USA rivers suspended and bottom sediment major and trace elements

Description

Data describes the major and minor element composition of major rivers from the continental United States

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Suspended sediments were collected in May to June 1986, excepted for the Connecticut River that was sampled in April 1987. River bottom sediment was collected as submerged sediment from near the suspended sediment sampling site. In many cases (11 rivers), duplicate samples of bottom sediment were taken. Suspended sediment samples were filtered onto either 0.4 m Nucleopore (preferred) or Millipore 0.45 m filters (for rivers with high suspended sediment loads). Samples were allowed to air dry naturally. For the river suspended and bottom sediment, samples were well homogenized, and a portion of the dried sample (ca. 100 mg) was weighed into cleaned Teflon bombs where they were microwave digested in a solution of HNO3:HF:HCl in a ratio of 3:2:1 (3 ml total) for 10 minutes at 180 oC, after a 15 minute ramp to the digestion temperature. A triplicate set of blanks were digested similarly, but without any added sample. Also digested were certified marine sediment standard MESS4 and stream sediment NCSDC 73309. After digestion, 10 ml of 4% boric acid was added, and some sediment samples were spiked with a standard mixture of both high and low concentration. After this, the Teflon vessels were re-closed and digested in the microwave for 30 minutes at 170 oC after a 15 minute ramp to the digestion temperature. After this, samples were cooled and diluted both 20 and 400 times in matrix equivalent solution for ICP-MS analysis. A typical ICP-MS analytical run included standards of 0.1, 0.5, 1, 10, 100, 500 and 5000 g l-1 together with milli-Q purified water as a blank. Standards and blanks were matrix equivalent with the samples. Some samples were run in triplicate to assess standard deviation, while all others were run in duplicate. Recovery of standard samples was typically between 90 and 110 %, while recovery of the elemental spikes was typically 100 +/- 5%. Relative standard deviations of samples run in triplicate was generally within 2-3%, but was up to 32% for Cd, and occasionally 10-12% for some of the other elements. All recovery and standard deviation results are shown in the supplemental information.

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