Same-source analysis of microplastics and polycyclic aromatic hydrocarbons in surface water using unified pretreatment, TD-GC/MS, and Py-GC/MS

Microplastics can accumulate hydrophobic organic pollutants, but microplastic identification and PAH analysis are often conducted using separate subsamples or different pretreatment routes, which weakens the correspondence between polymer type and co-occurring contaminants. Here, we established an application-oriented same-source analytical workflow for the joint analysis of microplastics and PAHs affiliated with the enriched microplastic-containing fraction in surface-water samples. The enriched sample obtained after unified pretreatment was analyzed by thermal desorption-GC/MS for affiliated PAHs and by pyrolysis-GC/MS for microplastics. By generating both types of information from the same enriched sample, this workflow reduces sample splitting and simplifies pretreatment prior to instrumental analysis. After fractionated filtration and density separation, the enriched microplastic-containing fraction was subjected to thermal desorption-GC/MS for PAH analysis and pyrolysis-GC/MS for microplastic fingerprint characterization. Applied to seven representative watershed sections, six polymers PMMA, PP, PET, PVC, PC, and PE were detected. Significant spatial heterogeneity in microplastic concentrations was observed across sampling sites, with the highest level at S6 (1.3 μg/mL) and the lowest at S2/S5. Polymer composition also varied markedly: PVC dominated in the middle reaches (S2-S4), while PET became the dominant polymer (>65%) in downstream sites (S6-S7). Twelve PAHs affiliated with the enriched microplastic-containing fraction were identified, with estimated ∑PAHs levels ranging from 10 to 500 ng/g, mostly low-ring species 60-80%. This workflow enables joint characterization of microplastic types and affiliated PAHs from the same enriched sample, providing an efficient analytical approach for integrated monitoring and comparative analysis at the watershed scale.