Određivanje porekla PM2,5 frakcije aerosola u graničnoj zoni urbanog područja Beograda primenom komplementarnih statističkih metoda

Abstract

U ovom radu analizirani su elementni i jonski sastav PM2,5 frakcije aerosola uzorkovanih tokom perioda Maj 2014 – Maj 2015. godine na rubu urbane teritorije Beograda. Masene koncentracije 19 elemenata (Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, As, Sr, Ba, Pb) u sastavu PM2,5 izmerene su PIXE (Particle Induced X-ray Emission) metodom, dok su koncentracije tri najzastupljenija jona (NH4+, NO3-, SO42-) određene metodom jonske hromatografije. Primenom receptorskog modela PMF (Positive Matrix Factorisation) modela, na osnovu hemijskog sastava PM2,5, određene su dominantne grupe izvora zagađenja i njihovi doprinosi. Obrasci atmosferske cirkulacije – lokalne i regionalne – i njihov uticaj na doprinose identifikovanih izvora, kao i na masene koncentracije gasova prekursora neorganskih jona (NO2 i SO2), ispitani su kombinacijom niza receptorskih modela. Rezultati su pokazali da, iako postoji trend opadanja posmatrano u periodu od sedam godina, masene koncentracije komponenata antropogenog porekla u sastavu PM2,5, poput S, K i Pb, i dalje su relativno visoke, naročito tokom grejne sezone. Osim Ca i Ti, masene koncentracije svih elemenata bile su pod manjim ili većim uticajem antropogenih aktivnosti, koji je takođe izraženiji tokom grejne sezone. Neutralizacioni odnos sugerisao je kiselost PM2,5 na posmatranoj teritoriji, dok je nazastupljeniji jon bio SO42-. Identifikovano je pet dominantnih grupa izvora PM2,5: sagorevanje biomase, saobraćaj, sekundarni sulfati, lokalno sagorevanje fosilnih goriva sa nitratima i resuspenzija prašine. Najveće relativne doprinose pokazali su sagorevanje fosilnih goriva sa nitratima i sekundarni sulfati, dok je doprinos emisija iz sagorevanja biomase bio znatno niži. Analize uticaja lokalnih i dugometnih obrazaca atmosferske cirkulacije na doprinose izvora sugerisale su dominantno lokalno poreklo sagorevanja biomase i fosilnih goriva, formacije nitrata i saobraćaja. Pokazano je takođe da su sekundarni sulfati i resuspenzija prašine (zemljišne prašine ili peska) pod značajnim uticajem regionalinih i prekograničnih emisija. Interesantno je da su karakteristični meteorološki uslovi tokom merne kampanje – izuzetno visoka precipitacija i posledične poplave – naglasili značajnost uticaja emisija (SO2) iz regionalnih termoelektrana i termoelektrana na Balkanu na kvalitet vazduha u Beogradu. Pored uticaja resuspenzije poljoprivrednog zemljišta, predviđanja NOAA HYSPLIT modela ukazala su na doprinose peska transportovanog iz Saharske pustinje kao i iz oblasti istočno od Kaspijskog mora. Procena zdravstvenih uticaja PM2,5 sugerisala je da su najštetniji uticaji emisija iz lokanih procesa sagorevanja i sekundarnih sulfata, mada su detaljnija ispitivanja neophodna kako na epidemiološkoj tako i na toksikološkoj bazi.

The subject of this dissertation is the analysis of the elemental and ionic composition of the PM2.5 aerosol fraction sampled in May 2014 - May 2015 on the outskirts of the Belgrade urban area. Mass concentrations of 19 elements (Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, As, Sr, Ba, Pb), components of PM2.5, were measured by the PIXE method (Particle Induced X-ray analysis), while concentrations of the three major ions (NH4+, NO3-, SO42-) were determined by ion chromatography. Based on the chemical composition of PM2.5, the dominant groups of pollution sources and their contributions were determined using the PMF (Positive Matrix Factorization) receptor model. Atmospheric circulation patterns, local and regional, and their influence on the contributions of identified sources and mass concentrations of PM2,5 gaseous precursors (NO2 and SO2) were examined with a combination of several receptor models. The results showed that although there is a declining trend in the concentrations of anthropogenic components in PM2.5 (observed over a period of seven years), mass concentrations of some of them, such as S, K and Pb, are still relatively high, especially during the heating season. Apart from Ca and Ti, the concentrations of all elements were influenced by anthropogenic activities, which were more pronounced during the heating season. The neutralization coefficient suggested that PM2.5 within the examined territory was mainly acidic, while the most abundant ion was SO42-. Five dominant groups of PM2.5 sources have been identified: biomass burning, traffic, secondary sulfates, local combustion of fossil fuels mixed with nitrates, and dust resuspension. Combustion of fossil fuels with nitrates and secondary sulfates showed the largest relative contributions, while the contribution of emissions from biomass burning was lower. Analyses of the influence of local and long-term patterns of atmospheric circulation on the contribution of these sources suggested the dominant local origin of biomass burning and fossil fuel combustion, nitrate formation processes, and traffic. It has also been shown that secondary sulfates and dust resuspension were significantly affected by regional and transboundary emissions. Specific meteorological conditions that marked the measurement campaign (extremely high precipitation and consequential floods) emphasized the impact of SO2 - emitted from thermal power plants in Serbia and the Balkan region - on Belgrade air quality. Predictions from NOAA HYSPLIT model indicated the contribution of sand transported from the Saharan and Turkmenistan deserts in addition to the likely impact of resuspension of regional agricultural soil. Analysis of relations between the health impacts of PM2.5 on the population of Belgrade and the identified sources’ contributions suggested that the most harm was caused by emissions from local combustion processes and secondary sulfates. More detailed studies on this subject are necessary using both an epidemiologicaland toxicological approach.