A comparative study of the main mechanisms controlling indoor air pollution in residential flats

The relative contribution of the main mechanisms that control indoor air quality in residential flats was examined. Indoor and outdoor concentration measurements of different type pollutants (black carbon, SO2, O3, NO, NO2,) were monitored in three naturally ventilated residential flats in Athens, Greece. At each apartment, experiments were conducted during the cold as well as during the warm period of the year. The controlling parameters of transport and deposition mechanisms were calculated from the experimental data. Deposition rates of the same pollutant differ according to the site (different construction characteristics) and to the measuring period for the same site (variations in relative humidity and differences in furnishing). Differences in the black carbon deposition rates were attributed to different black carbon size distributions. The highest deposition rates were observed for O3 in the residential flats with the older construction and the highest humidity levels. The calculated parameters as well as the measured outdoor concentrations were used as input data of a one-compartment indoor air quality model, and the indoor concentrations, the production, and loss rates of the different pollutants were calculated. The model calculated concentrations are in good agreement with the measured values. Model simulations revealed that the mechanism that mainly affected the change rate of indoor black carbon concentrations was the transport from the outdoor environment, while the removal due to deposition was insignificant. During model simulations, it was also established that that the change rate of SO2 concentrations was governed by the interaction between the transport and the deposition mechanisms while NOX concentrations were mainly controlled through photochemical reactions and the transport from outdoors.

Study on indoor thermal environment and air quality of office rooms controlled by personal displacement ventilation using CFD

Three-dimensional computational simulations are performed to examine indoor environment and micro-environment around human bodies in an office in terms of thermal environment and air quality. In this study, personal displacement ventilation (PDV), including two cases with all seats taken and two middle seats taken, is compared with overall displacement ventilation (ODV) of all seats taken under the condition that supply temperature is 24℃ and air change rate is 60 l/s per workstation. When using PDV, temperature stratification, the characteristic of displacement ventilation, is obviously observed at the position of occupant’s head and clearer in the case with all seats taken. Verticalertical ertical temperature temperature temperature temperature temperature differences below height of the head areare under under under 2℃ in two cases in two cases in two cases in two cases in two cases in two cases in two cases in two cases with all seats taken，and the temperature with PDV is higher than that with ODV. Verticalertical ertical temperature temperature temperature temperature temperature temperature difference is under 3 under 3under 3 under 3℃ in the case in the case in the case in the case in the case in the case in the case with two middle seats taken. CO2 concentration is lower th is lower th is lower this lower this lower than 2 g/man 2 g/m an 2 g/man 2 g/man 2 g/man 2 g/m 3 in the breath zone. in the breath zone. in the breath zone. in the breath zone. in the breath zone. in the breath zone. in the breath zone. in the breath zone. in the breath zone. The results indicate that PDV can be used in the room with big change of occupants’ number to satisfy the need of thermal comfort and air quality. When not all seats are taken, designers should increase supply air requirement or reduce its temperature for thermal comfort. INDEX TERMS

Analysis of Direct Outdoor Air Cooling Efficency for Combined Variable Air Volume Air-conditioning System in Stores in Cold Climates of China

Direct outdoor air cooling contributes a lot not only to the improvement of the indoor air quality but also to the energy saving. Its full use will reduce the water chiller’s running time especially in some stores where cooling load keeps much higher and longer than that in other buildings. A novel air-conditioning system named Combined Variable Air Volume system (CVAV), combining a normal AHU with a separate outdoor air supply system, was proposed firstly by the authors. The most attractive feature of the system is its full utilization of cooling capacity and freshness of outdoor air in the transition period of the year round. On the basis of the obtain of the dynamic cooling loads of the typical shopping malls in different four cities located in cold climates in China with the aid of DOE-2, the possibility of increasing the amount of outdoor air volume of CVAV system in the transition period instead of operating the water chillers was confirmed. Moreover, a new concept, Direct Outdoor Air Cooling Efficiency (DOACE), was defined as the ratio of cooling capacity of outdoor air to the water chiller, indicating the degree of outdoor air’s utilization. And the DOACE of the CVAV was calculated and compared with that of conventional all-air constant volume air-conditioning systems, the results showed that CVAV bear much more energy saving potential with the 10%~19% higher DOACE and it is a kind of energy efficient systems and can improve the indoor air quality as well.

Adhesion of Salmonella enterica var Enteritidis strains lacking fimbriae and flagella to rat ileal explants cultured at the air interface or submerged in tissue culture medium

Rat ileal air interface and submerged explant models were developed and used to compare the adhesion of Salmonella enterica var Enteritidis wild-type strains with that of their isogenic single and multiple deletion mutants. The modified strains studied were defective for fimbriae, flagella, motility or chemotaxis and binding was assessed on tissues with and without an intact mucus layer. A multiple afimbriate/aflagellate (fim(-)/fla(-)) strain, a fimbriate but aflagellate (fla(-)) strain and a fimbriate/flagellate but non-motile (mot(-)) strain bound significantly less extensively to the explants than the corresponding wild-type strains. With the submerged explant model this difference was evident in tissues with or without a mucus layer, whereas in the air interface model it was observed only in tissues,vith an intact mucus layer. A smooth swimming chemotaxis-defective (che(-)) strain and single or multiple afimbriate strains bound to explants as well as their corresponding wild-type strain. This suggests that under the present experimental conditions fimbriae were not essential for attachment of S. enterica var Enteritidis to rat ileal explants, However; the possession of active flagella did appear to be an important factor. in enabling salmonellae to penetrate the gastrointestinal mucus layer and attach specifically to epithelial cells.

‘In the air’ and below the horizon: migrant workers in UK construction and the practice-based nature of learning and communicating OHS

Local, tacit and normally unspoken OHS (occupational health and safety) knowledge and practices can too easily be excluded from or remain below the industry horizon of notice, meaning that they remain unaccounted for in formal OHS policy and practice. In this article we stress the need to more systematically and routinely tap into these otherwise ‘hidden’ communication channels, which are central to how everyday safe working practices are achieved. To demonstrate this approach this paper will draw on our ethnographic research with a gang of migrant curtain wall installers on a large office development project in the north of England. In doing so we reflect on the practice-based nature of learning and sharing OHS knowledge through examples of how workers’ own patterns of successful communication help avoid health and safety problems. These understandings, we argue, can be advanced as a basis for the development of improved OHS measures, and of organizational knowing and learning.

Chemistry–climate model simulations of twenty-first century stratospheric climate and circulation changes

The response of stratospheric climate and circulation to increasing amounts of greenhouse gases (GHGs) and ozone recovery in the twenty-first century is analyzed in simulations of 11 chemistry–climate models using near-identical forcings and experimental setup. In addition to an overall global cooling of the stratosphere in the simulations (0.59 6 0.07 K decade21 at 10 hPa), ozone recovery causes a warming of the Southern Hemisphere polar lower stratosphere in summer with enhanced cooling above. The rate of warming correlates with the rate of ozone recovery projected by the models and, on average, changes from 0.8 to 0.48 Kdecade21 at 100 hPa as the rate of recovery declines from the first to the second half of the century. In the winter northern polar lower stratosphere the increased radiative cooling from the growing abundance of GHGs is, in most models, balanced by adiabatic warming from stronger polar downwelling. In the Antarctic lower stratosphere the models simulate an increase in low temperature extremes required for polar stratospheric cloud (PSC) formation, but the positive trend is decreasing over the twenty-first century in all models. In the Arctic, none of the models simulates a statistically significant increase in Arctic PSCs throughout the twenty-first century. The subtropical jets accelerate in response to climate change and the ozone recovery produces awestward acceleration of the lower-stratosphericwind over theAntarctic during summer, though this response is sensitive to the rate of recovery projected by the models. There is a strengthening of the Brewer–Dobson circulation throughout the depth of the stratosphere, which reduces the mean age of air nearly everywhere at a rate of about 0.05 yr decade21 in those models with this diagnostic. On average, the annual mean tropical upwelling in the lower stratosphere (;70 hPa) increases by almost 2% decade21, with 59% of this trend forced by the parameterized orographic gravity wave drag in the models. This is a consequence of the eastward acceleration of the subtropical jets, which increases the upward flux of (parameterized) momentum reaching the lower stratosphere in these latitudes.

Inhalation exposure to particulate matter in rooms with underfloor air distribution

This work investigated the personal exposure to indoor particulate matters using the intake fraction metric and provided a possible way to trace the particle inhaled from an indoor particle source. A turbulence model validated by the particle measurements in a room with underfloor air distribution (UFAD) system was used to predict the indoor particle concentrations. Inhalation intake fraction of indoor particles was defined and evaluated in two rooms equipped with the UFAD, i.e., the experimental room and a small office. According to the exposure characteristics and a typical respiratory rate, the intake fraction was determined in two rooms with a continuous and episodic (human cough) source of particles, respectively. The findings showed that the well-mixing assumption of indoor air failed to give an accurate estimation of inhalation exposure and the average concentration at return outlet or within the overall room could not relate well the intake fraction to the amount of particle emitted from an indoor source.

Evaluation of regional climate simulations for air quality modelling purposes

In order to evaluate the future potential benefits of emission regulation on regional air quality, while taking into account the effects of climate change, off-line air quality projection simulations are driven using weather forcing taken from regional climate models. These regional models are themselves driven by simulations carried out using global climate models (GCM) and economical scenarios. Uncertainties and biases in climate models introduce an additional “climate modeling” source of uncertainty that is to be added to all other types of uncertainties in air quality modeling for policy evaluation. In this article we evaluate the changes in air quality-related weather variables induced by replacing reanalyses-forced by GCM-forced regional climate simulations. As an example we use GCM simulations carried out in the framework of the ERA-interim programme and of the CMIP5 project using the Institut Pierre-Simon Laplace climate model (IPSLcm), driving regional simulations performed in the framework of the EURO-CORDEX programme. In summer, we found compensating deficiencies acting on photochemistry: an overestimation by GCM-driven weather due to a positive bias in short-wave radiation, a negative bias in wind speed, too many stagnant episodes, and a negative temperature bias. In winter, air quality is mostly driven by dispersion, and we could not identify significant differences in either wind or planetary boundary layer height statistics between GCM-driven and reanalyses-driven regional simulations. However, precipitation appears largely overestimated in GCM-driven simulations, which could significantly affect the simulation of aerosol concentrations. The identification of these biases will help interpreting results of future air quality simulations using these data. Despite these, we conclude that the identified differences should not lead to major difficulties in using GCM-driven regional climate simulations for air quality projections.

An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection

Hourly data (1994–2009) of surface ozone concentrations at eight monitoring sites have been investigated to assess target level and long–term objective exceedances and their trends. The European Union (EU) ozone target value for human health (60 ppb–maximum daily 8–hour running mean) has been exceeded for a number of years for almost all sites but never exceeded the set limit of 25 exceedances in one year. Second highest annual hourly and 4th highest annual 8–hourly mean ozone concentrations have shown a statistically significant negative trend for in–land sites of Cork–Glashaboy, Monaghan and Lough Navar and no significant trend for the Mace Head site. Peak afternoon ozone concentrations averaged over a three year period from 2007 to 2009 have been found to be lower than corresponding values over a three–year period from 1996 to 1998 for two sites: Cork–Glashaboy and Lough Navar sites. The EU long–term objective value of AOT40 (Accumulated Ozone Exposure over a threshold of 40 ppb) for protection of vegetation (3 ppm–hour, calculated from May to July) has been exceeded, on an individual year basis, for two sites: Mace Head and Valentia. The critical level for the protection of forest (10 ppm–hour from April to September) has not been exceeded for any site except at Valentia in the year 2003. AOT40–Vegetation shows a significant negative trend for a 3–year running average at Cork–Glashaboy (–0.13±0.02 ppm–hour per year), at Lough Navar (–0.05±0.02 ppm–hour per year) and at Monaghan (–0.03±0.03 ppm–hour per year–not statistically significant) sites. No statistically significant trend was observed for the coastal site of Mace head. Overall, with the exception of the Mace Head and Monaghan sites, ozone measurement records at Irish sites show a downward negative trend in peak values that affect human health and vegetation.

A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2

A Lagrangian model of photochemistry and mixing is described (CiTTyCAT, stemming from the Cambridge Tropospheric Trajectory model of Chemistry And Transport), which is suitable for transport and chemistry studies throughout the troposphere. Over the last five years, the model has been developed in parallel at several different institutions and here those developments have been incorporated into one "community" model and documented for the first time. The key photochemical developments include a new scheme for biogenic volatile organic compounds and updated emissions schemes. The key physical development is to evolve composition following an ensemble of trajectories within neighbouring air-masses, including a simple scheme for mixing between them via an evolving "background profile", both within the boundary layer and free troposphere. The model runs along trajectories pre-calculated using winds and temperature from meteorological analyses. In addition, boundary layer height and precipitation rates, output from the analysis model, are interpolated to trajectory points and used as inputs to the mixing and wet deposition schemes. The model is most suitable in regimes when the effects of small-scale turbulent mixing are slow relative to advection by the resolved winds so that coherent air-masses form with distinct composition and strong gradients between them. Such air-masses can persist for many days while stretching, folding and thinning. Lagrangian models offer a useful framework for picking apart the processes of air-mass evolution over inter-continental distances, without being hindered by the numerical diffusion inherent to global Eulerian models. The model, including different box and trajectory modes, is described and some output for each of the modes is presented for evaluation. The model is available for download from a Subversion-controlled repository by contacting the corresponding authors.

Effect of hypobaric hypoxia, simulating conditions during long-haul air travel, on coagulation, fibrinolysis, platelet function, and endothelial activation

CONTEXT: The link between long-haul air travel and venous thromboembolism is the subject of continuing debate. It remains unclear whether the reduced cabin pressure and oxygen tension in the airplane cabin create an increased risk compared with seated immobility at ground level. OBJECTIVE: To determine whether hypobaric hypoxia, which may be encountered during air travel, activates hemostasis. DESIGN, SETTING, AND PARTICIPANTS: A single-blind, crossover study, performed in a hypobaric chamber, to assess the effect of an 8-hour seated exposure to hypobaric hypoxia on hemostasis in 73 healthy volunteers, which was conducted in the United Kingdom from September 2003 to November 2005. Participants were screened for factor V Leiden G1691A and prothrombin G20210A mutation and were excluded if they tested positive. Blood was drawn before and after exposure to assess activation of hemostasis. INTERVENTIONS: Individuals were exposed alternately (> or =1 week apart) to hypobaric hypoxia, similar to the conditions of reduced cabin pressure during commercial air travel (equivalent to atmospheric pressure at an altitude of 2438 m), and normobaric normoxia (control condition; equivalent to atmospheric conditions at ground level, circa 70 m above sea level). MAIN OUTCOME MEASURES: Comparative changes in markers of coagulation activation, fibrinolysis, platelet activation, and endothelial cell activation. RESULTS: Changes were observed in some hemostatic markers during the normobaric exposure, attributed to prolonged sitting and circadian variation. However, there were no significant differences between the changes in the hypobaric and the normobaric exposures. For example, the median difference in change between the hypobaric and normobaric exposure was 0 ng/mL for thrombin-antithrombin complex (95% CI, -0.30 to 0.30 ng/mL); -0.02 [corrected] nmol/L for prothrombin fragment 1 + 2 (95% CI, -0.03 to 0.01 nmol/L); 1.38 ng/mL for D-dimer (95% CI, -3.63 to 9.72 ng/mL); and -2.00% for endogenous thrombin potential (95% CI, -4.00% to 1.00%). CONCLUSION: Our findings do not support the hypothesis that hypobaric hypoxia, of the degree that might be encountered during long-haul air travel, is associated with prothrombotic alterations in the hemostatic system in healthy individuals at low risk of venous thromboembolism.

Idealised simulations of sting-jet cyclones

An idealised modelling study of sting-jet cyclones is presented. Sting jets are descending mesoscale jets that occur in some extratropical cyclones and produce localised regions of strong low-level winds in the frontal fracture region. Moist baroclinic lifecycle (LC1) simulations are performed with modifications to produce cyclones resembling observed sting-jet cyclones. A sting jet exists in the idealised control cyclone with similar characteristics to the sting jet in a simulation of windstorm Gudrun (a confirmed sting-jet case). Unlike in windstorm Gudrun, a low-level layer of strong moist static stability prohibits the descent of the strong winds from above the boundary layer to the surface in the idealised case. Conditional symmetric instability (CSI) exists in the cloud head and dissipates as the sting jet leaves the cloud head and descends. The descending, initially moist, sting-jet trajectories consistently have negative or near-zero saturated moist potential vorticity but moist static stability and inertial stability, consistent with CSI release; the moist static stability becomes negative during the period of most rapid descent, by which time the air is relatively dry implying conditional instability release is unlikely. Sensitivity experiments show that the existence of the sting jet is robust to changes in the initial state, and that the initial tropospheric static stability significantly impacts the descent rate of the sting jet. Inertial and conditional instability are probably being released in the experiment with the weakest initial static stability. This suggests that sting jets can arise through the release of all three instabilities associated with negative saturated moist potential vorticity. While evaporative cooling occurs along the sting-jet trajectories, a sensitivity experiment with evaporation effects turned off shows no significant change to the wind strength or descent rate of the sting jet implying that instability release is the dominant sting-jet driving mechanism.

Jet characterization in the upper troposphere/lower stratosphere (UTLS): applications to climatology and transport studies

A method of classifying the upper tropospheric/lower stratospheric (UTLS) jets has been developed that allows satellite and aircraft trace gas data and meteorological fields to be efficiently mapped in a jet coordinate view. A detailed characterization of multiple tropopauses accompanies the jet characterization. Jet climatologies show the well-known high altitude subtropical and lower altitude polar jets in the upper troposphere, as well as a pattern of concentric polar and subtropical jets in the Southern Hemisphere, and shifts of the primary jet to high latitudes associated with blocking ridges in Northern Hemisphere winter. The jet-coordinate view segregates air masses differently than the commonly-used equivalent latitude (EqL) coordinate throughout the lowermost stratosphere and in the upper troposphere. Mapping O3 data from the Aura Microwave Limb Sounder (MLS) satellite and the Winter Storms aircraft datasets in jet coordinates thus emphasizes different aspects of the circulation compared to an EqL-coordinate framework: the jet coordinate reorders the data geometrically, thus highlighting the strong PV, tropopause height and trace gas gradients across the subtropical jet, whereas EqL is a dynamical coordinate that may blur these spatial relationships but provides information on irreversible transport. The jet coordinate view identifies the concentration of stratospheric ozone well below the tropopause in the region poleward of and below the jet core, as well as other transport features associated with the upper tropospheric jets. Using the jet information in EqL coordinates allows us to study trace gas distributions in regions of weak versus strong jets, and demonstrates weaker transport barriers in regions with less jet influence. MLS and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer trace gas fields for spring 2008 in jet coordinates show very strong, closely correlated, PV, tropopause height and trace gas gradients across the jet, and evidence of intrusions of stratospheric air below the tropopause below and poleward of the subtropical jet; these features are consistent between instruments and among multiple trace gases. Our characterization of the jets is facilitating studies that will improve our understanding of upper tropospheric trace gas evolution.

Improving a convection-permitting model simulation of a cold air outbreak

A convection-permitting local-area model was used to simulate a cold air outbreak crossing from the Norwegian Sea into the Atlantic Ocean near Scotland. A control model run based on an operational configuration of the Met Office UKV high-resolution (1.5 km grid spacing) NWP model was compared to satellite, aircraft and radar data. While the control model captured the large-scale features of the synoptic situation, it was not able to reproduce the shallow (<1.5 km) stratiform layer to the north of the open cellular convection. Liquid water paths were found to be too low in both the stratiform and convective cloud regions. Sensitivity analyses including a modified boundary-layer diagnosis to generate a more well-mixed boundary layer and inhibition of ice formation to lower temperatures improved cloud morphology and comparisons with observational data. Copyright © 2013 Royal Meteorological Society and British Crown Copyright, the Met Office