Effect of soil moisture dynamics on dense nonaqueous phase liquid (DNAPL) spill zone architecture in heterogeneous porous media

The amount, location, and form of NAPL in contaminated vadose zones are controlled by the spatial distribution of water saturation and soil permeability, the NAPL spill scenario, water infiltration events, and vapor transport. To evaluate the effects of these processes, we used the three-phase flow simulator STOMP, which includes a new permeability-liquid saturation-capillary pressure (k-S-P) constitutive model. This new constitutive model considers three NAPL forms: free, residual, and trapped. A 2-D vertical cross-section with five stratigraphic layers was assumed, and simulations were performed for seven cases. The conceptual model of the soil heterogeneity was based upon the stratigraphy at the Hanford carbon tetrachloride (CT) spill site. Some cases considered co-disposal of NAPL with large volumes of wastewater, as also occurred at the Hanford CT site. In these cases, the form and location of NAPL were most strongly influenced by high water discharge rates and NAPL evaporation to the atmosphere. In order to investigate the impact of heterogeneity, the hydraulic conductivity within the lower permeability layer was modeled as a realization of a random field having three different classes. For six extreme cases of 100 realizations, the CT mass that reached the water table varied by a factor of two, and was primarily controlled by the degree of lateral connectivity of the low conductivity class within the lowest permeability layer. The grid size at the top boundary had a dramatic impact on NAPL diffusive flux just after the spill event when the NAPL was present near the ground surface. NAPL evaporation with a fine grid spacing at the top boundary decreased CT mass that reached the water table by 74%, compared to the case with a coarse grid spacing, while barometric pumping had a marginal effect for the case of a continuous NAPL spill scenario considered in this work. For low water infiltration rate scenarios, the distribution of water content prior to a NAPL spill event decreased CT mass that reached the water table by 98% and had a significant impact on the formation of trapped NAPL. For all cases simulated, use of the new constitutive model that allows the formation of residual NAPL increased the amount of NAPL retained in the vadose zone. Density-driven advective gas flow from the ground surface controlled vapor migration in strongly anisotropic layers, causing NAPL mass flux to the lower layer to be reduced. These simulations indicate that consideration of the formation of residual and trapped NAPLs and dynamic boundary conditions (e.g., areas, rates, and periods of different NAPL and water discharge and fluctuations of atmospheric pressure) in the context of full three-phase flow are needed, especially for NAPL spill events at the ground surface. In addition, NAPL evaporation, density-driven gas advection, and NAPL vertical movement enhanced by water flow must be considered in order to predict NAPL distribution and migration in the vadose zone.     

Isolation and characterization of 1,2,4-trichlorobenzene mineralizing Bordetella sp. and its bioremediation potential in soil

A soil which has been polluted with chlorinated benzenes for more than 25 years was used for isolation of adapted microorganisms able to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB). A microbial community was enriched from this soil and acclimated in liquid culture under aerobic conditions using 1,2,4-TCB as a sole available carbon source. From this community, two strains were isolated and identified by comparative sequence analysis of their 16S-rRNA coding genes as members of the genus Bordetella with Bordetella sp. QJ2-5 as the highest homological strain and with Bordetella petrii as the closest related described species. The 16S-rDNA of the two isolated strains showed a similarity of 100%. These strains were able to mineralize 1,2,4-TCB within two weeks to approximately 50% in liquid culture experiments. One of these strains was reinoculated to an agricultural soil with low native 1,2,4-TCB degradation capacity to investigate its bioremediation potential. The reinoculated strain kept its biodegradation capability: (14)C-labeled 1,2,4-TCB applied to this inoculated soil was mineralized to about 40% within one month of incubation. This indicates a possible application of the isolated Bordetella sp. for bioremediation of 1,2,4-TCB contaminated sites.     

Life cycle assessment of fuel selection for power generation in Taiwan

Life cycle assessment (LCA) was applied to performance data from 1997-2002 to evaluate the environmental impacts of the energy input, airborne emission, waterborne emission, and solid waste inventories for Taiwan's electric power plants. Eco-indicator 95 was used to compare the differences among the generation processes and fuel purification. To better understand the environmental trends related to Taiwan's electric power industry, three fuel scenarios were selected for LCA system analysis. Results indicate that there are differences in characteristic environmental impact among the 13 power plants. Scenario simulation provided a basis for minimizing environmental impacts from fuel selection targets. Fuel selection priority should be a gas-fired combined cycle substituted for a coal-fired steam turbine to be more environmentally friendly, particularly in the areas of the greenhouse effect, acidification, winter smog, and solid waste. Furthermore, based purely on economic and environmental criteria, it is recommended that the gas-fired combined cycle be substituted for the oil-fired steam turbine.     

Fungicidal values of bio-oils and their lignin-rich fractions obtained from wood/bark fast pyrolysis

Pine wood, pine bark, oak wood and oak bark were pyrolyzed in an auger reactor. A total of 16 bio-oils or pyrolytic oils were generated at different temperatures and residence times. Two additional pine bio-oils were produced at the National Renewable Energy Laboratory in a fluidized-bed reactor at different temperatures. All these bio-oils were fractionated to obtain lignin-rich fractions which consist mainly of phenols and neutrals. The pyrolytic lignin-rich fractions were obtained by liquid-liquid extraction. Whole bio-oils and their lignin-rich fractions were studied as potential environmentally benign wood preservatives to replace metal-based CCA and copper systems that have raised environmental concerns. Each bio-oil and several lignin-rich fractions were tested for antifungal properties. Soil block tests were conducted using one brown-rot fungus (Gloeophyllum trabeum) and one white-rot fungus (Trametes versicolor). The lignin-rich fractions showed greater fungal inhibition than whole bio-oils for a impregnation solution 10% concentration level. Water repellence tests were also performed to study wood wafer swelling behavior before and after bio-oil and lignin-rich fraction treatments. In this case, bio-oil fractions did not exhibit higher water repellency than whole bio-oils. Comparison of raw bio-oils in soil block tests, with unleached wafers, at 10% and 25% bio-oil impregnation solution concentration levels showed excellent wood preservation properties at the 25% level. The good performance of raw bio-oils at higher loading levels suggests that fractionation to generate lignin-rich fractions is unnecessary. At this more effective 25% loading level in general, the raw bio-oils performed similarly. Prevention of leaching is critically important for both raw bio-oils and their fractions to provide decay resistance. Initial tests of a polymerization chemical to prevent leaching showed some success.     

Political will,political skill,and political behavior

The current study used Mintzberg's (1983) conceptualization of political will and political skill to evaluate the predictors and consequences of political behavior at work. As elements of political will, we hypothesized that need for achievement and intrinsic motivation would predict the use of political behavior at work. Furthermore, we argued that political skill would moderate the relationship between political behavior and emotional labor. Data gathered from employees (N = 193) representing a wide array of organizations substantiated the proposed relationships. Specifically, need for achievement and intrinsic motivation were positively associated with political behavior. In turn, those opting to employ political behavior at work experienced a higher degree of emotional labor, but this relationship was found to operate differently at low and high levels of political skill. Specifically, emotional labor was a consequence of political behavior for those low in political skill, but emotional labor reactions from political behavior were neutralized for individuals high in political skill. Implications of these results, strengths and limitations, and directions for future research are discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

When experts disagree: the need to rethink indicator selection for assessing sustainability of agriculture

Sustainability indicators are well recognized for their potential to assess and monitor sustainable development of agricultural systems. A large number of indicators are proposed in various sustainability assessment frameworks, which raises concerns regarding the validity of approaches, usefulness and trust in such frameworks. Selecting indicators requires transparent and well-defined procedures to ensure the relevance and validity of sustainability assessments. The objective of this study, therefore, was to determine whether experts agree on which criteria are most important in the selection of indicators and indicator sets for robust sustainability assessments. Two groups of experts (Temperate Agriculture Research Network and New Zealand Sustainability Dashboard) were asked to rank the relative importance of eleven criteria for selecting individual indicators and of nine criteria for balancing a collective set of indicators. Both ranking surveys reveal a startling lack of consensus amongst experts about how best to measure agricultural sustainability and call for a radical rethink about how complementary approaches to sustainability assessments are used alongside each other to ensure a plurality of views and maximum collaboration and trust amongst stakeholders. To improve the transparency, relevance and robustness of sustainable assessments, the context of the sustainability assessment, including prioritizations of selection criteria for indicator selection, must be accounted for. A collaborative design process will enhance the acceptance of diverse values and prioritizations embedded in sustainability assessments. The process by which indicators and sustainability frameworks are established may be a much more important determinant of their success than the final shape of the assessment tools. Such an emphasis on process would make assessments more transparent, transformative and enduring.     

模拟消落带水华暴发行为的数值沙堆模型

以长江最大支流汉江近年来水华污染的现场资料为例,通过氮磷浓度、水温、流速和光照等实测数据构建了消落带开放水域环境体系的数值沙堆模型,描述了藻类生长及水华暴发的动力学机制;利用数值沙堆系统崩塌行为反映出的频率-尺度幂律关系作为判断消落带水域是否暴发水华以及规模大小的依据,采用有限尺度标度分析从不同侧面验证了水华暴发系统的自组织临界性,并揭示出各种拟合参数与水华暴发规模之间的定量关系.研究表明,沙堆模型如果存在良好的幂律关系,相应的消落带水域将暴发水华,且幂律指数越大,水华污染程度越严重.     

Hazardous emissions and concentrations of toxic metalloids and trace elements in charcoals from six commonly used tropical timbers for carbonization

Carbonized wood is a biofuel from cellulose pyrolysis with frequent smoke and life-threatening carcinogenic emissions. Carbon monoxide (CO), particulate matter (PM_2.5), metalloids and trace elements from charcoals from six commonly used tropical timbers for carbonization in Donkorkrom (Ghana) were assessed. During combustion, Anogeissus leiocarpa charcoal emitted the least CO (4.28 ± 1.08 ppm) and PM_2.5 (3.83 ± 1.57 μg/m³), while particulate matter was greatest for Erythrophleum ivorense (28.05 ± 3.08 ppm) and Azadirachta indica (27.67 ± 4.17 μg/m³) charcoals. Erythrophleum ivorense charcoal produced much lead (16.90 ± 0.33 ppm), arsenic (1.97 ± 0.10 ppm) and mercury (0.58 ± 0.003 ppm) but the least chromium (0.11 ± 0.01 ppm) and zinc (2.85 ± 0.05 ppm). Nickel was greatest for A. indica charcoal (0.71 ± 0.01 ppm) and least for Vitellaria paradoxa (0.07 ± 0.004 ppm). Trace elements ranged from 342.01 ± 2.54 ppm (A. indica) to 978.47 ± 1.80 ppm (V. paradoxa) for potassium and 1.74 ± 0.02% (V. paradoxa) to 2.24 ± 0.10% (A. indica) for sulphur. Besides A. leiocarpa charcoal, which ranked safest during combustion, the high PM_2.5 and CO emissions make the other biofuels hazardous indoors. Kitchens need air filters to absorb these emissions together with the use of improved cook stoves. These carcinogenic metalloids would necessitate that their ashes be properly discarded without human contact. Yet, the charcoals would be much suitable as soil amendment bio-char for plant growth quality improvement.