Carbon/Carbonate and Nitrogen Analyses, Leg 64, Gulf of California

Abstract

We analyzed Leg 64 sediments for total carbon and acid-insoluble (organic) carbon using a LECO WR-12 Analyzer. We first dried the 3-5 cm 3 sediment samples at 105 °-l 10°C (some shallow sediments used for the C-H-N analyses were dried at 45-55 °C) and then ground them to a homogeneous powder. The ground sediment was redried and two samples (0.1 g and 0.5 g) were then weighed in LECO clay crucibles. The 0.5-g sample was acidified with a 10% hydrochloric acid solution and then washed with distilled water. We then dried and analyzed the sample for acid-insoluble carbon, listed in Table 1 as "organic" carbon. The 0.1-g sample was analyzed for total carbon without further treatment. If the result showed less than 10% CaCO 3 , we analyzed an additional 0.5-g sample for greater accuracy. We calculated the calcium carbonate percentages as follows: (% total C-% organic C) × 8.33 = % CaCO 3 .