Evidence of traffic-generated air pollution in Havana

In Havana, transport is blamed as a likely source of pollution issues. which is usually supported on arguments referring to a vehicle fleet mainly made of old cars (i.e., most models are American from the 1950s or Russian from the 1980s) with poor technical conditions. Most of the existing studies are based on measurements from passive samplers collected for 24 h, which may not be representative of conditions where pollutant concentrations (particles or gases) fluctuate or are not homogeneous, such as transport-related pollution. The goal of this paper is to explore the transport-generated pollution by examining short-time correlations between traffic flows, pollutant concentrations and meteorological parameters. To do that, statistical relationships among all variables were analyzed, which revealed that PM10, NO2 and SO2 concentration levels are influenced by vehicular traffic, mainly with low-speed winds blowing perpendicular to the street axis. Furthermore, southeast and northeast winds force drag pollution from sources other than traffic. These conclusions depend on the specific conditions of the summer season at the measurement area. A more complete analysis could be conducted when more data becomes available for each season.

Une première mesure lidar combinée d'ozone et de vent, à partir d'une instrumentation et d'une méthodologie coup par coup

During these last decades, air pollution has drawn the attention of scientists because of the deterioration of the human environment that it has caused. Unfortunately, the study of this dynamic phenomenon is very complex and requires the use of models that compute the evolution of the physico-chemical parameters of the atmosphere. Moreover, the predictions of the numerical simulations have to be validated by range- and time-resolved measurements, carried out continuously up to the top of the planetary boundary layer. Only the optical radar or lidar satisfies these specifications: for this reason the Laboratory for Air and Soil Pollution (LPAS) of the Swiss Federal Institute of Technology (EPFL) has developed such a system in order to provide the modellers with information complementary to that given by the ground measurements. This instrument, after mounting on a mobile platform, has determined the concentration of the key molecule ozone during several field campaigns, demonstrating its reliability and precision. Moreover, the EPFL system is a shot per shot lidar, able to record each detected signal and not only its average in a time interval. This feature is innovative to lidar determinations of tropospheric ozone and allows one to measure accurately the statistical error, to correct for the effect of systematic biases and to observe the dynamic behaviour of the atmosphere: the measurement of the statistical error has been used to build a model of the signal and of its noise, useful in the design of future lidar systems and for the comparison of the various data processing algorithms. the correction of the bias caused by the artificial deformation of the statistical distribution of the signal at long distance has led to a considerable increase of the range of the retrieved ozone profiles, the observation of the dynamic behaviour of the atmosphere has resulted in the first simultaneous measurement of a pollutant concentration and of the wind velocity with the same data set recorded by a lidar.

EPFL1996

Méthodologie pour l'analyse d'une répartition modale et spatiale plus durable du trafic

Raphaëlle Arnaud

There has been a significant growth in freight traffic over the last few decades in Europe. The Alps, located in the middle of North-South route, are particularly sensitive regarding this evolution because of their topographic and climatic characteristics. The more flexible road transport has the advantage of meeting the requirements of contemporary production and distribution techniques, thus helping to explain increasing modal split for road transport. The development of road transport resulted in increased air and noise pollution, congestion, and safety concerns (accidents). The advent of the concept of sustainable development has called current modal split into question. It mainly covers the temporal dimension (equity between generations), but sustainable development also has to take into account the territorial dimension (equity inside the same generation). In this context, the consideration of the interaction between traffic and territory is essential. To assess the vulnerability of crossed areas to traffic and mainly to road and railway transalpine freight traffic, in particular to the nuisances they induce, a method has been developed. The use of a Geographic Information System and the development of an indicator system show the interest of this approach to evaluating the impact induced by a modal and/or spatial split of a volume of transalpine freight traffic (scenarios) on the crossed regions' sustainability. Developed to help decision-makers to take decisions meeting the sustainable development objectives, this method counts for the whole "Alpine segment" (Fréjus – Brenner) and is tested on the Swiss territory. The application on the Swiss territory takes railway and road traffic into account and the noise and air pollutions they induce. The development of indicators is based on immission data (concentrations) and on the spatial distribution of the population. This PhD thesis shows that the establishment of relationships between data coming from various sources is possible, even indispensable, to analyse the effect induced by a modal and/or spatial change of transalpine freight traffic. The results of this research reveal that transalpine freight traffic has a significant impact on the short term. To reduce this impact, it appears to be necessary to act on transalpine freight traffic but also on freight traffic in general. A change in a modal and spatial split of a transalpine freight traffic volume is able to reduce this impact but the situation will still not be satisfying.

EPFL2007

Impact of climate change on runoff pollution in urban environments

David Andrew Barry, Sylvain Coutu, Sébastien Kramer

Runoff from urban environments is generally contaminated. These contaminants mostly originate from road traffic and building envelopes. Facade envelopes generate lead, zinc and even biocides, which are used for facade protection. Road traffic produces particles from tires and brakes. The transport of these pollutants to the environment is controlled by rainfall. The interval, duration and intensity of rainfall events are important as the dynamics of the pollutants are often modeled with non-linear buildup/washoff functions. Buildup occurs during dry weather when pollution accumulates, and is subsequently washed-off at the time of the following rainfall, contaminating surface runoff. Climate predictions include modified rainfall distributions, with changes in both number and intensity of events, even if the expected annual rainfall varies little. Consequently, pollutant concentrations in urban runoff driven by buildup/washoff processes will be affected by these changes in rainfall distributions. We investigated to what extent modifications in future rainfall distributions will impact the concentrations of pollutants present in urban surface runoff. The study used the example of Lausanne, Switzerland (temperate climate zone). Three emission scenarios (time horizon 2090), multiple combinations of RCM/GCM and modifications in rain event frequency were used to simulate future rainfall distributions with various characteristics. Simulated rainfall events were used as inputs for four pairs of buildup/washoff models, in order to compare future pollution concentrations in surface runoff. In this way, uncertainty in model structure was also investigated. Future concentrations were estimated to be between ±40% of today’s concentrations depending on the season and, importantly, on the choice of the RCM/GCM model. Overall, however, the dominant factor was the uncertainty inherent in buildup/washoff models, which dominated over the uncertainty in future rainfall distributions. Consequently, the choice of a proper buildup/washoff model, with calibrated site-specific coefficients, is a major factor in modeling future runoff concentrations from contaminated urban surfaces.

2012