David Allende

New Approaches for Urban and Regional Air Pollution Modelling and Management

Air pollution is a complex problem that plays a key role in human well-being, environment and climate change. Since cities are, by nature, concentrations of humans, materials and activities, air pollution is clearly a typical phenomenon associated with urban centres and industrialized regions (Fenger, 1999; de Leeuw et al., 2001). Since approximately half the population of the world lives in medium to large cities, it is essential to evaluate the air quality levels of the atmosphere in order to assess the possible health impact from exposition to pollutants (World Health Organization [WHO], 2002; Brunekreef & Holgate, 2002). Additionally, air pollution is not only a human health problem: the effects of pollution in ecosystems and materials are well identified and documented (Fowler et al., 2009); economic costs can also be associated with poor air quality, and with political/governmental measures taken in order to prevent or reduce pollution (Muller & Mendelsohn (2007)). The simplest technique for evaluating patterns of local-scale urban air pollution concentration involves the interpolation of ambient concentrations from existing monitoring networks (Ballesta et al., 2008; Ferretti et al., 2008). However, the measured data from these stations are not necessarily representative of areas beyond their immediate vicinity, since concentrations of pollutants in urban areas may greatly vary on spatial scales that range from tens to hundreds of metres. At the same time, the temporal behaviour of primary and secondary pollutants changes considerably between day and night due to solar radiation, so that daily average measurements become unsatisfactory in determining or explaining high pollution episodes. Air Quality Models (AQMs) are mathematical tools that simulate the physical and chemical processes that involve air pollutant dispersion and reaction in the atmosphere. Furthermore, they improve the limitations of monitoring networks by providing prediction of the temporal and spatial distribution of actual pollution levels. Modelling studies, in combination with air quality monitoring, are then essential and complementary tools for long and short term air pollution control strategies. A well calibrated model is a unique tool that allows the representation of the atmospheric dynamics and chemistry. Thus, AQMs have become a valid instrument for environmental managers in many activities, such as

High resolution satellite derived erodibility factors for WRF/Chem windblown dust simulations in Argentina

A proper representation of dust sources is critical to accurately predict atmospheric particle concentration in regional windblown dust simulations. The Weather Research and Forecasting model with Chemistry (WRF/Chem) includes a topographic-based erodibility map originally conceived for global scale modeling, which fails to identify the geographical location of dust sources in many regions of Argentina. Therefore, this study aims at developing a method to obtain a high-resolution erodibility map suitable for regional or local scale modeling using WRF/Chem. We present two independent approaches based on global methods to estimate soil erodibility using satellite retrievals, i.e. topography from the Shuttle Radar Topography Mission (SRTM) and surface reflectance from the Moderate Resolution Imaging Spectroradiometer (MODIS). Simulation results of a severe Zonda wind episode in the arid central-west Argentina serve as bases for the analysis of these methods. Simulated dust concentration at surface level is compared with particulate matter measurements at one site in Mendoza city. In addition, we use satellite aerosol optical depth (AOD) retrievals to investigate model performance in reproducing spatial distribution of dust emissions. The erodibility map based on surface reflectance from MODIS improves the representation of small scale features, and increases the overall dust aerosol loading with respect to the standard map included by default. Simulated concentrations are in good agreement with measurements as well as satellite derived dust spatial distribution.

Air-quality impact of PM10 emission in urban centres

This paper calculates a detailed inventory of PM10 emissions in the urban area of Mendoza, Argentina, and evaluates the impact of such emissions by using the CALPUFF dispersion program. It includes direct and indirect emissions from mobile sources; emissions from industrial sources and fugitive emissions from unpaved road and dust production from bare land. The main results show the relevance of indirect vehicular particulate emissions owing to resuspension, which contributes 37% of the emissions compared with 21% from exhaust emissions. Heavy-duty diesel freight and bus transport are the main sources for PM10 emissions, despite their low contribution to the fleet composition.

Determination of regional acidification factors for Argentina

PurposeIn the last decade, the use of life cycle assessment (LCA) as a tool for selection between different technologies or products fulfilling the same function has spread rapidly in Latin American countries. However, this accelerated growth in the use of LCA has not always been supported with progress in construction of local inventories or the development of impact assessment methods that consider local and regional characteristics of the sites where technologies, products, and activities or services are being produced or developed. The aim of this study is to propose a local methodology to estimate regional factors for the terrestrial acidification impact category in Argentina based on the critical load exceedance in sensitive areas.Material and methodsAcidification factors for ecological regions in Argentina were calculated following a procedure that compares acidic deposition with critical loads, using a linear function to represent the damage, when the deposition is above the soil buffering capacity. The acidic deposition in the study area was estimated using the air transport model wind trajectory model, with emissions from the global inventory EDGAR. Detailed soil maps were used in order to include the acidification sensitivity of the receiving ecosystems. Also, an application case of the calculated factors is presented in order discuss the relevance of the regional factors implementation in local studies.Results and discussionDeposition fluxes were estimated for different ecoregions in Argentina. The regional factors calculated differ from site-generic factors used commonly to estimate potential impacts, demonstrating that their use in local studies could lead to erroneous outcomes. This was more evident in the application case, where the potential impact calculated was very different, depending on the impact factor used.Conclusions and recommendationsThe model presented in this study allows the assessment of the impact caused by deposition of acidifying substances emitted during the life cycle of a product or process, taking into account the local characteristics where the intervention occurs, and it is the first development of a regional model for acidification within the LCA context carried out in Argentina. The obtained results highlight the importance of developing regional characterization factors for local or regional impacts referred to a definite region.

High-resolution atmospheric emission inventory of the argentine energy sector. Comparison with edgar global emission database

This study presents a 2014 high-resolution spatially disaggregated emission inventory (0.025° × 0.025° horizontal resolution), of the main activities in the energy sector in Argentina. The sub-sectors considered are public generation of electricity, oil refineries, cement production, transport (maritime, air, rail and road), residential and commercial. The following pollutants were included: greenhouse gases (CO2, CH4, N2O), ozone precursors (CO, NOx, VOC) and other specific air quality indicators such as SO2, PM10, and PM2.5. This work could contribute to a better geographical allocation of the pollutant sources through census based population maps. Considering the sources of greenhouse gas emissions, the total amount is 144 Tg CO2eq, from which the transportation sector emits 57.8 Tg (40%); followed by electricity generation, with 40.9 Tg (28%); residential + commercial, with 31.24 Tg (22%); and cement and refinery production, with 14.3 Tg (10%). This inventory shows that 49% of the total emissions occur in rural areas: 31% in rural areas of medium population density, 13% in intermediate urban areas and 7% in densely populated urban areas. However, if emissions are analyzed by extension (per square km), the largest impact is observed in medium and densely populated urban areas, reaching more than 20.3 Gg per square km of greenhouse gases, 297 Mg/km2 of ozone precursors gases and 11.5 Mg/km2 of other air quality emissions. A comparison with the EDGAR global emission database shows that, although the total country emissions are similar for several sub sectors and pollutants, its spatial distribution is not applicable to Argentina. The road and residential transport emissions represented by EDGAR result in an overestimation of emissions in rural areas and an underestimation in urban areas, especially in more densely populated areas. EDGAR underestimates 60 Gg of methane emissions from road transport sector and fugitive emissions from refining activities.