Occurrence of Semi-Volatile Organic Compounds in Sediments of the Nerbioi-Ibaizabal Estuary (Bilbao, Spain): Spatial and Temporal Distribution and Ecological Risk Assessment

The occurrence and spatial distribution of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), fragrances, UV filters and photoinitiators were investigated in surface sediments of Nerbioi-Ibaizabal estuary between 2005 and 2013, in 2020. Samples were extracted by focused ultrasound solid–liquid extraction technique and analyzed by gas chromatography coupled with mass spectrometry. Total PAHs, PCBs, OCPs, musks, UV filters and photoinitiators concentrations ranged between not detected (n.d.) and 43000 ng g⁻¹, n.d. and 2500 ng g⁻¹, n.d. and 820 ng g⁻¹, n.d. and 880 ng g⁻¹, n.d. and 91 ng g⁻¹ and from nd to 120 ng g⁻¹, respectively. Hexachlorocyclohexanes (HCHs) were ubiquitous in the estuary, suggesting that these compounds, although banned, leach from landfills. The PCB concentrations showed a decreasing trend. Ecological risk assessments based on sediment quality guidelines (SQGs) and risk quotient (RQ) suggested semi-volatile organic compounds could represent a potential ecological risk in the Nerbioi-Ibaizabal estuary.