摘要 :
Two Tunable Diode Laser Absorption Spectrometer (TDLAS) systems were used to measure HNO(sub 3). One system also measured formaldehyde (HCHO) atmosphere. Nitrogen dioxide (NO(sub 2)) was measured by the second TDLAS and by the LUM...
展开
Two Tunable Diode Laser Absorption Spectrometer (TDLAS) systems were used to measure HNO(sub 3). One system also measured formaldehyde (HCHO) atmosphere. Nitrogen dioxide (NO(sub 2)) was measured by the second TDLAS and by the LUMINOX, LMA-3 which is a new, small, simple and extremely sensitive instrument for NO(sub 2) measurements. The importance of these measurements is the role that NO(sub 2) plays as the direct precursor to gas phase HNO(sub 3). Agreement between the HNO(sub 3) measurements obtained by the 2 TDLAS systems were within the combined experimental errors. The diurnal behavior of the HNO(sub 3) concentrations were quite regular with a maximum occuring between 15:00 and 18:00 each day. Maximum concentrations of 18 ppbv were observed on September 14th. HCHO exhibited similar behaviour with the largest measured values of 14 ppbv occurring at 15:00 on the 13th. NO(sub 2) showed somewhat more variable behaviour generally with two maxima, one in the afternoon and one about mid-night. The TDLAS and LUMINOX were in good agreement with a few interesting exceptions.
收起
摘要 :
Progress is decribed for the first year of a two-year program designed to obtain data necessary for assessing the potential contribution of natural organics to the formation of photocheimcal air pollution in the California South C...
展开
Progress is decribed for the first year of a two-year program designed to obtain data necessary for assessing the potential contribution of natural organics to the formation of photocheimcal air pollution in the California South Coast Air Basin (CSCAB). Needed data include knowledge of emission rates, ambient concentrations and oxidant- and aerosol-forming potential of biogenic hydrocarbons as well as estimates of vegetative biomass in the CSCAB. During the initial year of this investigation, the following tasks were carried out: Oxidant-precursor relationships were determined for near-ambient concentrations of a-pinene based on data obtained with a 40,000-liter dual-mode outdoor irradiation chamber. Initial measurements were made of the ambient concentrations of natural hydrocarbons emitted by relevant vegetative communities in areas free of anthropogenic emissions. Plant enclosure chambers and analytical methods were developed for measuring the emission factors of isoprene and monoterpenes from natural, ornamental and agricultural vegetation in the 'source region' of the CSCAB. Studies were made of the feasibility of applying remote imagery techniques (including LANDSAT, U-2 and low altitude photography) to the task of quantifying the extent and mass of vegetation in the 'source region' of the CSCAB.
收起
摘要 :
The concentration of gaseous ammonia is a very important atmospheric chemical parameter affecting both the physical and chemical nature of several species. It is therefore very important to understand better the sources and the co...
展开
The concentration of gaseous ammonia is a very important atmospheric chemical parameter affecting both the physical and chemical nature of several species. It is therefore very important to understand better the sources and the concentrations of ammonia in the atmosphere, especially now that the ammonia injection process may be introduced as a means of reducing the oxides of nitrogen emission from stationary sources. Four analytical methods for the determination of ambient ammonia concentrations were evaluated, both in the laboratory and in the field. One method was chosen for additional field study, improvements were made, and field measurements were conducted at five sites in the South Coast Air Basin over a one-year period. The improved method utilized a specially constructed sampling system containing a Teflon prefilter to remove particulates followed by oxalic acid impregnated filters to trap ammonia gas.
收起
摘要 :
A combined experimental and chemical computer modeling research program has been carried out to develop and evaluate an experimental protocol for the determination of organic reactivities. A 4-component surrogate mixture was devel...
展开
A combined experimental and chemical computer modeling research program has been carried out to develop and evaluate an experimental protocol for the determination of organic reactivities. A 4-component surrogate mixture was developed to simulate the organics present in California's South Coast Air Basin, and incremental additions or deletions of the test organic were made to this 4-component surrogate mixture. In this series the standard mini-surrogate-NOx run was alternated with runs with added or removed test organics. As an integral part of this overall program, chemical kinetic computer modeling studies were also carried out using the most up-to-date kinetic and mechanistic data. The observed effects of added (or deleted) organics on the 4-component surrogate mixture are interpreted in terms of our current knowledge of the atmospheric chemistry of the organics studied, and the relevance of this research program to the development of emission control strategies by the CARB is discussed.
收起
摘要 :
The formation of sulfate and nitrate species in the California South Coast Air Basin (SoCAB) is a topic of great importance in air quality because these species lead to acid deposition, visibility degradation, and increased aeroso...
展开
The formation of sulfate and nitrate species in the California South Coast Air Basin (SoCAB) is a topic of great importance in air quality because these species lead to acid deposition, visibility degradation, and increased aerosol concentrations. The California Air Resources Board (CARB) has sponsored several field programs over the past four years to characterize the reactants, products, kinetics and mechanisms of stratus cloud chemistry in the SoCAB. In the study, a comprehensive computerized mathematical model of cloud chemistry and physics was used to investigate the chemical and physical processes that govern the formation of acidic species in clouds. First, the performance of the model treatment of equilibrium chemistry and chemical kinetics is evaluated. Then, the model was used to investigate the chemical pathways and transport processes that lead to acid formation in clouds and to study the sensitivity of the acid concentrations to various chemical and meteorological parameters.
收起
摘要 :
The study investigated the air quality impacts of methanol fuel use in the South Coast Air Basin. The results of the recently completed study are: Controlling emissions from mobile sources alone will not lead to achievement of the...
展开
The study investigated the air quality impacts of methanol fuel use in the South Coast Air Basin. The results of the recently completed study are: Controlling emissions from mobile sources alone will not lead to achievement of the National Ambient Air Quality Standard for ozone in Basin by year 2000 or 2010, use of methanol fuels can help in reducing ozone concentrations. As a side benefit, concentrations of PAN, NO2 and PM10 are also reduced, the amount of ozone reduction is sensitive to fuel type. M100 (100% methanol) fuel is twice as effective as M85 (85% methanol, 15% gasoline) fuel when results are compared to the baseline ozone concentration formed with the use of gasoline in advanced conventional vehicles, generally, formaldehyde levels in the atmosphere will remain unchanged with the use of methanol fuel. However, formaldehyde concentrations may increase or decrease somewhat at some of the sites, depending upon specific local conditions.
收起
摘要 :
The Van Nuys Tunnel experiment conducted in 1987 by Ingalls et al to verify automotive emission inventories as part of the Southern California Air Quality Study, gave higher CO and HC emission-rate values than expected on the basi...
展开
The Van Nuys Tunnel experiment conducted in 1987 by Ingalls et al to verify automotive emission inventories as part of the Southern California Air Quality Study, gave higher CO and HC emission-rate values than expected on the basis of automotive-emission models - by factors of approximately 3 and 4, respectively. The CO/NOx and HC/NOx emission-rate ratios moreover were higher than expected - by similar factors (NOx emission rates were about as expected). The purpose of the present paper is to review the literature on dynamometer and on-road (in tunnels and along roadways) testing of in-use vehicles, and on urban-air CO/HC/NOx concentration ratios, to see whether the Van Nuys Tunnel results are reasonable in terms of previous experience. The conclusions are that (1) on-road CO and HC emissions higher than expected have been reported before, (2) on-road CO and HC emissions consistent with the Van Nuys Tunnel results have been reported before, and (3) on-road CO/NOx and HC/NOx emission-rate ratios higher than expected have been reported before.
收起
摘要 :
Automated sub-event sequential rain samplers were used to sample rain during the winter and spring of 1987 in the South Coast Air Basin. Rainwater pH levels varied from 4 to 6 at West Los Angeles and Henninger Flats, from 4 to 5.5...
展开
Automated sub-event sequential rain samplers were used to sample rain during the winter and spring of 1987 in the South Coast Air Basin. Rainwater pH levels varied from 4 to 6 at West Los Angeles and Henninger Flats, from 4 to 5.5 at Pasadena, from 4.3 to 5.7 at Mt. Wilson, and from 4.5 to 6.8 at Riverside. Measurements of the atmospheric burdens of aerosol and gas phase species prior to a storm indicated that considerably more N(V) and S(IV) were deposited in rainfall than could be accounted for by pre-storm atmospheric burdens of these species while pre-storm burdens of CA(2+), Mg(2+), Na(+), and N(III) were closer to the measured deposition of these species in the rainfall. Concentrations of Na(+), CA(2+), and Mg(2+) were observed to be higher in larger droplets, and concentration of SO(4)(2-), NO(3-), NH(4+) and H(+) were higher in the small droplets. Aerosols and fog- and cloudwater were sampled during the Southern California Air Quality Study to assess the role that fog and cloud play in the formation of aerosol in the South Coast Air Basin and to quantify the scavenging of precursor aerosol and gases during droplet formation.
收起
