Plastics in soil environments: All things considered

The increasing production and use of conventional plastics, including in agricultural systems, has generated over 6500 million tonnes of plastic waste over the last 70 years. Over two–third of this waste had been deposited in landfills and natural environments including soils. However, the existence, persistence and impacts of plastics on soil properties and soil ecosystem services have received little attention compared to aquatic environments. Some agricultural soils accumulate plastics in large concentration from the application of sewage sludge and composts, wastewater for irrigation and the use of plastic films. The review provides an overview of the procedures used for the separation and characterization of plastics in soils. Based on the limited data, we have found that contaminated soils accumulate substantial amounts of plastics worldwide with a mean of 6153 particles kg − 1 soil (median 1083 = particles kg − 1 ). The presence of plastics can cause a series of toxic effects to soil health, fauna and plants through complex interactions. The results from existing literature have been reviewed and summarized. Once plastics enter the soil, they can simultaneously go through photo–, thermal– and bio– degradation. However, the degradation of conventional plastics is very slow, with half–lives ranging from a few hundreds to thousands of years in soil environments. Based on our review findings we recommend a number of priority research areas.