Photochemical Reactivities of Exhausts from 1966 Model Automobiles Equipped to Reduce Hydrocarbon Emissions

During the summer of 1966, a selected group of automobiles from the Cincinnati phase of the GSA study were used in an irradiation chamber study. The study was conducted to evaluate the photochemical air pollution potential of representative models of the equipped and unequipped automobiles. Only one set of automobiles, the unequipped Chevelles, produced exhaust capable upon irradiation of forming significant levels of oxidant and PAN. Neither the equipped Chevelles nor any of the Fords or Plymouths, whether equipped or unequipped, produced exhaust having the characteristics necessary to form oxidant or PAN upon irradiation. The eye irritation level reported by the panel upon irradiation of exhaust from unequipped Chevelles was much higher than that produced by the irradiated exhausts from any of the other types of automobiles. Overall, there does appear to be some small improvement with respect to eye irritation in comparing equipped with unequipped automobiles. To a large extent, the improvement in the air pollution potential of exhaust from equipped Chevelles compared to the unequipped Chevelles can be attributed to the reduction in the hydrocarbon to nitrogen oxide ratio. The irradiated exhaust from equipped Chevelles, except for aldehyde levels, is about the same in photochemical air pollution potential as are the exhausts from both equipped and unequipped Fords and Plymouths which are maintained under lean operating conditions. Such irradiation chamber measurements are related to exhaust not hydrocarbon reactivities. Hydrocarbon reactivities can be obtained by direct measurement of reactive and nonreactive hydrocarbons in the automotive emissions.     

Photochemical Reactivities of N-Butane and Other Paraffinic Hydrocarbons

Photooxidation of lower-reactivity paraffinic hydrocarbons with nitrogen oxide was investigated. Maximum oxidant yield occurred at much lower ratios of hydrocarbon to nitrogen oxide than in more reactive systems such as propylene-nitrogen oxide mixtures. Appreciable oxidant yields were obtained even from irradiation of propane-nitrogen oxide mixtures at low ratios of nitrogen oxide to propane. These results, and nitrogen dioxide and oxidant dosages computed from these measurements, substantiate the importance of reactivity characteristics in formulation of decisions on control of hydrocarbons and nitrogen oxides.     

Note On The Use of Law Students as an Air Management Resource

Abstract

In this research, pilot-scale trickle bed biofilter systems have been analyzed to determine their effectiveness in controlling toluene in waste gas streams. These studies evaluated two synthetic microbial attachment media—a monolithic channelized medium and a pelletized ceramic medium. Operational parameters considered included toluene loading, empty bed residence time (EBRT), temperature, and long-term operation. The channelized medium provided 99% removal efficiency for a toluene loading of 0.725 kg COD/m³-day during the initial stages. However, continuous operation resulted in reduced and erratic efficiencies, due to air channeling caused by random plugging. After biomass accumulated within the channels and was subsequently removed by hosing, performance of the channelized medium never regained the previous levels. Similarly, the pelletized medium exhibited consistently good performance until the accumulation of excess biomass in the medium interstices also caused overall performance to deteriorate.

Implementation of a suitable backwashing strategy for biomass control was achieved for the pelletized medium by using full medium fluidization. This strategy permitted long-term operation of the biofilter at a toluene loading of 2.27 kg COD/m³-day and 1 minute EBRT, with efficiencies consistently over 99% and no appreciable back-pressure development between successive periods of backwashing.     

Design and Operating Parameters for a Large Ambient Aerosol Chamber

Recent investigations of ambient aerosol behavior over urban areas have pointed out the need for controlled experimental data to link together field investigation results and computer simulation studies. This paper describes the design considerations, construction details and operating parameters of a large (8000 ft³) outside reaction chamber constructed in rural North Carolina. The chamber is triangular in cross-section, 20 ft wide, 20 ft high and 40 ft long, and is covered with clear 5 ml Teflon film. The outdoor location of the chamber permits the reaction volume to be exposed to the natural conditions of temperature and solar radiation. A recirculating air system allows the air in the chamber to be passed through an “absolute” fiberglas filter for adjustment of condensation nuclei concentration and also through driers for humidity adjustment. Internal fans are provided for mixing of the chamber contents without use of the recirculating system so that various degrees of turbulence can be approximated. A sampling line from the chamber passes directly to an instrument room, located directly under the chamber, where direct analyses for particle composition, concentration, and size, and gas composition and concentration are carried out. Parameters which can be varied in this system include number, size, distribution, and chemical composition of pre-existing nuclei, as well as humidity, solar radiation, temperature, and trace gas concentration and composition.     

Interlaborafory Comparison of Formaldehyde Emissions from Particleboard Underlayment in Small-Scale Environmental Chambers

Formaldehyde (CH₂O) emissions from particleboard underlayment have been measured in 0.17 and 0.2 m³ chambers at separate laboratories to test the comparability of small scale environmental chamber measurements under different ventilation and product loading conditions. Absolute CH₂O calibration was established through intermethod comparison of different monitoring techniques against a CH₂O generation apparatus. Interlaboratory precision was enhanced via co-calibration of each laboratory’s CH₂O colorimetric analyzer against the same blank and bi-level generation source at the beginning and end of the study. The results show excellent intermethod and interlaboratory agreement in both the CH₂O calibration and particleboard emissions testing. The CH₂O emission rates of the test specimens demonstrate a Fick’s Law dependence on CH₂O vapor concentration. Measured CH₂O concentrations are described by a single-compartment, single emitter model, and are inversely proportional to the ratio [N/L (m/h)] of the air exchange rate [N(h^-1)] and product loading [L(m^-1)]. Comparison tests at varying N and L, but uniform N/L were performed; similar CH2O concentrations were measured for N and L levels selected from an indoor compartment model, and for fivefold larger N and L values, which are more convenient for small-scale chamber testing.     

Estimating Separately Personal Exposure to Ambient and Nonambient Particulate Matter for Epidemiology and Risk Assessment: Why and How

ABSTRACT

This paper discusses the legal and scientific reasons for separating personal exposure to PM into ambient and nonambient components. It then demonstrates by several examples how well-established models and data typically obtained in exposure field studies can be used to estimate both individual and community average exposure to ambient-generated PM (ambient PM outdoors plus ambient PM that has infiltrated indoors), indoor-generated PM, and personal activity PM. Ambient concentrations are not highly correlated with personal exposure to nonambient PM or total PM but are highly correlated with personal exposure to ambient-generated PM. Therefore, ambient concentrations may be used in epidemiology as an appropriate surrogate for personal exposure to ambient-generated PM. Suggestions are offered as to how exposure to ambient-generated PM may be obtained and used in epidemiology and risk assessment.     

Ecological risk assessment of organic waste amendments using the species sensitivity distribution from a soil organisms test battery

Safe amendment rates (the predicted no-effect concentration or PNEC) of seven organic wastes were estimated from the species sensitivity distribution of a battery of soil biota tests and compared with different realistic amendment scenarios (different predicted environmental concentrations or PEC). None of the wastes was expected to exert noxious effects on soil biota if applied according either to the usual maximum amendment rates in Europe or phosphorus demands of crops (below 2 tonnes DM ha⁻¹). However, some of the wastes might be problematic if applied according to nitrogen demands of crops (above 2 tonnes DM ha⁻¹). Ammonium content and organic matter stability of the studied wastes are the most influential determinants of the maximum amendment rates derived in this study, but not pollutant burden. This finding indicates the need to stabilize wastes prior to their reuse in soils in order to avoid short-term impacts on soil communities.     

Persistent organic pollutants (POPs) in Caspian seals of unusual mortality event during 2000 and 2001

Persistent organic pollutants including organochlorine pesticides, PCBs, and PCDDs/DFs were determined in the blubber of Caspian seals, which died during an outbreak of canine distemper virus in 2000 and 2001. DDTs were the predominant contaminants that ranged from 3.1 to 560 microg/g lipid. A negative correlation was observed between concentration of contaminants and blubber thickness. During spring, as the blubber layer becomes thin after breeding and moulting, seals may face higher risk due to the increased concentration of organochlorines in their bodies. TEQs in the blubber of Caspian seals (10-340 pg TEQ/g) were lower than those in seals from other locations, suggesting that toxic effects of these contaminants are a deal less in the present population and they are unlikely to be linked to mass mortality. The levels of PCBs and pesticides in Caspian seals, however, comparable to those in other aquatic mammals that have suffered from epizootics, might pose a risk of immunosuppression.     

Determination of brevetoxin in recent marine sediments

Harmful algal blooms (HAB) of Karenia brevis (K. brevis) produce a suite of lipid soluble polyether brevetoxins, known to cause environmental, health and economic ill effects. There is evidence that K. brevis has increased in abundance over the past 50 years, but the dataset is incomplete. The objective of this paper was to analyze sediment from an area where K. brevis blooms have occurred and investigate if these compounds are incorporated into the underlying sediment, thus potentially allowing the use of brevetoxins as an indicator of past K. Brevis blooms. The results from LC-ESI-MS-MS analyses of brevetoxin analogs detected in surficial sediments from three sites (Fort Meyers Beach [FMB], Big Hickory Pass [BHP] and Big Carlos Pass [BCP]) along the Southwest Florida coastline with prior HAB history are promising. The analogs detected from BHP sediments were PbTx-2 and PbTx-3 with values of 0.81 and 3.1 ng g(-1) dry sediment, respectively. The detected PbTx-2 from BCP was 3.6 ng g(-1) dry sediment, while the detected PbTx-3 from BCP was 9.7 ng g(-1) dry sediment. PbTx-3 was only detected at the FMB site (2.7 ng g(-1) dry sediment). The detection of brevetoxins in recent sediments where K. brevis have occurred indicates brevetoxin incorporation into marine sediments.