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801.
Four kinds of woods used for residential heating in Australia were selected and burned under two burning conditions in a domestic wood heater installed in a laboratory. The selected wood species included pine (Pinus radiata), red gum (Eucalvptus camaldulensis), sugar gum (Eucalyptus cladocalyx) and yellow box (Eucalyptus melliodora). The two different burning conditions represented fast burning and slow burning, with the air inlet of the combustion chamber respectively 'full open' and 'half open'. By sampling and analysing particulate and gaseous emissions from the burning of each load of wood under defined experimental conditions, PAHs emissions and their profiles in the particulate and gaseous phases were obtained. 16 species out of the 18 selected PAHs were detected. Of these, seven species were detected in the gaseous phase and most were lower molecular weight compounds.Similarly, more than 10 species of PAHs were detected in the particulate phase and these were mostly heavier molecular weight compounds. Under both burning conditions, emission levels for total PAHs and total genotoxic PAHs were the highest for pine and lowest for sugar gum, with red gum being the second highest, followed by yellow box. Using the specific sampling method, gaseous PAHs accounted for above 90% mass fraction of total PAHs in comparison to particulate PAHs (10%). The majority of the genotoxic PAHs were present in the particulate phase. PAHs emission levels in slow burning conditions were generally higher than those in fast burning conditions. 相似文献
802.
The effect of sediment sources on the selection of polychlorinated biphenyl (PCB) dechlorinating competence was investigated using sediments from two different locations, the Grasse River and Owasco Lake. These two sediments had a similar organic carbon content but different particle size distribution. The two PCB-free sediments were spiked with Aroclor 1248 and inoculated with microorganisms from the Reynolds and General Motors sites in the St. Lawrence River, which exhibited different dechlorination patterns. When each inoculum was serially transferred into fresh sediments four times (every 8-10 weeks), they still maintained the initial dechlorination patterns regardless, the source of sediments and the number of transfers, and dechlorination patterns of the two inocula in the same sediments did not converge. In a parallel approach, when the acclimated microorganisms from the Reynolds site were inoculated into fresh sediments from both sources as well as sediments enriched with organic carbon (2%, w/v), the dechlorination pattern remained unchanged after a 40-week incubation. These results suggest that the sediment characteristics or organic carbon content did not play a role in the selection of dechlorinating populations. 相似文献
803.
This study measured the levels of 17 congeners of PCDDs/PCDFs in serum to compare the levels between potentially exposed workers at an industrial waste incinerator and any residents with no known exposures. The 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDD were detected in serum of workers but in controls. Likewise, 1,2,3,7,8-PeCDF, 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDF were detected only in serum of workers. The international toxic equivalent (TEQ) levels of PCDDs/PCDFs in sera of workers are much higher than in controls. Among PCDDs, the proportion of total concentration and TEQ level is dominated predominantly by 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDD. We need extensive studies to estimate human exposure and are continuing this investigation. 相似文献
804.
Holmén BA Niemeier DA Meng Y 《Journal of the Air & Waste Management Association (1995)》2001,51(4):601-615
On November 18, 1997, above-road particulate matter (PM) lidar (light detection and ranging) signals and heavy-duty (HD) and light-duty (LD) vehicle counts were simultaneously collected for 894 10-sec sampling periods at the Caldecott Tunnel in Orinda, CA, for the purpose of measuring the relative contributions of LD and HD vehicles to the PM lidar signal under real-world driving conditions. The relationship between the PM lidar signal and traffic activity (i.e., LD and HD traffic volumes) was examined using a time-series analysis technique, multilagged regression. The time-series model results indicate that the PM lidar signal in the current sampling period (PMt) depended on the level recorded in the previous three sampling periods (i.e., PMt-1, PMt-2, and PMt-3), the number of LD vehicles in the seventh past sampling period (LDt-7), and the number of HD vehicles measured 80 sec previous to the current sampling period (HDt-8). On a 10-sec period basis, the model results indicate that HD vehicles contributed, on average, 3 times more to above-road PM lidar signals than did LD vehicles. The observed lag in the relationship between vehicle types and the lidar signal 20 m above the road suggests that resuspended road dust, rather than tailpipe exhaust emissions, was the main source of the detected PM. Detection of road dust at such heights above the road suggests the need for investigating the processes governing the vertical transport and recycling of PM over the road as a function of vehicle dynamics under a range of meteorological conditions. 相似文献
805.
Persistence of residues in water and sediment of a fresh-water lake after surface application of technical chlordane 总被引:1,自引:0,他引:1
P C Oloffs L J Albright S Y Szeto 《Journal of environmental science and health. Part. B》1978,13(1):47-58
A fresh-water lake, free from detectable pesticide residues before this study, was treated with a commercial formulation of technical chlordane. Water and sediment samples were analysed for chlordane residues 7, 24, 52, 279. and 421 days after treatment. Residues moved rapidly from the water to the lake bottom, supporting earlier results of a laboratory study with other organochlorines. In water, alpha- and gamma-chlordane concentrations remained proportional to total chlordane concentrations, as determined by total-peak area measurements of gas-liquid chromatogrammes. But in bottom sediments, alpha- and gamma-chlordane were more persistent than other constituents of technical chlordane, supporting recent evidence that quantification of technical chlordane residues on the basis of gamma-chlordane quantification only (or that of alpha- and gamma-chlordane only), can lead to incorrect results and that this method, although simple and fast, should no longer be recommended. 相似文献
806.
ATP pools in pure and mixed cultures 总被引:1,自引:0,他引:1
I C Kao S Y Chiu L T Fan L E Erickson 《Journal - Water Pollution Control Federation》1973,45(5):926-931
807.
The objectives of the present research were (i) to report the mass balance of chlorine during pentachlorophenol (PCP) photodegradation and (ii) to reveal the photodegradation pathway experimentally with a theoretical proof based on the density functional theory (DFT). The chlorine of PCP was completely mineralized to produce chloride ions after 24h of UV irradiation. As intermediates, 2,3,5,6-tetrachlorophenol, 2,3,4,6-tetrachlorophenol and 2,5-dichlorophenol were identified. At least 80% of the chlorine balance during PCP photodegradation was accounted by PCP, these intermediates, and chloride ions. A DFT calculation showed differences in the C-Cl bond dissociation energy level and the positions of respective PCP molecular and the PCP intermediates. The dechlorination intermediates predicted using the calculated C-Cl bond dissociation energy were consistent with those experimentally confirmed, indicating the feasibility of this theoretical method in predicting the dechlorination pathway. 相似文献
808.
Z. Ning C.S. Cheung Y. Lu M.A. Liu W.T. Hung 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):7880-7893
The aim of the work presented here is to study experimentally and numerically the dispersion characteristics of vehicular exhaust plume at an idle condition in an idealized and simplified environment. The gaseous and particulate concentrations in the exhaust plume of three idling motor vehicles were measured in an isolated environment under calm weather conditions. Despite the difference in the initial concentrations, the pollutants decayed exponentially in all directions.The CFD code PHOENICS 3.3, with the k–ε eddy dissipation sub-model, was used for the numerical simulation. The simulated results match very well with the experimental results close to the source of emission but decay to the ambient concentrations much slower. The effects of the initial emission concentration, exit velocity, exit direction and crosswind intensity have been investigated parametrically. The initial pollutant concentration will increase the local concentrations but the pattern of dispersion remains the same. The exit velocity will increase the momentum of the jet, resulting in a deeper penetration downstream. The exit angle has a stronger influence on pollutant dispersion than both initial pollutant concentration and exit velocity. When the exit angle is 15°, the pollutants tend to spread on the ground region. Crosswind shows a significant effect on the dispersion of the exhaust plume also. It will divert the plume to disperse in the same direction of the wind with limited penetration in the downstream direction. 相似文献
809.
Use of autotrophic sulfur-oxidizers to remove nitrate from bank filtrate in a permeable reactive barrier system 总被引:1,自引:0,他引:1
Moon HS Ahn KH Lee S Nam K Kim JY 《Environmental pollution (Barking, Essex : 1987)》2004,129(3):499-507
This study was conducted to evaluate the potential applicability of an in situ biological reactive barrier system to treat nitrate-contaminated bank filtrate. The reactive barrier consisted of sulfur granules as an electron donor and autotrophic sulfur-oxidizing bacteria as a biological component. Limestone was also used to provide alkalinity. The results showed that the autotrophic sulfur oxidizers were successfully colonized on the surfaces of the sulfur particles and removed nitrate from synthetic bank filtrate. The sulfur-oxidizing activity continuously increased with time and then was maintained or slightly decreased after five days of column operation. Maximum nitrate removal efficiency and sulfur oxidation rate were observed at near neutral pH. Over 90% of the initial nitrate dissolved in synthetic bank filtrate was removed in all columns tested with some nitrite accumulation. However, nitrite accumulation was observed mainly during the initial operation period, and the concentration markedly diminished with time. The nitrite concentration in effluent was less than 2 mg-N/l after 12 days of column operation. When influent nitrate concentrations were 30, 40, and 60 mg-N/l and sulfur content in column was 75%, half-order autotrophic denitrification reaction rate constants were 31.73 x 10(-3), 33.3 x 10(-3), and 36.4 x 10(-3) mg(1/2)/l(1/2)min, respectively. Our data on the nitrate distribution profile along the column suggest that an appropriate wall thickness of a reactive barrier for autotrophic denitrification may be 30 cm when influent nitrate concentration is less than 60 mg-N/l. 相似文献
810.
Chen YH Chang CY Chen CC Chiu CY Yu YH Chiang PC Ku Y Chen JN Chang CF 《Chemosphere》2004,56(2):133-140
This study investigates the ozonation of 2-mercaptothiazoline (2-MT). The 2-MT is one of the important organic additives for the electroplating solution of the printed wiring board industry and has been widely used as a corrosion inhibitor in many industrial processes. It is of concern for the aquatic pollution control especially in the wastewaters. Semibatch ozonation experiments in the completely stirred tank reactor are performed under various concentrations of input ozone. The concentrations of 2-MT, sulfate, and ammonium are analyzed at specified time intervals to elucidate the decomposition of 2-MT during the ozonation. In addition, the time variation of the dissolved ozone concentration (C(ALb)) is continuously monitored in the course of experiments. Total organic carbon (TOC) is chosen and measured as a mineralization index of the ozonation of 2-MT. The results indicate that the decomposition of 2-MT is efficient, while the mineralization of TOC is limited via the ozonation only. Simultaneously, the yield of sulfate with the maximum value of about 47% is characterized by the increases of TOC removal and ozone consumption. These results can provide some useful information for assessing the feasibility of the treatment of 2-MT in the aqueous solution by the ozonation. 相似文献