The Impact of Petrochemical Enterprises on the Soil Cover in Samara Oblast

We studied the state of the soil cover in sanitary protection zones of two large oil refineries in Samara region (at distances up to 1000 m from the refineries) using a combination of chemical and microbiological test to identify priority pollutants. The following parameters were used for the sanitary-chemical assessment of soils: soil pH and the concentrations of ammonium, nitrates, mercury, anion-active surface-active agents, phenols, petroleum products, arsenic, copper, lead, zinc, cadmium, nickel, cobalt, and benzo[a]pyrene. The sanitary-bacteriological tests included determination of the coliform index, index of lactose-positive Bacillus coli, enterococcus index, total microbial count, and the quantity of saprophytes, actinomycetes, and enteric pathogens. Petroleum products, benzo[a]pyrene, arsenic, and some heavy metals (cadmium and nickel) were the priority pollutants of sanitary protection zones of oil refineries. The results of microbiological tests demonstrated that the soil self-purification processes in the studied areas are very slow. It was found that the content of hydrocarbons in soils depends on the distance of sampling sites from large highways within sanitary protection zones. The contents of most of heavy metals and arsenic in soils were higher near large highways and parking areas in comparison with those at the sites near small streets with low traffic. The results obtained attest to the unsatisfactory state of the soil cover in the examined sanitary protection zones. These zones require further monitoring and certain remediation actions.