Moored sediment trap observations collected from fixed moorings in the Great Lakes region and Yellowstone Lake, Wyoming from 1977-04-28 to 2005-03-15 (NCEI Accession 0266598)

Total Carbon, Organic Carbon and Organic Nitrogen Great Lakes Trap Sample Processing Field Collection and Storage Trap bottles were capped on the ship deck, kept in coolers, transported back to the lab in coolers and stored upright under refrigeration. Samples were left to settle in the refrigerator until overlying water in the sample bottle was clear of suspended particles. Size Fractionation Approximately 30 ml of overlying water in a trap bottle was decanted into a beaker (to be used as a rinse). The remaining sample was shaken, sonified, and immediately poured through a 355 micron screen into a clean beaker. To ensure quantitative transfer of material from the trap bottle, it was rinsed with the overlying water previously set aside (see above). If there was still residual material in the trap bottle a DDW rinse was used. (In these cases we would try to minimize the use of DDW). The >355 micron fraction collected on the screen was back-rinsed off the screen and collected onto tared Whatman GF/F filters 4.7cm using a vacuum filter flask. These filters are dried at 70°C and weighed to determine >355 micron size fraction. The <355 micron size fraction collected in the beakers was placed in the refrigerator to settle until overlying water was clear of suspended particles. Overlying water in the sample beaker was siphoned off as much as possible without disturbing the sample. The sample beaker was then frozen. The sample was then freeze dried, weighed and ground with a mortar and pestle to a homogenous powder. The ground samples are transferred to combusted scintillation vials, and stored frozen in the GLERL Trap Archive. Additional Step for Organic Samples Sub-sampled the archived <355 micron size fraction (~25-50 mg) into labeled acetone rinsed 20 mL polyethylene scintillation vials. Covered with an excess of 2N HCl (approximately 2 mls) Samples were then shaken on a shaker table for 24 hours or until the carbonates stopped bubbling. Samples then dried in a 70°C degree oven, reground and stored in dessicator or freezer until CHN analysis. For CHN analysis (same for Organic and Total Carbon and Nitrogen samples) Re-dried samples at 70°C for 20 minutes on day of analysis, then cooled in a desiccator until ready to weigh (must be room temperature). Approximately 12-18mg of sample weighed into tin capsules for CHN analyses. Total Carbon, Organic Carbon and Nitrogen was determined on a CE Instruments EA 11120 CHN analyzer (ThermoQuest Italia, Milan Italy)