Forest-edge effects on sea-salt aerosol deposition : a wind-tunnel study using living oak leaves

Landscape patchiness creates aerodynamic transition zones that affect the exchange of nutrients and pollutants between the atmosphere and vegetation. Using an artificially-generated NaCl aerosol (mass-versus-particle-size distribution with aerodynamic mean particle diameter 1.6 mu m; geometric standard deviation 1.9), we investigated the forest-edge effect on aerosol deposition within a model oak (Quercus robur) canopy in a wind tunnel with an emulated beach-to-forest transition. The deposition rate around the forest edge was 2-3 times higher than to the beach and 50%-60% higher than to the interior of the forest. The deposition velocity at the edge was 0.06 cm s(-1), which is 2-3 times higher than the beach-deposition velocity. Our results can help improve estimates of aerosol-borne inputs of nutrients or pollutants to forested landscapes that experience shifts in meteorological regimes due to changes in climate and forestry practices, in particular with respect to deciduous species in coastal environments

Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM

We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas-phase Master Chemical Mechanism version 3.2 (MCMv3.2), an aerosol dynamics and particle-phase chemistry module (which considers acid-catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion-limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study (1) the evaporation of liquid dioctyl phthalate (DOP) particles, (2) the slow and almost particle-size-independent evaporation of alpha-pinene ozonolysis secondary organic aerosol (SOA) particles, (3) the mass-transfer-limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), and (4) the influence of chamber wall effects on the observed SOA formation in smog chambers. ADCHAM is able to capture the observed alpha-pinene SOA mass increase in the presence of NH3(g). Organic salts of ammonium and carboxylic acids predominantly form during the early stage of SOA formation. In the smog chamber experiments, these salts contribute substantially to the initial growth of the homogeneously nucleated particles. The model simulations of evaporating alpha-pinene SOA particles support the recent experimental findings that these particles have a semi-solid tar-like amorphous-phase state. ADCHAM is able to reproduce the main features of the observed slow evaporation rates if the concentration of low-volatility and viscous oligomerized SOA material at the particle surface increases upon evaporation. The evaporation rate is mainly governed by the reversible decomposition of oligomers back to monomers. Finally, we demonstrate that the mass-transfer-limited uptake of condensable organic compounds onto wall-deposited particles or directly onto the Teflon chamber walls of smog chambers can have a profound influence on the observed SOA formation. During the early stage of the SOA formation the wall-deposited particles and walls themselves serve as an SOA sink from the air to the walls. However, at the end of smog chamber experiments the semi-volatile SOA material may start to evaporate from the chamber walls. With these four model applications, we demonstrate that several poorly quantified processes (i.e. mass transport limitations within the particle phase, oligomerization, heterogeneous oxidation, organic salt formation, and chamber wall effects) can have a substantial influence on the SOA formation, lifetime, chemical and physical particle properties, and their evolution. In order to constrain the uncertainties related to these processes, future experiments are needed in which as many of the influential variables as possible are varied. ADCHAM can be a valuable model tool in the design and analysis of such experiments

Health care professionals meeting with individuals with Type 2 diabetes and obesity: Balancing coaching and caution

The burden of diabetes and obesity is increasing worldwide, indicating a need to find the best standard for diabetes care. The aim of this study was to generate a theory grounded in empirical data derived from a deeper understanding of health care professionals’ main concerns when they consult with individuals with diabetes and obesity and how they handle these concerns. Tape-recorded interviews were conducted with seven groups and three individual members of a diabetes team in an area of western Sweden. The grounded theory (GT) method was used to analyse the transcribed interviews. A core category, labelled Balancing coaching and caution and three categories (Coaching and supporting, Ambivalence and uncertainty, and Adjusting intentions) emerged. The core category and the three categories formed a substantive theory that explained and illuminated how health care professionals manage their main concern; their ambition to give professional individualised care; and find the right strategy for each individual with diabetes and obesity. The theory generated by this study can improve our understanding of how a lack of workable strategies limits caregivers’ abilities to reach their goals. It also helps identify the factors that contribute to the complexity of meetings between caregivers and individuals with diabetes