Contribution of liquefied petroleum gas to air pollution in the metropolitan area of Mexico City

An estimation of hydrocarbon emissions caused by the consumption of liquefied petroleum gas (LPG) in the Metropolitan Area of Mexico City (MAMC) is presented. On the basis of experimental measurements at all points of handling, during the distribution process, and during the consumption of LPG in industrial devices and domestic appliances, an estimated 76,414 tons/year are released to the air. The most important contribution is found during the domestic consumption of LPG (70%); this makes the control initiatives available to the consumer. By developing a control program of LPG losses, a 77% reduction in emission is expected in a 5-yr period. The calculated amounts of LPG emissions when correlated with the consumption of LPG, combined with information from air samples from the MAMC, do not point to LPG emissions as the most important factor contributing to tropospheric ozone in the air in Mexico City.     

Effect of Liquefied Petroleum Gas on Ozone Formation in Guadalajara and Mexico City

Abstract

Leakages of liquefied petroleum gas (LPG) are suspected to contribute greatly to ozone (O₃) formation in Mexico City. We tested such a hypothesis by outdoor captive-air irradiation (CAI) experiments in the two largest Mexican metropolitan areas: Guadalajara (GMA) in 1997 and Mexico City (MCMA) in 2000. O₃ was monitored in each city for 20 days (8:00 a.m.–6:00 p.m.) in smog chambers containing unaltered morning air or morning air enriched with either commercial LPG or LPG synthetic mixture 60/40 (propane and butane). Tested additions of both components were 35% (by volume) in GMA and 60% (by volume) in MCMA. The addition effects on O₃ (max) were compared with effects from diluting LPG components or total nonmethane hydrocarbons (tNMHCs) by 50%. Diluting tNMHCs had the greatest absolute effect at both cities: it lowered O₃ (max) by 24% in GMA and 55% in MCMA. Adding commercial LPG increased O₃ (max) by 6% in GMA and 28% in MCMA; whereas adding LPG synthetic mixture 60/40 caused a similar increase in O₃ (max), 4 and 21% in GMA and MCMA, respectively. Compared with dilution of tNMHCs, dilution of LPG-associated compounds had a smaller decreasing effect on O₃ (max), only 4% in GMA and 15% in MCMA. These results show that commercial LPG and LPG synthetic mixture 60/40 affect O₃ formation to a lesser extent than estimated previously.     

Assessment of reducing ozone forming potential for vehicles using liquefied petroleum gas as an alternative fuel

Liquefied petroleum gas (LPG) is currently used in a small fleet of taxis as an alternative fuel to gasoline in Taipei, Taiwan as part of an incentive program promoted by Taiwan EPA to improve urban air quality. Under the test procedure in accordance with the US FTP-75 protocol to simulate an average urban driving pattern, the exhaust from four LPG and four gasoline-powered vehicles was analyzed for the percent composition of NMHCs. Emission factors for individual NMHCs were apportioned from the emission factors of total hydrocarbon based on chemical composition of the exhaust from both types of vehicles. After adjusting for ozone formation potential (OFP) by maximum incremental reactivity, the average OFP for LPG vehicles was estimated to be only 52.8% (g-O₃/veh-km) of the gasoline vehicles, or 3.3% of ozone reduction in Taipei metropolitan area, should all taxis be converted to LPG fuel.Composition analysis of the local LPG revealed that propane, butane and isobutane were the three major components and negligible amounts of alkenes were also found. In addition, the leakage from a LPG service station was substantially smaller than from a gasoline service station because of the closed design with the LPG pumping systems.     

液化石油气轿车实际道路污染物排放特征

利用PEMS对国2技术LPG出租轿车和汽油轿车的实际道路排放进行测试,基于测试数据对LPG轿车排放特征进行解析,并与汽油轿车的排放因子进行对比分析.结果显示:速度和行驶模式对LPG轿车污染物排放影响明显;LPG轿车CO 2、CO、HC和NOx污染物的实测排放因子分别为(169.5±22.2)、(2.18±2.38)、(...     

Emissions of liquefied petroleum gas (LPG) from motor vehicles

Continuous on-site measurements of 50 speciated volatile organic compounds (VOCs) were conducted in downtown Guangzhou to characterize the sources and concentration profiles of ambient VOCs. The synchronicity in diurnal variation between the VOCs and NO suggests that traffic emissions were responsible for the observed VOCs in downtown Guangzhou.It was found that the three major constituent species of liquefied petroleum gas (LPG), i.e., propane, iso-butane, and n-butane, together termed LPG alkanes, contributed, on average, 24% of the total VOCs (TVOCs). Their high correlation and synchronized diurnal variations between NO and the LPG alkanes suggest that their origin lies in LPG fueled car exhaust in Guangzhou. LPG buses and taxis were likely to be responsible for the bulk of ambient LPG species. Using propane and 3-methyl pentane (3MC5A) as the indicators for the LPG and gasoline emissions, respectively, the emissions of the LPG fleet were found to increase more than those of the gasoline fleet during the morning and evening rush hours, as well the noontime break in downtown Guangzhou.Although LPG alkanes account for 24% of the TVOC, their contribution to the total ozone forming potential (OFP) is only about 7%. Ethylene and propylene contribute about 26% to the total OFP despite their lower contribution of 16% to the TVOC.     

On-road remote sensing of liquefied petroleum gas (LPG) vehicle emissions measurement and emission factors estimation

In the present study, the real-world on-road liquefied petroleum gas (LPG) vehicle/taxi emissions of carbon monoxide (CO), hydrocarbon (HC) and nitric oxide (NO) were investigated. A regression analysis approach based on the measured LPG vehicle emission data was also used to estimate the on-road LPG vehicle emission factors of CO, HC and NO with respect to the effects of instantaneous vehicle speed and acceleration/deceleration profiles for local urban driving patterns. The results show that the LPG vehicle model years and driving patterns have a strong correlation to their emission factors. A unique correlation of LPG vehicle emission factors (i.e., g km⁻¹ and g l⁻¹) on different model years for urban driving patterns has been established. Finally, a comparison was made between the average LPG, and petrol [Chan, T.L., Ning, Z., Leung, C.W., Cheung, C.S., Hung, W.T., Dong, G., 2004. On-road remote sensing of petrol vehicle emissions measurement and emission factors estimation in Hong Kong. Atmospheric Environment 38, 2055–2066 and 3541] and diesel [Chan, T.L., Ning, Z., 2005. On-road remote sensing of diesel vehicle emissions measurement and emission factors estimation in Hong Kong. Atmospheric Environment 39, 6843–6856] vehicle emission factors. It has shown that the introduction of the replacement of diesel taxis to LPG taxis has alleviated effectively the urban street air pollution. However, it has demonstrated that proper maintenance on the aged LPG taxis should also be taken into consideration.     

The environmental Kuznets curve hypothesis for Bangladesh: the importance of natural gas,liquefied petroleum gas,and hydropower consumption

Environmental Science and Pollution Research - Mitigating environmental pollution has become a global agenda keeping the sustainability of socioeconomic and environmental development into...     

Tethered balloon-based soundings of ozone,aerosols, and solar radiation near Mexico City during MIRAGE-MEX

A tethered balloon sampling system was used to measure vertical profiles of ozone, particles, and solar radiation in the atmospheric boundary layer on the northern edge of Mexico City, in March 2006 as part of the Megacity Impact on Regional and Global Environment-Mexico experiment. Several commercial sensors, designed for surface applications, were deployed on a tethered balloon platform.Profiles indicate that for these 3 scalars the boundary layer (surface up to 700 m) was well mixed in the period 10:00–16:00 LST. Good agreement was observed for median surface and balloon ozone and particle number concentrations. For most profiles, the surface deposition of ozone was not significant compared to median profile concentrations. Particle number concentration (0.3, 0.5, 1.0 and 5.0 μm) also showed little variation with attitude. Radiatprofiles showed a monotonic increase in diffuse radiation from the maximum altitude of profiles to the surface. Consequently, it was inferred that surface measurements of these likely were representative of lower boundary layer values during this time period.     

Atmospheric ozone: formation and effects on vegetation

Ozone (O(3)) is present both in the troposphere and the stratosphere. Troposphere O(3) is predominantly produced by photochemical reactions involving precursors generated by natural processes and to a much larger extent by man's activities. There is evidence for a trend towards increasing tropospheric O(3) concentrations. However, tropospheric O(3) is known to account for only 10% of the vertical O(3) column above the earth's surface. The stratosphere accounts for an additional 90% of the O(3) column. There is evidence to suggest that there are losses in the stratospheric O(3) due to the updraft of O(3) destroying pollutants generated by both natural processes and by human activity. Such a loss in stratospheric O(3) can result in alterations of incidence in the ultraviolet (UV) radiation to the earth's surface. Tropospheric O(3) is known to be highly phytotoxic. Appropriate exposures to O(3) can result in both acute (symptomatic) and chronic (changes in growth, yield or productivity and quality) effects. Chronic effects are of great concern in terms of both crops and forests. A number of experimental techniques are available to evaluate the chronic effects of O(3) on plants. There are limitations attached to the use of these techniques. However, results obtained, with such techniques are valuable if interpreted in the appropriate context. Among all field evaluation techniques, open-top chambers are the most frequently used method for evaluating the chronic effects of O(3) on crops. The National Crop Loss Assessment Program (NCLAN) of the United States is the largest such effort. However, given the limitations of the open-top chambers and the experimental aspects of NCLAN, its results must be interpreted with caution. On the other hand, acute effects can be evaluated with less complexity through the use of biological indicator plants. The numerical modelling of such effects are also far less complicated than establishing numerical cause and effects relationships for chronic effects. Confounding the acute or chronic responses of plants to O(3), is the presence of other kinds and forms of pollutants in the ambient atmosphere and the incidence of pathogens and pests. The resulting complex interactions and joint effects on plants are poorly understood. Future research must address these issues. In the final analysis we have re-emphasized the fact that plant health is the product of its interaction with the physical and chemical climatology and pathogens and pests. What we have described in this context is the importance of tropospheric O(3) within the chemical climatology of our environment and its effects on vegetation.     

Contribution of LPG-Derived Emissions to Air Pollution in the Metropolitan Area of Guadalajara City

ABSTRACT

Measurements of hydrocarbon (HC) emissions generated by the use of liquefied petroleum gas (LPG) in the metropolitan area of Guadalajara City (MAG) are presented in this work. Based on measurements in the course of distribution, handling, and consumption, an estimated 4407 tons/yr are released into the atmosphere. The three most important contributors to LPG emissions were refilling of LPG-fueled vehicles and commercial and domestic consumption. The MAG shows a different contribution pattern of LPG emission sources compared with that of the metropolitan area of Mexico City (MAMC). These results show that each megacity has different sources of emissions, which provides more accurate strategies in the handling procedures for LPG to decrease the impact in O₃ levels. This work represents the first evaluation performed in Guadalajara City, based on current measurements, of the LPG contribution to polluting emissions.     

Contribution of LPG-derived emissions to air pollution in the metropolitan area of Guadalajara City

Measurements of hydrocarbon (HC) emissions generated by the use of liquefied petroleum gas (LPG) in the metropolitan area of Guadalajara City (MAG) are presented in this work. Based on measurements in the course of distribution, handling, and consumption, an estimated 4407 tons/yr are released into the atmosphere. The three most important contributors to LPG emissions were refilling of LPG-fueled vehicles and commercial and domestic consumption. The MAG shows a different contribution pattern of LPG emission sources compared with that of the metropolitan area of Mexico City (MAMC). These results show that each megacity has different sources of emissions, which provides more accurate strategies in the handling procedures for LPG to decrease the impact in O3 levels. This work represents the first evaluation performed in Guadalajara City, based on current measurements, of the LPG contribution to polluting emissions.     

Sensitivity of ozone concentrations to diurnal variations of surface emissions in Mexico City: A WRF/Chem modeling study

Sensitivity of ozone (O₃) concentrations in the Mexico City area to diurnal variations of surface air pollutant emissions is investigated using the WRF/Chem model. Our analysis shows that diurnal variations of nitrogen oxides (NO_x = NO + NO₂) and volatile organic compound (VOC) emissions play an important role in controlling the O₃ concentrations in the Mexico City area. The contributions of NO_x and VOC emissions to daytime O₃ concentrations are very sensitive to the morning emissions of NO_x and VOCs. Increase in morning NO_x emissions leads to decrease in daytime O₃ concentrations as well as the afternoon O₃ maximum, while increase in morning VOC emissions tends to increase in O₃ concentrations in late morning and early afternoon, indicating that O₃ production in Mexico City is under VOC-limited regime. It is also found that the nighttime O₃ is independent of VOCs, but is sensitive to NO_x. The emissions of VOCs during other periods (early morning, evening, and night) have only small impacts on O₃ concentrations, while the emissions of NO_x have important impacts on O₃ concentrations in the evening and the early morning.This study suggests that shifting emission pattern, while keeping the total emissions unchanged, has important impacts on air quality. For example, delaying the morning emission peak from 8 am to 10 am significantly reduced the morning peaks of NO_x and VOCs, as well as the afternoon O₃ maxima. It suggests that without reduction of total emission, the daytime O₃ concentrations can be significantly reduced by changing the diurnal variations of the emissions of O₃ precursors.     

Formaldehyde levels in air and wet precipitation at Mexico City, Mexico

Formaldehyde concentrations in ambient air and in rain water were measured at the University of Mexico, Mexico City. Air samples were taken twice a day, from 9:00 to 13:00 h and from 13:00 to 16:00 h local time from July to December 1985. Rain water was collected on daily bases from July to October, i.e. during the rainy season. The ambient air mean value was 24.4 x 10(-3) ppmv for morning hours, while the afternoon mean value was 18.5 x 10(-3) ppmv. The formaldehyde concentration in wet precipitation ranged from 0.10 to 0.80 mg liter(-1) (3.3 to 26.6 micromoles liter(-1)) 0.41 mg liter(-1) (13.7 microoles liter(-1)). A comparison of the results of this study with some measurements made at remote maritime sites, rural and urban areas, indicated that the formaldehyde levels in the atmosphere and rain water of Mexico City are among the highest reported in the literature, including the data reported by Grosjean (1982) for Los Angeles, California, during severe photochemical pollution conditions.     

Effects of reactive hydrocarbons on ozone formation in southern Taiwan

Ambient air samples were collected at 13 air quality monitoring stations in Kaohsiung city, Kaohsiung county, and Pingtung county (KKP) to investigate the composition and spatial distribution of C₂–C₁₀ non-methane hydrocarbons (NMHCs) in southern Taiwan. Ozone formation potentials (OFPs) of NMHCs were estimated using maximum incremental reactivity (MIR) and k_OH method (reactivity of NMHC with OH radical) to assess the relative effects of hydrocarbons on ozone formation. The measurements showed that mixing ratios of toluene, ethene, ethyne, ethane, isopantane and propane were the highest among all measured species at most of the sampling sites. Nevertheless, considering both the photochemical reactivities and mixing ratios of all the measured species, toluene, xylene, ethene and propene were calculated to have the highest OFPs and reactivities. The OFPs and reactivities assessed by the MIR and k_OH methods for the four compounds accounted for 54.5% and 39.3% of all the measured species. Larger benefit margin of ozone abatement may be obtained by reducing emissions of a group of key species with high OFPs.2,2-dimethylbutane (22DMC4) was used as an indicator of traffic emissions to distinguish traffic from non-traffic contributions of key species in Kaohsiung metropolitan area. It revealed that the contribution of non-traffic source was significant for toluene, whereas xylene was found to be primarily from the traffic source in Kaohsiung metropolitan area during the sampling periods.     

Partitioning of nitrate and ammonium between the gas and particulate phases during the 1997 IMADA-AVER study in Mexico City

The partitioning of nitrate and ammonium between the gas and particulate phases is studied combining available equilibrium models and measurements taken in Mexico City during the 1997 IMADA-AVER field campaign. Based on this analysis, there are no significant differences in model predictions, but some discrepancies exist between predictions and observations. The inclusion of crustal elements in the modeling framework improves agreement of model predictions for particulate nitrate against measurements by approximately 5%. Although some equilibrium aerosol models do not explicitly treat crustal elements, these species can be treated as equivalent concentrations of sodium. Atmospheric equilibrium models predict daily average PM_2.5 nitrate concentrations within 20% of the IMADA-AVER measurements at the MER site. Six-hour average PM_2.5 nitrate concentrations are predicted within 30–50% on average except for the afternoon sampling periods (12:00–18:00 h). Investigating the possible sources of these discrepancies, it appears that a dynamic instead of an equilibrium approach is more suitable in reproducing aerosol behavior during these afternoon periods. By applying the Multicomponent Aerosol Dynamic Model (MADM), model performance in predicting concentrations of particulate nitrate significantly improves during the afternoon periods.     

Photochemical ozone formation in the Sydney airshed

The theoretical photostationary state relationship, k₃[O₃][NO]/k₁[NO₂] = 1, was tested in the free atmosphere using data obtained from a series of air mass trajectory experiments which were performed as part of the Sydney Oxidant Study. These data show that in general, the relationship was valid to within a factor of two for the Sydney airshed when three minute averaged concentration measurements were used. The effects of various averaging times upon the experimental photostationary state relationship arc discussed.     

Feasibility of landfill gas as a liquefied natural gas fuel source for refuse trucks

The purpose of this paper is to develop a methodology to evaluate the feasibility of using landfill gas (LFG) as a liquefied natural gas (LNG) fuel source for heavy-duty refuse trucks operating on landfills. Using LFG as a vehicle fuel can make the landfills more self-sustaining, reduce their dependence on fossil fuels, and reduce emissions and greenhouse gases. Acrion Technologies Inc. in association with Mack Trucks Inc. developed a technology to generate LNG from LFG using the CO2 WASH process. A successful application of this process was performed at the Eco Complex in Burlington County, PA. During this application two LNG refuse trucks were operated for 600 hr each using LNG produced from gases from the landfill. The methodology developed in this paper can evaluate the feasibility of three LFG options: doing nothing, electricity generation, and producing LNG to fuel refuse trucks. The methodology involved the modeling of several components: LFG generation, energy recovery processes, fleet operations, economic feasibility, and decision-making. The economic feasibility considers factors such as capital, maintenance, operational, and fuel costs, emissions and tax benefits, and the sale of products such as surplus LNG and food-grade carbon dioxide (CO2). Texas was used as a case study. The 96 landfills in Texas were prioritized and 17 landfills were identified that showed potential for converting LFG to LNG for use as a refuse truck fuel. The methodology was applied to a pilot landfill in El Paso, TX. The analysis showed that converting LFG to LNG to fuel refuse trucks proved to be the most feasible option and that the methodology can be applied for any landfill that considers this option.     

PM composition and source reconciliation in Mexico City

PM_2.5 and PM₁₀ were collected during 24-h sampling intervals from March 1st to 31st, 2006 during the MILAGRO campaign carried out in Mexico City's northern region, in order to determine their chemical composition, oxidative activity and the estimation of the source contributions during the sampling period by means of the chemical mass balance (CMB) receptor model. PM_2.5 concentrations ranged from 32 to 70 μg m⁻³ while that of PM10 did so from 51 to 132 μg m⁻³. The most abundant chemical species for both PM fractions were: OC, EC, SO₄²⁻, NO₃⁻, NH₄⁺, Si, Fe and Ca. The majority of the PM mass was comprised of carbon, up to about 52% and 30% of the PM2.5 and PM10, respectively. PM2.5 constituted more than 50% of PM10. The redox activity, assessed by the dithiothreitol (DTT) assay, was greater for PM_2.5 than for PM₁₀, and did not display significant differences during the sampling period. The PM_2.5 source reconciliation showed that in average, vehicle exhaust emissions were its most important source in an urban site with a 42% contribution, followed by re-suspended dust with 26%, secondary inorganic aerosols with 11%, and industrial emissions and food cooking with 10% each. These results had a good agreement with the Emission Inventory. In average, the greater mass concentration occurred during O₃S that corresponds to a wind shift initially with transport to the South but moving back to the North. Taken together these results show that PM chemical composition, oxidative potential, and source contribution is influenced by the meteorological conditions.     

The influence of aerosols on photochemical smog in Mexico City

Aerosols in the Mexico City atmosphere can have a non-negligible effect on the ultraviolet radiation field and hence on the formation of photochemical smog. We used estimates of aerosol optical depths from sun photometer observations in a detailed radiative transfer model, to calculate photolysis rate coefficients (J_NO2) for the key reaction NO₂+hν→NO+O (λ<430 nm). The calculated values are in good agreement with previously published measurements of J_NO2at two sites in Mexico City: Palacio de Minerı́a (19°25′59″N, 99°07′58″W, 2233 masl), and IMP (19°28′48″N, 99°11′07″W, 2277 masl) and in Tres Marias, a town near Mexico City (19°03′N, 99°14′W, 2810 masl). In particular, the model reproduces very well the contrast between the two urban sites and the evidently much cleaner Tres Marias site. For the measurement days, reductions in surface J_NO2 by 10–30% could be attributed to the presence of aerosols, with considerable uncertainty due largely to lack of detailed data on aerosol optical properties at ultraviolet wavelengths (esp. the single scattering albedo). The potential impact of such large reductions in photolysis rates on surface ozone concentrations is illustrated with a simple zero-dimensional photochemical model.     

Photochemical formation and transport of ozone in Athens,Greece

An evaluation of the diurnal variation of the hourly ozone concentrations measured at five sites in Greater Athens from June until early September 1984 indicates that photosmog episodes in Greater Athens are associated with the sea breeze circulation. Due to local air circulation in the Athens basin, precursors of O₃ are transported to and accumulated in the Saronikos Bay during the morning hours while the land breeze is blowing. At noon, when the sea breeze sets in, the O₃ formed over the sea is brought back to the coast and to central Athens where it increases the local O₃ concentration by a factor of 3–5 within a few hours. The O₃ levels often remain high throughout the night. During the photochemical smog episodes, all of them accompanied by well-developed sea breezes, the U.S. Air Quality Standard of 120 ppb O₃ was exceeded for 4–7 h day⁻¹. Peak O₃ concentrations up to nearly 200 ppb were recorded in the smog episodes.Relatively high O₃ concentrations were measured on the island of Aegina. They tend to remain high during the night and can be attributed only to primary pollutant transport from Greater Athens advected by the land breeze. The O₃ values obtained at Mount Immitos (1000 m above MSL) suggest that, first, the sea breeze inhibits the influence of vertical thermal convection up to heights above 600 m, and second, no O₃ is noticeable from above the tropopause to ground level or from long-range transport.