Fear follows form Strandbygaard, Sofie Kirt; Jones, Alan Keith Spence; Jensen, Lotte M. B. ...
Journal of transport and land use,
01/2020, Letnik:
13, Številka:
1
Journal Article
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In pursuing fear-reduction strategies in public transport, the total experience of accessing rail stations should be taken into account. This article correlates passengers' fear of crime at train ...stations with neighborhood types and income data within the pedestrian catchment area. The research is based on urban form and income around 84 S-train stations in the Copenhagen metropolitan area and nine years of passenger surveys on fear of crime at these stations. The study reveals a significant positive correlation between low income and fear of crime; the lower the income in an urban area, the more unsafe passengers feel at the station. However, when controlling for the relationship between income, safety and neighborhood type, stations in neighborhoods with urban form associated with low incomes have the lowest ratings of safety. The research indicates that train passengers' sense of security is connected to neighborhood type and the city's planning characteristics. This is an important finding for urban designers and planners working on the integration of public transport and station design in urban areas.
Hydrochemical data, compound specific carbon isotope analysis and isotopic enrichment trends in dissolved hydrocarbons and residual electron acceptors have been used to deduce BTEX and MTBE ...degradation pathways in a fractured chalk aquifer. BTEX compounds are mineralised sequentially within specific redox environments, with changes in electron acceptor utilisation being defined by the exhaustion of specific BTEX components. A zone of oxygen and nitrate exhaustion extends approximately 100 m downstream from the plume source, with residual sulphate, toluene, ethylbenzene and xylene. Within this zone complete removal of the TEX components occurs by bacterial sulphate reduction, with sulphur and oxygen isotopic enrichment of residual sulphate (
ε
s=−
14.4‰ to −
16.0‰). Towards the plume margins and at greater distance along the plume flow path nitrate concentrations increase with
δ
15N values of up to +
40‰ indicating extensive denitrification. Benzene and MTBE persist into the denitrification zone, with carbon isotope enrichment of benzene indicating biodegradation along the flow path. A Rayleigh kinetic isotope enrichment model for
13C-enrichment of residual benzene gives an apparent
ε value of −
0.66‰. MTBE shows no significant isotopic enrichment (
δ
13C
=
−
29.3‰ to −
30.7‰) and is isotopically similar to a refinery sample (
δ
13C
=
−
30.1‰). No significant isotopic variation in dissolved MTBE implies that either the magnitude of any biodegradation-induced isotopic fractionation is small, or that relatively little degradation has taken place in the presence of BTEX hydrocarbons. It is possible, however, that MTBE degradation occurs under aerobic conditions in the absence of BTEX since no groundwater samples were taken with co-existing MTBE and oxygen. Low benzene
δ
13C values are correlated with high sulphate
δ
34S, indicating that little benzene degradation has occurred in the sulphate reduction zone. Benzene degradation may be associated with denitrification since increased benzene
δ
13C is associated with increased
δ
15N in residual nitrate. Re-supply of electron acceptors by diffusion from the matrix into fractures and dispersive mixing is an important constraint on degradation rates and natural attenuation capacity in this dual-porosity aquifer.
► Carbon isotope fractionation for MTBE varies with dissolved oxygen concentration. ► Carbon isotope fractionation can underestimate MTBE biodegradation at plume fringes. ► Fractionation factors must ...be for specific biodegradation mechanisms and conditions. ► Specific microbial populations influence carbon isotope fractionation in groundwater.
Radiolabelled assays and compound-specific stable isotope analysis (CSIA) were used to assess methyl tert-butyl ether (MTBE) biodegradation in an unleaded fuel plume in a UK chalk aquifer, both in the field and in laboratory microcosm experiments. The 14C-MTBE radiorespirometry studies demonstrated widespread potential for aerobic and anaerobic MTBE biodegradation in the aquifer. However, δ13C compositions of MTBE in groundwater samples from the plume showed no significant 13C enrichment that would indicate MTBE biodegradation at the field scale. Carbon isotope enrichment during MTBE biodegradation was assessed in the microcosms when dissolved O2 was not limiting, compared with low in situ concentrations (2mg/L) in the aquifer, and in the absence of O2. The microcosm experiments showed ubiquitous potential for aerobic MTBE biodegradation in the aquifer within hundreds of days. Aerobic MTBE biodegradation in the microcosms produced an enrichment of 7‰ in the MTBE δ13C composition and an isotope enrichment factor (ε) of −1.53‰ when dissolved O2 was not limiting. However, for the low dissolved O2 concentration of up to 2mg/L that characterizes most of the MTBE plume fringe, aerobic MTBE biodegradation produced an enrichment of 0.5–0.7‰, corresponding to an ε value of −0.22‰ to −0.24‰. No anaerobic MTBE biodegradation occurred under these experimental conditions. These results suggest the existence of a complex MTBE-biodegrading community in the aquifer, which may consist of different aerobic species competing for MTBE and dissolved O2. Under low O2 conditions, the lower fractionating species have been shown to govern overall MTBE C-isotope fractionation during biodegradation, confirming the results of previous laboratory experiments mixing pure cultures. This implies that significant aerobic MTBE biodegradation could occur under the low dissolved O2 concentration that typifies the reactive fringe zone of MTBE plumes, without producing detectable changes in the MTBE δ13C composition. This observed insensitivity of C isotope enrichment to MTBE biodegradation could lead to significant underestimation of aerobic MTBE biodegradation at field scale, with an unnecessarily pessimistic performance assessment for natural attenuation. Site-specific C isotope enrichment factors are, therefore, required to reliably quantify MTBE biodegradation, which may limit CSIA as a tool for the in situ assessment of MTBE biodegradation in groundwater using only C isotopes.
This paper presents a typomorphological analysis of train station neighbourhoods to examine passengers' fear of crime at the station in relation to the surrounding urban form. The study defines ...station neighbourhood types in the Copenhagen Metropolitan area within the pedestrian catchment area, an 800 m (1/2 mile) radius around the 84 S-train stations. The types are defined through a typomorphological analysis based on urban parameters related to Crime Prevention Through Environmental Design (CPTED) and Placemaking. The types are compared with 9 years of passenger surveys of fear of crime at these stations. The analysis establishes three dominant station neighbourhood types and demonstrates the relationship between them and passengers' fear of crime at the stations. The research underlines the importance of the surrounding urban environment in the design and governance of train stations, and proposes a typomorphological method to identify potentials in regional planning and in upgrade of transit-oriented developments.
Diffusion equilibrium exchange (DEE) is presented as a novel, practical alternative to centrifugation for the recovery and chemical analysis of interstitial water in contaminated core samples from ...consolidated rocks and aquifers. The methodology is suitable for sampling organic and inorganic compounds, including redox sensitive species such as SO4 2-, NO3 -, NO2 -, Mn(II), Fe(II), and sulfide (HS-). DEE also permits analyte extraction from kilogram quantities of core, which avoids extended centrifugation or sample amalgamation and provides analyte masses appropriate for stable isotope analysis. The procedure involves simple and rapid on-site sectioning of representative core samples, which are preserved in the field by storage in airtight bottles filled with deoxygenated deionized water containing a conservative tracer (Br-). Equilibration times for individual solutes can be estimated in advance to reduce the need for time-series analysis; for an effective diffusion coefficient of 2.5 × 10-10 m2 s-1 (Br- in chalk rock) equilibration was >90% completed after 30 h, consistent with the predicted equilibration time. The DEE method presented minimizes sampling errors from temperature changes, oxidation of reduced chemical species, and loss of volatile compounds, which can occur with other interstitial water sampling techniques. It also gives superior resolution of in situ solute distributions and geochemical processes in consolidated sediments than centrifugation and can provide estimates of aquifer porosity in core samples. Laboratory experiments using chalk rock core and simulated extraction procedures confirm the superior performance of the DEE method over centrifugation for a range of solutes. The method has been used to generate detailed interstitial water profiles of electron acceptor and contaminant concentrations along the flow path of a petroleum hydrocarbon plume in the U.K. Upper Chalk aquifer as part of a natural attenuation assessment.
Radiolabelled assays and compound-specific stable isotope analysis (CSIA) were used to assess methyl tert-butyl ether (MTBE) biodegradation in an unleaded fuel plume in a UK chalk aquifer, both in ...the field and in laboratory microcosm experiments. The super(14)C-MTBE radiorespirometry studies demonstrated widespread potential for aerobic and anaerobic MTBE biodegradation in the aquifer. However, Delta super(13)C compositions of MTBE in groundwater samples from the plume showed no significant super(13)C enrichment that would indicate MTBE biodegradation at the field scale. Carbon isotope enrichment during MTBE biodegradation was assessed in the microcosms when dissolved O sub(2) was not limiting, compared with low in situ concentrations (2 mg/L) in the aquifer, and in the absence of O sub(2). The microcosm experiments showed ubiquitous potential for aerobic MTBE biodegradation in the aquifer within hundreds of days. Aerobic MTBE biodegradation in the microcosms produced an enrichment of 7ppt in the MTBE Delta super(13)C composition and an isotope enrichment factor ( epsilon ) of -1.53ppt when dissolved O sub(2) was not limiting. However, for the low dissolved O sub(2) concentration of up to 2 mg/L that characterizes most of the MTBE plume fringe, aerobic MTBE biodegradation produced an enrichment of 0.5-0.7ppt, corresponding to an epsilon value of -0.22ppt to -0.24ppt. No anaerobic MTBE biodegradation occurred under these experimental conditions. These results suggest the existence of a complex MTBE-biodegrading community in the aquifer, which may consist of different aerobic species competing for MTBE and dissolved O sub(2). Under low O sub(2) conditions, the lower fractionating species have been shown to govern overall MTBE C-isotope fractionation during biodegradation, confirming the results of previous laboratory experiments mixing pure cultures. This implies that significant aerobic MTBE biodegradation could occur under the low dissolved O sub(2) concentration that typifies the reactive fringe zone of MTBE plumes, without producing detectable changes in the MTBE Delta super(13)C composition. This observed insensitivity of C isotope enrichment to MTBE biodegradation could lead to significant underestimation of aerobic MTBE biodegradation at field scale, with an unnecessarily pessimistic performance assessment for natural attenuation. Site-specific C isotope enrichment factors are, therefore, required to reliably quantify MTBE biodegradation, which may limit CSIA as a tool for the in situ assessment of MTBE biodegradation in groundwater using only C isotopes.
The Chargers' defense stopped Gates County cold after the onside kick, then Ayden-Grifton's offense proceeded to reach the end zone on 10 of its 11 possessions, rolling up 463 total yards to rout the ...fourth-seeded Red Barons, 70-14, Friday in the second round of the state 1AA playoffs.
A highly questionable ruling at first base leading off the bottom of the eighth inning allowed the eventual winning run to reach base as the Vikings dropped a heartbreaking 2-1 decision to Farmville ...Central Friday night.
After forcing a decisive title game with a dramatic victory earlier in the day, Shelby ran out of gas in the nightcap, falling to Area III champion Rowan County 5-3.at Clark-LeClair Stadium on the ...campus of East Carolina University.
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