Heavy Metal Distribution in the Area of Thessaloniki, Greece Th. Kouimtzis

Heavy metal distribution in the area of

Thessaloniki, Greece

Th. Kouimtzis, C. Samara, D. Voutsa Environmental Pollution Control Laboratory, Department of Chemistry, Aristotle University Thessaloniki,

54006 Thessaloniki, Greece

Abstract

In order to evaluate the presence of heavy and other metals in the area of

Thessaloniki, air particulate matter and roadside dust samples were obtained at various sampling points located in the urban and industrial area of the city. The samples were analyzed by instrumental neutron activation and atomic absorption spectroscopy. Metals determined in TSP and inhalable particles were characterized with respect to their origin from natural or man-made emission sources. A receptor modeling approach was applied to identify and apportion sources of air particulate matter and heavy metals. Regarding the presence of heavy metals in roadside dust results showed elevated concentrations of Pb, Zn and Sb in the urban area, whereas in the industrial area found increased concentrations of As,

Cd, Cr and Pb.

Introduction

The major elements of the earth's crust form a sequence of minerals and ores dependent on prevailing temperature and pressure. The minor elements usually occupy spaces in the lattices of minerals according to specific rules. Most of the minor elements are known as the trace elements and play an important part in animal and plant nutricion. There are groups of trace elements which are known somewhat arbitrarily as "heavy metals". Regarding environmental problems, lead, mercury, cadmium, copper, zink, arsenic are perhaphs the most important heavy metals. Trace elements are distributed in the environment via two physical processes. In the course of primary dispersion the elements are concentrated in certain types of geological formations leading to the formation of localized concentration known as ores. Secondary dispersion within the surface environment is of great importance in elemental differentiation within soils. In this case mobilization is strongly influenced by pH, Eh and the stability of the minerals which have to be decomposed.

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A third process results from human activities in which the elements have been rearranged in such a way that pollution has occured. Trace elements find their way into humans either by direct absorption via the air or drinking water, or via the food chain. An indispensable link in the food chain is plant life while airborne particulates are in air from which humans receive their allocation of trace elements. The presence of heavy metals in airborne particulate matter and roadside dust have always been of great concern to people living in urban areas, because of their effects on human health. A complex urban environment usually contains numerous metal emission sources. Since emissions from several types of sources can be characterized by their element composition, chemical analysis of airborne particulate matter and roadside dust can assist in source identification. Thus, element such as As, V and Cd are released into the atmosphere from oil or fossil fuel combustion, while metals such as Fe, Cu, Cr, Zn and Sb are components of many alloys, pipes, wires and tyres in motor vehicles and pollute mainly the roadside environment as a result of mechanical friction and normal wear and tear. However, owing to the complexity of pollution sources and the effect of other factors (such as meteorological conditions, secondary processes etc) that alter the composition and distribution of aerosols and dust; the evaluation of the contribution from individual sources is sometimes difficult. In this respect, source apportionment techniques are employed for identification and quantification of the major particle pollution source dosses. The aim of this work was the study of the heavy metal distribution in the area of Thessaloniki and the identification of emission sources. Increased concentration of particulate matter have often been shown in the atmosphere of Thessaloniki [1,2,3]. Thessaloniki, with a population of more than one million is the second largest city in Greece. It is located in a bowl formed by low hills facing at the northern end of Thermaikos Bay. The development: of the city is characterized by a relatively slow industrial growth followed, after 1960, by rapid industrialization and increase of population. The lack of plan of location of the new industrial units has as a result created various environmental problems. Today, the structure of the city, which stretches over 20 km, includes an urban area with high traffic density surrounded by two industrial areas north and northwest as well as by a rather rural area extending east and southeast. The main activities in the industrial areas include fertilizer production, iron and steel manufacturing, cement kiln, sulfuric acid and chemicals production as well as oil products and manganese ore treatment. From the meteorological point of view the area has a high proportion of calm weather and high humidity. Temperature inversion and insulant effects are very common leading to very limited dispersion of the pollutants.

Experimental

Heavy metals in inhalable particles Inhalable airborne particles were collected from the city center (Figure 1) during the period October 1993 - May 1994. All samples were collected over a 24-h period on glass fibre filters (99% collection efficiency for 0.3 um particles). A sierra-Anterson High Volume Sampler equipped with a Sierra Cascade Impactor

Air Pollution Engineering and Management 115

Figure 1: Map of the sampling area: Sj, 82, TSP sampling points. 1-20 roadside dust sampling points.

operating at 40 CFM was used to collect fine (d < 2 um) and coarse (2.5 < d < 10 um) particulate fractions. Unloaded and loaded filters were weighted after conditioning in a desiccator. Each loaded filter was extracted with a mixture of HC1 and HNOg acid in an ultrasonic bath and the metals were determined by AAS.

Heavy Metals in TSP [3] Total suspented particulates were collected during the period July 1987- June 1988 at two sampling stations, Stl (91 samples) in the city centre and St2 (93 samples) at the northwestern border of the residential area, close to oil refinery and industrial area. Details of sampling and determination of the heavy metals are given in reference [3].

Heavy metals in roadside dust [4] Dust samples from 20 sampling points were seasonally collected during the period Summer 1987 - Summer 1988. The sampling points (Figure 1) were selected taking into account the possible emission sources and the traffic density.

Details of sampling and determination of heavy metals are given in reference [4].

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Results and Discussion

Heavy metals in TSP [3] In Table 1, are summarized the results obtained for TSP and their heavy metals content during the period July 1987 - June 1988. These results show quite large variations both in TSP and heavy metal concentration. This was attributed not only to fluctuation of emission sources over the seasons (traffic, industries, domestic hearing etc) but also to weather conditions that strongly affect the dispersion of airborne particles. Some metals fluctuate much more the concentration of TSP indicating that these metals are likely to be emitted by specific sources.

Table 1: Mean concentration of TSP and heavy metal in the atmosphere of Thessaloniki (July 1987 - June 1988)

Element Stl St2 ng/m^ Mean SD Range Mean SD Range Fe* 780 620 340-1570 1070 940 330-2560 Pb* 1040 630 130-3280 1370 1280 120-7100 Mn« 95 65 20-371 122 80 20-430 231 149 45-603 169 92 58-324 ZnC^* 229 85 61-427 218 87 81-466 Ni° 15 10 11.9-43.0 13 9 2.0-34.2

Cr* 11 5 1.0-22.2 13 6 3.8-33.5 Co' 6 4 1.0-12.5 5 3 0.8-9.7 yc 18 21 2.3-98.6 22 14 4.9-63.5

TSP* 256 94 94-623 283 191 96-766

* (ug/m3) a = 90, b = 51, c = 23 samples

It is clear that the annual average concentration of TSP is much higher than the EEC standard of 150 ugW. More than 30% of TSP were found to be higher than 300 ng/m^, which is the limit of the 95th percentile of all mean daily values taken during the year. This means that there is a serious atmospheric pollution problem, in the area of Thessaloniki, caused by air particulate matter. Re- sults obtained during the years that followed the examined period (Table 2) show that the problem still exists [5]. However, heavy metal concentrations were found to be of the same order of magnitude with those reported for other cities [6-12]. As far as Pb is concerned the mean annual concentration did not surpass the limit of 2.0 jig/m^ of the EEC, although these concentrations occasionally reached 3.3 and 7.1 jig/rrP at Stl and St2 respectively. The decrease of Pb content in gasoline from 0.4 g/1 to 0.15 g/1 since February 1998 and the use of unleaded gasoline has, as a result, remarkable decrease of Pb in the atmosphere of Thessaloniki as it can be seen from the data presented in Table 2. Temporal variation of TSP and metal mass proportions show that some metals have distict emission patterns changing with the seasons. Thus, during winter TSP seems to be enriched with Fe, V, Ni, Co, Cr, while Mn and Zn showed more or less constant mass proportions throughout the year. Assuming no change in industry activities over the seasons, the increased emission of V and Ni (and partially Cr, Cu and Co) during the winter could be attributed to oil combustion in domestic and commercial heating facilities.

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Table 2: Mean concentration of TSP and Lead in the atmosphere of Thessaloniki

(January 1991-December 1993).

Year Stl St2 TSP (ug/m3 I Pb (ng/nf) TSP (ug/m') Pb (ng/nV) 1990 266 580 366 630 1991 206 390 268 470 1992 251 570 340 1993 195 280 231

Metal Enrichment in Air Dust. To evaluate the enrichment of heavy metals in TSP, the enrichment factors (EFs) were calculated with respect to their distribution in the earth's crust. Iron was used as the baseline element. This means that all iron determined in air dust is considered to be soil derived. The results are presented in Figure 2a.

DOOOO-, a Air dust

COOOi

1000-

: 100

I' K)i

01 a Co Pb Zn Mn Cu Mi V OX)-, b: Rood side dust A

100-

ii ^ u

'. '!

(XL Cr Co Pb • Residential area * Industrial area

Figure 2. Enrichment factors of heavy metals in air dust (a) and road side dust (b) in the area of Thessaloniki.

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As can be seen, the mean EF values of Pb, Zn and Cu are much higher than unity. This means that these metals are released into the atmosphere almost exclusively by man-made sources. The EF values of Mn, Cr, Co, Ni and V are lower (between 4 and 12) indicating significant contribution from natural sources (crystal materials)[13]. It is worth noting that the EF or Cr in air dust is about the same as that found in roadside dust of the area of Thessaloniki [4]. This means that the majority of atmospheric Cr is soil derived. However, the distinction between natural and man-made sources is based on the total quantity of airborne particles collected by the high-volume sampler.

Since EF values are strongly dependent on particle size, higher EFs for many metals (Pb, V, Ni, Cr etc.) would be obtained if only fine particles were examined. This is confirmed looking at the results presented in Table 6, which are referred to the fine and coarse particles. The contribution of historically - contamined soils to the airborne metal concentrations was also considered. For this reason [M]/[Fe] ratios in suspended particulate matter were compared to the ratios found in local road-side dust.[4] Assuming iio change in elemental ratios upon entertainment by wind action, the contribution of entrained material was calculated for the relation:

[M] soil

[M] entrained = [Fe] atmos [Fe] soil where [M] is the concentration of the metal being concerned. It must be pointed out that this calculation gives only an estimation of the entrainment contribution, which is overestimated if other sources of Fe are present. The results show that Pb, Zn, Mn and Co appear to be derived from emission sources rather than wind-blown soil, while about 50% of Cr seems to be soil-derived.

Influence of wind direction. The frequency distribution of wind directions is given in the histogram of Figure 3. This histogram, obtained from 349 observations, showed that the period July 1987-June 1988 was characterized mainly by calms and NNE winds. It should be pointed out that these winds are usually of low speed (<10 km/h) in contrast with southerly winds, which have higher speed (10-20 km/h). Mean and range concentrations of TSP (ug/rn^) related to the predominate wind direction are given in Figure 3. As can be seen, higher concentrations of TSP at both stations were measured during periods of calm. The same trend was observed for V, Ni, Co and Pb in air dust, indicating that during periods of calm air dust is enriched with these metals. This means that these metals are mainly emitted from specific load sources (traffic, domestic heating). However, some transfer of Ni, Co and V to St2 by NW winds was also observed. This could be attributed to industrial emissions. On the other hand, Mn and Cr concentrations in air dust showed only little dependence on wind direction. Chromium showed slightly increased concentrations at St2 with NW winds, probably due to emissions from the iron and steel manufactures located in this direction. Cr and Mn, as well as V and Zn, showed relatively high concentrations at both stations with NNE winds. The primary emission sources in this direction consists of the cement industry and two smelters. However, the entire area east

St, Sti

Mea?> Range

600-

400-

- 200-

N-349

= 20

NNE SE S SWNWC

Figure 3. Wind direction effect on TSP (ug/nf) in the atmosphere of Thessaloniki.

and southeast of the city is also characterized by natural chromite deposits that contain V, Zn, Mn, Co etc. as minor elements [14].

Source Apportionment and Elemental Mass Balances. All the data collected during the period of 1987-1988 have been used to identify and apportion the sources of airborne metallic pollutants [15]. For this purpose, the model regression on absolute principal component scores (APCS) was developed using heavy metal concentration data within total suspended particles. This technique was used, provided quantitative information regarding both source particle characteristics and impacts. The analysis identified four major sources of heavy metals within TSP in the city centre (Stl) and five major sources in the station ST2 closed to industrial area. The mean mass contributions to TSP from principal component analysis identified sources are presented in Table 3: The results in Table 3 indicate that only 29 percent of TSP is explained by the identified metal emission sources affecting the monitoring site in the centre of the city. In order of importance, contributions to ambient TSP concentration were fuel oil burning (12%), pyrometallurgical non-ferrous metal production (8%), motor vehicle exhaust (5%) and soil resuspension (4%). On the contrary, 56 per cent of TSP is explained by the estimated mass contributions from PCA identified metal emission sources for the sampling site located at the northwestern border of the residential area. Contributions to ambient TSP concentration at Station 2 were fuel oil burning (20%), industrial Cr source (15%), soil resuspension (9%), non- ferrous industry (8%) and motor vehicle exhaust (4%). An underestimation of the soil resuspension contribution at both sites is obvious and must be attributed to the fact that the primary matrix elements in soil and cement were not included in PC analysis. The contribution of this particle source was found to be highest at Station 2. This station is also more strongly affected by oil burning emissions.

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Table 3: Mean mass contributions from PC A identified sources

Source Estimated contribution to TSP (ug.rn-3 ± S.E. of the mean)

Station 1 Station 2 Soil resuspension 11. 7 (±2.2) 25.5 (±4,5) Oil burning 33.5 (±14.3) 59.5 (±9.7) Non-ferrous metal works 22.7 (±2.7) 22.3 (±1.3) Motor vehicles 13.5 (±6.1) 10.5 (±3.6) Industrial Cr 44.9 (±5.6) Unexplained 198.3 (±17.4) 129.8 (±20.1) Total predicted 279.6 (±15.9) 293.0 (±12.7) Total observed 260.5 (±9.5) 289.6 (±11. 9) Pred-Obs. mass correlation 0.84 0.86

After the estimation of the mean source impacts and elemental profiles, the elemental mass balances were calculated by taking their products. Finally, the mean source contribution to heavy metal concentrations for both stations was calculated. The results are presented in Table 4. The correlations of the predicted and observed values are quite high, more than 0.91 for both stations, except for Zn

(0.78) and Cr (0.74) of the station Stl.

Table 4: Mean source contributions to heavy metal concentrations for Station 1 and Station 2 (ng m-3)

Ele- Soil Oil Non-ferrous Motor Industr. ment resuspension burning metal works vehicles Cr Stl Stl Stl Stl Fe 449.29 71.41 42.68 47.62 Pb 174.13 87.84 262.2 201.15 Mn 8.76 21.46 4.77 2.83 Cu 10.04 3.35 192.73 8.63 Zn 22.66 18.78 56.07 13.63 Ni 6.89 2.68 4.54 1.08 Cr 1.99 1.01 2.27 0.81 3.85 2.04 Co 0.67 0.27 V 7.94 8.38 0.91 2.43 Ele- St2 St2 St2 St2 St2 ments Fe 323.72 238.0 81.56 334.8 114.15 Pb 83.16 182.85 342.63 343.1 147.85 Mn 10.71 64.15 3.78 11.18 7.19 Cu 5.61 7.19 2.1 165.17 12.13 Zn 23.72 53.95 14.19 58.1 35.5 Ni 4.85 4.79 0.84 4.02 2.25 Cr 1.28 1.2 0.74 3.58 6.29 Co 2.55 0.6 0.32 0.89 0.45 V 6.89 8.99 1.05 9.89 5.39

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The application of another model, a modified version of factor analysis/multiple regression, identified the same type of the sources with similar contribution to TSP [16].

Heavy metals in roadside dust [4] Results obtained from the analysis of roadside dust samples of the area of Thessaloniki showed a considerable seasonal variation for most of the elements. However, individual elements found to have different seasonal dependency, probably due to differences in their release in the environment and their mobility. The mean elemental concentrations are presented in Table 5. From these data it is seen that some elements are primarily dependent on industrial activities while others on traffic. Increased concentrations of As and Cd were found near and around the main industrial area (IND 1). Particularly-high concentrations of

As (up to 563 ug.g-i) were found at sampling points 12 and 13. These concentrations could be attributed to As emissions from the fertilizer plant located in this re- gion, where about 80.000 ton.y* of Fe$2 are burned for sulfuric acid production. When vegetable samples, grown in this area near sampling points 12 and 13, examined (March 1990) for the metal content it was found that some of them were contaminated with high As concentration [17]. Highest concentrations were found in endive and spinach. On the contrary, As concentration in all vegetables grown in the area near the sampling points 2 and 3, were very low, closed to

Table 5: Mean (a) concentration of heavy metal (jig/g) in roadside dust of the area of Thessaloniki

Sampl- Fe Cr Co Pb Zn Mn Cd As Sb ing points (mg/g) RUR 1 38,8 1469 50.5 234 85 683 1.50 5.9 1.06 2 23,0 1442 25,4 67 42 445 2.06 7.1 0.24 3 22,9 338 10.4 60 208 281 1.80 10.0 0.97 20 13.0 46 5.6 102 98 152 ND 9.9 0.65 CITY 4 20.1 90 8.9 454 431 256 1.68 10.3 1.69 N 5 26,9 201 10,5 1094 1086 249 1.30 31.5 5.89 6 23,7 139 8,9 771 807 349 0.90 16.5 7.09 7 26,4 210 10.5 936 214 253 1.47 14.2 4.18 8 25,4 102 8,0 589 583 353 1.01 24,1 4.78 9 31,9 166 8.7 575 517 347 0,62 179.2 665 IND1 10 29,2 170 9.3 431 1924 383 0.41 64.5 6.49 11 28.3 244 10,0 313 331 258 2.74 33.7 3.64 338,6 5.30 12 47,4 336 13,6 413 574 438 1.29 13 41.8 362 10.5 506 207 428 2.62 200.6 159 14 23,5 116 4.3 306 176 307 1.78 40.0 1.39 15 53.2 240 8.4 255 217 352 2.64 67.2 2.87 IND2 16 19.0 97 9,6 730 177 226 ND 23.5 1.79 17 23.9 161 8.3 420 567 260 0.36 29.9 1.72 18 30.0 371 8.9 611 474 493 0.22 65.8 3.30 19 50.3 1332 18,9 567 239 274 0.65 107.4 3.42

(a) Of four sampling (once a season) during the period summer 1987-spring 1988.

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detection limits. Results obtained during 1993-1994 show a decrease in the As concentration of the vegetable grown in the area near the sampling points 12 and 13 which is attributed to the fact that elemental sulfur (instead of FeS2) is burned for sulfuric acid production since 1991 [18]. Relatively increased concentrations of As and Cr were also found at sampling point 19 (IND 2), next to the cement producing plant. The maximum concentrations of Cr, Co and Mn were observed south-east of the city (sampling points 1 and 2), where the main activities are agricultural or light industrial. The high levels of Cr, Co and Mn are attributed to the fact that soil in this area is rich in chromites that contain Co and Mn as minor elements. Pb was found to be strongly dependent on traffic density, since higher concentrations were determined along the main traffic roads (sampling points 5, 6, 8, 13, 16, 18 and 19) or in front of bus stations (sampling point 7). The contribution of possible industrial emission sources to the Pb pollution level determined near and around the industrial area, could not be distinguished from the Pb emissions due to the traffic, because this area is also characterized by high traffic density. Taking into account that the average Pb concentration in the Greek Sediments is 28 ug.g-*, even the less frequented by traffic points (2 and 3) seem to be contaminted. The above observations are in agreement with the enrichment factor presented in figure 2b. The mean Pb levels in roadside dust from the 20 sampling points (427 jig.g-i) is in good agreement with that reported by other investigations for the city of Thessaloniki, but they are higher than reported for Athens [19-28], However, when compared with other cities of the world Thessaloniki seems to be less contaminated by lead [22-24]. Of course, the selection of representative sampling point is, in this case, of great importance.

Heavy metals in inhalable particles

The fact that the annual average concentration of TSP in the atmosphere of Thessaloniki is much higher than EEC standards leaded us to examine the concentration and contamination of inhalable particles. For this purpose, an impactor was used to collect the inhalable portion width of <10 n and to separate them into two fractions. The fine particles with d < 2,5 jo, and the course particle with 2.5 < d < 10 u. The results obtained for the period October 1993 - May 1994 for the city centre of Thessaloniki are summarized in Table 6. First of all, it can be seen that although the inhalable particles is a part of the TSP, their mean concentration is higher than the EEC standards of 150 u£/m^ for TSP. It is also clear that the partition of the heavy metals is different for each element with higher contamination of the fine particles. Thus, there is a remarcable enrichment of the fine particles with Pb and Zn, which also confirms the fact that these two elements are of man-sources taken into account that the fine particles are of man- sources. The ratio fine [M] / coarse [M] gives us some evidence of the origin of air particles. The value of this ratio for the examined metals is in the following order Zn (35.1) > Pb (5.5) > Cu (2.2) > Mn (1.8) > Fe (0.76), which means that Pb and Zn are primarily of man-sources while Fe is of natural origin. The data of Table 6 have also been used to identify and apportion the heavy metal emission sources, using the same techniques as for the TSP. The analysis identified the same four major sources for the city centre of Thessaloniki with the same order of importance, fuel oil burning (15%); pyrometallurgical non-ferrous metal production (8%), motor vehicle exhaust (7%) and soil resuspention (6%).

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Table 6: Mean concentration of inhalable TSP in the atmosphere of Thessaloniki (City Center: October 1993 - May 1994)

Element TSP < 2.5 urn 2.5 urn < TSP < lOum

ng/m^ Mean& SD Range Mean SD Range Fe 460 94 319-673 604 158 320-861 Pb 293 106 94-646 54 19 15-77 Mn 45 24 15-116 24 14 6-66 Cu 340 129 111-605 155 60 78-269 Zn 1354 104 1211-1650 39 14 13-68

TSP 117 32 62-178 64 27 19-130

* (ug/m3) a = 32 samples

Conclusions

Encreased concentrations of TSP and inhalable particles were found in the atmosphere of both urban and industrial area of Thessaloniki. Their annual average concentration is much higher than the EEC standard of 150 ug/m^.

Lead, zinc and copper were found to be primarily emitted from man-made sources. Vanadium, nicher and cobalt seem to be derived partially from natural and man-made sources, while Gr is mainly soil-derived. Four and five major sources of heavy metals within TSP were identified in city center and industrial area respectively. Regarding roadside dust, increased concentration of lead was found in the urban area whereas high concentration of As was found in industrial area. In both cases their emission sources were identified.

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