scholarly journals Direct determination of highly size-resolved turbulent particle fluxes with the disjunct eddy covariance method and a 12 – stage electrical low pressure impactor

2008 ◽  
Vol 8 (24) ◽  
pp. 7405-7417 ◽  
Author(s):  
A. Schmidt ◽  
O. Klemm
Keyword(s):  
Eddy Covariance ◽  
Aerosol Particles ◽  
Direct Determination ◽  
Low Pressure ◽  
West Germany ◽  
City Centre ◽  
Eddy Covariance Method ◽  
North West ◽  
Particle Fluxes ◽  
The City

Abstract. During summer 2007, turbulent vertical particle mass and number fluxes were measured for a period of 98 days near the city centre of Münster in north-west Germany. For this purpose, a valve controlled disjunct eddy covariance system was mounted at 65 m a.g.l. on a military radio tower. The concentration values for 11 size bins with aerodynamic diameters (D50) from 0.03 to 10 μm were measured with an electrical low pressure impactor. After comparison with other fluxes obtained from 10 Hz measurements with the classical eddy covariance method, the loss of information concerning high frequent parts of the flux could be stated as negligible. The results offer an extended insight in the turbulent atmospheric exchange of aerosol particles by highly size-resolved particle fluxes covering 11 size bins and show that the city of Münster acts as a relevant source for aerosol particles. Significant differences occur between the fluxes of the various particle size classes. While the total particle number flux shows a pattern which is strictly correlated to the diurnal course of the turbulence regime and the traffic intensity, the total mass flux exhibits a single minimum in the evening hours when coarse particles start to deposit. As a result, a mean mass deposition of about 10 mg m−2 per day was found above the urban test site, covering the aerosol size range from 40 nm to 2.0 μm. By contrast, the half-hourly total number fluxes accumulated over the lower ELPI stages range from −4.29×107 to +1.44×108 particles m−2 s−1 and are clearly dominated by the sub-micron particle fraction of the impactor stages with diameters between 40 nm and 320 nm. The averaged number fluxes of particles with diameters between 2.0 and 6.4 μm show lower turbulent dynamics during daytime and partially remarkably high negative fluxes with mean deposition velocities of 2×10−3 m s−1 that appear temporary during noontime and in the evening hours.

scholarly journals Direct determination of highly size-resolved turbulent particle fluxes with the disjunct eddy covariance method and a 12 – stage electrical low pressure impactor

2008 ◽  
Vol 8 (3) ◽  
pp. 8997-9034 ◽  
Author(s):  
A. Schmidt ◽  
O. Klemm
Keyword(s):  
Eddy Covariance ◽  
Aerosol Particles ◽  
Direct Determination ◽  
Low Pressure ◽  
West Germany ◽  
City Centre ◽  
Eddy Covariance Method ◽  
North West ◽  
Particle Fluxes ◽  
The City

Abstract. During summer 2007, turbulent vertical particle fluxes were measured for a period of 98 days near the city centre of Münster in north-west Germany. For this purpose, a valve controlled disjunct eddy covariance system was mounted at 65 m a.g.l. on a military radio tower. The concentration values for 11 size bins with aerodynamic diameters (D50) from 0.03 to 10 μm were measured with an electrical low pressure impactor. After comparison with other fluxes obtained from 10 Hz measurements with the classical eddy covariance method, the loss of information concerning high frequent parts of the flux could be stated as negligible. The results offer an extended insight in the turbulent atmospheric exchange of aerosol particles by highly size-resolved particle fluxes covering 11 size bins and show that the city of Münster acts as a relevant source for aerosol particles. Significant differences occur between the fluxes of the various particle size classes. While the total particle number flux shows a pattern which is strictly correlated to the diurnal course of the turbulence regime and the traffic intensity, the total mass flux exhibits a single minimum in the evening hours when coarse particles start to deposit. As a result, a mean mass deposition of about 10 g m−2 per day was found above the urban test site, covering the aerosol size range from 40 nm to 2.0 μm. By contrast, the half-hourly total number fluxes accumulated over the lower ELPI stages range from –4.29×107 to +1.44×108 particles m−2 s-1 and are clearly dominated by the sub-micron particle fraction of the impactor stages with diameters between 40 nm and 320 nm. The averaged number fluxes of particles with diameters between 2.0 and 6.4 μm show lower turbulent dynamics during daytime and partially remarkably high negative fluxes with mean deposition velocities of 2×10−3 m s−1 that appear temporary during noontime and in the evening hours.

scholarly journals Physico-chemical and bacteriological characterisation of surface water in Bamenda (North West Cameroon)

2021 ◽  
Vol 11 (12) ◽  
Author(s):  
Alice Magha Mufur ◽  
Margaret Tita Awah ◽  
Gus Djibril Kouankap Nono ◽  
Primus Azinwi Tamfuh ◽  
Pierre Wotchoko ◽  
...  
Keyword(s):  
River Water ◽  
Principal Component ◽  
Point Sources ◽  
Ion Concentration ◽  
City Centre ◽  
Physical Parameters ◽  
Water Type ◽  
North West ◽  
Physico Chemical ◽  
The City

AbstractThe Mezam River and its tributaries constitute a prominent water source for domestic use and vegetable irrigation in Bamenda Town (North West Cameroon). The river flows through the city and is thus vulnerable to impairment by substances from point and non-point sources. This current research aims to assess the degree of pollution of the Mezam River water to ascertain its suitability for various uses. A total of 24 water samples were collected from six segments of the Mezam River basin in the dry and rainy seasons during the years 2015 and 2016 in view of physico-chemical and bacteriological analyses. In situ measurement of physical parameters was taken in the field. The data were analysed by multivariate statistical techniques (principal component analysis and factor analysis). The results revealed that the river water is slightly acidic (pH = 5.45–6.47) and ion concentration is low (41.67–237.00 µS/cm). The water type is Ca-SO4 and Ca-Mg-(Cl + NO3) in the dry season and Ca-Mg-SO4 in the rainy season. High NO3− values (50 mg/l) are recorded at Nkimefueh. The Mezam River water is heavily polluted with indicator bacteria (0–500 CFU/100 ml) whose concentrations steadily increase from the reference point (YB) through sampling points in the city centre, suggesting the influence of human-induced activities. The population is urged to adopt a responsible behaviour towards waste disposal and refrain from disposing waste in water courses in order to safeguard the aquatic environment and also protect the health of the population.

scholarly journals Eddy covariance measurements of the net turbulent methane flux in the city centre – results of 2 years campaign in Łódź, Poland

2016 ◽  
Author(s):  
W. Pawlak ◽  
K. Fortuniak
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Vertical Component ◽  
Ground Level ◽  
Methane Flux ◽  
City Centre ◽  
Carbon Dioxide Fluxes ◽  
Methane Fluxes ◽  
Eddy Covariance Measurements ◽  
The City

Abstract. In the period between July 2013 and August 2015, continuous measurements of turbulent methane exchange between an urbanised area and the atmosphere were carried out in Łódź. Such long, continuous measurement series of turbulent methane exchange between the city and the atmosphere are still a rarity. The measurement station was located in the centre of the city, where fluxes of energy (sensible and latent heat) and fluxes of mass (carbon dioxide) have been continuously measured since 2000 and 2007, respectively. In the immediate vicinity of the measurement station there are potential sources of methane, such as streets with vehicle traffic or dense sewerage and natural gas networks. To determine the fluxes, the eddy covariance technique was used; the measurement station was equipped with instruments for recording fluctuations in the vertical component of the wind speed (an ultrasonic 3D anemometer, RM Young 81000, RM Young, USA) as well as the concentration of methane in the air (an open path Li 7700 CH4 Analyser, Li-cor, USA). The devices were mounted on a mast at a height of 37 metres above ground level and, on average, 20 metres over the roofs of the surrounding buildings. The results were therefore averaged for an area with a diameter of approximately 1 kilometre. Our aim was to investigate the temporal variability of the turbulent exchange of methane in the city-atmosphere system. The results show in the first place that positive methane fluxes (turbulent gas transport from the surface to the atmosphere) definitely dominate compared with negative fluxes. This indicates that the study area of the centre of Łódź is a net source of methane to the troposphere. The measurements also indicated the existence of a clear annual rhythm of the turbulent flux of methane in the centre of Łódź (on average, the values observed in winter amounted to ~40–60 nmol m−2 s−1 and were significantly larger than in summer). The daily variability of the flux of CH4 (FCH4) is faintly visible throughout the year. The studied area of the centre of Łódź is also characterised by a cycle of methane exchange – the values measured on working days were higher by 6.6 % (winter) to 5.6 % (summer) than those observed at weekends. The largest monthly exchange was characteristic of winter months (from 2.0 to 2.7 g m−2 month−1) and the lowest occurred in summer (from 0.8 to 1.0 g m−2 month−1). The mean daily patterns of FCH4 in consecutive months were used to determine the cumulative annual exchange. In 2014, the centre of Łódź emitted a net quantity of almost 18 g m−2. Furthermore, the study analyses the covariability of methane and carbon dioxide fluxes.

scholarly journals Building a predictive machine learning model of gentrification in Sydney

2021 ◽  
Author(s):  
William Thackway ◽  
Matthew Kok Ming Ng ◽  
Chyi Lin Lee ◽  
Christopher Pettit
Keyword(s):  
Machine Learning ◽  
City Centre ◽  
North West ◽  
Vulnerable Communities ◽  
Policy Interventions ◽  
South West ◽  
Socioeconomic Index ◽  
Machine Learning Model ◽  
Neighbourhood Change ◽  
The City

In an era of rapid urbanisation and increasing wealth, gentrification is an urban phenomenon impacting many cities around the world. The ability of policymakers and planners to better understand and address gentrification-induced displacement hinges upon proactive intervention strategies. It is in this context that we build a tree-based machine learning (ML) model to predict neighbourhood change in Sydney. Change, in this context, is proxied by the Socioeconomic Index for Advantage and Disadvantage, in addition to census and other ancillary predictors. Our models predict gentrification from 2011-2016 with a balanced accuracy of 74.7%. Additionally, the use of an additive explanation tool enables individual prediction explanations and advanced feature contribution analysis. Using the ML model, we predict future gentrification in Sydney up to 2021. The predictions confirm that gentrification is expanding outwards from the city centre. A spill-over effect is predicted to the south, west and north-west of former gentrifying hotspots. The findings are expected to provide policymakers with a tool to better forecast where likely areas of gentrification will occur. This future insight can then inform suitable policy interventions and responses in planning for more equitable cities outcomes, specifically for vulnerable communities impacted by gentrification and neighbourhood change.

Spatiotemporal dynamics of CO2 flux in Basel city centre

2021 ◽  
Author(s):  
Stavros Stagakis ◽  
Christian Feigenwinter ◽  
Etienne Zurbriggen ◽  
Andrea Pitacco ◽  
Roland Vogt
Keyword(s):  
Soil Respiration ◽  
Eddy Covariance ◽  
City Centre ◽  
Urban Vegetation ◽  
Emission Sources ◽  
Flux Dynamics ◽  
Mitigation Potential ◽  
Eddy Covariance Measurements ◽  
Plant Respiration ◽  
The City

<p>Independent, timely and accurate monitoring of urban CO<sub>2</sub> emissions is important to assess the progress towards the Paris Agreement goals, evaluate the mitigation potential of the implemented actions and support urban planning, policy- and decision-making processes. However, there are several challenges towards achieving comprehensive urban emission monitoring at the required scales, which are mainly related to the complexities in the urban form, the urban function and their interactions with the atmosphere. Cities are highly heterogeneous mosaics of CO<sub>2</sub> sources and sinks. Typically, the main emission sources in an urban neighbourhood are vehicles and buildings, while the contribution of human, plant and soil respiration can be also significant depending on population density and green area fraction. At the same time, urban vegetation acts as carbon sink, mitigating urban emissions locally. This study attempts to unravel the complex urban CO<sub>2</sub> flux dynamics by modelling each component separately (i.e. building emissions, traffic emissions, human metabolism, photosynthetic uptake, plant respiration, soil respiration) based on high resolution geospatial, meteorological and population activity datasets. The case study is the city centre of Basel, Switzerland. The models are calibrated and evaluated using Eddy Covariance measurements of CO<sub>2</sub> flux from two permanent tower sites in the city centre, covering a significant part of the study area. Moreover, an extended field campaign for the measurement of the biogenic components (i.e. photosynthetic uptake, plant respiration, soil respiration) has been active since the summer of 2020, involving regular chamber flux measurements and soil stations across the study area. The study reveals the spatial and temporal complexity of the urban CO<sub>2</sub> flux dynamics both diurnally and seasonally. The relative contribution of each flux component to the seasonal cycle is presented, while the mitigation potential of urban vegetation is evaluated. Cross-comparison between model outputs and Eddy Covariance measurements are discussed in respect to source area variability, airflow complexity in the urban canopy layer and irregular unrecognized emission sources.</p>

scholarly journals Feline patent Toxoplasma-like coccidiosis among feral cats (Felis catus) in Doha city, Qatar and its immediate surroundings

2014 ◽  
Vol 59 (3) ◽  
Author(s):  
Marawan Abu-Madi ◽  
Jerzy Behnke
Keyword(s):  
Felis Catus ◽  
City Centre ◽  
Clear Pattern ◽  
Hospital Records ◽  
Feral Cat ◽  
Feral Cats ◽  
North West ◽  
The City ◽  
Annual Period

AbstractDoha city has a high feral cat population and studies of hospital records in Doha have shown that human toxoplasmosis also occurs. Clearly, there is a need to understand the role of cats as vectors of human toxoplasmosis in the city and as a first step we assessed the extent of patent Toxoplasma-like coccidial infections among feral cats. Oocysts in cat faeces were detected between June 2008 and April 2010, from a range of locations radiating out of the city centre in concentric semi circular/elliptic rings and by north, west and south divisions within each of the rings. In total 4,652 cats were sampled and overall prevalence of oocysts was 9.1%. Prevalence was 10.1% in the first summer, and then dropped to 8.4% in the following winter and further to 6.8% in the next summer before rising to 10.6% in the final winter of the study; this interaction between annual period and season was significant. There were also significant changes in prevalence across each of the consecutive months of the study, but no clear pattern was evident. Prevalence did not vary significantly by city sector and there was no difference in prevalence between the host sexes. We conclude therefore, that despite minor and significant perturbations, the prevalence of patent Toxoplasma-like coccidial infections among cats in Doha is remarkably stable throughout the year, across years and spatially within the city’s districts.

scholarly journals Eddy covariance measurements of the net turbulent methane flux in the city centre – results of 2-year campaign in Łódź, Poland

2016 ◽  
Vol 16 (13) ◽  
pp. 8281-8294 ◽  
Author(s):  
Włodzimierz Pawlak ◽  
Krzysztof Fortuniak
Keyword(s):  
Eddy Covariance ◽  
Methane Flux ◽  
Heat Fluxes ◽  
City Centre ◽  
Carbon Dioxide Fluxes ◽  
Surface Exchange ◽  
Eddy Covariance Measurements ◽  
The City ◽  
Comparable Magnitude ◽  
Measurement Period

Abstract. To investigate temporal variability of methane (CH4) fluxes in an urban environment, air–surface exchange fluxes of CH4 were continuously measured using eddy covariance techniques at a city-centre site in Łódź, Poland, from July 2013 to August 2015. In the immediate vicinity of the measurement site, potential methane sources include vehicle traffic, dense sewerage infrastructure and natural gas networks. Sensible and latent heat fluxes have also been measured since 2000 and carbon dioxide fluxes since 2007 at this site. Upward CH4 fluxes dominated during the measurement period, indicating that the city centre is a net source of CH4 to the troposphere. The highest monthly fluxes were observed in winter (2.0 to 2.7 g m−2 month−1) and the lowest in summer (0.8 to 1.0 g m−2 month−1). Fluxes on working days were around 6 % higher than on weekends. The cumulative flux indicates that the city centre emitted a net quantity of nearly 18 g m−2 of CH4 in 2014. Stable values of the FCO2∕ FCH4 ratio in months (minimum 2.41 × 10−3, maximum 5.3 × 10−3) and the lack of a clear annual course suggest comparable magnitude of both fluxes.

Carbon dioxide emissions variability monitoring, based on four years of Eddy Covariance measurements in a typical Mediterranean city

2021 ◽  
Author(s):  
Konstantinos Politakos ◽  
Stavros Stagakis ◽  
Nektarios Chrysoulakis
Keyword(s):  
Time Series ◽  
Eddy Covariance ◽  
Carbon Dioxide Emissions ◽  
Source Area ◽  
Urban Morphology ◽  
City Centre ◽  
Surface Model ◽  
Time Step ◽  
The City ◽  
Mediterranean City

<p>Urban areas around the globe are growing rapidly and as a consequence the anthropogenic effects on the environment are ever-increasing. Understanding the dynamics, procedures and mechanics behind urban greenhouse gas emissions is a challenge for the scientific community. This study investigates the variability of urban CO<sub>2</sub> emissions in the city centre of Heraklion, a typical Mediterranean city in Greece, during a four-year period with gradual changes in the traffic regulations and changes in traffic patterns due to the recent restriction measures imposed to limit the spread of the COVID-19 pandemic. The CO<sub>2</sub> flux (Fc) was measured using the Eddy Covariance (EC) method with a single tower-based system, permanently installed in the centre of the city. Fc was calculated at a 30-min time step and the time-series were quality-controlled and gap-filled using a moving look-up table (mLUT) technique. Fc time series were then aggregated to monthly and yearly emissions totals. Annual flux source area was estimated with the Flux Footprint Prediction (FFP) model, parameterized using measured atmospheric parameters and urban morphological parameters extracted from a Digital Surface Model. The source area was characterized by complex urban morphology and land use types. Specifically, at North of the tower a commercial zone is located, where significantly higher Fc patterns were detected, compared to South, where a residential area dominates. A gradual reduction to CO<sub>2</sub> emissions has been observed since 2016, due to urban planning interventions related to pedestalization of extended areas in the city centre and traffic regulation. During the COVID-19 lockdown period in the Spring of 2020, the diurnal Fc patterns and the monthly aggregated Fc showed significant reductions in the order of 70 % compared to the previous years. Fc values returned to the previous years’ levels with the end of the lock-down in the summer 2020, as it was expected. Finally, during the second lock-down, started in Greece in November 2020, the CO<sub>2</sub> emissions were higher compared to the first lock-down, reflecting a higher level of mobility in Heraklion centre.</p>

A New InscribedKioniskosfrom Thebes

2006 ◽  
Vol 101 ◽  
pp. 369-377 ◽  
Author(s):  
Vassilis L. Aravantinos
Keyword(s):  
Point Of View ◽  
The Other ◽  
City Centre ◽  
North West ◽  
Railway Line ◽  
The North ◽  
The One ◽  
The City ◽  
Roofing System

A fragmentary inscription found at Thebes casts new light on the abortive invasion of Athens in 506 by Kleomenes, the Boiotians, and the Chalkidians. On the one hand, it provides valuable confirmation, soon after the event, of the general drift of Herodotos' account of events; on the other, even in its incomplete state, it adds one important detail lacking in Herodotos. And, of course, it tells the story from the Boiotian point of view.The excavation took place in the winter of the year 2001–2 in the property of Evanghelia Madhis at Thebes following her application for the construction of a new house. The plot is situated in the suburb of Pyri, in the north-west periphery of Thebes, about 800 m from the city centre of Thebes, and just beyond the Athens–Thessaloniki railway line (FIG. 1). In it was unearthed a well-built tomb-like cist, made of three rows of large conglomerate stone blocks in regular masonry; similar blocks form its pavement. No traces of covering stones or other relevant materials have so far been discovered. However, since the contents of the cist—including objects such as the bronze inscribed sheets found at the bottom—were probably thrown there when it was abandoned, it may never have been properly covered: no trace of a superstructure or roofing system is preserved on the upper surface of the walls of the cist.

Restricting Traffic into the City Centre: Has Madrid Central Been Effective to Reduce NO 2 Levels?

2019 ◽  
Author(s):  
Rafael Salas ◽  
María José Pérez Villadóniga ◽  
Juan Prieto Rodríguez ◽  
Ana Russo
Keyword(s):  
City Centre ◽  
The City
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