Methods of microplastic separation from soil and soil arthropods: a systematic review

Microplastics – small plastic particles ≤ 5 mm – have quietly invaded soils, threatening the delicate balance of ecosystems and soil organisms. This review dives into the toolbox scientists use to detect and extract these hidden pollutants from soil and soil-dwelling organisms. We explore methods such as floating plastics in salty solutions, breaking down organic matter with hydrogen peroxide or enzymes, and using high-tech imaging like infrared spectroscopy. While some techniques, like sodium iodide separation, recover over 95% of microplastics, their high cost and complexity remain hurdles. Gentler approaches, such as enzyme-based digestion, protect fragile organisms but take longer. Despite advances, the field struggles with inconsistent methods and the near-invisible challenge of nanoplastics. Innovations like atomic force microscopy hint at future breakthroughs, but unifying global standards and blending old and new techniques will be key to turning the tide. This work calls for teamwork across disciplines to sharpen our tools, safeguard soils, and stem the silent spread of microplastic pollution.