scholarly journals Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

2006 ◽  
Vol 6 (1) ◽  
pp. 549-578 ◽  
Author(s):  
A. Virtanen ◽  
T. Rönkkö ◽  
J. Kannosto ◽  
J. M. Mäkelä ◽  
J. Keskinen ◽  
...  
Keyword(s):  
Particle Distribution ◽  
Total Concentration ◽  
Average Density ◽  
Size Distributions ◽  
Nucleation Mode ◽  
The Road ◽  
Mode 2 ◽  
Traffic Rate ◽  
Winter Time ◽  
Summer Time

Abstract. The number concentration and size distribution of traffic related particles were measured at road-side in Helsinki. Two winter campaigns took place in 10–26 February 2003 and 28 January–12 February 2004 and two summer campaigns in 12–27 August 2003 and 6–20 August 2004. The measurements were performed simultaneously at distances of 9 m and 65 m from the highway. This study concentrates on data that were measured when the wind direction was from the road to the measurement site. The total concentration in winter time was 2–3 times higher than in summer time and it was dominated by nucleation mode particles. The particles smaller than 63 nm (at aerodynamic size) constitute ~90% of all particles in winter time and ~80% of particles in summer time. The particle total concentration increases with increasing traffic rate. The dependence of particles smaller than 63 nm on traffic rate is stronger than for particles larger than 63 nm both during summer and winter. The particle distribution at the roadside consists of two distinguishable modes. The GMD of nucleation mode (Mode 1) was 20.3 nm at summer and 18.9 nm at winter. The GMD of the larger mode (Mode 2) was 72.0 nm at summer and 75.1 nm at winter. The GMD values of the modes do not depend on traffic rate. The average density value for Mode 1 particles was 1.0 g/cm3 both in summer and winter time, while the average density value for Mode 2 was 1.5±0.1 g/cm3 and 1.8±0.3 g/cm3 for summer and winter time, respectively.

scholarly journals Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

2006 ◽  
Vol 6 (9) ◽  
pp. 2411-2421 ◽  
Author(s):  
A. Virtanen ◽  
T. Rönkkö ◽  
J. Kannosto ◽  
J. Ristimäki ◽  
J. M. Mäkelä ◽  
...  
Keyword(s):  
Particle Density ◽  
Aerosol Particles ◽  
Geometric Mean ◽  
Average Density ◽  
Average Particle ◽  
Size Distributions ◽  
Nucleation Mode ◽  
Mode 2 ◽  
Traffic Rate ◽  
Summer Time

Abstract. Number concentrations and size distributions of traffic related aerosol particles were measured at a roadside in Helsinki during two winter campaigns (10–26 February 2003, 28 January–12 February 2004) and two summer campaigns (12–27 August 2003, 6–20 August 2004). The measurements were performed simultaneously at distances of 9 m and 65 m from the highway. Total number concentrations were measured by a condensation particle counter (CPC) and particle size distributions by a scanning mobility particle sizer (SMPS) and an electrical low pressure impactor (ELPI). This study concentrates on data that were measured when the wind direction was from the road to the measurement site. The total concentrations in the wintertime were 2–3 times higher than in the summertime and the concentrations were dominated by nucleation mode particles. The particles smaller than 63 nm (aerodynamic diameter) constituted ~90% of all particles in the wintertime and ~80% of particles in the summer time. The particle total concentration increased with increasing traffic rate. The effect of traffic rate on particles smaller than 63 nm was stronger than on the larger particles. The particle distributions at the roadside consisted of two distinguishable modes. The geometric mean diameter (GMD) of nucleation mode (Mode 1) was 20.3 nm in summer and 18.9 nm in winter. The GMD of the larger mode consisting mostly of traffic related soot particles (Mode 2) was 72.0 nm in summer and 75.1 nm in winter. The GMD values of the modes did not depend on the traffic rate. The average particle density for each mode was determined by a parallel density fitting method based on the size distribution measurement made by ELPI and SMPS. The average density value for Mode 1 particles was 1.0±0.13 g/cm3 and 1.0±0.07 g/cm3 both in summer and winter respectively, while the average density value for Mode 2 was 1.5±0.1 g/cm3 and 1.8±0.3 g/cm3 for summer and winter, respectively.

scholarly journals Assessment model of levels for winter road maintenance

2017 ◽  
Vol 12 (2) ◽  
pp. 127-134 ◽  
Author(s):  
Tomas Ratkevičius ◽  
Alfredas Laurinavičius
Keyword(s):  
Traffic Accidents ◽  
Assessment Model ◽  
Road Maintenance ◽  
The Road ◽  
Road Users ◽  
Foreign Countries ◽  
Winter Road ◽  
Winter Time ◽  
National Significance ◽  
Winter Road Maintenance

The limited funding for the road industry leads to economizing in the planning of road network maintenance, to identifying the appropriate priorities of the activities with the greatest benefit for the society. The level of maintenance is the direct assessment of the road operation and maintenance service provided to the road users; it directly affects the road maintenance and for road users costs the better is road maintenance, the road users incur the fewerexpenses and vice versa. Insufficient road maintenance in the winter time causes not only the danger of traffic accidents but also worsens the driving conditions, increases the fuel consumption, vehicle depreciation, transportation becomes more expensive. Many results of studies showed that the current choice of maintenance levels in the winter time taking into account only the road category and traffic volume does not ensure the indicators of the most advanced world countries and road functional purpose. The principle of the minimal expenses for the society should be the main criterion in identifying the optimal levels of winter road maintenance. The experience of Lithuania and foreign countries helped in creating the model of assessment of winter maintenance levels for Lithuanian roads of national significance, which can be applied in the other foreign countries as well. This model could be an effective tool for the selection of the optimal maintenance levels, which would economically substantiate the winter road maintenance strategy, that best corresponds to the needs of the society.

scholarly journals Iodine speciation and size distribution in ambient aerosols at a coastal new particle formation hotspot in China

2019 ◽  
Vol 19 (6) ◽  
pp. 4025-4039 ◽  
Author(s):  
Huan Yu ◽  
Lili Ren ◽  
Xiangpeng Huang ◽  
Mingjie Xie ◽  
Jun He ◽  
...  
Keyword(s):  
Particle Formation ◽  
Coastal Areas ◽  
Aerosol Sample ◽  
Size Distributions ◽  
New Particle Formation ◽  
Nucleation Mode ◽  
Iodine Species ◽  
Organic Iodine ◽  
Iodine Compounds ◽  
Iodine Speciation

Abstract. Intense new particle formation (NPF) events were observed in the coastal atmosphere during algae growth and farming season at Xiangshan gulf of the east China coast. High nucleation-mode iodine concentrations measured by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) confirmed that the NPF events were induced by iodine species. Our study provides important information on iodine speciation, size distributions, and its role in NPF in the context of heavy air pollution in China's coastal areas. For the first time, we identified 5 inorganic iodine species, 45 organic iodine compounds (35 molecular formulas), and a group of iodide–organic adducts in aerosols. The concentrations and size distributions of iodine species down to 10 nm were measured during the iodine-induced NPF, continental NPF, and non-NPF days at the coastal site and compared to those at an inland site. The iodine in the above four aerosol sample types were characterized by iodate, aromatic iodine compounds, iodoacetic acid or iodopropenoic acid, and iodide–organic adducts, respectively. Iodide and organic iodine compounds were found in the nucleation-mode particles; however, it is still not clear whether they contributed to nucleation or just new particle growth. Wild algae, as well as farmed algae, could be an important NPF source in China's coastal areas.

Annual re-habituation of calving caribou to oilfields in northern Alaska: implications for expanding development

2008 ◽  
Vol 86 (7) ◽  
pp. 627-637 ◽  
Author(s):  
Shawn P. Haskell ◽  
Warren B. Ballard
Keyword(s):  
Rangifer Tarandus ◽  
Weight Of Evidence ◽  
The Road ◽  
Tolerance Response ◽  
Traffic Rate ◽  
Post Hoc ◽  
Northern Alaska ◽  
Spring Snowmelt ◽  
Road System ◽  
Response Variables

Previous research led to hypotheses that calving caribou ( Rangifer tarandus granti J.A. Allen, 1902) in north Alaskan oilfields habituated to human activities: (i) across years and (ii) annually after spring migration (i.e., re-habituation). We used predictor variables of year and a spring snowmelt index to evaluate weight of evidence for these competing hypotheses. Response variables were calf percentage and sighting rate of calving caribou along a high-traffic road system from 1982 to 1990 and 2000 to 2002. We also considered local calf percentage and caribou density, determined by aerial surveys, for respective response variables. We found no evidence of habituation across years. We found two more lines of evidence (one strong and one weaker) for re-habituation within years during calving periods. Post hoc models suggested a further tolerance response exhibited by caribou; more data are needed. Even when snow melted early and calving caribou were most habituated among years, caribou and calves were under-represented near the road system. Investigation of a traffic-rate effect seems warranted. However, habitat selection and forage availability should be considered when interpreting avoidance behaviour at a larger spatial extent. We contend that the behavioural adaptability of calving caribou exhibited in existing oilfields was contingent on the no-hunt policy.

Characterization of Particle Size, Number, and Mass Emissions From a Diesel Powered Generator

2006 ◽  
Author(s):  
Imad A. Khalek
Keyword(s):  
Particle Size ◽  
Solid Particle ◽  
Particle Distribution ◽  
Size Range ◽  
Number Concentration ◽  
Solid Particles ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Engine Operation ◽  
Size Number

Total (volatile plus solid) and solid particle size, number, and mass emitted from a 3.8 kW diesel powered generator were characterized using a Scanning Mobility Particle Sizer (SMPS) that measures the size distribution of particles, and a catalytic stripper that facilitates the measurement of solid particles. The engine was operated at a constant speed for six steady-state engine operations ranging from idle to rated power. The solid particle size distributions were mainly monomodal lognormal distributions in nature reflecting a typical soot agglomerate size distribution with a number mean diameter in the size range from 98 nm to 37 nm as the load decreases from high to low. At idle, M6, however, the solid particle distribution was bimodal in nature with a high number of solid nanoparticles in the sub-20 nm size range. It is likely that these solid particles nucleated later in the combustion process from metallic ash typically present in the lube oil. The total particle size distributions exhibited a bimodal structure only at light load, M5, engine operation, where a high number of volatile nanoparticles were observed. The rest of the operating conditions exhibited monomodal distributions although the nature of the particles was vastly different. For the medium load modes, M2, M3, and M4, the particles were mainly solid particles. For the rated power, M1, and idle, M6, modes of engine operation, significant number of volatile particles grew to a size nearing that of soot particles making the distribution monomodal, similar to that of a solid particle distribution. This shows that monomodal distributions are not necessarily solid particle but they can be strongly dominated with volatile particles if significant particle growth takes place like the case at M1, and M6. The total number and mass concentration were extremely high at engine rated power. The number concentration exceeded 1.2 billion particles per cubic centimeter and the mass exceeded 750 milligrams per cubic meter. The number concentration is more than five orders of magnitude higher than a typical ambient level concentration, and the mass concentration is more than four orders of magnitude higher. It is important to indicate, however, that if the engine power rating is lowered by 35 percent from its designated level, both particle mass and number emissions will be reduced by two orders of magnitude. By measuring total and solid particle size and number concentration of particles, one can calculate other metrics such as surface area and mass to provide detail information about particle emissions. Such information can serve as an important database where all metrics of particle emissions are captured.

scholarly journals Fast time response measurements of particle size distributions in the 3–60 nm size range with the nucleation mode aerosol size spectrometer

2018 ◽  
Vol 11 (6) ◽  
pp. 3491-3509 ◽  
Author(s):  
Christina Williamson ◽  
Agnieszka Kupc ◽  
James Wilson ◽  
David W. Gesler ◽  
J. Michael Reeves ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Cloud Condensation Nuclei ◽  
Radiation Budget ◽  
Fast Time ◽  
Size Distributions ◽  
Free Troposphere ◽  
Particle Size Distributions ◽  
Nucleation Mode ◽  
Data Inversion

Abstract. Earth's radiation budget is affected by new particle formation (NPF) and the growth of these nanometre-scale particles to larger sizes where they can directly scatter light or act as cloud condensation nuclei (CCN). Large uncertainties remain in the magnitude and spatiotemporal distribution of nucleation (less than 10 nm diameter) and Aitken (10–60 nm diameter) mode particles. Acquiring size-distribution measurements of these particles over large regions of the free troposphere is most easily accomplished with research aircraft. We report on the design and performance of an airborne instrument, the nucleation mode aerosol size spectrometer (NMASS), which provides size-selected aerosol concentration measurements that can be differenced to identify aerosol properties and processes or inverted to obtain a full size distribution between 3 and 60 nm. By maintaining constant downstream pressure the instrument operates reliably over a large range of ambient pressures and during rapid changes in altitude, making it ideal for aircraft measurements from the boundary layer to the stratosphere. We describe the modifications, operating principles, extensive calibrations, and laboratory and in-flight performance of two NMASS instruments operated in parallel as a 10-channel battery of condensation particle counters (CPCs) in the NASA Atmospheric Tomography Mission (ATom) to investigate NPF and growth to cloud-active sizes in the remote free troposphere. An inversion technique to obtain size distributions from the discrete concentrations of each NMASS channel is described and evaluated. Concentrations measured by the two NMASS instruments flying in parallel are self-consistent and also consistent with measurements made with an optical particle counter. Extensive laboratory calibrations with a range of particle sizes and compositions show repeatability of the response function of the instrument to within 5–8 % and no sensitivity in sizing performance to particle composition. Particle number, surface area, and volume concentrations from the data inversion are determined to better than 20 % for typical particle size distributions. The excellent performance of the NMASS systems provides a strong analytical foundation to explore NPF around the globe in the ATom dataset.

Measured particle size distributions during winter time in Eastern Lappland

1992 ◽  
Vol 23 ◽  
pp. 995-998
Author(s):  
Pasi Aalto ◽  
Jyrki M. Mäkelä ◽  
Markku Kulmala ◽  
Pertti Hari
Keyword(s):  
Particle Size ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Winter Time ◽  
Measured Particle

scholarly journals The spatial variability of vehicle densities as determinant of urban network capacity

2010 ◽  
Vol 368 (1928) ◽  
pp. 4627-4647 ◽  
Author(s):  
Amin Mazloumian ◽  
Nikolas Geroliminis ◽  
Dirk Helbing
Keyword(s):  
Fluid Dynamic ◽  
Analytical Formula ◽  
Network Capacity ◽  
Average Density ◽  
Urban Traffic ◽  
Flow Measurements ◽  
Urban Network ◽  
The Road ◽  
Simple Simulation ◽  
Traffic Performance

Due to the complexity of the traffic flow dynamics in urban road networks, most quantitative descriptions of city traffic so far have been based on computer simulations. This contribution pursues a macroscopic (fluid-dynamic) simulation approach, which facilitates a simple simulation of congestion spreading in cities. First, we show that a quantization of the macroscopic turning flows into units of single vehicles is necessary to obtain realistic fluctuations in the traffic variables, and how this can be implemented in a fluid-dynamic model. Then, we propose a new method to simulate destination flows without the requirement of individual route assignments. Combining both methods allows us to study a variety of different simulation scenarios. These reveal fundamental relationships between the average flow, the average density and the variability of the vehicle densities. Considering the inhomogeneity of traffic as an independent variable can eliminate the scattering of congested flow measurements. The variability also turns out to be a key variable of urban traffic performance. Our results can be explained through the number of full links of the road network, and approximated by a simple analytical formula.

CELLULAR AUTOMATON MODELS FOR MIXED TRAFFIC FLOW CONSIDERING PASSAGE WAY OF EMERGENCY VEHICLE

2013 ◽  
Vol 27 (08) ◽  
pp. 1350052 ◽  
Author(s):  
HAN-TAO ZHAO ◽  
HONG-YAN MAO ◽  
RUI-JIN HUANG
Keyword(s):  
Cellular Automaton ◽  
Traffic Flow ◽  
Average Density ◽  
Vehicle Speed ◽  
Emergency Vehicle ◽  
Mixed Traffic ◽  
Mixed Traffic Flow ◽  
The Road ◽  
Emergency Vehicles ◽  
Computer Numerical Simulation

Two kinds of cellular automaton models are proposed for mixed traffic flow with emphasis on emergency vehicles. By analyzing the characteristics of ordinary vehicles in giving way to emergency vehicles, the rules for changing lanes are modified. Computer numerical simulation results indicate that an emergency vehicle without changing lanes can enhance speed with density lower than 0.1, while its speed can be enhanced by changing lane with density greater than 0.1. Meanwhile, vehicle speed and density within a certain range around emergency vehicles are lower than the road section average velocity and average density. The passage way of emergency vehicle that facilitate lane change causes less interference than that of an emergency vehicle which is unable to change lane. The study found that the physical characteristics of traffic flow when there are emergency vehicles are significantly different from routine traffic flow. Emergency vehicles can facilitate their passage by changing lanes at a medium or high density.

AN ADAPTIVE EBCA MODEL PROBING THE PROBLEM OF RIDING AGAINST THE TRAFFIC FLOW

2011 ◽  
Vol 22 (02) ◽  
pp. 191-208 ◽  
Author(s):  
TAO WANG ◽  
JUN-FENG WANG
Keyword(s):  
Phase Transition ◽  
Average Density ◽  
Deterministic Case ◽  
Average Flow Rate ◽  
Traffic System ◽  
The Road ◽  
Wrong Direction ◽  
Stochastic Case ◽  
The Right ◽  
Good Agreement

Despite the rule that cyclists must ride on the right half of the road is written into the state vehicle code, the phenomenon of riding against the bicycle flow is still serious. To investigate the effect of bicycles going in the wrong direction, a Bi-Directional Adaptive EBCA model is developed in this paper. The phase transition F-J as well as the phase transition F-S-F are suggested by observing the spatial-temporal pattern. The deterministic case that the linear relationship between the average flow rate and the bicycle number disappears when the average density exceeds a particular value is shown. Under the stochastic case, the impacts of the avoiding probability Ps and the returning probability Pr on the traffic system are analyzed. The results of the simulation are in good agreement with the realistic bicycle flow.

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