Fog Chemistry at an Urban Midwestern Site

This work investigates the oxidative aging of preformed secondary organic aerosol (SOA) derived from α-pinene ozonolysis (～100 ppb_v hydrocarbon [HC_x] with excess of O₃) within the University of California–Riverside Center for Environmental Research and Technology environmental chamber that occurs after introduction of additional hydroxyl (OH) and nitrate (NO₃) radicals. Simultaneous measurements of SOA volume concentration, hygroscopicity, particle density, and elemental chemical composition (C:O:H) reveal increased particle wall-loss-corrected SOA formation (1.5%, 7.5%, and 15.1%), increase in oxygen-to-carbon ratio (O/C; 15.6%, 8.7%, and 8.7%), and hydrophilicity (4.2%, 7.4%, and 1.4%) after addition of NO (ultraviolet [UV] on), H₂O₂ (UV on), and N₂O₅ (dark), respectively. The processing observed as an increase in O/C and hydrophilicity is attributed to OH and NO₃ reactions with first-generation vapor products and UV photolysis. The rate of increase in O/C appears to be only sufficient to achieve semivolatile oxygenated organic aerosol (SV-OOA) on a day time scale even at the raised chamber radical concentrations. The additional processing with UV irradiation without addition of NO, H₂O₂, or N₂O₅ is observed, adding 5.5% wall-loss-corrected volume. The photolysis-only processing is attributed to additional OH generated from photolysis of the nitrous acid (HONO) offgasing from chamber walls. This finding indicates that OH and NO₃ radicals can further alter the chemical composition of SOA from α-pinene ozonolysis, which is proved to consist of first-generation products.

Implications: Secondary organic aerosol (SOA) may undergo aging processes once formed in the atmosphere, thereby altering the physicochemical and toxic properties of aerosol. This study discusses SOA aging of a major biogenic volatile organic compound (VOC; α-pinene) after it initially forms SOA. Aging of the α-pinene ozonolysis system by OH (through NO or H₂O₂ injection), NO₃ (through N₂O₅ injection), and photolysis is observed. Although the reaction rate appears to be only sufficient to achieve semivolatile oxygenated organic aerosol (SV-OOA) level of oxygenation on a 1-day scale, it is important that SOA aging be considered in ambient air quality models. Aging in this study is attributed to further oxidation of gas-phase oxidation products of α-pinene ozonolysis.

Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air &; Waste Management Association for information on the referenced α-pinene ozonolysis reaction and chamber reactor temperature.     

Development of a database for chemical mechanism assignments for volatile organic emissions

The development of a database for making model species assignments when preparing total organic gas (TOG) emissions input for atmospheric models is described. This database currently has assignments of model species for 12 different gas-phase chemical mechanisms for over 1700 chemical compounds and covers over 3000 chemical categories used in five different anthropogenic TOG profile databases or output by two different biogenic emissions models. This involved developing a unified chemical classification system, assigning compounds to mixtures, assigning model species for the mechanisms to the compounds, and making assignments for unknown, unassigned, and nonvolatile mass. The comprehensiveness of the assignments, the contributions of various types of speciation categories to current profile and total emissions data, inconsistencies with existing undocumented model species assignments, and remaining speciation issues and areas of needed work are also discussed. The use of the system to prepare input for SMOKE, the Speciation Tool, and for biogenic models is described in the supplementary materials. The database, associated programs and files, and a users manual are available online at http://www.cert.ucr.edu/~carter/emitdb.

Implications: Assigning air quality model species to the hundreds of emitted chemicals is a necessary link between emissions data and modeling effects of emissions on air quality. This is not easy and makes it difficult to implement new and more chemically detailed mechanisms in models. If done incorrectly, it is similar to errors in emissions speciation or the chemical mechanism used. Nevertheless, making such assignments is often an afterthought in chemical mechanism development and emissions processing, and existing assignments are usually undocumented and have errors and inconsistencies. This work is designed to address some of these problems.     

Effects of Wind Direction on Coarse and Fine Particulate Matter Concentrations in Southeast Kansas

Abstract

Field data for coarse particulate matter ([PM] PM₁₀) and fine particulate matter (PM_2.5) were collected at selected sites in Southeast Kansas from March 1999 to October 2000, using portable MiniVol particulate samplers. The purpose was to assess the influence on air quality of four industrial facilities that burn hazardous waste in the area located in the communities of Chanute, Independence, Fredonia, and Coffeyville. Both spatial and temporal variation were observed in the data. Variation because of sampling site was found to be statistically significant for PM₁₀ but not for PM_2.5. PM₁₀ concentrations were typically slightly higher at sites located within the four study communities than at background sites. Sampling sites were located north and south of the four targeted sources to provide upwind and downwind monitoring pairs. No statistically significant differences were found between upwind and downwind samples for either PM₁₀ or PM_2.5, indicating that the targeted sources did not contribute significantly to PM concentrations. Wind direction can frequently contribute to temporal variation in air pollutant concentrations and was investigated in this study. Sampling days were divided into four classifications: predominantly south winds, predominantly north winds, calm/variable winds, and winds from other directions. The effect of wind direction was found to be statistically significant for both PM₁₀ and PM_2.5. For both size ranges, PM concentrations were typically highest on days with predominantly south winds; days with calm/variable winds generally produced higher concentrations than did those with predominantly north winds or those with winds from “other” directions. The significant effect of wind direction suggests that regional sources may exert a large influence on PM concentrations in the area.     

The potential effect of differential ambient and deployment chamber temperatures on PRC derived sampling rates with polyurethane foam (PUF) passive air samplers

Performance reference compound (PRC) derived sampling rates were determined for polyurethane foam (PUF) passive air samplers in both sub-tropical and temperate locations across Australia. These estimates were on average a factor of 2.7 times higher in summer than winter. The known effects of wind speed and temperature on mass transfer coefficients could not account for this observation. Sampling rates are often derived using ambient temperatures, not the actual temperatures within deployment chambers. If deployment chamber temperatures are in fact higher than ambient temperatures, estimated sampler-air partition coefficients would be greater than actual partition coefficients resulting in an overestimation of PRC derived sampling rates. Sampling rates determined under measured ambient temperatures and estimated deployment chamber temperatures in summer ranged from 7.1 to 10 m³ day⁻¹ and 2.2-6.8 m³ day⁻¹ respectively. These results suggest that potential differences between ambient and deployment chamber temperatures should be considered when deriving PRC-based sampling rates.     

High richness and dense seeding enhance grassland restoration establishment but have little effect on drought response

Restorations commonly utilize seed addition to formerly arable lands where the development of native plant communities is severely dispersal limited. However, variation in seed addition practices may profoundly affect restoration outcomes. Theory and observations predict that species-rich seed mixtures and seeding at high densities should enhance native plant community establishment, minimize exotic species cover, and may promote resistance and resilience to, and recovery from, environmental perturbations. We studied the post-seeding establishment of native plant communities in large grassland restoration plots, which were sown at two densities crossed with two levels of species richness on formerly arable land in Nebraska, USA, and their responses to drought. To evaluate drought resistance, recovery, and resilience of restored plant communities, we erected rainfall manipulation structures and tracked the response of seeded species cover and total plant biomass during experimental drought relative to controls and in the post-drought growing season. High seed richness and high-density seeding treatments resulted in greater richness and cover of native, seeded species per 0.5 m2 compared to low-richness and low-density treatments. Cover differences in response to seed mixture richness were driven by native forbs. Richness and cover of exotic species were lowest in high-richness and high-density treatments. We found little evidence of differential drought resistance, recovery, and resilience among seeding treatments. Increases in exotic species across years were restricted to drought subplots, and were not affected by seeding treatments. Grassland restoration was generally enhanced and exotic cover reduced both by the use of high-richness seed mixtures and high-density seeding. Given the lack of restoration treatment effects on the resistance, recovery, or resilience of seeded species exposed to drought, and the increases in exotic species following drought, other forms of active management may be needed to produce restored plant communities that are robust to climate change.     

Measuring and modeling the seasonal changes of an urban Green Treefrog (Hyla cinerea) population

Green Treefrogs (Hyla cinerea) were captured, marked, measured and released at an urban study site in Lafayette, LA, during the 2004 and 2005 breeding seasons. A statistical method based on a generalization of the hypergeometric distribution was used to derive weekly time-series estimates of the population sizes. To describe the population dynamics, a stage structured mathematical model was developed and compared to time-series obtained from the weekly population estimates study using a least-squares approach. Two fitting experiments were done: (1) Using uniform distribution for the birth rate during the breeding season; (2) Using a birth rate distributed according to weekly data on frog calling intensity. Although both model-to-data fits look very promising during the years 2004 and 2005 and result in similar inherent survivorship rates for the tadpoles, juvenile and adult frogs, the fit that uses the calling data predicts a lower number of tadpoles and frogs in the long term than the one that uses uniform birth distribution. The parameter estimates resulting from these fitting experiments are used in the context of stochastic simulations to derive extinction and persistence probabilities for this population. Due to the oscillatory dynamics (with high amplitude) evidenced by the capture-recapture data and corroborated by the model, it is suggested that anuran monitoring efforts should take into account the natural intra-annual variation in population size.     

Morphological and fluorescence analysis of the Montastraea annularis species complex in Florida

The taxonomic status of the Montastraea annularis species complex is unclear. Much evidence has been accumulated to support the separation into 3 species, but the presence of intermediate morphotypes and the apparent lack of effective reproductive barriers in some areas are yet unexplained. Several authors have made a call for the introduction of new traits that can be used to resolve differences among closely related coral species. We collected skeletal and tissue samples from corals within the M. annularis species complex (15 each of M. annularis, M. faveolata, and M. franksi) and 10 morphological intermediates from several reefs in the Florida Keys. Multivariate analysis of corallite skeletal measurements supported the separation of the species complex into three taxa. We detected two main fluorescence emission peaks at 480 nm (turquoise) and 515 nm (green) that were not distributed equally among the three species. Every M. annularis colony had a major turquoise fluorescence peak. Some had a weak green secondary fluorescence peak. Colonies of M. faveolata and M. franksi had either the green or turquoise fluorescence peak, but at significantly different frequencies. The intermediate morphotypes proved to be highly heterogeneous with respect to both micromorphology and fluorescence, and their nature could not be fully explained. We were not able to separate the three species using fluorescence characters alone, however this new trait does increase our understanding of the taxonomic structure within the M. annularis species complex. Received: 21 January 2000 / Accepted: 1 September 2000     

Exploring discourses on international environmental regime effectiveness with Q methodology: a case study of the Mediterranean Action Plan

Extensive research has been done on the 'high politics' of negotiations of international environmental agreements. However, little attention has been paid to the effectiveness of their implementation after coming into force. Effectiveness cannot be easily measured, since different stakeholders use different criteria as the basis of their opinion. The purpose of this study is to investigate discourses on the effectiveness of an international environmental regime. The regime chosen is the Mediterranean Action Plan (MAP) - and its legal framework, the Barcelona Convention - which was established in 1975 under the aegis of the United Nations Environment Programme (UNEP). Q methodology was used to reveal discourses on the effectiveness of UNEP/MAP. After collecting relevant literature and identifying the stakeholders, 25 in-depth interviews were conducted. The stakeholders were from the Secretariat of the Convention, academia, NGO workers, and others that studied or knew the subject well. From these interviews 294 statements were extracted, from which 44 were finally selected to be used in the Q study. The interviewees were approached for the second time to complete the Q sorts. This study revealed four distinct discourses concerning the effectiveness of international environmental regimes. It concludes that there is no one 'right' way of defining effectiveness and that no approach can provide more than a partial evaluation of the overall effectiveness of a regime.     

Changes in the leachability of metals from dredged canal sediments during drying and oxidation

The behaviour of metals in canal sediments after their disposal to land has important implications for the environmental management of canal dredgings. The leaching behaviour of trace metals was investigated in a laboratory-based experiment using sediment from a canal in the UK (139 mg Zn kg-1dry sediment, 1.1 mg Cd, kg-1dry sediment 31.5 mg Cr kg-1dry sediment, 20.6 mg Cu kg-1dry sediment 48.4 mg Ni kg-1dry sediment, 43.4 mg Pb kg-1dry sediment and 7.6 mg As kg-1dry sediment). The sediment was allowed to dry. Cores (10 cm long) of the drying canal sediment were taken over a period of 12 weeks. A simple water extraction procedure was used to investigate changes in metal leachability at varying depths through the cores. Metal leachability increased over the first five weeks of drying and then subsequently decreased between weeks five and twelve, (e.g. Cd increased from approximately 0.006 to 0.018 mg/kgsediment then decreased to approximately 0.006 mg/kgsediment, Zn increased from approximately 1.5 to 3 mg/kgsediment and then decreased to approximately 1.5 mg/kgsediment). These results were combined with sulphide/sulphate ratios, which showed a decrease as the sediment dried (e.g. at 2-4 cm depth from approximately 1 to 0.49), and BCR sequential extraction data. Most metals (except Cd and As) showed a redistribution from the residual phase into more mobile phases as the sediment dried and oxidised. Metal leachability was strongly correlated with the sulphide/sulphate ratio with leachability normally increasing with decreasing sulphide/sulphate ratio. The combined results were used to infer the likely behaviour of dredged material upon disposal to land.     

Environmental risks of farmed and barren alkaline coal ash landfills in Tuzla, Bosnia and Herzegovina

The disposal of coal combustion residues (CCR) has led to a significant consumption of land in the West Balkan region. In Tuzla (Bosnia and Herzegovina) we studied previously soil-covered (farmed) and barren CCR landfills including management practises, field ageing of CCR and the transfer of trace elements into crops, wild plants and wastewaters. Soil tillage resulted in mixing of cover soil with CCR. Medicago sativa showed very low Cu:Mo ratios (1.25) which may cause hypocuprosis in ruminants. Total loads of inorganic pollutants in the CCR transport water, but not pH ( approximately 12), were below regulatory limits of most EU countries. Arsenic concentrations in CCR transport water were <2microgl(-1) whereas reductive conditions in an abandoned landfill significantly enhanced concentrations in leachates (44microgl(-1)). The opposite pattern was found for Cr likely due to large initial leaching of CrVI. Public use of landfills, including farming, should be based on a prior risk assessment due to the heterogeneity of CCR.