Total organic material and grain size data in marine sediment samples taken as part of the Davis Sewage Treatment Project, summer 2009/10

Brief description

Total Organic Carbon
A 2 g homogenised wet sediment sub-sample from each core was weighed into a pre-combusted crucible and dried at 105 degrees C. The dried sample was reweighed before being analysed for total carbon by mass loss on ignition at 550 degrees C, the sample was placed in the muffle furnace for 4 hours.
Samples 56698, 57062, 56837, 57058, and 580792 were analysed in triplicate to assess the reproducibility of the analytical procedure. (Total number of analyses was 117).

- TOC
- For the 107 samples:
- Mean and SD: 3 plus or minus 4 % DMB, range: 0.16-15 %, n=107
- Considering the mean values for the 27 site locations:
- Range: 0.33-14 % DMB, mean and SD: 3.3 plus or minus 3.7 % DMB, n=27
- Analytical uncertainty
- Analytical precision: 5 samples analysed in triplicate:
- RSD = 6 plus or minus 5% range 1-11%, n=5
- Site heterogeneity: reproducibility (RSD) of mean data from site replicate samples was 26% (mean, SD 15%, range 10-57%, n=27)
- From the limited data on reproducibility summarised above, it can be concluded that site heterogeneity contributes most to the uncertainty of the TOC data for the site locations.

- DMF
- For the 107 samples:
- Mean and SD: 0.57 plus or minus 0.23 %, range: 0.09-0.85, n=107
- Considering the mean values for the 27 site locations:
- Range:0.17-0.83, mean and SD: 0.57 plus or minus 0.22, n=27
- Analytical uncertainty
- Analytical precision: 5 samples analysed in triplicate:
- RSD = 2 plus or minus 2% range 0.8-5%, n=5
- Site heterogeneity: reproducibility (RSD) of mean data from site replicate samples (mostly quadruplicates) was 10% (mean, SD 10%, range 1-37%, n=27)
- From the limited data on reproducibility summarised above, it can be concluded that site heterogeneity contributes most to the uncertainty of the DMF data for the site locations.

Collection of sediment cores
Sediment for grain size and various chemical analysis were sampled using a core of PVC tubing (15cm long x 5cm diameter) pushed 10cm into the sediment. These cores were kept upright at all times to ensure the stratigraphy remained intact and frozen in the core tube at -20 degrees C.

Grain size analysis
The outer 5 mm edge of the core was removed with a scalpel blade and placed in a clean, dried preweighed beaker. The sample was weighed and placed in an oven at 45 degrees C to dry. Once dry the sample was reweighed and then sieved through a 2 mm sieve, any residual sediment in the beaker was weighed and the weight recorded. The less than 2 mm fraction and the greater than 2 mm fraction were separately collected and weighed. A 5 g sample of the less than 2 mm fraction was taken for grain size analysis which was carried out using the Mastersizer 2000 Particle Size Analyser by Associate Professor Damian Gore at the Department of Physical Geography, Macquarie University, Sydney.