Factors influencing the biogeochemistry of sedimentary carbon and phosphorus in the Sacramento-San Joaquin Delta |
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| Authors: | E B Nilsen M L Delaney |
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| Institution: | (1) US Geological Survey, California Water Science Center, 6000 J Street, Placer Hall, Sacramento, CA 95819-6129, USA;(2) Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory L-397, P.O. Box 808, 7000 East Avenue, Livermore, CA 94551, USA |
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| Abstract: | This study characterizes organic carbon (Corganic) and phosphorus (P) geochemistry in surface sediments of the Sacramento-San Joaquin Delta, California. Sediment cores were
collected from five sites on a sample transect from the edge of the San Francisco Bay eastward to the freshwater Consumnes
River. The top 8 cm of each core were analyzed (in 1-cm intervals) for Corganic, four P fractions, and redox-sensitive trace metals (uranium and manganese). Sedimentary Corganic concentrations and Corganic: P ratios, decreased, while reactive P concentrations increased moving inland in the Delta. The fraction of total P represented
by organic P increased inland, while that of authigenic P was higher bayward than inland reflecting increased diagenetic alteration
of organic matter toward the bayward end of the transect. The redox indicator metals are consistent with decreasing sedimentary
suboxia inland. The distribution of P fractions and C:P ratios, reflect the presence of relatively labile organic matter in
upstream surface sediments. Sediment C and P geochemistry is influenced by site-specific particulate organic matter sources,
the sorptive power of the sedimentary material present, physical forcing, and early diagenetic transformations presumably
driven by Corganic oxidation. |
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