Arctic surface waters are strongly enriched in 228Ra. Offshore, the 228Ra distribution follows the distribution of freshwater with a hypothetical freshwater endmember, but the actual low-salinity distribution of 228Ra shows that a large part of 228Ra is supplied by the wide shelves rather than by rivers. Few data are available in the low-salinity range and close to the shore of the Russian Arctic. To my knowledge no data is available on 224Ra near the Siberian coast. Aug/Sept 2013 I had the opportunity to sample for Radium isotopes on several approx. 100-km long transects perpendicular to the coast of the Lena delta. The shallow (approx. 25m) sea is extremely stratified, salinity (hydrography measured by Murmansk Marine Biological Institute) ranging from locally close to 0 at the surface to 30 ‰ at depth, often in several discrete steps. Close to the shore the turbidity is very high. The strongest source of 224Ra was found in the turbid coastal waters of intermediate salinity while 228Ra had its major source at higher salinities. I will discuss the potential use of these tracers for studying mixing in the coastal zone and possible inputs of groundwaters in this largely permafrost-dominated region.