The use of chemical dispersants is one of the most widely used methods for responding to oil spills. The most important characteristic of dispersants is their effectiveness. The dispersant effectiveness is a measure of how well the dispersant breaks up and stabilizes the oil into the water column. In this paper, we studied the dispersing ability of three proprietary dispersants with respect to light and heavy crude oils of Usinsk and Nagornoye fields with a density of 0.816 g/cm3 and 0.896 g/cm3, respectively. The dispersant effectiveness was determined using a Baffled Flask Test; dispersant was applied to the oil slick, mixed, and the concentration of oil in a sample taken from the water column was measured using UV-Visible spectrophotometry. A modification of the standard technique is proposed to minimize the error of the method for the heavy crude oil by eliminating the error associated with inaccuracy of dosing. For this purpose, oil of the Nagornoye field was added to the tested systems not “by volume”, but “by weight”. It was provided better convergence of the experimental results. The standard deviation in the case of dosing of oil “by volume” exceeded 10% and varied from 11.87% to 13.59%. The introduction of oil “by weight” was much lower and varied from 5.66% to 6.30%. Studied dispersants have a higher dispersing ability for the less dense oil of the Usinsk field.
The experiments on mobilization of soil organic matter during soil washing with ultrafresh water against the background of salinity pulsing were designed and performed. Unpolluted soil and the soil artificially polluted with copper(II) were used in experiments, namely, clay loamy typical chernozem (Haplic Chernozem) of the Alekhin Central Chernozemic Nature Reserve (Kursk oblast, Russia; 51°34.207 N, 36°05.444 E) and sandy loamy soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) from the Domodedovo district of Moscow oblast, Russia (55°17.683 N, 37°50.045 E). Soil samples were taken from the upper humus-accumulative (A1) horizon (5–15 cm). A drastic change in the composition of washing solution from fresh water to 0.1 M NaCl solution and back led to destruction of soil aggregates under the impact of osmotic pressure. Soddy-podzolic soil proved to be more resistant to destruction as compared with typical chernozem. Copper(II) was leached off from artificially contaminated samples of soddy-podzolic soil with the flow of dissolved organic matter, whereas copper leaching from typical chernozem was associated with the destruction of aggregates and release of intraaggregate organic matter. It is argued that copper (II) migration models should take into account the amount of dissolved organic matter for soddy-podzolic soil and the content of aromatic fragments in the organic matter for typical chernozem. A conceptual model of the Cu(II) leaching from contaminated soddy-podzolic soil and typical chernozem in the course of soil washing with fresh water against the background of salinity pulsing and the destruction of soil structure is constructed.
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