The history of plutonium and cesium-137 contamination of the Ob River delta sediments

A depositional history of particulate organic carbon in a floodplain lake from the lower Ob’ River, Siberia

“…Lakes in this region freeze to depths of 1-1.5 m, which approaches the water depth of this lake, however Sayles et al (1997) examined the top 24 cm of the core and found no evidence that the sediment record had been disturbed by lake ice freezing to the sediment. This sediment profile also shows very little bioturbation or other mixing of sediments (Panteleyev, 1995;Sayles et al, 1997). Collection and processing of sediment cores is described in Panteleyev (1995) and Sayles et al (1997).…”

“…Large amounts of sediment are stored in the floodplains upstream of the river mouth (Ivanov et al, 1995;Meade et al, 2000), which is believed to be a factor in holding sediment export from this river stable since the 1940s Gordeev, 2006). Below Salekhard, which is often considered to mark the mouth of the river, the floodplain continues another 135 km and is up to 20 km wide, with a highly branched channel and many shallow (2-3 m deep) lakes of varying sizes ("sor" lakes) that are connected to the river via narrow channels (Ivanov et al, 1995;Panteleyev, 1995). Below this floodplain, the river enters its delta, which occupies 3250 km 2 , 40% of which consists of islands containing many "sor" lakes, similar to the lower floodplain (Ivanov et al, 1995).…”

“…Sediments in the "sor" lakes derive from both riverine suspended sediments and local bank erosion, with the balance between these two sources controlled by river flow, sediment load, bank properties and ice conditions (Ivanov et al, 1995;Panteleyev, 1995). These lake sediments consist mostly of silts and clays, but can also contain fine plant debris (Ivanov et al, 1995).…”

“…These lake sediments consist mostly of silts and clays, but can also contain fine plant debris (Ivanov et al, 1995). Sedimentation rates in these lakes over the last 300 years averaged 0.2-0.4 cm/year but as much as 10 cm can accumulate during a single, extreme flood event (Ivanov et al, 1995;Panteleyev, 1995).…”

“…This sediment profile also shows very little bioturbation or other mixing of sediments (Panteleyev, 1995;Sayles et al, 1997). Collection and processing of sediment cores is described in Panteleyev (1995) and Sayles et al (1997). Briefly, an 11.5 cm i.d.…”