Natural Dust Sources Research Articles

Iron dissolution from Patagonian dust in the Southern Ocean: under present and future conditions

Although the input of desert dust as a key source of trace metals in the Southern Ocean (SO) has been previously studied, the dissolution process of metals in surface waters, particularly iron (Fe), remain poorly understood. Given the crucial role of Fe in primary production and the biological carbon pump in the SO, we focused on experimental estimations of Fe dissolution from Patagonian dust, the primary natural dust source in the SO. Our study considered both current and projected future conditions, encompassing sea-surface warming, acidification, increased photosynthetically active radiation, and doubled dust inputs. Through controlled laboratory experiments using filtered SO seawater, conducted over 7 days, we assessed changes in particulate Fe (pFe) concentrations, Fe redox speciation (Fe(II)/Fe(III)), and in the mineralogy of Fe-bearing dust in abiotic condition. The predominant minerals in the dust included quartz and aluminosilicates, with silicon (Si), aluminum (Al), and Fe as the major elements. No significant alterations in the mineralogy and the elemental composition of the dust were recorded during the dissolution experiments, neither under present nor under projected future conditions. The particulate Fe(II)/Fe(III) ratio remained consistently at 0.25 during the experiments, unaffected by changed conditions. Consequently, changes in environmental conditions in the SO would therefore not significantly alter the mineralogy and redox speciation of pFe in the Patagonian dust. On the contrary, pFe exhibited a dissolution rate of 3.8% and 1.6% per day under present and future conditions, respectively. The environmental changes anticipated for 2100 in the SO will likely to result in a decrease in the dissolution rate of pFe. Thus, even though a doubling of dust input by 2100 is anticipated, it will unlikely provide significantly more dissolved Fe (dFe) in seawater in the SO. Consequently, the future intensification of Patagonian dust inputs may not alleviate the Fe limitation in the SO.

Quantifying the contributions of natural and anthropogenic dust sources in Shanxi Province, northern China

Dust storms have direct or indirect impacts on climate change and human health. Identifying and quantifying natural/anthropogenic dust sources can facilitate effective prevention and control of dust events. Based on surface real-time PM10 monitoring data, satellite remote sensing and the HYSPLIT model, this study determined the specific timing, coverage and sources of dust events in Shanxi Province, Northern China. Thus, a composite fingerprinting technique was established to quantify potential dust sources and dust contributions of single dust events. The dust oxidation model was validated, indicating that the composite fingerprinting technique was well suited to the study region. The results show that natural dust sources (67%) contributed more to the study region than anthropogenic dust sources. They were mainly from the northwest and north of the study region. Particularly, the contributions of Taiyuan (TY) and Linfen (LF) accounted for the largest (82%) and smallest (55%) proportions, respectively, both exceeding 50%. Anthropogenic dust sources contributed 33%, mainly from the east and south of the study region. The contribution of anthropogenic dust sources increased in the study region from north to south. In terms of potential dust sources, the Tengger Desert and Badain Jaran Desert (TDBD) contributed the most (26%), followed by the Otindag Sandy Land (OL) (22%). The Taklimakan Desert (TD) contributed the least (2%). The Middle Farmland region of the Hexi Corridor (HMF) in the west (15%) had the largest proportion of anthropogenic dust sources. Differences in the regional contribution of potential dust sources mainly resulted from winter winds, surface drought severity and particle size. At an insignificant distance from the study region, the contribution of potential dust sources was larger in the west than in the east and increased from south to north overall. These methods and findings can contribute to improving the ecological environment in Northern China.

Identification of natural and anthropogenic sources and the effects of climatic fluctuations and land use changes on dust emissions variations in the Qinghai-Tibetan Plateau

Human activity in modulating dust emissions is one of the major causes of large uncertainties in the global dust budget. However, the division of natural and anthropogenic dust sources remains controversial, and the natural and anthropogenic effects on the variations in dust emissions were hardly distinguished. To bridge these gaps, a model was employed to simulate the dust emission processes over the Qinghai-Tibetan Plateau (QTP) whose dust yield remains uncertain. Integrating the Human Activity Intensity (HAI) dataset, the natural and anthropogenic dust sources were identified. By combining the different scenarios of land use and climate, the dust emission processes under 15 scenarios from 1982 to 2020 were simulated, and the effects of climatic fluctuations (CF) and land use changes (LUC), which were roughly recognized as the natural and anthropogenic effects, respectively, on the variations in dust emissions were distinguished. The results showed that the annual dust emission quantities ranged from 41.12 to 240.68 Tg/a during the period. The natural dust sources (NDSs) and anthropogenic dust sources (ADSs) occupied an average of 13.30% and 59.77% of the total area of the QTP, respectively, and their contributions to the total dust emissions of the QTP were 8.11% and 91.89%, respectively. During these decades, the CF had an obvious trend of restraining dust emissions, while the effects of LUC promoted dust emissions, and after 2000, the promoted effect slowed down. Overall, the effects of LUC on dust emissions were slightly larger than those of CF. From the perspective of dust emission variations, we discussed the anthropogenic disturbance on the ecosystems of the QTP. We believe the study method can provide valuable references for identifying natural and anthropogenic sources and quantifying the effects of natural and anthropogenic factors on dust emission variations, and the results can reduce the uncertainty of the global dust budget.

Application of Kolmogorov-Zurbenko filter to quantify the long-term meteorological and emission impacts on air quality

High concentrations of Particulate Matter (PM) have become a major problem in Turkey because of its economic development over the past decades, as well as its geographical proximity to natural dust source areas. In this study, PM10 data (for the period of 2010–2020) of 36 ground-based stations in 12 metropolitan cities over different regions in Turkey was used and Kolmogorov-Zurbenko (KZ) filter was implemented to decompose the data into its temporal components. A stepwise Multiple Linear Regression (MLR) model was developed to establish relationships between PM10 concentrations and a set of meteorological variables for each city to quantify the long-term meteorological as well as emission impacts on changes and trends in air quality. In this study analysis has revealed that out of twelve major cities in Turkey, only three of them has PM10 levels below or around 45 μgm−3,which is 24 h Air Quality Guideline (AQG) level identified by WHO (WHO, 2021). Overall, over the selected period, long-term change in PM10 concentration is negative for 10 out of 12 cities, ranging between −39.6 μgm−3 and −1.2 μgm−3. Only Adana and Kayseri have a positive long-term change ranging between 1.0 μgm−3 and 3.1 μgm−3. Long-term change in meteorology related component (χLTmet) is relatively constant, hence, long-term change in PM10 concentration (χLT) is heavily influenced by emission related component (χLTemis). As emission impact reduces over time, there is a decrease in PM10 levels in most of the cities. This finding is further supported by reductions in national emissions data.

Overestimation of anthropogenic contribution of heavy metals in precipitation than those of aerosol samples due to different treatment methods

Due to increased anthropogenic activities in recent decades, many heavy metal elements have been emitted into the atmosphere and transported to remote regions. The Enrichment factors (EFs) is a normally used method for evaluating the source of heavy metal elements. However, because of some flaws of this method (e.g., higher solubility of heavy metals elements than reference elements in dilute acid), the anthropogenic contributions of some heavy metal elements in the precipitation sample were overestimated. To address this issue, EFs of heavy metal elements of aerosol, precipitation and snowpit samples in a typical remote area of the Tibetan Plateau (TP) were compared. The results showed that the EF values of many heavy metal elements in precipitation and snowpit samples were close to that of aerosol samples treated with dilute acid but usually much higher than those of totally dissolved aerosol samples. Moreover, EF values of most heavy metal elements in the ice core at the margin of the TP were higher than those at central TP, indicating that signal of long-range transport anthropogenic emitted heavy metal elements is weak and may be covered by natural mineral dust sources at glacier region. Therefore, the threshold EF values for determining anthropogenic sources of heavy metal elements in precipitation and ice core samples should be higher than those of aerosols. This study provides new knowledge on investigating anthropogenic sources of heavy metals in precipitation samples at both the TP and other regions of the world.

Field Portable X-Ray Fluorescence (pXRF) Spectrometry for Chemical Dust Source Characterization: Investigations of Natural and Mining-Related Dust Sources in Greenland (Kangerlussuaq Area)

In this study, we evaluate the use of field portable X-ray fluorescence (pXRF) as a screening tool for dust source characterisation at two sites in Greenland, a natural site near Kangerlussuaq influenced by dust generated by the Greenland Ice Sheet and an anorthosite mine site located 80 km from Kangerlussuaq. Measurements of ground surface samples were done ex-situ in LDPE plastic bags and in-situ at selected locations. Ex-situ measurements were done both before and after drying of samples to evaluate the effect of water content. Further, the effect of XRF cup films and LDPE bag walls was measured to enable element-specific corrections for signal attenuation of the pXRF measurements. Accuracy and precision were evaluated using a matrix blank and three different soil certified reference materials (CRMs). Finally, pXRF data from the two sites were analysed statistically by principal component analysis (PCA) and linear discriminant analysis (LDA) for the purpose of discriminating between dust sources. The pXRF results showed detectable concentrations of the elements: Al, Si, K, Ca, Fe, Sr, Zr and Ba in all samples (and P, Mn, Zn, Rb, Y, Nb, Ta, Pb and Th in some samples). Moreover, the results showed good accuracies for 21 elements in the CRMs. The PCA/LDA plots based on the pXRF data provided a good tool to discriminate between natural and mining-related dust sources and also between some specific mining-related sources. Altogether, this demonstrates that pXRF combined with multivariate statistics can be an adequate tool for fast cost-effective dust source characterisation.

Gone with the Wind: Microbial Communities Associated with Dust from Emissive Farmlands.

Dust is a major vehicle for the dispersal of microorganisms across the globe. While much attention has been focused on microbial dispersal in dust plumes from major natural dust sources, very little is known about the fractionation processes that select for the "dust microbiome." The recent identification of highly emissive, agricultural land dust sources in South Africa has provided the opportunity to study the displacement of microbial communities through dust generation and transport. In this study, we aimed to document the microbial communities that are carried in the dust from one of South Africa's most emissive locations, and to investigate the selective factors that control the partitioning of microbial communities from soil to dust. For this purpose, dust samples were generated at different emission sources using a Portable In-Situ Wind Erosion Lab (PI-SWERL), and the taxonomic composition of the resulting microbiomes was compared with the source soils. Dust emission processes resulted in the clear fractionation of the soil bacterial community, where dust samples were significantly enriched in spore-forming taxa. Conversely, little fractionation was observed in the soil fungal communities, such that the dust fungal fingerprint could be used to identify the source soil. Dust microbiomes were also found to vary according to the emission source, suggesting that land use significantly affected the structure and fractionation of microbial communities transported in dust plumes. In addition, several potential biological allergens of fungal origin were detected in the dust microbiomes, highlighting the potential detrimental effects of dust plumes emitted in South Africa. This study represents the first description of the fractionation of microbial taxa occurring at the source of dust plumes and provides a direct link between land use and its impact on the dust microbiome.

Magnetic signatures of natural and anthropogenic sources of urban dust aerosol

Abstract. The characteristics of urban dust aerosols and the contributions of their natural and anthropogenic sources are of scientific interest as well as being of substantial sociopolitical and economic concern. Here we present a comprehensive study of dust flux, magnetic parameters, magnetic particulate morphology, and elemental compositions of atmospheric dustfall originating from natural dust sources in East Asia and local anthropogenic sources in Xi'an, China. The results reveal a significant inverse relationship between seasonal variations of dust flux and magnetic susceptibility (χ). By comparing dust flux and χ records, the relative contributions of dust from local anthropogenic sources are estimated. Analyses using scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) indicate that magnetic particulate from different sources has distinct morphological and elemental characteristics. Detrital magnetic particles originating from natural sources are characterized by relatively smooth surfaces with Fe and O as the major elements and a minor contribution from Ti. The anthropogenic particles have angular, spherical, aggregate, and porous shapes with distinctive contributions from marker elements, including S, Cr, Cu, Zn, Ni, Mn, and Ca. Our results demonstrate that this multidisciplinary approach is effective in distinguishing dust particles derived from distant natural sources and local anthropogenic sources and for the quantitative assessment of contributions from the two end-members.

Quantifying contributions of natural and anthropogenic dust emission from different climatic regions

To quantitatively estimate the divergences in the natural and anthropogenic dust emission fluxes among different climatic regions, the total dust emissions at the global scale from 2007 to 2010 were simulated in this study. Despite the widely scattered anthropogenic dust distribution, the total area of potential anthropogenic dust sources was found slightly higher than that of natural dust sources. The anthropogenic dust distribution area was 1.61 × 107 km2 in January and 1.54 × 107 km2 in July, respectively. The natural dust sources contributed 81.0% of the global dust emissions and the anthropogenic contributed 19.0% of the residual. The natural and anthropogenic dust emission flux was 6.34 ± 0.31 μg m−2 s−1 and 1.01 ± 0.07 μg m−2 s−1, respectively. Especially, natural and anthropogenic dust emissions situated in different climatic regions. Natural dust emissions mainly located in hyper-arid and arid regions such as the Sahara, Arabian and Taklimakan Desert where dust emission fluxes range from 1 to 50 μg m−2 s−1, accounted for 97.3% of natural dust emissions at the global scale. While anthropogenic dust emissions concentrate in semi-arid, sub-humid and humid regions and generally fluctuated between 0.1 and 10 μg m−2 s−1. In addition, natural and anthropogenic dust proportions in semi-arid regions were the most complicated due to the complex land cover types, including grasslands, urban areas, croplands and open shrub lands, resulting in 42.99% of the anthropogenic dust emissions in semi-arid regions. The complex interplay of natural and anthropogenic dust emissions contributing to the total dust loadings may be a crucial factor enhanced the warming over semi-arid regions. This study provided confidence for the further investigation of the climatic impacts of natural and anthropogenic dust in different climatic regions under the background of global warming, especially the strengthening warming in semi-arid regions.

Trends of Aerosol Optical Properties over the Heavy Industrial Zone of Northeastern Asia in the Past Decade (2004–15)

The heavy industrial zone of northeastern Asia is dominated by year-round industrial scattering aerosols that undergo hygroscopic growth in summer. With the rapid economic development over the past decade, aerosol optical depth (AOD) has increased (6.35% yr−1) with an annual-mean AOD of 0.61 ± 0.13. Simultaneously, the aerosol particle size and aerosol scattering have increased, with an annual-mean scattering aerosol optical depth (SAOD) reaching 0.58 ± 0.15. However, considering that the annual AOD/gross domestic product (GDP) per capita decreased, the environmental degradation caused by aerosol emission is expected to reach a turning point based on the environmental Kuznets curve (EKC) hypothesis. In addition, annual-mean radiative forcing at the top, bottom, and interior of the atmospheric column reached −2.35 ± 2.33, −54.16 ± 7.26, and 51.81 ± 7.93 W m−2, respectively. The increase in unit SAOD contributes to the growth in net negative top-of-atmosphere (TOA) forcing and surface (SFC) forcing, and unit absorption aerosol optical depth (AAOD) increases together with atmosphere (ATM) forcing. Moreover, the cooling effect of aerosols on the Earth–atmosphere system showed an increase over the most recent 10 years related to the increase in scattering aerosol from development in the old industrial base. Except for local sources, under the western air masses, the circum–Bohai Sea economic zone was the potential source area of anthropogenic aerosols throughout the year with annual daily mean AOD, single-scattering albedo (SSA), TOA forcing, and SFC forcing values of 0.88, 0.93, −8.08, and −63.05 W m−2, respectively. The Mongolian Plateau was the potential natural dust source area under the northeastern air masses.

Anthropogenic dust emissions due to livestock trampling in a Mongolian temperate grassland

Abstract. Mongolian grasslands are a natural dust source region and they contribute to anthropogenic dust due to the long tradition of raising livestock there. Past decades of abrupt changes in a nomadic society necessitate a study on the effects of livestock trampling on dust emissions, so that research studies may help maintain a sustainable ecosystem and well-conditioned atmospheric environment. In this study, we conducted a mini wind tunnel experiment (using a PI-SWERL® device) to measure dust emissions fluxes from trampling (at three disturbance levels of livestock density, N) and zero trampling (natural as the background level) at test areas in a Mongolian temperate grassland. Moreover, we scaled anthropogenic dust emissions to natural dust emissions as a relative consequence of livestock trampling. We found a substantial increase in dust emissions due to livestock trampling. This effect of trampling on dust emissions was persistent throughout all wind friction velocities, u* (varying from 0.44 to 0.82 m s−1). Significantly higher dust loading occurs after a certain disturbance level has been reached by the livestock trampling. Our results suggest that both friction velocity (u*) and disturbance level of livestock density (N) have an enormous combinational effect on dust emissions from the trampling test surface. This means that the effect of livestock trampling on dust emissions can be seen or revealed when wind is strong. Our results also emphasize that better management for livestock allocation coupled with strategies to prevent anthropogenic dust loads are needed. However, there are many uncertainties and assumptions to be improved on in this study.

Spatial and Temporal Distributions of Air Pollutants and Size Distribution of Aerosols over Central and Eastern China.

The origins and spatial and temporal distributions of air pollutants (PM2.5, PM10, CO, SO2, NO2 and O3) during May to June of 2015 were investigated using data from 1490 monitoring sites in China. Aerosol number concentrations and meteorological data from Shijiazhuang, Nanjing, and Suzhou were combined with the MIX Asian emission data and the HYSPLIT model. Furthermore, the diurnal variation, size distribution, and main sources of air pollutants and aerosols were selectively characterized in the North China Plain (NCP) and the Yangtze River Delta (YRD). High values of particulate matter concentrations (PM), including PM2.5 and PM10, occurred in the northwestern and central regions of eastern China. Elevated PM2.5 and PM10 concentrations represented natural dust sources and anthropogenic resident, power plant, industry, and traffic emissions sources, respectively. The concentrated distributions of SO2 were similar to those of PM. The CO concentrations were distributed uniformly in China. High O3 values occurred above the Qinghai province. During the observation period, the air masses mainly originated from the northwest NCP and from the southwest or northeastern ocean in the YRD, resulting in high concentrations of PM2.5, PM10, SO2, and CO in the NCP, the average values of which were 61.8±40.0, 118.8±66.4, 24.1±24.6μgm-3, and 1.2±0.9mgm-3, respectively, and were 1.2, 1.4, 1.5, and 1.3 times larger than those in the YRD. NO2 had higher concentrations in the YRD with an average of 43.7±24.8μgm-3, which was 1.2 times larger than that in the NCP. The diurnal variations of PM, NO2 and CO had bimodal distributions and SO2 and O3 had unimodal distributions in the NCP and YRD. The aerosol number concentrations had average values of 12,661±5266, 11,189±5905, and 12,797±5931cm-3 in Shijiazhuang, Nanjing, and Suzhou. Their diurnal variations displayed trimodal peaks at 18:00-21:00, 11:00-14:00, and 06:00-08:00, and their spectra distributions were all unimodal with peaks at 60-70, 60-70, and 100-110nm, respectively.

Anthropogenic fugitive, combustion and industrial dust is a significant, underrepresented fine particulate matter source in global atmospheric models

Global measurements of the elemental composition of fine particulate matter across several urban locations by the Surface Particulate Matter Network reveal an enhanced fraction of anthropogenic dust compared to natural dust sources, especially over Asia. We develop a global simulation of anthropogenic fugitive, combustion, and industrial dust which, to our knowledge, is partially missing or strongly underrepresented in global models. We estimate 2–16 μg m−3 increase in fine particulate mass concentration across East and South Asia by including anthropogenic fugitive, combustion, and industrial dust emissions. A simulation including anthropogenic fugitive, combustion, and industrial dust emissions increases the correlation from 0.06 to 0.66 of simulated fine dust in comparison with Surface Particulate Matter Network measurements at 13 globally dispersed locations, and reduces the low bias by 10% in total fine particulate mass in comparison with global in situ observations. Global population-weighted PM2.5 increases by 2.9 μg m−3 (10%). Our assessment ascertains the urgent need of including this underrepresented fine anthropogenic dust source into global bottom-up emission inventories and global models.

Anthropogenic- and natural sources of dust in peatland during the Anthropocene.

As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). Anthropogenic spheroidal aluminosilicates clearly identify the beginning of industrial development and are proposed as a new indicator of the Anthropocene. In cal AD 1963 (±5), greatly elevated dust deposition and an increase in REE serve to show that the geochemistry of elements in the peat can be evidence of nuclear weapon testing; such constituted an enormous force blowing soil dust into the atmosphere. Among the natural dust sources, minor signals of dryness and of the Tunguska cosmic body (TCB) impact were noted. The TCB impact was indirectly confirmed by an unusual occurrence of mullite in the peat.

Tracing of aerosol sources in an urban environment using chemical, Sr isotope, and mineralogical characterization.

In the framework of two national research projects (ORGANOSOL and CN-linkAIR), fine particulate matter (PM2.5) was sampled for 17months at an urban location in the Western European Coast. The PM2.5 samples were analyzed for organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), major water-soluble inorganic ions, mineralogical, and for the first time in this region, strontium isotope (87Sr/86Sr) composition. Organic matter dominates the identifiable urban PM2.5 mass, followed by secondary inorganic aerosols. The acquired data resulted also in a seasonal overview of the carbonaceous and inorganic aerosol composition, with an important contribution from primary biomass burning and secondary formation processes in colder and warmer periods, respectively. The fossil-related primary EC seems to be continually present throughout the sampling period. The 87Sr/86Sr ratios were measured on both the labile and residual PM2.5 fractions as well as on the bulk PM2.5 samples. Regardless of the air mass origin, the residual fractions are more radiogenic (representative of a natural crustal dust source) than the labile fractions, whose 87Sr/86Sr ratios are comparable to that of seawater. The 87Sr/86Sr ratios and the mineralogical composition data further suggest that sea salt and mineral dust are important primary natural sources of fine aerosols throughout the sampling period.

Isotopic signature of atmospheric phosphate emitted from coal combustion

Atmospheric deposition of phosphorus (P) serves as an important nutrient input for many terrestrial, marine and freshwater ecosystems, influencing their biogeochemistry and primary production. Fossil fuel combustion, principally coal, is estimated to be a major source of atmospheric-P in industrialized regions. In this research, we aim to find a distinct isotopic signature for fly coal ash, the by-product of coal combustion that is emitted to the atmosphere. This signature could be used to identify coal's contribution to atmospheric-P. For this aim, ten fly coal ash samples from different coal sources, collected by power station filters, were analyzed for P concentrations and stable oxygen isotopic composition (δ18OP). Two inorganic phosphate fractions were analyzed: HCl-extractable and resin-extractable (bioavailable P). High HCl-P concentrations of up to 3500 μg P/g ash were found with a distinct δ18OP range of 17.1–20.5‰. The resin-P concentrations were substantially lower (<8 μg/g) with a wider and significantly lower δ18OP range of 10.6–16.5‰. The ash samples were found to have HCl-P δ18OP higher in ∼0–∼9‰ relative to the source coal. Similar isotopic values were found for ash with the same coal source country, regardless of the power station. Despite the low bioavailable P concentrations, fly ash could still be an important atmospheric P source to the biosphere since these combustion products likely acidify in the atmosphere to become bioavailable. This is also supported by our finding that smaller particles, which are more indicative of the particles actually emitted to the atmosphere, are significantly P-richer. Natural dust sources' δ18OP overlap fly ash's range, complicating the assessment of coal's contribution. Nonetheless, our results provide a new tool for identification of fossil fuel combustion sources in local and global atmospheric P deposition.

India: KMML – TiO2

Stable lead (Pb) isotopic fingerprints provide opportunities to trace natural and anthropogenic Pb sources in the environment. In order to evaluate Pb deposition from different sources over mountainous areas of western China, Pb isotopic compositions were characterized from modern aeolian dust in 15 snowpit samples collected from 13 typical mountain glaciers between 2008 and 2010. Most of the snowpits sampled cover more than a whole year of accumulation and overlap with each other on deposition date. Pb isotopic variability among all the samples is small, varying in the range of 18.1399–18.9199 for 206Pb/204Pb, 15.5979–15.8743 for 207Pb/204Pb, 38.2272–39.9453 for 208Pb/204Pb, 1.1605–1.2009 for 206Pb/207Pb and 2.4433–2.5182 for 208Pb/207Pb. Three isotopic plots of the different Pb isotope ratios (207Pb/204Pb vs. 206Pb/204Pb, 208Pb/204Pb vs. 206Pb/204Pb, and 208Pb/207Pb vs. 206Pb/207Pb) in all the samples show identical geographic trends, with more radiogenic in the south and less in the north. This trend is consistent with the distribution of natural dust sources and supports the interpretation of a regional/local source for insoluble particles (IP) to snow/glaciers in this region. Comparison with the Pb isotope results from potential dust sources, however, it shows that the Pb isotopic compositions of IP samples in snow samples are relatively less radiogenic. Parts of these less-radiogenic Pb isotopes are comparable with the ice core results during recent decades, which are shown to be influenced by anthropogenic sources. At sites located along the periphery of western China, the Pb isotopic compositions are much closer to anthropogenic results. Natural and anthropogenic Pb sources are roughly assessed using a simple binary model. The sites with a high anthropogenic fraction are at lower elevations and are relatively close to population centers.

Detection of anthropogenic dust using CALIPSO lidar measurements

Abstract. Anthropogenic dusts are those produced by human activities on disturbed soils, which are mainly cropland, pastureland, and urbanized regions, and are a subset of the total dust load which includes natural sources from desert regions. Our knowledge of anthropogenic dusts is still very limited due to a lack of data. To understand the contribution of anthropogenic dust to the total global dust load, it is important to identify it apart from total dust. In this study, a new technique for distinguishing anthropogenic dust from natural dust is proposed by using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) dust and planetary boundary layer (PBL) height retrievals along with a land use data set. Using this technique, the global distribution of dust is analyzed and the relative contribution of anthropogenic and natural dust sources to regional and global emissions are estimated. Results reveal that local anthropogenic dust aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25 % of the global continental dust load. Of these anthropogenic dust aerosols, more than 53 % come from semi-arid and semi-wet regions. Annual mean anthropogenic dust column burden (DCB) values range from 0.42 g m−2, with a maximum in India, to 0.12 g m−2, with a minimum in North America. A better understanding of anthropogenic dust emission will enable us to focus on human activities in these critical regions and with such knowledge we will be more able to improve global dust models and to explore the effects of anthropogenic emission on radiative forcing, climate change, and air quality in the future.

Anthropogenically induced changes in twentieth century mineral dust burden and the associated impact on radiative forcing

AbstractWe investigate the relative importance of climate change (CC) and anthropogenic land cover change (ALCC) for the dust emissions and burden changes between the late nineteenth century and today. For this purpose, the climate‐aerosol model ECHAM6‐HAM2 is complemented by a new scheme to derive potential dust sources at runtime using the vegetation cover provided by the land component JSBACH of ECHAM6. Dust emissions are computed online using information from the ECHAM6 atmospheric component. This allows us to account for changes in land cover and climate interactively and to distinguish between emissions from natural and agricultural dust sources. For today's climate we find that nearly 10% of dust particles are emitted from agricultural areas. According to our simulations, global annual dust emissions have increased by 25% between the late nineteenth century and today (e.g., from 729 Tg/a to 912 Tg/a). Globally, CC and ALCC (e.g., agricultural expansion) have both contributed to this change (56% and 40%, respectively). There are however large regional differences. For example, change in dust emissions in Africa are clearly dominated by CC. Global dust burden have increased by 24.5% since the late nineteenth century, which results in a clear‐sky radiative forcing at top of the atmosphere of −0.14 W/m2. Based on these findings, we recommend that both climate changes and anthropogenic land cover changes should be considered when investigating long‐term changes in dust emissions.

Lead isotopic composition of insoluble particles from widespread mountain glaciers in western China: Natural vs. anthropogenic sources

Stable lead (Pb) isotopic fingerprints provide opportunities to trace natural and anthropogenic Pb sources in the environment. In order to evaluate Pb deposition from different sources over mountainous areas of western China, Pb isotopic compositions were characterized from modern aeolian dust in 15 snowpit samples collected from 13 typical mountain glaciers between 2008 and 2010. Most of the snowpits sampled cover more than a whole year of accumulation and overlap with each other on deposition date. Pb isotopic variability among all the samples is small, varying in the range of 18.1399–18.9199 for 206Pb/204Pb, 15.5979–15.8743 for 207Pb/204Pb, 38.2272–39.9453 for 208Pb/204Pb, 1.1605–1.2009 for 206Pb/207Pb and 2.4433–2.5182 for 208Pb/207Pb. Three isotopic plots of the different Pb isotope ratios (207Pb/204Pb vs. 206Pb/204Pb, 208Pb/204Pb vs. 206Pb/204Pb, and 208Pb/207Pb vs. 206Pb/207Pb) in all the samples show identical geographic trends, with more radiogenic in the south and less in the north. This trend is consistent with the distribution of natural dust sources and supports the interpretation of a regional/local source for insoluble particles (IP) to snow/glaciers in this region. Comparison with the Pb isotope results from potential dust sources, however, it shows that the Pb isotopic compositions of IP samples in snow samples are relatively less radiogenic. Parts of these less-radiogenic Pb isotopes are comparable with the ice core results during recent decades, which are shown to be influenced by anthropogenic sources. At sites located along the periphery of western China, the Pb isotopic compositions are much closer to anthropogenic results. Natural and anthropogenic Pb sources are roughly assessed using a simple binary model. The sites with a high anthropogenic fraction are at lower elevations and are relatively close to population centers.