Weak transport of atmospheric water-insoluble particulate carbon from South Asia to the inner Tibetan Plateau in the monsoon season.

Carbonaceous particles play a crucial role in atmospheric radiative forcing. However, our understanding of the behavior and sources of carbonaceous particles in remote regions remains limited. The Tibetan Plateau (TP) is a typical remote region that receives long-range transport of carbonaceous particles from severely polluted areas such as South Asia. Based on carbon isotopic compositions (Δ14C/δ13C) of water-insoluble particulate carbon (IPC) in total suspended particle (TSP), PM2.5, and precipitation samples collected during 2020-22 at the Nam Co Station, a remote site in the inner TP, the following results were achieved: First, fossil fuel contributions (ffossil) to IPC in TSP samples (28.60 ± 9.52 %) were higher than that of precipitation samples (23.11 ± 8.60 %), and it is estimated that the scavenging ratio of IPC from non-fossil fuel sources was around 2 times that from fossil fuel combustion during the monsoon season. The ffossil of IPC in both TSP and PM2.5 samples peaked during the monsoon season. Because heavy precipitation during the monsoon season scavenges large amounts of long-range transported carbonaceous particles, the contribution of local emissions from the TP largely outweighs that from South Asia during this season. The results of the IPC source apportionment based on Δ14C and δ13C in PM2.5 samples showed that the highest contribution of liquid fossil fuel combustion also occurred in the monsoon season, reflecting increased human activities (e.g., tourism) on the TP during this period. The results of this study highlight the longer lifetime of fossil fuel-sourced IPC in the atmosphere than that of non-fossil fuel sources in the inner TP and the importance of local emissions from the TP during the monsoon season. The findings provide new knowledge for model improvement and mitigation of carbonaceous particles.

Significant spatial variations of the atmospheric environment at remote site of the Tibetan Plateau - a case study on major ions of precipitation around Nam Co station.

Remote region is normally considered a receptor of long-range transported pollutants. Monitoring stations are important platforms for investigating the atmospheric environment of remote regions. However, the potential contribution of very local sources around these stations may produce important influences on its atmospheric environment, which is still barely studied. In this study, major ions of precipitation were investigated simultaneously at a typical remote station (Nam Co station) and other sites nearby on the Tibetan Plateau (TP) - the so-called "The Third Pole" in the world. The results showed that despite low values compared to those of other remote regions, the concentrations of major ions in precipitation of Nam Co station (e.g., Ca2+: 32.71 µeq/L; [Formula: see text]: 1.73 µeq/L) were significantly higher than those at a site around 2.2 Km away (Ca2+: 11.47 µeq/L; [Formula: see text]: 0.64 µeq/L). This provides direct evidence that atmospheric environment at Nam Co station is significantly influenced by mineral dust and pollutants emitted from surface soil and anthropogenic pollutants of the station itself. Therefore, numbers of other related data reported on the station are influenced. For example, the aerosol concentration and some anthropogenic pollutants reported on Nam Co station should be overestimated. Meanwhile, it is suggested that it is cautious in selecting sites for monitoring the atmospheric environment at the remote station to reduce the potential influence from local sources.

Dust dominates glacier darkening across majority of the Tibetan Plateau based on new measurements.

Rapid retreat and darkening of most glaciers in the Tibetan Plateau (TP) are enhanced by the deposition of light-absorbing particles (LAPs). Here, we provided new knowledge on the estimation of albedo reduction caused by black carbon (BC), water-insoluble organic carbon (WIOC), and mineral dust (MD), based on a comprehensive study of snowpit samples from ten glaciers across the TP collected in the spring of 2020. According to the albedo reductions caused by the three LAPs, the TP was divided into three sub-regions: the eastern and northern margins, Himalayas and southeastern TP, and western to inner TP. Our findings indicated that MD had a dominant role in causing snow albedo reductions across the western to inner TP, with comparable effects to WIOC but stronger effects than BC in the Himalayas and southeastern TP. BC played a more important role in the eastern and northern margins of the TP. In conclusion, the findings of this study emphasize not only the important role of MD in glacier darkening across majority of the TP but also the influence of the WIOC in enhancing glacier melting which indicates the dominant contribution of non-BC components in the LAP-related glacier melting of the TP.

Correction to "Eocene Paleoclimate Evolution under the Background of Warmhouse-Hothouse Conditions in the Continental Fushun Basin: Implications from Magnetic Susceptibility and Color Reflectance".

[This corrects the article DOI: 10.1021/acsomega.2c02445.].

Importance of local non-fossil sources to carbonaceous aerosols at the eastern fringe of the Tibetan Plateau, China: Δ14C and δ13C evidences.

Carbonaceous particles are an important radiative forcing agent in the atmosphere, with large temporal and spatial variations in their concentrations and compositions, especially in remote regions. This study reported the Δ14C and δ13C of total carbon (TC) and water-insoluble particulate carbon (IPC) of the total suspended particles (TSP) and PM2.5 at a remote site of the eastern Tibetan Plateau (TP), a region that is influenced by heavy air pollution from Southwest China. The average organic carbon and elemental carbon concentrations of TSP samples in this study were 3.20 ± 2.38 µg m-3 and 0.68 ± 0.67 µg m-3, respectively, with low and high values in summer and winter, respectively. The fossil fuel contributions of TC in TSP and PM2.5 samples were 18.91 ± 7.22% and 23.13 ± 12.52%, respectively, both of which were far lower than that in Southwest China, indicating the importance of non-fossil contributions from local sources. The δ13C of TC in TSP samples of the study site was -27.06 ± 0.96‰, which is between the values of long-range transported sources (e.g., Southwest China) and local biomass combustion emissions. Therefore, despite the contribution from the long-range transport of particles, aerosols emitted from local biomass combustion also have an important influence on carbonaceous particles at the study site. The findings of this work can be applied to other remote sites on the eastern TP and should be considered in related research in the future.

Eocene Paleoclimate Evolution under the Background of Warmhouse-Hothouse Conditions in the Continental Fushun Basin: Implications from Magnetic Susceptibility and Color Reflectance.

Paleocene-Eocene hyperthermal events are a current research focus in the fields of sedimentology and paleoclimatology. The Fushun Basin in northeast China contains continuous continental Eocene fine-grained rocks, and a series of Eocene hyperthermal events in the Fushun Basin have been identified. Because of the high cost of high-precision isotope data testing, it is necessary to find new and alternative paleoclimate parameters. In this study, Eocene coal and oil shale-bearing layers in the Fushun Basin are used as research objects. The high-precision data of magnetic susceptibility, color reflectance, rock composition, and cluster analyses are used to conduct a vertical comparison in the same category and compare that analysis with the identified Eocene hyperthermal events in the Fushun Basin. The preliminary results show that high-frequency-dependent susceptibility, high color reflectance a* (redness)/L* (lightness) values, and high kaolinite content in the study area have good correspondence with global hyperthermal events and can be used as effective parameters for the identification of continental basin hyperthermal events. The detailed magnetic susceptibility and color reflectance data also reveal that the Eocene strata in the Fushun Basin recorded the Late Lutetian Thermal Maximum (LLTM) and 13 short-term hyperthermal events during the Early Eocene Climatic Optimum (EECO). These results indicate that the parameters of rock physical properties can be used to study the evolution of the paleoclimate in geological history, and it has universal practicability in continental and marine fine-grained sedimentary rocks.

Composition and sources of heavy metals in aerosol at a remote site of Southeast Tibetan Plateau, China.

Knowledge of the elemental composition of aerosols at remote sites is important for evaluating the influence of anthropogenic activities. In this study, the elemental composition and sources of total suspended particles (TSP) at Yaze, a remote site in the southeastern Tibetan Plateau (TP), were investigated. The results showed that the mean elemental concentrations at Yaze were relatively low compared with those in other areas of the TP. Seasonal variations in the studied elements was characterized by low and high concentrations during the monsoon and non-monsoon periods, respectively. The enrichment factors (EFs) for some heavy metals at Yaze were slightly higher than those at Nam Co station (inland TP) but much lower than those at Mt. Yulong (southeastern TP) and in the Indian megacity of Delhi, indicating fewer anthropogenic influences at the study site relative to sites close to severely polluted regions. For the studied elements, three major sources were identified: crustal origins (e.g., Al and Fe), anthropogenic origins (e.g., Zn and Cd) and mixed origins (e.g., As and Bi). Further analysis by potential source contribution functions showed that the local TP was the primary source for elements of crustal origins. Correspondingly, the typical heavy metals were mainly attributed to pollution emitted from anthropogenic activities and transported over long-range from both South and Southeast Asia. This work demonstrates the transport of heavy metals from external sources to remote sites in the southeastern TP. These results are also useful for interpreting the historical profiles of heavy metals in the ice cores of the TP.

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.