BTEX pollution caused by motorcycles in the megacity of HoChiMinh

Monitoring of benzene, toluene and xylenes (BTEX) was conducted along with traffic counts at 17 roadside sites in urban areas of HoChiMinh. Toluene was the most abundant substance, followed by p,m-xylenes, benzene, o-xylene and ethylbenzene. The maximum observed hour-average benzene concentration was 254 μg/m3 . Motorcycles contributed to 91% of the traffic fleet. High correlations among BTEX species, between BTEX concentrations and the volume of on-road motorcycles, and between inter-species ratios in air and in gasoline indicate the motorcycle-exhaust origin of BTEX species. Daily concentrations of benzene, toluene, ethylbenzene, p,m-xylenes and o-xylene were 56, 121, 21, 64 and 23 μg/m 3 , respectively. p,m-xylenes possess the highest ozone formation potential among the BTEX family.     

Anoxic biodegradation of dimethyl phthalate （DMP） by activated sludge cultures under nitrate-reducing conditions

Worldwide extensive use of plasticized plastics has resulted in phthalates pollution in different environment. Nitrates from industry and agriculture are also widely disseminated in the soils, natural waters and wastewaters. Dimethyl phthalate (DMP) biodegradation by activated sludge cultures under nitrate-reducing conditions was investigated. Under one optimized condition, DMP was biodegraded from 102.20 mg/L to undetectable level in 56 h under anoxic conditions and its reaction fitted well with the first-order kinetics. Using the high-performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC-MS) analysis, mono-methyl phthalate (MMP) and phthalic acid (PA) were detected as the major intermediates of DMP biodegradation. When combined with the determination of chemical oxygen demand (CODCr) removal capacity and pH, DMP was found to be mineralized completely under anoxic conditions. The biodegradation pathway was proposed as DMP → MMP → PA → … → CO2 H2O.The molar ratio of DMP to nitrate consumed was found to be 9.0:1, which agrees well with the theoretical stoichiometric values of DMP biodegradation by nitrate-reducing bacteria. The results of the non-linear simulation showed that the optimum pH and temperature for the degradation were 7.56 and 31.4℃, respectively.     

Pollution characteristics and health risk assessment of benzene homologues in ambient air in the northeastern urban area of Beijing, China

Ambient benzene homologues were measured at a site in the northeastern urban area of Beijing, China, from August 24 to September 4, 2012 by SUMMA canister sampling followed by laboratory determination using cryogenic cold trap pre-concentration-GC-MS/FID, and their health risks were also assessed. Daily total benzene homologues ranged from 0.99 to 49.71 μg/m3with an average of 11.98 μg/m3. Benzene homologues showed higher concentrations in the morning and evening than that at noontime. Comparison with previous studies revealed a trend of decrease for ambient benzene homologues probably due to the efective emission control in Beijing in recent years. Vehicular exhaust was the main source while volatilization of paints and solvents also made substantial contributions. Health risk assessment showed that BTEX(benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) and styrene had no appreciable adverse non-cancer health risks for the exposed population, while benzene has potential cancer risk of 1.34E-05. Available data from cities in China all implied that benzene imposes relatively higher cancer risk on the exposed populations and therefore strict control measures should be taken to further lower ambient benzene levels in China.     

Co-adsorption of gaseous benzene, toluene, ethylbenzene, m-xylene (BTEX) and SO2 on recyclable Fe3O4 nanoparticles at 0-101% relative humidities

We herein used Fe3O4 nanoparticles(NPs) as an adsorption interface for the concurrent removal of gaseous benzene, toluene, ethylbenzene and m-xylene(BTEX) and sulfur dioxide(SO2), at different relative humidities(RH). X-ray diffraction, Brunauer–Emmett–Teller, and transmission electron microscopy were deployed for nanoparticle surface characterization.Mono-dispersed Fe3O4(Fe2O3·Fe O) NPs synthesized with oleic acid(OA) as surfactant, and uncoated poly-dispersed Fe3O4 NPs demonstrated comparable removal efficiencies.Adsorption experiments of BTEX on NPs were measured using gas chromatography equipped with flame ionization detection, which indicated high removal efficiencies(up to(95 ± 2)%) under dry conditions. The humidity effect and competitive adsorption were investigated using toluene as a model compound. It was observed that the removal efficiencies decreased as a function of the increase in RH, yet, under our experimental conditions, we observed(40 ± 4)% toluene removal at supersaturation for Fe3O4 NPs, and toluene removal of(83 ± 4)% to(59 ± 6)%, for OA-Fe3O4 NPs. In the presence of SO2, the toluene uptake was reduced under dry conditions to(89 ± 2)% and(75 ± 1)% for the uncoated and coated NPs, respectively, depicting competitive adsorption. At RH 100%,competitive adsorption reduced the removal efficiency to(27 ± 1)% for uncoated NPs whereas OA-Fe3O4 NPs exhibited moderate efficiency loss of(55 ± 2)% at supersaturation.Results point to heterogeneous water coverage on the NP surface. The magnetic property of magnetite facilitated the recovery of both types of NPs, without the loss in efficiency when recycled and reused.     

Benzene, toluene and xylenes levels in new and used vehicles of the same model

The aim of this work was to determine the level of benzene, toluene, o-xylene and m, p-xylene （BTX） in air samples collected from the cabins of new and used vehicles of the same model. Ten new vehicles were examined in order to check interior emission from materials used to equip the passenger compartment. In order to compare and define the impact of exhaust gases, air samples were also collected from two used cars, at different mileages （up to 20,000 kin）. All vehicles tested were of the same type. Samples were collected onto Carbograph 1TD sorbent, thermally desorbed and examined with the use of gas chromatography with flame ionisation and mass spectrometry detectors. All results obtained were referred to Polish and German requirements for indoor air quality （both in public buildings and in workspace environments）. Average benzene, toluene, o-xylene and m, p-xylene concentrations in new cars were determined at the level of 11.8 μg/m^3, 82.7 μg/m^3, 21.2 μg/m^3 and 89.5 μg/m^3, respectively. In the used cars, BTX concentration increased with increasing vehicle mileage. The most significant increase of BTX concentration was observed above 11,000 km mileage.     

Groundwater contamination and natural attenuation capacity at a petroleum spilled facility in Korea

As a remedial option, the natural attenuation capacity of a petroleum contaminated groundwater at a military facility was examined. Hydrogeological conditions, such as high water level, permeable uppermost layer and frequent heavy rainfall, were favorable to natural attenuation at this site. The changes in the concentrations of electron acceptors and donors, as well as the relevant hydrochemical conditions, indicated the occurrence of aerobic respiration, denitrification, iron reduction, manganese reduction and sulfate reduction. The calculated BTEX expressed biodegradation capacity ranged between 20.52 and 33.67 mg/L, which appeared effective for the reduction of the contaminants levels. The contribution of each electron accepting process to the total biodegradation was in the order: denitrification > iron reduction > sulfate reduction > aerobic respiration > manganese reduction. The BTEX and benzene point attenuation rates were 0.0058-0.0064 and 0.0005-0.0032 day^-1, respectively, and the remediation time was 0.7-1.2 and 2.5-30 years, respectively. The BTEX and benzene bulk attenuation rates were 8.69 × 10^-4 and 1.05 × 10^-3 day^-1, respectively, and the remediation times for BTEX and benzene were 7.2 and 17.5 years, respectively. However, most of the natural attenuation occurring in this site can be attributed to dilution and dispersion. Consequently, the biodegradation and natural attenuation capacities were good enough to lower the contaminants levels, but their rates appeared to be insufficient to reach the remediation goal within a reasonable time frame. Therefore, some active remedial measures would be required.     

Biodegradation of alkylates under less agitated aquifer conditions

The biodegradability of three alkylates (2,3-dimethylpentane, 2,4-dimethylpentane and 2,2,4-trimethylpentane) under less agitated aquifer conditions was investigated in this study. All three alkylates biodegraded completely under these conditions regardless of the presence or absence of ethanol or benzene, toluene, ethylbenzene, and xylenes (BTEX) in the feed. In the presence of ethanol, alkylates degradation was not inhibited by ethanol. However, alkylates degraded more slowly in the presence of BTEX suggesting competitive inhibition to microbial utilization of alkylates. In the sterile controls, alkylates concentrations remained unchanged throughout the experiments.     

Phosphorus utilization and microbial community in response to lead/iron addition to a waterlogged soil

Constructed wetlands have emerged as a viable option for helping to solve a wide range of water quality problems. However, heavy metals adsorbed by substrates would decrease the growth of plants, impair the functions of wetlands and eventually result in a failure of contaminant removal. Typha latifolia L., tolerant to heavy metals, has been widely used for phytoremediation of Pb/Zn mine tailings under waterlogged conditions. This study examined e ects of iron as ferrous sulfate (100 and 500 mg/kg) and lead as lead nitrate (0, 100, 500 and 1000 mg/kg) on phosphorus utilization and microbial community structure in a constructed wetland. Wetland plants (T. latifolia) were grown for 8 weeks in rhizobags filled with a paddy soil under waterlogged conditions. The results showed that both the amount of iron plaque on the roots and phosphorus adsorbed on the plaque decreased with the amount of lead addition. When the ratio of added iron to lead was 1:1, phosphorus utilized by plants was the maximum. Total amount of phospholipids fatty acids (PLFAs) was 23%–59% higher in the rhizosphere soil than in bulk soil. The relative abundance of Gram-negative bacteria, aerobic bacteria, and methane oxidizing bacteria was also higher in the rhizosphere soil than in bulk soil, but opposite was observed for other bacteria and fungi. Based on cluster analysis, microbial communities were mostly controlled by the addition of ferrous sulfate and lead nitrate in rhizosphere and bulk soil, respectively.     

Degradation of dichloromethane by an isolated strain Pandoraea pnomenusa and its performance in a biotrickling filter

A strain Pandoraea pnomenusa LX-1 that uses dichloromethane(DCM) as sole carbon and energy source has been isolated and identified in our laboratory. The optimum aerobic biodegradation of DCM in batch culture was evaluated by response surface methodology. Maximum biodegradation(5.35 mg/(L·hr)) was achieved under cultivation at 32.8°C, pH 7.3, and 0.66% NaCl. The growth and biodegradation processes were well fitted by Haldane's kinetic model, yielding maximum specific growth and degradation rates of 0.133 hr-1and 0.856 hr-1, respectively. The microorganism efficiently degraded a mixture of DCM and coexisting components(benzene, toluene and chlorobenzene). The carbon recovery(52.80%–94.59%) indicated that the targets were predominantly mineralized and incorporated into cell materials. Electron acceptors increased the DCM biodegradation rate in the following order: mixed oxygen iron sulfate nitrate. The highest dechlorination rate was 0.365 mg Cl-/(hr·mg biomass), obtained in the presence of mixed electron acceptors. Removal was achieved in a continuous biotrickling filter at 56%–85% efficiency, with a mineralization rate of 75.2%. Molecular biology techniques revealed the predominant strain as P. pnomenusa LX-1. These results clearly demonstrated the effectiveness of strain LX-1 in treating DCM-containing industrial effluents. As such, the strain is a strong candidate for remediation of DCM coexisting with other organic compounds.     

Fate and degradation of nonylphenolic compounds during wastewater treatment process

In order to explore the biodegradation behavior of nonylphenolic compounds during wastewater treatment processing, two full-scale wastewater treatment plants were investigated and batch biodegradation experiments were conducted. The biodegradation pathways under the various operational conditions were identified from batch experiments: shortening of ethoxy-chains dominated under the anaerobic condition, whereas oxidizing of the terminal alcoholic group prevailed over the other routes under the aerobic condition. Results showed that the anoxic condition could accelerate the biodegradation rates of nonylphenolic compounds, but had no influence on the biodegradation pathway. The biodegradation rates of nonylphenol (NP) and short-chain nonylphenol polyethoxylates (NPnEOs, n: number of ethoxy units) increased from the anaerobic condition, then the anoxic, finally to the aerobic condition, while those of long-chain NPnEOs and nonylphenoxy carboxylates (NPECs) seemed similar under the various conditions. Under every operational condition, long-chain NPnEOs showed the highest biodegradation activity, followed by NPECs and short-chain NPnEOs, whereas NP showed relatively recalcitrant characteristics especially under the anaerobic condition. In addition, introducing sulfate and nitrate to the anaerobic condition could enhance the biodegradation of NP and short-chain NPnEOs by supplying more positive redox potentials.     

6种挥发性有机物在甲苯驯化微生物中的好氧生物降解性能

利用振荡摇瓶法测定了6种典型挥发性有机物,甲苯、邻二甲苯、间二甲苯、对二甲苯、苯和氯苯在甲苯驯化微生物中的好氧生物降解性能.结果表明,在本研究的液相浓度范围内(甲苯＜174mg/L,邻二甲苯＜149mg/L,间二甲苯＜129mg/L,对二甲苯＜133mg/L,苯＜234mg/L,氯苯＜146mg/L),3种二甲苯、苯和氯苯的降解速率随其初始浓度的增大而增加,符合一级反应,这5种VOCs未对微生物产生明显的抑制或毒害作用;甲苯的液相浓度大于85mg/L时,其降解速率不随初始浓度的增大而改变,其降解规律符合Monod方程.     

苯系化合物在硝酸盐还原条件下的生物降解性能

运用驯化的反硝化混合菌群进行了苯系化合物(BTEX)的厌氧降解试验.结果表明,混合菌群能够在反硝化条件下有效降解苯、甲苯、乙苯、邻二甲苯、间二甲苯和对二甲苯.BTEX的降解规律符合底物抑制的Monod模型,当初始浓度小于50mg·L^-1时,6种受试基质的厌氧降解速率顺序为:甲苯>乙苯>间二甲苯>邻二甲苯>对二甲苯>苯.整个试验过程中NO₃^-的消耗与苯、甲苯、乙苯、邻二甲苯、间二甲苯及对二甲苯生物降解之间的摩尔比分别为:9.47,9.26,1     

石化污泥对苯系化合物好氧生物降解的研究

为了探讨苯系化合物的生物降解途径,选用从石油化工污水处理场曝气池活性污泥中富集的混合菌种,在好氧条件下,研究了苯,甲苯,乙基苯,邻－,间－和对二甲苯的可生物降解性,当化合物的浓度为５０－１４０ｍｇ／Ｌ时,６种被试验化合物均可被微生物降解,从该混合菌种中筛选出１７株可降解甲苯,乙基苯,三甲苯,障－和对二甲苯的单一菌种,其中     

Anaerobic BTEX degradation in soil bioaugmented with mixed consortia under nitrate reducing conditions

Different concentrations of BTEX, including benzene, toluene, ethylbenzene, and three xylene isomers, were added into soil samples to investigate the anaerobic degradation potential by the augmented BTEX-adapted consortia under niwate reducing conditiom. All the BTEX substrates could be anaerobically biodegraded to non-detectable levels within 70 d when the initial concentrations were below 100 mg/kg in soil. Toluene was degraded faster than any other BTEX compounds, and the high-to-low order ofdegradation rates were toluene>ethylbenzene>m. xylene>o-xylene>benzene>P. xylene. Nitrite was accumulated with nitrate reduction. but the accumulation of nitrite had no inhibitory effect on the degradation of BTEX throughout the whole incubation. Indigenous bacteria in tIle soil could enhance the BTEX biodegradation ability of the enriched mixed bacteria. When the six BTEX compounds were simultaneously present in soil, there was no apparent inhibitory effect on their degradation with lower initial concentrations. Alternatively, benzene, o-xylene, and P-xylene degradation were inhibited with higher initial concentrations of 300 mg/kg. Higher BTEX biodegradation rates were observed in soil samples with the addition of sodium acetate compared to the presence of a single BTEX substrate. and the hypothesis of primary-substrate stimulation or cometabolic enhancement of BTEX biodegradation seems likely.     

反硝化苯降解的微环境研究

以稻田土,田边土和活性污泥为接种物,进行微环境试验,评价苯在厌氧反硝化条件下的可生物降解性。结果表明:苯和甲苯均发生了生物降解,甲苯的存在促进苯的降解,生物降解的同时发生硝酸盐还原,苯与硝酸根的消耗量之比为1∶2￣1∶3(质量比)。适宜的微生物种群是降解的关键条件。     

反硝化条件下微生物降解地下水中的苯和甲苯

利用实验室含水层物质微环境实验,对地下水中常见有机污染物苯和甲苯在厌氧反硝化条件下的微生物降解进行了研究．通过10种方案实验结果的分析对比表明,在强化反硝化条件下,微生物利用NO₃^-作为电子受体降解苯和甲苯;降解苯和甲苯的反硝化细菌来自于含水层物质;微生物所需要的宏量营养由苯、甲苯和硝酸盐提供,而微生物所需要的其他痕量元素来自于含水层物质;环境的酸碱条件对微生物降解具有重要影响pH值过高（pH＞10）或过低（pH＜4）均抑制微生物降解过程的进行这些结论对研究地下水有机污染及其生物治理具有一定的理论和实际指导意义     

天津市西南部苯系物浓度季节及空间变化特征

采用预冷冻浓缩系统和气相色谱/质谱联用仪,对天津市西南部BTEX（苯系物）浓度（以ρ计）进行了网格布点观测. 结果表明:ρ(苯)、ρ(甲苯)、ρ(乙苯)、ρ(间/对二甲苯)和ρ(邻二甲苯)的年均值分别为8.54、20.49、6.41、13.44和3.68 μg/m3,其中ρ(苯)和ρ(甲苯)均低于欧洲标准限值. 各BTEX浓度季节变化明显,与当地大气稳定度、光化学反应以及即时气象条件等因素密切相关. 利用各BTEX浓度的相关性,分析了不同类型采样点BTEX的来源,并证明工业企业和居民住宅附近存在非同源性苯和甲苯排放源. B/T〔ρ(苯)与ρ(甲苯)之比〕年均值为0.49,接近我国机动车尾气排放特点,但B/T值呈现出的季节变化特点可能与天津市供暖期燃煤排放有一定的关联.      

2012年夏季天津城区BTEX污染特征与臭氧潜势分析

采用AMA GC5000BTX在线色谱仪监测天津城区2012年夏季大气中苯、甲苯、乙苯、邻二甲苯和间-对二甲苯(苯系物,BTEX)的浓度,并结合其最大增量活性因子(MIR)计算各组分的最大臭氧生成潜势量.结果表明,观测期间BTEX浓度均值为38.72μg/m3,其中甲苯和间-对二甲苯浓度最高,乙苯和苯次之,邻二甲苯最低, BTEX存在明显的日变化特征,受大气光化学反应和边界层扩散能力共同影响,午后浓度最低,夜间BTEX浓度维持在较高水平,各BTEX日变化趋势一致.苯与甲苯质量浓度的比值为0.77,表明机动车排放是BTEX的主要来源,但石油化工和涂料挥发等因素也对其存在影响.经计算,间-对二甲苯的最大臭氧生成潜势量最高,甲苯、乙苯和邻二甲苯相当,苯最低, 表明BTEX中间-对二甲苯的光化学反应活性最强.     

苯系化合物好氧降解菌的驯化和筛选

为了筛选降解苯系化合物的优势菌种,选用城市污水处理场和石化废水处理的活性污泥作为菌源,分别以甲苯,乙苯,邻二甲苯,间二甲苯,对二甲本,１,３,５－三甲苯作为底物,在好氧条件下,驯化,筛选和分离出了能以上述６种化合物作为生长的唯一碳源和能源的微生物２５株,并对其进行了初步的鉴定,这些菌株的好氧生物降解研究结果表明,它们对苯系化合物具有良好生物降解能力。     

真菌Trichoderma viride Pers.ex Fr降解三苯废气性能实验

利用固相静态试验考察前期实验驯化出的真菌Trichoderma viride Pers.ex Fr对苯、甲苯、二甲苯的好氧生物降解性能。结果表明,在本研究的气相浓度范围内(苯47.25~1677.47g/m3,甲苯64.70~1258.50g/m3、二甲苯20.59~1707.85g/m3),3种气体的降解速率随其初始浓度的增大而增加,降解规律苯、甲苯符合Monod方程,二甲苯符合一级反应。