Microplastics released from artificial turf applied as hedge walls: Their aging-induced properties and uptake by grass carp, mussels and earthworms

Abstract

An emerging source of MPs in China is artificial turf applied as hedge walls (ATHWs), which have been increasingly used mainly in enclosing construction sites as well as beautifying the municipal landscape. However, the specific ecological risks caused by MPs released from ATHWs (ATHW-MPs) are still unknown. In the present study, we investigated the amount and aging-induced properties of green fibers (GMPs) and the backing materials (BMPs), released from the ATHWs; as well as their potential uptake by animals. Grass carp (Ctenopharyngodon idellus), mussels (Mytilus edulis) and earthworms (Eisenia fetida) were used as animal test species. Outdoor exposure for 180 days made ATHWs more prone to embrittlement and disintegration, leading to 4.58 ± 1.96 % weight loss of the grass panels. More and finer particles and fibers were released by an external shear force from the outdoor exposed panels than from panels exposed to artificial UV-light. The aging process altered the surface properties of both GMP and BMP such as zeta potential, surface roughness, specific surface area and chemical groups, which may change their interaction with chemicals and species in the environment. All the studied species tended to ingest more fine particles (<40 µm) of BMPs. As a kind of microfibers, GMP were ingested by some grass carp and mussels but not by earthworms. Ingestion of MPs increased at higher MP-exposure concentrations. Although most of BMPs were partly egested by animal species after 3 d intestinal cleansing; 10 %, 44 % and 22 % of ingested BMPs remained in grass carp, mussels and earthworms, respectively. Aging of ATHW cause more and finer shed MPs, therefore, the sources and quality of the raw materials and producing process must be strictly controlled. We suggest that industry should develop or pay attention to the materials that are more resistant to aging; assess and inform the life cycle of the ATHWs in the instructions, and remind users to avoid free exposure of the backing material during installation.