Vapor−Wall Deposition in Chambers: Theoretical Considerations

In order to constrain the effects of vapor–wall deposition on measured secondary organic aerosol (SOA) yields in laboratory chambers, researchers recently varied the seed aerosol surface area in toluene oxidation and observed a clear increase in the SOA yield with increasing seed surface area (Zhang, X.; et al. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 5802). Using a coupled vapor–particle dynamics model, we examine the extent to which this increase is the result of vapor–wall deposition versus kinetic limitations arising from imperfect accommodation of organic species into the particle phase. We show that a seed surface area dependence of the SOA yield is present only when condensation of vapors onto particles is kinetically limited. The existence of kinetic limitation can be predicted by comparing the characteristic time scales of gas-phase reaction, vapor–wall deposition, and gas–particle equilibration. The gas–particle equilibration time scale depends on the gas–particle accommodation coefficient α_p. Regardless of the extent of kinetic limitation, vapor–wall deposition depresses the SOA yield from that in its absence since vapor molecules that might otherwise condense on particles deposit on the walls. To accurately extrapolate chamber-derived yields to atmospheric conditions, both vapor–wall deposition and kinetic limitations must be taken into account

Understanding atmospheric organic aerosols via factor analysis of aerosol mass spectrometry: a review

Organic species are an important but poorly characterized constituent of airborne particulate matter. A quantitative understanding of the organic fraction of particles (organic aerosol, OA) is necessary to reduce some of the largest uncertainties that confound the assessment of the radiative forcing of climate and air quality management policies. In recent years, aerosol mass spectrometry has been increasingly relied upon for highly time-resolved characterization of OA chemistry and for elucidation of aerosol sources and lifecycle processes. Aerodyne aerosol mass spectrometers (AMS) are particularly widely used, because of their ability to quantitatively characterize the size-resolved composition of submicron particles (PM1). AMS report the bulk composition and temporal variations of OA in the form of ensemble mass spectra (MS) acquired over short time intervals. Because each MS represents the linear superposition of the spectra of individual components weighed by their concentrations, multivariate factor analysis of the MS matrix has proved effective at retrieving OA factors that offer a quantitative and simplified description of the thousands of individual organic species. The sum of the factors accounts for nearly 100% of the OA mass and each individual factor typically corresponds to a large group of OA constituents with similar chemical composition and temporal behavior that are characteristic of different sources and/or atmospheric processes. The application of this technique in aerosol mass spectrometry has grown rapidly in the last six years. Here we review multivariate factor analysis techniques applied to AMS and other aerosol mass spectrometers, and summarize key findings from field observations. Results that provide valuable information about aerosol sources and, in particular, secondary OA evolution on regional and global scales are highlighted. Advanced methods, for example a-priori constraints on factor mass spectra and the application of factor analysis to combined aerosol and gas phase data are discussed. Integrated analysis of worldwide OA factors is used to present a holistic regional and global description of OA. Finally, different ways in which OA factors can constrain global and regional models are discussed

One-Off Subsidies and Long-Run Adoption Experimental Evidence on Improved Cooking Stoves in Senegal

Free technology distribution can be an effective development policy instrument if adoption is socially inefficient and hampered by affordability constraints. Yet, policy makers often oppose free distribution, arguing that reference dependence spoils the willingness to pay and thus market potentials in the long run. For improved cookstoves, this paper studies the willingness to pay six years after a randomized one-time free distribution. Using a real-purchase offer procedure, we find that households who received a free stove in the past do not reveal a lower willingness to pay to repurchase the stove. Furthermore, we provide exploratory evidence that learning and reference-dependence effects do not spill over from the treatment to the control group. The policy implication is that one-time free distribution does not disturb future market establishment and might even facilitate it.JEL Codes: D03, D12, O12, O13, Q4

Asia’s Wicked Environmental Problems

The developing economies of Asia are confronted by serious environmental problems that threaten to undermine future growth, food security, and regional stability. This study considers four major environmental challenges that policymakers across developing Asia will need to address towards 2030: water management, air pollution, deforestation and land degradation, and climate change. We argue that these challenges, each unique in their own way, all exhibit the characteristics of "wicked problem". As developed in the planning literature, and now applied much more broadly, wicked problems are dynamic, complex, encompass many issues and stakeholders, and evade straightforward, lasting solutions. Detailed case studies are presented to illustrate the complexity and significance of Asia's environmental challenges, and also their nature as wicked problems. The most important implication of this finding is that there will be no easy or universal solutions to environmental problems across Asia. This is a caution against over-optimism and blueprint or formulaic solutions. It is not, however, a counsel for despair. We suggest seven general principles which may be useful across the board. These are: a focus on co-benefits; an emphasis on stakeholder participation; a commitment to scientific research; an emphasis on long-term planning; pricing reform; tackling corruption, in addition to generally bolstering institutional capacity with regard to environmental regulation; and a strengthening of regional approaches and international support

Aligning evidence generation and use across health, development, and environment

© 2019 The Authors Although health, development, and environment challenges are interconnected, evidence remains fractured across sectors due to methodological and conceptual differences in research and practice. Aligned methods are needed to support Sustainable Development Goal advances and similar agendas. The Bridge Collaborative, an emergent research-practice collaboration, presents principles and recommendations that help harmonize methods for evidence generation and use. Recommendations were generated in the context of designing and evaluating evidence of impact for interventions related to five global challenges (stabilizing the global climate, making food production sustainable, decreasing air pollution and respiratory disease, improving sanitation and water security, and solving hunger and malnutrition) and serve as a starting point for further iteration and testing in a broader set of contexts and disciplines. We adopted six principles and emphasize three methodological recommendations: (1) creation of compatible results chains, (2) consideration of all relevant types of evidence, and (3) evaluation of strength of evidence using a unified rubric. We provide detailed suggestions for how these recommendations can be applied in practice, streamlining efforts to apply multi-objective approaches and/or synthesize evidence in multidisciplinary or transdisciplinary teams. These recommendations advance the necessary process of reconciling existing evidence standards in health, development, and environment, and initiate a common basis for integrated evidence generation and use in research, practice, and policy design