Project
Detection, Fate and Effects of Fertilizer Coating Microplastic in Soils
Polymer coated fertiliser (PCF) is used globally as an efficient form of inorganic fertilisers in agriculture. It offers convenience and potentially reduces N emission to the environment. However, PCF prills enter soil readily as microplastic (MP) (diameter < 5 mm) and are virtually impossible to remove from soil. Thus, to understand and evaluate the risk of PCF-derived MP to agriculture soils, we develop methods to detect PCF, as well as their fate and effect to soil physical, chemical and biological parameters.
Background
Microplastics (MP) is an emerging category pollutants that has gained attention in environmental sciences due to its widespread occurrence in the environment, its persistence and toxicity. MP are plastic particle <5 mm.
Soil is recognised as a major sink of MP. Reviews and studies usually focus on more common agricultural MP sources such as mulch film, biosolids and atmospheric deposition. MP intentionally added to soil in the form of polymer coated fertilisers (PCF) were often neglected despite its extensive use and relatively long history of application in agriculture and forestry since the 1960s.
PCFs are produced as prills (Ø = 2-5 mm) consisting of a fertiliser core surrounded by a very thin layer of plastic coating. Due to the plastic coating, nutrients from the fertiliser core are released into the soil gradually in a controlled rate that match plant and crops’ need. Compared to conventional fertiliser, PCF minimises nitrogen and other nutrients losses, reduce management effort, labour cost as well as decreasing leaching into the waterway that may cause harmful effects.
Description
Compared to mulch film debris, MP from PCF is already smaller in size and impossible to be removed from soil. Additives added during polymer production might be leached into soil and the groundwater. Unlike mulch film, PCF is mixed into soil and undergo minimal UV degradation (if any) and thus, making it more difficult to degrade. Therefore, impacts of MP from PCF accumulating in soil might be more significant than previously perceived.
Recently, with the proposal of restriction on intentionally added MP in products (including particle < 5 mm and fiber < 15 mm) from European Chemical Agency (ECHA) gained favour from Member States, PCF gained more attention as a significant MP contributor in soil. Furthermore, the USA and China as the largest producers and consumers of PCF have limited policy regulating and monitoring the impact of PCF to the environment. With the majority of research on PCF recently focusing on its nutrient/fertilizer content and efficiency, the fate and effect of MP derived from PCF leave a knowledge gap. Our project aims to address this knowledge gap by developing a holistic approach to assess the impact of intentionally added MP in soil, with the preliminary investigation focus on PCF-derived MP.
Overall aim of the project
Develop suitable extraction method(s) for microplastics (MP) from polymer coated fertilisers (PCF) in soil assess the distribution and fate of PCF-derived MP in agricultural soil examine the impacts of PCF-derived MP to soil health and biota with laboratory, mesocosm experiments and long-term field trials.