A novel multi-criteria decision analysis approach to advance standardisation of microplastic extraction from agricultural soils

Microplastic (MP) pollution in agriculture is a growing concern, yet a lack of standardised analytical approaches limits the reliable assessment of MP pollution in soil. In this study, the extraction of six representative MP polymer types from three agricultural soils with a range of texture and organic matter was optimised by applying a novel multicriteria decision framework that integrated recovery efficiency, spectral integrity using Fourier Transform Infrared Spectroscopy (FT-IR), extraction time, extraction reagent costs, and environmental impact. Different combinations and sequences of density separation reagents (sodium iodide, sodium bromide, and zinc chloride) and organic matter digestion (with Fenton’s reagent or 30% H 2 O 2 ) were assessed at two temperatures (50°C and 60°C). Based on the decision framework, the combination of 30% H 2 O 2 at 50°C and zinc chloride (1.6 g/cm 3 ) was identified as the most effective method. Mean recovery of total MPs in all three soils was above 92%. The recovery of low-density polyethylene (LDPE) was lowest recovery for individual polymers at 73%. The MP spectral integrity remained high and the method was quick, low cost, and low environmental impact. The decision framework clearly demonstrated that this method provided the most reliable and effective approach for MP extraction from diverse agricultural soils. The framework provides a new robust and transparent model to support and accelerate global efforts toward methodological standardisation. • Microplastic extraction was optimised for soils using a multi-criteria decision framework • Digestion with 30% H 2 O 2 at 50°C, density separation with ZnCl 2 was most effective • Mean total MP recovery >92%; LDPE recovery was 73% • The method was effective, quick, cheap and had a low environmental impact