Development of an Oil-Degrading Biopreparation by Activation of Aboriginal Hydrocarbon-Oxidizing Microflora

A method of activation of aboriginal hydrocarbon-oxidizing microorganisms for remediation of soil and water basins polluted with oil products was developed. The optimum composition of activating additives was found (g/l): mineral components, 10.0; oil, 5.0; and a synthetic detergent, 0.2. The resulting biopreparations increased the degree of purification by factors of 4–8 in soil and 18–24 in water when applied at a concentration of 10⁷ cells/g(ml).     

不同覆盖方式对旱地胡麻土壤硝态氮和籽粒产量的影响

为了探讨黄土高原旱作雨养条件下覆盖种植胡麻田土壤硝态氮动态特征和增产效果,在2015和2016年胡麻生长季,以常规种植模式为对照(CK),研究了3种覆盖方式(全膜微垄覆土穴播、全膜覆土穴播和秸秆覆盖条播)对胡麻籽粒产量和关键生育时期农田硝态氮分布的影响.结果表明: 与CK相比,覆盖处理的胡麻籽粒产量分别增加56.1%(2015)和22.7%(2016),且均以全膜覆土穴播处理的籽粒产量最高.覆膜提高了胡麻根际土壤水分含量,在整个生育期的影响程度为先增加后降低;随着胡麻生育进程的推进,土壤硝态氮含量逐渐降低.两年试验中,覆盖处理下胡麻现蕾期0～40 cm土层硝态氮含量分别比CK增加3.1%～18.6%(2015)和5.1%～16.4%(2016),其中,全膜覆土穴播的增幅最大.2015年,胡麻盛花期和成熟期0～100 cm土层土壤硝态氮积累量较CK分别增加10.2%～22.2%和8.6%～21.4%,特别是在降雨较多的成熟期,0～40 cm土层土壤硝态氮含量较40～100 cm土层显著提高3.3%～4.9%,说明覆盖处理可以减缓硝态氮向下层的迁移.2016年,生育后期的高温干旱对胡麻生长造成了极大的影响,胡麻成熟期覆盖处理0～100 cm土层硝态氮积累量较CK显著增加6.6%～18.0%.相关分析表明,胡麻关键生育时期不同土层的土壤硝态氮含量与籽粒产量之间有显著正相关关系.综合考虑,全膜覆土穴播模式是适宜干旱、半干旱区推广应用的胡麻高产高效栽培方式.     

Characterisation and some possible uses of Plukenetia conophora and Adenopus breviflorus seeds and seed oils

Crude oil-polluted soil (five parts of weathered crude oil per 100 parts of soil; equivalent to 50,000 mg oil kg(-1) soil) samples were slurried in deionised water (300% of the water retention capacity of the soil) and treated with various amounts of natural-rubber processing sludge (nitrogen content 62.15 mg kg(-1) and phosphorus contents 8.75 mg kg(-1)) in a well-stirred, continuously-aerated tank at 29 degrees C. Changes in the total hydrocarbon content of the soil sample were determined, using a spectrophotometric technique, as a function of time. The extent of crude oil degradation was markedly higher (by up to 100%) in the sludge-treated soil than in the untreated soil sample. The efficiency of biodegradation of the crude oil hydrocarbons using the slurry-phase technique was compared with that of solid-phase technique.     

Bioremediation of soil polluted with fuels by sequential multiple injection of native microorganisms: Field-scale processes in Poland

Research was conducted to estimate impact of the multiple bioaugmentation on the treatment of soil contaminated by fuels - diesel oil and aircraft fuel. The bacteria used to inoculate the remediation plots were isolated from the polluted soil and proliferated in field conditions. The amount of biomass applied to the polluted soil was set to ensure the total number of bacteria in soil 10⁷-10⁸ cfu/g d.w. The multiple inoculation of soil with indigenous bacteria active in diesel oil and engine oil (plot A) degradation increased bioremediation effectiveness by 50% in comparison to the non-inoculated control soil and by 30% in comparison to the soil that was inoculated only once. The multiple inoculation of soil with indigenous microorganisms was then applied in bioremediation of the soil polluted with double high concentration of diesel oil (soil B) and in bioremediation of the soil polluted with aircraft fuel (soil C). The process efficiency was 80% and 98% removal of TPH for soil B and C, respectively.     

Oil Palm Empty Fruit Bunch and Sugarcane Bagasse Enhance the Bioremediation of Soil Artificially Polluted by Crude Oil

Contamination of soil by petroleum hydrocarbons is becoming prevalent in Malaysia. Infiltration of soil contamination into groundwater poses a great threat to the ecosystem and human health. Bioremediation can occur naturally or can be enhanced with supplementation of microorganisms and fertilizers. However, fertilizers are expensive and therefore alternative nutrient-rich biomaterials are required. In this study, two organic wastes from agricultural industry (i.e., sugarcane bagasse and oil palm empty fruit bunch) were investigated for possible enhanced bioremediation of soil contaminated with Tapis crude oil. Two bacterial strains isolated and characterized previously (i.e., Pseudomonas aeruginosa UKMP-14T and Acinetobacter baumannii UKMP-12T) were used in this study. Sugarcane bagasse (5% and 15%, w/w) and oil palm empty fruit bunch (20%, w/w) were mixed with soil (500 g) spiked with Tapis crude oil (3%, v/w). The treated soils as well as controls were incubated for 20 days under controlled conditions. Sampling was carried out every four days to measure the number of bacterial colonies (CFU/g) and to determine the percentage of oil degradation by gas chromatography. The two biostimulating agents were able to maintain the soil moisture holding capacity, pH, and temperature at 38-40% volumetric moisture content (VMC), 7.0, and 29–30°C; respectively. The growth of bacteria consortium after 20 days in the treatment with sugarcane bagasse and oil palm empty fruit bunch had increased to 10.3 CFU/g and 9.5 CFU/g, respectively. The percentage of hydrocarbon degradation was higher in the soil amended with sugarcane bagasse (100%) when compared to that of oil palm empty fruit bunch (97%) after 20 days. Our results demonstrated the potential of sugarcane bagasse and oil palm empty fruit bunch as good substrates for enhanced bioremediation of soil contaminated with petroleum crude oil.     

蚂蚁筑巢对西双版纳热带森林土壤易氧化有机碳时空动态的影响

蚂蚁筑巢定居能够形成与巢穴周围显著不同的微生境和土壤养分环境,从而对土壤易氧化有机碳(EOC)产生重要影响.本研究以中国科学院西双版纳勐仑热带植物园白背桐群落为研究对象,比较蚂蚁巢地与非巢地土壤EOC时空分布特征,并分析蚂蚁筑巢引起土壤理化性质的改变对土壤EOC时空动态的影响.结果表明: 研究区蚁巢和非蚁巢地土壤EOC随月份均呈明显的单峰型变化规律,表现为6月>9月>3月>12月;土壤EOC沿土层呈逐渐降低的变化趋势,在0～5 cm土层,蚁巢土壤EOC显著大于非巢地,在5～10和10～15 cm土层的差异不显著.蚂蚁筑巢显著提高了土壤温度、土壤有机碳、土壤易氧化有机碳、土壤微生物生物量碳、全氮、硝态氮和水解氮含量,显著降低了土壤含水率和容重,但对铵态氮、pH值的影响不显著.土壤有机碳、土壤微生物生物量碳是调控蚁巢和非巢地土壤EOC时空变化的主要因子,土壤温度、含水率、全氮和硝态氮等土壤指标对土壤EOC的影响次之.蚂蚁筑巢主要通过改变微生境(土壤温度和水分)及土壤养分(主要是土壤有机碳和微生物生物量碳)的状况,进而调控热带森林土壤易氧化有机碳的时空动态.     

Nitrification and utilization of ammonium and nitrate during oil bioremediation at different soil water potentials

Bioremediation of petroleum spills requires aerobic soil conditions and readily available N, which may be susceptible to leaching. Our objectives were to determine the influence of soil water potential on nitrification in the presence of crude oil, the toxicity of oil to NHj‐oxidizing bacteria, and the preferences of microorganisms for NH⁺ ₄ or NO^? ₃. A Weswood clay loam was amended with crude oil to contain 0, 5, and 10% by soil dry weight, and N was added to achieve C:N ratios of 90:1 and 120:1. Soil water potentials were maintained at ‐0.02, ‐0.1, and ‐1.0 kJ/kg or allowed to fluctuate between ‐0.02 and ‐3 kJ/kg. Concentrations of NH⁺ ₄ and NO₃ ^?were measured during an incubation period of 40 d. Nitrification in soil not amended with oil was rapid at water potentials of ‐0.02 and ‐0.1 kJ/kg but inactive at a water potential of ‐1.0 kJ/kg. Oil reduced nitrification rates and populations of NH⁺ ₄‐oxidizing bacteria. Little NO^? ₃ accumulated when the C:N ratio was 120:1, but when the C:N ratio was 90:1, up to 150 μg of NO₃‐N/g of soil accumulated at a soil water potential of ‐0.02 kJ/kg. Soil water potential in the range used did not greatly influence the extent of oil bioremediation but significantly influenced nitrification. Ammonium was preferentially used over NO^? ₃ by microorganisms during oil bioremediation. Nitrate accumulation from urea applied to stimulate oil bioremediation was low when N application matched requirements for oil bioremediation, and nitrification was restricted by controlling soil water content.     

Case Study of Petroleum Contaminated Area of Novi Sad After NATO Bombing in Yugoslavia

The 1999 NATO bombing of the oil refinery in Novi Sad (Yugoslavia) has heavily contaminated the Danube River and its sediments, as well as the surrounding soil and groundwater. The destruction of the factories released 73,569 tons of crude oil of which 90% was incinerated, 560 tons reached the Danube River, and the remainder was spilled onto the soil. The contents of oil and oil derivatives in the soil were in the range of 3 to 42,000?mg/kg. The first soil layer contained an average of 67,000?mg/kg of crude oil and oil derivatives. The layers beneath it, above the groundwater table, contained 56?ml/l of free oil derivatives in the drained water. The spreading of this pollution could imperil the groundwater quality in the water supply zone because the refinery is located in the hinterland of the zone. The quality of water and sediment samples was monitored from April 1999 to November 2000 by measuring concentrations of hydrocarbons and polyaromatic hydrocarbons (PAH). The hydrocarbon content in the Danube River water in October 2000 was about 20% of the value measured at the time of the accident. Immediately after the accident the concentration of mineral oil in the surface sediment was in the range of 0.11 to 0.29?g/kg. At the same time PAH concentrations in the river sediment were up to 160?mg/kg, depending on the sampling site location. The values showed a decrease in the course of further monitoring.     

The potential of Chromolaena odorata (L) to decontaminate used engine oil impacted soil under greenhouse conditions

This study reports on the use of Chromolaena odorata (L) R.M. King and H. Robinson, an Asteraceae (compositae) and an invasive alien weed in Africa for the remediation of soil contaminated with used engine oil. Used engine oilfrom a motor service garage was used to artificially contaminate soil taken from a garden to give total petroleum hydrocarbon (TPH) of between 1 and 40 g kg(-1). Chromolaena odorata (L), propagated by stem cuttings were transplanted into the contaminated soil and watered just enough to keep the soil at about 70% water holding capacity for 90 day. A set of control experiments containing 40 g kg(-1) used engine oil but without plants was set up. All experiments were set up in triplicates. Although the plants in the experiments containing higher than 30 g kg(-1) used engine oil showed relatively slower growth (fewer branches and leaves, and shorter in height) compared to those containing lower concentrations, the plants in all the experiments continued to grow until the end of the 90 day period. Residual TPH after 90 days showed that between 21 and 100% of oil was lost from the planted soil while only 11.5% was lost in the control, which did not contain plants during the same period. Analysis of plant tissues showed that both shoot and root tissues contained detectable levels of TPH and selected PAHs were also detectable. Biomass accumulation by Chromolaena odorata was affected adversely by concentrations of oil higher than 20 g kg(-1). Results of germination rates and germination energy measurements showed that Chromolaena odorata was able to reduce the toxicity of the contaminated soil after 90 days as compared to soils containing freshly contaminated soiL     

Enhanced haloarchaeal oil removal in hypersaline environments via organic nitrogen fertilization and illumination

Hypersaline soil and pond water samples were mixed with 3?% crude oil, some samples were autoclaved to serve as sterile controls; experimental samples were not sterilized. After 6-week incubation at 40?°C under light/dark cycles, the soil microflora consumed 66?%, and after 4?weeks the pond water microflora consumed 63?% of the crude oil. Soil samples treated with 3?% casaminoacids lost 89?% of their oil after 6?weeks and water samples lost 86?% after 4?weeks. Samples treated with casaminoacids and antibiotics that selectively inhibited bacteria, lost even more oil, up to 94?%. Soil-water mixtures incubated under continuous illumination lost double as much more oil than samples incubated in the dark. The soil-water mixture at time zero contained 1.3?×?10(4) CFU?g(-1) of hydrocarbon-utilizing microorganisms which were affiliated to Halomonas aquamarina, Exiguobacterium aurantiacum, Haloferax sp., Salinococcus sp., Marinococcus sp. and Halomonas sp. After 6-week incubation with oil, these numbers were 8.7?×?10(7?)CFU?g(-1) and the Haloferax sp. proportion in the total microflora increased from 20 to 93?%. Experiments using the individual cultures and three other haloarchaea isolated earlier from the same site confirmed that casaminoacids and light enhanced their oil consumption potential in batch cultures.     

Bioemulsifier production by Streptomyces sp. S22 isolated from garden soil

Out of 45 actinomycetes isolated from garden soil, pond water and air; fifteen showed good emulsification activity. Streptomyces sp. S22 isolated from garden soil produced maximum bioemulsifier with 0.5% (v/v) sunflower oil during stationary phase at 37 degrees C, pH 6 and 250 rev/min. Emulsification activity was maximum (320 EU/ml) with sunflower oil as substrate. Partially purified bioemulsifier from Streptomyces sp. S22 was a peptidoglycolipid containing lipid (51.25%), protein (30%), non-reducing sugar (17.75%) and reducing sugar (1%). The yield of partially purified bioemulsifier was 1.6 g/l and reduced the surface tension of water by 23.09 mN/m. The bioemulsifier produced by Streptomyces sp. S22 was stable at room temperature for seven days.     

Petroleum bioremediation — a multiphase problem

Microbial degradation of hydrocarbons is a multiphase reaction, involving oxygen gas, water-insoluble hydrocarbons, water, dissolved salts and microorganisms. The fact that the first step in hydrocarbon catabolism involves a membrane-bound oxygenase makes it essential for microorganisms to come into direct contact with the hydrocarbon substrate. Growth then proceeds on the hydrocarbon/water interface. Bacteria have developed two general strategies for enhancing contact with water-insoluble hydrocarbons: specific adhesion mechanisms and production of extracellular emulsifying agents. Since petroleum is a complex mixture of many different classes of hydrocarbons, of which any particular microorganism has the potential to degrade only part, it follows that the microorganisms must also have a mechanism for desorbing from used' oil droplets.The major limitations in bioremediation of hydrocarbon-contaminated water and soil is available sources of nitrogen and phosphorus. The usual sources of these materials, e.g. ammonium sulfate and phosphate salts, have a high water solubility which reduces their effectiveness in open systems because of rapid dilution. We have attempted to overcome this problem by the use of a new controlled-release, hydrophobic fertilizer, F-1, which is a modified urea-formaldehyde polymer containing 18% N and 10% P as P₂O₅. Microorganisms were obtained by enrichment culture that could grow on crude oil as the carbon and energy source and F-1 as the nitrogen and phosphorus source. The microorganisms and the F-1 adhered to the oil/water interface, as observed microscopically and by the fact that degradation proceeded even when the water phase was removed and replaced seven times with unsupplemented water — a simulated open system. Strains which can use F-1 contain a cell-bound, inducible enzyme which depolymerizes F-1.After optimizing conditions in the laboratory for the use of F-1 and the selected bacteria for degrading crude oil, a field trial was performed on an oil contaminated sandy beach between Haifa and Acre, Israel, in the summer of 1992. The sand was treated with 5 g F-1 per kg sand and inoculated with the selected bacteria; the plot was watered with sea water and plowed daily. After 28 days the average hydrocarbon content of the sand decreased from 5.1 mg per g sand to 0.6 mg per g sand. Overall, there was an approx. 86% degradation of pentane extractables as demonstrated by dry weight, I.R. and GLC analyses. An untreated control plot showed only a 15% decrease in hydrocarbons. During the winter of 1992, the entire beach (approx. 200 tons of crude oil) was cleaned using the F-1 bacteria technology. The rate of degradation was 0.06 mg g^-1 sand day^-1 (10°C) compared to 0.13 mg g^-1 sand day^-1 during the summer (25°C).     

Physical and Biological Treatment of Oil-Contaminated Soil in a Baffled Roller Bioreactor

Physical and biological removal of diesel oil from contaminated soil was studied in a baffled roller bioreactor. Initially, the effects of four factors (soil loading, temperature, pH, and surfactant) on physical removal of diesel oil were investigated. Only the presence of a surfactant (sodium dodecyl sulfate [SDS]) demonstrated a significant effect on diesel oil removal. Diesel oil removal efficiency was increased from 32.0% to 63.9% in the presence of 100 mg/L SDS. Using a microbial culture enriched from contaminated soil, biological treatment of diesel oil polluted soil under different soil loadings (15% to 50%), different diesel oil concentrations (1 to 50 g/L), and different types of soil (sand, silt, and clay) was then investigated in the baffled roller bioreactor. Biodegradation consisted of both fast and slow stages for degradation of light and heavy compounds, respectively. All biodegradation experiments demonstrated significant decreases in diesel oil concentrations (88.3% in 14 days for initial diesel oil concentrations of 1000 mg/L and a wide range of soil loadings). The presence of silty or sandy soils enhanced the biodegradation rate compared to the control bioreactor (without soil). The sandy soil loading had no effect on the biodegradation results. Using the enriched culture, the baffled roller bioreactor was able to biodegrade high diesel concentrations (up to 50 g/L) with biodegradation rates of 112.2 and 39.3 mg/L· h during fast and slow stages, respectively.     

黄土高原水蚀风蚀交错区植被地上生物量及其影响因素

采用野外调查的方法,于2009年9月下旬测定了六道沟小流域不同土地利用方式下的地上生物量以及土壤水分含量和养分含量,研究了水蚀风蚀交错区典型小流域植被地上生物量水平及其影响因素.结果表明:六道沟小流域主要植被地上干生物量在177～2207g·m-2;其中,玉米、谷子、弃耕地、人工草地、天然草地和灌木地的地上干生物量分别为2097～2207、518～775、248～578、280～545、177～396和372～680 g·m-2.农田平均土壤含水量(0～100 cm土层)最高,达14.2%,灌木地最低,为10.9%;弃耕地土壤水分含量的变异系数最大,为26.7%,说明弃耕地土壤水分有很强的空间异质性.土壤平均储水量大小顺序为:农田>人工草地>弃耕地>天然草地>灌木地,苜蓿地和柠条地出现土壤干化现象.植被地上干生物量与0～100 cm土层土壤储水量存在显著正相关关系(r=0.639,P<0.05),地上鲜生物量与植被的株高呈极显著正相关,较高植被的地上生物量可以间接控制水蚀风蚀交错区土壤侵蚀.植被地上生物量与土壤水分、养分具有很高的相关性,但与海拔、坡度、坡向、容重等的相关性不显著.     

The effect of soil: water ratios on the mineralisation of phenanthrene: LNAPL mixtures in soil

Contamination of soil by polycyclic aromatic hydrocarbons is frequently associated with non-aqueous-phase liquids. Measurement of the catabolic potential of a soil or determination of the biodegradable fraction of a contaminant can be done using a slurried soil respirometric system. This work assessed the impact of increasing the concentration of transformer oil and soil:water ratio on the microbial catabolism of [(14)C]phenanthrene to (14)CO(2) by a phenanthrene-degrading inoculum. Slurrying (1:1, 1:2, 1:3 and 1:5 soil:water ratios) consistently resulted in statistically higher rates and extents of mineralisation than the non-slurried system (2:1 soil:water ratio; P<0.01). The maximum extents of mineralisation observed occurred in the 1:2-1:5 soil:water ratio microcosms irrespective of transformer oil concentration. Transformer oil concentrations investigated displayed no statistically significant effect on total mineralisation (P>0.05). Soil slurries 1:2 or greater, but less than 1:5 (soil:water), are recommended for bioassay determinations of total contaminant bioavailability due to greater overall mineralisation and improved reproducibility.     

冀西北坝上半干旱区南瓜油葵间作的水分效应

针对冀西北高原水源匮乏、利用低效问题,于2009-2010年在农业部张北农业资源与生态环境重点野外观测试验站通过南瓜//油葵不同间作群体结构试验,探讨了该区南瓜水分高效的种植方式。试验设南瓜单作（Sp）,南瓜行间作1行油葵（IC1）,南瓜行间作2行油葵（IC2）和油葵单作（So）4个处理。结果表明,南瓜行间种植两行油葵（IC2）在南瓜生长中后期出现了油葵与南瓜争夺水分的现象,而南瓜行间种植一行油葵（IC1）无此现象。各处理间水量平衡各分量有较大的差异,在整个生育时期降雨量为201.6mm的情况下,渗漏量占的比重非常小,并且土壤蓄水量变化均为负值,绝大部分水分都是以气态水蒸散掉,但不同间作方式蒸散失水量不同,其中IC1较So、Sp和IC2分别少散失土壤水分36.33%、19.00%和34.87%。得益于油葵的偏利效应使南瓜经济产量下降30.00% ~71.42%,而间种油葵单株产量相对单作田提高190.71%~ 241.26%,虽其土地当量比LER和水分当量比WER分别达1.08~1.22和1.07~1.26,但IC1复合群体的经济效益只能与南瓜单作田持平,其他处理明显低于单作南瓜。在冀西北高原雨养背景下,稀植高效的南瓜单作生产能够实现对区域水资源的高效利用。     

Two-liquid-phase slurry bioreactors to enhance the degradation of high-molecular-weight polycyclic aromatic hydrocarbons in soil

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. The addition of a water-immiscible, nonbiodegradable, and biocompatible liquid, silicone oil, to a soil slurry was studied to promote the desorption of PAHs from soil and to increase their bioavailability. First, the transfer into silicone oil of phenanthrene, pyrene, chrysene, and benzo[a]pyrene added to a sterilized soil (sandy soil with 0.65% total volatile solids) was measured for 4 days in three two-liquid-phase (TLP) slurry systems each containing 30% (w/v) soil but different volumes of silicone oil (2.5%, 7.5%, and 15% [v/v]). Except for chrysene, a high percentage of these PAHs was transferred from soil to silicone oil in the TLP slurry system containing 15% silicone oil. Rapid PAH transfer occurred during the first 8 h, probably resulting from the extraction of nonsolubilized and of poorly sorbed PAHs. This was followed by a period in which a slower but constant transfer occurred, suggesting extraction of more tightly bound PAHs. Second, a HMW PAH-degrading consortium was enriched in a TLP slurry system with a microbial population isolated from a creosote-contaminated soil. This consortium was then added to three other TLP slurry systems each containing 30% (w/v) sterilized soil that had been artificially contaminated with pyrene, chrysene, and benzo[a]pyrene, but different volumes of silicone oil (10%, 20%, and 30% [v/v]). The resulting TLP slurry bioreactors were much more efficient than the control slurry bioreactor containing the same contaminated soil but no oil phase. In the TLP slurry bioreactor containing 30% silicone oil, the rate of pyrene degradation was 19 mg L(-)(1) day(-)(1) and no pyrene was detected after 4 days. The degradation rates of chrysene and benzo[a]pyrene in the 30% TLP slurry bioreactor were, respectively, 3.5 and 0.94 mg L(-)(1) day(-)(1). Low degradation of pyrene and no significant degradation of chrysene and benzo[a]pyrene occurred in the slurry bioreactor. This is the first report in which a TLP system was combined with a slurry system to improve the biodegradation of PAHs in soil.     

模拟氮沉降和降雨对华西雨屏区常绿阔叶林土壤呼吸的影响

从2013年12月至2014年11月,通过野外原位试验,对华西雨屏区常绿阔叶林进行了模拟氮沉降和降雨试验,采用LI-8100土壤碳通量分析系统(LI-COR Inc.,USA)测定了对照(CK)、氮沉降(N)、减雨(R)、增雨(W)、氮沉降+减雨(NR)、氮沉降+增雨(NW)6个处理水平的土壤呼吸速率,并通过回归方程分析了温度和湿度与土壤呼吸速率间的关系。结果表明:(1)氮沉降和增雨抑制了常绿阔叶林土壤呼吸速率,减雨促进了常绿阔叶林土壤呼吸速率。(2)减雨使华西雨屏区常绿阔叶林土壤呼吸年通量增加了258 g/m~2,而模拟氮沉降和增雨使华西雨屏区常绿阔叶林土壤呼吸年通量分别减少了321g/m~2和406g/m~2。(3)减雨增加了土壤呼吸的温度敏感性,模拟氮沉降和增雨降低了土壤呼吸的温度敏感性。(4)模拟温度和湿度与土壤呼吸速率间回归方程分析表明,土壤水分对土壤呼吸速率的影响较小。(5)模拟氮沉降和增雨处理减少土壤微生物生物量碳、氮的含量,减雨处理增加了土壤微生物生物量碳、氮的含量。(6)模拟氮沉降和降雨对华西雨屏区土壤CO_2释放的影响未表现出明显的交互作用。     

The Dynamic Change of Microbial Communities in Crude Oil-Contaminated Soils from Oil Fields in China

To study the biodegradability of microbial communities in crude oil contamination, crude oil-contaminated soil samples from different areas of China were collected. Using polyphasic approach, this study explored the dynamic change of the microbial communities during natural accumulation in oil field and how the constructed bioremediation systems reshape the composition of microbial communities. The abundance of oil-degrading microbes was highest when oil content was 3–8%. This oil content is potentially optimal for oil degrading bacteria proliferation. During a ～12 months natural accumulation, the quantity of oil-degrading microbes increased from 10⁵ to 10⁸ cells/g of soil. A typical sample of Liaohe (LH, oil-contaminated site near Liaohe River, Liaoning Province, China) was remediated for 50 days to investigate the dynamic change of microbial communities. The average FDA (a fluorescein diacetate approach) activities reached 0.25 abs/hr·g dry soil in the artificially enhanced repair system, 32% higher than the 0.19 abs/hr·g dry soil in natural circumstances. The abundance of oil-degrading microbes increased steadily from 0.001 to 0.068. During remediation treatment, oil content in the soil sample was reduced from 6.0% to 3.7%. GC–MS analysis indicated up to 67% utilization of C₁₀–C₂₀ normal paraffin hydrocarbons, the typical compounds that undergo microbial degradation.     

Effect of shale kerogen oxidation products on biodegradation of petroleum and petroleum products in soil and water

Effect of oxidation products of shale kerogen (high-molecular-weight acids with 6-22 carbon atoms) on biodegradation of oil and oil products in soil and water was studied. High-molecular-weight acids (HMWA) not only affected the layer of oil and/or oil products and dispersed it into small particles, but also stimulated growth of Rhodococcus erythropolis VKM AS-1339D, degraders of oil and oil products. Addition of 0.001-0.003% HMWA to a medium to be purified from oil products increased the extent of bacterial biodegradation by a factor of 1.1-5.0.