On-Road Motor Vehicle Emissions and Fuel Consumption in Urban Driving Conditions

ABSTRACT

This paper reports on the analysis of on-road vehicle speed, emission, and fuel consumption data collected by four instrumented vehicles. Time-, distance-, and fuel-based average fuel consumption, as well as CO, HC, NO_x, and soot emission factors, were derived. The influences of instantaneous vehicle speed on emissions and fuel consumption were studied. It was found that the fuel-based emission factors varied much less than the time- and distance-based emission factors as instantaneous speed changed. The trends are similar to the results obtained from laboratory tests. The low driving speed contributed to a significant portion of the total emissions over a trip. Furthermore, the on-road data were analyzed using the modal approach. The four standard driving modes are acceleration, cruising, deceleration, and idling. It was found that the transient driving modes (i.e., acceleration and deceleration) were more polluting than the steady-speed driving modes (i.e., cruising and idling) in terms of g/km and g/ sec. These results indicated that the on-road emission measurement is feasible in deriving vehicle emissions and fuel consumption factors in urban driving conditions.     

Study on photocatalytic degradation of gaseous dichloromethane using pure and iron ion-doped TiO2 prepared by the sol-gel method

The synthesis of TiO₂ and Fe–TiO₂ by sol–gel method is demonstrated and characterized. The characterization of TiO₂ and Fe–TiO₂ is performed with instruments, including TGA/DTA, FTIR, UV–Vis, N₂ adsorption and SEM. Dichloromethane is used for the photocatalytic activity test. From the results of dichloromethane photocatalyitc degradation, the calcined temperature of TiO₂ and the presence of water vapor influence the photocatalytic activity. The optimum doping amount of iron ions is 0.005 mol%, and this can enhance the photocatalytic activity, while too great an amount will make the iron ions become recombination centers for the electron–hole pairs and reduce the photocatalytic activity. UV–Vis diffuse reflectance spectra of Fe–TiO₂ show an increase in absorbency in the visible light region with the increase in iron ions doping concentration The intermediate of dichloromethane photodegradation includes CHCl₃, CCl₄, CH₂Cl₂ and COCl₂. The presence of iron ions may reduce the adsorption of Cl element on the surface of the photocatalyst.     

Prediction of the adsorption capacity for volatile organic compounds onto activated carbons by the Dubinin-Radushkevich-Langmuir model

Prediction of the adsorption capacity for volatile organic compounds (VOCs) onto activated carbons is elucidated in this study. The Dubinin-Radushkevich (D-R) equation was first used to predict the adsorption capacity of nine aromatic and chlorinated VOCs onto two different activated carbons. The two key parameters of the D-R equation were estimated simply from the properties of the VOCs using quantitative structure-activity relationship and from the pore size distribution of the adsorbent. The approach based on the D-R equation predicted well the adsorption capacity at high relative pressures. However, at the relative pressures lower than -1.5 x 10(-3), the D-R approach may significantly overestimate adsorption capacity. To extrapolate the approach to lower relative pressures, the integration of the D-R equation and the Langmuir isotherm, called the D-R-L model, was proposed to predict adsorption capacity over a wide range of relative pressures of VOCs. In this model, the Langmuir isotherm parameters were extracted from the predicted D-R isotherm at high relative pressures. Therefore, no experimental effort was needed to obtain the parameters of the D-R-L model. The model successfully predicted the adsorption capacity of aromatic and chlorinated hydrocarbons tested onto BPL and Sorbonorit B carbons over relative pressures ranging from 7.4 x 10(-5) to 0.03, suggesting that the model is applicable at the low relative pressures of VOCs often observed in many environmental systems. In addition, the molecular size of organic compounds may be an important factor affecting the adsorption capacity of activated carbons. For BPL carbon, an ultramicroporous adsorbent, the limiting pore volume Wo of the D-R equation decreased when the kinetic diameter of the adsorbate was larger than 6 angstroms. However, for Sorbonorit B carbon, no reduction of Wo was found, suggesting that the Wo may be related to the pore size distribution of the adsorbents, as well as to their molecular size. This size exclusion effect may play an important role in predicting the adsorption capacity of VOCs onto microporous adsorbents in the D-R-L model and in the corresponding D-R equation.     

Simultaneous removal of sulfur dioxide and polycyclic aromatic hydrocarbons from incineration flue gas using activated carbon fibers

Incineration flue gas contains polycyclic aromatic hydrocarbons (PAHs) and sulfur dioxide (SO₂). The effects of SO₂ concentration (0, 350, 750, and 1000 ppm), reaction temperature (160, 200, and 280 °C), and the type of activated carbon fibers (ACFs) on the removal of SO₂ and PAHs by ACFs were examined in this study. A fluidized bed incinerator was used to simulate practical incineration flue gas. It was found that the presence of SO₂ in the incineration flue gas could drastically decrease removal of PAHs because of competitive adsorption. The effect of rise in the reaction temperature from 160 to 280 °C on removal of PAHs was greater than that on SO₂ removal at an SO₂ concentration of 750 ppm. Among the three ACFs studied, ACF-B, with the highest microporous volume, highest O content, and the tightest structure, was the best adsorbent for removing SO₂ and PAHs when these gases coexisted in the incineration flue gas.

ImplicationsSimultaneous adsorption of sulfur dioxide (SO₂) and polycyclic aromatic hydrocarbons (PAHs) emitted from incineration flue gas onto activated carbon fibers (ACFs) meant to devise a new technique showed that the presence of SO₂ in the incineration flue gas leads to a drastic decrease in removal of PAHs because of competitive adsorption. Reaction temperature had a greater influence on PAHs removal than on SO₂ removal. ACF-B, with the highest microporous volume, highest O content, and tightest structure among the three studied ACFs, was found to be the best adsorbent for removing SO₂ and PAHs.     

Feeding and metabolism effects of three common microplastics on Tenebrio molitor L.

Environmental Geochemistry and Health - Mealworms from three different regions: Guangzhou, Tai’an and Shenzhen, were fed with three commonly used microplastics of polystyrene (PS), polyvinyl...     

Contamination by arsenic and other trace elements in tube-well water and its risk assessment to humans in Hanoi, Vietnam

Concentrations of As and other trace elements and their association were examined in groundwater (n = 25) and human hair (n = 59) collected at Gia Lam District and Thanh Tri District, suburban areas of Hanoi, Vietnam, in September 2001. Concentrations of As in the groundwater ranged from <0.10 to 330 microg/l, with about 40% of these exceeding WHO drinking water guideline of 10 microg/l. Also, 76% and 12% of groundwater samples had higher concentrations of Mn and Ba than WHO drinking water guidelines, respectively. Arsenic concentrations in hair of residents in Gia Lam and Thanh Tri Districts (range 0.088-2.77 microg/g dry wt.) were lower than those in other As-contaminated areas of the world, but were higher than those of people in non-contaminated areas. Concentrations of As and Mn in hair of some individuals from the Gia Lam and Thanh Tri Districts exceeded the level associated with their toxicity and, therefore, a potential health risk of As and Mn is a concern for the people consuming the contaminated water in this area. Cumulative As exposure was estimated to be lower than the threshold levels at the present, which might explain the absence of manifestations of chronic As poisoning and arsenicosis in the residents of Gia Lam and Thanh Tri Districts. To our knowledge, this study revealed for the first time that the residents are exposed not only to As but also Mn and Ba from groundwater in the Red River Delta, Vietnam.     

Polyurethane foam (PUF) disks passive air samplers: wind effect on sampling rates

Different passive sampler housings were evaluated for their wind dampening ability and how this might translate to variability in sampler uptake rates. Polyurethane foam (PUF) disk samplers were used as the sampling medium and were exposed to a PCB-contaminated atmosphere in a wind tunnel. The effect of outside wind speed on PUF disk sampling rates was evaluated by exposing polyurethane foam (PUF) disks to a PCB-contaminated air stream in a wind tunnel over air velocities in the range 0 to 1.75 m s-1. PUF disk sampling rates increased gradually over the range 0-0.9 m s-1 at approximately 4.5-14.6 m3 d-1 and then increased sharply to approximately 42 m3 d-1 at approximately 1.75 m s-1 (sum of PCBs). The results indicate that for most field deployments the conventional 'flying saucer' housing adequately dampens the wind effect and will yield approximately time-weighted air concentrations.     

Mercury accumulation in surface sediments of salt marshes of the Bay of Fundy

Mercury contamination in Canada's Bay of Fundy is a priority concern because of elevated levels observed in fish, birds and wildlife. Salt marshes constitute an important part of the Bay's coastline and are potential stores of mercury for the region. We measured the amount of mercury accumulated over a 5-yr period from 1997 to 2002 in surface sediments of seven salt marshes along the New Brunswick coast of the Bay. The seven study sites extended from outer to inner Bay, spanning a gradient in tidal range (6-12 m) and sediment characteristics such as %LOI (4-29%) and sediment deposition rate (0.27-1.76 cm yr(-1)). In each study site, mercury was measured in low and high marsh areas. Sediment mercury concentrations ranged from 7 to 79 ng g(-1) and loading rates ranged from 0.1 to 1.1 mg m(-2). Total estimated 5-yr storage of mercury in salt marsh sediments of the Bay is 854+/-465 kg. We also compared sediment mercury loading to atmospheric inputs measured at a deposition monitoring station operating in New Brunswick from 1997 to 2002 and found that direct atmospheric deposition appears to be a minor input of mercury to these sediments. We are unaware of documentation of mercury loading in salt marshes on a bay-wide scale and over a constrained (5-yr) time period elsewhere.     

Characterizing driving patterns for Zhuhai for traffic emissions estimation

Zhuhai, a relatively less developed city on the western coast of the Pearl River Delta (PRD) of China, is planning to undergo major development in coming years. A Hong Kong-Zhuhai-Macao Bridge project has been approved by the Central Government of China. The project will have great impact on the driving pattern and vehicular emissions to the city. This baseline study collected speed-time data of two instrumented private cars in morning and evening periods, as well as a daytime nonpeak period of >10 consecutive days in the spring and winter of 2003. The authors used the microwave speed sensor and global positioning system installed in the instrumented cars and used car-chasing technique to perform the data collection. They used the statistical package SPSS to assess the consistency, as well as to evaluate the variability of the data. Nine parameters, namely, average speed, average running speed, average acceleration rate, average deceleration rate, mean length of a driving period, time proportions of driving modes, average number of acceleration-deceleration changes, root mean square acceleration, and positive acceleration kinetic energy are calculated to represent the driving characteristics. A driving cycle for private cars was developed. If emission tests were conducted using the Zhuhai driving cycle, the level of vehicle emissions measured is likely to be in between that of the Federal Test Procedure (FTP) cycle and the Melbourne Peak cycle.     

Determination of the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon using thermogravimetric analysis

This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared for use herein. The capacity of waste tire-derived PAC to adsorb vapor-phase HgCl2 was successfully measured using a self-designed TGA adsorption system. Experimental results showed that the maximum adsorptive capacities of HgCl2 were 1.75, 0.688, and 0.230 mg of HgCl2 per gram of powdered activated carbon derived from carbon black at 30, 70, and 150 degrees C for 500 microg/m3 of HgCl2, respectively. Four adsorption isotherms obtained using the Langmuir, Freundlich, Redlich-Peterson, and Brunauer-Emmett-Teller (BET) models were used to simulate the adsorption of HgCl2. The comparison of experimental data associated with the four adsorption isotherms indicated that BET fit the experimental results better than did the other isotherms at 30 degrees C, whereas the Freundlich isotherm fit the experimental results better at 70 and 150 degrees C. Furthermore, the calculations of the parameters associated with Langmuir and Freundlich isotherms revealed that the adsorption of HgCl2 by PAC-derived carbon black favored adsorption at various HgCl2, concentrations and temperatures.