A computer program to process data from a direct current plasma emission spectrometer

This program processes data from a Spectraspan IIB spectrometer retrofitted with a Spectrajet III plasma excitation source (Spectrametrics, Inc ., Andover, MA). The spectrometer is operated manually and can determine only one element at a time. Accordingly, the program treats data for each element individually. Two of the spectrometer's performance characteristics tend to change gradually during normal operation: average blank count and analytical sensitivity. The program compensates for these variations. For the program to process data from the spectrometer, a reagent blank and a high standard (in this order) should be aspirated first; then the high standard and blank (in this order) should be run again after every six or fewer samples . The program, moreover, causes all data to be converted to logarithmic form before being used in computation. This makes possible the calculation of statistically valid confidence limits about predicted analyte concentrations. The program consists of a main section, DCPEOES, and three external sub-routines: BASELINE, SENSITIV, and XLNSQFT. BASELINE compensates for any change in the average blank count, and SENSITIV corrects for any variation in analytical sensitivity. XLNSQFT governs all correlation and prediction functions and has two interchangeable versions: one for first-order; the other for second-order, correlation.Prepared for the United States Department of Energy under Contract DE A102-81EV10694 and for the National Science Foundation under Grant OCE 81-19056

The accumulation of barium by marine phytoplankton grown in culture

Marine phytoplankton have been implicated as potentially important vectors for the vertical transport of barium in the oceans. To better assess the extent to which phytoplankton can influence the geochemical cycling of barium, its bioconcentration was studied in 21 clones of 19 species of marine phytoplankters belonging to 9 algal classes. Barium levels in the ash ranged from less than 2 μg g–1 for the coccolithophore Emiliania huxleyi and the red alga Porphyridium cruenturn to 589 μg g–1 for the flagellate Tetraselmis levis. Concentrations ≥4000 μg g–1, previously reported for certain samples of diatom ash were not encountered in this study. Concentration factors on a volume basis (VCF) ranged from 0 to 3.2 × 104; the geometric mean VCF for all species was 225. Diatoms and coccolithophores generally had lower VCFs (geometric means of 90 and 12, respectively) than did other species; dinoflagellates had a geometric mean VCF of 490. Experiments with the diatom Thalassiosira pseudonana indicated that Ba cell–1 increased linearly with ambient Ba concentration. Experiments to localize the site of Ba deposition in diatom cells indicated that most of the Ba was associated with the frustules rather than with the organic fraction. Dinoflagellates and several other algae not only concentrated Ba to relatively high levels, but also accumulated Si when grown in Si-enriched medium, although they grew at least as well without added Si as with it. Ba and Si accumulation were generally negatively correlated

The determination of rare earth elements in marine sediments by ion-exchange separation and ICP emission spectrometry

A method has been developed to measure rare-earth elements (REE) in gram-sized marine sediment samples. A strong acid digestion technique followed by ion-exchange chromatography is used to solubilize, separate, and purify the REE from other matrix components. Instrumental detection is by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Excellent precision and accuracy were proved by analyses of unknown sediment replicates and standard reference rock samples. Blanks and empirically determined detection limits are discussed in relation to measured REE concentrations in sediments. Direct evidence is given for the co-precipitation and fractionation of the REE by precipitates formed as a result of the acid digestion with HF. A technique for dissolving these is then presented.Funding was provided by the National Science Foundation under grant Number OCE 84-17910; and the United States Department of Energy under grant Number DE-AC02-76EV03566