Comprehensive Environmental Investigation at Former Industrial/Petroleum Underground Storage Tank Sites in Long Beach,CA: A Forensic Perspective

Two industrial sites were investigated based on years of available hydrogeologic information and monitoring data for soil and groundwater. Collected data were forensically evaluated using age-dating and fingerprinting methods. The previous business uses of the project sites were as a gas station, laundry/dry-cleaning service, and car wash with petroleum underground storage tanks (USTs). As a result, these sites were exposed to a number of toxic contaminants at relatively high concentrations. Source control was necessary for successful remediation and the ultimate removal of the remaining compounds from these industrial sites. Although contaminated soil around the source was excavated during the remedial action and the high concentrations of contaminants were reduced, typical groundwater contaminants such as petroleum hydrocarbons as gasoline (TPH-G), benzene, toluene, ethylbenzene, xylenes (BTEX), and oxygenates including methyl tert-butyl ether (MTBE), diisopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and tert-butyl alcohol (TBA) were persistently found at the studied sites around the source points. The plume and concentration of contaminants had changed their shapes and strength for all monitoring periods. Thus, additional source control seems to be a requirement for the complete removal of source contamination, which must be ascertained with groundwater and soil monitoring on a regular time base. For the study sites, monitored natural attenuation was relatively feasible for the long-term plan; however, it did not offer a perfect remediation solution for an ultimate goal because of residual toxic compounds that might have affected the surrounding residential areas at higher concentrations than their health limits. Therefore, as a remediation strategy, the combination of clean-up technology and natural attenuation with monitoring activities are more highly recommended than either clean-up or natural attenuation used separately.     

TiO2-Cu2O/蒙脱土复合光催化剂的制备与性能

以钠基蒙脱土（MMT）为载体,先采用溶胶-凝胶法将纳米TiO₂引入到MMT层间,再采用化学沉积法将纳米Cu₂O负载在TiO₂/MMT上,制备出TiO₂-Cu₂O/MMT纳米复合光催化剂。采用XRD、SEM、紫外-可见漫反射技术对催化剂进行了表征。以甲基橙为目标污染物,考察了催化剂的光催化性能。表征结果显示：TiO₂与Cu₂O均匀分布在MMT的表面与片层孔隙中;TiO₂-Cu₂O/MMT结合了TiO₂和Cu₂O的特性,拓宽了催化剂的光吸收范围。实验结果表明,在光源为可见光、初始甲基橙质量浓度为20 mg/L、光催化剂加入量为2 g/L的条件下,TiO₂-Cu₂O/MMT纳米复合光催化剂对甲基橙的光催化降解效果明显优于单一负载的Cu₂O/MMT和TiO₂/MMT,大幅提高了催化剂的光催化效率,反应300 min时TiO₂-Cu₂O/MMT对甲基橙溶液的脱色率达到93%。     

Fenton试剂高级氧化法降解甲基橙模拟废水研究

甲基橙是一种较难降解的有机苯环偶氮染料之一,研究其降解性能对其他染料废水体系的降解研究具有普遍参考价值。通过研究Fenton试剂降解甲基橙过程中的H202浓度、Fe2＋浓度、反应时间和反应体系pH值对甲基橙降解的影响,确定其最佳降解工艺条件为：当甲基橙浓度为20mg／L、pH值为3、Fe2＋浓度为1．5mmol／L、H2O2为32mmol/L时,降解率达到最大值（98．95％）。     

椰壳活性炭吸附消除VOCs

对一种椰壳活性炭对甲基丙烯酸甲酯的吸附消除行为进行了研究,重点考察了甲基丙烯酸甲酯的浓度、流速和吸附温度等条件以及水汽存在时对活性炭吸附行为的影响。结果表明,该颗粒活性炭对甲基丙烯酸甲酯有良好的吸附效果,甲基丙烯酸甲酯进口浓度和进气量的改变均会影响吸附饱和时间,导致其增加或减少。通过变温吸附实验确定降低环境温度对其吸附有促进作用。湿度为50%时吸附量相对干气饱和吸附量影响较小,说明该活性炭抗水汽能力较好。经多次重复再生实验,其饱和吸附量未见明显下降。     

Nitrous oxide and methane emission from a flooded rice field as influenced by separate and combined application of herbicides bensulfuron methyl and pretilachlor

Combination of divergent active principles to achieve broad-spectrum control is gaining popularity to manage the weed menace in intensive agriculture. However, such application could have non-target impacts on the soil processes affecting soil ecology and environmental interactions. A field experiment was conducted to investigate the impact of separate and combined applications of herbicides bensulfuron methyl and pretilachlor on the emission of N₂O and CH₄, and related soil and microbial parameters in a flooded alluvial field planted to rice cv Lalat. Single application of the herbicide bensulfuron methyl or pretilachlor resulted in a significant reduction of N₂O and CH₄ emissions while the combination of these two herbicides distinctly increased N₂O and CH₄ emissions. Cumulative N₂O emissions (kg N₂O-N) followed the order of bensulfuron methyl (0.35 kg ha⁻¹) < pretilachlor (0.36 kg ha⁻¹) < control (0.45 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% single dose (0.49 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% double dose (0.54 kg ha⁻¹). Cumulative CH₄ emissions (kg CH₄), on the other hand, followed the order of bensulfuron methyl (47.89 kg ha⁻¹) < pretilachlor (73.17 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% single dose (93.50 kg ha⁻¹) < control (106.54 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% double dose (124.67 kg ha⁻¹). The inhibitory effect of separate application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% on N₂O emission was linked to lower mineral N, lower denitrifying and nitrifying activity and low denitrifier and nitrifier populations. Inhibitory effect on CH₄ emission, on the contrary, was linked to prevention in the drop of redox potential, lower readily mineralizable carbon (RMC) and microbial biomass carbon (MBC) contents as well as lower methanogenic and higher methanotrophic bacterial population. Admittedly, stimulatory effect of combined application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% at double dose on N₂O and CH₄ emission was related to reversal of the identified indicators of inhibition. Results indicate that while individual application of herbicides bensulfuron methyl 0.6% or pretilachlor 6.0% can reduce N₂O and CH₄ emission from flooded soil planted to rice, their combined application at normal dose can keep the emission at a comparatively lower level with significantly higher grain yield as compared to the herbicides applied alone.     

Assessing inter-laboratory comparability and limits of determination for the analysis of cyclic volatile methyl siloxanes in whole Rainbow Trout (Oncorhynchus mykiss)

Cyclic volatile methyl siloxanes (cVMS) are high volume production chemicals used in a wide range of industrial and consumer products. Three cVMS compounds (D4, D5, and D6) have and are undergoing environmental risk evaluations in several countries and have been proposed for legal regulation in Canada. As interest in monitoring concentrations of these chemicals in the environment increase, there is a need to evaluate the analytical procedures for cVMS in biological matrices in order to assess the quality of data produced. The purpose of this study was to determine laboratory testing performance for measuring residues of D4, D5, and D6 in a standard set of fish homogenate samples and to estimate limits of determination for each substance. The samples sent to each laboratory consisted of homogenized whole body tissues of hatchery raised rainbow trout which were fed food fortified with D4, D5, and D6 (dosed) and trout that were fed standard food rations (control). The participants analyzed each sample using their analytical method of choice using their own standards and procedures for quantification and quality control. With a few exceptions, participating laboratories generated comparable results for D4, D5, and D6 in both the dosed and control samples having z-scores between 2 and −2. Method detection limits for the whole fish matrix were on average 2.4 ng g⁻¹ ww for D4, 2.3 ng g⁻¹ ww for D5, and 1.8 ng g⁻¹ ww for D6.     

Fuel efficiency improvement of a dual-fuel engine fuelled with Honge oil methyl ester (HOME)–bioethanol and producer gas

Renewable and alternative fuels have numerous advantages compared with fossil fuels as they are renewable and biodegradable and provide food and energy security and foreign exchange savings besides addressing environmental concerns and socio-economic issues (Yaliwal et al. 2013. International Journal of Sustainable Engineering, doi:10.1080/19397038.2013.801530. Zhu et al. 2011a, Applied Thermal Engineering 31 (14–15): 2271–2278; Zhu et al. 2011b, Fuel 90: 1743-1750; Banapurmath, Tewari, and Hosmath 2008, Renewable Energy 33: 2007-2018; Banapurmath 2009, “Performance, Combustion and Emission Characteristics of a Single Cylinder Direct Injection CI Engine Operated on Dual Fuel Mode Using Honge Oil and Producer Gas.” PhD thesis, 1–195; Banapurmath et al. 2011, Waste and Biomass Valorization 2: 1–11). In this context, the main objective of the present work is to study methods of biofuel production such as Honge oil methyl ester (HOME) using a conventional transesterification process and bioethanol from the Calliandra calothyrsus shrub using a new pretreatment method known as hydrothermal explosion. Further, experimental investigations were carried out on a single-cylinder, four-stroke, direct-injection stationary diesel engine operating in a dual-fuel mode using HOME, bioethanol and producer gas combinations to determine its performance, combustion and emission characteristics. The performance of the dual-fuel engine was analyzed at optimized engine conditions. HOME-Bioethanol (BE) blends such as HOME+ 5% bioethanol (BE5), HOME+ 10% bioethanol (BE10) and HOME+ 15% bioethanol (BE15) were prepared by adding bioethanol to HOME (on volume basis) in different proportions ranging from 5 to 15% with an increment of 5%. In this present work, the effect of different BE blends on the performance of producer gas fuelled dual fuel engine was studied. Experimental investigation on dual fuel engine using BE5-Producer gas operation resulted in up to 4–9% increased brake thermal efficiency with decreased hydrocarbon (HC), carbon monoxide (CO) and marginally increased nitric oxide (NOx) emission levels compared to HOME-Producer gas, BE10-producer gas and BE15-producer gas mode of operation. However, it was observed that, the overall performance of BE-producer gas operation was found to be lower compared to diesel-producer gas operation.     

Performance,combustion and emission characteristics of a single-cylinder,four-stroke,direct injection diesel engine operated on a dual-fuel mode using Honge oil methyl ester and producer gas derived from biomass feedstock of different origin

Renewable and alternative fuels have numerous advantages compared with fossil fuels, as they are renewable and biodegradable, and provide food and energy security and foreign exchange savings besides addressing environmental concerns and socio-economic issues. In this context, present work was carried out to investigate the feasibility of alternative and renewable fuels derived from biomass feedstock of different origin for engine applications. The present study was also extended to study the effect of producer gas composition derived from different biomass feedstock on the performance, combustion and emission characteristics of a single-cylinder, four-stroke, direct injection stationary diesel engine operated on a dual-fuel mode using Honge oil methyl ester (HOME) and producer gas induction. The performance of the engine was evaluated with a constant injection timing of 27° before top dead centre, an injection pressure of 205 bar for the diesel–producer gas combination and 230 bar for the HOME–producer gas combination and a compression ratio of 17.5. The results showed that the performance of the dual-fuel engine varies with the composition of the producer gas and depends on the type of biomass feedstock used in the gasifier. Experimental investigations on the dual-fuel engine showed that brake thermal efficiency values for the engine operated using HOME–producer gas derived from babul, neem and honge woods were found to be 17.2, 14.3 and 11.56% respectively, compared to 23.8% for diesel–producer gas operation at 80% load. However, the results showed better engine performance with lower exhaust emission levels for the operation of HOME–producer gas derived from the ordinary or babul wood compared with the operation of that derived from the neem and Honge woods. In view of this, present study reveals that use of alternative and renewable fuels for dual fuel engine can be considered as an immediate solution for the development of rural areas and emergency use in the event of severe diesel fuel shortage.     

RuO_2-IrO_2/Ti阳极电催化降解偶氮染料甲基橙模拟废水

以自制Ti基Ru O2-Ir O2镀层形稳电极为阳极,采用电催化氧化处理偶氮染料甲基橙模拟废水。以硫酸钠为支持电解质,在自然p H条件下分别考察了电解时间、电极间距、电流密度和电解质浓度等因素对甲基橙去除率的影响,并分析其原因。实验结果表明,在自然p H、电极间距为1.0 cm、电流密度为30.0 m A/cm2、电解质硫酸钠浓度为20.0 g/L、电解1.0h,甲基橙去除率高达90.0%以上。因此,电催化氧化法作为一种高效、简便的染料废水处理技术,具有一定的应用潜力。     

改性粉煤灰合成沸石对甲基橙的吸附动力学

以粉煤灰(FA)为原料,采用水热晶化一步法制备了Na P1型沸石(ZFA),对合成产物的结构进行了表征,并采用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)对其进行改性。通过静态吸附实验,研究了改性后Na P1型沸石(MZFA)对水溶液中甲基橙的吸附特性,从动力学角度探讨了吸附机理。结果表明,在所研究的浓度条件下,改性Na P1型沸石对甲基橙的吸附符合Langmuir等温吸附方程,在25℃时,静态饱和吸附量(Qm)为64.76 mg/g。动力学分析表明,改性Na P1型沸石对溶液中甲基橙的吸附符合准二级动力学模型。