Asian Dust Emissions Research Articles

Paleo-tropical cyclone activity over the last millennium inferred from shipwreck relics in the Xisha Islands, northern South China Sea

The prediction of the impact of long-term climate change on tropical cyclone (TC) activity has become a global concern, for which paleotempestology could provide crucial information about TC activity before instrumental archives. The ancient shipwrecks could alternatively be applied to retrieve paleo-TC activity owing to strong TC activity being among the dominant causes of historical shipwrecks. This study presents a preliminary study exploring the potential relationship between the shipwrecks and TC activity based on the compilation of shipwreck relics and chronological assessments of porcelains associated with the shipwrecks in the Xisha Islands, in the northern South China Sea (SCS). The compilation generally spans from the Song Dynasty to the Qing Dynasty (approximately 960 to 1850 CE), showing relatively enhanced shipwreck events during the time interval between 1400 and 1700 CE, consistent with the increased moisture and flood events during this period from other adjacent sedimentary records. Further analysis suggests that paleo-TC activity was controlled by multiple mechanisms concerning the El Niño Southern Oscillation (ENSO), the movement of the Intertropical Convergence Zone (ITCZ), and Asian dust emissions. Frequent ENSO events and the southward retreat of the ITCZ would have contributed to increased moisture in tropical regions promoting TC activity during the Little Ice Age (LIA), while the dust would strengthen TC activity through atmospheric circulations. Additional work combining the archaeological and sedimentary archives should be indispensable to further understand the climatic connections and potential mechanisms of TC processes, under climate change and relevant mitigation measures.

Effects of multiple factors on particle size selectivity under artificial extreme rainfall events on simulated Gobi surface

Understanding multiple-factor effects on particle size selectivity by extreme rainfall events in Ala-Shan Gobi desert is of great significance for better estimation of potential Asian dust emission sources. Artificial rainfall simulation experiments were used to investigate the particle size selectivity characteristics by extreme rainfall events under different rainfall intensities (20 mm h−1 and 40 mm h−1), slope gradients (3° and 15°) and gravel coverages (0, 30%, and 60%). Moreover, the relations of clay content (Clc), silt content (Sic), fine particle (< 50 μm) content (Fic) and enrichment ratio of fine particles (ER<50) with multiple factors were regressed and validated. Results show that rainfall intensity significantly (P < 0.05) affect runoff and sediment yield processes, but slope gradient was a dominant factor that changed particle size distribution (PSD). The selectivity of fine particles was higher at low rainfall intensity (20 mm h−1), gentle slope (3°) and moderate gravel coverage (30%), with ER<50 reaching 6.14, which dominate the potential Asian dust emission sources. The interaction were discussed and classified into ‘Synergy’ and ‘Trade-off’. Clc and Fic showed negative exponential relationship with rainfall intensity and slope gradient, but positive exponential relationship with gravel coverage. While Sic and ER<50 showed negative power function relationship with rainfall intensity, slope gradient and gravel coverage. These findings could help to understand the effects of multiple factors on potential sources of Asian dust emission under extreme rainfall events in Gobi region of northwestern China and provide basic science reference for the prediction of dust emission in this region.

Sources of aeolian magnetite at a remote site in Japan: Dominantly Asian desert dust or anthropogenic emissions?

Asian dust (AD) profoundly impacts human health and the environment, and the soluble Fe in AD is essential for nutrient supply to the ocean and atmospheric chemistry. To accurately assess the impacts of AD, it must be separated from other natural and anthropogenic sources in the total aerosol loading. In this study, coarse aerosol samples (Dp > 2.5 μm) collected in Noto, a remote coastal area in Japan, were analyzed through an environmental magnetic analysis. A comparison of the metal content and Pb isotopic ratios revealed that the magnetization of aerosols, which reflects magnetite content, highly correlated with AD inflow. That is, aerosol magnetite is preferentially concentrated in atmospheric particles during AD events; therefore, AD-affected samples can easily be identified and distinguished from those primarily affected by transboundary air pollution by using magnetic measurements. Based on the magnetization intensity of an AD reference material (CJ-2), the AD loading for ambient samples was estimated to be 5.2–32 μg/m3, similar to that calculated based on the Al mass concentration. Moreover, magnetism is strongly linked with Fe solubility in the ambient samples. This is notable because such information has been obtained previously only through labor-intensive chemical speciation involving sequential extraction. Therefore, magnetism can be used as a new measure of both AD loading and Fe solubility via non-destructive measurements.

The Spatiotemporal Characteristics and Driving Factors of Dust Emissions in East Asia (2000–2021)

The climate effect and environmental pollution caused by dust discharged into the atmosphere have attracted much attention. However, the driving factors of dust emissions have not been studied thoroughly. Here, spatiotemporal variations in dust emissions and the relationship between dust emissions and large-scale atmospheric circulation in East Asia from 2000 to 2021 were investigated using Modern-Era Retrospective Analysis for Research and Applications version 2, Cloud-Aerosol Lidar Pathfinder Satellite Observations, ERA5 reanalysis data, and climate indices. Results showed that the Taklimakan Desert in the Tarim Basin, the Gurbantonggut Desert in the Junggar Basin, the Turpan Basin, and the Gobi Desert in western Inner Mongolia and southern Mongolia are the main sources of dust emissions in East Asia. The period of strong dust emissions is from March to May, and emissions to the atmosphere were mainly distributed at 0–4 km in the troposphere. In the eastern and southwestern Tarim Basin, northern Junggar Basin, and parts of the Gobi Desert in southern Mongolia, dust emissions have significantly increased over the past 22 years, whereas in the southwestern Tibetan Plateau, southwestern Inner Mongolia, and a small part of the northern Mongolian Gobi Desert there was a significant decreasing trend. The winter North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) were significantly negatively correlated with East Asian dust emissions the following spring. The various phases of the AO/NAO coupling have clear different effects on East Asian dust emissions in the spring. When the AO/NAO coupling was negative (positive), the East Asian trough and Siberian High were strengthened (weakened), the frequency of cold air activity increased (weakened), 800 hPa wind speed strengthened (weakened), and East Asian emissions increased (decreased). In AO−/NAO+ years, the Asian polar vortex was stronger to the south and the East Asian trough was stronger to the west. The Lake Baikal trough was in the deepening phase, which caused more polar cold air to move into East Asia, aggravating the intensity of dust activity. In the AO+/NAO− years, the Siberian High and East Asian trough weakened, which was unfavorable to the southward movement of cold air from Siberia. Therefore, the frequency of windy weather in East Asia decreased, partly weakening dust emissions. However, a positive geopotential anomaly in northeast China and a negative geopotential anomaly in South Asia triggered an anomalous enhancement in easterly wind in the tropospheric area over northwest China. Strengthening of the Balkhash trough provides favorable conditions for gale weather in northwest China. The frequency of gale weather increased, and dust emissions were enhanced in northwest China.

Grain-size composition of the surface sediments in Chinese deserts and the associated dust emission

Chinese deserts are one of the essential source areas for global dust emission, and the intensity of dust emissions varies significantly depending on the grain-size composition of sediments, wind force, and vegetation coverage. To obtain complete and accurate information on the grain-size compositions of the surface sediments in these deserts and to assess the contribution of Chinese deserts to Asian dust emission, we systematically collected surface sediments from 12 deserts in northern China, and analyzed their grain-size composition. We also calculated dust emissions from 2010 to 2019 based on the sand transport rate and clay content. The mean grain-size of surface sediments was 2.34Φ, and the clay and silt contents were only 0.6 and 6.7%, respectively. The Taklimakan Desert had the finest surface sediment, with a mean grain-size of 2.75Φ, whereas the Kumtag Desert had the coarsest sediment, with a mean grain-size of 2.00Φ. The total annual dust emission of the Chinese deserts from 2010 to 2019 was 70.6 Tg y-1. The Taklimakan Desert in the western region, the Badain Jaran Desert and the adjacent Tengger and Ulan Buh deserts in the central region, and the Otindag Sandy Land in the eastern region were the greatest contributors to dust emission. These core areas of dust emission are also the regions with the highest dust storm frequency, indicating that the deserts are significant regions for dust storms in northern China and an important surface type for dust emission in China. We found a significant positive correlation between dust emission and dust storm frequency.

A 1600-year record of eolian activity from Jili Lake in northern Xinjiang

Eolian activity determines the magnitude of dust emission. However, geological records of eolian activity are scarce due to strong wind erosion in the dust source areas. Northern Xinjiang is recognized as a major dust source region in arid central Asia. Here we present a lacustrine record of eolian activity over the past 1600 years from Jili Lake, in northern Xinjiang, which acts a natural trap for airborne materials. Based on the stratigraphic variability of two sedimentary sequences and 20 radiocarbon dates, we infer that Jili Lake initially developed in the southwestern part of the lake basin during the mid-Holocene and then expanded to close to its modern surface area until 1600 years ago. Grain-size analyses of materials from different parts of the lake sedimentary system, including lake surface sediments, lake catchment deposits, and airborne sand and dust collected from near the lakeshore, demonstrate that the coarse silt and fine sand fraction (40–200 μm) of the lake sediments was transported primarily by strong winds and can be regarded as an indicator of changes in eolian activity. We argue that wind strength played an important role in lifting and transporting the coarse particles, although an arid climate cannot be entirely excluded out as a factor favoring eolian activity. The most intensive eolian activity occurred from ∼910 to 1300 AD, roughly corresponding to the Medieval Warm Period (MWP), whereas eolian activity was weak during the Little Ice Age (LIA, ∼1300 to 1760 AD). However, this pattern is inconsistent with other dust records from central Asia. Eolian dust activity reflects the coupling of dust-generating windstorms and dust source areas which were swept by cold air surges. The spatial differentiation of eolian dust activity in arid central Asia may thus be causally linked to the intensity and extent of the Siberian High (SH), given that intense cyclogenesis always occurs on the southwestern periphery of the SH in springtime. Changes in the SH can be further ascribed to atmospheric circulation modulated by phase alternations of the North Atlantic Oscillation (NAO) due to large-scale thermal contrasts. Our results suggest that the dynamics of Asian dust emission are closely linked with the spatial variability of the SH. Nonetheless, more records of eolian activity are needed to further elucidate the forcing mechanisms of dust entrainment in the source area of Asian dust.

Northwestern Pacific tropical cyclone activity enhanced by increased Asian dust emissions during the Little Ice Age

Instrumental records reveal that intense tropical cyclone (TC) activity varies with tropical sea surface temperature (SST) on annual-decadal scales. Drivers of intense TC activity at the centennial-millennial scale are less clear, due to the sparseness of pre-observational reconstructions. Here, we present a new 2 kyr continuous activity record of intense TCs from offshore eastern China. Our reconstruction indicates that this site witnessed enhanced TC activity during relatively warm periods, with a widespread increase in TC activity during the later part of the Little Ice Age. This latter observation reveals that enhanced TC activity was synchronized with increased Asian dust emissions during the Little Ice Age. TC activity was also lower in the late Roman Warm Period, when SST was higher but Asian dust emissions were lower than in the early phase. Such patterns suggest a centennial-millennial link between TC climatology and a combination of SST changes and Asian dust levels.

Impacts of climate and land cover variability and trends on springtime East Asian dust emission over 1982–2010: A modeling study

Mineral dust is an important player in global air quality and climate, but little is known about its variability and trends under the simultaneous influence of climate and land cover changes, particularly in East Asia where intense land cover change has occurred in recent decades. Here we determined the interannual variability and trends in dust emission from the main East Asian dust sources and examined to what extent these variations and trends were driven by climatic or land cover changes. We first optimized the dust emission module in the GEOS-Chem chemical transport model with better representation of dust physics and dependence on vegetation and wind variability. We then conducted simulations to quantify the impacts of climate and land cover variability and trends on springtime dust emission over 1982–2010 from the Teklimakan Desert, Gobi Desert and the whole East Asian desert domain. We found that dust emission from Gobi decreased substantially from the 1980s to 1990s, and then slightly increased toward the 2000s, leading to an overall reduction by 35% over the whole period. These changes were predominantly driven by meteorological changes and the effects of land cover change were negligible. Dust emission from Teklimakan increased from the 1980s to 1990s, but decreased afterward, leading to an overall reduction by 20%, albeit with large interannual variability. The overall trend was attributable to a consistent reduction in dust emission due to enhanced vegetation density in the periphery of the desert, accompanied by larger but more varying changes due to meteorological factors. Time series comparison and regression analysis indicated that in both deserts (especially Gobi), surface wind speed, followed by total precipitation, was the most important meteorological factor controlling dust variability and trends, with the weakening of wind playing the largest role in the overall decline in dust emission over the whole period. Overall, the interannual variability and trends of East Asian dust emission are largely shaped by climatic factors, with the land cover playing secondary but locally important roles, especially in the semiarid and non-desert regions undergoing rapid land cover change and desertification.

Neodymium isotopic constraints on Cenozoic Asian dust provenance changes linked to the exhumation history of the northern Tibetan Plateau and the Central Asian Orogenic Belt

The arid interior of Asia is the largest source of dust deposited in the North Pacific Ocean, and some dust is even transported to Greenland. Investigating the provenance history of Asian dust can provide strong constraints on the evolution of topography and climate in the Asian interior. Eolian dust Nd isotopic records preserved in North Pacific Ocean sediments since ∼40 Ma provide a spatially integrated first-order constraint on the provenance changes of Asian dust. However, a lack of similarly long dust Nd isotopic records from Asian dust source areas, namely, the northern Tibetan Plateau and the Central Asian Orogenic Belt, has hindered a full understanding of Asian dust provenance changes linked to the Cenozoic evolution of tectonics, climate and topography in inland Asia. Here, we have constructed the first fine-grained and whole-rock Nd isotopic records from sediments deposited on the northern Tibetan Plateau since ∼52 Ma. The results indicate two major changes, a gradual increase in εNd(0) values between ∼42 Ma and ∼25 Ma and a general decrease since ∼25 Ma, which were probably caused by the incremental northward growth of the Tibetan Plateau. Further mass balance estimates based on comparisons between the Nd isotopic characteristics of dust from the northern Tibetan Plateau and the North Pacific Ocean indicate that a rapid increase in the contribution of the Central Asian Orogenic Belt to Asian dust at ∼25 Ma can be closely linked to rapid exhumation caused by tectonic uplift and aridification in inland Asia. Our provenance analyses, together with the onset of eolian sediment in central and eastern Asia, suggest that a modern-like regime promoting Asian dust emissions and transport might have been in place since the late Oligocene.

High Sensitivity of Asian Dust Emission, Transport, and Climate Impacts to Threshold Friction Velocity

High Sensitivity of Asian Dust Emission, Transport, and Climate Impacts to Threshold Friction Velocity

Seasonal Variations and Long-term Trend of Mineral Dust Aerosols over the Taiwan Region

Atmospheric dust aerosols are known to affect the air quality and public health as well as climate and weather systems. An increasing number of modeling studies have related ice nucleation with the number concentrations of dust particles with a diameter larger than 500 nm (ND,d>500nm). In this paper, the seasonal variation, vertical properties, and long-term trend of ND,d>500nm over the Taiwan region are analyzed, using simulations from a global chemical transport model with size-resolved particle microphysics. Over Taiwan, ND,d>500nm shows a bimodal seasonal variation distribution with two peaks in spring (March–May) and fall-early winter (October–December). In the different seasons, ND,d>500nm varies by about one order of magnitude from summer to spring (0.06–1.23 cm–3 in the boundary layer, 0.03–0.55 cm–3 in the middle and lower troposphere, and 0.006–0.03 cm–3 in the upper level). Vertically, ND,d>500nm profiles show the unimodal distribution, with the highest ND,d>500nm appears at ~1 km and decreasing with altitude. From surface to high levels, the frequencies of intense dust events decrease in fall (September–November) and increase in summer months (June–August). The long-term model results suggest a decreasing trend of the strong dust event frequencies and annual mean ND,d>500nm over Taiwan in the last two decades. From 1999 to 2018, the number of strong dust event days and ND,d>500nm decreased by 40–43% and 37–54%, respectively, under 4 km, and the decline is weaker at higher altitudes. The analysis suggests that these decrease trends are caused by the declining Asian dust emissions.

Performance of KMA-ADAM3 in Identifying Asian Dust Days over Northern China

Recently, the Korea Meteorological Administration developed Asian Dust Aerosol Model version 3 (ADAM3) by incorporating additional parameters into ADAM2, including anthropogenic particulate matter (PM) emissions, modification of dust generation by considering real-time surface vegetation, and assimilations of surface PM observations and satellite-measured aerosol optical depth. This study evaluates the performance of ADAM3 in identifying Asian dust days over the dust source regions in Northern China and their variations according to regions and soil types by comparing its performance with ADAM2 (from January to June of 2017). In all regions the performance of ADAM3 was markedly improved, especially for Northwestern China, where the threat score (TS) and the probability of detection (POD) improved from 5.4% and 5.5% to 30.4% and 34.4%, respectively. ADAM3 outperforms ADAM2 for all soil types, especially for the sand-type soil for which TS and POD are improved from 39.2.0% and 50.7% to 48.9% and 68.2%, respectively. Despite these improvements in regions and surface soil types, Asian dust emission formulas in ADAM3 need improvement for the loess-type soils to modulate the overestimation of Asian dust events related to anthropogenic emissions in the Huabei Plain and Manchuria.

Effects of dust-in-snow forcing over the Tibetan Plateau on the East Asian dust cycle during the Last Glacial Maximum

The improved Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM) was used to investigate the dust-in-snow radiative forcing (SRF) over the Tibetan Plateau (TP) and its feedbacks on the regional climate and the dust cycle in spring, the season with the strongest dust activity, over East Asia during the Last Glacial Maximum (LGM). Simulated results show that the dust in snow can cause a large positive SRF and significant warming at the TP surface, reaching more than 45 W m−2 and 3–5 °C warming in western TP during the LGM. The SRF increases the East Asian dust emissions, dry deposition and wet deposition by 71.6 Tg (8.1%), 34.5 Tg (7.0%) and 7.9 Tg (16.0%), respectively, in spring during LGM. Further analysis reveals that, the SRF warms the TP surface and enhances the thermal effect of the TP in spring by increasing the surface shortwave radiative forcing, sensible and latent heat fluxes. A mid-upper level anticyclonic circulation anomaly is generated, thus increases the regional westerly wind over the East Asian dust source region, and in turn enhances the dust emission and dust transport over East Asia. In general, SRF over the TP creates a positive feedback loop of enhancing the East Asian dust cycle during LGM.

Prediction of Asian Dust Days over Northern China Using the KMA-ADAM2 Model

Abstract This study evaluates the Korea Meteorological Administration (KMA) Asian Dust Aerosol Model 2 (ADAM2) for Asian dust events over the dust source regions in northern China during the first half of 2017. Using the observed hourly particulate matter (PM) concentration from the China Ministry of Environmental Protection (MEP) and station weather reports, we find that a threshold value of PM10–PM2.5 = 400 μg m−3 works well in defining an Asian dust event for both the MEP-observed and the ADAM2-simulated data. In northwestern China, ADAM2 underestimates the observed dust days mainly due to underestimation of dust emissions; ADAM2 overestimates the observed Asian dust days over Manchuria due to overestimation of dust emissions. Performance of ADAM2 in estimating Asian dust emissions varies quite systematically according to dominant soil types within each region. The current formulation works well for the Gobi and sand soil types, but substantially overestimates dust emissions for the loess-type soils. This suggests that the ADAM2 model errors are likely to originate from the soil-type-dependent dust emissions formulation and that the formulation for the mixed and loess-type soils needs to be recalibrated. In addition, inability to account for the concentration of fine PMs from anthropogenic sources results in large false-alarm rates over heavily industrialized regions. Direct calculation of PM2.5 in the upcoming ADAM3 model is expected to alleviate the problems related to anthropogenic PMs in identifying Asian dust events.

Inverting the East Asian Dust Emission Fluxes Using the Ensemble Kalman Smoother and Himawari-8 AODs: A Case Study with WRF-Chem v3.5.1

We present the inversions (back-calculations or optimizations) of dust emissions for a severe winter dust event over East Asia in November 2016. The inversion system based on a fixed-lag ensemble Kalman smoother is newly implemented in the Weather Research and Forecasting model and is coupled with Chemistry (WRF-Chem). The assimilated observations are the hourly aerosol optical depths (AODs) from the next-generation geostationary satellite Himawari-8. The posterior total dust emissions (2.59 Tg) for this event are 3.8 times higher than the priori total dust emissions (0.68 Tg) during 25–27 November 2016. The net result is that the simulated aerosol horizontal and vertical distributions are both in better agreement with the assimilated Himawari-8 observations and independent observations from the ground-based AErosol RObotic NETwork (AERONET), the satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The developed emission inversion approach, combined with the geostationary satellite observations, can be very helpful for properly estimating the Asian dust emissions.

Joint influence of surface erosion and high-latitude ice-sheet extent on Asian dust cycle during the last glacial maximum

AbstractThe dust cycle plays an important role in the long-term evolution of the climate and environment. In this paper, an improved climate model including aerosol processes was used to carry out a set of sensitivity experiments and comparative analyses of the effects of high-latitude ice-sheet extent and abnormal dust erosion, as well as Earth’s orbital parameters and atmospheric greenhouse gas content, on dust activities during the last glacial maximum. The comparative analysis found that incorporating the abnormal surface erosion factor alone could increase dust emissions by 2.77-fold and 3.77-fold of the present-day global and Asian dust emissions, respectively. The high-latitude ice-sheet factor caused global dust emissions to increase by 1.25-fold that of the present day. Sensitivity experiments showed that increased surface erosion in Asia during the last glacial maximum made the greatest contribution to the increased dust emissions in Asia, followed by the high-latitude ice-sheet factor, while the contributions of the greenhouse gas content and orbital parameters were relatively weak. Strong dust emissions during the glacial period were therefore not only dependent on the development of the high-latitude ice sheets but were strongly associated with the underlying surface characteristics of local dust source regions.

A Study on Particulate Matter Forecasting Improvement by using Asian Dust Emissions in East Asia

Air quality forecasting system with Asian dust emissions was developed in East Asia, and PM10 forecasting performance of chemical transport model with Asian dust emissions was validated and evaluated. The chemical transport model (CTM) with Asian dust emission was found to supplement PM10 concentrations that had been under-estimated in China regions and improved statistics for performance of CTM, although the model were overestimated during some periods in China. In Korea, the prediction model adequately simulated inflow of Asian dust events on February 22~24 and March 16~17, but the model is found to be overestimated during no Asian dust event periods on April. However, the model supplemented PM10 concentrations, which was underestimated in most regions in Korea and the statistics for performance of the models were improved. The PM10 forecasting performance of air quality forecasting model with Asian dust emissions tends to improve POD (Probability of Detection) compared to basic model without Asian dust emissions, but A (Accuracy) has shown similar or decreased, and FAR (False Alarms) have increased during 2017.Therefore, the developed air quality forecasting model with Asian dust emission was not proposed as a representative PM10 forecast model in South Korea.

Radiative feedbacks of dust in snow over eastern Asia in CAM4-BAM

Abstract. Dust in snow on the Tibetan Plateau (TP) could reduce the visible snow albedo by changing surface optical properties and removing the snow cover through increased snowmelt, which leads to a significant positive radiative forcing and remarkably alters the regional energy balance and the eastern Asian climate system. This study extends our previous investigation in dust–radiation interactions to investigate the dust-in-snow radiative forcing (SRF) and its feedbacks on the regional climate and the dust cycle over eastern Asia through the use of the Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM). Our results show that SRF increases the eastern Asian dust emissions significantly by 13.7 % in the spring, countering a 7.6 % decrease in the regional emissions by the dust direct radiative forcing (DRF). SRF also remarkably affects the whole dust cycle, including transport and deposition of dust aerosols over eastern Asia. The simulations indicate an increase in dust emissions of 5.1 %, due to the combined effect of DRF and SRF. Further analysis reveals that these results are mainly due to the regional climatic feedbacks induced by SRF over eastern Asia. By reducing the snow albedo over the TP, the dust in snow mainly warms the TP and influences its thermal effects by increasing the surface sensible and latent heat flux, which in turn increases the aridity and westerly winds over northwestern China and affects the regional dust cycle. Additionally, the dust in snow also accelerates the snow-melting process, reduces the snow cover and then expands the eastern Asian dust source region, which results in increasing the regional dust emissions. Hence, a significant feature of SRF on the TP is the creation of a positive feedback loop that affects the dust cycle over eastern Asia.

Concentrations and chemical forms of heavy metals in the bulk atmospheric deposition of Beijing, China

This study aimed to investigate concentrations and mobility of selected metals (As, Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn) contained in the bulk atmospheric deposition of Beijing, China, between March 2007 and February 2008, and to evaluate the metal deposition fluxes. Beijing endured heavy atmospheric deposited metal pollution with a deposition flux of 149.28kgkm-2year-1 from nine metals studied, and a significant increasing trend was noted from metals studied during the past 23years. High enrichment factors (EFs) of As, Zn, Pb, Cd, and Cu manifested their major anthropogenic sources. Among which, Cd and Pb require a consistent monitoring and to be strictly controlled regarding their high mobility and ecotoxicity. Furthermore, a declined metal concentration was observed in the bulk atmospheric deposition during spring, and long-transported crustal particles sourced from East Asian dust emission belt can reasonably account for this phenomenon.

Inverse Modeling of Asian Dust Emissions with POPC Observations: A TEMM Dust Sand Storm 2014 Case Study

An inverse modeling system for estimating Asian dust emissions was developed by combining the GEOS-Chem chemical transport model with the Green's function method. We applied the system to two heavy dust storms that occurred in 2014 (10-25 March and 24 May to 5 June), using surface-based polarization optical particle counter (POPC) observations at Fukuoka. Validation by independent observation datasets, including POPC measurements and PM10 observations at Seoul, showed that the use of a posteriori dust emissions improved overestimations in the a priori simulation and achieved much better agreement with observations. Satellite observations, surface synoptic observations, and modeled wind fields indicated that the major dust source region differed between the two dust storms; the major dust outbreak of one storm occurred in the northeastern Gobi Desert, whereas that of the other occurred in the southern Gobi Desert. The a posteriori dust emissions successfully reproduced this difference. Thus, the inverse modeling system developed in this study was able to improve the estimation of not only the intensity but also the geographical distribution of dust emissions.