Fertilisers are a major source of microplastic pollution in agricultural soil, a long-running experiment in the UK has shown, and this pollution has increased dramatically in the past 50 years.
at Lancaster University, UK, and his colleagues looked at soil samples collected and archived at Rothamsted Research in an experiment that has been running since 1843. The samples came from three groups: one containing soil that had received no fertiliser, one containing soil treated with organic fertilisers such as manure or organic compost, and one containing soil that had been treated with conventional fertilisers.
In samples collected before 1966, the researchers found little or no trace of microplastics. In the samples from the past 50 years, there was a significant increase in microplastic concentrations in all three groups, meaning that even soils that hadn鈥檛 been treated with fertiliser were contaminated. However, soils treated with either organic or inorganic fertilisers contained more microplastics, showing that fertilisers are a major contributor to soil contamination.
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鈥淭he issue with microplastics is that they鈥檙e capable of being transported across the world into different environmental media,鈥� says Cusworth. 鈥淔or example, with organic fertilisers, if any of the feed that鈥檚 been given to the farmyard animals contains any plastic, this will be digested and end up in faeces.鈥�
Inorganic fertilisers can spread microplastics because many of them are coated with polymers to ensure that nutrients are slowly released into the soil, he adds.
found that large amounts of microplastic are filtered out of wastewater and concentrated in sewage sludge that is sold as agricultural fertiliser. It estimated that between 31,000 and 42,000 tonnes of microplastic could be applied on agricultural soils in Europe each year.
Other research has shown that microplastics can alter the physical, chemical and microbiological properties of soil, affecting its fertility and ultimately crop production. In particular, the roots of lettuce and wheat crops can absorb microplastics from the surrounding soil and water. These can then be transferred from the roots to the edible parts of the plant.
鈥淚t鈥檚 been known for several years now that agricultural fields are sinks for plastic,鈥� says at the Free University of Berlin, Germany. He adds that documenting patterns of microplastic accumulation in soils over time is an important step in better understanding the impact of microplastics on soils.
Communications Earth & Environment
