Frontiers in Marine Science (Apr 2014)
Cadmium assessment on the intertidal water margins from the Óbidos Lagoon (western coast of Portugal)
Abstract
The Óbidos Lagoon is the largest shallow coastal lagoon in Portugal. Like any other brackish water system, it has been potentially exposed to different sources of contamination (e.g. livestock farming, domestic and industrial sewage). Trace metals are persistent elements present in the water and sediments in their elemental and organic/inorganic forms. In fact, Cadmium is extremely pollutant due to its great solubility in water and high toxicity for organisms. Also, it is classified as a priority substance according to the European Union Water Frame directive. In this context, a seasonal environmental monitoring program was implemented in the intertidal water margins of the Óbidos Lagoon to assess the presence of Cadmium. In 2009 and 2010, eight sampling stations (S) distributed on the shores of the Óbidos Lagoon were chosen and water and sediments were seasonally collected. In all samples, cadmium concentrations were analyzed by Atomic Absorption Spectrometry, with Graphite Furnace Technique. Cadmium dissolved in the water samples was only detected during summer months, with the highest values in the Barrosa’s arm (S3: 0.35 mg/l) in 2009, and at the station further downstream (S1: 0.19 mg/l) in 2010. In the suspended fraction of the water samples the trace metal was detectable in all seasons, with the maximum concentration at the Barrosa’s arm (S4: 1.04 mg/l) in the winter of 2010. Cadmium was not detectable in the sediments during the summers and was sporadically present in the autumn and in the winter of 2009. The highest concentration in the sediments was observed at the Barrosa´s arm (S4: 140.78 mg/kg) in the spring of 2010. As a whole, cadmium contamination appears to be mostly focused on the inner areas of the lagoon, at the Barrosa´s arm, but a clear seasonal pattern of variation was not detectable. These results allow a better understanding of the environmental quality of this ecosystem and may assist in the definition of coastal management measures specifically targeted to trace metal contamination and pollution monitoring.
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