WFL Publisher Science and Technology Meri-Rastilantie 3 B, FI-00980 Helsinki, Finland e-mail: [email protected]

Journal of Food, Agriculture & Environment Vol.10 (2): 810-817. 2012

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Biomonitoring of air pollution in Prague using tree leaves Petr Soudek, Pavel Kinderman, Petr Maršík, Šárka Petrová and Tomáš Vaněk * Laboratory of Plant Biotechnologies, Joint Laboratory of Institute of Experimental Botany AS CR, v.v.i. and Crop Research Institute, v.v.i., Rozvojová 263, 162 05 – Prague 6, Czech Republic. *e-mail: [email protected] Received 18 November 2011, accepted 28 April 2012.

Abstract Urban areas are significant sources of various types of pollutants, especially particles. Dust particles are, due to their size and chemical composition, the major environmental problem. This study monitored the dust particles concentration in the air during two years at the traffic loaded roads of Prague and Kladno, tested possible reduction of airborne dust in the atmosphere by the absorption on the surface of leaves of suitable plants and discussed the possibility of the influence of the eruption of Iceland volcano Eyjafjallajökull on the quantity and composition of dust particles in the atmosphere. Key words: Dust particles, heavy metal, phytoremediation, volcanic ash.

Introduction These days, dust particles pollution is a serious air quality problem in the Czech Republic. The limit value for airborne dust is exceeded in a third of the Czech Republic, where two thirds of the population live. These people are exposed to the dust and their health risks are increased. In the Czech Republic and Poland, this is the worst from the entire European Union. Prague came out as the most polluted city by the airborne dust pollution among 30 major European cities 6. Twenty-four hours limit for the suspended particles matter PM10 is 50 µg.m-3. This limit can be exceeded 35 times per year. Another available limit 14 provides the highest average concentration throughout a year to 40 µg.m-3. The origin of the dust pollution is natural or anthropogenic. Significant anthropogenic sources are combustion processes, mainly in automobile engine and power plants, and other hightemperature processes 1. From natural sources can be mentioned e.g. volcanic eruptions or forest fires 17. Particles are released from air into other parts of the environment. The residence time of particles in the atmosphere depends on their size. Small particles resist in the air for a long time. The inhalation of particles smaller than 10 µm mainly harms the cardiovascular and pulmonary system. It can cause chronic bronchitis and chronic pulmonary disease. Some researches 4, 5, 13 agree that the adsorption of organic compounds with mutagenic and carcinogenic effects can results in a lung cancer 19. However, according to the recent studies, the health problems can be caused by airborne dust, even lower concentration than the limit. A possibility to reduce the amount of airborne dust in the atmosphere is using sorption on the surface of plants, especially trees 9. The ability to decrease the concentration of pollutants in the atmosphere depends mainly on plant species 12 and on the size of their leaves and stomata 18. Trees are able to reduce the amount of ammonium, volatile organic compounds (VOCs), SO2, O3 and dust particles 2. Also, Catinon et al. 3 described tree bark as the site of a deposition of dust particles 16. 810

This paper describes the monitoring of the dust particles concentration in the urban environments and quantifies the potential of trees planted surrounding the heavy traffic roads to reduce dust particles in the atmosphere. This work also discusses the influence of the eruption of volcano Eyjafjallajökull on the amount and element composition of airborne dust in the atmosphere. Materials and Methods Study area and sampling site description: The experiment was carried out in Prague, capital city of the Czech Republic close to Drnovská Street with heavy traffic. Ten plant samples from each tree were collected in the distance of about 2 m from the road during two sampling periods (June 2009 and June 2010). Seventeen woody species, Acer pseudoplatanus, Acer platanoides, Fallopia aubertii, Syringa vulgaris, Juglans regia, Tilia cordata, Symphoricarpos albus, Ulmus minor, Prunus avium, Prunus insititia, Sambucus nigra, Malus, Rosa canina, Pyrus communis, Cornus sanguine, Populus nigra and Betula pendula, in the locality were sampled. The leaves of plants were scanned for leaf area determination. Leaves with total area about 10 dm2 were washed by double distilled water (0.5 dm3) in sonic bath and particles were filtered under vacuum through Teflon filter (0.45 µm). Dried filter was weighed and used for elements determination. Heavy metal determination: Each dried filter was digested with 5 cm3 of acid mixture of HClO4 and HNO3 (15/85%, v/v) in digestion Teflon tubes overnight. Digestion was completed by gradual increase of temperature from 60 to 195ºC according to Zhao et al. 20. Digestion protocol was as follows: 3 hours, 60°C; 1 hour, 100°C; 1 hour, 120°C; 3 hours, 195°C. After cooling, 2.5 cm3 of HNO3 (20%) was added, whirl mixed and warmed to 80°C for 1 hour. The final volume was brought to 10 cm3 accurately. The element content in the solutions was determined by Journal of Food, Agriculture & Environment, Vol.10 (2), April 2012

quadruple-based inductively coupled plasma mass spectrometry (ICP MS, X Series 2, Thermoscientific) under the conditions given in Table 1. The quality of the analytical data and the procedure were verified using NIST 1640 (Trace Elements in Natural Water) and acid digests of NIST 2711 (Montana Soil) standard reference materials. The differences between the measured and certified values did not exceed 5% relative standard deviation (RSD). Reagent blanks and unexposed filter mineralized in the same acid mixture were used at the start of batch of analysis. Particle matter collection: The measurements were provided during two years (2009-2010) every week at three sampling points (3 m from Drnovská Street, Prague, and two control points 3 m from the centre circle of Kladno City and 100 m from all roads on the periphery of Prague). PM10 were measured by MicroDust Pro 880nm Aerosol Monitoring System (Casella Cel Ltd.) with air flow 3.95 L/min during two hours and results were processed by WinDust Pro software (Casella Cel Ltd.). Statistical analyses: All statistics were estimated by the use of Statistica (StatSoft, Inc., Tulsa, Oklahoma, USA). Results and Discussion The concentration of dust particles was measured at sampling point Drnovská Street in Prague, which was chosen for its heavy traffic and potential high dust concentration. For the comparison we chose a place on the periphery of Prague more than 100 m away from roads or any other source of pollution and the centre of Kladno City (about 20 km far from Prague) with high traffic and metal industry. We found a strong negative correlation with temperature at all three sampling points (Figs. 1-3). The highest dust concentration was measured during the winter time, when the outside temperature was close to or below zero. Low temperatures generate a decrease of scattered conditions. Also, the combustion increase during the winter time, especially in local combustion chambers, leads to dust particles release to the atmosphere. The amount of particles on the exposed places (Kladno City and Drnovská Street in Prague) was at similar level as the amount of particles on the periphery of Prague (more than 100 m from road). The eruption of volcano Eyjafjallajökull on April 14th, 2010, did not dramatically influence particles concentration in the

atmosphere. We observed increase of dust concentration (two times higher than usual average concentration in this season) after the date of the volcano eruption, but four weeks later, the dust concentration decreased to its usual value. In the next experiment, the ability of trees to absorb dust particles from the atmosphere on their leaves surface was studied. Seventeen plant species were tested (samples were collected surrounding of Drnovská Street, Prague). Ulmus minor and Rosa canina were identified as the best plants for dust adsorption. In comparison with Populus nigra, which was identified as the worst one, the elm tree adsorbed five time higher amount of dust particles (Table 2). Table 2. Amount of dust particles adsorbed on leaf surface of different plant species. Plant species Ulmus minor Rosa canina Cornus sanguinea Tilia cordata Pyrus communis Malus sp. Prunus avium Fallopia aubertii Sambucus nigra Syringa vulgaris Symphoricarpos albus Acer pseudoplatanus Juglans regia Prunus insititia Betula pendula Acer platanoides Populus nigra

Ø adsorption ± SD [µg.dm-2] 3123.33 ± 149.26 2900.86 ± 226.11 1824.34 ± 180.77 1799.52 ± 26.86 1728.27 ± 78.90 1695.35 ± 276.56 1443.92 ± 141.76 1442.30 ± 43.55 1440.79 ± 96.02 1367.71 ± 173.17 1333.15 ± 101.82 1198.10 ± 152.65 1114.11 ± 87.22 985.31 ± 93.46 940.66 ± 18.36 827.60 ± 44.45 649.56 ± 38.97

SD: Standard deviation, n=10.

We determined the element composition of adsorbed dust particles in June of 2009 and June 2010. We found significant increase of some elements in June 2010, especially Na, Mg, Al, K, Ca, Ti and Hg (Tables 3-6). Eiríksdóttir and Alfremsson 7 and Möckel 10 presented element composition of ash eructed from volcano Eyjafjallajökull. They found Na, K, Ca, Mg, Si, Fe and Ti as the major elements. The similar chemical composition was determined in volcanic ash from St. Helen 17 or volcanic dust from blue ice fields in Antarctica 8. It is possible, that the changes in chemical composition of dust particles adsorbed on leaves in June 2010 might be caused by the volcano eruption. An increase of a mercury Table 1. Operating conditions used for ICP-MS measurements of elements. concentration in the dust also Instrument X Series 2, Thermoscientific corresponds with volcano, because Plasma RF power 1.400 W many areas of geothermal activity Reflected power