Soil provides 98.8% of our food, making healthy soils vital for our food security. By 2050, we need to increase food production by 70% to meet the needs of a growing population. However, our soils have been under pressure and are degrading. One vital service soil provides is the contaminant sink and filtration to protect groundwater. However, this means that soil stores and potentially accumulates pollutants including microplastics.
The potential accumulation of microplastic in agricultural soil has recently raised concerns because of the increasing intentional use of plastics and unintentional entry of microplastics into soil due to farming practises. Practices like plastic mulching, where soil is covered with plastic to retain moisture and control weeds and the accidental introduction of plastics through biosolid applications, where composted biosolids are used as fertilizer, are contributing to microplastic entry into soil. Once the microplastic has been introduced into the soil they do not break down easily and can stay in the soil for many years. Based on this persistence, widespread use of plastic and recent results in soil eco toxicology and eco system effects, plastic has been proposed as driver of global change. However, even basic information such as plastic mass concentrations or its fate and impact on soil health are widely unknown.
Therefore, this project aimed to assess the significance of micro/plastic pollution in agricultural soil to understand its relevance to impact soil health through addressing the following specific objectives: (1) Quantify soil profile mass concentrations of plastic for their polymer type; (2) Develop/modify and validate a comprehensive analytical workflow additive fingerprinting/screening und potential identification employing LC and GC UHRMS systems; (3) Determine additive partitioning and leaching behaviour at different stages of polymer aging; (4) Quantification of plastic impact on vital soil processes.
Based on the findings of this project, it is evident that microplastics persist in the topsoil of all examined agricultural soils. However, the concentrations of microplastics detected were lower than anticipated, underscoring the importance of incorporating soil management practices into research methodologies and result interpretations. Further this highlights the need for standardized protocols to ensure comparability of results across studies.
These findings further highlight the impact of “best practice” and legislation covering soil management practices, such as fertilizer application control and quality control of organic fertilizers in protecting soil health and minimize microplastic contamination.
