Temporal variation of mercury in Turkish Black Sea waters and associated risk assessment

Presence of metals even at trace levels in natural waters pose sever health risks. Heavy metals are introduced to coastal and marine environments through a variety of sources and activities including sewage and industrial effluents where Black Sea is not different. However, metals behave differently in Black Sea as it an enclosed body. Coastal areas of Turkey face great challenges due to heavy metal contamination caused by rapid urbanization and industrialization. The aim of this study was to investigate the spatial and temporal distributions of total mercury (Hg) in seawater at the mid-Black Sea coast of Samsun, Turkey. The samples were collected from 13 monitoring stations, from the three distances in four seasons during the year 2013. The samples were analyzed for physicochemical parameters along with contamination and enrichment factors. The distribution of Hg is nearly random along the studied coast but obtained values ranges from 0.57 to 12.6 μg/L with an average of 5.24 μg/L were above permissible limits. It was observed that number of samples collected during wet seasons (winter and autumn) with Hg were higher. High enrichment factor 0.331 and contamination factor 25.2 was recorded. Hg present at sampling station M27 was due to point source, a possible ship activity indicated by enrichment factor. The sources responsible for water pollution with Hg are mainly municipal and industrial effluents, leaching, agricultural and pasturage runoff and oil spills. Furthermore, due to unique hydrography of Black Sea, risk of Hg accumulation is high. Interestingly, a direct relation between basicity and Hg concentration was observed. i.e. highest concentration was found on pH 8.33.