Assessment of Total Amount of Surface Sediment in Urban Environment Using Data on Solid Matter Content in Snow-Dirt Sludge

Abstract

The aim of the study is the development of a method of quantitative assessment of the total and size-fractionated amount of urban surface deposited sediment. The method utilises the feature of snow cover to accumulate the surface sediment. Snow-dirt sludge formed as a result of snow, and surface deposited sediment mixing on roads and other urban surfaces accumulates sediment over the winter period. In regions with long winter, the snow-dirt sludge lifecycle presents a delayed runoff event. Testing of the method was conducted in Ekaterinburg, Russia, a city situated in a cold region with long winter. Specimens of snow-dirt sludge and urban surface deposited sediment were collected in winter and summer 2017, respectively. Proportions of concentrations of dust, fine sand and coarse fractions in snow-dirt sludge were compared with the same proportion in surface deposited sediment sampled in the summer season. The average concentration of solid phase material in the snow-dirt sludge was 25 ± 9 g/L of melted water. The dust fraction <0.1 mm contributed 44% to the total concentration of the solid phase. The average mass concentrations of coarse fraction, fine sand and dust in summer samples of surface deposited sediment were in proportion 31%:31%:38%, respectively. A total amount of urban surface deposited sediment of approximately 320,000 tons (3.2 kg/m2 per unit residential area) was estimated in Ekaterinburg, of which about 120,000 tons was the dust fraction. Obtained quantitative assessments of sediment deposition on urban surfaces characterise the sedimentation as important environmental process in contemporary urban areas.