Atmospheric Solid Fallouts as a Source of Hydrophobicity of Urban Soils and Material for Their Formation

Abstract—

In urban conditions, the soil is exposed to a number of adverse factors that have a great impact on its hydrophobic and hydrophilic properties. The water-repellent properties of urban dust and soils were determined with the water drop penetration time (WDPT) test. Hydrophobization of Albic Retisols in the conditions of a megalopolis was modeled, and its rate was estimated. Three dust samples with different values of the WDPT test from 420 to 850 seconds were studied. According to the results of the model experiment, with an increase of solid atmospheric fallout in the Retisols, the level of their hydrophobicity also increases. The rate of the increase depends on the water-repellent properties of the dust. During pollution with the most hydrophobic dust, the maximum hydrophobization of the humus-accumulative soil horizon is achieved upon a 70-year-long impact. For other dust samples, an increase in the time of absorption of a drop was observed up to the maximum period of aerial soil contamination within the model experiment (200 years). Values of the WDPT test for the studied soil horizons ranged from 2.4 s to 1493.5 s for background soil and urban soil forming near a major highway for 90 years, respectively. In the soil of forty-year-old residential area, the value was 237.1 s. The correspondence of the levels of hydrophobicity, the degree of anthropogenic load and the residence time in the urban environment in the model experiment and in the samples of real urban soils indicates that solid atmospheric fallouts are a component of humus-accumulative horizons of urban soils and have a significant impact on their water-repellent properties.