Auxiliary Material Submission for Paper 2012GB004339
River discharge influences on particulate organic carbon age structure in the Mississippi/Atchafalaya River System.
Rosenheim, Roe, Roberts, Kolker, Allison, and Johannesson
Introduction
The auxiliary materials for this manuscript include one figure (2012GB004339-fs01.eps) and one table (2012GB004339-ts01.txt format).
Figure 2012GB004339-fs01.eps outlines the relationship between the third temperature interval’s radiocarbon and stable carbon isotope ratio and the calculated bulk isotope ratios of each sample. These linear relationships are so far unique to the MARS suspended load data set. The linear relationship between calculated bulk radiocarbon depletion (equation 4 in the manuscript) and the radiocarbon depletion of the third temperature interval (Table 2012GB004339-ts01.txt) lies on a 1:1 line, making it useful to estimate a bulk radiocarbon depletion value for the sample where the samples have been lost during preparation and where no more sediment exists. Such cases occurred in the intermediate depth sample from the Mississippi River during 2009 sampling (Figures 3d, 5f) and in the surface sample of the Atchafalaya channel (Figure 5a). The simple approximation, which focuses on measured data without manipulation, is more accurate for radiocarbon age (which is isotope-corrected for fractionation) than for stable isotope composition. In this experiment, temperature intervals were determined by sample size for radiocarbon analysis due to no prior knowledge of POC age structure in the MARS. As a result, the third temperature interval for each sample spanned a slightly different range in temperatures. Thus, any correlations would be expected to incorporate a degree of noise. The variability does not preclude the use of this approximation for radiocarbon age, although use for stable carbon isotope composition cannot be advised for this data set.
Table 2012GB004339-ts01.txt contains data for all samples analyzed.
1.2012GB004339-fs01.eps Correlation between the geometric mean (eq. 1) and third interval of stable carbon isotope data (top) and radiocarbon dates (bottom) for samples analyzed in this project.
2. 2012GB004339-fs01.txt Data table for all ramped pyrolysis samples analyzed.
2.1 Column “River-Year”, River abbreviation (MR – Mississippi River, AR – Atchafalaya River, MRO – Mississippi River Outlet, ARO – Atchafalaya River Outlet) hyphenated with sampling year.
2.2 Column “Depth Interval”, Relative depth of sampling, Surface (0.1D), Intermediate (Inter., 0.5D), or Bottom (0.9D), where D was the depth of the sample site.
2.3 Column “Collection Year”, Year of sample collection
2.4 Column “Analysis Year”, Year of radiocarbon analysis
2.5 Column “High Temperature Interval”, Temperature in degrees Celsius of the high temperature end of the temperature interval over which CO2 from the POC sample was integrated into a single sample.
2.6 Column “mmol CO2”, Quantity of CO2 in sample, measured in micromoles
2.7 Column “fM”, Fraction modern corrected for stable carbon isotope composition
2.8 Column “1s fM”, 1-sigma uncertainty on fM
2.9 Column “d13C”, stable carbon isotope ratio relative to PDB
2.10 Column “1s d13C”, analytical uncertainty in stable carbon isotope ratio
2.11 Column “d14C”, radiocarbon depletion relative to international standard, uncorrected for age [Stuiver and Polach, 1977]
2.12 Column “1s d14C”, analytical uncertainty on radiocarbon depletion, calculated from uncertainty on fM
2.13 Column “D14C”, radiocarbon depletion relative to international standard, corrected for time between sampling and analysis [Stuiver and Polach, 1977]
2.14 Column “1s D14C”, analytical uncertainty on radiocarbon depletion, calculated from uncertainty on fM