Aliphatic and aromatic hydrocarbons in coastal Caspian Sea sediments.

Amounts of heavy metal elements (Zn, Cd, Pb, Cu, Ni, Co, Mn, and Fe) in surficial sediments at four regions (coastline, estuaries, rivers discharging into the sea, and Gorgan Bay) along the southern coastline of the Caspian Sea were investigated in summer 2015. Collected data was applied to appraise the sediment contamination degree and the origin of pollutants based on the Geo-accumulation Index. Pollution status was assessed via the Enrichment Factor (EF) and the Potential Ecological Risk Index (PERI, the Hakanson index). Heavy metal contents in sediments in mg g−1 dw varied from 3000 to 39,500 for Fe, 166.66 to 2000 for Mn, 11 to 4198 for Zn, not detected (ND) to 822.83 for Pb, ND to 40.66 for Cd, 6.16 to 37.16 for Cu, 11.66 to 69 for Ni, and 6.33 to 33.00 for Co. Higher amounts of Cd, Pb, Cu, Mn, and Fe were determined in rivers discharging sediments into the sea. In Gorgan Bay, Zn, Ni, and Co were highest. Greater potential ecological risk levels were detected along the coastline as well as rivers discharging into the sea. Among heavy metals considered, Zn and Cd had the highest enrichment factors. The Geo-accumulation Index proved that the investigated region could be classified as Zn- and Cd-polluted area.

Distribution pattern and pollution status by analysis of selected heavy metal amounts in coastal sediments from the southern Caspian Sea.

The microbial community response to petroleum seepage was investigated in a whole round sediment core (16 cm length) collected nearby natural hydrocarbon seepage structures in the Caspian Sea, using a newly developed Sediment-Oil-Flow-Through (SOFT) system. Distinct redox zones established and migrated vertically in the core during the 190 days-long simulated petroleum seepage. Methanogenic petroleum degradation was indicated by an increase in methane concentration from 8 µM in an untreated core compared to 2300 µM in the lower sulfate-free zone of the SOFT core at the end of the experiment, accompanied by a respective decrease in the δ13C signal of methane from -33.7‰ to -49.5‰. The involvement of methanogens in petroleum degradation was further confirmed by methane production in enrichment cultures from SOFT sediment after the addition of hexadecane, methylnapthalene, toluene, and ethybenzene. Petroleum degradation coupled to sulfate reduction was indicated by the increase of integrated sulfate reduction from 2.8 SO42- m-2 day -1 in untreated cores to 5.7 mmol SO42- m-2 day -1 in the SOFT core at the end of the experiment, accompanied by a respective accumulation of sulfide from 30 to 447 µM. Volatile hydrocarbons (C2 to C6 n-alkanes) passed through the methanogenic zone mostly unchanged and were depleted within the sulfate-reducing zone. The amount of non-volatile n-alkanes (C10 to C38) decreased step-wise towards the top of the sediment core and a preferential degradation of shorter (C30) was seen during the seepage. This study illustrates, to the best of our knowledge, for the first time the development of methanogenic petroleum degradation and the succession of benthic microbial processes during petroleum passage in a whole round sediment core.

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Hydrocarbon Degradation in Caspian Sea Sediment Cores Subjected to Simulated Petroleum Seepage in a Newly Designed Sediment-Oil-Flow-Through System

The water produced at the Amal oil field in Libya is directly stored for evaporation in in-ground-pits. As there are a large number of oil production wells, there is a risk of environmental pollution because of the waste water’s eventual penetration into subsoil and surface waterways. From a technical point of view, the existing system of reservoir water disposal into storage pits will not be adequate to meet the increasing water production. Besides, the discharge of produced water without previous treatment is ecologically unacceptable. In this paper, a modern concept of produced water preparation is proposed, and the method of its disposal defined, applying an integrated approach to solving this problem, including technological, economic and environmental aspects. Produced water preparation in an oil field in Libya was chosen for the proposed implementation of an option with the lowest operating costs (storage tanks and liquid hydrophobic filter tank).

An oilfield in Libya: A new model to enhance waste water disposal

The presence of heavy metal and organic pollutants in wastewater effluents, flue gases, and even solid wastes from petrochemical industries renders improper discharges liable to posing threats to the ecological environment and human health. It is beneficial for pollution control to find out the regional distribution of contaminated sites. This study explored the relationship between the petrochemical contaminated areas and natural, socio-economic, and traffic factors. Ten indicators were selected as input variables, and the MaxEnt model was conducted to identify the potentially contaminated areas. Moreover, among these 10 variables, the factors that have the great impact on the results were determined according to the contribution of variables. The results showed that the MaxEnt model performed well with AUC of 0.981 ± 0.004, and 90% of the measured contaminated sites was located in areas with medium and high probability of contamination in the prediction results. The map of potentially contaminated areas indicated that the areas with high probability of contamination were distributed in Yangtze River Delta, Beijing, Tianjin, southern Guangdong, Fujian coastal areas, central Hubei and northeast Hunan, central Sichuan, and southwest Chongqing. The responses of variables presented that high probability of petrochemical contamination tended to appear in cities with developed economy, dense population, and convenient transportation. This study presents a novel way to identify the potentially contaminated areas for petrochemical sites and provides a theoretical basis to formulate future management strategies. 

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Azer G. Orudjev

Papers

Optimization of oil-containing wastewater treatment processes