TRACE METALS ENRICHMENT IN THE SEDIMENTS OF A MINING IMPACTED ESTUARY (NORTH OF SPAIN)

Trace elements are important components of natural water systems. Their behaviour is carefully investigated in environmental studies due to their key role in biogeochemical processes involving water, sediments and biota. Natural concentrations of trace elements in these matrices primarily depend on the local lithological and mineralogical characteristics. Unfortunately, as a result of human activities, the contemporary environment has been affected by several additional sources of trace elements, such as potentially toxic metals and metalloids. If the anthropogenic inputs of these elements in the natural systems exceed the local background values, we can expect to observe some effects on their biogeochemical cycles. These may also result in their anomalous accumulation in biota and, possibly, in human beings through fish and mussel consumption. Estuaries represent unique water systems, a vital link between the land and the sea. Due to mixing of fresh and seawater, estuaries are characterized by pronounced gradient of many parameters such as salinity, temperature, pH, redox potential as well as suspended particle matter composition. Besides, they often act as a trap for material brought by rivers, which may also include various contaminants, included potentially toxic elements, associated with anthropogenic activities. The primary aim of this work was to investigate the geochemical characteristics of the present sediments of the Nalón River estuary compared to the local geochemical background in order to assess possible anomalies due anthropogenic contributions which can have altered their lithogenic properties. For this purpose, spatial and temporal distributions of major and trace elements in the sediments were deeply investigated.