Air Quality Issues and Settlement Suitability Analysis in Iğdır Central District
Mücahit Çoşkun, Hüseyin Şahiner, Onur Canbulat, Ahmet ÖztürkAir pollution can be a concern during certain seasons, specifically in autumn and winter, in the city center of Iğdır owing to the city’s geomorphological and climatological features. This study aims to examine the spatial and vertical distribution of air pollution in the atmosphere of the city center of Iğdır and identify suitable areas for urban settlement. The results revealed that areas with highest pollution levels were in the city center of Iğdır and in the plain area located north of the city. The geographical conditions, specifically in winter, limit convective air movements, cause inversion, and intensify air pollution. Height of the aerosol layer expresses the upper limit that pollutants can reach in the atmosphere. In the city center of Iğdır, height of the aerosol layer approximately 1000–1100 m, especially in winter. Furthermore, pollutants are trapped between 850 m, which is the average altitude of the city center of Iğdır, and these altitudes causes the pollution to be felt more intensely. A change in the city’s settlement plan (horizontally) cannot address this issue in the longterm as the same air pollution problem will occur again. Thus, settlements should be established at least above 1000–1100 meters, which is the upper level of the aerosol layer in winter, to prevent this issue.
Iğdır Merkez İlçesinde Hava Kalitesi Sorunu ve Yerleşim Uygunluk Analizi
Mücahit Çoşkun, Hüseyin Şahiner, Onur Canbulat, Ahmet ÖztürkHava kirliliği sorunu sanayi faaliyetleri olmasa dahi, jeomorfolojik ve klimatolojik özelliklere bağlı olarak belirli mevsimlerde sürekli hale gelebilmektedir. Iğdır merkez ilçesi özellikle sonbahar ve kış mevsimlerinde bu sorunun yaşanmasıyla gündeme gelmektedir. Bu sorunun çözümüne odaklanılan araştırmada, alan kapsamı Iğdır ili ve merkez ilçesi; konu kapsamı ise hava kirliliği ve şehir yerleşim uygunluğu ile sınırlandırılmıştır. Araştırmanın amacı, çalışma alanında hava kirliliğinin atmosferdeki alansal ve dikey dağılışını ortaya koyarak şehir yerleşimine uygun alanları tespit etmektir. Elde edilen sonuçlara göre, Iğdır merkez ilçesinde yerleşmelerin yoğun olduğu alan ve kuzeyindeki ovalık saha, kirliliğin en fazla olduğu yerlerdir. Alandaki coğrafi şartlar; özellikle kış mevsiminde konvektif hava hareketlerini sınırlandırarak inversiyon oluşumuna ve hava kirliliğinin daha yoğun hissedilmesine sebep olmaktadır. Gezegensel sınır tabakasının göstergelerinden biri olan aerosol tabakası yüksekliği, Iğdır merkez ilçesinde özellikle kış mevsiminde 1000-1100 m civarındadır. Kirleticilerin Iğdır merkez ilçesinin ortalama yükseltisi olan 850 m ile bu yükseltiler arasına sıkışmasıyla, alanda kirlilik daha yoğun hissedilmektedir. Şehir yerleşim planında yatay olarak yapılacak bir değişiklik, sahip olunan coğrafi özellikler sebebiyle uzun süreçte yine aynı hava kirliliği sorununun yaşanmasına sebep olacaktır. Bu nedenle olası bir plan değişikliğinde yerleşimlerin, en azından kirletici gazların kış mevsiminde ulaştığı üst seviye olan 1000-1100 m’nin üzerine kurulması aynı sorunların tekrar yaşanmamasını sağlayacaktır.
Air pollution is a well-known factor that affects the natural atmosphere when its concentration reaches a certain level. Additionally, a national act, the Air Quality Assessment and Management Regulation, has been introduced to establish minimum levels for smoke, dust, gas, vapor, and aerosol concentrations in the air (URL 1; URL 2). According to a recent report (THHP, 2021), PM10, PM2.5, SO2, O3, and NO2 values from 98% of 175 stations in Turkey were found to exceed the value (20 µg/m3) defined by the World Health Organization. Moreover, the air quality of some cities is more heavily influenced by urbanization, fossil fuel usage, and topographic and meteorological factors (Çiftçi et al., 2013). In Iğdır, geomorphological structures limit the horizontal movement of air parcels and create an inversion layer (Koç, 2018). However, there has been little quantitative analysis of air quality to guide urban growth in Iğdır. This study aims to address the lack of suitability analysis based on air quality and risk mapping in Iğdır. The suitability of urban growth will be analyzed using Google Earth Engine (GEE) data sets (NO2, SO2, CO, UV aerosol index [UVAI]), O3, Formaldehyde (HCHO), and ABL [Aerosol Boundary Layer]) with the Best–Worst Method (BWM).
Iğdır city center is situated at an average altitude of 850 m. The Iğdır Province is depicted in Figure 1. The Iğdır Plain was formed by the Aras River through alluvial deposition. The prevailing wind direction is over the depression of the Iğdır Plain. Figure 3 shows the frequency of annual winds. The geomorphological structure of the city provides benefits in terms of climate and agriculture.
Data for NO2, SO2, CO, UVAI, O3, HCHO, and ABL were obtained from Sentinel-5P TROPOMI (TROPOspheric monitoring instrument) in the GEE data collection. The data is collected by Landsat, MODIS, NOAA AVHRR, and ALOS remote sensing platforms (Amani et al., 2020). First, pollutant data was correlated to the city center via principal component analysis (PCA) to reveal risk fields. PCA is a linear analysis tool used to reduce a large raw data matrix to only its principal components (Tezbaşaran & Gelbal, 2018; Yi & Latch, 2022). Then, the pollutants were analyzed using one of the multivariate analysis techniques, the BWM. The BWM analysis indicated the suitability for urban growth. The closer the BWM result is to zero, the more reliable the data are (Badri Ahmadi et al., 2017).
The concentrations of six different pollutants were distributed throughout Iğdır. The concentration of NO2 ranged between 0.0000125 and 0.000032 mol/m2 . Figure 4 shows that the concentration is higher in the northern region of the city center and lower in the southern region, where the elevation is higher. SO2 production is typically caused by the use of fossil fuels, and the average concentration ranges between 0.0000219–0.000231 mol/m2 (Figure 4). High levels of SO2 were observed in low-lying areas. The distribution of CO concentrations followed a similar pattern to that of NO2 concentrations, with higher levels in the north and lower levels (0.0207–0.0316 mol/m2 ) in areas with higher elevation (Figure 4). The city center of Iğdır had higher values of HCHO, while the rest of the region exhibited values between 0.0000708 and 0.000131 mol/m2 (Figure 4). Although positive values of the aerosol index resulted in negative health effects, the area of interest did not show positive aerosol index values (−1.23, −0.488), as shown in Figure 4. Tropospheric ozone, which results from reactions with other pollutants in the atmosphere, exhibited a similar trend to NO2 and CO, being lower at higher elevations. Its concentration ranged between 0.1362–0.1394 mol/m2 (Figure 4). Aerosol height varied between 934–3020 m (Figure 10). The plain region of Iğdır represents the lowest aerosol layer height (934–1240 m) . Moreover, the height of the aerosol layer defines the highest level of particles in the atmosphere. Low aerosol layer height increases the risk of pollution evolution. Gaseous pollutants were found to be at their maximum during the winter (Figure 11). The highest wind speed in the region is approximately 1.4 m/s. The lack of wind throughout the year increases the air pollution.
Despite its small population, Iğdır suffers greatly from air pollution. The study shows that the city center and northern part of the plain are affected by pollution the most. Furthermore, height of the aerosol layer indicates the atmospheric vertical boundary for the pollutants. Thus, high pressure (917.8 hPa) in the atmosphere causes the pollutants to accumulate in the plain region. Due to the low temperatures (annual average is 12.2°C and lowest is −3.3°C), an inversion layer forms, thus limiting the movement of pollutants in the region. The air pollution risk map shows the highest risk in the northern part of the plain (Figure 13).
Based on this analysis, it can be inferred that a suitable urban growth area can be selected within the altitude range of 1000 to 1500 meters, as depicted in Figure 14. It is recommended that the settlement be located above the highest measured altitude for inversion and the aerosol layer, which is at 1100 meters (as shown in Figure 15).
