Oil products in gully alluvium in the territory of Saratov: seasonal dynamics and geoecological assessment

Oil products are one of the most typical pollutants of the urban environment. With surface runoff from the urbanized territory, oil products enter the gullies and are transported by watercourses. The research analyzes the seasonal dynamics and conducts a geoecological assessment of the content of oil products in the alluvium of the gullies in the city of Saratov. The urban area has a high erosional dissection, the runoff of the city ravines is directed to the Volgograd Reservoir. The Volgograd Reservoir closes the cascade of reservoirs on the Volga River, serves as a source of drinking water supply and an object of recreation, and is of fishery importance. Samples of bottom sediments were collected from the source to the mouths of the gullies from the surface layer up to 2 cm deep. 45 samples were collected from thalwegs of 11 gullies during the minimum runoff in August-September 2022 and after snowmelt in April 2023. Laboratory analysis of the content of oil products was performed by the gravimetric method. The features of land use and technogenic load within each catchment area are considered. It was found that in one half of the samples the higher content of oil products was in spring, in the other - in summer. Almost half of the samples during both seasons are characterized as very dirty. The most polluted alluvium is in the gullies in the southern part of Saratov, where large industrial enterprises are located.