Microplastic contamination in soil environment – a review

Plastic is an indispensable material essential for modern human life. With highly increasing demand for plastic use, however, environmental contamination by plastic litters has become an emerging issue. Globally, large quantity of used plastics is landfilled or emitted directly to the aquatic and terrestrial environments, albeit a part of the plastics is recycled or incinerated as energy source. In particular, microplastic debris that are smaller than 5 mm are considered to be emerging contaminants of global concern. In the past decade, however, most of the researches on impacts of microplastic contamination have been focused on the marine ecosystem, whereas very limited ones on the terrestrial ecosystem. Soil can be considered as a major sink and a carrier of microplastic contaminants to the aquatic environment. Most sources of microplastics in the soil environment are entered via a variety of routes and subsequent fragmented and spread to the surrounding environments, vertically and horizontally. In addition, there are negative impacts on soil biota, which in turn would cause concerns of human health by affecting the food web. Here, we provide an overview of characteristics, research trend, analytical methods, migration and degradation processes, effects on soil biogeochemistry, and interaction with soil organisms of microplastics suggesting the importance of ongoing research impacts of microplastics on the terrestrial ecosystem.