图文摘要 | Graphical abstract
导读 | Introduction
微塑料（MPs）广泛分布在各种环境基质中，包括水体，沉积物，土壤，生物，大气等。但关于偏远地区冰川中微塑料的报道却很罕见，尤其是被广泛称为世界第三极和亚洲水塔的青藏高原（TP）。TP毗邻南亚、中国东部和中亚的人类密集区，已有研究表明大气污染物会跨境传输（如黑碳和汞），这可能影响其脆弱的原始环境。本研究在TP冰川上的表雪中检测到了MPs，这些冰川与人类活动的影响隔绝，表明MPs可以被长距离运输。今天，就让我们一起来了解MPs在不同环境基质中的全球污染现状，以及在TP冰川上的特征。
Microplastics (MPs) are widely distributed in a variety of environmental matrices, including water, sediment, soil, biology, and atmosphere. However, reports of microplastics in glaciers in remote areas are rare, especially on the Tibetan Plateau (TP), widely known as the world's third pole and Asia's water tower. TP is adjacent to human settlements in South Asia, eastern 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 this study, MPs were detected in surface snow on TP glaciers that are isolated from the effects of human activities, suggesting that MPs can be transported over long distances. Today, let us understand the current status of global contamination of MPs in different environmental matrices and their characterization on TP glacier.
一、全球水体中的MPs | MPs in freshwater worldwide
MPs研究起源于海洋，后逐渐转入陆地生态环境中。对全球淡水环境MPs研究统计发现：淡水中的MPs主要由PP和PE组成，主要是白色和透明的纤维，并且以粒径小于1毫米的MPs为主。在大塑料破碎和降解过程中会释放添加剂，并且会与其他污染物结合产生毒性。我们认为MPs污染的主要来源是人类活动，包括污水排放和轮胎磨损。同时，大气传输和沉积，包括降水输入，也是造成淡水系统中MPs污染的原因。
The study of MPs originated in the ocean, and then gradually transferred to terrestrial ecological environments. Statistics from studies of MPs in global freshwater environments reveal that MPs in freshwater consist mainly of PP and PE, which are mainly white and transparent fibers, and are dominated by MPs with particle size less than 1 mm. Additives are released during the fragmentation and degradation of large plastics and can combine with other contaminants to produce toxicity. We believe that the main sources of MPs pollution are human activities, including sewage discharge and tire wear. Also, atmospheric transport and deposition, including precipitation input, contribute to MPs contamination in freshwater systems.
图1 淡水生态系统中微塑料的运输概念图
Fig. 1 The concept figure of microplastic transportation in freshwater systems
二、全球沉积物中的MPs| MPs in sediments worldwide
目前对河流和湖泊沉积物中MPs的研究较多且细致，而对水库沉积物的关注相对较少。淡水沉积物中的MPs的平均丰度在不同地区表现出不同的特征和数量。纤维是淡水沉积物中最常见的MPs形状。与淡水水体相似，其颗粒大小以<1毫米为主，最常见的颜色是白色和透明。对于淡水沉积物中的MPs，PE是主要的聚合物，其次是PP和PS，而且不同地区的化学成分差异很大。来自陆地上大型塑料制品的次级MPs构成淡水沉积物中MPs的主要来源。由于其多源性，无论是人口密度还是工业活动或废水处理厂的位置，似乎都不能作为淡水沉积物中MPs污染空间分布的良好指标。水动力条件、降雨和洪水事件对MPs在淡水沉积物中的空间分布有叠加效应。
Current studies have investigated MPs in river and lake sediments in great detail, while relatively little attention has been paid to reservoir sediments. The average abundance of MPs in freshwater sediments exhibits different characteristics and amounts in different regions. Fibers are the most common shape of MPs in freshwater sediments. Similar to freshwater water bodies, their particle size is predominantly < 1 mm and the most common colors are white and transparent. For MPs in freshwater sediments, PE was the dominant polymer, followed by PP and PS, and the chemical composition varied considerably from region to region. Secondary MPs from large plastics on land constitute the main source of MPs in freshwater sediments. Due to their multiple sources, neither population density nor the location of industrial activities or wastewater treatment plants seem to be good indicators of the spatial distribution of MPs contamination in freshwater sediments. Hydrodynamic conditions, rainfall and flooding events have a superimposed effect on the spatial distribution of MPs in freshwater sediments.
图2 截止2020年2月已公布的全球淡水沉积物中微塑料污染的研究
Fig. 2 Global studies of microplastics pollution in freshwater sediment published to February 2020 (based on 38 studies).
三、全球土壤中的MPs | MPs in soil worldwide
目前，土壤中的MPs研究进展受限于固有的技术不一致和分析复杂基质中的颗粒的困难，而且关于土壤环境中MPs的发生和分布的研究仍然非常少、特别是在非洲、南美洲和大洋洲。水生环境和土壤中的MPs的特征和组成的一致性表明它们可能共享来源和交换MPs。广泛而多样的MPs不断填充土壤，导致MPs在土壤中的积累。有限的研究也表明，MPs与它们所吸收的污染物的结合和相互作用可能会影响土壤的健康和功能，甚至是沿着食物链迁移。MPs的产生和对土壤的影响取决于它们的表面形貌、化学组成和自然条件。
At present, the progress in the investigate of MPs in soils is limited by inherent technical inconsistencies and difficulties in analyzing particles in complex matrices, and studies on the occurrence and distribution of MPs in soil environments remain very few, especially in Africa, South America, and Oceania. The consistency in the characteristics and composition of MPs in aquatic environments and soils suggests that they may share sources and exchange MPs. extensive and diverse MPs continuously populate soils, leading to the accumulation of MPs in soils. Limited studies have also shown that the binding and interaction of MPs with the contaminants they take up may affect soil health and function, even as they transport along the food chain. The occurrence and impact of MPs on soils depends on their morphology, chemical composition, and natural factors.
图3微塑料在土壤生态系统中的影响和潜在风险
Fig. 3 Effects and potential risks of microplastics in soil ecosystems.
四、全球大气中的MPs | MPs in atmosphere worldwide
对大气MPs的研究是最少的。总悬浮颗粒物和大气沉积物，包括灰尘、降雨和雪的样本，是大气微塑料研究的环境载体。大气采样分为主动和被动两种方法。根据样品类型和识别方法，前处理流程包括筛分、消化、密度分离、过滤和干燥。使用立体显微镜、傅里叶变换红外光谱、扫描电子显微镜、拉曼光谱和液相色谱串联质谱法，可以测量大气微塑料的特征，包括颗粒粒径分布、形状、颜色、表面形态和聚合物成分。激光直接红外光谱法，热化学方法和质谱法是识别大气中微塑料的潜在方法。目前，估算大气中微塑料排放、运输和沉积的通量的模型正处于初步开发阶段；模型的应用将加强我们对基于模拟和观测数据的全球"微塑料循环"的理解。
The investigation of atmospheric MPs is minimal. The total suspended particles and atmospheric deposition, including dust, rainfall, and snow samples, are the environmental carriers for atmospheric microplastic studies. There are active and passive samplingmethods. Pretreatment depends on sample types and identification methods and includes sieving, digestion, density separation, filtration, and drying. The measured features for atmospheric microplastics include particle size distributions, shapes, colors, surface morphology, and polymer compositions,using stereomicroscopes, Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, and liquid chromatographytandem mass spectrometry. Laser direct infrared spectroscopy and thermochemical methods coupled with mass spectrometry are potential methods for identifying atmospheric microplastics. Currently, models for estimating the fluxes of atmospheric microplastic emission, transport, and deposition are in the initial stages of development; their implementation will enhance our understanding of the “microplastic cycle” globally based on simulated and observed data.
图4大气微塑料的研究点。(a)全球进行大气微塑料研究的地点；(b)、(c)和(d)，与(a)中三个黑色虚线框对应的三个区域。蓝色、红色和绿色的点分别代表主动采样、被动采样和两者。点的大小代表大气中微塑料的最小极限尺寸。如果在一个地点进行了多项研究，则选择最小尺寸。NA："不适用"。海洋上的绿线代表巡航线，线上的蓝点代表采样站。监测断面代表航行时的取样，每条黑/红线采集一次样品。
Fig. 4 Locations of studies on atmospheric microplastics. (a) Locations where atmospheric microplastic studies have been conducted around the globe; (b), (c), and (d), three areas corresponding to the three black dotted boxes in (a). The blue, red, and green dots represent active sampling, passive sampling, and both of them, respectively. Dot sizes represent the minimum limit size of atmospheric microplastics identified from the published literature. The minimum size was selected if multiple studies were conducted on one site. NA: “not applicable.” The green lines on the ocean represent cruise lines and the blue dots on the line represent sampling stations. The monitoring transects represent sampling while sailing, and samples were collected once for each black/red line.
五、青藏高原冰川上的MPs特征 | The characteristic of MPs in glacier in the Tibetan Plateau
青藏高原上两条典型冰川上的MPs丰度为650-920个/升，相比已有研究，本研究结果处于中高水平。MPs以尺寸<100μm，纤维状为主，主要的颜色是黑色，红色，绿色和蓝色。聚合物类型以PA, PE, Rubber为主。颗粒扩散模型表明，沉积在所研究的冰川上的MPs的大气运输主要来自中亚、北非（秋季）、穿越中欧和远至大西洋（冬季和春季），在北印度洋上空下降并向俄罗斯上升（夏季）。模拟结果可能表明，TP冰川上的MPs可能源于短距离和长距离传输，因为在TP高海拔地区的人类活动很少。我们的研究结果对了解微塑料在大气中向TP的迁移具有重要意义，并且提供了一个关于微塑料循环的全球视角。
The abundance of MPs on the two typical glaciers on TP was 650-920 items/L, and the results of the present study are in the middle to high level compared to the existing studies. The MPs are mainly fibers with size < 100 μm, and the main colors are black, red, green and blue. The polymer types were mainly PA, PE, and Rubber. Particle dispersion models suggest that atmospheric transport of MPs deposited on the studied glaciers comes mainly from Central Asia, North Africa (autumn), across Central Europe and as far as the Atlantic Ocean (winter and spring), descending over the Northern Indian Ocean and ascending towards Russia (summer). Simulation results may indicate that MPs on TP glaciers may originate from both short and long-range transport, as there is minimal human activity at high altitudes in TP. Our results have important implications for understanding the atmospheric transport of microplastics to TP and provide a global perspective on the microplastic cycle.
图5青藏高原冰川表雪中测得的微塑料。（a）和（b）是到达老虎沟冰川和枪勇冰川的100、10和1微米MPs颗粒的大气扩散模型。在（a）图中，测量的聚合物的缩写可以参考SI中的表S2。在(b)部分，MPs颗粒被建模为球形，密度为1g/cm3，沉降速度用斯托克斯定律计算（分别为0.3、0.003和0.00003米/秒）。使用HYSPLIT第5版完成建模，使用GDAS 1度的全球气象数据，在后向模式下，距地面50、100和500米处连续排放168小时。
Fig. 5 Microplastics measured from glacier snow in the Tibetan Plateau. (a), and (b) atmospheric particle dispersion modeling of 100, 10, and 1μm MP particles arriving at the Laohugou Glacier and Qiangyong Glacier. In part (a), the abbreviations for the measured polymers can be referred from Table S2 in SI. In part (b), MP particles were modeled as spherical with a density of 1g/cm3, and settling velocities were calculated using the Stokes law (0.3, 0.003, and 0.00003m/s, respectively). Modeling was completed using HYSPLIT version 5 using the GDAS 1 degree archived global meteorology and run in the backward mode with a continuous tracer plume emission for 168h at 50, 100, and 500m above ground level.
总结 | Conclusions
TP包含极地以外的最大体积的冰川，其中大部分正在经历快速退缩。冰川可以提供对空气污染物（包括MPs，或黑碳）长距离（或全球范围）大气传输的新认知，因为它们极高的海拔高度，独特的气象（风）条件和干湿（雪）沉积过程。MPs在冰川中的积累或从融化的冰川中的释放可能提供迄今为止被忽视的重要信息，如高海拔MPs传输动态（形状、大小、普遍性和历史变化），以及可能的大气来源识别。由于冰川目前正在退缩，这些小颗粒将被释放到水生生态系统中。MPs对TP和其他偏远地区的生态系统可能造成的污染和影响越来越令人担忧，由于它们能够吸收太阳辐射并加速融化，可能会带来未来的气候风险。在未来应加强对冰冻圈中的MPs的研究，并奠定纳米塑料分析的基础。减轻聚合物向空气和水生生态系统的排放应是一项普遍责任，以避免超过关键的环境阈值浓度。
The TP contains the largest volume of glaciers outside the polar regions, most of which are undergoing rapid retreat. Glaciers can provide insight into the long-range (or global-scale) atmospheric transport of air pollutants (including MPs, or black carbon), owing to their extremely high elevation, meteorological (wind) conditions, and unique dry and wet (snow) deposition processes. MPs deposition, accumulation in glaciers, or release from melting glaciers may provide important information that has so far been neglected, such as high-altitude MP transport dynamics (shape, size, ubiquity, and historical variations), and possible atmospheric source identification. As glaciers are currently retreating, these small particles will be released into aquatic ecosystems. The possible contamination and impacts of MPs on the ecosystems in the TP and other remote areas are increasingly concerning, and may pose a future climatic risk due to their ability to absorb solar radiation and accelerate melting. Technological developments will enhance the study of MPs in the cryospheric environment in the future, and laying the foundation into nanoplastic analysis. Mitigating the emissions of polymers into the air and aquatic ecosystems should be a universal responsibility to avoid exceeding critical environmental threshold concentrations.
扫二维码 | 查看原文
https://www.sciencedirect.com/science/article/pii/S0048969720371655?via%3Dihub
本文内容来自ELSEVIER旗舰期刊Sci Total Environ第758卷发表的论文：
Y.Zhang,T. Gao, S. Kang, S. Allen, X. Luo, D. Allen. Microplastics in glaciers of the Tibetan Plateau: Evidence for the long-range transport of microplastics. Sci 143634Total Environ. 758, 164317.
DOI: https://doi.org/10.1016/j.scitotenv.2020.143634
第一作者/通讯作者：
张玉兰 研究员
中国科学院西北生态环境资源研究院
在中国科学院青藏高原研究所获得博士学位，现为中国科学院西北生态环境资源研究院研究员。主要研究方向为冰冻圈化学及其气候环境影响。以第一作者或共同作者在Science of the Total Environment、Environmental Pollution、Earth Science Reviews等国际期刊发表论文53篇。
主要作者：康世昌 研究员
中国科学院西北生态环境资源研究院
国家杰出青年科学基金获得者，现为中国科学院西北生态环境资源研究院副院长、冰冻圈科学国家重点实验室主任，主要从事青藏高原冰芯气候和环境记录、雪冰和大气化学特征以及现代冰川和气候变化研究工作。曾任国际期刊“Atmospheric Research”副主编、现任国内核心期刊《冰川冻土》主编，先后担任国际冰川学会（IGS）理事，气候与冰冻圈计划（CliC）指导委员会成员，任IPCC第六次报告《海洋与冰冻圈特别报告》的领衔作者。先后参加南极和北极科考，组织或参加极高海拔的野外科学考察40多次。
转自：“蔻享学术”微信公众号
如有侵权，请联系本站删除！
