Qian Zhou, Haibo Zhang, Chuancheng Fu, Yang Zhou, Zhenfei Dai, Yuan Li, Chen Tu, Yongming Luo,
The distribution and morphology of microplastics in coastal soils adjacent to the Bohai Sea and the Yellow Sea,
Microplastics (<5 mm) are considered to be emerging pollutants
of global concern. Investigations on microplastics pollution in coastal
and marine environments have increased recently but knowledge gaps still
exist regarding microplastics in coastal beach soils with high-intensity
human activities. In the present study a total of 120 soil samples were
taken from 53 sites along >3000 km of coastline in Shandong province,
east China, adjacent to both the Bohai Sea and the Yellow Sea coastlines
under different land use management. Microplastics were separated from
the soil samples using a continuous flow and floating separation
apparatus. The shape type, size, abundance, spatial distribution,
polymer composition and surface morphology of the microplastics were
identified by a range of advanced microscopic and micro-analytical
methods. The analytical results show that seven shape types, namely
foams, pellets, fragments, flakes, fibers, films and sponges, were
present in the beach soils. The polymer composition of the microplastics
included polyethylene, polypropylene, polystyrene, polyether urethane
and a polymer blend of both polyethylene and polypropylene.
Approximately 60% of the observed microplastics had a size range < 1 mm.
Microplastic abundance varied greatly among the soils, ranging from 1.3
to 14,712.5 N kg−1 (dry weight) as influenced by high-intensity human
activities such as mariculture, tourism, and port construction. The
seven shape types of microplastics from the coastal environment had
different weathering surface morphologies, showing scratches, creases,
micropores, cracks, either concave or convex, and of various shapes and
sizes, possibly due to physical friction, photochemical oxidation and/or
animal attack. Algae or crude oil was observed on the surface of some
microplastics. The weathered surfaces of microplastics might act as a
high-capacity carrier with adhering microorganisms and chemicals.
Further studies are required on the weathering processes, sorption
capacity and transport of microplastics especially in smaller size
(<1 mm) under coastal conditions.