The impact of biodegradable plastics on methane and carbon dioxide emissions in soil ecosystems: a Fourier transform infrared spectroscopy approach

Biodegradable plastics (BPs), promising eco-friendliness, raise environmental concerns as they degrade into numerous microplastics (Bio-MPs). The impact of Bio-MPs on methane (CH₄) and carbon dioxide (CO₂) emissions in soil ecosystems remains largely unexplored. Utilizing Fourier transform infrared (FTIR) spectroscopy, we innovatively designed a circulating system, integrating a long optical-path gas cell with a static chamber for continuous and convenient CH₄/CO₂ monitoring in paddy soils with the addition of Bio-MPs (PBAT). On the 7th day of incubation, we observed a significant increase in CH₄/CO₂ absorption peaks due to the addition of PBAT, with enhancements of 92-fold and 213-fold, respectively. Built upon this system, we explored a quantitative method based on the main absorption peak (3010 cm^-1) for CH₄, and calculated cumulative emissions. Additionally, we analyzed attenuated total reflection (ATR) spectra of soil with and without Bio-MPs based on FTIR spectrometer, revealing the characteristic response in soil ATR spectra triggered by PBAT, and demonstrating ATR spectroscopy's potential for identifying soil contamination by Bio-MPs. This study aims to broaden and improve the utilization of FTIR spectroscopy for the purpose of monitoring soil GHG emissions and identifying soil contaminated by Bio-MPs, thereby offering significant insights into the influence of Bio-MPs on climate change.