Temperature dependence of secondary organic aerosol

Temperature was found to have a dramatic effect on secondary organic aerosol formation from two ozonolysis systems, cyclohexene and α-pinene. Isothermal experiments were conducted for both systems where the lowest temperature, 278 K, formed approximately 2.5–3 times and 5–6 times the SOA formed at 300 K and 318 K, respectively. Changing the cyclohexene system temperature to a different isothermal experimental set point after completion of SOA formation did not lead to sufficient condensation/evaporation to reproduce the SOA formation at other temperature set points. When the system temperature was cycled between two set points at the end of an experiment, the α-pinene system showed reversibility between the initial temperature 318 K and 300 K. For temperature cycles between the initial temperature of 300 K–318 K, an irreversible loss of mass is observed after the first heating cycle with reversibility observed between subsequent temperature cycles. The SOA formed at 278 K was reversible over a 22 K range but was unable to evaporate sufficiently to match the SOA mass formed at 300 K. Hygroscopicity measurements, taken after the completion of SOA formation, indicate that hygroscopicity of the aerosol is also a function of temperature and that the aerosol does not continue to be oxidized after initial growth is complete. The differing hygroscopicity of the semi-volatile component of the aerosol is evident during system temperature changes after completion of the experiment.     

Genomic erosion in a demographically recovered bird species during conservation rescue

The pink pigeon (Nesoenas mayeri) is an endemic species of Mauritius that has made a remarkable recovery after a severe population bottleneck in the 1970s to early 1990s. Prior to this bottleneck, an ex situ population was established from which captive-bred individuals were released into free-living subpopulations to increase population size and genetic variation. This conservation rescue led to rapid population recovery to 400–480 individuals, and the species was twice downlisted on the International Union for the Conservation of Nature (IUCN) Red List. We analyzed the impacts of the bottleneck and genetic rescue on neutral genetic variation during and after population recovery (1993–2008) with restriction site-associated sequencing, microsatellite analyses, and quantitative genetic analysis of studbook data of 1112 birds from zoos in Europe and the United States. We used computer simulations to study the predicted changes in genetic variation and population viability from the past into the future. Genetic variation declined rapidly, despite the population rebound, and the effective population size was approximately an order of magnitude smaller than census size. The species carried a high genetic load of circa 15 lethal equivalents for longevity. Our computer simulations predicted continued inbreeding will likely result in increased expression of deleterious mutations (i.e., a high realized load) and severe inbreeding depression. Without continued conservation actions, it is likely that the pink pigeon will go extinct in the wild within 100 years. Conservation rescue of the pink pigeon has been instrumental in the recovery of the free-living population. However, further genetic rescue with captive-bred birds from zoos is required to recover lost variation, reduce expression of harmful deleterious variation, and prevent extinction. The use of genomics and modeling data can inform IUCN assessments of the viability and extinction risk of species, and it helps in assessments of the conservation dependency of populations.     

Compositional data analysis of smoke emissions from debris piles with low-density polyethylene

ABSTRACT

Data describing the composition of smoke are inherently multivariate and always non-negative parts of a whole. The data are relative and the information is contained in the ratios between parts of the composition. A prior analysis of smoke emissions produced from the burning of manzanita wood mixed with low-density polyethylene plastic applied traditional statistical methods to the compositional data and found no effect. The current paper applies compositional data techniques to these smoke emissions to determine if the prior analysis was accurate. Analysis of variance of the isometric log-ratios showed that LDPE significantly affected the CO₂ emission ratio for 8 of the 191 trace gases; this analysis showed none of the gases identified in the previous analysis were affected by LDPE. LDPE did not affect the CO₂ emission ratios for the alkanes, alkenes, alkynes, aldehydes, cycloalkanes, cycloalkenes, diolefins, ketones, MAHs, and PAHs. Compositional data analysis should be used to analyze smoke emissions data. Burning contaminant-free LDPE should produce emissions like wood.     

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m³ FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NO_x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NO_x and simplified ambient surrogate–NO_x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO_x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO_x levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.     

Effect of low-density polyethylene on smoke emissions from burning of simulated debris piles

Low-density polyethylene (LDPE) plastic is used to keep piled debris from silvicultural activities—activities associated with development and care of forests—dry to enable efficient disposal by burning. The effects of inclusion of LDPE in this manner on smoke emissions are not well known. In a combustion laboratory experiment, 2-kg mixtures of LDPE and manzanita (Arctostaphylos sp.) wood containing 0, 0.25, and 2.5% LDPE by mass were burned. Gaseous and particulate emissions were sampled in real time during the entire flaming, mixed combustion phase—when the flaming and smoldering phases are present at the same time—and during a portion of the smoldering phase. Analysis of variance was used to test significance of modified combustion efficiency (MCE)—the ratio of concentrations of fire-integrated excess CO₂ to CO₂ plus CO—and LDPE content on measured individual compounds. MCE ranged between 0.983 and 0.993, indicating that combustion was primarily flaming; MCE was seldom significant as a covariate. Of the 195 compounds identified in the smoke emissions, only the emission factor (EF) of 3M-octane showed an increase with increasing LDPE content. Inclusion of LDPE had an effect on EFs of pyrene and fluoranthene, but no statistical evidence of a linear trend was found. Particulate emission factors showed a marginally significant linear relationship with MCE (0.05 < P-value < 0.10). Based on the results of the current and previous studies and literature reviews, the inclusion of small mass proportions of LDPE in piled silvicultural debris does not appear to change the emissions produced when low-moisture-content wood is burned. In general, combustion of wet piles results in lower MCEs and consequently higher levels of emissions.

Implications:Current air quality regulations permit the use of burning to dispose of silvicultural piles; however, inclusion of low-density polyethyelene (LDPE) plastic in silvicultural piles can result in a designation of the pile as waste. Waste burning is not permitted in many areas, and there is also concern that inclusion of LDPE leads to toxic air emissions.     

Ambient measurements of 2,2,4-trimethyl, 1,3-pentanediol monoisobutyrate in Southern California

2,2,4-trimethyl, 1,3-pentanediol monoisobutyrate (TPM) is a widely used solvent found in water-based coatings. Ambient measurements of TPM are reported here for the first time. Although this compound has been previously measured in indoor air, this study illustrates successful detection and quantification of TPM in ambient air at three locations in Southern California: Pico Rivera, Azusa, and Riverside. TPM was detected in every sample collected, with concentrations ranging from 0.7 to 49.5 parts per trillion (ppt). Collections took place during summer 2009, fall 2009, winter 2009/2010, and spring 2010, for 5–7 days during each season. The highest mean concentrations were observed during the summer months for each city, when coating activities are typically at their highest.

Implications 2,2,4-Trimethyl, 1,3-pentanediol monoisobutyrate (TPM) is a widely used solvent found in water-based coatings. Ambient measurements of TPM are reported here for the first time. The highest mean concentrations were observed during the summer months for each city, when coating activities are typically at their highest. Unreacted TPM constitutes approximately 0.01% of the total nonmethane hydrocarbon (NMHC) concentrations in the Los Angeles air basin and given its slow reactivity rate in forming ozone, this would be an approximate upper limit for the fraction of ozone that it is responsible for forming.     

Generation and characterization of diesel exhaust in a facility for controlled human exposures

An idling medium-duty diesel truck operated on ultralow sulfur diesel fuel was used as an emission source to generate diesel exhaust for controlled human exposure. Repeat tests were conducted on the Federal Test Procedure using a chassis dynamometer to demonstrate the reproducibility of this vehicle as a source of diesel emissions. Exhaust was supplied to a specially constructed exposure chamber at a target concentration of 100 microg x m(-3) diesel particulate matter (DPM). Spatial variability within the chamber was negligible, whereas emission concentrations were stable, reproducible, and similar to concentrations observed on the dynamometer. Measurements of nitric oxide, nitrogen dioxide, carbon monoxide, particulate matter (PM), elemental and organic carbon, carbonyls, trace elements, and polycyclic aromatic hydrocarbons were made during exposures of both healthy and asthmatic volunteers to DPM and control conditions. The effect of the so-called "personal cloud" on total PM mass concentrations was also observed and accounted for. Conventional lung function tests in 11 volunteer subjects (7 stable asthmatic) did not demonstrate a significant change after 2-hr exposures to diesel exhaust. In summary, we demonstrated that this facility can be effectively and safely used to evaluate acute responses to diesel exhaust exposure in human volunteers.     

Book reviews

ANALYTICAL PLANNING: THE ORGANISATION OF SYSTEMS

Thomas L. Saaty and Kevin P. Kearns

Pergamon Press, 1985. Price: U.S. $40.00, U.K. £29.50.

THE GEOGRAPHER AT WORK

Peter Gould

Routledge and Kegan Paul, London 1985’ Price: £8.95.

UTOPIA ON TRIAL

Alice Colman

Hilary Shipman Ltd., 19 Framfield Road, Highbury, London. May 1985 (reprinted August, 1985). Price: £7.95.

SIR RAYMOND UNWIN: ARCHITECT, PLANNER AND VISIONARY

Frank Jackson

A. Zwemmer Ltd., London 1985. 187 pp. with maps and illustrations.

STRATEGIC PLANNING IN ACTION: THE IMPACT OF THE CLYDE VALLEY REGIONAL PLAN 1946–1982

R. Smith and U. Wannop (eds)

Gower, 1985, 272 pp. Price: £16.50.

LOCALITIES, CLASS AND GENDER

The Lancaster Regionalism Group (Linda Murgatroyd, Mike Savage, Dan Shapiro, John Urry, Sylvia Walby, Alan Warde, with Jane Mark‐Lawson)

Pion Ltd., 1985. Price: £12.00.