BTEX在乙醇汽油和传统汽油污染地下水中的衰减行为对比

地下燃油储藏罐泄漏造成苯、甲苯、乙苯和二甲苯（BTEX）影响生态环境和公众健康的问题一直备受关注,随着乙醇汽油的推广使用,乙醇对BTEX修复策略的影响成为需要重视的新问题.为揭示乙醇汽油污染地下水中BTEX的衰减行为,本文通过室内两个独立砂槽投注实验和近3年的监测,对比了乙醇汽油和传统汽油中BTEX自然衰减和基于硫酸盐-硝酸盐补充的增强生物修复行为.结果表明,传统汽油BTEX自然衰减较快,乙醇汽油BTEX自然衰减较慢,一级衰减速率常数分别为0.0055~0.0329 d^-1和0.0045~0.0124 d^-1;苯衰减最快,其次为甲苯.补充硫酸盐和硝酸盐能促进生物修复,单独补充硫酸盐时其利用率为89.7%~92.9%,同时补充硝酸盐时硫酸盐利用被抑制,硝酸盐利用率为79.9%~87.2%.水位波动会促进BTEX溶解和迁移,增大质量通量.乙醇汽油不仅能消耗更多电子受体,使得BTEX衰减被抑制,而且可能会扩大水位波动引起的增溶效应.     

Control of petroleum-hydrocarbon contaminated groundwater by intrinsic and enhanced bioremediation

In the first phase of this study, the e ectiveness of intrinsic bioremediation on the containment of petroleum hydrocarbons was evaluated at a gasoline spill site. Evidences of the occurrence of intrinsic bioremediation within the BTEX (benzene, toluene, ethylbenzene, and xylenes) plume included (1) decreased BTEX concentrations; (2) depletion of dissolved oxygen (DO), nitrate, and sulfate; (3) production of dissolved ferrous iron, methane, and CO2; (4) deceased pH and redox potential; and (5) increased methanogens, total heterotrophs, and total anaerobes, especially within the highly contaminated areas. In the second phase of this study, enhanced aerobic bioremediation process was applied at site to enhance the BTEX decay rates. Air was injected into the subsurface near the mid-plume area to biostimulate the naturally occurring microorganisms for BTEX biodegradation. Field results showed that enhanced bioremediation process caused the change of BTEX removal mechanisms from anaerobic biodegradation inside the plume to aerobic biodegradation. This variation could be confirmed by the following field observations inside the plume due to the enhanced aerobic bioremediation process: (1) increased in DO, CO2, redox potential, nitrate, and sulfate, (2) decreased in dissolved ferrous iron, sulfide, and methane, (3) increased total heterotrophs and decreased total anaerobes. Field results also showed that the percentage of total BTEX removal increased from 92% to 99%, and the calculated total BTEX first-order natural attenuation rates increased from 0.0092% to 0.0188% per day, respectively, after the application of enhanced bioremediation system from the spill area to the downgradient area (located approximately 300 m from the source area).     

基于TMVOC的水位波动带土壤气相抽提模拟

为探究水位波动对土壤气相抽提（Soil Vapor Extraction，SVE）修复的影响，以西北某傍河石化场地为研究对象，利用TMVOC模拟苯系物的自然衰减过程及不同水位状态下SVE修复过程，从修复效果、相间转化、饱和度演变等方面比较不同条件下苯系物的衰减率.结果显示，该场地较佳的抽提井的压强为9.1×10⁴Pa，影响半径为8m；苯系物在自然衰减、水位稳定状态下SVE修复及水位波动状态下SVE修复12个月后的质量损失分别为17%、85%、96%；水位稳定和水位波动状态下SVE修复12个月后，非水相液体（Non-Aqueous Phase Liquids，NAPL）的饱和度最大可达到0.066和0.044；水位稳定状态下，苯系物在"气-液-NAPL"相去除率逐渐降低，水位波动状态下，在水位下降的阶段，更多的NAPL相苯系物转化为气相，并被抽提气流携带去除.     

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     

BTEX在地下环境中的自然衰减

通过室内模拟柱实验研究了BTEX在地下环境中的自然衰减过程,发现BTEX通过以细砂为介质的模拟地下环境时确实发生了自然衰减,挥发和生物降解作用是其自然衰减的重要机制.以苯为例,其在水中的质量浓度为11.40 mg/L左右时,挥发和生物降解作用占自然衰减的比例分别是16.36%和4.91%;而甲苯浓度为3.30 mg/L左右时,两者所占比例分别是11.04%和41.50%.可见BTEX中各组分衰减规律不同.BTEX浓度越大,其挥发得也越快,挥发对自然衰减的作用越大.微生物降解作用对甲苯更有效,占自然衰减的41.50%,间、对二甲苯次之占8.49%,而苯和乙苯很难被降解.     

沈阳地区地表水、浅层地下水及沿岸土壤中苯

对沈阳地区主要地表水(浑河、细河、蒲河、沈抚灌渠)及其沿岸地下水和土壤中苯系物(BTEX)的污染特点和分布特征进行了研究.结果表明:细河和沈抚灌渠地表水中BTEX检出率较高(33%～67%),苯和甲苯是该区域的主要污染物,ρ(苯)和ρ(甲苯)分别为<0.30～24.90和<0.30～354.00 μg/L;地表水检出的BTEX均未超过《生活饮用水卫生标准》(GB5749—2006)的限值(1 510 μg/L). 细河两岸的浅层地下水在一定程度上受到BTEX的污染,苯和甲苯的检出率分别为25%～33%和13%～25%,二甲苯和乙苯检出率较低(0～20%). 彰驿镇19个监测井中有2个浅层地下水监测井中的ρ(苯)超过GB5749—2006限值(10 μg/L),夏季ρ(苯)最大值为236.00 μg/L. 沿岸附近土壤中5种BTEX全部被检出,检出率均高于相应的河水. 研究区包气带土壤层虽具有良好的防污性能,但也具有储存和阻碍BTEX挥发和降解的负面效应,对当地的生态系统和人类健康构成了潜在的威胁.      

地下水苯系物污染原位曝气修复模拟研究

通过TMVOC软件模拟了苯系物在拟定渗流区“自然”环境条件下的污染物运移行为和原位曝气修复过程中的污染物衰减过程,确定了最佳曝气流量和所需要的曝气井数量及分布,并对修复效果进行了模拟.模拟显示,泄露过程中,在重力作用下,不饱和区的苯系物以竖直迁移为主,同时在毛细作用下横向迁移;在饱和区中以顺水流方向水平迁移为主,同时会溶解进入地下水,污染羽可到达含水层底部.从含水层底部的7个曝气孔同时以12m3/h的速率将空气注入时,只需180d即可完全修复苯系物污染区域.该条件下单井有效修复半径约5m,有效修复范围优于从含水层中部和中下部进行曝气.     

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.     

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.     

加油站油类污染物自然衰减现场试验研究

利用自行设计制作的一套土壤气体取样监测装置,在北京地区某加油站开展了包气带内石油类污染物自然衰减的现场试验研究.在现场对包气带内的土壤气体样本进行采集,并对样本中的VOC含量及O2、CO2含量进行了检测分析.2个阶段的检测结果表明,经过381 d的自然衰减,污染点位的TVOC浓度减少了99.2%,BTEX的气相浓度占TVOC的比例由17.0%降至12.1%;O2和CO2含量在G3点位呈现出随着土壤深度的增加,O2含量逐渐减少、CO2含量逐渐增加的变化趋势.通过对试验结果的分析得出以下结论:①第一次检测结果表明G3点位附近存在一定的土壤污染,经过381 d的自然衰减,G3点位土壤中的BTEX含量已降至保护环境的标准以下,该污染现场的环境监控措施可以解除;②对造成该点污染的原因进行推断,可以判定污染为短期污染源导致,不存在持续的泄漏源;③自然衰减能够有效清除土壤中污染物,可以作为北京市同类污染场地有效的治理手段加以考虑;④检测污染土壤中O2和CO2含量的变化是判断有机污染物需氧降解的有效手段.     

低温条件下基于TMVOC的土壤气相抽提技术数值模拟

为研究低温条件下土壤气相抽提技术对包气带中苯系物的去除效果、解决修复技术有效性评估等难题,基于TMVOC模型模拟砂箱试验,从浓度梯度、相间转化、饱和度变化等方面分析土壤气相抽提技术对污染物空间分布规律的影响机理.结果表明,TMVOC模拟苯系物浓度的计算值与试验测量值的拟合效果较好;低温条件下,砂箱土体中苯、甲苯、乙苯、邻二甲苯的去除率分别为89.8%、71.3%、29.7%、14.4%.两次抽提过程中,苯在"气-液-NAPL（non-aqueous phase liquid）"三相中的质量均减少,减少比例近似为2:7:1,苯在液相中的质量减幅最大;在间歇期,苯由"NAPL相"以近似3:7的比例向"气、液"两相运移.在砂箱土体上部和中部NAPL相饱和度保持为0,"气-液"两相共存,间接表明苯系物在"气-液"两相间发生运移;在砂箱土体底部污染源附近"气-液-NAPL"相共存,间接表明苯系物在"气-液-NAPL"相间发生运移,抽提作用使得气相与液相饱和度升高、NAPL相饱和度降低.      

Anaerobic biodegradation of benzene series compounds by mixed cultures based on optional electronic acceptors

A series of batch experiments were performed using mixed bacterial consortia to investigate biodegradation performance of benzene, toluene, ethylbenzene and three xylene isomers （BTEX） under nitrate, sulfate and ferric iron reducing conditions. The results showed that toluene, ethylbenzene, m-xylene and o-xylene could be degraded independently by the mixed cultures coupled to nitrate, sulfate and ferric iron reduction. Under ferric iron reducing conditions the biodegradation of benzene and p-xylene could be occurred only in the presence of other alkylbenzenes. Alkylbenzenes can serve as the primary subs＇rates to stimulate the transformation of benzene and p-xylene under anaerobic conditions. Benzene and p-xylene are more toxic than toluene and ethylbenzene, under the three terminal electron acceptors conditions, the degradation rates decreased with toluene 〉 ethylbenzene 〉 m-xylene 〉 o-xylene〉 benzene 〉 p- xylene. Nitrate was a more favorable electron acceptor compared to sulfate and ferric iron. The ratio between sulfate consumed and the loss of benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene was 4.44, 4.51, 4.42, 4.32, 4.37 and 4.23, respectively; the ratio between nitrate consumed and the loss of these substrates was 7.53, 6.24, 6.49, 7.28, 7.81, 7.61, respectively; the ratio between the consumption of ferric iron and the loss of toluene, ethylbenzene, o-xylene, m-xylene was 17.99, 18.04, 18.07, 17.97, respectively.     

微氧条件下以甲烷为碳源的反硝化实验研究

为探清微氧条件下以甲烷为碳源的反硝化是甲烷好氧氧化偶联反硝化(AME-D),还是甲烷厌氧氧化偶联反硝化(ANME-D),本研究以污水处理厂厌氧污泥为接种物,在微氧条件下以甲烷为碳源进行硝酸盐和亚硝酸盐反硝化的富集培养,考察硝酸盐和亚硝酸盐的反硝化速率,并对富集培养物的微生物群落和甲烷单加氧酶功能基因进行分析.结果表明:微氧条件下硝氮/亚硝氮的还原主要以AME-D过程为主,稳定阶段硝氮和亚硝氮的平均去除速率分别为3.69 mg·L~(-1)·d~(-1)(以N计)和18.04 mg·L~(-1)·d~(-1)(以N计),富集培养物中的优势微生物为甲基球菌科(Methylococcaceae)中的甲基单胞菌属(Methylomonas),相对含量为21.86%.     

臭氧浓度升高对冬小麦田土壤呼吸、硝化和反硝化作用的影响

为研究臭氧浓度升高对农田土壤呼吸、硝化和反硝化作用的影响,采用开顶箱(OTC)法设置3个臭氧浓度处理,分别为对照CK、T1(100 nL.L-1臭氧)和T2(150 nL.L-1臭氧).以便携式土壤CO2通量观测仪测定不同臭氧浓度处理下的冬小麦田土壤呼吸速率,并采用气压过程分离(BaPS)法测定不同处理的土壤CO2产生速率、硝化速率和反硝化速率.结果表明,在本实验阶段内,CK、T1、T2处理的土壤呼吸速率之间无显著差异(p0.05),其平均土壤呼吸速率分别为(5.36±0.72)、(5.08±0.04)、(4.94±0.18)μmol.(m2.s)-1.CK和T2处理的硝化速率和反硝化速率也均无显著差异(p0.05).不同臭氧浓度处理下的土壤呼吸速率与土壤温度的指数回归关系均达显著水平(p0.05),CK、T1和T2处理的土壤呼吸的Q10值分别为1.72、1.58和1.51.Pearson相关分析结果表明,CK处理中土壤硝化速率与反硝化速率和土壤含水量之间均存在显著相关关系(p0.05),其相关系数分别为0.828和0.890;T2处理中硝化速率与土壤含水量之间存在显著相关关系(p0.05),其相关系数为0.772.本研究表明,臭氧浓度升高未显著改变冬小麦田土壤呼吸、硝化和反硝化速率,但臭氧浓度升高显著降低了土壤呼吸的温度敏感性.     

生物通风堆肥法修复原油污染土壤的实验研究

通过模拟实验考察了生物通风堆肥方法修复吉林油田原油污染土壤的效果,探讨了石油污染物去除的途径和作用机制.实验结果表明:向原油污染的土壤中添加生物有机肥接种、采用生物通风堆肥法进行修复,效果较好.当原油污染土壤的含油量为7.00×104mg·kg-1时.经过40d处理,原油的去除率达45%以上,最大生物降解速率常数达到了0.0333 d-1,半衰期仅为20.82d.生物降解是污染物去除的主要途径,挥发去除的油低于土壤初始含油量的0.1%.在油污土:生物有机肥(干重)以8:2、7:3和5:5三个不同比例混合的实验中,以7:3比例混合时污染物的去除最彻底,完全生物降解率占总去除率的比例约为17%.原油组分含量的变化证实了原油生物降解的发生.原油的生物降解去除率与生物降解产生的CO2存在线性关系.污染物生物降解的速率和程度与微生物的数量和活性关系密切.     

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.     

生物降解对土壤气中苯衰减系数及筛选值的影响

以砂质土壤为例,采用Bio-vapor软件计算了生物降解对苯的a_i-s(衰减系数)及筛选值的影响,并对关键影响参数〔c_s(污染源苯质量浓度)、LT(建筑底板与污染源距离)、L_a(好氧土层厚度)和k_w(生物降解系数)〕进行分析. 结果表明:当c_s≥5×105mg/m3时,生物降解对a_i-s基本无贡献;当c_s≤1×104 mg/m3时,生物降解可导致a_i-s降低1~2个数量级,但降幅随c_s和LT的变化不明显;当c_s介于二者之间时,生物降解对a_i-s的作用受LT变化的影响较明显,LT升高1个数量级时,生物降解可导致a_i-s降低2个数量级. 生物降解对a_i-s的作用受L_a影响比较明显,L_a由0.50m增至1.50m时,生物降解可导致a_i-s降低2个数量级. Bio-vapor软件预测的砂质土壤条件下L_a的最大值为0.63m,低于现场普遍测试结果(1.50m),表明该模型预测结果可能过于保守,实际项目中可通过测试土壤气中各组分的纵向分布确定L_a. 当c_s≤5×104 mg/m3时,k_w由0.033h-1增至2.000h-1,生物降解将导致a_i-s降低2个数量级. 因此,同一概念模型下考虑生物降解时土壤气中苯筛选值高于不考虑生物降解时1~2个数量级.      

Denitrification on Andosols in an intensive dairy farming region of central Japan

Evaluation of denitrification capacities is necessary to develop a sustainable manure management system in order to reduce NO₃⁻ leaching and N₂O emissions from agricultural soils. Denitrification rates were measured using the acetylene inhibition technique on intact soil cores from eight Andosols under three different cropping systems in an intensive livestock catchment of central Japan. The N application rates ranged from 200 to 800 kg N ha⁻¹ yr⁻¹. The denitrification rates were highly variable across fields, and were influenced significantly by land uses and manure forms. Compared with upland fields, paddy rice fields had a greater denitrification rate up to 1380 and 85 mg N m⁻² day⁻¹ in the top 30-cm soil layer during flooding and non-flooding periods, respectively. In upland fields, the maximum value for the top 30-cm soils was 44 mg N m⁻² day⁻¹ and most of the rates were less than 10 mg N m⁻² day⁻¹. The greater denitrification rates were often associated with slurry application rather than composted dry manure. Overall, denitrification from Andosols in this study displayed a lower capacity than that of non-Andosols.     

天津城区夏冬季典型污染过程中BTEX变化特征及其健康风险评估

利用GC955在线气相色谱仪分别于2019年7月和2020年1月在天津市区开展苯系物（BTEX,包括苯、甲苯、乙苯、间/对-二甲苯和邻-二甲苯）实时在线观测,对典型污染过程中BTEX的浓度水平、组成及演化机制进行了研究,并运用特征物种比值法对BTEX的来源进行了定性分析,最后运用US EPA的人体暴露分析评价方法对BTEX健康风险进行评估.结果表明,臭氧和霾污染过程中BTEX体积分数平均值分别为1.32×10^-9和4.83×10^-9,其中苯的体积分数占比最大,其次是甲苯、乙苯和二甲苯占比最小.2020年1月BTEX体积分数很大程度上受到西南方向短距离传输的影响,而在2019年7月BTEX浓度受到本地排放的影响.BTEX浓度水平在2019年7月受到温度和相对湿度的共同影响,而在2020年1月当温度较低时BTEX浓度对相对湿度的变化更敏感.天津市区BTEX在霾污染过程中受生物质燃烧/化石燃料燃烧/燃煤排放的影响较大,而在臭氧污染过程中除了受到燃烧排放源影响,交通源排放在很大程度上也有影响.臭氧污染和霾污染过程中BTEX的HI分别为0.072和0.29,均处于EPA认定的安全范围内.苯的致癌风险在清洁天和污染过程中均高于EPA规定的安全阈值,需引起高度重视.     

Utilizing surfactants to control the sorption, desorption, and biodegradation of phenanthrene in soil-water system

An integrative technology including the surfactant enhanced sorption and subsequentdesorption and biodegradation of phenanthrene in the soil-water system was introduced and tested. For slightly contaminated agricultural soils, cationic-nonionic mixed surfactant- enhanced sorption of organic contaminants onto soils could reduce their transfer to plants, therefore safe-guarding agricultural production. After planting, residual surfactants combined with added nonionic surfactant could also promote thedesorption and biodegradation of residual phenanthrene, thus providing a cost-effective pollution remediation technology.0ur results showed that the cationic-nonionic mixed surfactantsdodecylpyridinium bromide (DDPB) and Triton X-100 (TX100) significantly enhanced soil retention of phenanthrene. The maximum sorption coefficient Kd* of phenanthrene for contaminated soils treated by mixed surfactants was about24.5 times that of soils without surfactant (Kd ) and higher than the combined effects of DDPB and TX100 individually, which was about 16.7 and 1.5 times Kd , respectively.0n the other hand, TX100 could effectively remove phenanthrene from contaminated soils treated by mixed surfactants, improving the bioavailability of organic pollutants. Thedesorption rates of phenanthrene from these treated soils were greater than 85% with TX100 concentration above2000 mg/L and approached 100% with increasing TX100 concentration. The biodegradation rates of phenanthrene in the presence of surfactants reached over 95% in30days. The mixed surfactants promoted the biodegradation of phenanthrene to some extent in 10-22days, and had no obvious impact on phenanthrene biodegradation at the end of the experiment. Results obtained from this study provide some insight for the production of safe agricultural products and a remediation scheme for soils slightly contaminated with organic pollutants.