Microplastics and plastic additives in rainwater and rainwater harvesting systems in the Greater Jakarta Coastal Region, Indonesia

Microplastics and plastic additives in rainwater harvesting systems (RWHS) represent a potential emerging concern in coastal urban environments. This preliminary baseline study investigated microplastic polymers and selected plastic additives in rainwater and RWHS water from two coastal sites in the Greater Jakarta coastal region, Indonesia, using pyrolysis gas chromatography-tandem mass spectrometry (Py-GC/MS/MS) for microplastic polymers and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for plastic additives. In RWHS samples, PVC, PET, and PMMA were detected, with differences in polymer composition and concentration between the two sampling locations. Plastic additives were also detected in rainwater and RWHS samples after blank correction, while no target microplastic polymers were detected above the method detection/quantification limits in the analyzed rainwater sample. The observed site-specific differences suggest that contamination patterns may vary between RWHS locations and may be influenced by local environmental conditions, atmospheric deposition, and possible interactions with RWHS infrastructure. Given the limited sampling design, potential blank-related uncertainty for some additives, and absence of direct source attribution, the findings should be interpreted as preliminary baseline evidence. Future studies should include expanded sampling, improved quality control, and direct characterization of RWHS materials.