A new approach to in-situ determination of roadside particle emission factors of individual vehicles under conventional driving conditions

A method for continuous on-road measurements of particle number emissions for both diesel- and petrol-fuelled vehicles is presented. The setup allows the determination of particle number emission factors on an individual vehicle basis by the simultaneous measurement of CO₂ and particle concentrations. As an alternative to previous measurements on the kerbside, the sample is taken directly in the street, with the advantage of sampling in-situ within the exhaust plumes of passing vehicles, allowing the separation of the individual high-concentration plumes. The method was tested in two experiments that were conducted in the Gothenburg area. In the first study, which was performed at an urban roadside, we were able to determine particle emission factors from individual vehicles in a common car fleet passing the measurement site. The obtained emission factors were of the same order of magnitude (between 1.4 × 10¹² and 1.8 × 10¹⁴ particles km^?1) as values published in the recent literature for light duty vehicles. An additional on-road experiment was conducted at a rural road with four light duty reference vehicles (three of them petrol-powered and one diesel-powered) at driving speeds of 50 and 70 km h^?1, realised with different engine speeds. The results of the traffic emission studies show that the method is applicable provided that instruments with an adequate dynamic range are used and that the traffic is not too dense. In addition, the variability in particle emissions for a specified driving condition was estimated.     

APPLICATION OF GREY MODEL AND ARTIFICIAL NEURAL NETWORKS TO FLOOD FORECASTING1

The main focus of this study was to compare the Grey model and several artificial neural network (ANN) models for real time flood forecasting, including a comparison of the models for various lead times (ranging from one to six hours). For hydrological applications, the Grey model has the advantage that it can easily be used in forecasting without assuming that forecast storm events exhibit the same stochastic characteristics as the storm events themselves. The major advantage of an ANN in rainfall‐runoff modeling is that there is no requirement for any prior assumptions regarding the processes involved. The Grey model and three ANN models were applied to a 2,509 km² watershed in the Republic of Korea to compare the results for real time flood forecasting with from one to six hours of lead time. The fifth‐order Grey model and the ANN models with the optimal network architectures, represented by ANN1004 (34 input nodes, 21 hidden nodes, and 1 output node), ANN1010 (40 input nodes, 25 hidden nodes, and 1 output node), and ANN1004T (14 input nodes, 21 hidden nodes, and 1 output node), were adopted to evaluate the effects of time lags and differences between area mean and point rainfall. The Grey model and the ANN models, which provided reliable forecasts with one to six hours of lead time, were calibrated and their datasets validated. The results showed that the Grey model and the ANN1010 model achieved the highest level of performance in forecasting runoff for one to six lead hours. The ANN model architectures (ANN1004 and ANN1010) that used point rainfall data performed better than the model that used mean rainfall data (ANN1004T) in the real time forecasting. The selected models thus appear to be a useful tool for flood forecasting in Korea.     

尿中氚水和总氚的对比分析测定研究

用蒸馏液闪法测量尿中氚水浓度 ,用氧化蒸馏液闪法测量尿中总氚 (氚水和有机氚 )浓度。同时测量了 1999年核设施退役时接触氚人员的高于本底水平的尿中氚水和总氚浓度 72个样品。比较氚水和有机氚浓度 ,得到有机氚浓度占氚水浓度的平均值为 (5 4± 3 7) % ,其值与理论值和动物实验值基本相符     

Removal of organic matter and nitrogen from river water in a model floodplain

A significant improvement in river water quality cannot be expected unless nonpoint-source contaminants are treated in addition to the further treatment of point-source contaminants. If river water is sprayed over a floodplain, the consequent water filtration through the sediment profile can simultaneously remove organic matter and nitrogen in the water through aerobic and denitrifying reactions. This hypothesis was tested using lysimeters constructed from polyvinyl chloride (PVC) pipe (150 cm long, 15 cm in diameter) packed with loamy sand floodplain sediment. Water was applied to the top of the lysimeters at three different flow rates (48, 54, and 68 mm d(-1)). Concentrations of NO3 and dissolved oxygen (DO), chemical oxygen demand (COD), and redox potential (Eh) in the water were measured as functions of depth after the system reached steady states for both water flow and reactions. At the rate of 68.0 mm d(-1), a reducing condition for denitrification developed below the 5-cm depth due to the depletion of O2 by organic matter degradation in the surface oxidizing layer; Eh and DO were below 205 mV and 0.4 mg L(-1), respectively. At a depth of 70 cm, COD and NO3-N concentration decreased to 5.2 and 3.8 mg L(-1) from the respective influent concentrations of 17.1 and 6.2 mg L(-1). Most biodegradable organic matter was removed during flow and further removal of NO3 was limited by the lack of an electron donor (i.e., organic matter). These results indicate that the floodplain filtration technique has great promise for treatment of contaminated river water.     

Does the selection of ISO 14001 registrars matter? Registrar reputation and environmental policy statements in China

This study investigates the relationship between characteristics of environmental policy statements and the reputations of ISO 14001 registrars who had performed certification audits of firms operating in mainland China. Three characteristics of environmental policy statements were examined: (1) The conformance of the policy to strict interpretations of the international standard; (2) The policy statement's adherence to the good practice guidelines specified in ISO 14004; and, (3) Self-reported evaluations of the policy statement's effectiveness as implemented. Data from 106 facilities in Beijing, Shanghai and Guangzhou reveal that registrar quality has a relatively weak, positive relationship with conformance to both ISO 14001 standards and to ISO 14004 guidelines, but no relationship was observed with the self-reported data. Additional findings are that the use of foreign registrars is significantly associated with the adoption of ISO 14004 guidelines and that conformance with ISO 14001 standards is somewhat higher for international joint ventures and foreign-owned firms than for state-owned enterprises.     

Operational characteristics of effective removal of H2S and NH3 waste gases by activated carbon biofilter

Simultaneous removal of hydrogen sulfide (H2S) and ammonia (NH3) gases from gaseous streams was studied in a biofilter packed with granule activated carbon. Extensive studies, including the effects of carbon (C) source on the growth of inoculated microorganisms and gas removal efficiency, product analysis, bioaerosol emission, pressure drop, and cost evaluation, were conducted. The results indicated that molasses was a potential C source for inoculated cell growth that resulted in removal efficiencies of 99.5% for H2S and 99.2% for NH3. Microbial community observation by scanning electron microscopy indicated that granule activated carbon was an excellent support for microorganism attachment for long-term waste gas treatment. No disintegration or breakdown of biofilm was found when the system was operated for 140 days. The low bioaerosol concentration emitted from the biofilter showed that the system effectively avoided the environmental risk of bioaerosol emission. Also, the system is suitable to apply in the field because of its low pressure drop and treatment cost. Because NH3 gas was mainly converted to organic nitrogen, and H2S gas was converted to elemental sulfur, no acidification or alkalinity phenomena were found because of the metabolite products. Thus, the results of this study demonstrate that the biofilter is a feasible bioreactor in the removal of waste gases.     

EPR characterization of the catalytic activity of clays for PCE removal by gamma-radiation induced by acid and thermal treatments

Clays from tidal flat sediments showed efficient catalytic activity in the decomposition of PCE by gamma-radiation. The highest PCE removal of 98.6% was obtained with clays heated to 700 degrees C after acid treatment. The improved catalytic activity was identified by electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra of clays were significantly changed by the acid and thermal treatments. The intensity of a narrow signal at g=2 (signal III) was decreased with increasing thermal treatment temperature and this increased the PCE removal efficiency. The acid treatment completely removed a broad signal at g=2 (signal II), decreased the intensity of signal III, and improved the gamma-radiation treatment of PCE.     

A two-dimensional model for simulating the transport and fate of toxic chemicals in a stratified reservoir

A two-dimensional reservoir toxics model is essential to establishing effective water resources management and protection. In a reservoir, the fate of a toxic chemical is closely connected with flow regimes and circulation patterns. To better understand the kinetic processes and persistence and predict the dissipation of toxic contaminants in the reservoir during a spill or storm runoff event, a toxics submodel was developed and incorporated into an existing laterally integrated hydrodynamics and transport model. The toxics submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. The two-dimensional toxicant simulation model was applied to Shasta Reservoir in California to simulate the physico-chemical processes and fate of a volatile toxic compound, methyl isothiocyanate (MITC), during a chemical spill into the Sacramento River in 1991. The predicted MITC concentrations were compared with those observed. The effect of reservoir flow regimes on the transport and fate of the toxic substance was investigated. The results suggested that the persistence of MITC is significantly influenced by different flow regimes. Methyl isothiocyanate is more persistent in the reservoir under an interflow condition due to reduced volatilization from deep layers than under an overflow condition. In the overflow situation, the plume moved more slowly toward the dam and experienced greater dissipation. This analysis can assist in toxic spill control and reservoir management, including field sampling and closure of water intakes.     

Toxicity of carbaryl,diquat dibromide,and fluoranthene,individually and in mixture,to larval grass shrimp,Palaemonetes pugio

This study examined the toxicity of two pesticides (carbaryl and diquat dibromide) and one polycyclic aromatic hydrocarbon (fluoranthene), both singly and in mixture, to grass shrimp larvae (Palaemonetes pugio). These three chemicals are all present in coastal environments and can easily enter estuarine ecosystems. Fluoranthene was the most toxic chemical with a 96-h LC₅₀ value of 32.45 μ g/L, followed by carbaryl (43.02 μ g/L) and diquat dibromide (1624 μ g/L). In the chemical mixture tests, the binary carbaryl/diquat dibromide mixture and the ternary carbaryl/diquat dibromide/fluoranthene mixture had additive results.