Spatiotemporal Dynamics of Polychlorinated Biphenyl Pollution in the Bottom Sediments of the Salgir River (Crimean Peninsula)

We investigated the content and distribution of indicator polychlorinated biphenyls (PCBs) in the bottom sediments of the Salgir River, the longest river of the Crimean Peninsula. The results of PCB pollution analysis at 13 sites in the steppe segment of the river are reported. The PCB contents of surface sediments were determined using gas chromatography with a micro-electron capture detector. Significant spatial and temporal heterogeneity in PCB distribution was observed. The total content of six indicator PCB congeners (∑6PCBs) ranged from 3 ng/g dry weight in the upper reaches of the river to 252 ng/g in the middle reaches, and the most contaminated areas were located near the villages of Krasnaya Zor’ka and Pyatikhatka. The mean ∑6PCB values in three cores at the villages of Iskra, Pyatikhatka, and Izobil’noe decreased downstream and amounted to 194, 18, and 6 ng/g, respectively. The profiles of PCB congeners in sediment cores in the middle reaches and mouth of the river differed in both concentration level and the depth of maximum values. Sedimentation rates were determined to vary between 0.37 and 0.42 cm/y, which is similar to the values reported for the steppe rivers of Europe. It was shown that the vertical distribution of PCB congeners in the bottom sediments is controlled by variations in anthropogenic input rather than natural sedimentation processes. The highest sediment flux to the surface sediments of the Salgir River (1012 μg/m2 y) was documented near Pyatikhatka, and the lowest (10 μg/m2 y), in the mouth region of the river. Possible PCB pollution sources include the sites of electrical waste disposal for the surface sediments and the use of PCB-containing pesticides in agricultural areas in the mid-20th century for deeper core samples. It was shown that sedimentation processes contribute to river self-purification from PCBs, leading to their partial burial in bottom sediments.