Atmospheric microplastics : A review on current status and perspectives

Microplastics have recently been detected in the atmosphere of urban, suburban, and even remote areas far away from source regions of microplastics, suggesting the potential long-distance atmospheric transport for microplastics. There still exist questions regarding the occurrence, fate, transport, and effect of atmospheric microplastics. These questions arise due to limited physical analysis and understanding of atmospheric microplastic pollution in conjunction with a lack of standardized sampling and identification methods. This paper reviews the current status of knowledge on atmospheric microplastics, the methods for sample collection, analysis and detection. We review and compare the methods used in the previous studies and provide recommendations for atmospheric microplastic sampling and measurement. Furthermore, we summarize the findings related to atmospheric microplastic characteristics, including abundance, size, shapes, colours, and polymer types. Microplastics occur in the atmosphere from urban to remote areas, with an abundance/deposition spanning 1–3 orders of magnitude across different sites. Fibres and fragments are the most frequently reported shapes and the types of plastic which generally aligns with world plastic demand. We conclude that atmospheric microplastics require further research and greater understanding to identify its global distributions and potential exposure to human health through further field sampling and implementation of standardized analytical protocols

Microplastics in glaciers of the Tibetan Plateau : evidence for long-range transport of microplastics

Microplastics are globally prevalent on a large scale in various marine and terrestrial environments, including Arctic snow and precipitation in protected areas of the United Sates. However, reports of microplastics from glaciers are rare, especially for the Tibetan Plateau (TP), which is widely known as the world's Third Pole and Asian Water Tower. Adjacent to human settlements in South Asia, East China, and Central Asia, the TP features regular cross-border air pollution (e.g., black carbon and mercury), which can affect its vulnerable and pristine environments. In previous studies, abundant microplastics have been reported from Tibetan rivers/lakes water and sediments, and surface soils. We detected microplastics in glacier surface snow on the TP, which were isolated from the impact of human activities, indicating that microplastics can be transported over long distances. This evidence is expected to be significant for understanding the atmospheric transport of microplastics to the TP, and provides a global perspective on the microplastic cycle

Cryosphere as a temporal sink and source of microplastics in the Arctic region

Microplastics (MPs) pollution has become a serious environmental issue of growing global concern due to the increasing plastic production and usage. Under climate warming, the cryosphere, defined as the part of Earth's layer characterized by the low temperatures and the presence of frozen water, has been experiencing significant changes. The Arctic cryosphere (e.g., sea ice, snow cover, Greenland ice sheet, permafrost) can store and release pollutants into environments, making Arctic an important temporal sink and source of MPs. Here, we summarized the distributions of MPs in Arctic snow, sea ice, seawater, rivers, and sediments, to illustrate their potential sources, transport pathways, storage and release, and possible effects in this sentinel region. Items concentrations of MPs in snow and ice varied about 1–6 orders of magnitude in different regions, which were mostly attributed to the different sampling and measurement methods, and potential sources of MPs. MPs concentrations from Arctic seawater, river/lake water, and sediments also fluctuated largely, ranging from several items of per unit to >40,000 items m−3, 100 items m−3, and 10,000 items kg−1 dw, respectively. Arctic land snow cover can be a temporal storage of MPs, with MPs deposition flux of about (4.9–14.26) × 108 items km−2 yr−1. MPs transported by rivers to Arctic ocean was estimated to be approximately 8–48 ton/yr, with discharge flux of MPs at about (1.65–9.35) × 108 items/s. Average storage of MPs in sea ice was estimated to be about 6.1×1018 items, with annual release of about 5.1×1018 items. Atmospheric transport of MPs from long-distance terrestrial sources contributed significantly to MPs deposition in Arctic land snow cover, sea ice and oceanic surface waters. Arctic Great Rivers can flow MPs into the Arctic Ocean. Sea ice can temporally store, transport and then release MPs in the surrounded environment. Ocean currents from the Atlantic brought high concentrations of MPs into the Arctic. However, there existed large uncertainties of estimation on the storage and release of MPs in Arctic cryosphere owing to the hypothesis of average MPs concentrations. Meanwhile, representatives of MPs data across the large Arctic region should be mutually verified with in situ observations and modeling. Therefore, we suggested that systematic monitoring MPs in the Arctic cryosphere, potential threats on Arctic ecosystems, and the carbon cycle under increasing Arctic warming, are urgently needed to be studied in future

Black carbon and organic carbon dataset over the Third Pole

The Tibetan Plateau and its surroundings, also known as the Third Pole, play an important role in the global and regional climate and hydrological cycle. Carbonaceous aerosols (CAs), including black carbon (BC) and organic carbon (OC), can directly or indirectly absorb and scatter solar radiation and change the energy balance on the Earth. CAs, along with the other atmospheric pollutants (e.g., mercury), can be frequently transported over long distances into the inland Tibetan Plateau. During the last decades, a coordinated monitoring network and research program named “Atmospheric Pollution and Cryospheric Changes” (APCC) has been gradually set up and continuously operated within the Third Pole regions to investigate the linkage between atmospheric pollutants and cryospheric changes. This paper presents a systematic dataset of BC, OC, water-soluble organic carbon (WSOC), and water-insoluble organic carbon (WIOC) from aerosols (20 stations), glaciers (17 glaciers, including samples from surface snow and ice, snow pits, and 2 ice cores), snow cover (2 stations continuously observed and 138 locations surveyed once), precipitation (6 stations), and lake sediment cores (7 lakes) collected across the Third Pole, based on the APCC program. These data were created based on online (in situ) and laboratory measurements. High-resolution (daily scale) atmospheric-equivalent BC concentrations were obtained by using an Aethalometer (AE-33) in the Mt. Everest (Qomolangma) region, which can provide new insight into the mechanism of BC transportation over the Himalayas. Spatial distributions of BC, OC, WSOC, and WIOC from aerosols, glaciers, snow cover, and precipitation indicated different features among the different regions of the Third Pole, which were mostly influenced by emission sources, transport pathways, and deposition processes. Historical records of BC from ice cores and lake sediment cores revealed the strength of the impacts of human activity since the Industrial Revolution. BC isotopes from glaciers and aerosols identified the relative contributions of biomass and fossil fuel combustion to BC deposition on the Third Pole. Mass absorption cross sections of BC and WSOC from aerosol, glaciers, snow cover, and precipitation samples were also provided. This updated dataset is released to the scientific communities focusing on atmospheric science, cryospheric science, hydrology, climatology, and environmental science. The related datasets are presented in the form of excel files. BC and OC datasets over the Third Pole are available to download from the National Cryosphere Desert Data Center (10.12072/ncdc.NIEER.db0114.2021; Kang and Zhang, 2021)

Simulation and Assessment of Future Glacial Lake Outburst Floods in the Poiqu River Basin, Central Himalayas

A glacial lake outburst flood (GLOF) is a typical glacier-related hazard in high mountain regions. In recent decades, glacial lakes in the Himalayas have expanded rapidly due to climate warming and glacial retreat. Some of these lakes are unstable, and may suddenly burst under different triggering factors, thus draining large amounts of water and impacting downstream social and economic development. Glacial lakes in the Poiqu River basin, Central Himalayas, have attracted great attention since GLOFs originating there could have a transboundary impact on both China and Nepal, as occurred during the Cirenmaco GLOF in 1981 and the Gongbatongshaco GLOF in 2016. Based on previous studies of this basin, we selected seven very high-risk moraine-dammed lakes (Gangxico, Galongco, Jialongco, Cirenmaco, Taraco, Beihu, and Cawuqudenco) to simulate GLOF propagation at different drainage percentage scenarios (i.e., 25%, 50%, 75%, and 100%), and to conduct hazard assessment. The results show that, when any glacial lake is drained completely or partly, most of the floods will enter Nepal after raging in China, and will continue to cause damage. In summary, 57.5 km of roads, 754 buildings, 3.3 km2 of farmland, and 25 bridges are at risk of damage due to GLOFs. The potentially inundated area within the Chinese part of the Poiqu River basin exceeds 45 km2. Due to the destructive impacts of GLOFs on downstream areas, appropriate and effective measures should be implemented to adapt to GLOF risk. We finally present a paradigm for conducting hazard assessment and risk management. It uses only freely available data and thus is easy to apply

Sink or source? Methane and carbon dioxide emissions from cryoconite holes, subglacial sediments, and proglacial river runoff during intensive glacier melting on the Tibetan Plateau

High Mountain Asia glaciers are currently ignored in the estimation of global greenhouse gas budgets (e.g., methane (CH4) and carbon dioxide (CO2)). Similar to the Asian Water Tower and Third Pole, the Tibetan Plateau (TP) hosts the largest volume of glaciers outside the polar regions. These glaciers contain large reservoirs of organic carbon that can influence glacial ecosystems under rapid melting. However, no data exist on the current footprint of CH4 and CO2 from glaciers in the TP. Here, we report in situ observations of CH4 and CO2 fluxes for glacial cryoconite holes, subglacial sediments, and proglacial river runoff across the TP. Our results indicate that cryoconite holes and subglacial sediments can accelerate the export of greenhouse gasses during the melting season due to intensive glacier melting. However, to some extent, proglacial river runoff can be a significant sink of atmospheric CO2; this fact was not identified in previous studies. Our findings suggest that variations (source or sink) of greenhouse gasses from TP glacial basins should be considered in regional CH4 and CO2 budgets under climate warming

Current status and future perspectives of microplastic pollution in typical cryospheric regions

The cryosphere is the term used to describe the frozen areas of the Earth, including all forms of snow and ice, which are primarily influenced by anthropogenic pollutants through atmospheric transport. In this review, we described the current status of newly emergent pollutant-microplastics-in the snow and ice of typical cryospheric regions (e.g., Arctic, Antarctic, Alps, Tibetan Plateau, and Andes), discussed their transport pathways, and provided perspectives for future research. A brief summary of snow and ice sampling, pretreatment, and the identification of microplastics in cryospheric regions suggested that standard procedures were inadequate and urgently required improvement. Microplastics were widely distributed in snow and ice across the typical cryospheric regions, indicating the ubiquitous distribution of microplastics in such environments. However, the abundance, size distribution, shape, and polymer composition of the microplastics in snow and ice showed significant differences. Sea ice was especially important for the temporal storage, transport, and release of microplastics in the Arctic and Antarctic. Microplastics in land snow cover and mountain glaciers emphasized the importance of atmospheric transport in the transferal of microplastics to cryospheric regions. In particular, the non-polar cryospheric regions (e.g., Tibetan Plateau, Andes, or Alps) were highlighted as important receptors of mid-latitude emissions of microplastics, which might indicate a future climatic risk considering the ability of microplastics to absorb radiation and accelerate the melting of snow. Microplastics retrieved from mountain glacier ice cores may also provide new insights into the historical variations of anthropogenic pollutants. The potential impact of microplastics in snow and ice on the carbon cycle and the climatic risk needs to be further addressed in the future

Data on DOC and N from the Muz taw glacier in Central Asia

This Data in Brief article provides a supplementary information to the dissolved organic carbon and nitrogen from the snow of Muz taw glacier in the Central Asia, which is related to the scientific article titled with “Characterization, sources and transport of dissolved organic carbon and nitrogen from a glacier in the Central Asia”[1]. Meanwhile, major ions (including Na+, K+, NH4+, Ca2+, Mg2+, Cl−, SO42−, NO3−, and NO2−) were also reported. These data were analysed using descriptive statistics such as correlations and principle component analysis. Additionally, we conducted a literature review on DOC and N concentrations for the comparison. This article also presents the analysis data of the mass absorption cross section of DOC in snow.ISSN:2352-340

Impacts of the active layer on runoff in an upland permafrost basin, northern Tibetan Plateau

<div><p>The paucity of studies on permafrost runoff generation processes, especially in mountain permafrost, constrains the understanding of permafrost hydrology and prediction of hydrological responses to permafrost degradation. This study investigated runoff generation processes, in addition to the contribution of summer thaw depth, soil temperature, soil moisture, and precipitation to streamflow in a small upland permafrost basin in the northern Tibetan Plateau. Results indicated that the thawing period and the duration of the zero-curtain were longer in permafrost of the northern Tibetan Plateau than in the Arctic. Limited snowmelt delayed the initiation of surface runoff in the peat permafrost in the study area. The runoff displayed intermittent generation, with the duration of most runoff events lasting less than 24 h. Precipitation without runoff generation was generally correlated with lower soil moisture conditions. Combined analysis suggested runoff generation in this region was controlled by soil temperature, thaw depth, precipitation frequency and amount, and antecedent soil moisture. This study serves as an important baseline to evaluate future environmental changes on the Tibetan Plateau.</p></div

(a) Variability of thaw depths in summer, (b) thaw depth versus the square root of accumulated degree days of thaw (ADDT^0.5) predicted by Stefan equation in summer 2014 and 2015 (bars indicate one standard deviation), thaw depth versus (c) ADDT^0.5 of soil temperature and (d) unfrozen soil moisture at a depth of 20 cm.

<p>(a) Variability of thaw depths in summer, (b) thaw depth versus the square root of accumulated degree days of thaw (ADDT^0.5) predicted by Stefan equation in summer 2014 and 2015 (bars indicate one standard deviation), thaw depth versus (c) ADDT^0.5 of soil temperature and (d) unfrozen soil moisture at a depth of 20 cm.</p