Unsteady turbulence in a tidal bore: field measurements in the Garonne River in October 2013

A tidal bore is an unsteady rapidly-varied free-surface flow generated by the rapid rise in water elevation during the early flood tide, when the tidal range exceeds 4.5 to 6 m and the channel bathymetry amplifies the flood tidal wave. This study describes a detailed field investigation conducted in the Garonne River (France). The tidal bore was undular on 19 October 2013 and the bore front was followed by some well-defined whelps. The instantaneous velocity data indicated large and rapid fluctuations of all velocity components during the tidal bore. Large Reynolds shear stresses were observed during and after the tidal bore passage. Altogether the investigation characterised some unusual turbulence transient in a large river system

Turbulence and turbulent events in tidal bores: field observations

A tidal bore is a compressive wave of tidal origin, propagating upstream as the tidal flow turns to rising when a macro-tidal flood flow enters a funnel shaped river mouth with shallow waters. New field measurements were conducted in the Garonne River tidal bore at Arcins in 2015. Instantaneous velocity measurements were performed continuously at high-frequency prior to, during and after each bore. The bore occurrence had a marked effect on the velocity and turbulent Reynolds stress field, with large and rapid fluctuations, during the bore passage and the early flood tide. A turbulent event analysis was conducted in the highly unsteady rapidly-varied tidal bore flow. The method detects bursting events by comparing the absolute value of an instantaneous turbulent flux with its standard deviation. This analysis, based upon basic concepts, was extended to the rapidly varied, highly-unsteady tidal bore flood flow motion. The turbulent event data analysis showed relatively close results for all studies and all fluxes. A very large majority of turbulent events had a duration less than 0.01 s, with on average 20 turbulent events per second. During all studies, the event duration showed some tidal trend, with longer turbulent events immediately after the tidal bore passage, occurring simultaneously with sediment erosion processes

Fate of drugs during wastewater treatment

This is the post-print version of the final paper published in TrAC Trends in Analytical Chemistry. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2013 Elsevier B.V.Recent trends in the determination of pharmaceutical drugs in wastewaters focus on the development of rapid multi-residue methods. This review addresses recent analytical trends in drug determination in environmental matrices used to facilitate fate studies. Analytical requirements for further fate evaluation and tertiary process selection and optimization are also discussed.EPSRC, Northumbrian Water, Anglian Water, Severn Trent Water, Yorkshire Water, and United Utilities

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

Temperature measurement by infrared thermography in a lubricated contact: radiometric analysis

Abstract A method of surface temperature measurement by infrared thermography in a lubricated contact has been developed. The capabilities of the camera are examined. The analysis, which needs the determination of global radiometric coefficients and leads to radiometric equations is presented. The calibration of emissivity and transmittivity coefficients of the involved materials is reported. The validity of the method is tested and discussed. Nomenclature E global coefficient of emission L radiant intensity M radiative power R global coefficient of reflectio

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