We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Baseline levels of microplastics in agricultural soils obscure the effects of additional microplastics from recycled fertilizers
AI summary Read the abstract
Researchers investigated whether liquid or solid digestate fertilizer from a Swiss biogas plant adds detectable microplastic loads to agricultural soils above natural background levels. Despite finding microplastics in digestate, treated soil concentrations were not significantly different from the unfertilized control, suggesting high baseline soil microplastic levels obscure the signal from digestate inputs.
Digestate from the recycling of various organic wastes in biogas plants is widely used as organic fertilizer for agricultural soils. Organic fertilizers contribute to microplastic loads, but it is not well constrained how they contribute to the overall accumulation of microplastic in agricultural soils. We investigated a field experiment in Switzerland fertilized since 2018 with liquid or solid digestate from a non-agricultural biogas plant. Microplastic particle concentrations (p) and characteristics were investigated in digestate fertilizers, digestate-treated soils and a control soil that did not receive organic fertilizers. Microplastics were extracted from the soil (two rounds of density separation (1.5 g cm− 3) and Fenton treatment), followed by µFTIR chemical imaging analysis with a size detection limit of 20 μm. We found median microplastic concentrations of 16,000 p kg− 1 (10,600–54,000 p kg− 1) in digestate fertilizers, 6,400 p kg− 1 (800–33,800 p kg− 1) in digestate-treated soils and 7,100 p kg− 1 in the control soil caused by a single outlier value or 5,600 p kg− 1 when excluding the outlier. Particle sizes and polymer compositions differed between digestate fertilizers and soils. Topsoil (0–20 cm) microplastic stocks varied from 1.8 to 3.8 × 106 p m− 3. The calculated inputs from the digestate application contributed only 0.9–4.0% to the total microplastic stocks which led to the case that digestate microplastic inputs were not detectable against the variation of the stocks. The study highlights those substantial high concentrations of microplastic might already occur in many soils, due to previous microplastic inputs over several decades from e.g., recycled fertilizer application like sewage sludge or from other diffuse sources. Whilst it was observed from the fluxes that digestate can be a substantial source of microplastics to soils, the comparatively short time of application and the high background at our investigated sites leads to a obscured effect where digestate inputs serve a limited function.
More Papers Like This
An Overlooked Entry Pathway of Microplastics into Agricultural Soils from Application of Sludge-Based Fertilizers
AI summary Read the abstract
Researchers analyzed sludge-based fertilizers applied to agricultural soils and found high microplastic concentrations (hundreds to thousands per kilogram of dry weight) that were transferred to soils after application, identifying this as an important but overlooked pathway for terrestrial microplastic contamination.
Quantification and identification of microplastics in organic fertilizers: the implication for the manufacture and safe application
AI summary Read the abstract
Researchers measured microplastic contamination in 23 commercial organic fertilizers, finding widespread presence at levels that could meaningfully contribute to agricultural soil pollution when fertilizers are applied. The results raise concerns about organic fertilizers as an underappreciated pathway for microplastics entering farm soils and the food system.
Microplastics in liquid biofertilizers: An overlooked threat to agricultural soil?
AI summary Read the abstract
Researchers quantified microplastic concentrations in liquid biofertilizers and estimated their contribution to agricultural soil loading, finding that fragment-dominated particles in the 5–50 μm range represent a measurable but minor input compared with sewage sludge, though repeated long-term application could cause gradual accumulation.
Biosolid amendments as drivers for microplastic pollution in soil: Measurements and insight from multiple analytical methods in an agricultural field study
AI summary Read the abstract
Farms often spread "biosolids" (treated sewage sludge and animal waste) on fields as fertilizer, but this study shows that practice can also introduce microplastic pollution into agricultural soil, with fields that received sludge showing different plastic contamination than untreated fields. Since crops grow in this soil and microplastics can potentially work their way into our food and water, this raises questions about how common farming practices might be a hidden source of plastic exposure in our diets.
Microplastic contamination of organic fertilisers applied to agricultural soils
AI summary Read the abstract
This study examined microplastic contamination in organic fertilizers applied to agricultural soils, finding plastic particles in multiple fertilizer types. Organic fertilizers derived from sewage sludge or compost can introduce microplastics into farmland, potentially contaminating crops and groundwater.
Research digests by email
When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.