[Compositions and residual properties of petroleum hydrocarbon in contaminated soil of the oilfields].

The aims of this study were to determine the compositions and residual properties of petroleum hydrocarbon in soil, as well as to identify the source and weathering degree of the pollution. A total of 5 producing wells in Gudao and Hekou oil producing region of Shengli oilfields were analyzed. More than 50 individual target compounds including straight-and branched-chain alkanes( n-alkanes, pristine and phytane) and polycyclic aromatic hydrocarbons (PAHs) in soil samples and crude oil were determined by gas chromatography-mass spectrometry (GC-MS). The percentages of chain alkanes and PAHs in total solvent extractable matters(TSEM) of soil samples were both much lower than those in the crude oil samples. The compositions of petroleum hydrocarbon in soil samples differed from those in crude oil, which indicated the n-alkanes with carbon numbers <12 were much easier to lose in contrast to the n-alkanes with high carbon numbers. With n-octadecane/phytane as index for the weathering rate of oil contaminated soils, the relationship between the index and petroleum hydrocarbon compounds was analyzed using principal component analysis (PCA). The results showed that the n-alkanes with carbon numbers > 33 and the PAHs with rings between 3 and 5 were much harder to degrade. PCA of 4 indexes for source identification revealed more than 50% of the soil samples were polluted by crude oil, which needs more attention during remediation.

[Microbial community structure and distribution characteristics in oil contaminated soil].

Molecular biology methods such as PCR-DGGE combined with phylogenetic analysis were used for the soil microbial community structure and distribution profiling. Relationship of microbial community structure and distribution differed in a typical oil contaminated field was studied. Results showed that soil oil content was the main factor to the difference of microbial community structure similarity. The similarity index of microbial community structure and oil content had a significantly negative correlation. The contaminated soil microorganism genus had an uneven distribution. Thus, soil pollution had obvious stress and differentiation for microbial community structure and species relationship. Dominant species in oil contaminated soil were identified as Gulosibacter, Halomonas, Petrobacter, Methylocystis, and Pseudoalteromonas. The findings provide a basis for understanding the microbial characteristics of oil contaminated soil.

[Removal of oil in the lake water in Daqing area using subsurface constructed wetland].

Based on the water quality and climate of the oil contaminated lake in Daqing area, four simulated subsurface wetland systems were constructed in the field to study their removal effect of oil in lake water, including the gravel bed, the gravel-reed bed, the slag-reed bed and the slag bed. The research lasted about 360 d, including five periods: the start up period, the microorganism adding period, the slow-releasing carbon sources adding period, the low temperature period and the normal operation period. During the study, oil removal efficiency of the four units are 24.7%,28.4%, 45.9% and 42.9% respectirely, and the slag unit shows better than gravel unit. The adding of microorganism and slow-releasing carbon sources markedly improves the oil removal. The application of plant in the wetland system also promotes the oil removal. In all the four simulated subsurface wetland systems, 70% of the oil removal attributes to the adsorption effect.

[Physical and chemical effects and plant growth suitability of substrates in subsurface flow wetland].

Substrate, which not only takes part in the pollutant-removing, but influences the plant growth, plays an important role in subsurface flow wetland. With X-ray fluorescence measurement and X-ray diffractometer, the elements and minerals in zeolite and shale were confirmed, and the removal mechanics of nitrogen, phosphate and hydrogen ion in substrates were explained respectively. The investigation show that the zeolite has abounded with micropores and mesopores, while the shale has only mesopores, which causes the NH4+ -N adsorption capability of the shale is less than zeolite. The PO4(3-) -P removal and hydrogen ion buffer capacity of shale are greater than those of zeolite because CaCO3 is one of the main contents of shale. In pilot-plant system to treat starch waste water, the reeds and acorus aclamuc were either planted in shale and zeolite, and the phytum's indexes in shale including relative green concentration, average plant height, root stem ratio were higher than those in zeolite. The root vitality of reeds and acorus aclamuc planted in shale were 3.7 and 1.6 times of those in zeolite respectively. Total nitrogen and phosphorus contents in the plant organization of acorus aclamuc in shale were 7.8 and 3.4 times of those in zeolite; total nitrogen and phosphorus contents in the plant organization of reeds in shale were 3.3 and 2.2 times of those in zeolite. The results indicate that shale provides a steady pH for the plant's root in the acid waste water and it is more suitable for plant growth than zeolite.

[Effects of plants on nitrogen/phosphorus removal in subsurface constructed wetlands].

Effects of plants on nitrogen/phosphorus removal was studied in pilot-scale in subsurface constructed wetland, the main contents included nutrient uptake, effects of harvesting and roots on hydraulic condition. The result show that the amounts of nitrogen and phosphorous removed by plant harvesting is about 5% of the total removed nutrients in SFS wetlands. The best harvesting periods is between 9-10 month every year. Plant harvesting may induce fluctuation of outflow; aboveground biomass can stabilize micro-environmental of roots. The roots can also improve hydraulic condition of SFS system, decreasing dead area 5 % - 10 % and extending hydraulic retention time.

[Effects of acid soils on the biodegradation of hydrocarbons].

Biodegradation efficiency of hydrocarbons and melioration of micro-ecosystem conditions in acid soils should be seriously concerned due to either occurrence of acid polluted soils or acidification during bioremediation process. The influence of acid situation on degrading microbes and the biodegradation rate were figured out by monitoring variations of biomass, microbial activities and petroleum contents with time in acid and alkaline polluted soils in laboratory. Injecting degrading microbes and meliorating micro-ecosystem conditions of acid soils were conducted. The results showed that acid soils (pH = 5.4-5.7) had extreme restraint on local microbe numbers and activities, and biodegradation rate almost reached zero. Injection of degrading microbes could not remarkably reduce the restriction of acid conditions. The microbe numbers quickly went down from 10(6) cells/g dried soil to zero in 14 days and the Fluorescein Diacetate (FDA) activities were only about 0.10 Abs/g dried soil. However, addition of bio-carriers could effectively improve micro-ecosystem conditions in acid soils, thus notably diminish the restraint to some extent. In 19 days, the amount of microorganisms decreased from 2 x 10(6) to 2.2 x 10(2) cells/g dried soil. And up to 49 days, about 13% hydrocarbons were removed from the polluted soils by microbes.

[The relationship between abiotic factors and microbial activities of microbial eco-system in contaminated soil with petroleum hydrocarbons].

By means of the biostimulation and bioaugmentation in the micro-ecological environment of contaminated soil with petrochemical hydrocarbons, the biodegradation rates and mode of the contaminants were significantly improved. Based on the investigations carried out in some oilfields and petrochemical industrial area of Northern China, the relationship between the abiotic factors such as nutrient, pH, contaminants, water content, alkalinity, etc., and microbial activities was interpreted and identified in this paper. The results from the investigations and indoor and in-situ experiments conducted recent years indicated that the soils in the areas, to the extent, have been polluted by the different kinds of organic compounds composed of monoaromatic benzene, PAHs, chlorinated solvent, and alkanes, and the concentrations of the compounds mostly were elevated as compared to the background, with the highest 34,000 mg/kg dry soil. The column chromatography analysis results showed that the alkyl and aromatic compounds were accounted for more than 50% of the total hydrocarbon contents, which was readily degraded by degrading bacteria and improved the degrading microbe activities. The effective nitrogen and phosphorus encountered in the soil was less than 30 mg/kg dry soil and 10 mg/kg dry soil, only about 5% of total contents of them respectively. Based on the stoichiometric calculation and reasonable ratio of carbon to nutrient content regarding the biodegradation of organic compounds, the nutrient levels mainly composed of nitrogen and phosphorus in polluted soil as importantly limiting factors to degrading bacterial growth and activity were insufficient to the biodegradation of petrochemicals, and it is needed to add the nutrient for the bioremediation of contaminated soil. It is undoubted that the optimization of abiotic factors play significant role in increasing the microbial activity and improving the biodegradation rates.

Production of biosurfactant and its role in the biodegradation of oil hydrocarbons.

Based on indigenous bacteria from the oil-contaminated site of Dawu water source area in Zibo city of China, the production of biosurfactant and its role in the biodegradation of oil hydrocarbons have been investigated. Batch experiments were performed with paraffin as the sole substrate under temperature of 30 degrees C and pH of 7. Two high-effective species of bacteria (Z1 and Z2) were isolated. During the growth of both species, biosurfactants were produced, as indicated by the decrease of surface tensions of the enrichment medium from 61 to 45 mN/m. The critical micelle concentration (CMC) of Z1 ferment liquid was 0.4 (volume content). When reaching the CMC, Z1 ferment liquid demonstrated the effect of dissolution enhancement, that is, it could enhance the dissolved concentration of phenanthrene to above 1 mg/L, which was higher than the saturated solubility of phenanthrenene under standard condition. Elementary identification results revealed that both Z1 and Z2 belongs to bacillus. Z1 was 0.5 microm in diameter, 0.5-3 microm in length, and bearing flagellum, while Z2 was 0.2 microm in diameter, 0.5-1 microm in length and no flagellum.