ArticlePublisher preview available

Combining stable carbon isotope analysis and petroleum-fingerprinting to evaluate petroleum contamination in the Yanchang oilfield located on loess plateau in China

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

This study evaluated petroleum contamination in the Yanchang (Shaanxi Yanchang Petroleum (Group) Co., Ltd.) oilfield, located in the loess plateau region of northern Shaanxi, China. Surface soil and sediment samples were collected from the wasteland, farmland, and riverbed in this area to assess the following parameters: total petroleum hydrocarbon (TPH), n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and carbon isotope ratios (δ¹³C). The results showed that TPH and PAH levels in the study area were 907–3447 mg/kg and 103.59–563.50 μg/kg, respectively, significantly higher than the control samples (TPH 224 mg/kg, PAHs below method quantification limit, MQL). Tests using δ¹³C to detect modified TPH (2238.66 to 6639.42 mg/kg) in the wastelands adjacent to the oil wells revealed more significant contamination than tests using extraction gravimetric analysis. In addition, “chemical fingerprint” indicators, such as low to high molecular weight (LMW/HMW) hydrocarbons, carbon preference index (CPI), and pristine/phytane (Pr/Ph), further confirmed the presence of heavy petroleum contamination and weathering. This has resulted in a nutrient imbalance and unsuitable pH and moisture conditions for microbial metabolic activities. This study evaluates petroleum contamination, which can inform contamination remediation on a case by case basis.
This content is subject to copyright. Terms and conditions apply.
RESEARCH ARTICLE
Combining stable carbon isotope analysis
and petroleum-fingerprinting to evaluate petroleum
contamination in the Yanchang oilfield located
on loess plateau in China
Yiping Wang
1
&Jidong Liang
1,2
&Jinxing Wang
1
&Sha Gao
1,3
Received: 23 April 2017 /Accepted: 17 October 2017 /Published online: 15 November 2017
#Springer-Verlag GmbH Germany 2017
Abstract This study evaluated petroleum contamination in
the Yanchang (Shaanxi Yanchang Petroleum (Group) Co.,
Ltd.) oilfield, located in the loess plateau region of northern
Shaanxi, China. Surface soil and sediment samples were col-
lected from the wasteland, farmland, and riverbed in this area
to assess the following parameters: total petroleum hydrocar-
bon (TPH), n-alkanes, polycyclic aromatic hydrocarbons
(PAHs), and carbon isotope ratios (δ
13
C). The results showed
that TPH and PAH levels in the study area were 9073447 mg/
kg and 103.59563.50 μg/kg, respectively, significantly
higher than the control samples (TPH 224 mg/kg, PAHs be-
low method quantification limit, MQL). Tests using δ
13
Cto
detect modified TPH (2238.66 to 6639.42 mg/kg) in the
wastelands adjacent to the oil wells revealed more significant
contamination than tests using extraction gravimetric analysis.
In addition, Bchemical fingerprint^indicators, such as low to
high molecular weight (LMW/HMW) hydrocarbons, carbon
preference index (CPI), and pristine/phytane (Pr/Ph), further
confirmed the presence of heavy petroleum contamination
and weathering. This has resulted in a nutrient imbalance
and unsuitable pH and moisture conditions for microbial met-
abolic activities. This study evaluates petroleum contamina-
tion, which can inform contamination remediation on a case
by case basis.
Keywords Total petroleum hydrocarbon (TPH) .N-alkanes .
Polycyclic aromatic hydrocarbons (PAHs) .Carbon isotope
ratios (δ
13
C) .Loess
Introduction
The Yanchang oilfield is located in the loess plateau region in
the northern part of Shaanxi, China. In the past 20 years, pe-
troleum production from this field has increased rapidly, from
one million tons to more than 12 million tons per year.
Yanchang has become one of the most important energy pro-
duction bases in China. Unfortunately, environmental pollu-
tion has accompanied this petroleum extraction, leading to the
accumulation of persistent petroleum compounds in the envi-
ronment. Further, soil erosion is a serious problem in the
Loess Plateau, due to its fragile ecosystem. As a result, con-
taminated soils can become a pollution source, allowing con-
taminants to spread on a large scale. There have been few
reports about petroleum contamination in this area.
Therefore, petroleum pollution investigations are needed to
drive prompt risk management and petroleum contamination
remediation.
Petroleum is a complex mixture, composed of alkanes,
aromatics, resins, asphaltenes, and other organic matter
(Salanitro et al. 1997). Some petroleum compounds are
known to have carcinogenic, mutagenic, and teratogenic ef-
fects. As such, many countries have classified petroleum as a
type of hazardous compound (Huang et al. 2016,Zhouetal.
Responsible editor: Zhihong Xu
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s11356-017-0500-6) contains supplementary
material, which is available to authorized users.
*Jidong Liang
jidongl@mail.xjtu.edu.cn
1
Department of Environmental Engineering, Xian Jiaotong
University, Xian 710049, China
2
State Key Laboratory of Loess and Quaternary Geology, Institute of
Earth Environment, Chinese Academy of Sciences, Xian 710061,
China
3
Department of Environmental Science, Changan University,
Xian 710054, China
Environ Sci Pollut Res (2018) 25:28302841
https://doi.org/10.1007/s11356-017-0500-6
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Petroleum products wide spread in cold climate regions, such as northeast China, Canada, and Russia, which led to many petroleum hydrocarbons' contamination sites in these high latitude areas with low temperature. For example, the soil and river sediments in Yanchang Oilfield, located in the cold gully region of the Loess Plateau, were seriously contaminated according to our previous studies (Wang et al. 2018, Gao et al. 2019b. Considering the susceptible natural environment of Loess Plateau, the hazardous impacts of petroleum hydrocarbons on this region might be much more serious than other ecosystem. ...
... Consisting to previous studies, saturated hydrocarbons are the most susceptible to biodegradation, while the PAHs are more difficult to be degraded by microorganisms. PAHs with cyclic structure are usually toxic to microbes (Wang et al. 2018). Polar components are mostly macromolecular mass substances with complex and stable structure and anti-biodegradability, which results in basically no degradation by microorganisms (Zhou et al. 2011). ...
Article
Full-text available
Petroleum hydrocarbons have been worldwide concern contaminants because of their mutagenicity and carcinogenicity. The potential biodegradation of petroleum hydrocarbons at low temperatures is important for petroleum contamination remediation in cold region. In this study, a mixed cold-adapted bacteria flora JY, including seven petroleum-degrading strains (B1, H1, H2, H3, R1, R2, and S), was isolated from Alpine Meadow soil. Based on their 16S rRNA sequence analysis, B1, R1, and H3 were identified as Arthrobacter sp.; R2, S, H1, and H2 were identified as Rhodococcus sp., Pseudomonas sp., Stenotrophomonas sp., and Sphingobacterium sp., respectively. The mixed flora demonstrated 53.68% of total petroleum hydrocarbons (TPH) removal of the contaminated water (1 g oil L⁻¹) after 30 days of incubation under 10 °C. In the degradation process, alkanes were more preferred to be degraded by JY than polycyclic aromatic hydrocarbons (PAHs) and other polar component. During this period, the abundant bacteria in the flora were transformed from alkane degraders of Rhodococcus sp. and Sphingobacterium sp. to PAH degraders of Pseudomonas sp. and sheltered Arthrobacter sp. This study verified that a cold-adapted mixed culture JY isolated from alpines meadow soil was capable in degrading TPH under low temperature through flora cooperation.
... redissolve to 1 mL with hexane. The polar components were eluted by 100 mL dichloromethane and determined gravimetrically 21 . 100 µL aliquot of four surrogate standards (n-hexane-d14, n-undecane-d24, phenanthrene-d10, and benz[a]anthracene-d12) (each at a concentration of 2 µg/mL) were added to soil samples before extraction to estimate the extraction efficiency of n-alkanes and 16 PAHs, respectively. ...
... TEQs of ∑PAH16 in petro-related area soils were in the highest range of 620.93 μg/kg-1434. 21 46 . Therefore, contamination control should priority focus on the individual PAHs of BaP, DBA, BbF in these areas. ...
Article
Full-text available
The distribution and characteristics of petroleum in three different geographic oilfields in China: Shengli Oilfield (SL), Nanyang Oilfield (NY), and Yanchang Oilfield (YC) were investigated. The average concentration of the total petroleum hydrocarbons (TPHs) conformed to be in the following law: SL Oilfield > NY Oilfield > YC Oilfield. Fingerprint analysis on the petroleum contamination level and source was conducted by the geochemical indices of n-alkanes and PAHs, such as low to high molecular weight (LMW/HMW) hydrocarbons, n-alkanes/pristine or phytane (C17/ Pr, C18/Ph), and ratio of anthracene/ (anthracene + phenanthrene) [Ant/(Ant + Phe)]. Soils adjacent to working well oils indicated new petroleum input with higher ratio of low to high molecular weight (LMW/HMW) hydrocarbons. The oil contamination occurred in the grassland soils might result of rainfall runoff. Petroleum source, petroleum combustion source, and biomass combustion were dominant PAHs origination of soils collected from oil exploitation area, petrochemical-related sites, farmland and grassland, respectively. The suggestive petroleum control strategies were proposed in each oilfield soils. Ecological potential risk of PAHs was assessed according to the toxic equivalent quantity (TEQ) of seven carcinogenic PAHs. The results showed that high, medium, and low ecological risk presented in petro-related area, grassland soils, and farmland soils, respectively. High ecological risk was persistent in abandoned oil well areas over abandoned time of 15 years, and basically stable after 5 years. This study can provide a critical insight to ecological risk management and source control of the petroleum contamination.
... Oil spillage occurs mostly due to natural disasters and anthropogenic activities such as attacks by militant organisations or accidents of ships during their transportation from one Gulf country to another. Incidents of oil spillage are of major concern because they result in consequential contamination of the sea and coastline area (Singh et al. 2015;Wang et al. 2018). Hydrocarbons present in crude oil have many adverse environmental as well as health impacts (Sayed et al. 2021). ...
Article
Petrochemicals are important hydrocarbons, which are one of the major concerns when accidently escaped into the environment. On one hand, these cause soil and fresh water pollution on land due to their seepage and leakage from automobile and petrochemical industries. On the other hand, oil spills occur during the transport of crude oil or refined petroleum products in the oceans around the world. These hydrocarbon and petrochemical spills have not only posed a hazard to the environment and marine life, but also linked to numerous ailments like cancers and neural disorders. Therefore, it is very important to remove or degrade these pollutants before their hazardous effects deteriorate the environment. There are varieties of mechanical and chemical methods for removing hydrocarbons from polluted areas, but they are all ineffective and expensive. Bioremediation techniques provide an economical and eco-friendly mechanism for removing petrochemical and hydrocarbon residues from the affected sites. Bioremediation refers to the complete mineralization or transformation of complex organic pollutants into the simplest compounds by biological agents such as bacteria, fungi, etc. Many indigenous microbes present in nature are capable of detoxification of various hydrocarbons and their contaminants. This review presents an updated overview of recent advancements in various technologies used in the degradation and bioremediation of petroleum hydrocarbons, providing useful insights to manage such problems in an eco-friendly manner.
... At the same time, this petrol usage has negative impacts on ecological balance (Xue et al., 2015). Blowouts during oil field development, various accidents more likely resulting in oil pipelines leakage and storage tanks leakage, oil tankers and its leakage accidents, oil well drilling, petroleum refinery, and production equipment overhauls are all common causes of petroleum hydrocarbon spills and discharges during petroleum production, storage, transportation, refining, and processing, as we have seen (Chen et al., 2015;Wang et al., 2018). Spilled oil is also a problem that contaminates drinking water. ...
Article
Full-text available
In soil, polycyclic aromatic hydrocarbons (PAHs) have resulted in severe environmental deterioration, compromised soil characteristics, and negatively affect all life forms, including humans. Developing appropriate and effective clean-up technology is crucial in solving the contamination issues. The traditional methods to treat PHAs contaminated soil are less effective and not ecofriendly. Bioremediation, based on bioaugmentation and biostimulation approaches, is a promising strategy for remediating contaminated soil. The use of plant growth-promoting rhizobacteria (PGPR) as a bioaugmentation tool is an effective technique for treating hydrocarbon contaminated soil. Plant growth-promoting rhizobacteria (PGPR) are group of rhizospheric bacteria that colonize the roots of plants. Biochar is a carbon-rich residue, which acts as a source of nutrients, and is also a bio-stimulating candidate to enhance the activities of oil-degrading bacteria. The application of biochar as a nutrient source to bioremediate oil-contaminated soil is a promising approach for reducing PHA contamination. Biochar induces polyaromatic hydrocarbons (PAHs) immobilization and removes the contaminants by various methods such as ion exchange electrostatic attractions and volatilization. In comparison, PGPR produce multiple types of biosurfactants to enhance the adsorption of hydrocarbons and mineralize the hydrocarbons with the conversion to less toxic substances. During the last few decades, the use of PGPR and biochar in the bioremediation of hydrocarbons-contaminated soil has gained greater importance. Therefore, developing and applying a PGPR-biochar-based remediating system can help manage hazardous PAH contaminated soil. The goal of this review paper is to (i) provide an overview of the PGPR mechanism for degradation of hydrocarbons and (ii) discuss the contaminants absorbent by biochar and its characteristics (iii) critically discuss the combined effect of PGPR and biochar for degradation of hydrocarbons by decreasing their mobility and bioavailability. The present review focuses on techniques of bioaugmentation and biostimulation based on use of PGPR and biochar in remediating the oil-contaminated soil.
... Today, increasing population with enhanced demand for petroleum and petroleum-based products cause higher probabilities of oil spills and improper waste disposal leading to PH-associated environmental threats ( Joshi et al. 2019). The mechanism pertaining to the production, storage, refining, processing and transportation of petroleum and petroleum associated products results in the release of petroleum hydrocarbon like polycyclic aromatic hydrocarbons (PAHs), during the partial combustion of the fossil fuels, and have its direct effect on the environment and human health (Wang et al. 2018). The hydrocarbons possess the ability to bring about an alteration in the structure and functions of microbial communities of the ecosystem (Chikere et al. 2011), and thereby cause the change in biogeochemical networks reducing plant productivity and destabilization of the food chain . ...
Article
The release of petroleum and petroleum derivatives, such as polycyclic aromatic hydrocarbons (PAHs), in the environment owing to anthropogenic activities, has become a major global threat to human health and ecological equilibrium. It causes a number of diseases and petroleum hydrocarbon (PH) compounds bind to soil components, making their removal very difficult. In order to find an eco-friendly, convenient, and non-expensive way, indigenous PH degrading microorganisms are employed. Biofilm, being a syntrophic association plays an important role in PAH degradation. The three-dimensional structure of the biofilm matrix is found to facilitate the efficient and rapid degradation of PAH. Various physicochemical parameters of biofilm are found to regulate the efficacy of PAH degradation. In order to amend certain drawbacks of biofilm mediated remedi-ation, these days microbial electrochemical systems are increasingly being used for redressal of PH contamination, where the solid anode functions as an endless electron acceptor and the microbial activity is stimulated by bio-current in situ to guarantee the PH removal from contaminated soil and water. Following uptake of emulsified PH, it may be denatured by biofilm-associated enzymes or by biosurfactant molecules (such as rhamnolipids). The biomolecules synthesized by the bacterial cells further help in the expression of the specific genes thereby helping in the enhancement of PH degradation. ARTICLE HISTORY
... Surface soil samples were collected from Yanchang (Shaanxi Yanchang Petroleum (Group) Co., Ltd.) oilfield, located in the Loess Plateau region of northern Shaanxi province, China. Detailed information about the sampling sites was described previously [30]. About 1.0 g of each soil sample was added to 100 mL of enrichment medium in a 250 mL flask and incubated in a rotary shaker at 30°C and 120 rpm until the exponential phase. ...
Article
Full-text available
Polycyclic aromatic hydrocarbons (PAHs) are key organic pollutants in the environment that pose threats to the ecosystem and human health. The degradation of high molecular weight (HMW) PAHs by enriched bacterial consortia has been previously studied, while the involved metabolisms and microbial communities are still unclear and warrant further investigations. In this study, five bacterial consortia capable of utilizing different PAHs (naphthalene, anthracene, and pyrene) as the sole carbon and energy sources were enriched from PAH-contaminated soil samples. Among the five consortia, consortium TC exhibited the highest pyrene degradation efficiency (91%) after 19 d of incubation. The degradation efficiency was further enhanced up to 99% by supplementing yeast extract. Besides, consortium TC showed tolerances to high concentrations of pyrene (up to 1000 mg/L) and different heavy metal stresses (including Zn²⁺, Cd²⁺, and Pb²⁺). The dominant genus in consortium TC, GS, and PL showing relatively higher degradation efficiency for anthracene and pyrene was Pseudomonas, whereas consortium PG and GD were predominated by genus Achromobacter and class Enterobacteriaceae, respectively. Consortium TC, as a highly efficient HMW PAH-degrading consortium, could be applied for synergistic biodegradation of HMW PAHs and in situ bioremediation of the sites contaminated with both PAHs and heavy metals.
... The δ 13 C values of oil carbon vary from -27 to -31‰ [8,27], on the average amounting in the Volgograd oblast to -29‰; the assumed average values for heavily oil-polluted soils are close. ...
Article
Petroleum contamination in terrestrial environments caused by industrial activities is a significant problem that has received considerable attention. Carbon and nitrogen isotopic compositions (δ¹³C and δ¹⁵N) effectively describe the behavior of plants and soils under petroleum contamination stress. To better understand plant and soil responses to petroleum-contaminated soil, δ¹³C and δ¹⁵N values of the plants (Agropyron cristatum, Leguminosae with C4 photosynthesis pathway, and Trifolium repens with C3 photosynthesis pathway) and the soil samples under 1-month exposure to different extents of petroleum contamination were measured. The results showed that petroleum contamination in the soil induced the soil δ¹⁵N values to increase and δ¹³C values to decrease; from 1.9 to 3.2 ‰ and from −23.6 to −26.8 ‰, respectively. However, the δ¹³C values of Agropyron cristatum decreased from −29.8 ‰ to −31.6 %, and the δ¹³C values of Trifolium repens remained relatively stable from −12.6 ‰ to −13.1 ‰, indicating that they have different coping strategies under petroleum-contaminated soil conditions. Moreover, the δ¹⁵N values of Trifolium repens decreased from 5.6 ‰ to 0.8 ‰ near the air δ¹⁵N values under petroleum-contaminated soil, which implies that their nitrogen fixation system works to reduce soil petroleum stress. The δ¹³C and δ¹⁵N values of Agropyron cristatum and Trifolium repens reflect changes in the metabolic system when they confront stressful environments. Therefore, stable isotopic compositions are useful proxies for monitoring petroleum-contaminated soil and evaluating the response of plants to petroleum contamination stress.
Article
The petroleum-contaminated soil (PCS) was used as a raw material to prepare carbonized soil (CS) and iron-modified CS (Fe–CS) by limited-oxygen pyrolysis and limited-oxygen pyrolysis with ferrate pretreatment, respectively. The effectiveness and mechanism of CS and Fe–CS as a persulfate (PS) activator to degrade aniline (AN) are investigated. Results demonstrate that PS can be effectively activated by CS and Fe–CS. The degradation efficiencies of AN are 86.45% and 98.58% within 8 h, and 59.67% and 66.30% of the total organic carbon are removed, respectively. After five consecutive reuses, CS and Fe–CS can still reach AN removal rates of 64.78% and 62.47%, respectively, and TOC removal rates of 50.28% and 58.01%, respectively. Fe loading can promote the pyrolysis of CS, increase oxygen-containing groups on the soil surface, and increase the graphitization of carbon in the soil. Radical- and hole-quenching experiments speculate that the predominant reactive species may be holes and ¹O2 and that holes are dominant. This research provides an innovative method for the high-value utilization of PCS, and a novel activator for PS to degrade organic pollutants.
Article
Bioremediation strategies apply environmental microbes to metabolize organic compounds and can be useful for the treatment of oil-contaminated soils. In this study, different approaches of bioremediation were compared on a scale-up treatment. The defined microbial consortium was formulated with degrading microorganisms previously selected (Pseudomonas mendoncina BPB 1.8, Bacillus cereus BPB 1.20, Bacillus cereus BPB 1.26, and Bacillus sphaericus BPB 1.35). Bioaugmentation/biostimulation, biostimulation, and natural attenuation strategies were evaluated after 60 days of treatment by gas chromatography. The contaminant level remained elevated after the treatments using natural attenuation and biostimulation. However, the bioaugmentation with biostimulation treatment showed a satisfactory ability to degrade petroleum hydrocarbons (85%). Interestingly, no correlation was observed with the presence of hydrocarbon-degrading microorganisms and CO2 production, and denaturing gradient gel electrophoresis exhibited no significant difference in the biodiversity of the treatments. Although, the results showed that the microbial consortium was imperative to the successful biodegradation of TPH-contaminated gas station soil.
Article
Full-text available
We compared data on the extent of bioremediation in soils polluted with oil. The data were obtained using conventional methods of hydrocarbon determination: extraction gas chromatography-mass spectrometry, extraction IR spectroscopy, and extraction gravimetry. Due to differences in the relative abundances of the stable carbon isotopes (C-13/C-12) in oil and in soil organic matter, these ratios could be used as natural isotopic labels of either substance. Extraction gravimetry in combination with characteristics of the carbon isotope composition of organic products in the soil before and after bioremediation was shown to be the most informative approach to an evaluation of soil bioremediation. At present, it is the only method enabling quantification of the total petroleum hydrocarbons in oil-polluted soil, as well as of the amounts of hydrocarbons remaining after bioremediation and those microbially transformed into organic products and biomass.
Article
Full-text available
Large oilfields are often coincidentally located in major river deltas and wetlands, and potentially damage the structure, function and ecosystem service values of wetlands during oil exploration. In the present study, the effects of crude oil contamination during oil exploration on soil physical and chemical properties were investigated in marshes of the Momoge National Nature Reserve in Jilin Province, China. The concentrations of total petroleum hydrocarbons in the marsh soil near the oil wells are significantly higher than those in the adjacent control marsh. Soil water contents in oil-contaminated marshes are negatively correlated with soil temperature and are significantly lower than those in the control area, especially in fall. Crude oil contamination significantly increases the soil pH up to 8.0, and reduces available phosphorus concentrations in the soil. The concentrations of total organic carbon are significantly different among sampling sites. Therefore, crude oil contamination could potentially alkalinize marsh soils, adversely affect soil fertility and physical properties, and cause deterioration of the marshes in the Momoge National Nature Reserve. Phyto-remediation by planting Calamagrostis angustifolia has the potential to simultaneously restore and remediate the petroleum hydrocarbon-contaminated wetlands. Crude oil contamination affects the soil physical and chemical properties, so developing an effective restoration program in the Momoge wetland is neccesary.
Article
Full-text available
Biomarkers are one of the most important hydrocarbon groups in petroleum. Biomarkers can be detected in low quantities (ppm and sub-ppm level) in the presence of a wide variety of other types of petroleum hydrocarbons by the use of the gas chromatography/mass spectrometry (GC/MS). Relative to other hydrocarbon groups in oil such as alkanes and most aromatic compounds, biomarkers are more degradation-resistant in the environment. Furthermore, biomarkers formed under different geological conditions and ages may exhibit different biomarker fingerprints. Therefore, chemical analysis of biomarkers generates information of great importance to environmental forensic investigations in terms of determining the source of spilled oil, differentiating and correlating oils, and monitoring the degradation process and weathering state of oils under a wide variety of conditions. This article briefly reviews biomarker chemistry, biomarker characterization and quantification, biomarker distributions, weathering effects on biomarker composition, bicyclic biomarker sesquiterpanes and diamondoids, diagnostic ratios and cross-plots of biomarkers, unique biomarkers, application of biomarker fingerprinting techniques for spill source identification, and application of multivariate statistical analysis for biomarker fingerprinting.
Article
Extracellular polymeric substances (EPS) are present both outside of the cells and in the interior of microbial aggregates, and account for a main component in microbial aggregates. EPS can influence the properties and functions of microbial aggregates in biological wastewater treatment systems, and specifically EPS are involved in biofilm formation and stability, sludge behaviors as well as sequencing batch reactors (SBRs) granulation whereas they are also responsible for membrane fouling in membrane bioreactors (MBRs). EPS exhibit dual roles in biological wastewater treatments, and hence the control of available EPS can be expected to lead to changes in microbial aggregate properties, thereby improving system performance. In this review, current updated knowledge with regard to EPS basics including their formation mechanisms, important properties, key component functions as well as sub-fraction differentiation is given. EPS roles in biological wastewater treatments are also briefly summarized. Special emphasis is laid on EPS controlling strategies which would have the great potential in promoting microbial aggregates performance and in alleviating membrane fouling, including limitation strategies (inhibition of quorum sensing (QS) systems, regulation of environmental conditions, enzymatic degradation of key components, energy uncoupling etc.) and elevation strategies (enhancement of QS systems, addition of exogenous agents etc.). Those strategies have been confirmed to be feasible and promising to enhance system performance, and they would be a research niche that deserves further study.
Article
Quorum sensing (QS) is a communication process between cells, in which bacteria secrete and sense the specific chemicals, and regulate gene expression in response to population density. Quorum quenching (QQ) blocks QS system, and inhibits gene expression mediating bacterial behaviors. Given the extensive research of acyl-homoserine lactone (AHL) signals, existences and effects of AHL-based QS and QQ in biological wastewater treatments are being subject to high concern. This review summarizes AHL structure, synthesis mode, degradation mechanisms, analytical methods, environmental factors, AHL-based QS and QQ mechanisms. The existences and roles of AHL-based QS and QQ in biomembrane processes, activated sludge processes and membrane bioreactors are summarized and discussed, and corresponding exogenous regulation strategy by selective enhancement of AHL-based QS or QQ coexisting in biological wastewater treatments is suggested. Such strategies including the addition of AHL signals, AHL-producing bacteria as well as quorum quenching enzyme or bacteria can effectively improve wastewater treatment performance without killing or limiting bacterial survival and growth. This review will present the theoretical and practical cognition for bacterial AHL-based QS and QQ, suggest the feasibility of exogenous regulation strategies in biological wastewater treatments, and provide useful information to scientists and engineers who work in this field.
Article
The concentrations of total petroleum hydrocarbons (TPH), n-alkanes (n-C8 through n-C40), and 16 polycyclic aromatic hydrocarbons (PAHs) in soils were determined to assess the level of organic contamination in soils from the Da-gang Petrochemical Industry Park with several big state-run enterprises, a recent rapid flourishing park in China. The results showed that the concentration of TPH in soil was high, up to 20 ng/g-12.8478 %; in particular, the content in most sites ranged from 1 to 2 %. Thus, it is clear that soil environment in the Da-gang Petrochemical Industry Park has been seriously polluted by TPH according to the Nemerow pollution index method. Furthermore, the average concentration of Σ(n-C>16 through n-C34) in 30 sampling sites was above the maximum limit set for F3 under all the conditions in the Canada-wide standards for petroleum hydrocarbons (PHC CWS) with 43.33-93.33 % soil samples exceeding F3 standards, and n-alkanes possessing higher concentrations were proved much abundant alkanes in this study. Besides, the predominance of even n-alkanes and lower carbon preference index (CPI) demonstrated that n-alkanes in surface soils were mainly caused by anthropogenic inputs, while the concentration of Σ16-PAHs was in the range of 1652.5-8217.3 ng/g and the BaA/(BaA + Chr) and Flu/(Flu + Pyr) ratios indicated that pyrogenic PAHs may be the dominant PAHs in most soils with the contribution of petrogenic hydrocarbons in some sites.
Article
Polycyclic aromatic hydrocarbons (PAHs) were extracted from 30 samples (24 soils and 6 stream sediments) collected in El-Tabbin area in the southern part of Greater Cairo, Egypt. Isopleth maps of PAHs clarified the regional variability and identified the most affected regions in the area suffering from high pollution. The total PAH concentrations were 53.4-5558.0ngg(-1) in the sample extracts. The highest values were found in a soil sample near a coke factory, with the highest concentration of single PAHs, which were 1064.8ngg(-1) of fluoranthene and 1286.4ngg(-1) of phenanthrene. The calculated ratios and indexes allowed to elucidate origin of the organic compounds and to identify emission sources. The overall molecular patterns are signatures of pyrolysis of fossil fuels and biomass. Petrogenic contamination was recognised in the sediment samples due to petroleum products deliveries from ships. Also perylene was prominent especially in samples of the River Nile sediments as a diagenetic product of fungi. Other detailed information on petrogenic sources was provided by analysis of alkanes and calculation of alkane ratios.
Article
The results from the measurements of aliphatic hydrocarbons suggest that hydrocarbons suggest that hydrocarbons in the Point Loma Wastewater Treatment Plant (PLWTP) effluents are mainly petroleum derived; those in the Tijuana River runoff have largely originated from terrestrial plants with visible petroleum contamination; and those in the sea surface microlayer, sediment traps, and sediments at various coastal locations off San Diego have mostly resulted from biogenic contributions with enhanced microbial products in the summer season. Rainfall in the winter season appeared to amplify the inputs from terrestrial higher plants to the coastal areas. The PLWTP discharged approximately 3.85 metric tons of n-alkanes (C{sub 10}-C{sub 35}) in 1994, well below the level (136 metric tons) estimated in 1979. The input of aliphatic hydrocarbons from the Tijuana River was about 0.101 metric tons in 1994. Diffusion, solubilization, evaporation, and microbial degradation seemed partially responsible for the difference in the concentrations and compositions of aliphatic hydrocarbons in different sample media, although the relative importance of each mechanism cannot be readily discerned from the available data. The results from analyses of aliphatic hydrocarbon compositional indices are generally consistent with those of polycyclic aromatic hydrocarbons.
Article
Oil is produced from the Suphan Buri, Phitsanulok and Fang Basins onshore central and northern Thailand. Most of the Cenozoic rift-basins onshore Thailand are 2–4 km deep, but the Phitsanulok Basin is the deepest with a basin-fill up to 8 km thick. In this basin, the Sirikit field produces ∼18,000–24,000 bbl/day of crude oil. In the Suphan Buri Basin, about 400 bbl/day of crude oil is produced from the U Thong and Sang Kajai fields. Approximately 800 bbl/day of crude oil is produced from the Fang field (Fang Basin), which in reality consists of a number of minor structures including Ban Thi, Pong Nok, San Sai, Nong Yao and Mae Soon. A total of eight oil samples were collected from these structures and from the Sirikit, U Thong and Sang Kajai fields. The oils were subjected to MPLC and HPLC separation and were analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS and GC-MS-MS). The U Thong oil was investigated in more detail by separating the oil into a number of fractions suited for the analysis of various specific compounds.