Contribution Of Asian Dust Research Articles

Contribution of Asian dust into the sediment budget of the Parece Vela Basin over the last 1 Ma: Implications for the climate change in East Asia

By quantifying the deposition of Asia-derived dust in the Western Pacific Ocean it is possible to constrain the consequences of climate change in East Asia. However, the rates of eolian dust deposition and its transport mechanism in the low-latitude Pacific remain uncertain. Core CP19 recovered sediment dating from ∼1 Ma to the present in the Parece Vela Basin (PVB). In this study we present bulk-rock major and trace element geochemistry, and Sr and Nd isotopic compositions from this sediment. The results reveal that these clastic sediments are a mixture of volcanic materials derived from the adjacent island arcs and eolian dust material originating from the arid regions of East Asia. Within the PVB, the proportion of Asian dust in the detrital sediment ranges from 30% to 50%, with an average of 44%. The majority of the dust originated from Eastern Asian deserts. Sr and Nd isotopes indicate that there is a significant increase in the overall proportion of eolian dust in the PVB starting at ∼0.64 Ma, influenced by an enhanced East Asian winter monsoon. In contrast, strengthening of the East Asian summer monsoon led to a decrease in the proportion of the eolian dust from the Ordos deserts. The notable alteration in eolian dust flux to the PVB corresponds to an abrupt intensification of aridity and monsoon climate in the East Asian continent at ∼0.64 Ma, caused by the Middle Pleistocene Climate Transition.

Contribution of the world's main dust source regions to the global cycle of desert dust

Abstract. Even though desert dust is the most abundant aerosol by mass in Earth's atmosphere, the relative contributions of the world's major source regions to the global dust cycle remain poorly constrained. This problem hinders accounting for the potentially large impact of regional differences in dust properties on clouds, the Earth's energy balance, and terrestrial and marine biogeochemical cycles. Here, we constrain the contribution of each of the world's main dust source regions to the global dust cycle. We use an analytical framework that integrates an ensemble of global aerosol model simulations with observationally informed constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth (DAOD). We obtain a dataset that constrains the relative contribution of nine major source regions to size-resolved dust emission, atmospheric loading, DAOD, concentration, and deposition flux. We find that the 22–29 Tg (1 standard error range) global loading of dust with a geometric diameter up to 20 µm is partitioned as follows: North African source regions contribute ∼ 50 % (11–15 Tg), Asian source regions contribute ∼ 40 % (8–13 Tg), and North American and Southern Hemisphere regions contribute ∼ 10 % (1.8–3.2 Tg). These results suggest that current models on average overestimate the contribution of North African sources to atmospheric dust loading at ∼ 65 %, while underestimating the contribution of Asian dust at ∼ 30 %. Our results further show that each source region's dust loading peaks in local spring and summer, which is partially driven by increased dust lifetime in those seasons. We also quantify the dust deposition flux to the Amazon rainforest to be ∼ 10 Tg yr−1, which is a factor of 2–3 less than inferred from satellite data by previous work that likely overestimated dust deposition by underestimating the dust mass extinction efficiency. The data obtained in this paper can be used to obtain improved constraints on dust impacts on clouds, climate, biogeochemical cycles, and other parts of the Earth system.

Contribution of Asian dust to soils in Southeast China estimated with Nd and Pb isotopic compositions

Asian dust has been identified in subtropical soils of China. Neodymium (Nd) and lead (Pb) elemental and isotopic geochemistry of soils in Southeast China were used to assess the significance of local versus extraneous sources. The eNd(0) values were close to the parent rocks (+ 2.9) in the young soils (NSJ); while their values were always negative (~ − 3.7) in the old soils (OMJ), implying dust deposition. The young soils contained less Asian dust contribution (< 8 %) while the old soils contained more than 50 % Asian dust contribution. This implied that dust contributions were gradually increasing with the soil development stage and Asian dust input had become the principal Nd source for the old soils in this area. On the other hand, Pb excesses and low 207Pb/206Pb values (~ 0.8503) in near-surface soils indicated a significant anthropogenic Pb addition onto surface soils. The close relationship between the Pb content and isotopic ratios in the soil profile indicated that the excessive lead in the surface soil was exogenous. These results suggested that Asian dust made up a significant fraction in the old soils, but that local sources (i.e., basalt and anthropogenic) were not trivial in Southeast China.

Estimating transboundary transported anthropogenic sulfate deposition in Japan using the sulfur isotopic ratio

High emissions of air pollutants from Northeast Asia are strongly influenced by air quality as well as by ecosystems. This study investigated the spatiotemporal variations in the sulfur isotopic ratio (δ34S) in atmospheric deposition at eleven monitoring stations in Japan from 2011 to 2016 and estimated the amount of transboundary transported anthropogenic sulfate (TRB) deposition using mass balance calculations. The δ34S of sulfate in precipitation ranged from -0.42 to +22.7‰. Sea salt (SS), TRB, and domestic anthropogenic sources (DOM) were the dominant sources of sulfate deposition in Japan. TRB sulfate deposition was largest on the Sea of Japan side, with an annual average value of 1.5 ± 0.3-6.9 ± 0.5 mg m-2 d-1 (36-44%), followed by Mt. Happo (4.5 ± 0.1 mg m-2 d-1; 88%), the Pacific Ocean side (1.5 ± 0.8, 4.3 ± 0.9 mg m-2 d-1; 24-50%), and the remote islands in the North Pacific Ocean (1.1 ± 0.2, 2.0 ± 0.8 mg m-2 d-1; 19-32%). TRB sulfate deposition on the Sea of Japan side was 2-12 times higher in winter and 1-2 times higher in summer than that of DOM. In contrast, TRB sulfate deposition on the Pacific Ocean side was 1.5-3 times higher in summer than in winter due to high precipitation levels. In Tokyo, the annual contribution from DOM sulfate deposition is approximately three times higher than that from TRB. Annual TRB sulfate deposition is lowest at Ogasawara at 1.1 ± 0.2 mg m-2 d-1, and the annual oceanic DMS contribution to sulfate deposition is high, accounting for 1.3 mg m-2 d-1 (20 ± 6%). The contribution of Asian dust was estimated to be 1-5.2 mg m-2 d-1(3-6%), which occurred in a single Asian dust event on the Sea of Japan side.

The contribution of Asian dust in the pedogenesis of ultisols in Southeastern China determined by soil grain size

The present study was conducted to understand the pedogenesis of soils developed on basalts and reveal the impact of Asian dust on soils in subtropical China. Soils developed on basalts in Xinchang-Shengzhou Basin are classified as ultisol and sampled by genetic horizon. For grain size analysis, organic matter was removed from soil samples, and then soil samples were dispersed overnight and followed by ultrasonic treatment. Grain size was measured by a Laser Grain size Analyzer. For isotopic analysis, soil samples were first dried at room temperature and then combusted at 700 °C, digested using an HNO3 + HF mixture and dissolved in a 2 N HCl solution. Sr and Nd isotopes measured on a GV Isoprobe-T thermal ionization mass spectrometer (TIMS). The grain size distribution with a significantly high content of the “basic dust fraction” (10–50 μm fraction) in the upper profiles (0–40 cm) indicates atmospheric deposition onto the surface layers of soils. The patterns of the grain size frequency curves in the upper layer imply that Asian dust has a great impact on soils. The grain size parameters also reflected the influence of Eolian deposits on soils. The 87Sr/86Sr and eNd values for soils show that the near-surface horizons are substantially impacted by dust. The grain size, its parameters, and Sr-Nd isotopes have been marked by Eolian characteristics for the upper layers of soil, while showing a dominant basaltic signature in the lower layers. Besides parent material, accumulation of Asian dust has played an important role in pedogenesis of soils in Southeast China.