How Microplastics Affect Fungicide Build-Up in Corn

Jim Crocker
22nd May, 2024

How Microplastics Affect Fungicide Build-Up in Corn

Image Source: Natural Science News, 2024

Key Findings

  • The study by Zhejiang University examined how polyethylene microplastics (PE-MPs) affect the behavior of three fungicides in soil and maize plants
  • PE-MPs increased the adsorption of hydrophobic fungicides azoxystrobin and tebuconazole to soil, reducing their bioavailability
  • The presence of PE-MPs prolonged the persistence of azoxystrobin and tebuconazole in soil and decreased their accumulation in maize plants
Microplastics (MPs) and pesticides are pervasive in agricultural soils, but their combined effects on soil-plant systems have been underexplored. A recent study conducted by Zhejiang University[1] sheds light on this issue by examining how polyethylene microplastics (PE-MPs) influence the behavior and bioavailability of three commonly used fungicides—metalaxyl, azoxystrobin, and tebuconazole—in soil and maize plants. The research found that the adsorption of fungicides to both MPs and soil was significantly influenced by their octanol/water partition coefficients (logKow), a measure of a substance's hydrophobicity. The addition of 5% PE-MPs to the soil notably increased the adsorption of the hydrophobic fungicides azoxystrobin and tebuconazole, due to their higher affinity for PE-MPs compared to soil. However, the hydrophilic fungicide metalaxyl showed negligible changes in adsorption. This increased adsorption led to a decrease in the bioavailable fractions of azoxystrobin and tebuconazole in the soil, particularly in the in situ pore water, which resulted in prolonged persistence of these fungicides in the soil and reduced their accumulation in maize plants. The study also found that PE-MPs had a more pronounced effect on tebuconazole than on azoxystrobin, likely due to tebuconazole's higher logKow, which makes it more prone to adsorption by PE-MPs. Metalaxyl's bioavailability remained largely unaffected by the presence of PE-MPs. These findings align with earlier research that has highlighted the significant presence of MPs in agricultural soils due to various sources such as agricultural films, livestock manure, irrigation water, and air deposition[2][3]. For instance, a study examining the spatial distribution of MPs in China's farmland found average abundances of 2462 ± 3767 items/kg in agricultural soils, with higher concentrations in greenhouses and mulched farmlands[2]. Another study identified that mulching soils contained larger amounts of MPs compared to non-mulching soils, indicating that agricultural practices significantly contribute to MP contamination[3]. Moreover, the long-term application of organic fertilizers like pig manure has also been shown to introduce MPs into agricultural soils. Research has demonstrated that soils amended with pig manure over 22 years contained significantly higher MP concentrations than control plots, suggesting that repeated manure application can lead to substantial MP accumulation in soils[4]. The current study from Zhejiang University provides crucial insights into how MPs can alter the environmental fate of pesticides, thereby affecting their persistence and bioavailability in agricultural systems. By demonstrating that PE-MPs can increase the adsorption of hydrophobic fungicides to soil, thereby reducing their bioavailability and accumulation in plants, this study underscores the need for comprehensive risk assessments of MP and pesticide co-contamination. In summary, the findings from this study contribute to our understanding of the complex interactions between MPs and pesticides in agricultural soils. They highlight the importance of considering both MPs and pesticides in environmental risk assessments and developing strategies to mitigate their combined impacts on agroecosystems.

AgricultureEnvironmentPlant Science

References

Main Study

1) Different effects of polyethylene microplastics on bioaccumulation of three fungicides in maize (Zea mays L.)

Published 21st May, 2024

https://doi.org/10.1007/s44297-024-00028-x

Related Studies

2) Spatial Distributions, Compositional Profiles, Potential Sources, and Intfluencing Factors of Microplastics in Soils from Different Agricultural Farmlands in China: A National Perspective.

https://doi.org/10.1021/acs.est.2c07621

3) Microplastics in agricultural soils on the coastal plain of Hangzhou Bay, east China: Multiple sources other than plastic mulching film.

https://doi.org/10.1016/j.jhazmat.2019.121814

4) Abundance and morphology of microplastics in an agricultural soil following long-term repeated application of pig manure.

https://doi.org/10.1016/j.envpol.2020.116028


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