A Simplified and Optimised Protocol for Microplastics Determination in Soil and Sludge Applied Soils

Abstract Microplastics are emerging contaminants of concern often associated with high concentrations in waste streams. An enormous quantity of dry sludge is generated globally and is often used as a soil amendment in agricultural areas in both the developed and developing countries. The concentration of microplastics (MPs) in sewage sludge varies globally in a wide range between 1 and 186.7 ± 26.0 MP g −1 . The methodologies used for MP determination in sludge and soils vary, making any realistic comparison infructuous. The International Atomic Energy Agency (IAEA) took the initiative to develop a simple and optimised method under its Coordinated Research Project (CRP; D15021) to determine MPs in agricultural soils and intends to evaluate the fate and environmental impact of plastics in soil and crops. The methodology for MP determination in agricultural soils and sludge-applied soils is presented. Details are given on sample collection and the need for composite samples for non-homogeneous matrices like soil, sample processing including a preferred method for oxidation of organic matter, density separation fluids and multi-tier sample identification techniques. Adaptation of the method will not only lead to the generation of comparable data for the CRP participants. It will also assist the 178 IAEA member states across the regions in generating analogous datasets on microplastics (MPs) in soil and sludge-applied soils. The data and information generated on MP inventories can be used to underpin the policy on safe sludge usage in agricultural soils.