Land use regression modeling of intra-urban residential variability in multiple traffic-related air pollutants

Background: There is a growing body of literature linking GIS-based measures of traffic density to asthma and other respiratory outcomes. However, no consensus exists on which traffic indicators best capture variability in different pollutants or within different settings. As part of a study on childhood asthma etiology, we examined variability in outdoor concentrations of multiple traffic-related air pollutants within urban communities, using a range of GIS-based predictors and land use regression techniques. Methods: We measured fine particulate matter (PM2.5), nitrogen dioxide (NO2), and elemental carbon (EC) outside 44 homes representing a range of traffic densities and neighborhoods across Boston, Massachusetts and nearby communities. Multiple three to four-day average samples were collected at each home during winters and summers from 2003 to 2005. Traffic indicators were derived using Massachusetts Highway Department data and direct traffic counts. Multivariate regression analyses were performed separately for each pollutant, using traffic indicators, land use, meteorology, site characteristics, and central site concentrations. Results: PM2.5 was strongly associated with the central site monitor (R2 = 0.68). Additional variability was explained by total roadway length within 100 m of the home, smoking or grilling near the monitor, and block-group population density (R2 = 0.76). EC showed greater spatial variability, especially during winter months, and was predicted by roadway length within 200 m of the home. The influence of traffic was greater under low wind speed conditions, and concentrations were lower during summer (R2 = 0.52). NO2 showed significant spatial variability, predicted by population density and roadway length within 50 m of the home, modified by site characteristics (obstruction), and with higher concentrations during summer (R2 = 0.56). Conclusion: Each pollutant examined displayed somewhat different spatial patterns within urban neighborhoods, and were differently related to local traffic and meteorology. Our results indicate a need for multi-pollutant exposure modeling to disentangle causal agents in epidemiological studies, and further investigation of site-specific and meteorological modification of the traffic-concentration relationship in urban neighborhoods

Turbulence measurements in the Garonne River tidal bore: First observations

A tidal bore is an abrupt rise in water depth advancing in some estuaries during spring tide conditions. In the present study, some detailed turbulence field measurements were conducted continuously at high-frequency (64 Hz) in the Garonne River tidal bore. The turbulent velocity components were sampled with an acoustic Doppler velocimeter (ADV) at 0.8 m beneath the freesurface. On 10 and 11 Sept. 2010, the tidal bore was undular as it passed in front of the sampling site. The tidal bore Froude number estimated from the channel bathymetry and observations was equal to 1.20 and 1.30 on 10 and 11 Sept. 2010 respectively. The turbulent velocity data showed the marked impact of the tidal bore propagation. The longitudinal velocity component highlighted some rapid flow deceleration during the passage of the tidal bore, associated with a sudden rise in the free surface elevation, and a flow reversal after the tidal bore front passage. The Reynolds stress data indicated some large amplitudes and rapid fluctuations during the tidal bore and flood flow. These field observations are the first detailed turbulence measurements in a tidal bore with high spatial and temporal resolutions

Organic micropollutant removal during river bank filtration: batch studies

Organic micropollutant (OMP) removal during river bank filtration (RBF) under oxic conditions was simulated in a batch experiment. A cocktail of 16 OMPs, with varying physico-chemical properties, was dosed to try to relate OMP removal behavior to these properties. An indication for the biodegradation potential of the OMPs was obtained by comparing a batch filled with sand and river water to a batch filled with sand, river water and sodium azide (NaN3) as biocide. It is concluded that all charged, both positive and negative compounds, are biodegraded. For neutral compounds there is no clear trend visible for biodegradation potential: metolachlor, diuron, caffeine and lincomycin (Log D ranging from -0.64 to 3.44) are neutral and biodegraded. Atrazine, carbamazepine, phenytoin and sulfadiazine (Log D ranging from -0.14 to 2.63) are also neutral but not biodegraded. Both neutral groups cover the same range in Log D which implies that other factors/physico-chemical properties than hydrophobicity are playing a role in the biodegradation behavior of neutral compounds. Further research is required to determine the origin of biodegradation potential of neutral compounds. The addition of an easily biodegradable carbon source (sodium acetate) at regular time intervals did not have a significant effect on OMP removal after 14 days. Further research should explain whether this was caused by a lack of nutrients or the water:sand ratio and the dosed concentration OMPs. Since OMP removal is similar in the batch filled with river water and sand and the batch filled with demineralized water and sand after 14 days, it can be concluded that OMP removal mainly takes place in the soil phase. This was expected since in the soil more biomass (biofilm) is present and this biomass seems to play an important role in OMP removal

Integration Concept of the Reflectometry Diagnostic for the Main Plasma in DEMO

This paper presents the initial conceptual study of integration of reflectometry antennas and waveguides (WGs) in DEMO. The antennas are located at several poloidal angular positions covering a full poloidal section of the helium-cooled lithium lead breading blanket. The concept of slim cassette (SC) is presented which allows for possible side attachment to the blanket sector and offers compatibility with remote handling (RH) operations. The proposed concepts for WGs sectors relative motion decoupling, vacuum boundary breaking, and RH are presented. Monte Carlo neutronic simulations have been done in order to evaluate the heat loads and shielding capabilities of the system. The first results indicate that the cooling for the EUROFER diagnostic components (antennas and WGs) can in principle be provided by the blanket cooling services (He is considered) via connection to the main back supporting structure and routed via the main diagnostic structure body. The first results on the SC thermal analysis indicate that for the first wall (FW), an increase of He speed is required (or a higher cooling volume) as temperatures are above blanket FW temperature. As for the inner components (shielding and wave guides), the cooling requires localized optimization (hot spots in module corners and front antennas) but respects average temperature limit requirement

Integration Concept of the Reflectometry Diagnostic for the Main Plasma in DEMO

This paper presents the initial conceptual study of integration of reflectometry antennas and waveguides (WGs) in DEMO. The antennas are located at several poloidal angular positions covering a full poloidal section of the helium-cooled lithium lead breading blanket. The concept of slim cassette (SC) is presented which allows for possible side attachment to the blanket sector and offers compatibility with remote handling (RH) operations. The proposed concepts for WGs sectors relative motion decoupling, vacuum boundary breaking, and RH are presented. Monte Carlo neutronic simulations have been done in order to evaluate the heat loads and shielding capabilities of the system. The first results indicate that the cooling for the EUROFER diagnostic components (antennas and WGs) can in principle be provided by the blanket cooling services (He is considered) via connection to the main back supporting structure and routed via the main diagnostic structure body. The first results on the SC thermal analysis indicate that for the first wall (FW), an increase of He speed is required (or a higher cooling volume) as temperatures are above blanket FW temperature. As for the inner components (shielding and wave guides), the cooling requires localized optimization (hot spots in module corners and front antennas) but respects average temperature limit requirement