Beschreibung:
<p> Each year a mussel produces an incremental layer of its shell which is composed mainly of calcium carbonate and a small fraction of organic substance. Many other elements are simultaneously deposited in these annual layers, and are assumed to be essentially immobile. Three nuclear analytical techniques, the proton microprobe (μ-PIXE), instrumental neutron activation analysis (INAA), and α-track autoradiography were used to determine the temporal history of concentrations of elements in shells of the freshwater pearl mussel, Margaritifera margaritifera (L.), from four rivers in central Sweden. The high spatial resolution (3μm) of μ-PIXE allows analyses of samples representing small parts of single years. Thirty elements were identified and quantified using INAA technique. Elemental concentrations in old samples (from 1860) were similar to those from young specimens (1970-85). Silver, gold, iron and cobolt decrease strongly and manganese and sulfur increase in connection with acidification after 1940. The present study indicates that shells of living mussels, together with museum or subfossil shell material may be used to date environmental changes caused by natural events and large-scale industrial, agricultural or nuclear contamination. </p>