Institute of Earth Environment
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Spatial distribution and potential sources of arsenic and water-soluble ions in the snow at Ili River Valley, China
No full textTrace elements and water-soluble ions in snow can be used as indicators to reveal natural and anthropogenic emissions. To understand the chemical composition, characteristics of snow and their potential sources in the Ili River Valley (IRV), snow samples were collected from 17 sites in the IRV from December 2018 to March 2019. Inverse distance weighting, enrichment factor (EF) analysis, and backward trajectory modelling were applied to evaluate the spatial distributions and sources of water-soluble ions and dissolved arsenic (As) in snow. The re-sults indicate that Ca2+ and SO42-were the dominant ions, and the concentrations of As ranged from 0.09 to 0.503 mu g L-1. High concentrations of As were distributed in the northwest and middle of the IRV, and the concentrations of the major ions were high in the west of the IRV. The strong correlation of As with F-, SO42-, and NO2- demonstrates that As mainly originated from coal-burning and agricultural activities. Principal component analysis showed that the ions originated from a combination of anthropogenic and crustal sources. The EFs showed that K+, SO42-, and Mg2+ were mainly influenced by human activities. Backward trajectory cluster analysis suggested that the chemical composition of snow was affected by soil dust transport from the western air mass, the unique terrain, and local anthropogenic activities. These results provide important sci-entific insights for atmospheric environmental management and agricultural production within the IRV
Assessing the Modern Multi-Decadal Scale Aridification Over the Northern China From a Historical Perspective
No full textNorthern China (35 degrees-50 degrees N; 105 degrees-125 degrees E) has experienced a multidecadal aridification since 1950s, which was mainly manifested by multi-decadal scale decreases of regional precipitation and soil moisture, and brought severe influences on societal and economic developments. However, the position of this aridification among the historical aridification events over northern China during the last millennium has not been fully assessed. Furthermore, the contributions from anthropogenic forcings, natural forcings, and internal variability on this aridification have not been quantitatively differentiated. In this study, observations, proxy reconstructions, and model simulations from community Earth system model last millennium ensemble archive were used to assess this aridification from a historical perspective, and differentiate the contributions from different forcings and internal variability. It was found that duration and magnitude of this aridification are more prominent than most of aridifications during the last millennium. The comparisons between control experiment and sensitivity experiments show that the external forcings, especially anthropogenic forcings, result in a significant larger aridification rate than other historical aridifications. Only combined impacts from internal variability (i.e., Pacific Decadal oscillation, PDO and Atlantic Multidecadal oscillation (AMO)) and anthropogenic forcings (e.g., greenhouses gas emission, anthropogenic aerosol emission, and land use cover changes) can result in such a severer aridification than historical aridifications. The results also confirm that the phase shifts of PDO and AMO trigger this aridification over the northern China, and, whether external forcings contribute to these phase shifts were also discussed
Rapid determination of plutonium isotopes in small samples using single anion exchange separation and ICP-MS/MS measurement in NH3-He mode for sediment dating
No full textTo accurately determine ultra-trace Pu isotopes in small environmental samples, we explored ICP-MS/MS in NH3-He mode, and investigated mechanism of U-238 interference removal and measurement sensitivity improvement for plutonium isotopes. The interference of uranium and uranium hydrides was effectively eliminated using 0.4 mL/min NH3 as reaction gas by shifting them to U(NHm)(n)(+) and UH(NHm)(n)(+). The overall interference of uranium was reduced to <2.4 x 10 (-7), while remaining excellent Pu-239 sensitivity (13,900 Mcps/(mg/L)) mainly due to ion focusing effect of Pu by helium gas. On this basis, the purification of plutonium using a single AG1- x 4 column was proved to be sufficient for accurate determination of plutonium isotopes by the developed detection method, and the detection limits for the method were estimated to be 0.16 fg (0.4 mu Bq) for Pu-239, 0.046 fg (0.4 mu Bq) for Pu-240 and 0.039 fg (0.15 mBq) for Pu-241. The method was validated by analyzing plutonium isotopes in certificated reference materials and reported environmental samples of only 1-2 g. The analytical results of ultra-trace Pu isotopes in small amounts (similar to 1 g) of lake sediments obtained by the developed method were successfully applied to sediment dating
Explorations of tire and road wear microplastics in road dust PM2.5 at eight megacities in China
No full textTire and road wear microplastics (TRWMPs) in road dust are a key source of atmospheric particulate matter and have an adverse impact on human health and the environment. In this study, samples of particulate matter with a diameter of 2.5 mu m or less (PM2.5) in road dust were collected from eight megacities in China to determine the TRWMP content, including that of natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). The total abundance of TRWMPs was the highest in Lanzhou (174.7 +/- 17.0 mu g g(-1)), followed by Xi'an (169.3 +/- 23.8 mu g g(-1)), Beijing (107.5 +/- 7.5 mu g g(-1)), Changchun (102.2 +/- 8.4 mu g g(-1)), Chengdu (101.6 +/- 12.9 mu g g(-1)), Guangzhou (98.8 +/- 6.5 mu g g(-1)), Wuhan (96.0 +/- 5.3 mu g g(-1)), and Shanghai (86.1 +/- 30.1 mu g g(-1)). A considerably higher TRWMP fraction in road dust PM2.5 was observed in the northern cities than in the southern cities and is attributable to the higher frictional resistance of roads subjected to less precipitation. The abundance of TRWMPs in the southern cities was dependent on road type, but this dependence was not observed in the northern cities. In the south, road dust PM2.5 on main roads contained more TRWMPs than that on branch roads. Correlation analysis indicated that TRWMPs were associated with tire, road, and break wear. In relation to intracellular oxidative stress factors, higher correlations were observed between TRWMPs and lactate dehydrogenase (r = 0.83) than between TRWMPs and reactive oxygen species (r = 0.59), possibly because TRWMPs destroy the integrity of the cell membrane, with NR exhibiting a higher cytotoxicity than SBR or BR. This study provides evidence that TRWMPs have an adverse impact on human health by inducing cellular oxidative stress. Therefore, further research on TRWMPs in respirable road dust is required
Direct Radiative Effect (DRE) of Dust Aerosols on West African and East Asian Monsoon: The Role of Ocean-Atmosphere Interactions
No full textThe direct radiative effect (DRE) of dust aerosols on the West African and East Asian monsoons is analyzed using the Community Atmosphere Model version 4 containing the dust aerosol parameterization module with and without the coupling of ocean-atmosphere processes, respectively. The atmospheric model (AM) and the ocean-atmosphere coupled model (CM) can both capture the major spatial characteristics of dust aerosols and summer monsoons over West Africa and East Asia. Our results show that the DREs on the West African (WASM) and East Asian summer monsoon (EASM) are more significant in the CM simulations compared to the AM simulations, causing the strengthening of the WASM and weakening of the EASM. The DRE of dust aerosols induces a negative radiative forcing leading to a surface cooling of the downstream ocean of the dust source region when the coupled ocean feedback is added. The distinct DRE of dust aerosols on the WASM and EASM are resulted from the relative locations of the ocean cooling regions to the respective monsoon regions. This study shows the importance of the coupled ocean-atmosphere processes in the DRE and its influences on the WASM and EASM systems
Cenozoic Uplift of Tanggula Range and Tuouohe Basin, Northern Tibet: Insights of the Anisotropy of Magnetic Susceptibility
No full textThe timing and intensity of deformation of the Tanggula Range and Tuotuohe Basin are in debatable but strengthening the research on them is necessary for better understanding the geodynamic models of the Tibet and the tectonic-climate connections during the Cenozoic. Here we present the anisotropy of magnetic susceptibility (AMS) records from the foreland Tuotuohe Basin to understand the tectonic uplift history of the Tanggula Range for the interval of similar to 37-19.7 Ma. Rock magnetic analyses indicate that the main magnetic carrier is paramagnetic and the minor is hematite. Thus, the AMS in the Tuotuohe Section (TS) can be used to track the tectonic strain related to tectonic processes. The distribution direction of the maximum principle susceptibility (K-max) is approximately NW-SE, which intersects at about 10 degrees with the strike of the strata and is nearly parallel to the Tanggula thrust fault system, whereas the minimum principle susceptibility (K-min) is oriented in the NE-SW direction with a girdle distribution. This is consistent with the sedimentary fabric imprinted by the NE-SW shortening direction, representing the earliest deformation stage. AMS data in the TS can be divided into two phases at 30 Ma. From similar to 37 to 30 Ma, the AMS parameters indicate an active tectonic strain and the Tanggula Range uplift induced by the India-Asia convergence, whereas between 30 and 19.7 Ma, the strain is weak compared with the earlier phase. Finally, the weak strain environment between 30 and 19.7 Ma indicated by the AMS indexes of the TS and the paleoelevation evidence from the Tuotuohe Basin all together suggest that an additional 1000-2000 m of surface uplift of the basin may have begun after 19.7 Ma
Cenozoic Uplift of Tanggula Range and Tuouohe Basin, Northern Tibet: Insights of the Anisotropy of Magnetic Susceptibility
No full textThe timing and intensity of deformation of the Tanggula Range and Tuotuohe Basin are in debatable but strengthening the research on them is necessary for better understanding the geodynamic models of the Tibet and the tectonic-climate connections during the Cenozoic. Here we present the anisotropy of magnetic susceptibility (AMS) records from the foreland Tuotuohe Basin to understand the tectonic uplift history of the Tanggula Range for the interval of similar to 37-19.7 Ma. Rock magnetic analyses indicate that the main magnetic carrier is paramagnetic and the minor is hematite. Thus, the AMS in the Tuotuohe Section (TS) can be used to track the tectonic strain related to tectonic processes. The distribution direction of the maximum principle susceptibility (K-max) is approximately NW-SE, which intersects at about 10 degrees with the strike of the strata and is nearly parallel to the Tanggula thrust fault system, whereas the minimum principle susceptibility (K-min) is oriented in the NE-SW direction with a girdle distribution. This is consistent with the sedimentary fabric imprinted by the NE-SW shortening direction, representing the earliest deformation stage. AMS data in the TS can be divided into two phases at 30 Ma. From similar to 37 to 30 Ma, the AMS parameters indicate an active tectonic strain and the Tanggula Range uplift induced by the India-Asia convergence, whereas between 30 and 19.7 Ma, the strain is weak compared with the earlier phase. Finally, the weak strain environment between 30 and 19.7 Ma indicated by the AMS indexes of the TS and the paleoelevation evidence from the Tuotuohe Basin all together suggest that an additional 1000-2000 m of surface uplift of the basin may have begun after 19.7 Ma
Climatic controls on travertine deposition in southern Tibet during the late Quaternary
No full textLarge volumes of travertine deposits are preserved at hydrothermal spring sites on the Tibetan Plateau (TP). Yet, most of these deposits are under-researched with respect to their diagenetic and depositional history and there is still very limited understanding of the tectonic and climatic influences on travertine precipitation in the arid high-altitude setting of Tibet. In this study, a detailed uranium-series dating campaign was carried out for the Qiusang travertine (similar to 4270 m above sea level), southern Tibet that has been previously dated back to 486 thousand years ago (ka). Based on 42 new Th-230/U ages, combined with geomorphological and sedimentological investigations, several travertine zones were identified and distinct travertine depositional phases constrained: 11.7-6.8 ka and similar to 13.4 ka (zone 1), 128-122 ka (zone 2),-193 ka (zone 3),similar to 292 ka and 324 ka (zone 4), > 317 ka (zone 5), ca. 415 to 470 ka (zone 6) and ca. 419 to 445 ka (zone 7). Comparison of these depositional phases with local and regional proxy records suggests that travertine accumulation at Qiusang occurred during main interglacials when monsoon precipitation peaked on the TP. This coincidence, together with a sensitive response of Tibetan hydrothermal spring activity to meteoric recharge, implies that climate controls the precipitation of large travertine volumes on orbital timescales on the plateau. We propose that (i) tectonic activity is of subor-dinate importance and influences travertine precipitation on the TP only episodically and on significantly shorter (i.e. centennial to millennial) timescales related to the recurrence rates of large earthquakes and that (ii) intensive monsoonal-driven groundwater recharge is required on top of tectonic activity for generating volu-metrically significant travertine accumulations. Because of the high precipitation rates typical for hydrothermal spring carbonates, we conclude that travertine deposits on the TP could be utilized as valuable high-resolution proxy records of peak monsoon conditions in the currently arid to semi-arid landscape.& nbsp;Furthermore, the Qiusang travertine zone 7 is terraced and the travertine layers adjusted to a paleo-riverbed elevation similar to 30 m above the current river, allowing us to constrain fluvial incision to-0.07 m/ka for the south -central sector of the TP since the Mid-Pleistocene. The abundant travertine occurrences in Tibet in combination with uranium-series dating can thus also provide detailed insights into earth surface dynamics and landscape evolution on the world highest plateau
Accumulation of aeolian sediments around the Tengger Desert during the late Quaternary and its implications on interpreting chronostratigraphic records from drylands in north China
No full textChronostratigraphic records in the drylands of north China provide essential archives to reveal the dynamic connections between climate changes and behaviours of aeolian systems. This study presents a detailed investigation of aeolian sediment accumulation around the Tengger Desert during the late Quaternary, comprising of grain-size characteristics and sources, sediment types and burial ages, and potential responses to external and localised forces. A combination of previously published chronostratigraphic records and 91 newly dated optically stimulated luminescence (OSL) samples collected from multiple sites covering a wide region of the south margin of the desert are used to constrain the accumulation of aeolian sediments during the late Quaternary. The prevailing strong near-surface winds at 22-19 ka, 18-14 ka, 13-10 ka, and 3-0 ka are found to be in anti-phase relation with the strength of the East Asia summer monsoon (EASM). The widespread attenuation of aeolian activity occurred between 7 and 3 ka. The accumulation of aeolian sediments during the past 250 ka has been controlled by multiple factors, including wind, aridity, sediment availability, and preservation capacity. We demonstrate that the interpretation of chronostratigraphic records is significantly affected by the number of available records, which emphasises the importance of sampling at multiple sites. The synchronous accumulation of aeolian sand and sandy loess at certain periods and the significant overlapping of volume percentage distributions at certain grain-size intervals between the two types of sediments indicate that their responses to external forces may not be independent and that the palaeoclimatic significance of sandy loess accumulated in the desert-loess transition zone requires a reassessment. (C) 2021 Elsevier Ltd. All rights reserved
In-vitro oxidative potential and inflammatory response of ambient PM2.5 in a rural region of Northwest China: Association with chemical compositions and source contribution
No full textOverproduction of reactive oxygen species (ROS) induced by atmospheric particles and subsequent inflammatory responses are considered as one of the most important pathological mechanisms with regard to the adverse effects of air pollution exposure. In this study, fine particulate matter (PM2.5) samples were collected at a rural site in Guanzhong Basin, Northwest China, in both summer (August 3-23, 2016) and winter (January 5-February 1, 2017). Then, human bronchial epithelial BEAS-2B cells were exposed to the PM2.5, cultured for 24 h, and then assayed for particle-induced ROS and three inflammatory factors (tumor necrosis-alpha (TNF-alpha), interleukin-6 (IL-6), and interferon-gamma (IFN-gamma)) in vitro. The oxidative potential (OP) induced by winter PM2.5 samples was higher than that induced by summertime samples, whereas inflammatory values showed contrasting seasonal variations. Both OP and inflammatory factors were significantly correlated with most chemical compounds in winter, but not in summer, which was thought to be related mainly to the higher contribution from secondary aerosols formed during the warm season. Source apportionment results showed secondary aerosols formation have significant contribution to OP of PM2.5 in both seasons, but the dominant oxidation processes is different. Secondary nitrates-related process was the major contributors regulating the OP in winter; however, secondary sulfates formation were mainly responsible for the ROS responses in summer. For primary emission, biomass burning, rather than coal emission or vehicle exhaust, was the significant source for OP of PM2.5 in winter. In most cases, the source contribution of each inflammatory factor was similar to that of the ROS. Our results highlighted the significant health risk of atmospheric aerosols from biomass burning in the rural regions of Guanzhong Basin, Northwest China