This data repository contains the following files, organised as compressed folders:
	•	1 Overview Files.zip Source data used to generate figures (Figure 2; Extended Data Figures 1, 3, 4, and 7).
	•	2 PTRwid output (ppb files).zip PTR-MS data and code for the first level of data analysis, providing sVOC concentrations per second of TOF measurement, calculated in ppb.
	•	3 Averaged PTRwid data (data reduction).zip Second-level data analysis: signal integration over 7 minutes after the TD temperature reached 200°C.
	•	4 Output NP fingerprinting algorithm.zip Third-level data analysis enabling identification and quantification of nanoplastics using the 40-ion approach (Materic et al., 2020).
	•	5 Output blank subtraction and LoD filter.zip Continuation of second-level analysis: blank subtraction for each m/z and limit of detection (LoD) filtering based on system blanks.
	•	7 Montecarlo.zip Code and supporting files for the Monte Carlo simulation of theoretical organic matter (OM) overestimation.
	•	8 Sargassum.zip Data and fingerprints used to estimate organic matter interference on the model plant Sargassum sp.
	•	9 Gyre circulation.zip Code and data used for calculating the gyre mixed-layer volume.
Raw PTR-MS data files are available uncompressed as .h5 files (297 files)