We present a new method for chemical characterization of micro- and nanoplastics based on thermal desorption–proton transfer reaction–mass spectrometry. The detection limit for polystyrene (PS) ...obtained is <1 ng of the compound present in a sample, which results in 100 times better sensitivity than those of previously reported by other methods. This allows us to use small volumes of samples (1 mL) and to carry out experiments without a preconcentration step. Unique features in the high-resolution mass spectrum of different plastic polymers make this approach suitable for fingerprinting, even when the samples contain mixtures of other organic compounds. Accordingly, we got a positive fingerprint of PS when just 10 ng of the polymer was present within the dissolved organic matter of snow. Multiple types of microplastics (polyethylene terephthalate (PET), polyvinyl chloride, and polypropylene carbonate), were identified in a snowpit from the Austrian Alps; however, only PET was detected in the nanometer range for both snowpit and surface snow samples. This is in accordance with other publications showing that the dominant form of airborne microplastics is PET fibers. The presence of nanoplastics in high-altitude snow indicates airborne transport of plastic pollution with environmental and health consequences yet to be understood.
Methane is a powerful greenhouse gas and its biological conversion in marine sediments, largely controlled by anaerobic oxidation of methane (AOM), is a crucial part of the global carbon cycle. ...However, little is known about the role of iron oxides as an oxidant for AOM. Here we provide the first field evidence for iron-dependent AOM in brackish coastal surface sediments and show that methane produced in Bothnian Sea sediments is oxidized in distinct zones of iron- and sulfate-dependent AOM. At our study site, anthropogenic eutrophication over recent decades has led to an upward migration of the sulfate/methane transition zone in the sediment. Abundant iron oxides and high dissolved ferrous iron indicate iron reduction in the methanogenic sediments below the newly established sulfate/methane transition. Laboratory incubation studies of these sediments strongly suggest that the in situ microbial community is capable of linking methane oxidation to iron oxide reduction. Eutrophication of coastal environments may therefore create geochemical conditions favorable for iron-mediated AOM and thus increase the relevance of iron-dependent methane oxidation in the future. Besides its role in mitigating methane emissions, iron-dependent AOM strongly impacts sedimentary iron cycling and related biogeochemical processes through the reduction of large quantities of iron oxides.
Plastic materials are increasingly produced worldwide with a total estimated production of >8300 million tonnes to date, of which 60% was discarded. In the environment, plastics fragment into smaller ...particles, e.g. microplastics (size < 5 mm), and further weathering leads to the formation of functionally different contaminants – nanoplastics (size <1 μm). Nanoplastics are believed to have entirely different physical (e.g. transport), chemical (e.g. functional groups at the surface) and biological (passing the cell membrane, toxicity) properties compared to the micro- and macroplastics, yet, their measurement in the environmental samples is seldom available. Here, we present measurements of nanoplastics mass concentration and calculated the deposition at the pristine high-altitude Alpine Sonnblick observatory (3106 MASL), during the 1.5 month campaigh in late winter 2017. The average nanoplastics concentration was 46.5 ng/mL of melted surface snow. The main polymer types of nanoplastics observed for this site were polypropylene (PP) and polyethylene terephthalate (PET). We measured significantly higher concentrations in the dry sampling periods for PET (p < 0.002) but not for PP, which indicates that dry deposition may be the preferential pathway for PET leading to a gradual accumulation on the snow surfaces during dry periods. Air transport modelling indicates regional and long-range transport of nanoplastics, originating preferentially from European urban areas. The mean deposition rate was 42 (+32/-25) kg km−2 year−1. Thus more than 2 × 1011 nanoplastics particles are deposited per square meter of surface snow each week of the observed period, even at this remote location, which raises significant toxicological concerns.
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•We detected nanoplastics of different types at a remote high-altitude site.•The average nanoplastics concentration was 46 ng/mL of melted surface snow.•The calculated deposition rate at the snow surface was 42 kg km−2 year−1.•Urban areas in western Europe are important sources of nanoplastics at this site.
Several viable but conflicting explanations have been proposed to explain the recent ~8 p.p.b. per year increase in atmospheric methane after 2006, equivalent to net emissions increase of ~25 Tg CH
...per year. A concurrent increase in atmospheric ethane implicates a fossil source; a concurrent decrease in the heavy isotope content of methane points toward a biogenic source, while other studies propose a decrease in the chemical sink (OH). Here we show that biomass burning emissions of methane decreased by 3.7 (±1.4) Tg CH
per year from the 2001-2007 to the 2008-2014 time periods using satellite measurements of CO and CH
, nearly twice the decrease expected from prior estimates. After updating both the total and isotopic budgets for atmospheric methane with these revised biomass burning emissions (and assuming no change to the chemical sink), we find that fossil fuels contribute between 12-19 Tg CH
per year to the recent atmospheric methane increase, thus reconciling the isotopic- and ethane-based results.
Abstract
It is now established that microplastics are a pervasive presence in aquatic and terrestrial ecosystems. The same is assumed to be true for nanoplastics but data are lacking due to technical ...difficulties associated with sample analysis. Here, we measured nanoplastics in waterbodies at two contrasting sites: remote Siberian Arctic tundra and a forest landscape in southern Sweden. Nanoplastics were detected in all sampled Swedish lakes (
n
= 7) and streams (
n
= 4) (mean concentration = 563
µ
g l
−1
) and four polymer types were identified (polyethylene, polyvinyl chloride (PVC), polypropylene, polyethylene terephthalate). In Siberia nanoplastics were detected in 7/12 sampled lakes, ponds and surface flooding, but only two polymer types were detected (PVC and polystyrene) and concentrations were lower (mean 51
µ
g l
−1
). Based on back-calculation of air mass trajectories and particle dispersion, we infer that nanoplastics arrive at both sites by aerial deposition from local and regional sources. Our results suggest that nanoplastics may be a near-ubiquitous presence even in remote ecosystems.
It has been established that various anthropogenic contaminants have already reached all the world's pristine locations, including the polar regions. While some of those contaminants, such as lead ...and soot, are decreasing in the environment, thanks to international regulations, other novel contaminants emerge. Plastic pollution has been shown as a durable novel pollutant, and, since recently, smaller and smaller plastics particles have been identified in various environments (air, water and soil). Considerable research already exists measuring the plastics in the 5 mm to micrometre size range (microplastics). However, far less is known about the plastics debris that fragmented to the sub-micrometre size (nanoplastics). As these small particles are light, it is expected that they have already reached the most remote places on Earth, e.g. transported across the globe by air movement. In this work, we used a novel method based on Thermal Desorption – Proton Transfer Reaction – Mass Spectrometry (TD-PTR-MS) to detect and measure nanoplastics of different types in the water sampled from a Greenland firn core (T2015-A5) and a sea ice core from Antarctica. We identify polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), and Tire wear nanoparticles in the 14 m deep Greenland firn core and PE, PP and PET in sea ice from Antarctica. Nanoplastics mass concentrations were on average 13.2 ng/mL for Greenland firn samples and 52.3 ng/mL for Antarctic sea ice. We further discuss the possible sources of nanoplastics that we found at these remote locations, which likely involve complex processes of plastic circulation (emission from both land and sea surface, atmospheric and marine circulation).
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•We detected nanoplastics in ice samples beyond the South and North polar circle.•The most prominent nanoplastics type was PE, with relative contribution of >50%.•In a 14 m firn core from Greenland, we detected on average 13.2 ng/mL nanoplastics.•In sea ice from Antarctica, we detected on average 52.3 ng/mL nanoplastics.•Tire wear nanoplastics are significant in the Northern but not in Southern polar site.
Sulfur hexafluoride (SF6) is a greenhouse gas with one of the highest radiative efficiencies in the atmosphere as well as an important indicator of transport time scales in the stratosphere. The ...current widely used estimate of the atmospheric lifetime of SF6 is 3200 years. In this study we use in situ measurements in the 2000 Arctic polar vortex that sampled air with up to 50% SF6 loss to calculate an SF6 lifetime. Comparison of these measurements with output from the Whole Atmosphere Community Climate Model (WACCM) shows that WACCM transport into the vortex is accurate and that an important SF6 loss mechanism, believed to be electron attachment, is missing in the model. Based on the measurements and estimates of the size of the vortex, we calculate an SF6 lifetime of 850 years with an uncertainty range of 580–1400 years. The amount of SF6 loss is shown to be consistent with that of HFC‐227ea, which has a lifetime of 670–780 years, adding independent support to our new SF6 lifetime estimate. Based on the revised lifetime the global warming potential of SF6 will decrease only slightly for short time horizons (<100 years) but will decrease substantially for time horizons longer than 2000 years. Also, the use of SF6 measurements as an indicator of transport time scales in the stratosphere clearly must account for potential influence from polar vortex air.
Key Points
Atmospheric lifetime of SF6 reduced by nearly a factor of 3 based on measurements in the stratospheric polar vortex
Consistency of SF6 and HFC‐227ea derived mean age of air gives independent confirmation of SF6 lifetime reduction
The signal of mesospheric loss or production of a trace gas is highly concentrated in the stratospheric polar vortices each winter
Plain Language Summary
We have calculated an atmospheric lifetime of the molecule SF6 based on trace gas measurements in the stratospheric polar vortex. This lifetime is 3 times shorter than the commonly used lifetime over the past 20 years. Since SF6 is a greenhouse gas this adjustment has implications for long‐term climate effects.
Methane is an important greenhouse gas and its atmospheric concentration has almost tripled since pre-industrial times. It plays a central role in atmospheric oxidation chemistry and affects ...stratospheric ozone and water vapour levels. Most of the methane from natural sources in Earth's atmosphere is thought to originate from biological processes in anoxic environments. Here we demonstrate using stable carbon isotopes that methane is readily formed in situ in terrestrial plants under oxic conditions by a hitherto unrecognized process. Significant methane emissions from both intact plants and detached leaves were observed during incubation experiments in the laboratory and in the field. If our measurements are typical for short-lived biomass and scaled on a global basis, we estimate a methane source strength of 62–236 Tg yr-1 for living plants and 1–7 Tg yr-1 for plant litter (1 Tg = 1012 g). We suggest that this newly identified source may have important implications for the global methane budget and may call for a reconsideration of the role of natural methane sources in past climate change.
Coastal environments are a major source of marine methane in the atmosphere. Eutrophication and deoxygenation have the potential to amplify the coastal methane emissions. Here, we investigate methane ...dynamics in the eutrophic Stockholm Archipelago. We cover a range of sites with contrasting water column redox conditions and rates of organic matter degradation, with the latter reflected by the depth of the sulfate–methane transition zone (SMTZ) in the sediment. We find the highest benthic release of methane (2.2–8.6 mmol m–2 d–1) at sites where the SMTZ is located close to the sediment–water interface (2–10 cm). A large proportion of methane is removed in the water column via aerobic or anaerobic microbial pathways. At many locations, water column methane is highly depleted in 13C, pointing toward substantial bubble dissolution. Calculated and measured rates of methane release to the atmosphere range from 0.03 to 0.4 mmol m–2 d–1 and from 0.1 to 1.7 mmol m–2 d–1, respectively, with the highest fluxes at locations with a shallow SMTZ and anoxic and sulfidic bottom waters. Taken together, our results show that sites suffering most from both eutrophication and deoxygenation are hotspots of coastal marine methane emissions.
Ocean plastic pollution is a problem of increasing magnitude; yet, the amount of plastic at the sea surface is much lower than expected. Solar ultraviolet (UV) radiation can induce photodegradation, ...but its importance in determining the longevity of floating plastic remains unconstrained. Here, we measured photodegradation rates of different plastic types slightly larger than microplastics (virgin polymers and floating plastic debris) under simulated marine conditions. UV irradiation caused all plastic types to leach dissolved organic carbon, and to a lesser degree carbon dioxide, carbon monoxide, methane, and other hydrocarbon gases. The release of photodegradation products translates to degradation rates of 1.7–2.3 % yr−1 of the tested plastic particles normalized to conditions as found in the subtropical surface ocean. Modelling the accumulation of floating plastic debris, our results show that solar UV radiation could already have degraded 7 to 22 % of all floating plastic that has ever been released to the sea.
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•Several plastic types were exposed to UV light under simulated marine conditions.•UV light induced photodegradation; degradation products were dominated by DOM.•Photodegradation of small plastic pieces was 1.7–2.3 % yr−1 under subtropical conditions.•7–22 % of all floating plastic released to the sea could be photodegraded already.•Photodegradation is a potential key sink for floating plastic.
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