Germination of grass species in soil affected by crude oil contamination

Many grass species exist in the oil exploration areas of North Dakota. The objective of this study was to evaluate seed germination of 65 grass species affected by crude oil. Germination of all species was reduced by crude oil, ranging from 4.3 to 100%. Twenty-eight species were tolerant, 29 moderately tolerant, 6 moderately sensitive, and 2 sensitive. Based on the tolerance levels, the following were used to further test the dose response to crude oil: strong creeping red fescue (Festuca rubra L. ssp. rubra), perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), buffalograss [Buchloe dactyloides (Nutt.) Engelm.], little bluestem [Schizachyrium scoparium (Michx.) Nash], witchgrass (Panicum capillare L.), sand dropseed [Sporobolus cryptandrus (Torr.) Gray], Johnsongrass [Sorghum halepense (L.) Pers.], and smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.]. The EC₅₀ of germination and biomass was effective in ranking the 9 species. Buffalograss, sand dropseed, and orchardgrass were ranked as the most tolerant species with EC₅₀ values of 0.1, > highest concentration tested, 0.05 m³ m^?3 (P < 0.05), respectively. Smooth crabgrass and little bluestem were ranked as most sensitive with EC₅₀ values of 0.03 and 0.04 m³ m^?3 (P < 0.05), respectively. Buffalograss showed the lowest germination (10.4%) and biomass reduction (25%) (P < 0.05).     

四种园林植物对土壤镉污染的耐受性

采用模拟Cd污染土壤培养法,测定了Cd胁迫下山矾、桑树、绣线菊、山茶4种园林植物幼苗的生长、生物量变化,根茎叶的Cd含量,光合色素含量与MDA含量,对耐性指数(Ti)、转移系数(TF)、生物富集系数(BCF)进行了评价。结果表明:(1)山矾、桑树、绣线菊和山茶的平均耐性指数分别为93.99、82.33、82.10和87.25;(2)4个树种幼苗根茎叶的Cd含量都随着Cd处理浓度的增加而增加,转移系数值(TF)都小于1,转移能力为山矾山茶绣线菊桑树。对Cd累积能力为山矾山茶桑树绣线菊;山矾和山茶生物量吸收的Cd总量显著高于绣线菊和桑树。(3)Cd处理浓度的不断增加,叶绿素a/叶绿素b比值与对照相比变化不显著,类胡萝卜素的含量持续增加;桑树、山茶、山矾和绣线菊MDA含量分别平均上升为15%、10.17%、9.69%、12.86%。不同Cd浓度下,MDA上升幅度顺序为桑树绣线菊山茶山矾。研究表明山矾具有很高的Cd耐性、转移能力、以及地上部分积累镉的能力,是一种抗Cd污染较好的园林绿化树种。     

原油污染对黄绵土和风沙土水分入渗的影响

原油进入土壤后会堵塞土壤孔隙,影响土壤斥水性,改变土壤水分运动状况.本研究利用土柱模拟的方法,研究了不同原油污染程度(0、0.5％、1％、2％、4％)对黄绵土和风沙土水分入渗过程的影响.结果 表明:随着原油含量的增加,两种土壤湿润锋的推进速度和入渗速率均减小,土壤原油污染程度为4％时湿润锋运移到土柱底部的所需时间最长,...     

Porous biocarrier-enhanced biodegradation of crude oil contaminated soil

Soil contamination with crude oil from petrochemicals and oil exploitation is an important worldwide issue. Comparing available remediation techniques, bioremediation is widely considered to be a cost-effective choice; however, slow degradation of crude oil is a common problem due to the low numbers of bacteria capable of degrading petroleum hydrocarbons and the low bioavailability of contaminants in soil. To promote crude oil removal, biocarrier for immobilization of indigenous hydrocarbon-degrading bacteria was developed using porous materials such as activated carbon and zeolite. Microbial biomass reached 10¹⁰ cells g^?1 on activated carbon and 10⁶ cells g^?1 on zeolite. Total microbial and dehydrogenase activities were approximately 12 times and 3 times higher, respectively, in activated carbon than in zeolite. High microbial colonization by spherical and rod shapes were observed for the 5–20 μm thick biofilm on the outer surface of both biocarriers using electronic microscopy. Based on batch-scale experiments containing free-living bacterial cultures and activated carbon biocarrier into crude oil contaminated soil, biocarrier enhanced the biodegradation of crude oil, with 48.89% removal, compared to natural attenuation with 13.0% removal, biostimulation (nutrient supplement only) with 26.3% removal, and bioaugmentation (free-living bacteria) with 37.4% removal. In addition, the biocarrier increased the bacterial population to 10⁸ cells g^?1 dry soil and total microbial activity to 3.5 A₄₉₀. A hypothesis model was proposed to explain the mechanism: the biocarrier improved the oxygen, nutrient mass transfer and water holding capacity of the soil, which were the limiting factors for biodegradation of non-aqueous phase liquid (NAPL) contaminants such as crude oil in soil.Scientific relevanceThis study explored the role of biocarrier in enhancing biodegradation of hydrophobic contaminants such as crude oil, and discussed the function of biocarrier in improving oxygen mass transfer and soil water holding capacity, etc.     

Enhanced crude oil biodegradation in soil via biostimulation

Research on feasible methods for the enhancement of bioremediation in soil contaminated by crude oil is vital in oil-exporting countries such as Kuwait, where crude oil is a major pollutant and the environment is hostile to biodegradation. This study investigated the possibility of enhancing crude oil bioremediation by supplementing soil with cost-effective organic materials derived from two widespread locally grown trees, Conocarpus and Tamarix. Amendments in soils increased the counts of soil microbiota by up to 98% and enhanced their activity by up to 95.5%. The increase in the biodegradation of crude oil (75%) and high levels of alkB expression substantiated the efficiency of the proposed amendment technology for the bioremediation of hydrocarbon-contaminated sites. The identification of crude-oil-degrading bacteria revealed the dominance of the genus Microbacterium (39.6%), Sphingopyxis soli (19.3%), and Bordetella petrii (19.6%) in unamended, Conocarpus-amended, and Tamarix-amended contaminated soils, respectively. Although soil amendments favored the growth of Gram-negative bacteria and reduced bacterial diversity, the structures of bacterial communities were not significantly altered.     

Biodegradation of crude oil by soil microorganisms in the tropic

Five microorganisms, three bacteria and two yeasts, capable of degrading Tapis light crude oil were isolated from oil-contaminated soil in Bangkok, Thailand. Soil enrichment culture was done by inoculating the soil in mineral salt medium with 0.5% v/v Tapis crude oil as the sole carbon source. Crude oil biodegradation was measured by gas chromatography method. Five strains of pure microorganisms with petroleum degrading ability were isolated: three were bacteria and the other two were yeasts. Candida tropicalis strains 7Y and 15Y were identified as efficient oil degraders. Strain 15Y was more efficient, it was able to reduce 87.3% of the total petroleum or 99.6% of n-alkanes within the 7-day incubation period at room temperature of 25 ± 2 °C.     

Microbial biosurfactant mediated removal and/or solubilization of crude oil contamination from soil and aqueous phase: An approach with Bacillus licheniformis MTCC 5514

This study highlights the role of marine microbial biosurfactants on solubilization/removal of crude-oil contamination from four different soils in an aqueous phase. Soil of four different types, viz., sandy, fine sand soil, clay, and clay loam, were collected and saturated with crude oil. Marine isolate MTCC 5514 (Bacillus licheniformis) was chosen for the study and comparisons were made with synthetic surfactants and commercially available biosurfactant. In-situ studies were carried out with different percentages of crude oil to assess the growth and the percentage removal of oil. For ex-situ studies, soils were pre-saturated with crude oil and then treated with the chosen biosurfactant at a 10% concentration level using flask and column methods. After time intervals of 30–120 min, samples were collected and then subjected to extraction with hexane and the percentage removal was calculated. Results revealed, at 2% concentration of crude oil, that complete solubilization was achieved. With regard to ex-situ studies, clay soil absorbed the maximum percentage of oil compared to other soil types, and with regard to the removal, all the synthetic surfactants showed <60% removal irrespective of soil type. In the case of biosurfactants even at 10% concentration, >85% removal was achieved.     

GC/MS-SCAN to follow the fate of crude oil components in bioreactors set to remediate contaminated soil

In this paper GC/MS-SCAN was used to identify the crude oil components that persist after bioremediation treatment of contaminated soil and the metabolites generated during this process. The soil was treated in bioreactors inoculated with an adapted bacterial population. In the first of two sets of conditions used, the water phase of the reactor was circulated continuously at a flow rate of 7 l day⁻¹, and in the other case, it was circulated for a short period once a day to give the equivalent of 0.5 l day⁻¹. Data showed that acyclic, n- and substituted alkanes C₁₂ were still present after one year of remediation, while the majority of substituted derivatives of polycyclic and aromatic hydrocarbons could not be detected by GC/MS-SCAN analysis. The number of components identified was about one-half of that initially observed. After treatment the same number of components was detected at the top and bottom of the reactor in which the water phase was circulated continuously, whereas a smaller number of metabolites were observed at the top rather than at the bottom of the reactor with discontinuous circulation. The analysis has pointed to the importance of n-alkanes, their substituted derivatives and polycyclic aromatic hydrocarbons as the most significant pollutants.     

The occurrence of fin rot in mullet (Mugil cephalus) associated with crude oil contamination of an estuarine pond-ecosystem

Four estuarine pond-ecosystems equipped with tidal simulation were established and stocked with mullet, shrimp, and oysters. A 6 month pre-spill sampling period established a consistently low incidence of disease in the mullet, Mugil cephalus , from all ponds. Following the preliminary study period, Empire Mix crude oil (4.0-5.0 p.p.m.) was spilled on each of two of the ponds in mid-July, 1974. Six to eight days following the oil spill all the mullet examined from the treated ponds had varying degrees of fin rot on one or more of their fins. The fin erosion involved primarily the caudal, pectoral, and pelvic fins with the caudal fin the most severely damaged. The degree of damage to the fins varied from a slight discoloration with no visible fraying to complete erosion of all of the fin elements. A gram negative rod tentatively identified as Vibrio sp. is considered the primary pathogen responsible for the fin erosion. Although the condition of the infected fish indicated the possibility of a systemic infection, only a low percentage of the kidney cultures taken from the diseased fish were positive indicating the infection was mostly external. The course of the infection was documented over a 56-day period following the oil spill. Significantly, 96% of the mullet observed from the treated ponds had some degree of fin damage while only 6 % of those observed from the control ponds had eroded fins. The high incidence of fin rot which occurred in the estuarine-pond ecosystems did not occur during numerous acute exposures of mullet to crude oil in the laboratory.     

Influence of crude oil contamination on the bacterial community of semiarid soils of Patagonia (Argentina)

Autochthonous bacteriocenoses in semiarid soils in Patagonia were found to be capable of rapidly adapting to high contamination with crude oil. This adaptation at community level is due to the selective enrichment of hydrocarbon‐utilizing bacteria always present in these soils. Immediately after a heavy contamination with crude oil, the authochthonous bacteriocenosis contained about 28% hydrocarbon‐utilizing bacteria which could be classified into eight ecotypes with characteristic metabolic profiles. Mainly n‐alkanes were used as growth substrates of representative strains. After seven months' exposure to crude oil, the bacteriocenosis consisted almost entirely of hydrocarbon‐utilizing bacteria. At least fourteen ecotypes were distinguishable, and the majority of representative strains were able to metabolize a broad spectrum of aliphatic and aromatic hydrocarbons. Corresponding to the significant alteration of the physiological diversity, drastic changes to the taxonomic diversity were also found. Whereas at the beginning of the study the autochthonous bacteriocenoses were dominated by GRAM ‐positive genera of the Actinomycetales (Dietzia, Gordona, Nocardia, Rhodococcus, Streptomyces) with high ecological potency, after just two months' exposure to crude oil, GRAM ‐ negative bacteria (especially Pseudomonas stutzeri) became predominant within the hydrocarbon‐utilizing bacteriocenoses accompanied by some GRAM ‐positive genera of the Actinomycetales with a significantly lower abundance. These findings underline the importance of Pseudomonas and some genera of Actinomycetales for processes of natural attenuation and the technically supported in situ bioremediation of soil polluted by crude oil in Patagonia.     

Biostimulation potential of biochar for remediating the crude oil contaminated soil and plant growth

Crude oil contamination is a serious environmental threat to soil and plants growing in it. Biochar has the potential of biostimulation for remediation of crude oil-contaminated soil. Therefore, the current research was designed to analyze the bio-stimulatory impact of biochar for remediating the crude oil contaminated soil (10%, and 15%), and growth of maize under glasshouse conditions. Biochar was produced by pyrolysis of Australian pines at 350 °C. Soil incubations were done for 20 days. The results of soil analysis showed that the crude oil degradation efficiency of biochar was 34%. The soil enzymatic activities had shown 38.5% increase in fluorescein diacetate (FDA) hydrolysis and 55.6% increase in dehydrogenase activity in soil incubated with biochar in comparison to control. The soil microbial diversity was improved to 41% in biochar treated soil with respect to untreated one, while microbial respiration rate had shown a 33.67% increase in soil incubated with biochar with respect to control under oil stress. Gas Chromatography Mass spectrometry (GC-MS) analysis had shown the high content of low molecular weight hydrocarbons (C₉-C₁₃) in the soil incubated with biochar in comparison to untreated soil. Biochar showed a significant increase in fresh and dry biomass (25%, 14.61%), leaf area (10%), total chlorophyll (11%), water potential (21.6%), osmotic potential (21%), and membrane stability index (12.7%). Moreover, biochar treatment showed a higher increase in the contents of proline (29%), total amino acids (18%), soluble sugars (30.4%), and antioxidant enzymes like superoxide dismutase (16.5%), catalase (11%), and peroxidase (12%). Overall, the results of the present study suggest the bio-stimulating potential of biochar for degradation of hydrocarbons in crude oil contaminated soil and their growth-stimulating effects on maize.     

Responses of bioaugmented ryegrass to PAH soil contamination

The physiological and biochemical responses of ryegrass (Lolium multiflorum) to PAH induced stress in soils contaminated with phenanthrene and pyene were investigated, in the presence of PAH-degrading bacteria (Acinetobacteria junii) or arbuscular mycorrhizal fungi (AM fungi, Glomus mossae). The parameters monitored included chlorophyll content, chlorophyll a/b ratio, soluble-carbohydrate content, soluble-protein, malondialdehyde and electrolyte leakage, and superoxide dismutase (SOD) and peroxidase (POD) activities. Ryegrass showed good resistance and acclimation to PAH stress in soil, however, PAH contamination resulted in adverse effects such as damage of photosynthetic function and acceleration of shoot senescence. At PAH level of 100 mg kg(-1), chlorophyll contents were 14% lower than control (no PAH). Activities of SOD and POD were more sensitive indicators of PAH stress as compared to other parameters. However, all parameters showed trends based on either the bioaugmentation of the plants or PAH treatment level. It was concluded that the inoculation of AMF and PAH-degrading bacteria, especially the former, have a positive effect on alleviation of PAH toxicity to ryegrass plants. Furthermore, the inoculation of AMF increased the shoot and biomass of ryegrass by 11-19% and 18-78%, respectively. Bioaugmented ryegrass plants show promise as a host plants in the phytoremediation of PAH contaminated soils.     

Tolerance of soil flagellates to increased NaCl levels

The ability of heterotrophic flagellates to survive and adapt to increasing salinities was investigated in this study. Whole soil samples were subjected to salinities corresponding to marine conditions and clonal cultures were used to perform growth and adaptation experiments at a wide range of different salinities (0-50 ppm). More morphotypes tolerant to elevated NaCl levels were found in road verge soil that was heavily exposed to de-icing salt than in less exposed soils, though there were fewer tolerant than intolerant morphotypes in all soils examined. Heterotrophic flagellates isolated on a freshwater medium from a non-exposed soil were unable to thrive at salinities above 15 ppt, and showed reduced growth rates even at low salt salinities (1-5 ppt). The findings suggest that heterotrophic soil flagellates are less tolerant to NaCl than their aquatic relatives, possibly due to their long evolutionary history in soil, and support the idea that identical morphospecies may differ considerably with respect to physiology     

The role of indigenous bacterial and fungal soil populations in the biodegradation of crude oil in a desert soil

The biodegradation capacity of indigenous microbial populations was examined in a desert soil contaminated with crude oil. To evaluate biodegradation, soil samples supplemented with 5, 10 or 20% (w/w) of crude oil were incubated for 90 days at 30 °C. The effect of augmentation of the soil with vermiculite (50% v/v) as a bulking agent providing increased surface/volume ratio and improved soil aeration was also tested. Maximal biodegradation (91%) was obtained in soil containing the highest concentration of crude oil (20%) and supplemented with vermiculite; only 74% of the oil was degraded in samples containing the same level of crude oil but lacking vermiculite. Gas chromatograms of distilled fractions of crude oil extracted from the soil before and after incubation demonstrated that most of the light and part of the intermediate weight fractions initially present in the oil extracts could not be detected after incubation. Monitoring of microbial population densities revealed an initial decline in bacterial viable counts after exposure to oil, presumably as a result of the crude oil’s toxicity. This decline was followed by a steep recovery in microbial population density, then by a moderate increase that persisted until the end of incubation. By contrast, the inhibitory effect of crude oil on the fungal population was minimal. Furthermore, the overall increased growth response of the fungal population, at all three levels of contamination, was about one order of magnitude higher than that of the bacterial population.     

Tolerance of soil bacterial complexes to salt shock

Investigations showed that bacteria present in soil are resistant to one-day exposure to a saturated solution of ammonium nitrate and can well develop when transferred to laboratory nutrient media. The evaluated number of bacteria in NH4NO3-treated soil samples was nearly the same as in native soil samples, while was 1.5-2.5 times smaller in the former than in the latter case when microbial succession in the soil samples was initiated by wetting them. Bacteria (particularly gram-negative ones) occurring at the early stages of succession were the most sensitive to salt stress. Bacteria in soil were found to be much more resistant to salt stress than the same bacteria isolated in pure cultures.     

Mycoremediation of crude oil contaminated soil by specific fungi isolated from Dhahran in Saudi Arabia

Crude oil biodegrading microorganism considers the key role for environmental preserving. In this investigation, crude oil biodegrading fungal strains have been isolated in polluted soil of crude-oil at khurais oil ground in Kingdom of Saudi Arabia. Among of 22 fungal isolates, only three isolates reflected potential capability for oil degradation. These isolates were identified and submitted to GenBank as (A1) Aspergillus polyporicola (MT448790), (A2) Aspergillus spelaeus (MT448791) and (A3) Aspergillus niger (MT459302) through internal-transcribed spacer-regions (ITS1&ITS2) for sequencing in molecular marker. Comparing with controls, strain (A1) Aspergillus niger was superior for biodegradation ability (58%) comparing with Aspergillus polyporicola and Aspergillus spelaeus degrading were showed 47 and 51% respectively. Employed CO₂ evolution as indicator for petroleum oil biodegradation by the fungal isolates reflected that, Aspergillus niger emission highest CO2 (28.6%) comparing with Aspergillus spelaeus and Aspergillus polyporicola which showed 13% and 12.4% respectively. capability of Aspergillus sp. to tolerate and adapted oil pollutants with successful growth rate on them, indicated that it can be employed as mycoremediation agent for recovering restoring ecosystem when contaminated by crude oil.     

原油和消油剂对鱼类毒性的研究进展

原油对鱼类的毒性主要来自其水溶性成分,可导致鱼卵死亡或发育畸形,并造成鱼类麻痹、发炎、粘膜受损和死亡。消油剂的使用在分散了油膜的同时也带来二次污染,其活性剂对鱼类产生新的毒性影响。消油剂将原油分散为乳化颗粒并能进入鱼体内,加大了原油的毒性并延长其作用时间。综述了原油和消油剂对鱼类毒性的研究进展,展望了鱼类在相关毒性试验领域的应用及发展方向。     

The phosphate status of garden soils in relation to soil pH

Summary The phosphate status of 800 garden soils, obtained from various parts of the United Kingdom, as determined by the Morgan extraction method is presented in relation to soil pH.74%–95% of the soils of pH 5 to 5.5, 29%–46% of the soils of pH 6 to 6.5, and 17%–18% of the soils of pH 7 to 8 had a low phosphate status.11%–19% of the soils of pH 6.5 to 8 had a very high phosphate status, indicating over-manuring with respect to phosphate fertilisers.There are indications that the Morgan method is not entirely satisfactory for determining phosphate availability in soils of pH 5.5 or less.