Occurrence, distribution and ecological risk of trace metals and organic pollutants in surface sediments from a Southeastern European river (Someşu Mic River, Romania)

The increasing contamination of fresh water resources by trace metals and persistent organic pollutants is a major environmental concern. In the present study, we investigated, for the first time, the distribution, sources and ecological risk of trace metals and organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), in surface sediments from a Southeastern European river (Somesu Mic River, Romania). Concentrations of Cd, Cr, Cu, Pb, Ni and Zn ranged from 0.04 to 0.4, 9.4 to 43.15, 7.2 to 65.6, 12.3 to 131.4, 14.7 to 47.7 and 42.1 to 236.8 mg kg−1 dw, respectively. Concentrations of total PAHs, PCBs and OCPs ranged from 24.8 to 575.6, 2.7 to 252.7 and 2.1 to 44.3 ng g−1 dw, respectively. Some sediment parameters, i.e., pH, total organic carbon (TOC) and total organic matter (OM) contents, played a significant role in the spatial distribution of contaminants. A combined analysis based on diagnostic ratios and multivariate analyses revealed PAHs originating mainly from pyrolytic sources. PCB compositions showed distinct contamination signatures for tri- to tetra-chlorinated PCBs, characteristic of contamination by Aroclor-1016 and -1254 technical mixtures. The dominant OCP congeners were α-HCH and p,p′-DDD, reflecting past use of technical HCHs and DDTs in agricultural practices. Metal source and pollution status was assessed using geoaccumulation index and enrichment factor, which indicate widespread pollution by Pb, Cd, Zn, Ni and Cu. The use of Sediments Quality Guidelines (SQGs), mean effect range-median quotient (m-ERM-Q) and toxic equivalent factor (TEF) indicated that the highest ecological risks occurred for PCBs and DDTs. This work presents not only initial baseline information on the extent of organic and inorganic contaminations in a river of ecological and economical interest, but also provides a diagnostic ratio/statistical combined approach that can be used to evaluate sediment quality in similar environments.