First evidence of microplastic contamination in the supraglacial debris of an alpine glacier

Highlights

• We report the first evidence of microplastic contamination on an alpine glacier.

• Mean amount of 74.4 ± 28.3 (SE) items kg⁻¹ of sediment was found.

• Microplastic contamination was in the same range of marine and coastal sediments.

• We estimated 131–162 million plastic items on the glacier ablation area.

Abstract

Contamination by plastic debris has been documented in most regions of the world, but their occurrence in high mountain areas has not been investigated to date. Here we present the first report of the occurrence and amount of microplastic in any terrestrial glacier environment. In the supraglacial debris of the Forni Glacier (Italian Alps), we observed the occurrence of (mean ± standard error) 74.4 ± 28.3 items kg⁻¹ of sediment (dry weight). This amount is within the range of variability of microplastic contamination observed in marine and coastal sediments in Europe. Most plastic items were made by polyesters, followed by polyamide, polyethylene and polypropylene. We estimated that the whole ablation area of Forni Glacier should host 131–162 million plastic items. Microplastic can be released directly into high elevation areas by human activities in the mountain or be transported by wind to high altitude. The occurrence of microplastic on Forni Glacier may be due to the gathering of debris coming from the large accumulation area into the relatively smaller ablation area of the glacier, as a consequence of its flow and melting.

Introduction

Accumulation of plastic polymer (hereafter plastic) items is one of the most ubiquitous and long-lasting changes to the earth surface that human activities have produced since mass production of plastic commenced in the 1950s (Barnes et al., 2009; Thompson et al., 2004). Concerns have been raised in recent years on the potential impacts of plastic on ecosystems. Plastic is persistent, it can easily accumulate in the environment and enter the trophic chain, and its impacts on ecosystems have already been demonstrated (Barnes et al., 2009; Cole et al., 2011; Wright et al., 2013). In recent years, particular attention has been focused on microplastics, plastic items smaller than 5 mm. They can be specifically produced to be used in diverse personal care products and in different industrial applications (i.e., primary microplastics), or can be generated by the break-down of macroplastics (secondary microplastics) (Eerkes-Medrano et al., 2015). Surveys on marine and freshwater ecosystems have been established to monitor the temporal trends in the amount of plastic items. Oceanic campaigns have estimated the amount of macro- and microplastics afloat in the sea, and the amount transported to sea by rivers from terrestrial ecosystems (Eriksen et al., 2014). Moreover, recent studies have demonstrated that microplastics can be transported to virtually any part of the globe, also in the so-called remote areas. Indeed, plastic fragments have been found in deep sea, Southern Oceans, Arctic and Antarctica (Hamid et al., 2018), as well as in sub-alpine lake sediments (Imhof et al., 2013), in pelagic water and shoreline debris from high-mountain lakes (Free et al., 2014; Zhang et al., 2016), and floodplain soils in Alpine valleys (Scheurer and Bigalke, 2018). In addition, recent evidence of atmospheric microplastic deposition in a remote, pristine mountain area of the French Pyrenees suggests that microplastics can reach and affect remote, sparsely inhabited areas far from emission sources through atmospheric transport (Allen et al., 2019). However, to the best of our knowledge, no published study has documented the occurrence and the amount of plastic items on glaciers so far.

Glaciers are accumulation sites for aerially transported debris and pollutants as glacier ice forms through the transformation of accumulated snowfalls, which are particularly efficient in scavenging contaminants, including small debris, from the atmosphere (e.g. Lei and Wania, 2004; Lovett and Kinsman, 1990). Temperate glaciers then flow down valley, and the ablation area of valley glaciers thus concentrates the debris and the contaminants collected over the much vaster accumulation area of the glacier (Nakawo et al., 1986). For this reason, supraglacial debris is particularly rich in air-transported pollutants (Cook et al., 2016; Pittino et al., 2018), including radionuclides (Baccolo et al., 2017; Łokas et al., 2016). We thus hypothesized that similar processes may act also for microplastics, and we present here the first evidence of the occurrence and the first estimate of the amount of microplastic in the supraglacial debris of a large valley glacier in the Italian Alps.