Aeolian dust deposition rates in south-western Iran

The annual atmospheric dust-load originating in the so-called Dust Belt ‎, which ranges from the ‎Sahara desert and the Arabian peninsula to the arid lowlands of Central Asia and the deserts of ‎northern China, impacts the air quality and the climate worldwide. Iran as a whole, and especially the ‎southwestern regions of the country, most affected by dust, with frequent dust storms characterized ‎by annual mean concentrations of more than 100 µg/m³ of suspended dust. Although aeolian dust is a ‎highly relevant problem in Iran, there is a lack of comprehensive regional studies on this topic. The ‎central aim of the study presented here is therefore the spatiotemporal analyses and classification of ‎dust events, the chemical composition of the dust, and the connections between regional and seasonal ‎climate variation and dust deposition rates in four sub-regions of Iran. This comprehensive approach is ‎based on the maximum mean dust concentration and the seasonality of dust events. The results are ‎provided new and valuable insights into the dust deposition and its related processes in the study area.‎ The study area covers 8.43% of Iran (about 117,000 km2), located between 45°30′00″ E 35°00′00″ N ‎and 49°30′00″ E 30°00′00″ N including Kermanshah, Lorestan and Khuzestan. The fieldwork area is ‎characterized by the rolling mountainous terrain about 4000 m above sea level (a.s.l) in the north and ‎east, plains and marshlands in the south. Study area has also located in dry climate and hot summer ‎conditions in the south, cold and hot desert climates in the west. The studies on aeolian dust in ‎southwestern Iran are based solely on ground deposition rates from 2014 to 2017‎‏.‏ To address the connections between the Ground observation of dust Deposition Rates (GDR), climate ‎zones, and weather patterns, a comparative analysis with various data sets was conducted. Both ‎gravimetric and directional dust samplers (10 each) were installed to record the monthly GDR between ‎‎2014 and 2017. The sampler design was deliberately kept simple to ensure long-term durability and ‎easy maintenance. The collected dust samples were analyzed for their chemical composition using ‎Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The ten sampling sites were also classified ‎by their land use / land cover (LULC) for a more detailed data interpretation. The observation data ‎during two typical dust cases (spring 2014 and winter 2015), have furthermore been compared with ‎the spatiotemporal dust concentration and dust load over the study area. Comparing the results of the ‎monthly mean Aerosol Optical Thickness (AOT) derived from the Moderate Resolution Imaging ‎Spectroradiometer (MODIS) and GDR data, using enhancement algorithms were applied in order to ‎investigate the spatiotemporal distribution of dust events. To demonstrate the aerosol movement, a ‎HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for tracing the ‎investigated dust events. The time-space consistency between AOT and GDR, in agreement with the ‎HYSPLIT model output was the basis for an improved estimation of the dust deposition rate from ‎separate thickness layers. Finally, by comparing the high temporal and maximum seasonal deposition ‎rates, using MODIS and GDR data, the impact of the regional climate on the deposition rates of ‎aeolian dust was assessed, which allows insights in potential future dust emission scenarios in times of ‎climate change. ‎ A major finding shows the impact of dust events on the environment and considers the influence of ‎geographical factors, such as weathering, and climate pattern over aeolian dust deposition rates. In ‎more detail, finding to address the first objective suggested that contributors of the elemental ‎concentrations are associated with elements emanating from local industrial and commercial activities ‎‎(Cr, V, and Cd). The dominant variables (K, Zn) strongly influence the aerosol composition values and ‎represent the dust transport route. Inter –element relationships shows that the highest proportion (80%) ‎of dust samples subjected to Airborne Metals Regulations are formed under local and regional ‎conditions. Besides, the analyses indicate that the WRF-Chem model adequately simulates the ‎evolution, spatial distribution and load of dust over the study area. Hence, the model performance has ‎been evaluated by GDR. It showed different values of GDR highly depending on LULC pattern. Due to ‎the fact, that there is no way to isolate each individual area from the effects of either anthropogenic ‎sources or natural weathering processes, developing guidance on the priorities of expanding projects ‎and preventative actions towards potential dust deposition from natural and dominant sources may be ‎a subject of institutional interest. ‎ The results of direct measurements of dust deposition, which are typically made by passive sampling ‎techniques (ground-based observations), along with analyzed data from AOT, represent the second ‎objective to understand the spatiotemporal pattern of the points with the same variation. The ‎corresponding points headed to find moving air mass trajectories, using HYSPLIT were proven to be a ‎discriminator of their local and regional origin of aeolian dust. Furthermore, the seasonal deposition rate ‎varied from 8.4 g/m2/month in the summer to 3.5 g/m2/month in the spring. Despite all the advances ‎of AOT, under certain circumstances, the ground-based solutions were able to represent aerosol ‎conditions over the research area, tested in the southwestern regions of Iran. And that is when the low ‎number of observations is a commonly acknowledged drawback of GDR.‎ In addition, the peak of the seasonal deposition rates (t/km2/month) occurred in [arid desert hot-BWh, ‎‎8.4], [arid steppe hot-BSh, 6.6], and [hot and dry summer-Csa, 3.5] climate regions. Thus, the third ‎objective response was‏ ‏detected as the highest deposition rates of dust BWh >BSh >Csa throughout ‎the year, once the annual mean deposition rates (t/km2/year) are 100.80 for [BWh], 79.27 for [BSh], ‎and 39.60 for [Csa]. The knowledge gained on the dust deposition processes, together with the ‎feedback from the climate pattern, will provide insights into the records of data for developing new ‎sources, deposition rates and their climate offsets. Taking this in mind, having information about the ‎ground deposition rates in the study region could make the estimations more accurate, while finding an ‎appropriate algorithm is necessary to enhance the affected areas exposed to the dust. In order to ‎assess the impact of dust events on human health, environment and the damage to the various ‎business sectors of the country’s economy, additional studies with adequate modelling tools are ‎needed. ‎ Due to this date, the data holding organizations are somewhat reluctant to make their data available to ‎other parties. This work is also a step toward an institutional suggestion to gain benefit from information ‎exchange amongst data holding organizations, providers and users. The need for capacity building and ‎strong policy for implementing user-friendly geo information portal‏ ‏is essential.

Investigation of Aeolian Dust Deposition Rates in Different Climate Zones of Southwestern Iran

Dust and atmospheric particles have been described in southwestern Iran primarily in terms of load, concentration and transport. The passive deposition, however, has been discussed inadequately. Therefore, the relationships between different climate zones in southwestern Iran and dust deposition rates were quantified between 2014 and 2017 using both space- (second modern-era retrospective analysis for research and applications, version 2 reanalysis model) and ground-based (eolian ground deposition rate) tools. In addition, the surface meteorological records, including the wind patterns favoring the occurrence of dust events, were examined. A hot desert climate (BWh), hot semi-arid climate (BSh), and temperate hot and dry summer climate (Csa) were identified as the three dominant climate regions in the study area, exhibiting the highest average dust deposition rates. In this study, correlations between the most relevant climate patterns and deposition rate weather parameters were found to describe a region’s deposition rate when a dust event occurred. Based on these results, the BSh and Csa regions were found to be associated with the seasonal cycle of dust events in March, April, and May, revealing that in the long run meteorological conditions were responsible for the varying dust deposition rates. Relatively, precipitation and temperature were the two major factors influencing dust deposition rates, not wind speed. Moreover, the peak seasonal deposition rates in the spring and summer were 8.40 t km−2 month−1, 6.06 t km−2 month−1, and 3.30 t km−2 month−1 for the BWh, BSh, and Csa climate regions, respectively. However, each of these climate types was directly related to the specific quantity of the dust deposition rates. Overall, the highest dust deposition rates were detected over the years studied were 100.80 t km−2 year−1, 79.27 t km−2 year−1, and 39.60 t km−2 year−1 for BWh, BSh, and Csa, respectively

Aeolian dust deposition rates in south-western Iran

The annual atmospheric dust-load originating in the so-called Dust Belt ‎, which ranges from the ‎Sahara desert and the Arabian peninsula to the arid lowlands of Central Asia and the deserts of ‎northern China, impacts the air quality and the climate worldwide. Iran as a whole, and especially the ‎southwestern regions of the country, most affected by dust, with frequent dust storms characterized ‎by annual mean concentrations of more than 100 µg/m³ of suspended dust. Although aeolian dust is a ‎highly relevant problem in Iran, there is a lack of comprehensive regional studies on this topic. The ‎central aim of the study presented here is therefore the spatiotemporal analyses and classification of ‎dust events, the chemical composition of the dust, and the connections between regional and seasonal ‎climate variation and dust deposition rates in four sub-regions of Iran. This comprehensive approach is ‎based on the maximum mean dust concentration and the seasonality of dust events. The results are ‎provided new and valuable insights into the dust deposition and its related processes in the study area.‎ The study area covers 8.43% of Iran (about 117,000 km2), located between 45°30′00″ E 35°00′00″ N ‎and 49°30′00″ E 30°00′00″ N including Kermanshah, Lorestan and Khuzestan. The fieldwork area is ‎characterized by the rolling mountainous terrain about 4000 m above sea level (a.s.l) in the north and ‎east, plains and marshlands in the south. Study area has also located in dry climate and hot summer ‎conditions in the south, cold and hot desert climates in the west. The studies on aeolian dust in ‎southwestern Iran are based solely on ground deposition rates from 2014 to 2017‎‏.‏ To address the connections between the Ground observation of dust Deposition Rates (GDR), climate ‎zones, and weather patterns, a comparative analysis with various data sets was conducted. Both ‎gravimetric and directional dust samplers (10 each) were installed to record the monthly GDR between ‎‎2014 and 2017. The sampler design was deliberately kept simple to ensure long-term durability and ‎easy maintenance. The collected dust samples were analyzed for their chemical composition using ‎Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The ten sampling sites were also classified ‎by their land use / land cover (LULC) for a more detailed data interpretation. The observation data ‎during two typical dust cases (spring 2014 and winter 2015), have furthermore been compared with ‎the spatiotemporal dust concentration and dust load over the study area. Comparing the results of the ‎monthly mean Aerosol Optical Thickness (AOT) derived from the Moderate Resolution Imaging ‎Spectroradiometer (MODIS) and GDR data, using enhancement algorithms were applied in order to ‎investigate the spatiotemporal distribution of dust events. To demonstrate the aerosol movement, a ‎HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for tracing the ‎investigated dust events. The time-space consistency between AOT and GDR, in agreement with the ‎HYSPLIT model output was the basis for an improved estimation of the dust deposition rate from ‎separate thickness layers. Finally, by comparing the high temporal and maximum seasonal deposition ‎rates, using MODIS and GDR data, the impact of the regional climate on the deposition rates of ‎aeolian dust was assessed, which allows insights in potential future dust emission scenarios in times of ‎climate change. ‎ A major finding shows the impact of dust events on the environment and considers the influence of ‎geographical factors, such as weathering, and climate pattern over aeolian dust deposition rates. In ‎more detail, finding to address the first objective suggested that contributors of the elemental ‎concentrations are associated with elements emanating from local industrial and commercial activities ‎‎(Cr, V, and Cd). The dominant variables (K, Zn) strongly influence the aerosol composition values and ‎represent the dust transport route. Inter –element relationships shows that the highest proportion (80%) ‎of dust samples subjected to Airborne Metals Regulations are formed under local and regional ‎conditions. Besides, the analyses indicate that the WRF-Chem model adequately simulates the ‎evolution, spatial distribution and load of dust over the study area. Hence, the model performance has ‎been evaluated by GDR. It showed different values of GDR highly depending on LULC pattern. Due to ‎the fact, that there is no way to isolate each individual area from the effects of either anthropogenic ‎sources or natural weathering processes, developing guidance on the priorities of expanding projects ‎and preventative actions towards potential dust deposition from natural and dominant sources may be ‎a subject of institutional interest. ‎ The results of direct measurements of dust deposition, which are typically made by passive sampling ‎techniques (ground-based observations), along with analyzed data from AOT, represent the second ‎objective to understand the spatiotemporal pattern of the points with the same variation. The ‎corresponding points headed to find moving air mass trajectories, using HYSPLIT were proven to be a ‎discriminator of their local and regional origin of aeolian dust. Furthermore, the seasonal deposition rate ‎varied from 8.4 g/m2/month in the summer to 3.5 g/m2/month in the spring. Despite all the advances ‎of AOT, under certain circumstances, the ground-based solutions were able to represent aerosol ‎conditions over the research area, tested in the southwestern regions of Iran. And that is when the low ‎number of observations is a commonly acknowledged drawback of GDR.‎ In addition, the peak of the seasonal deposition rates (t/km2/month) occurred in [arid desert hot-BWh, ‎‎8.4], [arid steppe hot-BSh, 6.6], and [hot and dry summer-Csa, 3.5] climate regions. Thus, the third ‎objective response was‏ ‏detected as the highest deposition rates of dust BWh >BSh >Csa throughout ‎the year, once the annual mean deposition rates (t/km2/year) are 100.80 for [BWh], 79.27 for [BSh], ‎and 39.60 for [Csa]. The knowledge gained on the dust deposition processes, together with the ‎feedback from the climate pattern, will provide insights into the records of data for developing new ‎sources, deposition rates and their climate offsets. Taking this in mind, having information about the ‎ground deposition rates in the study region could make the estimations more accurate, while finding an ‎appropriate algorithm is necessary to enhance the affected areas exposed to the dust. In order to ‎assess the impact of dust events on human health, environment and the damage to the various ‎business sectors of the country’s economy, additional studies with adequate modelling tools are ‎needed. ‎ Due to this date, the data holding organizations are somewhat reluctant to make their data available to ‎other parties. This work is also a step toward an institutional suggestion to gain benefit from information ‎exchange amongst data holding organizations, providers and users. The need for capacity building and ‎strong policy for implementing user-friendly geo information portal‏ ‏is essential.

Determination of dust sources by analyzing the elements correlation within the dust

The southwestern and western provinces of Iran are heavily affected by aeolian dust deposition. Besides the results of weathering, soil formation processes and the elemental composition of soil surfaces are influenced by aeolian dust transport and deposition. In most cases, the source areas of the dust are not clear. After Geiger and Cooper (2010) it is possible to conclude the dust source areas from the dust elemental composition. Therefore this study’s objective is to analysis the elemental composition of dust samples, and the elemental correlations of 10 dust sampling stations in the southwestern Iran for the determination of the dust source areas. To begin with: monthly dust samples including event frequencies were collected in the south and west of Iran. As one might expect, the element concentration was determined using inductively coupled plasma mass spectrometry (ICP-MS). Dust event frequency (DEF) was recorded of course based on its reduction of visibility in the air and the CCME standard for particulate matter 2.5 (<1000m visibility and PM2.5). Accordingly, the associations of daily data recorded from dust events frequency (DEF) together with result from the ICP-MS have been discussed. After all, Strong correlations were detected between the Site deposition level (SDL) and the DEF in in the south and west, except one in L06 with a lack of associations. In brief, the positive correlation between DEF and classified elements was significant (P<0.05) for Na, Mg in a “geologic group”, Zn in an organic group Ni, Mg in an industry group and Cd, Pb in the group of smelting plants. Moreover, strong negative correlation have been observed from the same classification for Si, Ca, Sr in a “geologic group”, Cr in an industry group, and As, Pb in a smeltery group. In particular, elements from the organic group had no negative correlation with DEF. To sum up, high correlation values indicate hazards from deposition sources in large scale. The findings also suggest that the major contributors of V, Cr, Co, Ni, Cu, Zn, As, Se, Cd, Ba and Pb in elemental concentration may depend upon meteorological and dominant variables and the pretty much conversation between