Spatial and seasonal variations of acid volatile sulphide (AVS) and simultaneously extracted metals (SEM) in Dutch marine and freshwater sediments

Within the framework of setting environmental quality criteria for certain heavy metals in sediment, Acid Volatile Sulphide (AVS) has been proposed as the primary standardisation parameter in combination with the amount of simultaneously extracted metals (SEM). From a series of toxicity studies published in the literature, it was concluded that the SEM/AVS ratio is able to predict quite well the availability of various heavy metals for different organisms. Incorporation of the SEM/AVS ratio in deriving sediment quality criteria has been proposed, principally in the U.S. This study has been designed to investigate the applicability of the AVS-concept in Dutch sediment quality criteria. Due to the dynamic behaviour of AVS especially in natural systems, knowledge with respect to spatial and seasonal variations of AVS and SEM levels is required for a proper application of the AVS-concept. AVS has been detected in 95% of the investigated sediment samples. The corresponding SEM/AVS ratio was found to be smaller than one in 19 out of 21 samples. According to literature data, toxic effects from heavy metals are expected to be absent under these conditions. Hence, implementation of the AVS-concept in Dutch quality criteria seems to be justified regarding our observations. However, seasonal variations in AVS and SEM concentrations were observed, which may lead to variations in metal availability for organisms during the year. Although the seasonal behaviour was different for various sediments, the corresponding SEM/AVS patterns were found to be smaller than one in all cases. This observation is very promising for further acceptance of the AVS-concept in setting quality criteria.