Comparative microplastic analysis in urban waters using μ-FTIR and Py-GC-MS: A case study in Amsterdam

Area of Science:

• Environmental Science
• Analytical Chemistry

Background:

• Microplastic (MP) contamination is a global issue in freshwater systems.
• Current MP analysis often focuses on particle numbers, underutilizing spectroscopic methods for mass estimation.
• Accurate MP mass quantification is crucial for understanding environmental impact.

Purpose of the Study:

• To compare micro Fourier-transform infrared (μ-FTIR) imaging and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) for identifying and quantifying microplastics in urban water.
• To assess the comparability of these techniques for both particle number and mass concentration measurements.
• To investigate microplastic abundance in Amsterdam's canals, considering location and season.

Main Methods:

• Two sampling campaigns (summer and winter) were conducted in the Amsterdam canal network.
• An in-situ volume-reducing pump collected surface water microplastics (10-300 μm).
• Microplastics were analyzed using μ-FTIR imaging and Py-GC-MS for particle number and mass concentration.

Main Results:

• Microplastic concentrations ranged from 16-107 MP/m³.
• Mass concentrations estimated by μ-FTIR were 2.0-789 μg/m³, and by Py-GC-MS were 8.5-754 μg/m³.
• Both methods showed comparable trends in MP abundance, with variations attributed to inter-methodological differences. Higher concentrations were found in the city center, with seasonal variations noted in high-activity areas.

Conclusions:

• μ-FTIR imaging and Py-GC-MS provide comparable results for microplastic mass concentration in urban water.
• Microplastic pollution is elevated in urban centers, with seasonal influences in areas of high human activity.
• Further research is needed to refine and standardize microplastic mass quantification techniques.