Microplastic Evaluation in Water and Sediments of a Dam Reservoir–Riverine System in the Eastern Carpathians, Romania

The complex aquatic system of dam reservoirs is known to trap emerging pollutants as microplastics (MPs) in sediments and water column. Considering the knowledge gaps in this type of environment, we investigated the amount and distribution of MPs in the surface water layer, as well as in the surface and deep sediments of the Siriu Reservoir in the Buzău River system, which is located in the southern area of the Eastern Carpathians, Romania. There was a discrepancy between MP abundancy in both water and sediment samples collected near the reservoir (5.3 MPs/m3, 315.5 MPs/kg) and at several kilometers downstream of the dam (1.4 MPs/m3, 132.5 MPs/kg). The chronological accumulation of MPs in the lacustrine sediments was determined by analyzing 5 cm intervals of a 50 cm length core extracted from the reservoir bed. By comparing the concentration of MPs identified in each interval with the solid debit volumes registered in the last decade, we found that flood events could be traced easily due to abundant MP accumulation. Morphologically, the particles were observed mainly as fibers and fragments. Fourier transform infrared spectroscopy (FT-iR) investigations identified most of the MPs as polypropylene (28%), polyethylene (26%), and polyethylene terephthalate (19%).