Synthetic fibers in atmospheric fallout: A source of microplastics in the environment?

Highlights

• Atmospheric fallout of fibers is higher at a more urbanized site.

• 29% of the fibers in atmospheric fallout contain petrochemicals.

• Atmospheric fallout appears to be an important source of microplastics.

Abstract

Sources, pathways and reservoirs of microplastics, plastic particles smaller than 5 mm, remain poorly documented in an urban context. While some studies pointed out wastewater treatment plants as a potential pathway of microplastics, none have focused on the atmospheric compartment. In this work, the atmospheric fallout of microplastics was investigated in two different urban and sub-urban sites. Microplastics were collected continuously with a stainless steel funnel. Samples were then filtered and observed with a stereomicroscope. Fibers accounted for almost all the microplastics collected. An atmospheric fallout between 2 and 355 particles/m²/day was highlighted. Registered fluxes were systematically higher at the urban than at the sub-urban site. Chemical characterization allowed to estimate at 29% the proportion of these fibers being all synthetic (made with petrochemicals), or a mixture of natural and synthetic material. Extrapolation using weight and volume estimates of the collected fibers, allowed a rough estimation showing that between 3 and 10 tons of fibers are deposited by atmospheric fallout at the scale of the Parisian agglomeration every year (2500 km²). These results could serve the scientific community working on the different sources of microplastic in both continental and marine environments.

Introduction

Microplastics are a widespread particular contaminant originating from the breakdown of larger plastic debris (secondary) or directly manufactured on a millimetric or submilletric size (primary) (Cole et al., 2011). These plastics have been defined as particles with the largest dimension smaller than 5 mm (Arthur et al., 2008); they cover a continuous spectrum of sizes and shapes including 1D-fibers, 2D-fragments and 3D-spheres.

Given their size, these microparticles can be ingested by a wide range of species, either in marine (Anastasopoulou et al., 2013, Lusher et al., 2013, Thompson et al., 2004) or freshwater environments (Sanchez et al., 2014). These microplastics have negative effects on organisms and the possibility of their translocation, bioaccumulation and trophic accumulation is currently being debated (Wright et al., 2013).

While marine plastic pollution has been well documented, there has been limited focus on the continental contamination (Dris et al., 2015b, Wagner et al., 2014). Moreover, its sources, pathways and reservoirs in urban environments remain largely unknown. It is crucial to gather a better knowledge about these particles in the continental environment as rivers are said to be the main source of marine microplastics (Andrady, 2011). If it is very often cited that 80% of the fibers in the marine environment come from the continent, this estimation is not well documented and demonstrated.

Synthetic fibers are one of the forms in which microplastics can be found. They derive presumably from synthetic clothing or macroplastics. Different pathways are thought to be an important source of fibrous microplastics in the aquatic environment. It has been shown that laundry washing machines discharge large amounts of microplastics into wastewaters (reaching 1900 fibers in one wash (Browne et al., 2011)). During wastewater treatment, synthetic fibers are known to contaminate sewage sludge (Habib et al., 1998, Zubris and Richards, 2005). The sources and fate of microplastics in the various compartments of the urban environment are poorly documented (Dris et al., 2015a); this paper focuses on the atmospheric compartment and investigates the contribution of the atmospheric fallout as a potential vector of plastic pollution.