The mobilization of hazardous elements after a tropical storm event in a polluted estuary

The Tubarão River (Santa Catarina, Brazil) is affected by hazardous elements (HEs) pollution from abandoned coal mines, agricultural activities, urban discharges, industrial and leisure zones, etc. In order to study the distribution and sources of HEs contamination in a polluted estuary after a tropical storm, waters and surface sediments were collected from 15 sampling sites along the Tubarão River. The concentration of 24 elements (Ag, Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, Ti, Tl, V, W, and Zn) were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the mineralogical composition of the sediments by Raman spectroscopy and X-ray diffraction (XRD). The metal concentrations in water and sediment showed wide spatial variation due to the variability in water discharges and anthropogenic inputs after a storm. In general, higher metal concentration in water and lower in sediments were found upstream (closer to coal mining). Downstream sampling sites and the Oratorio River sampling site (one of the eight tributaries of the estuary) showed the highest values in sediment samples. Normalized and Weighed Average Concentrations (NWAC) were calculated, which allow us to identify, in a very simple way, the sampling sites of higher concern (hotspots of contamination) in the studied area. NWAC suggested that the strong rainfall events could affect to the metal distribution in sediments. The results of this study were compared with a previous study in the same area during dry season by Principal Component Analysis (PCA), showing changes in environmental pollution of the sediment after a strong storm event.