Dataset: Salinity, radium/thorium radionuclide, and nitrogen oxide concentration measurements from surface and porewater samples collected in coastal South Carolina from 2017 to 2019

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.