Sediment dispersal of PE and PVC primary microplastics in a coastal archipelago surrounding a plastic production industrial complex

Microplastic pollution is a global environmental concern, yet the distribution and fate of primary microplastics, particularly small pre-production particles, remain poorly understood. This study investigates the occurrence, distribution, and sources of microplastics in surface sediments of a fjord system on the Swedish west coast, adjacent to a major petrochemical industrial complex. Microplastics were detected in all 9 samples, with concentrations ranging from 6.7 to 48 particles g⁻¹ dry weight. Polyethylene (PE), polyvinyl chloride (PVC), and polypropylene (PP) dominated the polymer composition, accounting for over 90% of identified particles. Distinct and homogeneous particle morphologies suggest a strong influence from local industrial sources, particularly PE and PVC. Spatial patterns revealed the highest concentrations near the industrial area, with decreasing levels further away and low levels at the reference site, although local hydrography and sediment dynamics influenced distribution. PE was more widely dispersed than PVC, consistent with its lower density and longer residence time in surface waters prior to sedimentation, whereas PVC showed more localized accumulation. The results demonstrate that primary microplastics from industrial activities are a major contributor to sediment contamination in the study area. The complex fjord system influences transport and deposition processes, but overall patterns align with known emission sources and hydrodynamic conditions. This study highlights the importance of addressing industrial emissions of pre-production plastics and provides a scientific basis for environmental monitoring and management strategies.