although this can vary with the type of sorbent media and pH (Wu and Zhou 2009). Unfortunately, in this current experiment no measurements of pH were reported despite the potential for changes in pH to be caused by chemical reactions between the dissolved metal compounds and the shell material (Färm 2002; Genç-Fuhrman et al. 2007; Wu and Zhou 2009). It is important for future research to either measure pH or control for possible effects from varying pH