Meteorological investigation of high PM10 concentration in Istanbul Kagithane region

Air pollution has become an important problem in the world because of industrialization and urbanization. For years, in our country and the world, there are health and environmental issues connected with the air pollution. In 1952, nearly 5.000 people lost their lives because of the effect of air pollution in England. In 2013 in China, visibility decreased due to the fog event causing from air pollution, the number of traffic accident rose to 70 and lots of allergic and asthma people were affected from this pollution. Occurrence of air pollution decreases the air quality in the atmosphere. In the world, the other countries attach quite importance to air pollution and air quality. Especially China has lower air quality conditions due to its high population density and higher industrial activities. Studies done in China are generally about effects of particulate pollution on health effects. Air pollution affects the tourism sector so that in Spain PM10 pollution effects on tourism were investigated. Also, in Europe studies and analyzes include particulate matter sources and particulate matter's transboundary transportations over continentals. In Turkey, studies about air pollution had begun in 1960's and at first, studies were done in Ankara then with the increase of air pollution problems in other cities, studies and analysis became widespread. Studies were generally focused on Istanbul because of increasing air pollution due to the city's geographical location, climate conditions, factor of westerly and southerly winds, domestic heating and motor vehicle emissions, ships emissions passing over Bosphorus. The other specific studies based on Istanbul were done over the regions, which have high traffic density. Industrial emissions, domestic heating, organic sources (volcanic ashes, desert dusts, pollens, etc.) and chemical reactions in the atmosphere or transboundary particulate matter transportation cause air pollution in the atmosphere. Meteorological conditions are also have important effects on occurrence of air pollution besides particulates in the atmosphere. Especially high pressure, calm winds and no precipitation conditions increase the particulate matter concentration and duration in the air. İstanbul is one of the megacities with approximately 15 million people living in and population density increases rapidly day by day. The number of residences increases along with the increment of the population and usage of motor vehicles and at the same time, emissions due to domestic heating and vehicles are expected to be risen. Also, İstanbul is exposed to particulate matter pollution carried with westerly winds coming from Europe and affected by southerly winds where there is dust transportation from Africa over Saharan Desert at the spring and fall seasons. Turkey's south regions and İstanbul are affected from this dust transportation significantly. Therefore, all these factors play a role in enhancing pollution in İstanbul. In this study, Kağıthane region in İstanbul were selected as study area. Kağıthane region is a creek valley and due to this topographical structure, low dispersion conditions are obtained. When high-pressure system and low wind speed conditions occur and high pollutant concentrations are measured, air pollution and air quality decreases dramatically. For this purpose, it is important to do PM10 measurements and determine the sources for environmental and health issues. In other studies, it was put forward that PM10 concentrations exceeded the European Union (EU) limits on daily and monthly bases. In our study, PM10 concentrations were measured regularly in between 2012 and 2014 years and some statistical analysis were done for daily, monthly, seasonally PM10 concentration. In 2012, mean PM10 concentration value was calculated as 80.77 μg/m3 and maximum concentration values were found as 195.2 μg/m3. In 2013, mean PM10 concentration value was calculated as 86.83 μg/m3 and maximum concentration values was found as 329.9 μg/m3 and In 2014, mean PM10 concentration value was calculated as 79.66 μg/m3 and maximum concentration values was found as 265.2 μg/m3. To test the homogeneity of the data some quality control and quality assurance tests were done. According to results of homogeneity test, PM10 concentration data belonging to 2014 year were selected as study data. After these analyses, episodic period were determined in between 5 December 2015 and 25 December 2015 because PM10 concentration increases gradually from December 5 to December 25. For this day the sources of PM10 concentration were determined. Meteorological analyses were done and upper level air charts were examined. According to meteorological analysis results, on the episode day, there was a high-pressure system over Turkey and PM10 was sunk over Kağıthane Creek Valley because of calm winds and the inversion effect. Wind speed and direction is obtained by using Weather Research and Forecast model (WRF) and analyses for the episode day were done. With WRF outputs 850hPa temperature, height and wind speed values were visualized for inner (10x10km) and outer (3.3x3.3km) domain. 700hPa and 500hPa upper air maps were plotted to see the upper air particulate matter transportation with higher wind speed. According to these maps, with the effects of low-pressure system over Iceland and approaching high-pressure system over Aegean and Mediterranean to Istanbul on December 15th 2014, there was particulate matter transportation over Eastern Europe to Istanbul by westerly winds from 4500m and 6000m heights in the atmosphere. There was no precipitation on episode day due to the high-pressure system. The effects of transboundary PM10 transportation on episode day were searched with back trajectory analysis with Hybrid Single Particle Lagrangian Integrated Trajectory model (HYSPLIT). According to this trajectory analysis, PM10 transportation were started from eastern Europe at 4500m and 6000m height two days before episode day and PM10 transported from Africa over Saharan Desert with southerly winds at 1500m nearly six days before. These transportations from different locations was caused to measure high level PM10 concentrations. In addition to these analyses, horizontal and vertical wind speed was measured with SODAR instrument over study area. These measurements were done at different elevations from surface level. In every 30 minutes at different elevations (30, 50, 70, …, 410m) wind data were recorded. Horizontal wind speed component was measured approximately 2 m/s over surface and there was a decrease in wind speed magnitude at 50m level. From surface to 50m heights, there was an inversion layer on December 15 at 00UTC. After 50m heights, wind speed increases with height. Because of the low wind speed effect, there was not a significant PM10 transportation over surface. Vertical wind speed component was measured and due to the inversion, the motion of air was toward from surface to the 50m height. Vertical wind speed component was measured with negative sign at 00UTC time period. With the effect of vertical wind speed, there is a vertical PM10 transportation over study area and these situations caused PM10 sank. Altogether, meteorological, topographical and human effects caused the higher PM10 concentration measurements over Kağıthane Valley region