Dissolved organic carbon content estimation in the Lena River Delta

An estimation of the dissolved organic carbon formation and runoff to the Arctic Ocean by rivers is one of the important aims of the permafrost hydrology. The source of the historical data about organic carbon is the values of the permanganate oxidation (PO) from Roshydromet polar stations. According to historical data a mean PO value for the Lena River for 1960-1975 in Kachyug station (upstream of the river) is 9.2 mg/l, for Kusur station (downstream, near delta) – 10,9 mg/l. PO is the closest to the modern useful parameter DOC (dissolved organic concentration) but not equal. There are special local coefficients of conversation, we used an average value (DOC=0.5*PO). Based on recalculation mean annual DOC discharge for Lena, Kusur could be 91 kg/s. In the Lena River delta on Samoilovsky research station measurements of different components of carbon cycle were carried out for several years as a part of Russian-German expeditions. In August of 2012 and in July 2013 investigations at the catchment of the Fish Lake were carried out. Fish Lake is a thermokarst-polygonal lake, and the landscape of its catchment is typical for the Lena River delta. These measurements were done in order to study the income of DOC to the lake from an active layer of catchment. For this purpose the depth of the active layer and soil moisture were measured. In August 2012 the depth of the active layer was 20 to 60 cm, 20-30 cm on polygon rims and 30-60 cm in polygon centers and near the lake. For twenty days an increase of the depth ranged from 10 to 15%. Soil moisture value was 28-72%. In July 2013 the depth of active layer was from 17 to 48 cm, an increase for month was from 0 to 10%. Soil moisture value was 18-90%. In 2012 DOC concentrations in pore water ranged from 8 to 51 mg/l, and average DOC concentration in the catchment Fish Lake was 25 mg/l. Highest values were in the dry centers of the polygons. In the water objects like the polygon ponds and the Fish Lake DOC concentration was 5