Measurement of Acid Volatile Sulphide and Simultaneously Extracted Metals in Sediment from Lake Albufera (Valencia, Spain)

Lake Albufera (Valencia, Spain) is part of a legally protected wetland of international importance. However, it has deteriorated as a result of urban, industrial, and farming pollution. It is highly eutrophic, and its sediment contains persistent pollutants, such as heavy metals. In anoxic sediments, sulphides represent an important binding phase for heavy metals. In this study, acid volatile sulphide (AVS) and simultaneously extracted metals (SEM) were analyzed in surface sediment extracted from Lake Albufera; organic matter and total metals were also analyzed. Twelve sites were sampled in each of three sampling campaigns conducted in March and September 2007 and September 2008. The results revealed elevated organic matter contents varying between 6.9 and 16.7%. The concentrations of AVS in the lake were high, ranging from 8.5 to 48.5 mu mol/g; the lowest concentrations were found in the central sites. The AVS results displayed significant differences between the samples from the winter and summer of 2007 (p < 0.05) but not between the two summer samples. The results obtained for SEM varied from 1.4 to 4.8 mu mol/g. The difference SEM-AVS was less than zero for all sampling locations and campaigns, indicating the existence of a sulphide pool able to bind metals.