²¹⁰Pb and ¹³⁷Cs in margin sediments of the Arctic Ocean: Controls on boundary scavenging

Abstract

210Pb and 137Cs were measured in 25 sediment cores collected during the International Polar Year from a transect spanning the North American Arctic margin, from the North Bering Sea to Baffin Bay/Davis Strait. Profiles and inventories of the radioisotopes were used to determine sediment mixing and accumulation at each site and to assess the intensity of scavenging and burial. Sediment accumulation rates derived from 210Pb and validated using 137Cs are between ≤0.04 and 0.23 g cm−2 yr−1. 210Pb cannot be used to derive sedimentation rates for vigorously biomixed sediments from the North Bering‐Chukchi shelf. Elevated 137Cs activities and inventories in recently deposited sediments imply delayed inputs of particle‐associated 137Cs to the sediments, likely transported from the watershed to the coast and subsequently redistributed to shelf/slope sediments. Inventories of 210Pbex in all cores meet or exceed the estimated supply of 210Pbex from atmospheric deposition and decay of 226Ra in the water column. This implies that in contrast to the deep Arctic Ocean basin, there is a sufficient supply of suspended particulates along the North American Arctic margin to scavenge the supply of 210Pbex. 210Pbex inventories in sediments are up to 21‐fold greater than the in situ supply at some sites. Large inventories of 210Pbex in sediments along the North Bering‐Chukchi shelf result primarily from focusing, while those along the north Chukchi slope (Barrow Canyon) and in Baffin Bay/Davis Strait reflect strong boundary scavenging, likely supported by lateral exchanges with deep/interior Atlantic‐origin waters.

Persistent organic pollutants in ocean sediments from the North Pacific to the Arctic Ocean

“…[] reported no apparent corelationships between PCB concentrations and sediment properties including TOC. While the distribution of ΣPCBs in Hudson Bay sediments (a shallow water region) only partly reflect sediment texture (Φ < 63 μm, r 2 = 0.49) and organic carbon content ( r 2 = 0.55) [ Kuzyk et al ., ]. In summary, this would indicate complex processing of organic contaminants following their input––principally deposition from the atmosphere for remote pelagic environments––and final accumulation with benthic particulate matter.…”

Sources and accumulation of sediment and particulate organic carbon in a subarctic fjard estuary:210Pb,137Cs, and δ13C records from Lake Melville, Labrador

“…Sedimentation velocity ( s , cm a −1 ), the rate at which sediment accumulates on the seafloor, was estimated by using a onedimensional two-layer advection-diffusion model that accounts for both biomixing and compaction with depth (Lavelle et al 1985;Kuzyk et al 2013;Kuzyk et al 2015):…”

“…On the basis of historical 137 Cs fallout and similar temporal variations of 137 Cs atmospheric fallout outlined by Monetti (1996) and Wright et al (1999), an input function was developed and compared with measured values of 137 Cs (cf. Kuzyk et al 2013). Sediment velocities were adjusted, within 95% confidence limits, to give the best fits for both 210 Pb ex and 137 Cs.…”

“…Following methodology developed by Kuzyk et al (2013), we used the 210 Pb and 137 Cs inventories in tandem (Fig. 9) to evaluate the relative importance of focusing (or lateral transport) and scavenging, driven by vertical particle flux (e.g., from primary production in surface waters).…”

Influence of Sedimentation Rate on the Metal Contamination in Sediments of Bohai Bay, China

“…In contrast, 137 Cs is an artificial radionuclide (half-life = 30.2 years), which was released into the environment for the first time through atmospheric nuclear weapon tests conducted in the 1950s-1960s. This radionuclide is often used together with 210 Pb to validate the geochronology of the sediment (Kuzyk et al 2013).…”