Microplastic surface retention and mobility on hiking trails

Inter-annual variation in the microplastics abundance in feces of the Baird's tapir (Tapirus bairdii) from the Selva Maya, México

Microplastics (MPs) are found in a wide range of ecosystems, from the Arctic to the deep ocean. However, there is no data on their presence in terrestrial mammals that inhabit the Selva Maya. The aim of this study is to detect the presence of MPs in the feces of the Baird's tapir (Tapirus bairdii) from the region of Calakmul, located in the Yucatan Peninsula, Mexico. We analyzed 129 fecal samples collected during 2017 and 2018, obtaining 57 and 72 samples during the rainy and dry seasons respectively. Sixty-eight percent of the samples contained 743 MPs with a mean of 19.3 ± 28.1 MPs/kg of dry weight (DW) feces in both years. An inter-annual variation in the average abundance of microplastic was observed during the two-year period (2017-2018), with a 72 % increase in these plastic particles in feces. Fourteen polymers were identified, with ethylene vinyl acetate (EVA), polypropylene (PP) and polyester (PES) being the most abundant during both years. Although the effects of MPs on the health of tapirs are not known, their presence is cause for concern. There is an urgent need for the implementation of appropriate plastic waste management programs in communities of the Selva Maya to diminish the consumption of MPs in species including humans where they pose a significant risk to health. ENVIRONMENTAL IMPLICATIONS: The use of plastics worldwide is increasing every day, so the presence of microplastics is and will continue to be a major environmental problem. It is known that contaminants can adhere to plastics, making them hazardous materials. Microplastics can contaminate remote areas such as Biosphere Reserves. Terrestrial species such as the tapir can ingest microplastics, putting their health at risk. Knowing the dispersion of microplastics is very important in order to manage them properly, taking into account their emission sources and type of polymer.

Microplastics in vineyard soils: First insights from plastic-intensive viticulture systems

In the terrestrial environment, microplastics in specialty cropping systems have not been studied so far. Viticulture as a potential plastic-intensive management form and a land use with high erosion risks, plays an important role in transport and distribution of material to other terrestrial and aquatic systems. This paper is a first investigation of microplastics in vineyard soils, assessing the spatial distribution and composition of microplastics in organically and conventionally managed viticulture, and relates it to the macroplastic collected at the vineyards. Topsoils (0-10, 10-30 cm) and plastic particles on soil surfaces from eight vineyard lots were sampled. Four of the vineyards were under organic and four underconventional management and they were all located in the Moselle and Saar Wine Region (Rhineland-Palatinate, Germany). Microplastic analysis was performed via μFTIR chemical imaging after wet-chemical microplastic extraction from soil samples. The mean microplastic concentration was 4200 ± 2800 p kg-1 (mean ± SD), with detected mean sizes of 230 μm ± 300 μm. Most abundant polymers were PP (35.2 %), PA (25.3 %) and PE (15.5 %). The distribution pattern showed higher microplastic concentration in topsoil, at middle and bottom slope position. The smallest particle sizes were found in subsoil samples and bottom position. Thus, erosion is assumed to be a potential downhill transport pathway. According to our dataset, management seems to have no significant influence on microplastic abundance, but affects polymer composition. Polymer composition of micro- and macroplastics partly coincide, thus in-situ fragmentation, is considered the major input source. Based on our findings, we recommend further investigation of plastic pathways in speciality crop systems like viticulture.

Tracking anthropogenic microparticles in wildlife of an alpine insular environment

Despite the isolation of remote natural regions, it has been discovered that they are experiencing the accumulation of anthropogenic microparticles (i.e., microplastics or natural or semisynthetic cellulosic particles). Teide National Park (Canary Islands, Spain) is a high-mountain protected area known for its rich biodiversity. This study aims to assess the occurrence of coloured anthropogenic particles in the faecal matter of wild mammals, specifically rabbits and mouflons, residing in the park. With this purpose, faeces were collected from 68 systematically distributed sampling points. A stereomicroscopy-guided grinding process allowed a chemical-free and quick visual inspection of 616 individual excreta, revealing that 96% were particle-free. However, 37 anthropogenic particles were found, which correspond to 0.79 ± 0.20 items per gram of dry faecal matter. The archetypical particle was a cellulosic blue microfibre of 2721 ± 407 µm, though poly(ethylene-vinyl acetate) and polypropylene were also identified via micro Fourier-transform infrared spectroscopic analysis. Atmospheric deposition and touristic pressure may be the sources of the anthropogenic particles, as they were randomly found in 36% of the sampling points. These findings represent the first evidence of anthropogenic particle ingestion by wild rabbits and mouflons, signifying the introduction of microplastics into terrestrial food chains in a remote high-mountain environment.

Weathering alters the profile of trace metals and organic compounds in leachates and bioavailability extracts from microplastics of trail running shoes

Microplastics (MPs) from rubber outsoles of trail running shoes may contribute significantly to contamination in protected areas. In the natural environment, weathering processes can damage MP molecular structure and alter the mobility of inorganic and organic compounds used as additives in rubber. In this study, we characterised changes in the surface morphology, functional groups, and thermal stability of MPs weathered on and below the soil surface over 12 weeks, and analysed inorganic and organic additives in leachates (0.01M CaCl2) and bioaccessibility extracts (ethyl acetate). Weathering conditions included UVC irradiation at 25 °C and 80% soil moisture. Microplastics on the soil surface exhibited cracking, fragmentation, and increased extractability of zinc, sulphur, titanium and fatty acids. Microplastics below the soil surface were not significantly physically or chemically altered, however zinc leachability increased following extended weathering by up to 155%. Bioaccessibility of thiol, aromatic and cyclic organic additives decreased from both surface and sub-surface MPs over the 12 week weathering period, but there was evidence of an increase in transformation by-products. Microplastic toxicity may be significantly altered by environmental conditions and MP weathering. It is critical ecotoxicological studies use weathered MPs to assess impacts on rare and endemic species found in protected spaces.

Microplastic pollution on hiking and running trails in Australian protected environments

Microplastics (MPs) are ubiquitous worldwide, present even in remote areas of the natural environment. Hiking and trail running are a source of MPs on recreational trails in protected environments, which are characterised by high biodiversity and natural, ecological or cultural significance. Our understanding of the risks of microplastic pollution is impeded however by a lack of information on MPs present in the soil environment in such areas. This study characterised the quantity and physicochemical characteristics of MPs in two conservation areas in south-eastern Australia: 1) the adjacent Duval Nature Reserve and Dumaresq Dam Reserve, and 2) the Washpool and Gibraltar Range National Parks. We measured atmospheric deposition over a six-month period in the Reserves, and baseline amounts of MPs on recreational trails in the Reserves and National Parks. Atmospheric deposition averaged 17.4 MPs m^-2 day^-1 and was dominated by fibres, comprising 84 % of MPs. Microplastics detected on trail surfaces ranged from 162.5 ± 41.6 MPs/linear metre to 168.7 ± 18.5 MPs/linear metre and exhibited a very wide range of physical and chemical characteristics. The majority of MPs on the trail surfaces comprised polyurethane, polyethylene terephthalate and polystyrene, and 47-71 % were fibres. Microplastics were attributed to clothing, footwear, litter, and diffuse sources. Minimising and preventing MP pollution, however, is complex given there are multiple direct and diffuse sources, and several factors influencing increased MP deposition and retention in the environment.