Assessing spatial and seasonal dynamics and source apportionment of microplastics in Deeporbeel wetland in...

Wetlands acting as pollutant sinks make them a hotspot for microplastics (MPs) pollution, yet source-driven MPs accumulation assessments are limited, representing a gap hindering targeted mitigation strategies, particularly in biodiverse regions. To address this, the present study combined two years pre- and post-monsoon MPs abundances with PCA-APCS-MLR to determine polymer-specific MPs sources in Deeporbeel, a Ramsar site in Northeast India. Water and sediment samples (6 sites × 3 replicates) were collected during both seasons over two years, followed by NOAA-standard protocols and μ-Raman characterization. Water MPs abundance during the pre-monsoon season peaked at sites S2 (0.84 ± 0.16 particles per L) and S6 (1.44 ± 0 particles per L), while post-monsoon at site S6 (1.21 ± 0.02 and 2.12 ± 0.10 particles per L) across both years. Sediment MPs were consistently highest at site S1 (11.22 ± 0.42 and 9.44 ± 1.96 particles per 100 g) during both seasons. Fibers remained >50 % in both media, with PVC (31 %) dominant in sediments and ABS (29 %) in water. PCA-APCS-MLR explained 91.6 % of the total variance in water (meanR²=0.92) and 98.29 % in sediment samples (meanR²=0.98), identifying four and three potential sources, respectively. Among the identified polymers, PVC (59.10 %) dominated water, and ABS (33.1 %) dominated sediment samples. Water MPs linked to industrial and commercial, packaging, household, medical, and automobile-vehicle inputs, whereas sediments reflected site-specific contributions. The identified sources showed the Deeporbeel role as a continuous MPs sink. This polymer-based source apportionment allowed feasible insights for targeted mitigation, enabling management of potential sources and designing seasonal monitoring and control strategies.