## 4 Conclusions  
PAH concentrations in sediments of the mid-Adriatic Sea show great variability, ranging from very low concentrations in the open sea area to very high concentrations in urbanized, coastal areas. The application of the PMF model for PAH source apportionment revealed the presence of four main sources of PAH pollution in the investigated area. Among them, Source 1 and Source 4 can be considered as the most important ones since their contributions to the total PAH pollution were observed in each studied area. Positive Matrix Factorization provided detailed information about PAH sources and the contribution of each source to the total PAH in each location, which makes it a reliable tool for the management of various activities in the Adriatic region. To obtain more accurate information on pollution sources, the dataset used as model input should include a greater number of stations as well as other pollutants, such as trace metals, pesticides, dioxins, antifouling chemicals, etc. The PAH-toxicity assessment revealed a high cancer risk associated with PAH concentration in the sediments of Sibenik Bay, while in the rest of the study area the cancer risk associated with the sediment concentrations of PAH was low. While these results are in good agreement with the results obtained by applying the sediment quality guidelines, they differ greatly from the results of the bioassay used to test the acute toxicity of the sediments. It can be concluded that additional bioassays conducted on a larger number of different marine species are needed to accurately assess the environmental risk associated with PAH. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13126992/s1](https://www.mdpi.com/article/10.3390/app13126992/s1)]([https://www.mdpi.com/article/10.3390/app13126992/s1](https://www.mdpi.com/article/10.3390/app13126992/s1)), Figure S1: Chromatogram of the PAH mixture in sediment sample separated by DB5-MS column and obtained by GC-MS operating in the SIM mode. Table S1. Sampling locations and descriptions of the sites in the Coastal zone and along the Mid Adriatic transect selected for the Source apportionment and toxicity assessment. Table S2. Sampling locations and descriptions of the sites in Kastela and Sibenik Bay selected for the Source apportionment and toxicity assessment. Table S3. List of parent and alkyl-substituted PAH, sulphur heterocyclic aromatic compounds and oxygen heterocyclic aromatic compounds determined in sediment samples; abbreviation, molecular weight and internal standard used as a reference. Table S4. PAH concentration (ug kg\({}^{-1}\) dry sediment weight) with limits of detection (LOD) determined in the sediments of Coastal area and measurements uncertainties for each sample used as input data matrices for PMF. Table S5. PAH concentration (ug kg\({}^{-1}\) dry sediment weight) with limits of detection (LOD) determined in the sediments of transect area and measurements uncertainties (M.U.) for each sample used as input data matrices for PMF. Table S6. PAH concentration (ug kg\({}^{-1}\) dry sediment weight) with limits of detection (LOD) determined in the sediments of Kastela Bay are and measurements uncertainties (M.U.) for each sample used as (M.U.) for each sample used as input data matrices for PMF. Table S7. PAH concentration (ug kg\({}^{-1}\) dry sediment weight) with limits of detection (LOD) determined in the sediments of Sibenik bay and measurements uncertainties (M.U.) for each sample used as input data matrices for PMF. Conceptualization, J.M. ; Methodology, J.M. ; Software, J.M. ; Formal analysis, J.M. and J.V. ; Resources, G.K.; Writing--original draft, J.M. ; Writing--review & editing, J.M. and J.V. ; Visualization, J.M. ; Project administration, G.K.; Funding acquisition, G.K. All authors have read and agreed to the published version of the manuscript.