Trends in air quality and population exposure in Santiago, Chile, 1989–2001

This study focused on establishing trends in the period 1988–2001 in PM_2.5, PM₁₀ and ozone concentrations in Santiago, Chile, and linking those to population exposure. There is strong seasonality in the concentration levels, driven by prevailing meteorological conditions, with the concentration of particulates peaking at the beginning of winter, whereas the ozone concentration is highest during the summer. The levels of PM_2.5 and PM₁₀ have substantially decreased since the late 1980s and so has the population exposure. Nevertheless, the majority of the population is still exposed to annual average levels that are above standard values. The situation with ozone exposure is different; no substantial decrease can be observed in the data. If anything, certain parts of Santiago, notably the south-east, have shown increased levels of ozone. Overall population exposure indicates that the average person was more at risk of ozone in the year 2000 than they were in 1993.     

Phenol and nitrophenols in the air and dew waters of Santiago de Chile

Phenol, nitrophenols and dinitrophenols were measured in air and dews in downtown Santiago de Chile. In both systems, phenol, 2-nitrophenol (2-NP), and 4-nitrophenol (4-NP) were the compounds found in higher concentrations and with major frequency. Temporal profiles in air were compatible with a significant direct incorporation from mobile sources. The data can be explained in terms of a faster removal of 2-NP than 4-NP, with the former predominating in fresh air masses and 4-NP in more aged samples. All these compounds, as well as dinitrophenols, were found in dew waters. Simultaneous measurements in air and dew indicate that phenol present in dew exceeds that expected in equilibrated samples, while the opposite occurs with 4-NP. This last result is associated to mass transfer limitations for the highly water soluble nitroderivative.     

Coastal lows and sulfur air pollution in Central Chile

Air pollutants in Santiago (33.5°S, 70.8°W, 500 m a.s.l.), a city with 5 million inhabitants, located in a basin in Central Chile surrounded by the high Andes, frequently exceed air quality standards. This affects human health and it stresses vegetation. The most extreme winter and fall pollution events occur when the subsident regime of the Pacific high is further enhanced by coastal lows (CLs), which bring down the base of the subsidence inversion. Under these conditions, the air quality worsens significantly giving rise to acute air pollution episodes. We assess the ability of a regional transport/chemistry/deposition model (MATCH) coupled to a meteorological model (High Resolution Limited Area Model—HIRLAM) to simulate the evolution of oxidized sulfur (SO_x) in connection with intensive CLs. We focus on SO_x since it is an environmental issue of concern, and the emissions and concentrations of SO_x have been regularly monitored making it easier to bracket model outputs for SO_x than for other pollutants. Furthermore, the SO_x emissions in the area are very large, i.e., about 0.4% of the global anthropogenic sources. Comparisons with observations indicate that the combination of HIRLAM and MATCH is a suitable tool for describing the regional patterns of dispersion associated with CLs. However, the low number and the limited geographical coverage of reliable air quality data preclude a complete evaluation of the model. Nevertheless, we show evidence of an enhanced contribution of the largest copper smelter in the area, i.e., Caletones, to the burden of SO_x in the Santiago basin, especially in the form of sulfate associated to fine particles (diameters <2.5 μm), during CLs. Further, we speculate that the Caletones plume may trigger or promote secondary aerosol formation during CLs in the Santiago basin.     

Volatile carbonylic compounds in downtown Santiago, Chile

Formaldehyde, acetaldehyde, acetone, propanal, butanal, 2-butenal, 3-methylbutanal, hexanal, benzaldehyde, 2-methylbenzaldehyde, and 2,5-dimethylbenzaldehyde were measured during six spring days at downtown Santiago de Chile. Measurements were performed 24h/day and averaged over three hour periods. The averages of the maxima (ppbv) were, formaldehyde: 3.9+/-1.4; butanal: 3.3+/-3.4; acetaldehyde: 3.0+/-0.9; acetone: 2.4+/-1.0; 2-butenal: 0.56+/-0.52; propanal: 0.46+/-0.21; benzaldehyde: 0.34+/-0.3; 3-butanal: 0.11+/-0.05; hexanal: 0.11+/-0.08; 2-methylbenzaldehyde: 0.08+/-0.05; 2,5-dimethylbenzaldehyde: 0.05+/-0.03. Aliphatic aldehydes (C1-C3) are strongly correlated among them and weakly with primary (toluene) and secondary (ozone plus nitrogen dioxide or PAN) pollutants. In particular, the correlation between acetaldehyde and propanal values remains even if diurnal and nocturnal data are considered separately, indicating similar sources. All these aldehydes present maxima values in the morning (9-12h) and minima at night (0-3h). The best correlation is observed when butanal and 2-butenal data are considered (r=0.99, butanal/2-butenal=6.2). These compounds present maxima values during the 3-6h period, with minima values in the 0-3h period. These data imply a strong pre-dawn emission. Other aldehydes show different daily profiles, suggesting unrelated origins. Formaldehyde is the aldehyde whose concentration values best correlate with the levels of oxidants. The contribution of primary emissions and photochemical processes to formaldehyde concentrations were estimated by using a multiple regression. This treatment indicates that (32+/-16)% of measured values arise from direct emissions, while (79+/-23)% is attributable to secondary formation.     

Carbon monoxide concentration forecasting in Santiago, Chile

In the city of Santiago, Chile, air quality is defined in terms of particulate matter with an aerodynamic diameter < or = 10 microm (PM10) concentrations. An air quality forecasting model based on past concentrations of PM10 and meteorological conditions currently is used by the metropolitan agency for the environment, which allows restrictions to emissions to be imposed in advance. This model, however, fails to forecast between 40 and 50% of the days considered to be harmful for the inhabitants every year. Given that a high correlation between particulate matter and carbon monoxide (CO) concentrations is observed at monitoring stations in the city, a model for CO concentration forecasting would be a useful tool to complement information about expected air quality in the city. Here, the results of a neural network-based model aimed to forecast maximum values of the 8-hr moving average of CO concentrations for the next day are presented. Forecasts from the neural network model are compared with those produced with linear regressions. The neural network model seems to leave more room to adjust free parameters with 1-yr data to predict the following year's values. We have worked with 3 yr of data measured at the monitoring station located in the zone with the worst air quality in the city of Santiago, Chile.     

Summertime photochemical ozone formation in Santiago,Chile

The city of Santiago, Chile experiences frequent high pollution episodes and as a consequence very high ozone concentrations, which are associated with health problems including increasing daily mortality and hospital admissions for respiratory illnesses. The development of ozone abatement strategies requires the determination of the potential of each pollutant to produce ozone, taking into account known mechanisms and chemical kinetics in addition to ambient atmospheric conditions. In this study, the photochemical formation of ozone during a summer campaign carried out from March 8–20, 2005 has been investigated using an urban photochemical box model based on the Master Chemical Mechanism (MCMv3.1). The MCM box model has been constrained with 10 min averages of simultaneous measurements of HONO, HCHO, CO, NO, j(O¹D), j(NO₂), 31 volatile organic compounds (VOCs) and meteorological parameters. The O₃–NO_x–VOC sensitivities have been determined by simulating ozone formation at different VOC and NO_x concentrations. Ozone sensitivity analyses showed that photochemical ozone formation is VOC-limited under average summertime conditions in Santiago. The results of the model simulations have been compared with a set of potential empirical indicator relationships including H₂O₂/HNO₃, HCHO/NO_y and O₃/NO_z. The ozone forming potential of each measured VOC has been determined using the MCM box model. The impacts of the above study on possible summertime ozone control strategies in Santiago are discussed.     

Inhalable urban atmospheric particulate matter in a semi-arid climate: The case of Santiago De Chile

The city of Santiago is characterized by low average rainfall and atmospheric thermal inversion layers. Air pollution levels are high. Dichotomous sampling of inhalable particulate matter (IPM) has been conducted at a fixed station on the Universidad de Santiago de Chile (USACH) campus from October 1981 to March 1983. The air sampling inlet cutoff was 15 μm, the fractioning cut being located at a 2.5 μm aerodynamic diameter. The samples were analyzed qualitatively by X-ray fluorescence (XRF) spectrometry. Information on the IPM component of urban air pollution in Santiago by particle sizing sampling methods was not previously available, nor had XRF spectrometry been applied to local IPM samples. A multivariate statistical analysis of the body of data comprising sample masses and XRF elemental intensities is presented and discussed. The group of elements Al, Si, K, Ca, Ti and Fe shows strong statistical correlations in the coarse particle fraction; correlations in the fine particle fraction include Br/Pb. Evidence for seasonal variations in the air pollution pattern is presented. Pollution by sulfur is discussed.     

Responses of herbaceous plants to urban air pollution: Effects on growth, phenology and leaf surface characteristics

Vehicle exhaust emissions are a dominant feature of urban environments and are widely believed to have detrimental effects on plants. The effects of diesel exhaust emissions on 12 herbaceous species were studied with respect to growth, flower development, leaf senescence and leaf surface wax characteristics. A diesel generator was used to produce concentrations of nitrogen oxides (NO_x) representative of urban conditions, in solardome chambers. Annual mean NO_x concentrations ranged from 77 nl l^−l to 98 nl l⁻¹, with NO:NO₂ ratios of 1.4-2.2, providing a good experimental simulation of polluted roadside environments. Pollutant exposure resulted in species-specific changes in growth and phenology, with a consistent trend for accelerated senescence and delayed flowering. Leaf surface characteristics were also affected; contact angle measurements indicated changes in surface wax structure following pollutant exposure. The study demonstrated clearly the potential for realistic levels of vehicle exhaust pollution to have direct adverse effects on urban vegetation.     

Particle size distribution and its relationship to black carbon in two urban and one rural site in Santiago de Chile

The size distribution of particles has been studied in three sites in the Metropolitan area of Santiago de Chile in the winter of 2009 and a comparison with black carbon was performed. Two sites are located near busy streets in Santiago and the other site is located in a rural area about 40 km west of Santiago with little influence from vehicles, but large influence from wood burning. The campaign lasted 1 or 2 weeks in each site. We have divided the particle size measurements into four groups (10–39 nm, 40–62 nm, 63–174 nm, and 175–700 nm) in order to compare with the carbon monitor. In the sites near the street, black carbon has a high correlation (R ? 0.85) with larger particles (175–700 nm). The correlation decreased when black carbon was compared with smaller particles, having very small correlation with the smallest sizes (10–39 nm). In the rural site, black carbon also has a high correlation (R = 0.86) with larger particles (175–700 nm), but the correlation between black carbon and the finest particles (10–39 nm) decreases to near 0. These measurements are an indication that wood burning does not generate particles smaller than ?50 nm. In the urban sites, particle size distribution is peaked toward smaller particles (10–39 nm) only during rush hours, but at other times, particles size distribution is peaked toward larger sizes. When solar radiation was high, evidence of secondary particle formation was seen in the rural site, but not in the urban sites. The correlation between the number of secondary particles and solar radiation was R² = 0.46, indicating that it there may be other variables that play a role in ultrafine particle formation.

Implications:A study of the size distribution of particles and black carbon concentration in two street sites and one rural site shows that in the last site the number of particles ultrafine particles (d < 40 nm) is 10 times lower but the number of larger particles is about 2 times lower. Thus, the rural site has less of the particles that are more dangerous to health. The number of ultrafine particles is mostly associated with traffic, while the number of larger particles is associated with wood burning and other sources. Wood burning does not generate particles smaller than ?50 nm.     

Typical building arrangements for urban air pollution modelling

Typical building arrangements along urban roads and their parameters were determined for three cities in the south-western part of Germany. Some examples of the dispersion of vehicle emissions within idealized street canyons show how different building parameters influence the concentration of air pollutants.     

Statistical distributions for air pollution applied to the study of the particulate problem in Santiago

An expression relating the distribution of concentrations of air pollutants to the emission levels is derived and applied to the study of the air pollution problem of Santiago de Chile. Features specific to the area, like the geography and meteorology are included in a stochastic framework. The resulting distribution is simple. It has two parameters which can be easily estimated from the data. It fits well the data from Santiago and is a powerful tool to analyze pollution data and design a mitigation strategy. The methodology developed here can be applied to any city.     

Total element concentration and chemical fractionation in airborne particulate matter from Santiago,Chile

Total element determination and chemical fractionation were carried out in airborne particulate matter (PM₁₀) from the Cerrillos monitoring station in Santiago, Chile, sampled in July (winter), 1997–2003.Element concentration in the period under study (1997–2003) was statistically analyzed through cluster analysis in order to identify groups of elements having similar behavior along time. Elements such as Cd, Cu, Pb, Ni, As and Mg show a clear decrease in concentration with time. On the contrary, chromium increases its concentration almost linearly during the period.In order to estimate whether the presence of a certain element in PM₁₀ matrix is mainly due to anthropogenic or natural processes, the enrichment factor of each element was determined.According to their behavior in the sequential extraction procedure, the elements were grouped by multivariate analysis in three clusters: (a) those mobile elements (Pb, Cd, Zn, Mn, Cu and As) which are weakly bound to the matrix (fractions 1 and 2) (b) those elements (V, Ti, and Cr) mainly bound to carbonates and oxides (fraction 3) and (c) the most immobile elements (Ni, Mo, Ca, Mg, Ba and Al), mainly bound to silicates and organic matter (fraction 4). A source of great concern is the fact that elements of such high toxicity as Pb, Cd and As are highly concentrated in both mobile fractions, indicating that these elements have a direct impact on the environment and on the health of the exposed population.     

Emission factors for gasoline light-duty vehicles: experimental program in Santiago, Chile

The emission inventory of the city of Santiago, Chile, related to mobile sources was built up using constant emission factors extracted from international literature. To improve the estimate of mobile source emissions, an experimental program was designed, consisting of transient tests on a chassis dynamometer over a sample of about 166 vehicles, applying 9 local driving cycles with average speeds of 3-80 km/hr, and experimentally determined in previous research carried out by the authors. An analysis of the influence of fuel inlet technology, and a year time-length model over emissions, was undertaken. We proposed emission factors as a function of average speed and of CO, THC, and NOx for catalytic and noncatalytic light-duty gasoline vehicles, disaggregated on commercial and private cars. A comparative analysis with emission factors obtained for the application of the COPERT II and AP-42 models was also presented. Our current analysis gives solid evidence indicating that to obtain a reasonable accuracy on emission estimates and calculations, local emission factors must be used.     

Economic impacts of urban air pollution: valuation for Mumbai, India

Urban air pollution is on the rise in many cities of the world. There are associated health impacts that affect urban residents, especially the poor. By doing economic valuation, it is possible to draw the attention of citizens, policy-makers and, of course, researchers to the extent of damage and the value of it. In this paper, such a valuation is done using time-series data for the suburb of Mumbai called Chembur and cross-sectional data for several wards. We value mortality and morbidity from air pollution using the above data. It is shown that the pollution in Mumbai can lead to high health costs. In general the average cost amounts 0.26% of income due to highly subsidised treatment and poverty. However, 5% of patients who suffer severe attacks may pay as much as much as 19% of their income. Workdays lost are of equal importance to health expenditures. Distributional aspects of the damage are such that children and senior citizens are affected most.     

Emission Factors for Gasoline Light-Duty Vehicles: Experimental Program in Santiago,Chile

ABSTRACT

The emission inventory of the city of Santiago, Chile, related to mobile sources was built up using constant emission factors extracted from international literature. To improve the estimate of mobile source emissions, an experimental program was designed, consisting of transient tests on a chassis dynamometer over a sample of about 166 vehicles, applying 9 local driving cycles with average speeds of 3-80 km/hr, and experimentally determined in previous research carried out by the authors. An analysis of the influence of fuel inlet technology, and a year time-length model over emissions, was undertaken. We proposed emission factors as a function of average speed and of CO, THC, and NO_x for catalytic and noncatalytic light-duty gasoline vehicles, disaggregated on commercial and private cars. A comparative analysis with emission factors obtained for the application of the COPERT II and AP-42 models was also presented. Our current analysis gives solid evidence indicating that to obtain a reasonable accuracy on emission estimates and calculations, local emission factors must be used.     

A comparison study of three urban air pollution models

The predictions of three urban air pollution models with varying degrees of mathematical and computational complexities are compared against the hourly SO₂ ground-level concentrations observed on 10 winter nights of the RAPS experiment in St. Louis. The emphasis in this study is on the prediction of urban area source concentrations. Statistics for the paired comparison of predictions of each model with the observations are presented. The RAM and the ATDL model with stable diffusion coefficients overestimated the observed night-time concentrations. The results show that the performance of the ATDL model with near-neutral diffusion coefficients is comparable to the more sophisticated 3-D grid numerical model.