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The sorption capacity of selected heavy metals (Cd, Pb, Cu, Cr) to five Estonian soils was evaluated using spiked subsoil samples in laboratory experiments. The experimental sorption data fitted well to the linear Freundlich isotherm. The sorption of metals in subsoil depended on the soil type, e.g., mineral composition. The results indicate that the content of quartz and carbonates is important in affecting the metal sorption capacity of subsoil. On the basis of our data the possibility of penetration in depth and accumulation of mobile metals was evaluated. It was concluded that increase in dissolved Cd and accumulation of other metals in the subsoil of Podzol is expected. The accumulation of Pb could be the main process for soils with a high amount of dolomite.

Oil shale ash (OSA) from the circulating fluidized bed (CFB) boiler was granulated and used as a sorbent for the removal of phenols from shale oil wastewater. The method for preparation of the sorbent involved washing of the ash, mixing with clay, gelling the mixture with sodium alginate solution, solidifying the granules in barium chloride solution, drying and calcination of the granules and modifying with a surfactant -- hexadecyltrimethylammonium bromide (CTAB). The sorbent was characterized by specific surface area (BETN2), X-ray diffraction (XRD) and 29Si Magic Angle Spinning- Nuclear Magnetic Resonance (MAS-NMR) analysis. Batch adsorption experiments were conducted to determine the phenol adsorption isotherm at 20 °C and removal of water-soluble phenols from phenolic shale oil processing wastewater. Removal of phenols from wastewater was found to be 50--65% under given conditions. [ABSTRACT FROM AUTHOR]

The present study focuses on the fate of polycyclic aromatic hydrocarbons (PAHs) in soils amended with oil shale ash (OSA). Leachability studies to assess the release of PAHs to the environment are essential before the application of OSA in agriculture. A quantitative estimation of the leaching of PAHs from two types of soil and two types of OSA was undertaken in this study. Two leaching approaches were chosen: (1) a traditional one step leaching scheme and (2) a leaching scheme with pretreatment, i.e.., incubation of the material in wet conditions imitating the field conditions, followed by a traditional leaching procedure keeping the total amount of water constant. The total amount of PAHs leached from soil/OSA mixtures was in the range of 15 to 48 μg/kg. The amount of total PAHs leached was higher for the incubation method, compared to the traditional leaching method, particularly for Podzolic Gleysols soil. This suggests that for the incubation method, the content of organic matter and clay minerals of the soil influence the fate of PAHs more strongly compared to the traditional leaching scheme. The amount of PAHs leached from OSA samples is higher than from soil/OSA mixtures, which suggests soils to inhibit the release of PAHs. Calculated amount of PAHs from experimental soil and OSA leaching experiments differed considerably from real values. Thus, it is not possible to estimate the amount of PAHs leached from soil/OSA mixtures based on the knowledge of the amount of PAHs leached from soil and OSA samples separately. [ABSTRACT FROM AUTHOR]

The focus of the current study is to characterise the leaching behaviour of polycyclic aromatic hydrocarbons (PAHs) from oil shale ashes (OSAs) of pulverised firing (PF) and circulating fluidised-bed (CFB) boilers from Estonian Thermal Power Plant (Estonia) as well as from mortars and concrete based on OSAs. The target substances were 16 PAHs from the EPA priority pollutant list. OSA samples and OSA-based mortars were tested for leaching, according to . for monolithic matter was used for OSA-based concrete. Water extracts were analysed by GC-MS for the concentration of PAHs. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene were detected. Still, the release of PAHs was below the threshold limit value for inert waste. The amount of the finest fraction (particle size <0.045 mm), the content of the Al-Si glass phase and the surface characteristics were the main factors, which could affect the accessibility of PAHs for leaching. The mobility of PAHs from OSA of CFB and PF boilers was 20.2 and 9.9 %, respectively. Hardening of OSA-based materials did not lead to the immobilisation of soluble PAHs. Release of PAHs from the monolith samples did not exceed 0.5 μg/m. In terms of leaching of PAHs, OSA is safe to be used for construction purposes. [ABSTRACT FROM AUTHOR]

The present work focuses on the environmental effect of oil shale retorting residues originating from gaseous (GHC) and solid heat carrier (SHC) technologies. Samples were taken from Viru Keemia Grupp Oil factory (VKG Oil Ltd, Estonia). The water extracts of semi-coke samples from GHC retorting plants were non-toxic. The leachate water of SHC retorting ash was acutely toxic to Daphnia magna among tested organisms. The water extracts of semi-coke and retorting ash were acutely toxic at lower pH values and the release of anions and molybdenum increased significantly. The results show strong positive correlation between the toxicity and salinity/electric conductivity of the leachates. Release of anions in turn is related to the degree of decomposition of mineral phases during the retorting process. [ABSTRACT FROM AUTHOR]

To estimate the environmental properties of oil shale ash-based mortars the leaching of harmful components was studied. The leachates were highly alkaline. The predominant ions were Ca2+, K+, Na+, SO4 2-. The leachable content of soluble components in PF ash mortars was higher in comparison with that in CFB ash mortars. Results indicated that over curing time the fraction of readily soluble inorganic components decreased and the mobility of potentially hazardous Cd and Zn did not increase. Addition of bypass dust could affect the content of leachable ions. Results give new knowledge about the environmental properties of oil shale ash-based materials, including backfilling composites for underground mining technology. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory leaching tests of bottom and fly ash samples from an oil shale fueled pulverized firing (PF) and a circulated fluidized bed (CFB) boiler in 1:10 (wt/vol) suspensions of deionized water were performed. The ash samples were characterized for BETN2 specific surface area, mesopore distribution and contents of elements by ICP-MS. Water extracts were analyzed for pH, conductivity and the contents of 22 elements by ICP-MS. Several toxic metals, e.g. Tl, Mo, Sr, Cr and Pb, exhibited higher mobilization rates in fly ash samples from the PF boiler after two sequential extraction cycles compared to fly ashes from the CFB boiler. Higher mobility of trace elements in fly ash samples from the PF boiler may be explained by higher temperature in the furnace chamber of the PF boiler compared to the CFB boiler and surface characteristics of the ashes. According to the results the release of some trace elements, such as V, Cr, Ni, Cu, Zn, Mo, Cd, Ba, Tl and Pb from oil shale ash to aqueous environment is a long-term process. [Copyright &y& Elsevier]

Abstract: The leaching behavior of selected polycyclic aromatic hydrocarbons (PAHs) from an oil shale processing waste deposit was monitored during 2005–2009. Samples were collected from the deposit using a special device for leachate sampling at field conditions without disturbance of the upper layers. Contents of 16 priority PAHs in leachate samples collected from aged and fresh parts of the deposit were determined by GC–MS. The sum of the detected PAHs in leachates varied significantly throughout the study period: 19–315μg/l from aged spent shale, and 36–151μg/l from fresh spent shale. Among the studied PAHs the low-molecular weight compounds phenanthrene, naphthalene, acenaphthylene, and anthracene predominated. Among the high-molecular weight PAHs benzo[a]anthracene and pyrene leached in the highest concentrations. A spent shale deposit is a source of PAHs that could infiltrate into the surrounding environment for a long period of time. [Copyright &y& Elsevier]

A field study of the leaching of trace elements from the upper soil layer of a spent shale deposit was carried out. The study was conducted by installing a set of samplers in both active and closed parts of the deposit. Leachates were analyzed for pH, conductivity and concentrations of elements by ICP-MS. The results indicated release of metals from both parts of the deposit. Among the elements Mo, Zn, Ni, Cu, Cr and V were most mobile. The highest concentrations of Mo (104 μg/l), Zn (80 μg/l) and Ni (76 μg/l) were found in leachates from the active part of the deposit. [ABSTRACT FROM AUTHOR]

Dehydrogenase enzyme activity (DHA) assay method using resazurin was accommodated for measuring of toxicity of compound contaminants on uncharacterized microbial communities present in any given soil. The method was used to compare the toxic effect of heavy metal and polycyclic aromatic hydrocarbon (PAH) contaminant mixture (Cr, Pb, Cu, Cd, Pyrene) on four typical Estonian soils covering a range of compositions. The method proved to be useable on all soils; the sensitivity of soil microbiology to toxic effect of contaminants was found to have a negative correlation with Ca and organic matter (OM) content and a positive correlation with amorphous phase content of soils. [Copyright &y& Elsevier]

This study was designed to assess the contamination of a very special lake, Lake Baikal in Siberia, and two big lakes, Ladoga and Onega in the European part of Russia, by polycyclic aromatic hydrocarbons (PAHs). PAH compounds were analyzed by HPLC and the target PAH, benzo[ a ]pyrene (B a P), by using the spectral-luminescence (Shpol'skii) method. Elevated levels (to 96 μg kg -1 ) of B a P in sediments of Lake Baikal reflected proximity to potential sources of emission, situated either on shore (a paper and pulp mill in Baikalsk) or upstream river systems. The concentration of B a P in sediments decreased with the distance from outlet and the depth. The sediment samples contained several representatives of PAHs. The total content of identified compounds reached 873 μg kg -1 (less than four nuclear representatives not included). Dominating heavy PAHs were dibenz[ a,j ]anthracene, dibenz[ a,h ]anthracene, dibenzo[ a,e ]pyrene, and dibenzo[ a,l ]pyrene. The concentration of B a P in sediments of northeastern Baikal was more than two times less than that for the southern part of the lake and corresponds to the background level. The B a P levels estimated for sediments close to paper and pulp mills of the Lake Ladoga exceeded 160 μg kg -1 , being two orders of magnitude higher than that for other areas of these lakes. The contamination of sediments of Lake Onega by PAHs is affected by pulp and paper mills as well as other sources. Our results clearly demonstrate the contribution of specific industrial sources like paper and pulp mills to the content of PAHs in the Baikal, Ladoga, and Onega water ecosystem. [ABSTRACT FROM AUTHOR]

Ash generated by oil shale combustion contains polycyclic aromatic hydrocarbons (PAHs) hazardous for environment and human health. The leaching of three- to four-ring PAHs sorbed on oil shale ash and zeolite NaA used as reference matter was investigated. The uptake of PAHs on ash was linearly correlated with the molecular surface area and K ow . The ash and zeolite have similar specific surface area and different characteristics of pores contribution to the total pore volume. The sorption capacity of ash for PAH was four times less than that of aluminosilicate. PAHs sorbed on ash particles leached more readily than those on zeolite. After 3 hr the amount of leached PAHs was 89.6% for phenanthrene and 30% for less-soluble anthracene. In field conditions during the disposing time, the mineral composition and sorptive capacity of ash may change and affect the mobility of PAHs. [ABSTRACT FROM AUTHOR]

The use of various in vitro toxicity assays for testing environmental solid samples is dependent on the availability of reliable methods for the sampling and pretreatment of the material. This study focuses on the evaluation of leaching behaviour as a first step in the context of the toxicity testing of solid environmental matter. Spent shale, from oil shale retorting, was chosen as a suitable example of deposited solid waste material. For the generation of leachate in the laboratory setting, a standard two-stage batch-leaching test was applied to the samples of technogenic waste. In the field, a new type of lysimeter, which does not disturb the surface, was used for in situ leachate collection. The chemical composition of water extracts was found to be different under field conditions, as compared with the laboratory experiments. Thus, the hazard identification of a solid technogenic waste by in vitro toxicological tests applied to laboratory leachates would not be the best solution. The content of hazardous ingredients could be underestimated if only laboratory tests are used. For risk assessment concerned with solid waste materials, the generation of leachate by using field lysimeters is recommended.

Solid wastes from the oil-shale industry produce leachates containing toxic compounds such as heavy metals and persistent polycyclic aromatic hydrocarbons (PAH). The hazard to the environment represented by waste leachates depends not only on their chemical composition, but also on the mobility and bioavailability of toxic contaminants in soils. We evaluated the applicability of bioassays for toxicity assessment of the bioavailable fraction of heavy metals and PAH in soils, in experiments with samples of four different soil types (Rendzina, Brown pseudopodzolic, Typical brown, Sodpodzolic), the pH of which ranged from 6.2 to 7.2. The toxicity of the bioavailable fraction of the soil contaminants was assessed with the dehydrogenase enzyme activity assay, and with a Toxkit microbiotest with the crustacean, Thamnocephalus platyurus, after treatment of the soil samples with an artificial solution containing chromium (III), lead (II), copper (II), cadmium (II) and pyrene. The test results confirm those of earlier experiments, which characterised the sorption potential of investigated soils for the same compounds. Both tests turned out to be sufficiently sensitive, and hence can be recommended as effective and useful tools for the assessment of the bioavailable fraction of soil contaminants.