Distribution pattern and risk assessment of microplastics contamination in different agricultural systems

ABSTRACT

To explore the existence of microplastics (MPs) in agricultural soils in the Coimbatore region of Tamil Nadu, India, this study was carried out in six agricultural sites with distinct agronomic practices and agricultural inputs. Using the density-digestion separation method, 81% of organic matter (OM) in soils was removed and MPs were quantified and characterised using a stereo microscope and ATR-FTIR. MP abundance of treated sewage irrigated field (1,650 items kg⁻¹) > paddy field (1,500 items kg⁻¹) > integrated farming system field (1,250 items kg⁻¹) > inorganic fertilisers applied field (1,025 items kg⁻¹) > organic manures applied field (1,000 items kg⁻¹) > plastic mulched field (800 items kg⁻¹) was assessed with more than 50% MPs at < 500 µm size, which exhibited that smaller MPs tend to transfer into soil layers and affect soil organisms through the food chain. The most prevailing MP colours were blue (37.71%), black (29.41%), and pink (23.87%) with polyethylene as a widely distributed polymer type among all MPs composition. The risk assessment revealed the highest hazard level in plastic mulched soil with category V contamination irrespective of the MPs abundance. This study emphasises the significant influence of agricultural inputs, irrigation practices, location, and atmospheric inputs of MPs in agricultural sites and provides a baseline for further research to understand the trophic transfer of MPs in agricultural ecosystems and its effects on the food chain.

KEYWORDS:

• Microplastics
• agricultural soils
• risk assessment
• treated sewage irrigation
• agricultural inputs
• polyethylene

Acknowledgments

The authors would like to thank Tamil Nadu Agricultural University, Coimbatore, and Vellore Institute of Technology for providing all the facilities for conducting this study. The authors acknowledge G K Dinesh for assistance in generating FTIR graphs (Supplemental material).

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03067319.2024.2309553.

Additional information

Funding

This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.