. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ELEMENTAL DISTRIBUTIONS IN BIVALVES 63 .15000 30000 25000 w D o o 20000 15000 - 10000 5000. 100 200 300 400 Position (urn) 500 600 Figure 3. Scan across the prismatic/homogeneous boundary in a Mercenaria mcrcenaria thin section. Data were recorded as the area under user-defined regions of interest, with the background subtracted. Data was recorded for 15 s per point (detector live time). Initial Fe concentration is 211 ppm, initial Sr concentration is 1550 ppm. The Fe peak concentration is 1420 ppm. croprobes it is 1 ^m. New
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ELEMENTAL DISTRIBUTIONS IN BIVALVES 63 .15000 30000 25000 w D o o 20000 15000 - 10000 5000. 100 200 300 400 Position (urn) 500 600 Figure 3. Scan across the prismatic/homogeneous boundary in a Mercenaria mcrcenaria thin section. Data were recorded as the area under user-defined regions of interest, with the background subtracted. Data was recorded for 15 s per point (detector live time). Initial Fe concentration is 211 ppm, initial Sr concentration is 1550 ppm. The Fe peak concentration is 1420 ppm. croprobes it is 1 ^m. New PIXE microprobes claim spot sizes of 300 nm. For low-Z elements (Z < 18) EPMA has the greatest sensitivity as well as small spot size. Because of the ready availability of electron microprobes, EPMA is also suited to measurements of higher-Z elements present in quan- tities of several hundred parts per million or more. For measurements of elements present in concentrations of a few parts per million, SXRF is the method of choice. This is the only technique that combines MDLs of a few parts per million with spot sizes of a few micrometers. However, for some measurements, the spot size of the NSLS mi- croprobe (8 ^m) is too large. In these cases, PIXE micro- probes can be used, if the elements are present in large enough concentrations. The greater accessibility of PIXE microprobes also makes them attractive for studies of ele- ments present in concentrations of several tens of parts per million. Bulk analysis techniques cannot provide the same spa- tial resolution as microprobes. The neutron activation studies of Carell ct ai (1987) were performed on shell samples of 10-50 mg. This corresponds to a shell section mm thick by 6 mm long by 3 mm deep. If this section is cut with the thin direction normal to the ventral margin, it represents approximately 1 month of growth. Atomic absorption analysis can detect much smaller amounts of trace elements, hence the limiting factor
Size: 1605px × 1557px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
