[Distribution Characteristics and Potential Ecological Hazards Assessment of Soil Heavy Metals in Typical Soil Profiles in Southeast Suburb of Beijing].

To investigate the distribution characteristics and the potential ecology risk of different types of heavy metals, soil samples were collected from various stratigraphic sections in the southeastern suburb of Beijing, where soil heavy metal (Cu, Pb, Cr, As) contents were measured and analyzed using multivariate statistical analysis and the potential ecological risk index method. The results showed that the concentrations of the four heavy metals followed the order of Cr > Cu > As > Pb with variable coefficients ranging from 59.60% to 159.33% at 3-6 m stratum, which all displayed a high degree of variability. The concentrations of Cu and Pb were positively correlated with soil organic matter (SOM), cation exchange capacity (CEC), etc, with higher eigenvalues in Factor 1 and 2, demonstrating the impact of organic colloid on the occurrence of heavy metals. The risk level of the specific heavy metal followed the order of As > Cu > Pb > Cr, where As already showed a medium potential ecological risk in the studied area.

[Application of Whole-cell Biosensor ADP1_pWHlux for Acute Toxicity Detection in Water Environment].

A whole-cell biosensor acinetobacter ADP1_pWHlux was constructed by genetic engineering for detecting acute toxicity, so as to overcome the harsh application conditions when detecting acute toxicity using natural luminescent bacteria or whole-cell biosensor constructed by model microorganisms as the host cell. Detection methods, detection sensitivity and detection range of acinetobacter ADP1_pWHlux were studied. The results showed that the luminescence of ADP1_pWHlux was inhibited by acute poison, poison dose and inhibition of luminescence exhibit dose-response relationship. ADPL_pWHlux was respond to 4 mg x L(-1) HgCl2 within 5 min. The detection limit for HgCl2 was 0.04 mg x L(-1). The detectable effects for indicators of Be2+, Ba2+, Cu2+, Ni2+ in standards for drinking water quality were obvious. The detection range of Be2+, Ba2+, Cu2+ were 0.025-250 mg x L(-1), the detection range of Ni2+, was 0.0025-250 mg x L(-1), the detection limit of Pb2+, BrO3(-) , ClO2(-) were 0.002 5 mg x L(-1), the detection limit of ClO3(-) was 0.025 mg x L(-1). The whole-cell biosensor ADPl_pWHlux detection method has been applied to evaluate acute toxicity in water environment of Qinghe river in Beijing, indicating the established method can be used to detect contaminated water samples.

[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.

[Effect of permeabilization on sulfate reduction activity of Desulfovibrio vulgaris Hildenborough cells in the presence of different electron donors].

The Desulfovibrio vulgaris Hildenborough (DvH) cells permeabilized with ethanol were used as biocatalysts to enhance hydrogenotrophic sulfate conversion. The effect of permeabilization extent of DvH cells on sulfate reduction was studied in the presence of different electron donors. When hydrogen was used as an electron donor, the highest level of sulfate reduction activity attained in cells treated with 10% ethanol (V/V), followed by 15% -ethanol treated cells. Furthermore, sulfate reduction activity markedly decreased when the ethanol concentration exceeded 15%. However, when lactate was used as the electron donor, the optimum ethanol concentration of the permeabilizing reagent was 20%, followed by 15% and 10%. Even when ethanol concentration reached 25%, DvH cells remained their partial activity with lactate. In a word, sulfate reduction activity of DvH cells responded differently in the presence of different donors. This was because the oxidation process of H2 and lactate occurred at different positions in DvH cells, and consequently intracellular electron transport pathway differed. To ensure the integrity of the electron transport chain between the donor and the accepter was a key factor for determining the permeabilization extent and for the application of cell permeabilization technology.

[Compositions and diagnostic ratios of heavily degraded crude oil residues in contaminated soil in oilfields].

The aims of this study were to determine the rate of degradation of crude oil in soil, to reveal the fingerprints of residual oil after long-term biodegradation, and to screen parameters for evaluation of the biodegradability residual oil. A total of 18 contaminated soil samples containing heavily degraded crude oil residuals from Daqing, Shengli and Baise oilfields were analyzed. More than 100 individual target compounds including straight-and branched-chain alkanes (n-alkanes, pristane and phytane), polycyclic aromatic hydrocarbons (PAHs), terpanes, steranes and triaromatic steranes (TAS) in residual oil were determined by gas chromatography-mass spectrometry (GC-MS). For all the soil samples, less than 10% and 30% of alkanes and PAHs remained in the residual oils relative to crude oils. Terpanes, steranes and TAS were found to be less biodegradable. Depletions decreased with increasing carbon number of n-alkanes. However, average depletions > 80% were found in n-alkanes with carbon numbers < 37. Average depletions were > 70% for 2-4 ring PAHs, while 5-6 ring PAHs were more resistant. Increase in alkylation level decreased depletion within homologues of naphthalene, phenanthrene, chrysene and Benzo[e] pyrene. GC-MS could only reveal less than 3% of the compounds of residual oils, which were mainly comprised of n-alkanes with carbon number > 20, alkylated naphthalenes and phenanthrenes, terpanes, steranes and TAS. Based on compositional characteristics of alkanes and PAHs in residual oils, 6 diagnostic ratios, which were ratios of susceptible compounds to resistant compounds or to the amounts residual oil, were proposed as the parameters for characterization of residual oils and determining the biodegradability of oils contaminated soils.

[The effects of aerobic exercise on cardiac output during exercise in patients with chronic heart failure].

OBJECTIVE: To observe the effects of aerobic exercise on cardiac output during exercise in patients with chronic heart failure (CHF). METHODS: A total of 50 CHF patients (echocardiography measured left ventricular ejection fraction < 0.49) were enrolled in the study and randomly divided into aerobic exercise group (n = 25) and control group (n = 25). Cardiopulmonary exercise testing (CPET) was performed. Patients of aerobic exercise group underwent aerobic exercise according to aerobic exercise prescription and exercise intensity is decided by anaerobic threshold before 10 J/s (1 minute before) of the oxygen consumption. After 6 supervised aerobic exercise training sessions in the hospital, patients were asked to perform the home-based aerobic exercise training. Patients in control group were required to maintain daily physical activities. CPET were reviewed 3 months later. RESULTS: Cardiac output (CO), peak CO, peak cardiac power output (peak CPO), resting heart rate (HR), heart rate at AT (HRAT), HR peak, resting mean arterial pressure (MAP), peak MAP at baseline were similar between aerobic exercise group and control [(4.2 ± 2.0) L/min vs. (3.3 ± 1.0) L/min, (6.2 ± 2.7) L/min vs. (5.2 ± 1.8) L/min, (1.8 ± 2.9) L/min vs. (2.0 ± 1.8) L/min, (1.3 ± 0.5) J/s vs. (1.2 ± 0.5) J/s, (76.8 ± 13.5) beats/min vs. (73.4 ± 11.9) beats/min, (91.5 ± 11.3) beats/min vs. (92.6 ± 12.4) beats/min, (106.0 ± 12.9) beats/min vs. (108.3 ± 17.4) beats/min, (80.8 ± 9.9) mm Hg (1 mm Hg = 0.133 kPa) vs. (87.6 ± 13.3) mm Hg, (98.8 ± 12.4) mm Hg vs. (102.7 ± 13.9) mm Hg, all P > 0.05]. Compared to baseline, CO, peak CO, peak CPO, HR, HRAT, HR peak, MAP, peak MAP after 3 months were similar between aerobic exercise group and control (all P > 0.05). The differences between baseline and 3 months later expressed as ΔCO, Δpeak CO, Δpeak CPO, ΔHR, ΔHRAT, ΔHR peak, ΔMAP, Δpeak MAP were also similar between aerobic exercise group and control group [(-0.7 ± 2.4) L/min vs. (0.7 ± 2.0) L/min, (1.1 ± 2.6) L/min vs. (1.4 ± 2.1) L/min, (0.1 ± 3.7) L/min vs. (-0.2 ± 2.5) L/min, (0.2 ± 1.0) J/s vs. (0.2 ± 0.5) J/s, (-0.4 ± 7.6) beats/min vs. (1.9 ± 9.9) beats/min, (3.4 ± 11.3) beats/min vs. (-2.8 ± 7.6) beats/min, (8.9 ± 14.5) beats/min vs. (3.7 ± 14.4) beats/min, (1.5 ± 12.8) mm Hg vs. (-1.3 ± 11.1) mm Hg, (6.4 ± 18.9) mm Hg vs. (1.3 ± 12.3) mm Hg, all P > 0.05]. CONCLUSION: Three months aerobic exercise training did not improve cardiac output and related parameters during exercise in this cohort patients with CHF.

[Effects of aerobic exercise on exercise tolerance in patients with chronic heart failure].

OBJECTIVE: To explore the effects of aerobic exercise on exercise tolerance in patients with chronic heart failure (CHF). METHODS: A total of 50 CHF patients with left ventricular ejection fraction (LVEF) < 49% by echocardiography were enrolled. And they were randomly divided into exercise group (n = 25) and non-exercise group (n = 25). Cardiopulmonary exercise testing (CPET) was performed. The patients of exercise group underwent an aerobic exercise program in which exercise intensity was decided by anaerobic threshold (AT) before 10 J/s while those of non-exercise group performed daily activities. After 6 sessions of supervised aerobic exercise, the home-based aerobic exercise training began. CPET was re-examined 3 months later. RESULTS: The VO(2) AT, VO(2) peak, Load AT, Load peak, peak VO(2)/HR and VE/VCO(2) slope at baseline were similar between exercise group and non-exercise group (P > 0.05). The VO(2) AT, VO(2) peak, Load AT, Load peak and peak VO(2)/HR in patients of exercise group were increased compared with baseline, The differences between baseline and 3 months later expressed as ΔVO(2) AT, ΔVO(2) peak, ΔLoad AT, ΔLoad peak, Δpeak VO(2)/HR and ΔVE/VCO(2) slope, The differences of ΔVO(2) AT, ΔVO(2) peak, ΔLoad AT, ΔLoad peak and Δpeak VO(2)/HR between two groups were statistically significant [ΔVO(2) AT: 2.8 (1.2 - 3.5) ml×kg(-1)×min(-1) vs -0.3 (-2.8 - 0.1) ml×kg(-1)×min(-1), P < 0.01; ΔVO(2) peak: 3.4 (1.8 - 4.6) ml×kg(-1)×min(-1) vs -0.5 (-1.4 - 0.3) ml×kg(-1)×min(-1), P < 0.01; ΔLoad AT:15.0 (2.5 - 22.5) J/s vs 0.5(-4.2 - 3.8) J/s, P < 0.01; ΔLoad peak: 15.0 (1.3 - 25.0) J/s vs 0.0 (-8.8 - 15.0) J/s, P < 0.05; Δpeak VO(2)/HR: 2.3 (0.0 - 4.0) ml×kg(-1)×beat(-1) vs -0.1 (-0.7 - 1.2) ml×kg(-1)×beat(-1), P < 0.01]. The difference of ΔVE/VCO(2) slope was not statistically significant [-2.3 (-12.2 - 1.8) vs 1.0 (-0.4 - 2.6), P > 0.05]. CONCLUSION: After 3 months of aerobic exercise, exercise capacity may improve in the CHF patients.

[Groundwater pollution risk mapping method].

Based on methods for groundwater vulnerability assessment not involving in contamination source elements, and lack of the systemic and effective techniques and parameter system on groundwater pollution risk mapping in present, through analyzing the structure of groundwater system and characteristics of contaminant sources, and coupling groundwater intrinsic vulnerability with contaminant sources, the integrated multi-index models were developed to evaluate the risk sources of groundwater contaminant and form the groundwater pollution risk mapping in this paper. The models had been used to a large-scale karst groundwater source of northern China as a case study. The results indicated that vulnerability assessment overlaid risk pollution sources of groundwater could effectively confirm the high risk regions of groundwater pollution, and the methods might provide necessary support for the supervision of groundwater pollution.

[Performance of a combined bio-chemical sulfidogenic system and microbial characteristics in the presence of H2].

To study and evaluate the performance of the continuously-operated autohydrogenotrophic sulfate reduction technique enhanced with electrochemical method and to improve the sulfate removal efficiency, a combined bio-electrical sulfidogenic system was developed with a three-dimensional bio-cathode. Sulfate reduction rate was elevated markedly owing to H2 mass transfer enhancement, biomass augmentation and electrical field stimulation. Indeed, when a current of 0.50 mA was applied to the system, the average sulfate removal load was 1.94 g/(L x d) during the stable running status and the maximum removal load was 2.23 g/(L x d). Furthermore, the combined bio-electrical system was comparatively more stable in terms of response to the variation of influx load under the same hydraulic conditions. Results of SEM showed that besides the bacteria attached on the surface of the hollow fiber, large amount of biomass was aggregated on the surface and the inner gridding space of the graphite felt. PCR-DGGE analysis indicated that the diversity of the microbial community structure was slightly reduced resulting in an optimized one. The dominant genera were Desulfovibrio and Desulfomicrobium. Enhanced H2 mass transfer, biomass augmentation, optimized microbial community structure and electrical stimulation were the key important factors for the high sulfate reduction efficiency of the system.

[Bio-electrochemical effect on hydrogenotrophic sulfate reduction stimulated by electrical field in the presence of H2 under atmospheric pressure].

Microbial sulfate reduction rate is limited with H2 as electron donor. In order to improve hydrogenotrophic sulfate reduction under normal atmospheric H2 pressure, a bio-electrochemical system with direct current was designed and performed in this study. Results indicates that sulfate reduction rate (SRR) increases with the augment of current intensity under lower current intensity (I < or = 1.50 mA). When optimum current intensity of 1.50 mA is applied, the SRR is 1.7 to 2.1 times higher than that of the control reactor. The synergistic effect of electrochemistry and microbiology on sulfate reduction varies at different current intensity. Under the condition of I < or = 1.50 mA, the most probable mechanism of SRR increase is that electric or magnetic field stimulates the proliferation of sulfate-reducing bacteria (SRB) and the activity of the enzymes. When I is higher than 1.50 mA, the activity of SRB is inhibited, resulting in lower reduction rate compared with that at lower current. If controlling the cathode potential lower than -0.69 V and H2 partial pressure 1.01 x 10(5) Pa, electro-catalytic sulfate reduction process takes place with H2 as reductant in this bio-electrochemical system. However, the overall reduction rate is still lower than that when I = 1.50 mA is applied, and additionally the energy consumption is much higher. Therefore, electric field of low intensity can enhance hydrogenotrophic sulfate reduction in the presence of H2 under atmospheric pressure.

[Microbial community constitute and phylogenetic analysis on oil polluted soils in oilfields of China].

The microbial communities in oil polluted soils from oilfields of China were analyzed using a modern molecular biological approach. The crude total DNA from soils were directly extracted, 16S rDNA fraction were amplified by PCR, the bands were separated using denaturing gradient gel electrophoresis (DGGE), and some of the typical bands were sequenced and compared with the records of NCBI to classify the germs. Comparison of the DNA extraction indicated that the yields were 1.4-2.2 times as much as the existing technique, and the DNA purity reached 1.8-2.0. With higher similarity and correlation in CQ and DQ oilfields but lower in that of SL and YM oilfields, the influence factors to microbial communities consisted in the elementary properties of soil samples such as oil contents, water ratio, etc. Extraction and sequencing analysis of selected 16S rDNA bands demonstrated a range of similarity of 89%-100% to reference bacteria. The Shannon-Weiner index of the oil contaminated soils was 0.5-1.2, and which was increased slightly along with the enhancement of microbial amounts and FDA activities. According to this research, it has possibility in developing a reliable tool for researching oil contaminated soil bacteria diversity, and in applying a credible foundation for adjusting the microbial ecosystem and determining the dominant community in contaminated soils in oilfields.

[Performance of slow-release organic carbon-source (SOC) materials for in-situ biological denitrification in groundwater].

As lack of electron donor (carbon source) is a key problem of in-situ denitrification in groundwater, slow-release organic carbon-source (SOC) materials were produced as appropriate electron donor in denitrification PRB. GPVAS and GEPVAS series were manufactured by blending starch and PVA together, with alpha-amylase as the additive, and their performance was detected through SEM and static batch experiments. The results showed that PVA formed the framework filling with starch molecule, and the carbon releasing process followed the law of second order kinetics. Equilibrium concentration of COD (c(m)) and release rate coefficient (k) were key factors of kinetics evaluation. Both c(m) and k of GPVAS-40 were the lowest. The influence of alpha-amylase to the performance of SOC materials was remarkable. The c(m) values would ascend rapidly with augmenting of alpha-amylase content, while the releasing speed rose when amylase activity was lower than 0.03 U/g and then decreased. Consequently, the releasing process was controllable through changing the content of starch and activity of alpha-amylase to meet needs of different situations and pollution of groundwater and improve the effect of in-situ nitrate removal.

Sensitivity of key factors and uncertainties in health risk assessment of benzene pollutant.

Predicting long-term potential human health risks from contaminants in the multimedia environment requires the use of models. However, there is uncertainty associated with these predictions of many parameters which can be represented by ranges or probability distributions rather than single value. Based on a case study with information from an actual site contaminated with benzene, this study describes the application of MMSOILS model to predict health risk and distributions of those predictions generated using Monte Carlo techniques. A sensitivity analysis was performed to evaluate which of the random variables are most important in producing the predicted distributions of health risks. The sensitivity analysis shows that the predicted distributions can be accurately reproduced using a small subset of the random variables. The practical implication of this analysis is the ability to distinguish between important versus unimportant random variables in terms of their sensitivity to selected endpoints. This directly translates into a reduction in data collection and modeling effort. It was demonstrated that how correlation coefficient could be used to evaluate contributions to overall uncertainty from each parameter. The integrated uncertainty analysis shows that although drinking groundwater risk is similar with inhalation air risk, uncertainties of total risk come dominantly from drinking groundwater route. Most percent of the variance of total risk comes from four random variables.

[Uncertainty analysis of health risk assessment caused by benzene contamination in a contaminated site].

Lots of uncertainties lie in the procedure of environmental risk assessment (ERA) and how to analyze them exactly is studied comprehensively. Based on the investigation of petroleum contamination in a contaminated site, the representative benzene contaminant in soil was selected to analyze uncertainty of environmental risk resulting from drinking and inhalation exposure routes, using the Monte-Carlo simulations. According to the analysis results, the total health risk average value caused by benzene contamination from the alkene factory is 1.18 x 10(-4) for the people living on the district A, which is more than the risk limit of U.S. EPA 10(-6) and means contamination hazard to health. In four different areas of the alkene factory, the main source of risk comes from the cracking equipments with 1.17 x 10(-4). With the impact factors of the uncertainty, the contamination harm to the human health's probability is different referring to the different risk level, which is a criteria value meaning no harm to health issued by different institution. The study results provide an important foundation of effective control and remediation actions of contaminated sites.

[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.

[Relationships between loading rates and nitrogen removal effectiveness in subsurface constructed wetlands].

About forty kinds of nitrogen loading removal rate were studied in field in 15 months, inflow and outflow loading rules of reeds/Zizania caduciflora/mixing and no-plant bed were discussed in different inflow loading. The four kinds SFS inflow loading changed from 400 mg x (m2 x d)(-1) to 8 000 mg x (m2d)(-1), while outflow loading is less than 7,000 mg (m2 d)(-1). Results show that outflow loading increase with the increase of inflow loading, linear relation is obvious. Total nitrogen removal rate has the same trend at low inflow loading. But in high inflow loading TN removal rate has much variation. The system had better run between 2,000 mg x (m2 x d)(-1) and 4,000 mg x (m2 x d)( -1) inflow loading. Average removal rate in between 1062 mg x (m2 x d)(-1) and 2 007 mg x (m2 x d)(-1). Plant SFS removal rate is better than no-plant SFS. TN removal rate of reed and zizania caduciflora bed is 63 % and 27 % higher than no-plant bed. Plant harvesting is unimportant and contributes less than 5% of TN removal loading, plant can improve system microenviroment and hydrology condition which could increase TN removal rate. The results provided deep insight to SFS nitrogen removal and reference to SFS design.

[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.