Assessment of airborne particulate levels in Spain in relation to the new EU-directive

PERGAMON Atmospheric Environment 35 Supplement No. 1 (2001) $43-$53

ATMOSPHERIC ENVIRONMENT

www.elsevier.com/locate/atmosenv

Assessment of airborne particulate levels in Spain in relation to the new EU-directive

Begofia Artifiano a'*, Xavier Querol b, Pedro Salvador a, Sergio Rodriguez b, Diana G. Alonso a, Andrrs Alastuey b

~Environment Department, CIEMAT, Avda. Complutense 22, E-28040 Madrid, Spain blnstitute of Earth Sciences "'Jaume Almera", (CSIC) el Lluis Solb y Sabaris sin 08028 Barcelona, Spain

Received 3 May 2000; received in revised form 10 July 2000; accepted 28 September 2000

Abstract

This study deals with PM10 levels obtained at several Spanish air quality monitoring urban, industrial and rural stations. Comparison with current national regulations on airborne concentrations of particulate matter showed that the standard limits are never exceeded in the selected areas. However, the limit values proposed in both stages of the recently approved European directive would be exceeded in the current situation. Seasonal distribution of exceedences shows a variety of patterns suggesting different contributions from anthropogenic and natural sources. PM 1 o levels were found to be affected by natural sources of a non-local origin or even attributed to long-range transport processes from arid or desert zones. © 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Air quality; Atmospheric particles; PMlo; Air quality networks; Natural particles sources

1. Introduction

The implementation of the recently approved Euro- pean (EU) directive on air quality (99/30/CE) will require an evaluation of the ambient levels of a number of pollutants by the member states. As regards the particulate matter, the Spanish standard for total suspended particles (TSP, Table 1) will be replaced by the new EU directive which demands the measurement of the fraction lower than 10 gm (PM10). Nevertheless, given the adverse ef- fects on health of this finer fraction (US-EPA, 1996), PM~o levels have been measured by some of the ambient air quality monitoring networks in Spain in recent years.

Although the new limits will be in force by 2010 and will be implemented in two stages (Table 1), our data suggest that these limits will not be met. A research project on the source apportionment PMIo/PM2.5 analysis in different areas of Spain is currently in progress. Preliminary results of the analysis of the 1995-1998

PMlo time series, with special emphasis on the events exceeding the daily limit values at different urban, industrial and rural sites in Eastern and Central Spain are presented in this study. Examples of the characterisation of high PMlo events in 1999 are also given.

Source apportionment studies to discriminate primary/ secondary and natural/anthropogenic origins of particles are time consuming and expensive. They involve size distribution measurements and chemical characterisation over a long period of time, But these studies could become more relevant given that natural particle sources (such as the long-range transport of Saharan dust) account for a number of high PMIo events in some parts of Spain (Querol et al., 1999a, b). However, in the absence of chemical data, the seasonal analysis of maximum distribution of PMlo levels and limit value exceedence patterns could shed some light on the major sources contributing to ambient air particulate levels.

2. Methodology

* Corresponding author. E-mail address: [email protected] (B. Artifiano).

The study is based on data supplied by selected PMlo monitoring stations in the following environments (see

1352-2310/01/$-see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S1 352-23 1 0 ( 0 0 ) 0 0 4 6 7 - 2

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Table 1 Limit values of the Spanish standard for ambient air particulate matter and new EU directive limit values and stages

Spanish standard

TSP annual limit value 150~tgm -3 TSP daily limit value 300 gg m- 3 (not to be exceeded more than 18 days yr- 1)

New EU directive

Stage I (to be achieved by January 2005) PMlo annual limit value PMlo daily limit value

Stage II (to be achieved by January 2010) PMI0 annual limit value PM10 daily limit value

40ggm 3 50 ggm 3 (not to be exceeded more than 35 days yr-1)

20ggm -3 50ggm 3 (not to be exceeded more than 7 daysyr -~)

N i 500 km

Monagrega 11~11~ ~rcel°na

~ / S t Andreu Madrid

(

~ P M ~ a measurement station

Fig. 1. Location of PMlo measurement stations selected for this study.

location in Fig. 1) in the period 1995-1998:

• Urban stations belonging to the Madrid Air Quality Monitoring Network.

• Industrial-urban stations in diverse areas of Catalonia (Igualada, Sant Andreu and Martorell), belonging to the Catalonia Air Quality Monitoring Network.

• Rural stations in Northeastern (Monagrega) and Southeastern (Carboneras) Spain belonging to the ENDESA (Empresa Nacional de Electricidad SA) monitoring network.

The ambient air quality in Madrid is controlled by an automatic network of monitoring, which is supervised by the Madrid City Council. This consists of 24 stations providing hourly data of the main atmospheric

pollutants such as ozone, nitrogen and sulphur oxides, carbon monoxide, hydrocarbons and particulate matter. The stations are distributed throughout the City in order to assess the atmospheric pollution in representative areas. They could all be regarded as typical urban traffic stations with the exception of one, located in a big park on the outskirts of Madrid, which could be considered as a sub-urban background station (# 24, Casa de Campo). In the urban traffic stations, the distance to the main roads ranges from 0.5 to 15 m, which suggests the predominant influence of local traffic on most of the pollutants. Given that Madrid has no significant industrial areas in its proximity, the main emission sources of atmospheric particles recorded by this network could be attributed to road traffic and domestic heating (during the cold season). The replacement of the TSP beta devices by new PMlo measurement systems was initiated by this network in 1990. The new systems currently operate at all the stations, supplying data continually. They are based on the Rupprecht and Patashnick tapered element oscillating microbalance (TEOM ®) method (Patashnick and Rupprecht, 1991). This device can provide hourly real-time data. A loss of particle mass could be produced by evaporation of semi-volatile compounds during filter collection owing to the heating of the air sample to remove particle-bound water. This underestimation will mainly affect the PMlo and PM2.5 fractions owing to the greater presence of semi-volatile material in the finer fractions. Ayers et al. (1999) quantified a loss of material of up to 30% in the TEOM PM2.5 measurements compared with gravimetric samplers, which are regarded as the reference method in the new EU directive. This effect could become important in urban areas like Madrid, where it is expected that this type of compound could account for a significant fraction of particulate matter. Actual concentration levels could, therefore, be slightly higher than those recorded at the monitoring stations.

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Nevertheless, as reported by Allen et al. (1997), the seasonal variability of this local effect should be assessed. In the Madrid area, a comparative study of the TEOM and the standardised (EN 12341, 1998) high volume sampler methods was carried out in August and September 1999. Both methods supplied very similar values as expected since the high temperatures recorded in Madrid during the summer months ( > 30°C) induced a low content of semi-volatile compounds in the particulate matter. A higher discrepancy is expected in the winter period given the lower temperatures.

The ambient air quality monitoring network of Catalonia is controlled in the same way as the one in Madrid. This network consists of 69 automatic stations providing hourly data of the main atmospheric pollutants. Initially beta attenuation instruments were used for TSP measurements. Subsequently, these instruments were complemented in 1993 with PMlo gravimetric measurements employing the standardised high-volume samplers. This PM ~ 0 manual monitoring was conducted on 2-3 moving days per week at 15 selected stations. For this reason, the time coverage of the PM~o data of these stations is considerably lower (45-65%) than that obtained at the stations in Madrid. Those stations with the best data coverage, were selected to study the PM ~ o time series. They were located in the industrial-urban areas of Igualada, Martorell and Sant Andreu. As in Madrid, the predominant influence of local traffic could be expected.

The Monagrega and Carboneras monitoring stations, belonging to ENDESA, are located near two power plants in rural areas. The Monagrega station is located in the field, isolated of populated areas. The closest villages are 10 km distant (a small village with < 3000 inhabit- ants). A similar situation can be described for Carbon- eras. Earlier studies have demonstrated that PM ~0 levels recorded at these monitoring stations are not significantly affected by the power plant emissions (Querol et al., 1998a, b). Therefore, these sites may be considered as representative of rural environments as regards PMlo levels.

These two monitoring stations have, since 1995, been equipped with automatic real time measurement instru- mentation of the main atmospheric pollutants. PM10 measurements are carried out with the TEOM system. A comparative study of this measurement and the standard gravimetric sampler at the Monagrega station showed that the microbalance method slightly under- estimated the measurements by 15% over a one-year period. However, as observed in Madrid, the measurements obtained by the two methods showed a good fit for the summer periods.

The 1995-1998 four-year period was selected for the limit values exceedences analysis. During this period, 18 out of 24 stations of the Madrid network measured PMlo. The year 1998 was not considered in this study since data availability was very low owing to significant

changes in the network management system. In Catalonia, the year 1995 was excluded given the low-data availability at the three stations selected. Finally, the PM~o time series recorded at the Monagrega and Car- boneras stations from 1996 to 1998 and from 1995 to 1998, respectively, were also selected taking into account their high-data availability.

The aforementioned stations are located in four very distinct areas in terms of climate, geography and emission features. The relative importance of the main emission source category will vary considerably from region to region. The natural sources, which should be included in any particle emission inventory, could also play an important role. Countries in the south of Europe located in the Mediterranean region, where natural processes can significantly affect the particle levels, should take these natural sources into consideration when performing an analysis of the normative compliance.

3. Results and discussion

3.1. Limit values exceedences

TSP limit values of the current Spanish standard were not exceeded at any of the selected stations, in Catalonia (DGQA, 1999) or in Madrid (Salvador and Artifiano, 2000).

Except for the Catalonia network, daily averages were obtained from PMlo hourly data with a minimum data capture of 90%, as required in the directive. The log- normal distribution provides a fairly good fit to the daily mean PM10 concentrations in almost all cases, (Fig. 2). This distribution has often been found to best describe particle concentrations in earlier studies, (Deacon et al., 1997) and is characterised by the geometric mean (GM) and the geometric standard deviation (GSD) which have been included in Table 2.

Annual arithmetic averages were obtained from the daily values for all the network stations to be compared to the EU directive limit values. In addition, the number of exceedences of the new daily limit value were estimated (Table 2). The results obtained show that the replacement of the current Spanish TSP limit values by the new PM 10 limit values would imply a dramatic change in the evaluation of the air quality in Madrid, Barcelona, Carboneras, and probably in most other rural, urban and industrial areas in Spain.

As regards the first stage considered by the directive (see Table 1), the 50ggm -3 PM10 daily limit value was exceeded more than 35 times yr -~ in the selected urban-industrial stations of Catalonia and approx, in half of the stations of Madrid during the three years (Table 2). Moreover, at some stations this value was exceeded in a systematic way more than 50% of the days during this period (Table 2 and Fig. 3a).

S46 B. Arti~ano et al. / Atmospheric Environment 35 Supplement No. I (2001) $43-$53

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This situation is fairly different from other European countries, where the number of exceedences only go beyond 35 times yr-~ at 20% of the stations or even less, depending on the year (DETR, 2000). In the Carboneras rural station the 50pgm -3 PM10 daily limit value was exceeded up to 48 days, in 1998. This site is located in one of the most extremely arid region of Spain, where high TSP annual means (93 + 39 pgm 3) have been reported in other experimental studies (Iranzo et al., 1994).

On the other hand, the Monagrega station did not exceed more than 7 days yr-1 this limit value (Table 2 and Fig. 3a).

The situation is slightly better as regards the annual limit value (40 Ixg m-3) since this limit was not exceeded at the Monagrega and Carboneras stations and was exceeded only at approx. 30% of the network stations in Madrid. However, this annual limit value was also exceeded at the selected stations in Catalonia (Fig. 3b).

As regards Stage II of the EU directive, the proposed annual and daily limit values would be exceeded at approx. 80% of the Madrid stations and at all the selected Catalan stations (Table 2 and Fig. 3a and b). Moreover, even at the Carboneras rural station, the PMlo levels would fail to meet the directive limit standards. Only Monagrega would be within the limit values of Stage II, although the annual mean PMlo value is fairly high for a rural station (16-18 pgm -3) when compared with the annual PMlo limit value of 20ggm -3.

This situation is reflected by the high particulate matter levels measured in the air quality networks in Madrid, Catalonia and in some rural Spanish locations. Thus, the PMlo annual network averages are approx. 32 gg m-3 in Madrid, 41 pgm -3 for the urban-industrial network of Catalonia (as reported by Querol et al., 199% for time series having >80% of time coverage data), and 18 and 30 pg m-3 for the rural sites of Monagrega and Carbon- eras, respectively (very close to and exceeding the annual limit imposed in the second stage of the directive).

3.2. Seasonal distribution o f PMlo limit values exceedences

The seasonal distribution of the number of exceedences of PMI0 levels over the daily limit value can provide useful information on the particle sources. The analysis of this time evolution for all the stations included in this study revealed three types of typical patterns. Fig. 4a and b show the relatively high number of daily exceedences at stations located in an arid rural environment in the South and East of Spain (Carboneras and Monagrega, respectively) in spring and summer. This is a typical rural pattern which could be related to the greater influence of natural processes during this period of the year, i.e. higher levels of soil-related particles due to strong convective conditions, lower aerosol scavenging potential (scarce rainfall episodes), and the higher influence of Saharan air masses intrusions.

Fig. 4c depicts the pattern of a typical urban station in Madrid with fall and winter maxima related to the major man-made emissions (road traffic exhausts and heating devices). This is the type of evolution which can be found in urban background stations in Northern and Central European cities (Monn et al., 1995 and Harrison et al., 1999). However, the seasonal pattern of exceedences shown by most of the Catalan stations (see example in Fig. 4d) does not follow this typical urban-industrial trend. Thus, maximal PM~o exceedence events occur in spring and autumn although summer and winter exceedences are also significant. A large number of the

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Fig. 3. Number of the PMlo daily limit value exceedences (a), and PMlo annual average concentration values (b), obtained for the Madrid, Catalonia and ENDESA monitoring stations from 1995 to 1998. The two horizontal solid lines in the figures show the limit values in each stage of the EU directive. IGU, Igualada; MAR, Martorell, SAN, Sant Andreu, MON, Monagrega, CAR, Carboneras.

autumn, spring and summer exceedences are probably due to external and/or natural particulate inputs.

3.3. Seasonal time-series evolution of daily levels o f PMlo and gaseous pollutants

Although the time distribution of the main daily peaks recorded in Madrid varies from station to station and during the year probably because of local factors, some periods can be identified as typical fall and winter pollution episodes (Fig. 5a). In these cases, stagnant atmospheric conditions associated with high-pressure systems over the centre of the Iberian Peninsula favour the accumulation of pollutants in the Madrid area, and the devel- opment of pollution episodes (Artifiano et al., 1994). These episodes can last up to 10 days and are detected at all the network stations.

The preliminary analysis of the Madrid PMao levels revealed that most of the daily PMlo peaks which result in exceedences of limit values are well correlated with an increase in the NOx levels, which can give rise to secondary particles through gas-to-particle conversion processes. This suggests that, in this case, local traffic is the main source of PMlo.

The urban-industrial stations of Catalonia also regis- tered high particulate winter events showing a good correlation with the increase in locally emitted air pollutants, mostly NOx and SO2 (Fig. 5b), which point to local traffic and industrial emissions as the major sources of the particulate matter.

However, winter PMlo levels recorded at the rural stations of Monagrega and Carboneras were significantly low in contrast to the winter PM10 peaks observed at urban and industrial sites in Madrid and Catalonia. High

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the i n d u s t r i a l - u r b a n s t a t ion o f I g u a l a d a , (Ca t a lon i a ) (b), a n d the r u r a l C a r b o n e r a s (c). ( F o r these f igures the T S P ins t ead of the P M l o

series f r o m I g u a l a d a h a v e been used, in o r d e r to get a m o r e r ep re sen t a t i ve t ime series. At th is p l ace T S P series h a v e a h ighe r c o v e r a g e of

da i ly da t a . The r e a s o n has been p o i n t e d o u t in the m e t h o d o l o g y section.)

$50 B. Artf~ano et al. / Atmospheric Environment 35 Supplement No, 1 (2001) $43-$53

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PMlo periods with exceedences of the limit values were recorded at these rural stations in spring and summer, simultaneously with low NOx and SO2 records (Fig. 5c).

Moreover, high PMlo events have been simultaneously recorded in Catalonia and Madrid during spring and summer. This is clearly shown in Fig. 5a and b for July 1995. In these cases, the low correlation with the levels of local gaseous pollutants suggests the added apportionment of a non-local source. Examples of these situations are given in Fig. 6. These events have been simultaneously recorded at rural stations more than 300km from Madrid and Barcelona (Fig. 6 upper) The parallel PMlo evolution recorded in July 1996 in these distant areas may be attributed to common meteorological conditions favouring the accumulation of particles in the atmosphere (high photochemical conversion rate, low rainfall and high convective dynamics favouring re-suspension processes). A detailed meteorological analysis indicates that most of these events coincide with

long-range transport of air masses from the Sahara over the Iberian Peninsula. In the example shown in Fig. 6 bottom, the Saharan intrusion is favoured by the presence of a high-pressure system over Northern Africa. The air mass back-trajectory study using the HY-SPL1T model (Draxler, 1994) supports this conclusion. More- over, the strong summer convective conditions induce a thick mixing layer (up to 3000m in Madrid, Crespi et al., 1995), allowing the load of Saharan particles from the higher atmospheric layers to reach the topographic surface. The inputs and methodology used to run the HY-SPLIT model can be found in Querol et al. (1998a), who have successfully used this tool to document the impact of the Saharan intrusions on ambient PMt0 time series. Thus, they demonstrated that these processes account for the major variations on daily PMa0 levels in Eastern Spain in summer and spring.

The long-range transport of Saharan dust has been documented in a number of studies not only in the Mediterranean area (Martin et al., 1990; Dayan et al.,

B. Arti~ano et al. /Atmospheric Environment 35 Supplement No. 1 (2001) $43-$53 $51

1991; Kubilay and Saydam, 1995), but also at northern- most latitudes (Reiff et al., 1986; Prospero and Nees, 1987; Gatz and Prospero, 1996). Climatological factors determine the time of the year most favourable for this atmospheric dynamics process (Kubilay et al., 2000). Sat- ellite climatology points at summer as the season when, more probably, dust transport takes place towards the western Mediterranean (Martin et al., 1998). Although the classical climatology of the Mediterranean in summer shows a fairly simple scheme for the surface pressure field (Meteorological Office, 1962), meso-meteorological processes governs the atmospheric dynamics of this area giving rise to a complex mosaic of atmospheric circula- tions with marked daily cycles, as Millgn et al. (1997) describe. After their description, at this time of the year, thermal-origin low-pressure systems form over the Iberian Peninsula and North of Africa. A compensatory loop of high pressures extends over the western Mediter- ranean area, favouring air mass trajectories from the Sahara desert towards the Eastern part of Spain. Anti- cyclones located over the North African coast (Algeria) and Middle Mediterranean reinforces this type of trajectories. The experimental data presented in this work confirm the incidence of the Saharan dust transport on the PMlo levels recorded in the eastern and central part of the Iberian Peninsula during the summer months. There are also evidences of some events which have been observed in spring an autumn.

Fig. 7 shows another example of the exceedence of PMlo limit values due to Saharan air mass transport, which occurred between 9 and 11 March 1999. The dust-enriched air masses contributed largely to the increase in the PMlo levels at different sites in Eastern Spain (Monagrega and Barcelona) (Fig. 7 upper left). This high dust load coupled with a minor local particulate contribution gave rise to high TSP and PM10 ambient levels in Barcelona. The Saharan origin was confirmed by the chemical characterisation of PMlo given the high levels of Ca, A1, Si and other crustal/ mineral elements. It was also observed that the mineral fraction apportionment was higher for PM10 (52%) than for PM2.5 (21%) during 10 March 1999, as shown in Fig. 7 (upper right). PM10/PM2.s monitoring under high Sahara dust events shows that monitoring of PM~.5 instead of PMt0 may avoid the interference of crustal particles without a major reduction in the secondary anthropogenic load, with the exception of nitrate. How- ever, the PM2.s measurement is not an adequate methodology for monitoring the impact of primary particulate emissions such as ceramic, mining or cement emissions on air quality since major ambient air particles derived emissions are mainly in the range of 2.5-10 gm.

The back-trajectory analyses confirm the air mass path crossing the Northern Africa region and arriving in Barcelona 10-11 March 1999 (Fig. 7, bottom).

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25 " a -20 -10 0 10 20

Fig. 7. PM10 daily values at Monagrega and Barcelona City recorded from 4 to 14 March 1999, (upper left). Source apportionment analysis for PM, 0 and PM2.5. It includes the organic and elemental carbon (OC + EC), the main ions that are related to the secondary produced particles and the marine and mineral originated particles content, (upper right). Back trajectories from Barcelona obtained for the period 10-11 March 1999. Endpoint levels have been taken at 900, 850 and 700hPa, (bottom).

$52 B. Arti~ano et al. / Atmospheric Environment 35 Supplement No. 1 (2001) $43-$53

The anthropogenic emissions and the Saharan intrusions are, however, not the sole cause of the higher PM~o levels recorded (even at rural sites) in the Mediterranean basin when compared with regions in Northern and Central Europe. Other possible contr ibutory causes whose relative importance should be evaluated are:

• An atmospheric particulate reservoir effect (Querol et al., 1999a) induced by a scarce renovation of the atmospheric masses in the Western Mediterranean basin (Mill/tn et al., 1997).

• The lower rainfall rate in the Mediterranean reduces the particulate scavenging potential and enhances the reservoir effect.

• The high photochemical conversion rate could account for a higher production of secondary particles from gaseous precursors in the Mediterranean area.

• The occurrence of poor soil profiles covering extensive areas of Eastern, Southern and Central Spain accounts for high crustal particulate emissions.

• The high convective dynamics accounts for an inten- sive crustal particulate re-suspension.

4. Conclusions

As result of this preliminary study carried out on some urban, industrial and rural stations of Spain, the new EU directive on PM10 limits will hardly be met in some areas. Moreover, in some urban or industrial stations the limits can be exceeded in a systematic way. Even at rural areas, there are exceedences of the daily limit value and the annual mean also exceeds or is very close to the annual limit value.

Seasonal analysis shows that natural sources can significantly affect the particle levels, mainly in summer and spring. Climatology (strong radiation, high photochemical conversion rates, low rainfall rate), and soil features, common in other South European and Mediterranean countries, can contribute to enhance the particle input. Long-range transport of Saharan dust has been demonstrated to affect largely the PM10 levels, although not the PM2. 5 fraction, in areas of the Iberian Peninsula. These factors should be taken into consideration when the European normative compliance is evaluated.

Acknowledgements

The authors would like to thank the Madrid City Council, the Generalitat de Catalunya Department of Environment Quality and ENDESA for providing the whole data series from the Air Quality Networks. This study forms part of a larger project funded by Spanish Commission CICYT (Ref: AMB98-1044), the Ministry of the Environment and by the Madrid Communi ty under reference 07M/0014/1998.

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Assessment of airborne particulate levels in Spain in relation to the new EU-directive

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