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71.
Solid-state 15N NMR was applied to the aqueous extracts of a 13C-enriched plant slurry (Lolium perenne), anaerobically incubated with 15N3-trinitrotoluene (TNT). Almost all 15N3-TNT transformation products became covalently bound to the plant-derived organic material extractable with water. DCPMAS
15N 13C NMR revealed a three-step reaction scheme. After reduction of TNT, the aryl amines are acetylated. Subsequent alkylation
of the resulting amides strengthens the incorporation of TNT-transformation products into humic material. Comparable results
have been recently obtained under aerobic conditions, which indicates that this pathway is a common process during biological
TNT transformation. 相似文献
72.
Surfactant complexation may have significant effects on the environmental behavior of nano-particles.In order to understand the ecological exposure of nano-materials,it is important to determine the stability and mobility of surfactant-complexed nano-materials in aqueous systems.In this study,the aggregation and transport of C_(60) complexed by the surfactant sodium dodecyl benzene sulfonate(SDBS)were investigated.It was found that SDBS-complexed C-_(60) had aζ-potential of-49.5 m V under near-neutral p H conditions and remained stable during an aging period of 15 days.It had a critical coagulation concentration of 550 mmol/L for Na Cl,which was higher than common natural colloids and many kinds of raw nano-materials,and was comparable to those of many kinds of surface-modified nano-materials.SDBS enhanced the stability of C_(60) colloid;however,at the same time,it also enhanced the colloidal particle aggregation rate.Much higher mobility was found for SDBS-complexed C_(60) than C_(60) colloid.Increase in ionic strength,Ca~(2+) concentration or Al~(3+) concentration decreased the mobility.In general,SDBS-complexed C_(60) had high stability and mobility. 相似文献
73.
Ramsis B. Salama Richard Silberstein Daniel Pollock 《Water, Air, & Soil Pollution: Focus》2005,5(1-2):3-26
The flow pathways of water in the soils of the Gnangara Mound are highly irregular and depend upon the moisture content, the
repellency and preferential wettability potential of the soils. The occurrence of preferential flow is more evident in dry
soils. As the soil wets during the rainy season, the water repellence and differential wettability decreases, the fingering
and the preferential flow paths disappear. Most of the agricultural sites in the Spearwood Sands which showed more irregular
flow than the Bassendean Sands are under continuous irrigation during cultivation season. As the repellency problems are chemically
treated, it is therefore expected that the flow will be more uniform all the year round. Landuse is mainly responsible for
variation in recharge rates; however, the hydraulic properties control aquifer response and water level pattern to a greater
degree. Water levels in the mid 1970s were in a semi steady state. Since that time, a combination of increasing water use
by pine plantations, heavy pumping from private boreholes in market gardens and private homes and intensive pumping from the
Gnangara Mound for the metropolitan water supply have caused water levels to continually decline in the Superficial aquifer.
Nitrate and phosphate concentrations in the regional Superficial aquifer are generally very low. None of the tested pesticides
(atrazine, diazinon, dimethoate, endosulfan, fenamiphos, iprodione, malathion and chlorpyrifos) were detected in the groundwater
samples collected from the monitoring bores. 相似文献
74.
75.
Carmen Difiglio Dolf Gielen 《Mitigation and Adaptation Strategies for Global Change》2007,12(3):387-405
If hydrogen (H2) is to significantly reduce greenhouse gas emissions and oil use, it needs to displace conventional transport fuels and be
produced in ways that do not generate significant greenhouse gas emissions. This paper analyses alternative ways H2 can be produced, transported and used to achieve these goals. Several H2 scenarios are developed and compared to each other. In addition, other technology options to achieve these goals are analyzed.
A full fuel cycle analysis is used to compare the energy use and carbon (C) emissions of different fuel and vehicle strategies.
Fuel and vehicle costs are presented as well as cost-effectiveness estimates. Lowest hydrogen fuel costs are achieved using
fossil fuels with carbon capture and storage. The fuel supply cost for a H2 fuel cell car would be close to those for an advanced gasoline car, once a large-scale supply system has been established.
Biomass, wind, nuclear and solar sources are estimated to be considerably more expensive. However fuel cells cost much more
than combustion engines. When vehicle costs are considered, climate policy incentives are probably insufficient to achieve
a switch to H2. The carbon dioxide (CO2) mitigation cost would amount to several hundred US$ per ton of CO2. Energy security goals and the eventual need to stabilize greenhouse gas concentrations could be sufficient. Nonetheless,
substantial development of related technologies, such as C capture and storage will be needed. Significant H2 use will also require substantial market intervention during a transition period when there are too few vehicles to motivate
widely available H2 refueling.
相似文献
Dolf GielenEmail: |
76.
77.
Environmental risk assessment of metals contaminated soils at silvermines abandoned mine site,Co Tipperary,Ireland 总被引:2,自引:0,他引:2
A centuries long history of mining and mineral processing has resulted in elevated Cd, Pb and Zn soil concentrations in the vicinity of the Silvermines abandoned mine site (AMS), Co. Tipperary, Ireland. A process for preliminary evaluation of environmental risk was developed and implemented. Potential pathways of metal compound transport and deposition were mapped and used to optimise the subsequent site investigation. Elevated soil metals are shown to be predominantly in areas where metal deposition in soil is associated with water related pathways (surface runoff, seasonal groundwater seepage and floodplains). Extensive areas of soil in the surrounding district are classified as contaminated on the basis of Cd, Pb and Zn concentrations, both total and potential bioavailable (EDTA-extractable). The most affected areas, with metal concentrations in soil comparable with that within the AMS, were floodplains located 2–3 km downstream from the site. Assessment of the sequential effects on grass and grazing animals indicates that Pb poses the greatest risk due to its high toxicity and high concentrations in soil (more than 10 000 mg kg–1). Within floodplain areas grazing cattle may intake a lethal dose of Pb. On the basis of the investigation an approach to risk assessment was developed which allowed quantified assessment of the risks related to individual metals, areas of contamination and contamination targets. 相似文献
78.
Fracturing, either pneumatic or hydraulic, is a method to improve the performance of soil vapor extraction (SVE) in relatively low permeability soils (< 10(-5) cm/s). A two-dimensional model is presented to simulate trichloroethylene (TCE) soil vapor extraction modified by fracturing. Flow and transport is modeled using mobile macropore and micropore networks, which also have been identified in the literature as dual porosity, dual permeability, or heterogeneous flow models. In this model, fluids can flow in both the macropore and micropore networks. This represents a more general model compared to immobile micropore, mobile macropore models presented thus far in the literature for vapor flow and transport in two dimensions. The model considers pressure- and concentration-driven exchange between the macropore and micropore networks, concentration-driven exchange between the gas and sorbed phases within each network, and equilibrium exchange between the gas and water and a sorbed phase within each network. The parameters employed in an example simulation are based on field measurements made at a fractured site. Considered in the simulations were the influence of the volume percentage of fractures, the length of fractures, the relative location of the water table, and the influence of pulsed pumping. For these simulations, internetwork concentration-driven exchange most significantly affected mass removal. The volume percentage of fractures more significantly influence flow and mass removal than the length of fractures. The depth of the water table below the contamination plume only significantly influenced flow and mass removal when the water table was within 60 cm of the bottom of the contaminated soil in the vadose zone for the parameters considered in this study. Pulsed pumping was not found to increase the amount of mass removed in this study. 相似文献
79.
Johnson DL 《Environmental geochemistry and health》2008,30(6):589-596
This work introduces a spatially resolved quantitative model, based on conservation of mass and first order transfer kinetics,
for following the transport and redistribution of outdoor soil to, and within, the indoor environment by track-in on footwear.
Implementations of the DIRT model examined the influence of room size, rug area and location, shoe size, and mass transfer
coefficients for smooth and carpeted floor surfaces using the ratio of mass loading on carpeted to smooth floor surfaces as
a performance metric. Results showed that in the limit for large numbers of random steps the dual aspects of deposition to
and track-off from the carpets govern this ratio. Using recently obtained experimental measurements, historic transport and
distribution parameters, cleaning efficiencies for the different floor surfaces, and indoor dust deposition rates to provide
model boundary conditions, DIRT predicts realistic floor surface loadings. The spatio-temporal variability in model predictions
agrees with field observations and suggests that floor surface dust loadings are constantly in flux; steady state distributions
are hardly, if ever, achieved.
A contribution from ESF Center for the Urban Environment. 相似文献
80.
Cormenzana JL García-Gutiérrez M Missana T Junghanns A 《Journal of contaminant hydrology》2003,61(1-4):63-72
Effective diffusion coefficients (D(e)) are usually measured by means of "through-diffusion" experiments in which steady state is reached, and the "time-lag" methods are used to estimate the apparent diffusion coefficient (D(a)). For sorbing radionuclides (as caesium), the time needed to reach steady-state conditions is very large, and the precision in D(a) determinations is not satisfactory. In this paper, a method that allows determining simultaneously effective and apparent diffusion coefficients in compacted bentonite without reaching steady-state conditions is described. Basically, this method consists of an "in-diffusion" experiment in which the concentration profile in the bentonite sample is used to estimate D(a), and the temporal evolution of the solute concentration in the reservoir is used to estimate D(e). This method has several advantages over the typical "through-diffusion" experiments, in particular: (a) experiment duration is significantly shorter, (b) D(a) values are measured with greater precision and (c) it is not necessary to maintain a constant solute concentration in the reservoir. This new method has been used to estimate the effective and apparent diffusion coefficients for caesium in FEBEX bentonite and in order to validate it, the results have been compared with results previously obtained with standard methods. Experimental results have been satisfactorily modelled using a simple model of diffusion in porewater and the measured value of D(e)(Cs) is very similar to D(e)(HTO) in the same bentonite. There is no evidence of "surface diffusion" in FEBEX bentonite for caesium. 相似文献