The Impact of Oil Industrial Operations on the Contamination of Soil Ecosystem by Harmful Chemicals

Book DOI: 10.21467/abstracts.93 released into atmosphere as a result of fossil fuel burning spread to wide distances. The most dangerous for human helth PAHs – bezo(a) pyren is mainly found in exhaust gases. In atmosphere, PAHs form suspended particles that can spread to large territories and transform to other pollutants through photochemical reactions. Further, these pollutants return to the earth surface and accumulate in soils and bottom sediments of surface waters. As it was mentioned above, crude oil have certain amount of trace elements. From the ecological viewpoint, they are divided into two groups: toxic and non-toxic. Among them Si, Fe, Al, Mn, Ca, Mg and P are low toxic microelements. V, Ni, Co, Pb, Cu, As, Hg and Zn have negative impact on biocenosis at high concentrations. About 10-3 % toxic metals and halogens are found in the asphaltene-tar fraction of oils. Some of metals are in the form of salts of organic acids, and others in the form of chelat complexes. Produced water is most hazardous natural pollutant of the environment. They contain various ions, oil and dissolved gases, such as CO2 and H2S. Both the oil polluted rocks and produced water cause pollution of the ecosystem components, first of all soil cover. The rocks obtained from oil extraction may constitute of 1-5% even 10% hydrocarbons. Depending on the pollution level, they can form complex substances with Fe and Al ions and various soluble complexes thus leading to the depletion of important minerals in soil. Drilling solutions and drill cuttings are by volume the largest anthropogenic waste formed when exploring and development of oil fields. These discharges include water-oil emulsions, corrosion inhibitors, surface active agents, Ca (NO3)2, Mg (NO3)2, HCl, KCl, NaON, NH4ON, various polymers and mechanical mixtures, etc. Light fractions of hydrocarbons easily migrate to deeper sections of soil, and therefore, increased content of heavy asphaltene-tar fraction accumulate in the upper layers. The asphaltene-tar fraction of oil is toxic and difficult degradable. This fraction contain the most toxic environmental pollutants – heavy metals. Potential threat of heavy metals to ecosystem components, especially to human health, is associated with two factors: high toxic impact at low concentrations and bioaccumulation abilities. Many of them like Hg, Pb, Cd, Cr, Zn and Cu can be very toxic to the ecosystem. Heavy metals are mainly gathered in soils and bottom sediments. Concentrated in soils heavy metals can be adsorbed and accumulated in different parts of plants through root system. One of the major global problems of the present days – acid rains can wash heavy metals from soil rocks into lakes, rivers and bays. Most of heavy metals disrupt enzyme function forming bonds with sulfur groups in enzyme and may eventually kill living organisms. Due to their migration and accumulation in the environment, most heavy metals can easily enter the food chain and create serious threats to human health. The negative effects of heavy metal contamination are viewed as global concern. The results of researches devoted to the impact of oil contamination on the soil microbiological peculiarities and plants quality have shown that the cereals cultivated in these soils contain increased quantities of Pb, Cd, Fe, Ni, Zn and Cu. High concentrations of heavy metals in soil can damage fertility and productivity of the farmlands. It was revealed that high concentration of heavy metals in the oil polluted soils not only affects the plant quality, and also reduces the number and activity of microbes. The results confirmed that the number of heterotrophic bacteria was 89% lower in oil polluted soils compared to unpolluted soils. Taking into consideration all the above stated, it can be concluded that the activities associated with the development of hydrocarbon fields lead to the release of large amount of chemicals to ecosystem causing serious problems including contamination and degradation of soil resources. Therefore, it is necessary to treat the waste formed during oil-gas operations properly prior to their discharge into the environment. The great attention should be paid to the development of contaminants minimization and pollution preventing measures to ensure ecological safety throughout the industrial territories.