Trace metal speciation in fresh and brackish waters using ultrafiltration, DGT and transplanted aquatic moss

• Main Author: Forsberg, Jerry
• Format: Master Thesis
• Language: English
• Published: Luleå 2005
• Subjects: Geochemistry; Geokemi; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25876

Distribution, mobility, and toxicity of metals in natural waters are strongly related to their aqueous speciation. To understand the behaviour of an aqueous element and the transformation between chemical species, there is a need for reliable methods that enable measurements of specific fractions of metals. Ultrafiltration has frequently been used to study speciation of metals in natural waters. Several disadvantages are, however, associated with ultrafiltration. The procedure is complicated, time consuming and implies sampling and storage of water which may result in a change in metal speciation. A possible alternative or complement to ultrafiltration is the technique of diffusive gradients in thin films (DGT) which provides an in situ measurement of labile metal species. DGT accumulates metals in a time- integrated way and produces a mean concentration over the chosen deployment period. The relatively common occurrence of aquatic moss and their ability to accumulate metals have led to an extensive use of moss as bioindicators in monitoring of aquatic environments. For waters where no native species can be used as bioindicator, transplant techniques have been developed. The aim of this study was to investigate differences and similarities between the trace metal speciation methods; DGT, 1 kDa ultrafiltration, 0.22um membrane filtration and transplanted aquatic moss, and to examine their dependence on water geochemistry. Two studies have been conducted and included in this work. In 2003 and 2004, DGT and 1 kDa ultrafiltration were simultaneously applied at two sampling stations in the Baltic Sea with different salinity and total trace metal concentrations. A total of 16 samplings were performed at the two sites. In 2004 and 2005, DGT, 1 kDa ultrafiltration and aquatic moss were simultaneously applied in the small fresh water stream Gråbergsbäcken in northern Sweden together with a standard 0.22um membrane filtration. The sampling was conducted 10 times over a whole ice free period. In the Baltic Sea ...