VARIATIONS OF HEAVY-METALS IN WATER, SEDIMENTS, AND BIOTA FROM THE DELTA OF EBRO RIVER, SPAIN

Cadmium, chromium, copper, lead, and zinc were measured in water, sediments, and biota [algae (Ulva lactuca) and molluscs (Cerastoderma edule and Tellinella pulchella)] of the two bays from the Delta of Ebro river (in southeastern Catalonia, Spain), to determine if concentrations were elevated due to pollution by a variety of agricultural and industrial activities. The effect of temperature (seasonal variation) and the influence of depth on the variation of metal levels were assessed. Metal concentrations were determined by atomic absorption spectrophotometry or by inductively coupled plasma spectrometry. As expected, most metals accumulated mainly in sediments and molluscs. A correlation study (Pearson) between the different elements showed significant differences for lead-cadmium and copper-chromium in algae, zinc-chromium in sediments, and copper-chromium in water. Metal concentrations found in sediments, water, and molluscs were quite similar at 10 degrees C and 30 degrees C, whereas the concentrations of these metals in samples of algae collected in summer were higher than those found in samples collected in winter. The levels of cadmium, copper, lead, and zinc found in this study were similar or lower than corresponding data reported from other areas, while chromium levels were about the same or higher than those found in surveys elsewhere.