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Tier 2
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Original research — experimental, observational, or case-control study. Direct primary evidence.
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Microplastic abundance in sludge-treated fields: Variance and estimated half-life
The Science of The Total Environment2024
15 citations
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Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Score: 50
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0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.
Researchers measured microplastic levels in agricultural fields that had been heavily treated with sewage sludge, finding concentrations ranging from roughly 2,400 to 49,000 particles per kilogram of soil, with polyester and acrylic accounting for more than half of all particles. The study estimated that once sludge application stops, the number of microplastic particles in soil decreases with a half-life of about 2.5 years, suggesting smaller particles break down or migrate away faster than larger ones.
This study investigated the abundance of microplastic (MP) in agricultural soil fertilised with sludge, assessing the variation in MP count and estimated mass in three long-term field trials treated excessively with sludge in 2003-2012. Ten samples were taken from each of the three fields with concentrations ranging from 2392 to 48,791 counts kg<sup>-1</sup>, where over 50 % of the MPs were polyester and acrylic. Due to the considerable variation in concentration, the impact of the number of sub-samples on the predicted measured concentration was estimated applying a Monto Carlo simulation approach. Choosing the number of sampling points is a compromise between acceptable sampling error and available resources. The simulations showed an increasingly high risk of obtaining an outlier when taking less than approx. ten subsamples. When ending fertilisation with sludge, the estimated half-life for the MPs measured by counts was approx. 2.5 years, whereas the half-life for the MP estimated mass was approx. 4 years. Hence, smaller particles seemed to degrade and/or migrate elsewhere the fastest.