Seasonally varied cross-shelf transport of sedimentary particles in the river-dominated margin sea elucidated by radionuclides
Description
Radionuclides data (Bq kg-1) and mineral component in the ECS surface sediments at different seasons
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Steps to reproduce
One hundred sixty-two surface sediments (0-1 cm) were collected within the ECS during the R/V ‘‘Shiyan 3” Cruise in May of 2011, R/V ‘‘Beidou’’ Cruise in August of 2011, R/V “Runjiang 1” Cruise in February of 2012, R/V “Beidou” Cruise in May of 2013, R/V “Dongfanghong 2” Cruise in August of 2013, and R/V “Beidou” Cruise in October of 2013, using a box corer. The sampled sediments were stored in resealable plastic bags at 4 °C for subsequent laboratory analysis. Some of the data acquired from samples collected in May and August of 2011 have been reported in our previous publication (Wang et al., 2016), which are shown in red in Figure 1. The 137Cs data from samples collected in August of 2013 were also reported in our previous study (Zhang et al., 2019). An aliquot of dry sediment was used to determine the grain size using a laser particle analyzer (LS100Q, Beckman, USA). Before analysis, wet sediment subsamples were oven-dried at 60°C to constant weight to remove pore water, then homogenized and ground to a fine, uniform powder with an agate mortar and pestle. About 60-120 g dry sample was accurately weighed into a cylindrical plastic container (70 mm internal diameter × 70 mm height), with all container seams hermetically sealed with paraffin wax to prevent escape of 222Rn, the gaseous decay product of ²²⁶Ra. Sealed samples were stored at room temperature for at least 20 days to establish a secular equilibrium between 226Ra and its progeny. The method for the measurement of 226Ra, 210Pb, 137Cs, and 7Be using High-Purity Germanium γ-ray spectrometry (Canberra Be3830) was given in our earlier published work (Wang et al., 2016). Each sample was counted for a minimum of 24 hours to achieve sufficient counting statistics, with method detection limits calculated at the 95% confidence interval for each target nuclide. The activity of 7Be was quantified via its characteristic 477.6 keV gamma emission (branching ratio 10.5%), 137Cs via its 661.6 keV photopeak (branching ratio 85%), and total 210Pb via its 46.5 keV gamma peak (branching ratio 4.25%). The activity of 226Ra was determined as the average of activities derived from the 351.9 keV peak of 214Pb (branching ratio 37.6%) and the 609.3 keV peak of 214Bi (branching ratio 46.1%), measured after confirmation of secular equilibrium. 210Pbex was calculated as the difference between the total 210Pb activity and the equilibrium 226Ra activity in the same sample. The International Atomic Energy Agency (IAEA) standard material (IAEA-RGU-1 and IAEA-RGTh-1) was utilized to calibrate the efficiency of the gamma counting system. All reported radionuclide activities were corrected for radioactive decay from the time of field sample collection to the midpoint of the gamma counting interval, using the accepted decay constants for each nuclide: 7Be, 137Csand 210Pb.
Institutions
- East China Normal UniversityShanghai, Shanghai