the major artifacts in this study. A strong negative correlation between ozone and PAH could be a signal of that kind of interference. Total PAH and benzo(a)pyrene show higher negative correlations with temperature than with ozone. Covariations between total PAH and some other combustion-derived species are also seen in Fig.2.
Table 1. Total PAH and Benzo(a)Pyrene (BaP) Pearson correlation against selected components in the daily data. Correlation PM2.5 Total-PAH 0.72 B(a)P 0.68
PM10 0.08 0.11
NO2 0.69 0.73
SO2 0.75 0.73
K+ 0.28 0.25
O3 -0.15 -0.21
temp -0.47 -0.48
60.00 PAH-SUM SO2 NO2 SO4-- ug(S)/m3
c[PAH] / ngm
0.00 DATE 1/1/2007 1/2/2007 1/3/2007 1/4/2007 1/5/2007 1/6/2007 1/9/2007 1/10/2007 1/11/2007 1/12/2007 1/13/2007 1/14/2007 1/21/2007 1/22/2007 1/23/2007 1/24/2007 1/25/2007 1/26/2007 1/27/2007 1/28/2007 1/29/2007 1/30/2007 1/31/2007 2/1/2007 2/2/2007 2/3/2007 2/4/2007 2/13/2007 2/14/2007 2/15/2007 2/16/2007 2/17/2007 2/18/2007 2/26/2007 2/27/2007 2/28/2007 3/1/2007 3/2/2007 3/3/2007 3/4/2007 8/13/2007 8/14/2007 8/15/2007 8/16/2007 8/17/2007 8/18/2007 8/19/2007 10/15/2007 10/16/2007 10/17/2007
Figure 2. Time series of total PAH, SO2, SO4 and NO2 in the daily dataset. Notice that time scale is not continuous.
PMF ANALYSIS PMF analysis of daily data found three factors that can be identified as western factor (F1), northern factor (F2) and eastern factor (F3). These factors are shown in Fig. 3. In factor 1, air masses came from western half of the sector circle (180-360 degrees). Most of calcium, chloride, sodium, magnesium and half of potassium are seen in this factor, which indicates ground dust and sea salt. Factor 1 also contains most of ozone, 44% of the fresh traffic pollution (NO) and 30% of oxidized traffic pollution (NO 2), but almost no PAHs at all. Of the PAHs, dibenzo(a,h)anthracene behaves slightly differently; 30% of it can be seen in this factor. This factor consists of domestic pollution from Finland as well as marine and long range transport (LRT) of continental air masses from southern and western Europe. This wind direction was most frequent, 67% of the days entered this factor. Factor 2 came from north-east. F2 contains, like F1, no remarkable PAH or other pollution and it can be classified as a clean factor. However, one third of SO2 enters this factor which indicates some SO2 source in this direction. Only 10% of the days belonged to this factor. Most of the PAHs (85%), as well as more than half of the LRT sulphate and nitrate particles and SO2 and NO2, enter in the factor 3. This factor came from the sector 45º-180º thus including St Petersburg area. This wind direction was reasonably rare (23% of days), but still makes a significant contribution to the pollutant concentrations.
c[NO2,SO2,SO4] / ugm
100 90 80
% of species
70 60 F1 50
40 30 20
phenantrene anthracene fluoranthene pyrene benz(a)anthracene chrycene/triphenylene benzo(k+b+j)fluoranthene benzo(a)pyrene benzo(ghi)perylene indeno(123-cd)pyrene dibenz(ah+ac)anthracene PAH-SUM Ca++ ug/m3 Cl- ug/m3 HNO3_NO3- ug(N)/m3 K+ ug/m3 Mg++ ug/m3 Na+ ug/m3 NH3_NH4+ ug(N)/m3 SO4-- ug(S)/m3 SO2 NO2 NO O3 TGM Day_Coarse ug/m3 Day_Fine ug/m3 rain/mm m_temp-Norm S0-45 S45-90 S90-135 S135-180 S180-225 S225-270 S270-315 S315-360 Days
Figure 3. Three-factor PMF analysis of the daily dataset.
During week, wind direction normally varies significantly. Therefore, wind factorization is unusable within weekly dataset. Because of that, three factor PMF analysis of weekly data was made without wind component and similarities with the daily dataset were found. In weekly dataset, practically all PAHs, except part of dibenzo(a,h)anthracene, came out in one factor with part of cadmium, lead and zinc, which indicates industrial pollution.
SUMMARY PAH samples from PM10 were collected at Virolahti, Finland. Two PAH datasets were analyzed. Daily dataset covers approximately two months data at wintertime and two one-week sampling periods in August and October. Weekly data covers time period from January 2007 to September 2008. The source areas of daily PAH concentrations together with a set of inorganic ions as well as gases and also wind direction were analyzed with PMF. Temporal examination of data showed strong seasonal variation for PAHs. Analysis of daily dataset identified three factors, which could be related to western, northern and eastern wind directions. Within these factors, several pollution sources could be identified. According to the PMF analysis used for daily dataset, most (about 80%) of the PAHs in Virolahti during the study period came from sector 45-180 degrees, which includes among other transboundary areas the metropol of St. Petersburg at the distance of 160 km. Marks of biomass burning, traffic and industrial pollution, as well as long range transport can be seen as well.
ACKNOWLEDGEMENTS The financial support by the Academy of Finland Centre of Excellence program (project no 1118615) is gratefully acknowledged.
REFERENCES Ravindra, K., Sokhi, R., Van Grieken, R. (2008). Review: Atmospheric polycyclic aromatic hydrocarbons: Source attribution, emission factors and regulation, Atmospheric Environment 42, p.2895-2921. Hellen, H., Hakola, H., Haaparanta, S., Pietarila, S. and Kauhaniemi, M. (2008). Influence of residential wood combustion on local air quality, Science of the total environment 393, p.283-290. EMEP Status Report 3/08 "Persistent Organic Pollutants in the Environment" Joint MSC-E & CCC Report. Paatero, P. (1997). Least square formulation of robust non-negative factor analysis, Chemometrics and Intelligent Laboratory Systems, 37, p. 23-35.