Transactions on Ecology and the Environment vol 6, © 1995 WIT Press, www.witpress.com, ISSN 1743-3541 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. Transactions on Ecology and the Environment vol 6, © 1995 WIT Press, www.witpress.com, ISSN 1743-3541 114 Air Pollution Engineering and Management 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 Transactions on Ecology and the Environment vol 6, © 1995 WIT Press, www.witpress.com, ISSN 1743-3541 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]. Transactions on Ecology and the Environment vol 6, © 1995 WIT Press, www.witpress.com, ISSN 1743-3541 116 Air Pollution Engineering and Management 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 pol- lution 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.