Estimating the ozone formation potential of volatile aromatic compounds in vehicle tunnels.

Two vehicle tunnels located in the Taipei area were selected to study the ozone formation potential of volatile aromatic compounds (VACs). Air samples in the two tunnels were collected using canisters. Analysis of VACs was conducted with a gas chromatograph equipped with a mass spectrometer. The total VOCs concentrations in Zefun tunnel ranged from 483.5 to 1032.2 (micrograms/m3) which increased with the increase in traffic volume. In the Lishin tunnel, the total VACs concentration ranged from 356.6 to 1961.3 (micrograms/m3) which was not well correlated with the traffic volume. The most predominant VACs in these vehicle tunnels were toluene and xylenes. Although the traffic volume and types of vehicles were not exactly the same, the characteristic ratios of the VACs concentrations were found to be similar. These results indicated that the existence of a specific characteristic ratio of VAC concentration was affected by the mobile sources. The maximum ozone formation potential resulted from the vehicles in the Lishin motorcycle tunnel which had higher values than the Zefun tunnel and much higher than the SPECIATE databases in the US via weighting the maximum incremental reactivity (MIR) scale.     

Effect of formaldehyde on Cu(II) removal from synthetic complexed solutions by ion exchange

The effect of formaldehyde (HCHO) on the ion exchange of Cu(II) from an equimolar EDTA (ethylenediaminetetraacetic acid, H(4)L) solution with a strong-base Amberlite IRA-400 resin was studied. Experiments were conducted as a function of the initial concentration of Cu(II) (0.5-10 mM), solution pH (1.0-6.0), HCHO concentration (0-6 vol%), and temperature (15-35 degrees C). It was shown that the amount of exchange of Cu(II), which exists in the form of complexed anions CuL(2-), increased with increasing solution pH and reached a plateau at an equilibrium pH (pH(e)) of 3.5. However, the amount of exchange decreased with increasing HCHO concentration up to 3 vol% but then slightly decreased with a further increase in HCHO concentration. Such effect of added HCHO was determined by the following two factors: the competitive exchange of HCOO(-) anions and the enhanced exchange of Cu(I) in the form of complexed anions CuL(3-). The exchange isotherm obtained at a fixed pH(e) could be well described by the Langmuir equation. The isosteric enthalpy change for the present ion exchange process was also evaluated and discussed.     

Dietary separation between two blennies and the Pacific gregory in northern Taiwan: evidence from stomach content and stable isotope analyses

Two blennies, Ecsenius lineatus Klausewitz and Ecsenius namiyei (Jordan and Evermann), and a cohabiting territorial damselfish, the Pacific gregory, Stegastes fasciolatus (Ogilby), were collected from shallow reefs in northern Taiwan between September and November 2004, and in October 2005 for stomach content and δ ¹³C and δ ¹⁵N analyses in an effort to study how extensively their food sources overlapped and to delineate the pattern of cohabiting interactions. These analyses showed differences in food use between the Ecsenius blennies and S. fasciolatus. However, there were inconsistencies. Epiphytic algae were their major food items of E. namiyei and E. lineatus. Macroalgae were rarely taken. Nevertheless, δ ¹³C and δ ¹⁵N signatures suggested that E. namiyei and E. lineatus might have assimilated mainly macroalgae-derived detritus instead of epiphytic algae. In contrast, macroalgae were the major food items of S. fasciolatus, followed by epiphytic algae. Differences in both δ ¹³C and ¹⁵N values indicated that for S. fasciolatus, algae (both macroalgae and epiphytic algae) might not be as important as the stomach contents showed. Instead, polychaetes were possibly its major food source. Differences between stomach contents and evidence from the separation of stable isotope signatures between blennies and the Pacific gregory indicate that some of the interspecific interactions derived from exploitative competition may have been alleviated. Moreover, their widespread territory overlap is possibly a sign of mutualism: S. fasciolatus allows territory sharing, while Ecsenius blennies, in return, clean up the algal mat by removing sand and detritus.     

Evaluating the implementation of cleaner production audit demonstration projects

Cleaner production audit demonstration projects were carried out in two Chinese case factories as part of a project co-sponsored by the Illinois Environmental Protection Agency and China's State Environmental Protection Administration. Audit results at both factories were characterized by implementation of predominantly low- or no-cost options, notable reductions in water pollution, and incomplete financial benefit analyses. Two reasons explain the financial benefit analyses' apparent weakness. First, factory audit teams were inexperienced in the techniques and procedures used to determine the economic benefits of cleaner production options. Second, motivations project personnel had for participating in the demonstration projects were not centered on attaining the monetary benefits of implementing cleaner production. Instead, other factors related to the international nature of the project, such as a high degree of state level oversight and prestige, were more influential in affecting the behavior of project personnel.     

Development of a biobarrier for the remediation of PCE-contaminated aquifer

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system, which includes a peat layer to enhance the anaerobic reductive dechlorination of PCE in situ. Peat was used to supply primary substrate (electron donor) continuously. A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system or PCE removal. This experiment was performed using a series of continuous-flow glass columns including a soil column, a peat column, followed by two consecutive soil columns. Anaerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for PCE biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts (trichloroethylene (TCE), cis-dichloroethylene (cis-DCE), vinyl chloride (VC), ethylene (ETH), and ethane). Results show that the decrease in PCE concentrations and production of PCE byproducts were observed over a 65-day operating period. Up to 98% of PCE removal efficiency was obtained in this passive system. Results indicate that the continuously released organics from peat column enhanced PCE biotransformation. Thus, the developed biobarrier treatment scheme has the potential to be developed into a cost-effective in situ PCE-remediation technology, and can be utilized as an interim step to aid in system scale-up.     

NPS MODEL PARAMETER UNCERTAINTY ANALYSIS FOR AN OFF-STREAM RESERVOIR1

ABSTRACT: Parameter uncertainties exert a significant effect on nonpoint source pollution (NPS) modeling results. A decision made on the basis of such results may thereby be inappropriate. In this work, the parameter uncertainty is analyzed to explore an improved modeling procedure. Drainage patterns generated from digital elevation data and rainfall are the major parameters examined. A case study for the watershed of the Posan off-stream reservoir is implemented. A significant spatial variation of NPS distribution simulated with a drainage pattern generated from varied methods is observed. The effects of rainfall randomness on the spatial loading distribution are assessed and computed based on a Monte Carlo simulation. The proposed procedure is capable of improving the quality of modeling results and the decision for an appropriate control strategy.     

Developments in forward osmosis and membrane distillation for desalination of waters

Membrane technology has become a common separation technology over the past decennia. Membranes are used more and more for the production of drinkable water from groundwater, surface water and wastewater. Membranes are now competitive versus conventional techniques. Desalination is predominantly used to eradicate the problem of water scarcity. The sustainability of all desalination processes depends mainly on the reduction of energy costs (production cost) and the increase in water recovery. Forward osmosis and membrane distillation are emerging technologies for sustainable desalination. Here we review membrane processes of forward osmosis and membrane distillation and the advancements in membrane material and modules. We also discuss the capability of membrane distillation in treating highly concentrated aqueous solutions derived from other desalination processes. Furthermore, the advancements in fabrication of high-performance membrane is reviewed and the performance of different membranes and optimization of membrane distillation process are summarized.     

Greenhouse gas emissions from landfill leachate treatment plants: A comparison of young and aged landfill

With limited assessment, leachate treatment of a specified landfill is considered to be a significant source of greenhouse gas (GHG) emissions. In our study, the cumulative GHG emitted from the storage ponds and process configurations that manage fresh or aged landfill leachate were investigated. Our results showed that strong CH₄ emissions were observed from the fresh leachate storage pond, with the fluxes values (2219–26,489 mg C m^?2 h^?1) extremely higher than those of N₂O (0.028–0.41 mg N m^?2 h^?1). In contrast, the emission values for both CH₄ and N₂O were low for the aged leachate tank. N₂O emissions became dominant once the leachate entered the treatment plants of both systems, accounting for 8–12% of the removal of N-species gases. Per capita, the N₂O emission based on both leachate treatment systems was estimated to be 7.99 g N₂O–N capita^?1 yr^?1. An increase of 80% in N₂O emissions was observed when the bioreactor pH decreased by approximately 1 pH unit. The vast majority of carbon was removed in the form of CO₂, with a small portion as CH₄ (<0.3%) during both treatment processes. The cumulative GHG emissions for fresh leachate storage ponds, fresh leachate treatment system and aged leachate treatment system were 19.10, 10.62 and 3.63 Gg CO₂ eq yr^?1, respectively, for a total that could be transformed to 9.09 kg CO₂ eq capita^?1 yr^?1.