The Organic Component of Particulate Matter in Small Streams of the Northern Yenisei Region During the Summer-Autumn Period

Abstract

A quantitative assessment is made of suspended sediment load, including particulate organic matter and organic carbon, in 2014 for the small streams of the Northern Yenisei region, in the taiga–tundra transition zone (near the city of Igarka, Krasnoyarsk krai). It was found that the suspended sediment concentration (SSC) of the streams under investigation fluctuated between 2 and 18 mg/L during the summer–autumn low-water period of 2014. The proportion of dissolved organic matter (DOM) in the total sediment yield varied from 16.4% to 74.1%, depending on landscape-geomorphological conditions for suspended sediment formation: it is higher for streams with tundra catchments and lower on forest watersheds underlain by sandy and clayey loams. The DOM content varies from catchment to catchment from 1.63 to 2.42 mg/L, and the mean concentration of dissolved organic carbon (DOC) is estimated at 0.73 to 1.09 mg C/L. It is shown that the local channel transformations serve as the main source of POM and DOC input to the water of two out of three streams under study. Surface runoff or fast subsurface flow in the organic soil horizon is the external source of DOM input to the water of the third stream during flooding. Regional empirical dependencies were obtained, which correlate the water discharge, total SSC and the proportion of DOM are obtained. The long-term proportion of DOM in the annual suspended sediment flow of the Graviika river makes up 25% and DOC, 11%, or, in absolute values, 406 and 183 t/year, and in units of layer 1.26 and 0.57 t/km², respectively.