Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

Location:  
Folly Island and Marsh, South Carolina, 32.68 N, 79.95 W
Daniel Island creek/marsh, South Carolina 32.89 N, 79.9 W

Sampling and analytical procedures:

Water samples were poured through PCV columns containing 15 grams of manganese impregnated fiber. The columns were returned to the lab (collection times were recorded to account for decay before counting) where the fiber was rinsed with deionized water and dried with compressed air to the point of no excess water expulsion. The samples were then weighed so that constant water content could be achieved between counting.

The RaDeCC counters had previously been flushed with air for a minimum of 15 minutes. Once the sample was attached, the system was flushed with helium and then closed trapping the helium. The samples were then counted three different times. The first count was directly after being rinsed and dried. The second count happened three days later. The third count happens approximately 3 weeks later, the sample is counted for 6 hours. The level of moisture is checked between each counting and adjusted by weight. The collection and counting method is adapted from Moore (2007) and Moore and Arnold (1996).

After the three counts on the RaDeCC the fibers are leached following an adapted method outlined by Moore et al (1985). In brief, the fibers are heated in a mixture of hydrochloric acid and hydroxylamine hydrochloride until pale. The fibers are then filtered and rinsed with hydrochloric acid and water. The leachate is then treated with barium nitrate (saturated) and 1 molar sodium hydrogen sulfate (or 1 molar sodium sulfate) and stirred to form a precipitate. After settling, the precipitate is centrifuged with excess liquid removed. The precipitate is then aged 2 weeks and counted using the WeGe.

For the determination of NOX, the method from Schnetger, Bernhard & Lehners, Carola. (2014) was used. In brief, the sample is collected in a glass vial and transported to the lab. To analyze nitrite a ratio of 10:1 sample to reagent (1:1 of NEED 0.004 M and Sulfanilamide 0.12 M) is incubated at 45C for 30 minutes or 60 minutes at room temperature. The absorbance is then measured at 540 nm. Total nitrogen oxide analysis is then performed using a 1:1.5 ratio of sample to reagent ( 5:1:1 of VCl₃ 0.05 M: NEED 0.004 M: Sulfanilamide 0.12 M) where the sample is incubated for 60 minutes at 45C, then absorbance is measured at 540 nm. A correction is made to account for the amount of NO₂ lost by conversion to NO to obtain a final corrected value for NOX total nitrogen oxides. 

Data from both the RaDeCC and WeGe are in text files. The relevant numbers from the raw data are transferred to Excel spreadsheets where calculations (including decay, coincidence counts, error) are performed to obtain final results.

Excel version: Microsoft® Excel® for Microsoft 365 MSO (Version 2111 Build 16.0.14701.20254) 64-bit  .

BCO-DMO Data Manager Processing Notes:
* First sheet named "Water" imported from Excel file ALLDATA_ToSubmitWater.xlsx into the BCO-DMO data system.
* Parameters (column names) renamed to comply with BCO-DMO naming conventions. See https://www.bco-dmo.org/page/bco-dmo-data-processing-conventions
* Date format converted to ISO 8601 date format yyyy-mm-dd
* There were a few time formats that had extra seconds as :00, these were stripped of to match the time format hh:mm of the rest of the dataset. 
* DateTime in UTC converted to ISO 8601 format yyyy-mm-ddTHH:MMZ
* Latitude and longitude rounded to five decimal places (from 8).
* Longitude made negative since West is negative in decimal degrees.
* The following columns rounded to two decimal places (guidance from submitter). exRa224_dpm_per_L, Ra223 dpm_per_L ,Th228 dpm_per_L , Ra226_dpm, Ra228_dpm, Ra226_dpm_L, Ra228_dpm_per_L
* column names NOX and NOX_Std_dev changed to Nitrate_and_Nitrite and Nitrate_and_Nitrite_std_dev for clarity Columns also rounded to one decimal place. (guidance from submitter).  

NSF Award Abstract:
Tidal marshes are critical junctions between marine and terrestrial chemical processes. The chemical and physical processes that tidal marsh sediments undergo determine the nature of the transformation and accumulation of particulate organic carbon (POC) at the marine to terrestrial interface. Physical transport of pore water through marsh sediments greatly influences the availability of carbon and nutrients that can undergo transformative reactions at the marine to terrestrial interface. Past studies have shown that there is a discrepancy between predicted rates of pore water flow and calculated estimates from tracer studies. Because this flow is crucial to the chemistry of sediment at the terrestrial to marine interface, which is the first junction of the chemical species exported to the ocean, it is important to explain the discrepancy between expected rates of flow and observed rates. This study will use a known tracer method based on natural isotopic ratios (224Radon/228Thorium) and will develop a new method (223Radon/ 227Actinium) to evaluate the export of POC due to pore water flow in tidal marsh sediments, which will have much broader impacts to the overall marine carbon budget. Results from this work will also be integrated into workshops that will educate students and teachers from outside of oceanography about oceanographic carbon and climate research. Presentations will also be developed in collaboration with the South Carolina State Museum as part of the Science Café series. Additionally, one graduate student and one undergraduate student will be supported by this funding.

Predicted advection rates of pore water in very fine-grained tidal marsh sediments have been shown to significantly differ from rates calculated using tracer studies. Because tidal marshes are a crucial chemical link at the marine terrestrial interface, and advection has a significant impact on the availability of chemical species to undergo diagenetic reactions at this interface, it is of significant importance to evaluate this discrepancy. Export of particulate organic carbon (POC) and dissolved organic carbon (DIC), in particular, are of interest, due to the impact on microbial communities within sediments. This research aims to validate the method of 224Ra/228Th disequilibrium to calculate pore water exchange rates. Previous studies using this method have provided evidence for more rapid pore water exchange than would generally be expected in such fine-grained sediments, which are less permeable than coarser grained sediment. Additionally, this research will attempt to develop the disequilibrium method for 223Ra/227Ac. The researchers will evaluate the impact of advection rates on the export of chemical species in salt marshes.