Constraints on aerosol nitrate photolysis as a potential source of HONO and NOx, Environmental Science and Technology

The concentration of nitrogen oxides (NOx) plays a central role in controlling air quality. On a global scale, the primary sink of NOx is oxidation to form HNO3. Gas-phase HNO3 photolyses slowly with a lifetime in the troposphere of 10 days or more. However, several recent studies examining HONO chemistry have proposed that particle-phase HNO3 undergoes photolysis 10–300 times more rapidly than gas-phase HNO3. We present here constraints on the rate of particle-phase HNO3 photolysis based on observations of NOx and HNO3 collected over the Yellow Sea during the KORUS-AQ study in summer 2016. The fastest proposed photolysis rates are inconsistent with the observed NOx to HNO3 ratios. Negligible to moderate enhancements of the HNO3 photolysis rate in particles, 1–30 times faster than in the gas phase, are most consistent with the observations. Small or moderate enhancement of particle-phase HNO3 photolysis would not significantly affect the HNO3 budget but could help explain observations of HONO and NOx in highly aged air

The Future of Agent-Based Modeling

In this paper, I elaborate on the role of agent-based (AB) modeling for macroeconomic research. My main tenet is that the full potential of the AB approach has not been realized yet. This potential lies in the modular nature of the models, which is bought by abandoning the straitjacket of rational expectations and embracing an evolutionary perspective. I envisage the foundation of a Modular Macroeconomic Science, where new models with heterogeneous interacting agents, endowed with partial information and limited computational ability, can be created by recombining and extending existing models in a unified computational framework

Price discovery in the CDS market: the informational role of equity short interest

This paper documents a negative relation between equity short interest and future returns on credit default swaps (CDS). This relation is most consistent with the theory that equity short interest telegraphs relevant information to secondary market CDS investors about credit spread not transmitted into prices in other ways. The CDS return predictive pattern also strengthens negatively for equity short-interest positions subject to an outward shift in the demand for shortable stocks, which we view as a proxy for the expected benefits of private information (Cohen et al. in J Finance 62(5):2061–2096, 2007). This suggests that features of the shorting market may help explain the lagged response of CDS spreads to equity short interest. Our tests of economic significance, however, do not support the view that the CDS return predictive pattern is strong enough to cover the round-trip cost of trading in the secondary CDS market

The development of strategic and tactical tools, using systems analysis, for waste management in large complex organisations: a case study in UK healthcare waste

Healthcare waste management within the United Kingdom (UK) has been identified as an area requiring extensive adoption of Best Practice (DETR, 2000). The National Health Service (NHS) generated 384,698 tonnes of waste in 2001. In order to manage this waste effectively, strategic and tactical tools within the NHS are required, which is a large complex organisation. Examples of such tools which could be used to deliver Best Practice within a hospital environment are the Strategic Waste Achievement Programme (SWAP) methodology and structured systems analysis design method (SSADM). SWAP is a strategic tool for senior managers and policy makers that can be used to develop sustainable waste management programmes and strategies for the whole organisation. An outline of SWAP is included in this paper. SSADM is the standard methodology used by the UK government for the development of their information systems. Some functional aspects of SSADM have been adapted for the documentation of waste generation and waste streams within an acute general hospital. A diagrammatic representation of the systems in place is the output from the waste flow diagrams (WFDs). These are relevant to the tactical levels within the organisation as the diagrams can be ‘walked through’ with the hospital managers and staff. The adoption of the methodology led to easily identified savings, amounting to over £28,000 for no capital outlay

Radon mitigation in domestic properties and its health implications - a comparison between during-construction and post-construction radon reduction

Although United Kingdom (UK) Building Regulations applicable to houses constructed since 1992 in Radon Affected Areas address the health issues arising from the presence of radon in domestic properties and specify the installation of radon-mitigation measures during construction, no legislative requirement currently exists for monitoring the effectiveness of such remediation once construction is completed and the houses are occupied. To assess the relative effectiveness of During-Construction radon reduction and Post-Construction remediation, radon concentration data from houses constructed before and after 1992 in Northamptonshire, UK, a designated Radon Affected Area, was analysed. Post-Construction remediation of 73 pre-1992 houses using conventional fan-assisted sump technology proved to be extremely effective, with radon concentrations reduced to the Action Level, or below, in all cases. Of 64 houses constructed since 1992 in a well-defined geographical area, and known to have had radon-barrier membranes installed during construction, 11% exhibited radon concentrations in excess of the Action Level. This compares with the estimated average for all houses in the same area of 17%, suggesting that, in some 60% of the houses surveyed, installation of a membrane has not resulted in reduction of mean annual radon concentrations to below the Action Level. Detailed comparison of the two data sets reveals marked differences in the degree of mitigation achieved by remediation. There is therefore an ongoing need for research to resolve definitively the issue of radon mitigation and to define truly effective anti-radon measures, readily installed in domestic properties at the time of construction. It is therefore recommended that mandatory testing be introduced for all new houses in Radon Affected Area

Domestic radon remediation of U.K. dwellings by sub-slab depressurisation: evidence for a baseline contribution from constructional materials

To quantify the effectiveness of Sub-Slab Depressurisation, widely used in the United Kingdom (U.K.) to mitigate indoor radon gas levels in residential properties, a study was made of radon concentration data collected from a set of 170 homes situated in Radon Affected Areas in Northamptonshire and neighbouring counties, remediated using conventional sump/pump technology. A high incidence of satisfactory remediation outcomes was achieved, with 100% of the houses remediated demonstrating post-remediation radon concentrations below the U.K. domestic Action Level of 200 Bq m− 3, while more than 75% of the sample exhibited radon mitigation factors (defined as the ratio of radon concentrations following and prior to remediation) < 0.2. Two systematic trends are identified. Firstly, absolute radon concentration reduction following remediation is directly proportional to initial radon concentration, with a mean reduction factor of 0.96 and a residual component of around 75 Bq m− 3. Secondly, houses with lower initial radon concentrations demonstrate poorer (higher) mitigation factors. These observations support a model in which the total indoor radon concentration within a dwelling can be represented by two principal components, one susceptible to mitigation by sub-slab depressurisation, the other remaining essentially unaffected. The first component can be identified with radon emanating from the subsoil and bedrock geologies, percolating through the foundations of the dwelling as a component of the soil-gas, and potentially capable of being attenuated by sub-slab depressurisation or radon-barrier remediation technologies. The second contribution can be identified with radon emanating from materials used in the construction of the dwelling with a further contribution from the natural background level, and is essentially unaffected by ground-level remediation strategies. Modelling of a multi-component radon dependency using ground-radon attenuation factors derived from the experimental data, in conjunction with typical background and structural-radon levels, yields behaviour in good agreement with the observed dependence of mitigation factor on initial radon concentratio

Time-integrating radon gas measurements in domestic premises: comparison of short-, medium- and long-term exposures

To identify the most applicable technology for the short-term assessment of domestic radon levels, comparative assessments of a number of integrating detector types, including track-etch, electret and activated charcoal were undertaken. Thirty-four unremediated dwellings in a high-radon area were monitored using track-etch detectors exposed for one-month and three-month periods. In parallel, one-week measurements were made in the same homes at one-month intervals, using co-located track-etch, charcoal and electret detectors exposed simultaneously, while three of the homes were also monitored by continuous-sampling detectors at hourly intervals over extended periods. Calibration of dose-integrating devices against each other and against continuous-monitoring systems confirmed good responsivity and linearity. Although track-etch, charcoal and electret devices are suitable in principle for one-week measurements, zero-exposure offset and natural radon variability cause many one-week results to be equivocal, necessitating repetition of the measurement. One-week exposures can be reliable indicators in low-radon areas or for new properties, but in high-radon areas, the use of three-month exposures is indicated. This analysis also established confidence limits for short-term measurement

Comparative analysis of weekly vs. three monthly radon measurements in dwellings

34 unremediated dwellings in a high-radon area were monitored with three types of dose-integrating radon detector. 20 homes were monitored for 4 consecutive 3-month periods and simultaneously for 12 consecutive 1-month periods; the remainder were monitored for 9 months (4 properties), 6 months (6 properties) or 3 months (4 properties). In addition, 1-week measurements were made at 1-month intervals, using co-located Track-Etch, Activated Charcoal and Electret detectors simultaneously. Calibration of dose-integrating devices against continuous-monitoring systems confirmed good responsivity and linearity. Although Track-Etch, Activated Charcoal and Electret devices are suitable in principle for one-week measurements, zero-exposure offset and natural radon variability mean that many one-week results will be equivocal and will need to be repeated. During the work, the chosen Track-Etch detector supplier abandoned the market, necessitating identification of a replacement, raising concerns over equivalence of results from nominally identical products from different sources and necessitating statistical compensation. Analysis of the data-set permitted derivation of confidence limits for the estimation of long-term average radon concentrations from short-term measurements