Method for extraction of nanoscale plastic debris from soil

Sample preparation for extraction of nanoscale plastic debris (NPD, size < 1 μm) from environmental samples is a critical step to prepare NPD for further identification and quantification. Developing a NPD extraction method from soil matrices is particularly challenging due to the complexity of solid matrices. In the present study, we built upon the lessons learned from method development for extraction of microplastics and nanomaterials from environmental samples to develop a sample preparation method for extraction of NPD from soil matrices. The evaluation criteria for the extraction method are size distribution, particle number recovery, and particle mass recovery. Since there is no validated method available to trace and quantify the mass of NPD in complex matrices, we applied polystyrene particles doped with europium (Eu-PS NPs). Standard LUFA soil and field soil were spiked and mixed for 24 h with 1 mg of Eu-PS NPs and the particles were extracted from the matrices of the soils. The extraction method did not significantly influence the size distribution of the particles and the extraction agents did not degrade the Eu-PS NPs. Mass balance calculation suggested recoveries of 82 and 77% of the added Eu-PS NPs in LUFA soil and field soil, respectively. The number recoveries of the particles were 81 and 85% for LUFA soil and field soil, respectively. This method can be further optimized and used as the first building block to develop a generic sample preparation method for the extraction of NPD from soil samples. By combining this developed and verified extraction method with identification and quantification techniques, a fit-for-purpose workflow can be developed to quantify and subsequently understand the fate of NPD in soil.