Baseline characterisation of microlitter in the sediment of torrents and the sea bottom in the Gulf of Tigullio (NW Italy)

Microlitter (<5 mm) distribution was investigated in the bottom sediments of the Entella Torrent and its tributaries as well as in the sea area in front of its mouth (Gulf of Tigullio; NW Italy). Microlitter was extracted from sediment using a concentrated hypersaline solution (1.2 g cm−3), filtered with 0.45-μm porosity and black grid membranes and examined using a binocular microscope. Items were counted, dimensionally measured and classified according to type, shape, colour and appearance. A total of 56 torrent and sea sediment samples revealed the presence of 4,302 items. The mean concentrations were 1.5 items cm−3± 1.3 standard deviation (SD) and 1.6 items cm−3± 1.3 SD for torrent samples and sea sediment samples, respectively. Transparent fibres predominated, followed by fragments. The most common colour was white-cream. In total, 1.8% of items were analysed with Fourier transform infrared spectroscopy (FT-IR) 2D imaging, using a focal plane array (FPA) detector to identify their composition. Nylon was the most common plastic polymer type; however, approximately 50% of the analysed samples consisted of cotton transparent fibres. The influences of human activities (cities, port and discharges) on microlitter composition were highlighted and torrents were confirmed as a vector of microlitter from land to sea.