The contribution of Saharan dust in PM(10) concentration levels in Anatolian Peninsula of Turkey

The role of large-scale atmospheric circulations on long-term variations of PM10 concentrations over Turkey

PM10 is widely identified as an important atmospheric pollutant posing a serious threat to human health and environment as well as it influences the climate system. To unearth the mechanism involved in its sources and circulation behavior in environment, this study focuses on the role of large-scale atmospheric circulation on the long-term variability of PM10 over Turkey by applying rotated empirical orthogonal functions (REOF) analysis. As a result of the implementation of REOF to the daily PM10 data for 80 air quality stations throughout the period 2010-2020, first REOF mode (REOF1 44.9% in winter, 43.2% in spring, 39.5% in summer and 31.6% in fall) for all the four seasons indicated the role of local emission sources on the variations of PM10, which show high PM10 values in different geographical regions. The results of the second mode (REOF2, 17.9% in winter, 14.0% in spring, 14.0% in summer and 16.3% in fall) indicate the role of large-scale atmospheric circulations on the values of PM10. From the REOF2 analysis and extracted synoptic composite maps, the strength of southerly winds and the presence of southwesterly winds at low levels are very important in transporting of dust pollutants from the Arabian Peninsula and Northern Africa, respectively, to the eastern (EAR) and southeastern (SEAR) regions of Turkey during winter. In spring, sand particles in the interior terrestrial part of the country are carried to the northern regions by the effect of large-scale southerly winds, which cause above-normal PM10 concentrations in the Black Sea region of Turkey. In summer, dust particles together with warm dry air intrusion to the eastern region of Turkey by strong easterly winds are sourced by Caspian Sea and result in high PM10 values. Our findings emphasize that the long-term variations in air quality over Turkey are affected secondary by the variations in the large-scale atmospheric circulations with primary contributions from the changes in local emission sources.

Ambient air quality assessment at the airports based on a meteorological perspective

Natural mineral dust episodes elevate particle concentrations and eventually decrease air quality. Air pollutant emissions from aircraft, airport ground operations, and long-range dust transport are producing problems for the aviation sector. Dust transport from the Sahara Desert, one of the primary dust sources globally, significantly affects the eastern Mediterranean basin, including Türkiye. This study investigates the effect of long-range dust transport on particulate matter (PM) concentrations at Turkish airports. Three different approaches were used to analyse dust episodes in the study area. Firstly, routine reports of meteorological conditions at the airports were investigated. For this purpose, airport routine meteorological reports (Metar) and aviation-selected special weather report (Speci) codes, recorded at 11 airports from 2012 to 2021, were used to determine the dust episode days. Secondly, the hourly PM measurement dataset was analyzed from the closest air quality monitoring stations to the airports. Finally, regional atmospheric model results and backward-trajectory analysis were used to validate the dust episodes and determine the dust origin. Results showed that 163 dust episodes occurred during the study period, 17% from North Africa and 12% from the Mediterranean region.

The effect of military conflict zone in the Middle East on atmospheric persistent organic pollutant contamination in its north

This study aimed to investigate long-range atmospheric transport of selected POPs released due to the effects of military conflicts in regions to the south of Turkey's borders. Ten locations were selected to deploy passive air samplers at varying distances to the border on a southeast-west transect of the country, proximity-grouped as close, middle, and far. Sampling campaign included winter and transition months when desert dust transport events occur. Hypothesis of the study was that a decreasing trend would be observed with increasing distance to the border. Group comparisons based on statistical testing showed that PBDE-183, Σ₄₅PCB, and dieldrin in winter; PBDE-28, PBDE-99, PBDE-154, p,p'-DDE, Σ₁₄PBDE, and Σ₂₅OCP in the transition period; and PBDE-28, PBDE-85, PBDE-99, PBDE-154, PBDE-190, PCB-52, Σ₄₅PCB, p,p'-DDE, and Σ₂₅OCP over the whole campaign had a decreasing trend on the transect. An analysis of concentration ratio to the background showed that long-range atmospheric transport impacted the study sites, especially those of close group in comparison to the local sources. Back-trajectory analyses indicated that there was transport from the conflict areas to sites in the close-proximity group, while farther sampling locations mostly received air masses from Europe, Russia, and former Soviet Union countries, followed by North Africa, rather than the military conflict areas. In consequence, decrease in concentrations with distance and its relation to molecular weight through proportions, diagnostic ratios, analysis of concentration ratio to the background, and back-trajectory analyses support the effect of transport from the military-conflict area to its north.

Investigating the long-term trends in aerosol optical depth and its association with meteorological parameters and enhanced vegetation index over Turkey

Aerosol optical depth (AOD) provides useful information on particulate matter pollution at both regional and global levels. In this study, the long-term datasets of aerosols, meteorological parameters, and enhanced vegetation index (EVI) were used from September 2002 to December 2021 over Turkey. This study examined the spatiotemporal distribution of aerosols and their association with meteorological parameters (temperature (Temp), relative humidity (RH), wind speed (WS)), and EVI over Turkey from 2002 to 2021. Moreover, this study also performed a comparison of AOD retrieved from Aqua with other satellites (Terra, SeaWiFS, and MISR) and ground-based (AERONET) products. The higher mean seasonal AOD (> 0.3) was observed over Southeastern Anatolia Region due to the dust transport from the Saharan Desert and Arabian Peninsula. Moreover, AOD was positively correlated with Temp and WS in the east of Turkey, while negative correlations were observed in the coastal regions. The correlation between AOD and RH was also observed negative in most parts of Turkey. Furthermore, in the coastal region, the correlation between AOD and EVI was found to be positive, whereas a negative correlation was seen over less vegetative areas. The multi-seasonal AOD averages were calculated as 0.187, 0.183, 0.138, and 0.104 for the spring, summer, autumn, and winter seasons, respectively. The most important result of this study is the regional differences in AOD over Turkey. For new studies, AOD should be observed separately for coastal areas and the eastern part of Turkey.

A holistic approach to the air quality of Konya City, Turkey

Considering an integrated approach to assess all of the measured pollutants in a diurnal, monthly, seasonal, and annual time scales and understanding the mechanisms hidden under low air quality conditions are essential for tackling potential air pollution issues. Konya, located in central Anatolia, is the largest province of Turkey with a surface area of 40,838 km² and has different industrial activities. The lack of recent detailed studies limits our information on the underlying air pollution levels in Konya and obscuring policymakers to develop applicable mitigation measures. In this study, we used hourly monitored air quality data of CO, NO₂, NO_x, PM₁₀, PM_2.5, and SO₂ from five stations in Konya and investigated the temporal and spatial variabilities for the 2008–2018 period via statistical analysis. Upon analysis, particulate matter was found to be the dominant pollutant deteriorating the air quality of Konya. The highest 2008–2018 periodic mean value of PM₁₀ was found in Karatay Belediye as 70.5 µg/m³, followed by 67.4 µg/m³ in Meram, 58.7 µg/m³ in Selçuklu, and 43.7 µg/m³ in Selçuklu Belediye. The 24-h limit value of PM₁₀ given as 50 µg/m³ in the legislation was violated in all of the stations, mainly during winter and autumn. High positive correlations were found among the stations, and the highest correlation was obtained between Selçuklu Belediye and Karatay Belediye with a Pearson correlation coefficient of 0.77. Long-term data showed a decreasing trend in PM₁₀ concentrations. Diurnal variability is found to be more pronounced than weekly variability. For almost all of the pollutants, except for photochemical pollutants like O₃, a prominent result was the nighttime and morning rush hours high-pollutant levels. A case study done for the January 29, 2018 to February 05, 2018 episode showed the importance of meteorology and topography on the high levels of pollution. Limitation of the pollutant transport and dilution by meteorological conditions and the location of Konya on a plain surrounded by high hills are believed to be the main reasons for having low air quality in the region.

Vertical Structure of Dust Aerosols Observed by a Ground-Based Raman Lidar with Polarization Capabilities in the Center of the Taklimakan Desert

The vertical structure of dust properties in desert sources is crucial for evaluating their long-range transportation and radiative forcing. To investigate vertical profiles of dust optical properties in the Taklimakan Desert, we conducted ground-based polarization Raman lidar measurements in Tazhong (83.39°E, 38.58°N, 1103 m above sea level), located at the center of the Taklimakan Desert in the summer of 2019. The lidar system developed by Lanzhou University for continuous network observation is capable of measuring polarization at 532 and 355 nm and detecting Raman signals at 387, 407, and 607 nm. The results indicate that dust aerosols in the central Taklimakan Desert were regularly lifted over 6 km during the summer with a mass concentration of 400–1000 µg m−3, while the majority of the dust remained restricted within 2 km. Moreover, the height of the boundary layer can reach 5–6 km in the afternoon under the strong convention. Above 3 km, dust is composed of finer particles with an effective radius (Reff.) less than 3 μm and a Ångström exponent (AE) related to the extinction coefficient (AEE)532,355 greater than 4; below 3 km, however, dust is dominated by coarser particles. In addition, the particle depolarization ratios (PDR) of Taklimakan dust are 0.32 ± 0.06 at 532 nm and 0.27 ± 0.04 at 355 nm, while the lidar ratios (LRs) are 49 ± 19 sr at 532 nm and 43 ± 12 sr at 355 nm. This study firstly provides information on dust vertical structure and its optical properties in the center of the desert, which may aid in further evaluating their associated impacts on the climate and ecosystem.

Dust Climatology of Turkey as a Part of the Eastern Mediterranean Basin via 9-Year CALIPSO-Derived Product

Turkey is located in the heart of complex transition geography between Eurasia and the Middle East. In the grand scheme, the so-called eastern Mediterranean Basin is located almost in the middle of the dusty belt, and is a hot spot of climate change. The downstream location of dust-carrying winds from close desert sources reveals Turkey as an open plane to particulate matter exposure throughout the year. In order to clarify this phenomenon, this paper aims to determine the desert dust climatology of Turkey via CALIPSO onboard Lidar. This prominent instrument enables us to understand clouds, aerosols and their types, and related climatic systems, with its valuable products. In this study, a 9-year CALIPSO-derived pure dust product dataset was formed to explain horizontal and vertical distributions, transport heights and case incidences. The results indicated that the pure dust extinction coefficient increased as the location shifted from west to east. Moreover, in the same direction of west to east, the dominant spring months changed to summer and autumn. Mountain range systems surrounding Anatolia were the main obstacles against lofted and buoyant dust particles travelling to northern latitudes. Even if high ridges accumulated mass load on the southern slopes, they also enabled elevated particles to reach the ground level of the inner cities.

Characterization of atmospheric mechanisms that cause the transport of Arabian dust particles to the southeastern region of Turkey

The Southeastern Anatolia Region (SEAR), the third-lowest mean annual precipitation region in Turkey, has semi-arid climate and plateau characteristics. The proximity of the region to North Africa and the Middle East dust source areas enables long-range transport of desert dust particles toward the SEAR by strong winds. Among the other dust source regions, the Arabian Peninsula has a crucial role in terms of affecting the SEAR with a high-annual frequency and high dust concentration values. We investigated the atmospheric patterns of three extreme Arabian dust episodes that affect the SEAR in this study. Dust episodes were determined using present weather (SYNOP) codes of ten stations in the SEAR during the 2014-2019 period. The source regions were found using HYSPLIT backward trajectory analysis. In this study, we benefited from synoptic maps, in situ PM₁₀ observations, numerical simulations of the WRF-Chem model, and MODIS satellite images to analyze the extreme dust episodes. The results showed that the surface low pressure over the Persian Gulf and strong southerly winds at the 700-hPa level enabled the transport of dust particles from the surface to the mid-atmospheric levels. If the center of the upper-level ridge extended from Saudi Arabia to southern Turkey, the atmospheric blocking mechanism prevented the dispersion of dense dust particles from the SEAR to its surrounding, which caused the observation of high dust concentrations in the SEAR. In general, the WRF-Chem model outputs are in good agreement with ground-based PM₁₀ concentrations and MODIS true-color images in terms of temporal and spatial distributions of dust concentrations.

Particulate matter concentrations and their association with COVID-19-related mortality in Mexico during June 2020 Saharan dust event

The present study evaluated the impact of Saharan dust event on particulate matter (PM: PM₁₀ and PM_2.5) concentrations by analyzing the daily average PM data between Saharan dust days (June 23-29, 2020) and non-Saharan dust days (June 15 to June 22 and June 30 to July 12, 2020) for four majorly affected regions in Mexico and by comparing with three major previous events (2015, 2018, and 2019). The results showed that PM₁₀ and PM_2.5 concentrations were 2-5 times higher during the Saharan dust event with the highest daily averages of 197 μg/m³ and 94 μg/m³, respectively, and exceeded the Mexican standard norm (NOM-020-SSA1-2014). When comparing with the previous Saharan dust episodes of 2015, 2018, and 2019, the levels of PM₁₀ and PM_2.5 considerably increased and more than doubled across Mexico. The correlation analysis revealed a positive association of PM levels with the number of daily COVID-19 cases and deaths during Saharan dust event. Furthermore, the human health risk assessment showed that the chronic daily intake and hazard quotient values incremented during Saharan dust days compared to non-Saharan days, indicating potential health effects and importance of taking necessary measures to ensure better air quality following the COVID-19 pandemic.

PM events and changes in the chemical composition of urban aerosols: A case study in the western Mediterranean

More than 400 PM₁ and 400 PM₁₀ daily samples were collected in the urban center of Elche (close to the Spanish Mediterranean coast) from February 2015 to February 2018. Samples were analyzed to determine the concentrations of major and trace components with the aim of evaluating the influence of specific pollution events on the chemical composition of both PM fractions. The concentrations of crustal elements in PM₁₀ significantly increased during Saharan dust outbreaks, particularly titanium, which has been identified as a good tracer of these events in the study area. Sulfate and nitrate levels were also enhanced due to secondary aerosol formation on mineral dust particles. Local pollution episodes had a great impact on submicron nitrate, whose mean concentration was more than four times higher than on non-event days. The chemical mass closure method was used to reconstruct PM₁ and PM₁₀ concentrations. Reasonably good correlations between measured and reconstructed concentrations were obtained, except for PM₁₀ samples collected during Saharan dust events. This was due to the underestimation of the dust contribution during these episodes. Moderate differences in the average chemical composition of PM₁₀ were observed between event and non-event days. Regarding PM₁, only local pollution episodes had a certain impact on its chemical composition.

The influence of meteorological conditions and atmospheric circulation types on PM10 levels in western Turkey

High levels of atmospheric pollutants have been frequently measured in Turkey during the last decade. Specifically, the occurrence of these high particulate matter concentrations is often related to either local-scale conditions or regional-scale transport. In order to better understand the atmospheric factors that trigger poor air quality, further research investigating the relationship between air pollution and meteorological variables or atmospheric circulation patterns is needed. In this study, the influence of synoptic-scale weather types on PM₁₀ levels over the Aegean region of Turkey is investigated for the period 2008-2015. First of all, hourly PM₁₀ concentrations of 13 air quality stations are respectively converted to daily, seasonal, and regional averages. The seasonal variability of PM₁₀ values in the region indicates that high particulate matter concentrations are registered in winter, fall, spring, and summer months with mean values at 90.6 (± 38.3 standard deviation), 66.9 (± 28.3), 61.6 (± 23.4), and 54.1 (± 12.8) μg m^-3, respectively. In regard to the synoptic-scale approach, eight directional and two vorticity types of the Lamb weather type (LWT) method are used in the analysis. Based on the results, poor air quality conditions are observed in all seasons during active southeasterly (SE, interaction between a low pressure over Italy and a high pressure over the Caspian Sea) circulation types (CTs). In winter, mainly easterly (E), SE, southerly (S), and anticyclonic (A) weather patterns result in above normal PM₁₀ concentrations. In addition to these four CTs, southwesterly (SW) types also cause higher PM₁₀ values in the spring season. During summer, SE, SW, westerly (W), and cyclonic (C) CTs are associated with above-normal PM₁₀ values. During fall, obvious higher PM₁₀ concentrations are found during SE, S, and A types.

April 2008 Saharan dust event: Its contribution to PM10 concentrations over the Anatolian Peninsula and relation with synoptic conditions

An online-coupled regional Weather Research and Forecasting model with chemistry (WRF-Chem) is utilized incorporating 0.1°×0.1° spatial resolution HTAP (Hemispheric Transport of Air Pollution) anthropogenic emissions to investigate the spatial and temporal distribution of a Saharan dust outbreak, which contributed to high levels (>50μg/m³) of daily PM₁₀ concentrations over Turkey in April 2008. Aerosol optical depth and cloud optical thickness retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on board of Aqua satellite are used to better analyze the synoptic conditions that generated the dust outbreak in April 2008. A "Sharav" low pressure system, which transports the dust from Saharan source region over Turkey along the cold front, tends to move faster in WRF-Chem simulations than observed. This causes the predicted dust event to arrive earlier than observed leading to an overestimation of surface PM₁₀ concentrations in WRF-Chem simulation at the beginning of the event.

Spatiotemporal variability and contribution of different aerosol types to the Aerosol Optical Depth over the Eastern Mediterranean

This study characterizes the spatiotemporal variability and relative contribution of different types of aerosols to the Aerosol Optical Depth (AOD) over the Eastern Mediterranean as derived from MODIS Terra (3/2000-12/2012) and Aqua (7/2002-12/2012) satellite instruments. For this purpose, a 0.1° × 0.1° gridded MODIS dataset was compiled and validated against sunphotometric observations from the AErosol RObotic NETwork (AERONET). The high spatial resolution and long temporal coverage of the dataset allows for the determination of local hot spots like megacities, medium sized cities, industrial zones, and power plant complexes, seasonal variabilities, and decadal averages. The average AOD at 550 nm (AOD₅₅₀) for the entire region is ~ 0.22 ± 0.19 with maximum values in summer and seasonal variabilities that can be attributed to precipitation, photochemical production of secondary organic aerosols, transport of pollution and smoke from biomass burning in Central and Eastern Europe, and transport of dust from the Sahara Desert and the Middle East. The MODIS data were analyzed together with data from other satellite sensors, reanalysis projects and a chemistry-aerosol-transport model using an optimized algorithm tailored for the region and capable of estimating the contribution of different aerosol types to the total AOD₅₅₀. The spatial and temporal variability of anthropogenic, dust and fine mode natural aerosols over land and anthropogenic, dust and marine aerosols over the sea is examined. The relative contribution of the different aerosol types to the total AOD₅₅₀ exhibits a low/high seasonal variability over land/sea areas, respectively. Overall, anthropogenic aerosols, dust and fine mode natural aerosols account for ~ 51 %, ~ 34 % and ~ 15 % of the total AOD₅₅₀ over land, while, anthropogenic aerosols, dust and marine aerosols account ~ 40 %, ~ 34 % and ~ 26 % of the total AOD₅₅₀ over the sea, based on MODIS Terra and Aqua observations.

Spatiotemporal variability and contribution of different aerosol types to the Aerosol Optical Depth over the Eastern Mediterranean

This study characterizes the spatiotemporal variability and relative contribution of different types of aerosols to the Aerosol Optical Depth (AOD) over the Eastern Mediterranean as derived from MODIS Terra (3/2000-12/2012) and Aqua (7/2002-12/2012) satellite instruments. For this purpose, a 0.1° × 0.1° gridded MODIS dataset was compiled and validated against sunphotometric observations from the AErosol RObotic NETwork (AERONET). The high spatial resolution and long temporal coverage of the dataset allows for the determination of local hot spots like megacities, medium sized cities, industrial zones, and power plant complexes, seasonal variabilities, and decadal averages. The average AOD at 550 nm (AOD₅₅₀) for the entire region is ~ 0.22 ± 0.19 with maximum values in summer and seasonal variabilities that can be attributed to precipitation, photochemical production of secondary organic aerosols, transport of pollution and smoke from biomass burning in Central and Eastern Europe, and transport of dust from the Sahara Desert and the Middle East. The MODIS data were analyzed together with data from other satellite sensors, reanalysis projects and a chemistry-aerosol-transport model using an optimized algorithm tailored for the region and capable of estimating the contribution of different aerosol types to the total AOD₅₅₀. The spatial and temporal variability of anthropogenic, dust and fine mode natural aerosols over land and anthropogenic, dust and marine aerosols over the sea is examined. The relative contribution of the different aerosol types to the total AOD₅₅₀ exhibits a low/high seasonal variability over land/sea areas, respectively. Overall, anthropogenic aerosols, dust and fine mode natural aerosols account for ~ 51 %, ~ 34 % and ~ 15 % of the total AOD₅₅₀ over land, while, anthropogenic aerosols, dust and marine aerosols account ~ 40 %, ~ 34 % and ~ 26 % of the total AOD₅₅₀ over the sea, based on MODIS Terra and Aqua observations.