This study evaluates the bioaccessibility and health risks related to heavy metals (Cd, Cr, Co, Cu, Mn, Ni, Pb, Zn and metalloid As) in airborne dust samples (TSP and PM2.5) in Zabol, Iran during the ...summer dust period, when peak concentration levels of PM are typically observed. High bioaccessibilities of carcinogenic metals in PM2.5 (i.e. 53.3%, 48.6% and 47.6% for Ni, Cr and As, respectively) were calculated. The carcinogenic and non-carcinogenic health risks were assessed for three exposure pathways (inhalation, ingestion and dermal contact), separately for children and adults. Non-carcinogenic inhalation risks were very high (Hazard Index: HI > 1) both for children and adults, while the carcinogenic risks were above the upper acceptable threshold of 10−4 for adults and marginally close (5.0–8.4 × 10−5) for children. High carcinogenic risks (>10−4) were found for the ingestion pathway both for children and adults, while HI values > 1 (8.2) were estimated for children. Carcinogenic and non-carcinogenic risk estimates for dermal contact were also above the limits considered acceptable, except for the carcinogenic risk for children (7.6 × 10−5). Higher non-carcinogenic and carcinogenic risks (integrated for all elements) were associated with the inhalation pathway in adults and children with the exception of carcinogenic risk for children, where the ingestion route remains the most important, while As was linked with the highest risks for nearly all exposure pathways. A comparative evaluation shows that health risks related with toxic elements in airborne particles in Sistan are among the highest reported in the world.
•Severe concentration levels of As and heavy metals in airborne dust in Zabol.•Large bioaccessibility fractions (∼50%) for carcinogenic elements Ni, Cr, Cd, As.•Carcinogenic and non-carcinogenic risks was very higher than acceptable thresholds.•The inhalation pathway, and As, Cr exposures are associated with the highest risks.
Dust storms are frequent phenomena in Khuzestan Province, southwest Iran, leading to environmental hazards and deleterious impacts on human health. This work analyzes mineralogic and geochemical ...characteristics of dust sediments at the source regions and in deposition areas in southwest Iran during three dust-storm events in winter and spring 2018. Twenty soil and airborne dust samples were collected and analyzed for compositions of dust at different distances from the source regions in Iraq and southwest Iran, aiming to assess the source characterization and possible mixing processes in the atmosphere. The grain size distributions were also analyzed at specific sites. The results show that about 50 % of the volume size distribution corresponds to particle sizes of above 20 μm, indicating local/regional dust storms of coarse to giant particles. XRD analysis indicates that calcite is the dominant mineral in all the samples, with a high quartz and dolomite fraction. The most abundant major compounds are SiO2 and CaO, while Cl, Ba, Sr, Pb, Ni, Zn, Cr, V are the main trace elements. The enrichment factor (EF) analysis showed that apart from Th, Nb, Ce, and V, all the other elements (Pb, Zn, Cr, etc.) have an anthropogenic origin or represent high amounts of pollutant contamination. High levels of elemental enrichment are attributable to intensive pollution in Khuzestan Province and at sampling sites due to fossil-fuel combustion, gas and petroleum drilling activities. Moreover, based on the geo-accumulation index (Igeo), all samples are found to be contaminated by heavy metals due to prior war-related materiel, oil and gas extraction, and emissions from polluting industries.
•Coarse to giant particles indicate local/regional dust storms.•Calcite is the dominant mineral with important quartz and dolomite fractions.•Enrichment factor analysis reveals high anthropogenic contamination of dust samples.•Soil samples are contaminated by heavy metals due to war, oil and gas extraction industries.
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•Pronounced seasonal variation in aerosol absorption in Athens over a 4-year period.•Significant BrC contribution (23.7%) to the total aerosol absorption at 370 nm.•Strong winter-time ...correlations between BrC and BB-related organic aerosols.•The BrCsec absorption is related to residential wood burning during winter nights.
This study analyses 4-years of continuous 7-λ Aethalometer (AE-33) measurements in an urban-background environment of Athens, to resolve the spectral absorption coefficients (babs) for black carbon (BC) and brown carbon (BrC). An important BrC contribution (23.7 ± 11.6%) to the total babs at 370 nm is estimated for the period May 2015–April 2019, characterized by a remarkable seasonality with winter maximum (33.5 ± 13.6%) and summer minimum (18.5 ± 8.1%), while at longer wavelengths the BrC contribution is significantly reduced (6.8 ± 3.6% at 660 nm). The wavelength dependence of the total babs gives an annual-mean AAE370-880 of 1.31, with higher values in winter night-time. The BrC absorption and its contribution to babs presents a large increase reaching up to 39.1 ± 13.6% during winter nights (370 nm), suggesting residential wood burning (RWB) emissions as a dominant source for BrC. This is supported by strong correlations of the BrC absorption with OC, EC, the fragment ion m/z 60 derived from ACSM and PMF-analyzed organic fractions related to biomass burning (e.g. BBOA). In contrast, BrC absorption decreases significantly during daytime as well as in the warm period, reaching to a minimum during the early-afternoon hours in all seasons due to photo-chemical degradation. Estimated secondary BrC absorption is practically evident only during winter night-time, implying the fast oxidation of BrC species from RWB emissions. Changes in mixing-layer height do not significantly affect the BrC absorption in winter, while they play a major role in summer.
► Sistan in southeast of Iran, has extensive wind erosion with intense dust storms. ► Quartz, calcite, muscovite and plagioclase are main mineralogical components of dust. ► SiO2, CaO, Al2O3, Na2O, ...MgO and Fe2O3 are major elements of dust. ► Mineralogy and chemical compositions of airborne dust are similar to soil samples. ► Dust has rounded irregular, prismatic and rhombic shapes, with only finer particles.
Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. Sistan is a region located in southeast Iran with extensive wind erosion, severe desertification and intense dust storms, which cause adverse effects in regional air quality and human health. To mitigate the impact of these phenomena, it is vital to ascertain the physical and chemical characteristics of airborne and soil dust. This paper examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol samples at two stations established close to a dry-bed lake dust source region, from August 2009 to August 2010. Furthermore, soil samples were collected from topsoil (0–5cm depth) at several locations in the dry-bed Hamoun lakes and downwind areas. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. X-ray Diffraction (XRD) analysis of airborne and soil dust samples shows that the dust mineralogy is dominated mainly by quartz (30–40%), calcite (18–23%), muscovite (10–17%), plagioclase (9–12%), chlorite (∼6%) and enstatite (∼3%), with minor components of dolomite, microcline, halite and gypsum. X-ray Fluorescence (XRF) analyses of all the samples indicate that the most important oxide compositions of the airborne and soil dust are SiO2, CaO, Al2O3, Na2O, MgO and Fe2O3, exhibiting similar percentages for both stations and soil samples. Estimates of Enrichment Factors (EFs) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes lying to the north of Sistan.
Aerosol emissions from biomass burning are of specific interest over the globe due to their strong radiative impacts and climate implications. The present study examines the impact of paddy crop ...residue burning over northern India during the postmonsoon (October–November) season of 2012 on modification of aerosol properties, as well as the long‐range transport of smoke plumes, altitude characteristics, and affected areas via the synergy of ground‐based measurements and satellite observations. During this period, Moderate Resolution Imaging Spectroradiometer (MODIS) images show a thick smoke/hazy aerosol layer below 2–2.5 km in the atmosphere covering nearly the whole Indo‐Gangetic Plains (IGP). The air mass trajectories originating from the biomass‐burning source region over Punjab at 500 m reveal a potential aerosol transport pathway along the Ganges valley from west to east, resulting in a strong aerosol optical depth (AOD) gradient. Sometimes, depending upon the wind direction and meteorological conditions, the plumes also influence central India, the Arabian Sea, and the Bay of Bengal, thus contributing to Asian pollution outflow. The increased number of fire counts (Terra and Aqua MODIS data) is associated with severe aerosol‐laden atmospheres (AOD500 nm > 1.0) over six IGP locations, high values of Ångström exponent (>1.2), high particulate mass 2.5 (PM2.5) concentrations (>100–150 µgm−3), and enhanced Ozone Monitoring Instrument Aerosol Index gradient (~2.5) and NO2 concentrations (~6 × 1015 mol/cm2), indicating the dominance of smoke aerosols from agricultural crop residue burning. The aerosol size distribution is shifted toward the fine‐mode fraction, also exhibiting an increase in the radius of fine aerosols due to coagulation processes in a highly turbid environment. The spectral variation of the single‐scattering albedo reveals enhanced dominance of moderately absorbing aerosols, while the aerosol properties, modification, and mixing atmospheric processes differentiate along the IGP sites depending on the distance from the aerosol source, urban influence, and local characteristics.
Key Points
Satellite and ground‐based monitoring of agriculture fires in northern India
Transport pathways, smoke plume characteristics, and affected areas
Variation of aerosol loading as a function of distance from the source
This study focuses on analyzing the extreme aerosol loading and the mechanisms, source areas and meteorological conditions that favored the abnormal dust exposure towards Arabian Sea during June ...2008. The analysis reveals that the spatial-averaged aerosol optical depth (AOD) over Arabian Sea in June 2008 is 0.5 (78.2%) higher than the 2000–2013 mean June value and is mostly attributed to the enhanced dust activity and several (18) dust storms originated from the Sistan region (Iran–Afghanistan borders). Landsat images show that the marshy lakes in Sistan basin got dried during the second half of June 2008 and the alluvial silt and saline material got easily eroded by the intense Levar winds, which were stronger (>15–20 m s−1) than the climatological mean for the month of June. These conditions led to enhanced dust exposure from Sistan that strongly affected the northern and central parts of the Arabian Sea, as forward air-mass trajectories show. The NCEP/NCAR reanalysis reveals an abnormal intensification and spatial expansion of the Indian low pressure system towards northern Arabian Sea in June 2008. This suggests strengthening of the convection over the arid southwest Asia and exposure of significant amount of dust, which can reach further south over Arabian Sea favored by the enhanced cyclonic circulation. MODIS imagery highlighted several dust storms originated from Sistan and affecting Arabian Sea during June 2008, while the SPRINTARS model simulations of increased AOD and dust concentration over Sistan and downwind areas are in agreement with ground-based and satellite observations.
•The high AOD over Arabian Sea in June 2008 is mostly attributed to Sistan dust storms.•The role of the Sistan basin in dust aerosol loading over Arabian Sea.•The Hamoun lakes and the Levar wind play a major role in enhancement of dust activity.•The intensity of the cyclonic circulation over Arabian Sea favored the dust exposure.
The present work analyzes the aerosol episode (AE) days and examines the modification in aerosol properties and radiative forcing during the period 2001–2010 based on Kanpur-AERONET data. AEs are ...defined as the days having daily-mean aerosol optical depth (AOD) above the decadal mean + 1 STD (standard deviation); the threshold value is defined at 0.93. The analysis identifies 277 out of 2095 days (13.2%) of AEs over Kanpur, which are most frequently observed during post-monsoon (78 cases, 18.6%) and monsoon (76, 14.7%) seasons due to biomass-burning episodes and dust influence, respectively. On the other hand, the AEs during winter and pre-monsoon are lesser in both absolute and percentage values (65, 12.5% and 58, 9.1%, respectively). The modification in aerosol properties on the AE days is strongly dependent on season; during post-monsoon and winter, the AEs are associated with enhanced presence of fine-mode aerosols from anthropogenic emissions and/or biomass burning, while during pre-monsoon and monsoon seasons, they are mostly associated with dust. Aerosol radiative forcing (ARF) calculated using SBDART shows much more surface (∼−69 to −97 Wm−2) and Top of Atmosphere cooling (−20 to −30 Wm−2) as well as atmospheric heating (∼43 to 71 Wm−2) during the AE days as compared to seasonal means. These forcing values are mainly controlled by the higher AODs and the modified aerosol characteristics (Angstrom Exponent α, single scattering albedo SSA) during the AE days in each season. Furthermore, the vertical profiles of aerosols and atmospheric radiative heating exhibit significant increase in lower and mid troposphere during the AE days. This may cause serious climate implications over Ganges Basin and surrounding regions with further consequences on cloud microphysics, monsoon rainfall and melting of Himalayan glaciers.
•Studying the seasonal and inter-annual variation of the aerosol episodes (AE) over Kanpur, central IGP, India.•The AE days are associated with accumulation of anthropogenic aerosols and biomass burning during post-monsoon and winter.•The AE days are strongly related to dust presence during pre-monsoon and monsoon.•The optical and physical properties of aerosols significantly are modifying during the AE days, also depending on season.•The aerosol radiative forcing at surface, TOA and within the atmosphere is considered very high during the AE days.
This work investigates the modulation in dust activity over southwest (SW) Asia attributed to changes in the mean sea level pressure (MSLP) between the Caspian Sea (CS) and Hindu Kush (HK) during the ...summer months (June–July–August–September, JJAS) of the period 2000–2014. The MSLP anomalies obtained via NCEP/NCAR re-analysis are evaluated via a new climatology index, the Caspian Sea–Hindu Kush Index (CasHKI), which is defined as CasHKI=MSLPanom.CS−MSLPanom.HK, over specific domains taken over the CS and HK. The changes in CasHKI intensity are examined against dust activity and rainfall distributions over south Asia. The satellite remote sensing (Meteosat, OMI, MODIS) analyses show that high CasHKI values corresponding to enhanced pressure gradient between the CS and the HK, are associated with intensification of northerly winds, increased dust emissions and transportation over SW Asia and north Arabian Sea. In contrast, variations in CasHKI intensity do not seem to have a significant effect on the Indian summer monsoon. Only a slight decrease of precipitation over the southern Indian peninsula and the neighboring oceanic areas and an increase of precipitation along the Ganges Basin and Himalayan range are found to be related to high CasHKI values. Model (MIROC-SPRINTARS) simulations of dust concentration and dust AOD (Aerosol Optical Depth) over SW Asia are consistent with the satellite observations, highlighting for the first time the modulation of the SW Asian dust activity by CasHKI.
•The CasHKI as a key parameter of SW Asia climate•Changes in CasHKI intensity affect the wind field over SW Asia.•High CasHKI values govern intense north winds and dust emissions over SW Asia.•Increased dust outflow over north Arabian Sea under high CasHKI intensity.•Limited effect of CasHKI variations on the summer monsoon rainfall
This study examines the spectral properties and source characteristics of absorbing aerosols (BC: Black Carbon; BrC: Brown Carbon, based on aethalometer measurements) in the urban background of ...Athens during December 2016–February 2017. Using common assumptions regarding the spectral dependence of absorption due to BC (AAEBC = 1) and biomass burning (AAEbb = 2), and calculating an optimal AAEff value for the dataset (1.18), the total spectral absorption was decomposed into five components, corresponding to absorption of BC and BrC from fossil-fuel (ff) combustion and biomass burning (bb), and to secondary BrC estimated using the BC-tracer minimum R-squared (MRS) method. Substantial differences in the contribution of various components to the total absorption were found between day and night, due to differences in emissions and meteorological dynamics, while BrC and biomass burning aerosols presented higher contributions at shorter wavelengths. At 370 nm, the absorption due to BCff contributed 36.3% on average, exhibiting a higher fraction (58.1%) during daytime, while the mean BCbb absorption was estimated at 18.4%. The mean absorption contributions due to BrCff, BrCbb and BrCsec were 6.7%, 32.3% and 4.9%, respectively. The AbsBCff,370 component maximized during the morning traffic hours and was strongly correlated with NOx (R2 = 0.76) and CO (R2 = 0.77), while a similar behavior was seen for the AbsBrCff,370 component. AbsBCbb and AbsBrCbb levels escalated during nighttime and were highly associated with nss-K+ and with the organic aerosol (OA) components related to fresh and fast-oxidized biomass burning (BBOA and SV-OOA) as obtained from ACSM measurements. Multiple linear regression was used to attribute BrC absorption to five OA components and to determine their absorption contributions and efficiencies, revealing maximum contributions of BBOA (33%) and SV-OOA (21%). Sensitivity analysis was performed in view of the methodological uncertainties and supported the reliability of the results, which can have important implications for radiative transfer models.
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•New approach to apportion BC - BrC absorption from biomass and fossil fuel burning•Combination of “Brown Carbon” and “Aethalometer” models in winter data in Athens•Biomass burning is the dominant nighttime BrC absorption source at 370–660 nm.•In daytime, traffic controls BC absorption and also affects near-UV BrC absorption.•Regressing BrC on ACSM PMF-resolved OA components provides their MAE and AAE values.
This study examines the influence of changes in the water coverage in the Hamoun dry-bed lakes on visibility, dust outbreaks, aerosol loading and land–atmospheric fluxes over the region covering the ...period 1985–2005. The Hamoun basin, located on the southeastern Iran and western Afghanistan borders, has been recognized as one of the major dust source regions in south Asia and is covered by shallow, marshy lakes that are fed by the Helmand and Farahrood rivers. When the water in watersheds that support the lakes is drawn down for natural or human-induced reasons, the end result is a decrease in the water coverage in the basin, or even complete dryness as occurred in 2001. Then, strong seasonal winds, mainly in summer, blow fine sand and silt off the exposed lakebed, enhancing dust activity and aerosol loading over the region. Satellite (Landsat) and meteorological observations reveal that the water levels in the Hamoun lakes exhibit considerable inter-annual variability during the period 1985–2005 strongly related to anomalies in precipitation. This is the trigger for concurrent changes in the frequency of the dusty days, aerosol loading and deterioration of visibility over the region, as satellite (TOMS, MODIS, MISR) observations reveal. On the other hand, soil moisture and latent heat, obtained via model (GLDAS_noah-10) simulations are directly linked with water levels and precipitation over the region. The desiccation of the Hamoun lakes in certain years and the consequent increase in frequency and intensity of dust storms are serious concerns for the regional climate, ecosystems and human health.
•Understanding the role of Land Use.•Land Cover changes and precipitation variability in dust emissions over Sistan, Iran.•Effect of dryness of ephemeral lakes on dust storm activity, visibility and aerosol loading.•Effect of dryness of ephemeral lakes on land-atmosphere fluxes.•Satellite monitoring of variability in lakes surface.
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