**4.2. Metropolitan São Paulo (RMSP)**

In terms of trace species, the composition of the lower troposphere in the conurbation of the RMSP differs considerably from that of the interior of the State and the coastal zone. The critical air quality issue here is the scale of the emissions from road vehicles. In 2001, the vehicle fleet consisted of 17,2% hydrated ethanol-fuelled, 76,3% gasohol-fuelled and 6,5% diesel-fuelled vehicles, with ethanol contributing 34% of the total fuel consumption [31]. The figures for 2011 were 46,7% gasohol (cars and light commercial), 3,9% hydrated ethanol, 31,9% flex-fuel, 5,4% diesel and 12% motorcycles [9].

Review of Aerosol Observations by Lidar and Chemical Analysis in the State of São Paulo, Brazil 287

, SO42-, Ca2+, and Cl-

oil burning (8%) and marine aerosols (14%). Alonso *et al.* [52] used chemical mass balance (CMB) receptor modeling to show that the composition of fine particles was consistent with the presence of primary material from vehicles and secondary organic carbon and sulphate. Road dust re-suspension and vehicle emissions were the main sources of coarse particles and TSP. The same trends in source profiles were observed at geographically distinct locations in São Paulo. Sanchez-Ccoyllo and Andrade [53] used receptor modeling to identify five main sources of aerosols: vehicles, waste incineration, vegetation, suspended

Organic and elemental carbon, emitted mainly from diesel vehicles, together with ammonium sulphate, make up most of the mass of fine particles [54, 55]. In [56] it is reported that 80% of the mass of fine (PM2.5) particles consisted of organic material, with

predominant in coarse particles (PM2.5-10). Albuquerque *et al.* [57] found that fine particles were rich in BC, S and Pb, while elements associated with crustal aerosols and/or industrial emissions (Al, Si, Ca, Ti, and Fe), together with ammonium sulphate and BC, composed the coarse mode particles. Other species, including K, Al, Fe and soil minerals, are included as a smaller component of fine particle mass [46]. Both vehicular and industrial emissions are sources of trace metals (Zn, Pb, Cr, Mn, Cd, etc.) [58, 59], and there appear to be continuing emissions of Pb from the road vehicle fleet, despite

Aerosol composition similar to that of São Paulo is found in other major conurbations. In Campinas, the second largest city in the State, 100 km inland from São Paulo, fine particles were found to consist of 48% elemental carbon and 22% organic carbon, together with

The PM concentrations are influenced not only by the magnitudes of emission sources, but also by ventilation and relative humidity. Miranda and Andrade [54] reported that higher PM10 concentrations (105 g.m-3) measured during the winter of 1999, compared to winter 2000 (60 g.m-3), were due to both better ventilation of the city during the latter period, as well as an increase in particle sizes at higher humidity. Similar findings were reported in [53], with lower pollutant levels associated with increased ventilation, precipitation, and

Primary emissions from vehicles result in large diurnal cycles in the concentrations of PM10, BC, CO, NOx and SO2 [51], however the diurnal trends in particle mass concentrations differ between highly polluted and less polluted periods, with concentrations higher during the daytime for the former, and during the nighttime for the latter [57]. A possible influence of humidity on both the mass and size distribution of the Sao Paulo aerosol was suggested by the observation that while the size distribution of ammonium sulphate was unimodal during the daytime (with a maximum at 0,38 m), at night, when humidity is higher, the size distribution was bimodal (with maxima at 0,38 and 0,59 m) [55]. Furthermore, particle growth, observed using a Scanning Mobility Particle Sizer (SMPS), has been found to

and NH4+ present in the fine fraction, and NO3-

soil dust and fuel oil burning.

apparently low levels of Pb in fuels [60].

soluble ions and trace elements [61].

increase under polluted conditions [57].

relative humidity.

SO42-, NO3-

It is important to consider the relative amounts of the different fuels used, since emissions vary according to fuel, which has consequences for aerosol composition. For example, there is a larger fraction of oxygenated compounds in the secondary aerosols produced from reactions involving the aldehydes and alcohols emitted during ethanol combustion, which can affect the hygroscopicity of the particles, as well as their toxicological properties [48, 49].

The proportions of gasohol (gasoline with 22% anhydrous ethanol) and hydrated ethanol used have varied considerably in recent decades. Ethanol was first adopted as a road vehicle fuel in Brazil in 1979, due to the Brazilian National Alcohol Program (PROALCOOL), which was introduced as a response to the 1970s oil crisis. This not only reduced Brazil's dependency on oil imports, but also helped to eliminate the use of lead-containing antiknock additives [49]. Sales of hydrated ethanol-fuelled vehicles peaked in the 1980s [50]. More recently, since around 2005, the new car market has been dominated by flex-fuel vehicles equipped with engine systems able to adjust to the gasoline/ethanol mixture present in the fuel tank [9].

In 2011, the sources of PM10 in metropolitan São Paulo were: heavy goods vehicles (38,6%), re-suspended dusts (25%), secondary aerosols (25%), industrial processes (10%) and light duty vehicles (1,4%). Annual mean concentrations of PM10 measured at the 18 automatic monitoring stations in São Paulo ranged between 31 and 50 g.m-3 [9]. A detailed analysis of these measurements, as well as of PM2.5, TSP and black smoke measurements made at a smaller number of locations, are provided in the CETESB report [9] and in earlier annual reports published by CETESB.

The pollutant source profile remains fairly constant throughout the year. Use of absolute principal factor analysis showed that the contributions of different sources to PM2.5 mass during winter and summer were: vehicle emissions (28 and 24% for the two seasons, respectively), re-suspended soil dusts (25 and 39%), oil combustion (18 and 21%), sulphates (23 and 17%) and industrial emissions (5 and 6%). Soil dusts accounted for 75-78% of the mass of coarse particles [51]. Andrade *et al.* [14] reported the results of elemental analyses, using particle-induced X-ray emission (PIXE) analysis of fine and coarse aerosols collected in 1989. Principal component analysis revealed the following sources of fine particles: oil and diesel combustion (explaining 41% of the mass), re-suspended soil dusts (18%), industrial emissions (13%), and a source associated with emissions of Cu and Mg (18%). Sources of coarse particles were: re-suspended soil dusts (59%), industrial emissions (19%), oil burning (8%) and marine aerosols (14%). Alonso *et al.* [52] used chemical mass balance (CMB) receptor modeling to show that the composition of fine particles was consistent with the presence of primary material from vehicles and secondary organic carbon and sulphate. Road dust re-suspension and vehicle emissions were the main sources of coarse particles and TSP. The same trends in source profiles were observed at geographically distinct locations in São Paulo. Sanchez-Ccoyllo and Andrade [53] used receptor modeling to identify five main sources of aerosols: vehicles, waste incineration, vegetation, suspended soil dust and fuel oil burning.

286 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

31,9% flex-fuel, 5,4% diesel and 12% motorcycles [9].

In terms of trace species, the composition of the lower troposphere in the conurbation of the RMSP differs considerably from that of the interior of the State and the coastal zone. The critical air quality issue here is the scale of the emissions from road vehicles. In 2001, the vehicle fleet consisted of 17,2% hydrated ethanol-fuelled, 76,3% gasohol-fuelled and 6,5% diesel-fuelled vehicles, with ethanol contributing 34% of the total fuel consumption [31]. The figures for 2011 were 46,7% gasohol (cars and light commercial), 3,9% hydrated ethanol,

It is important to consider the relative amounts of the different fuels used, since emissions vary according to fuel, which has consequences for aerosol composition. For example, there is a larger fraction of oxygenated compounds in the secondary aerosols produced from reactions involving the aldehydes and alcohols emitted during ethanol combustion, which can affect the hygroscopicity of the particles, as well as their toxicological properties [48, 49]. The proportions of gasohol (gasoline with 22% anhydrous ethanol) and hydrated ethanol used have varied considerably in recent decades. Ethanol was first adopted as a road vehicle fuel in Brazil in 1979, due to the Brazilian National Alcohol Program (PROALCOOL), which was introduced as a response to the 1970s oil crisis. This not only reduced Brazil's dependency on oil imports, but also helped to eliminate the use of lead-containing antiknock additives [49]. Sales of hydrated ethanol-fuelled vehicles peaked in the 1980s [50]. More recently, since around 2005, the new car market has been dominated by flex-fuel vehicles equipped with engine systems able to adjust to the gasoline/ethanol mixture

In 2011, the sources of PM10 in metropolitan São Paulo were: heavy goods vehicles (38,6%), re-suspended dusts (25%), secondary aerosols (25%), industrial processes (10%) and light duty vehicles (1,4%). Annual mean concentrations of PM10 measured at the 18 automatic monitoring stations in São Paulo ranged between 31 and 50 g.m-3 [9]. A detailed analysis of these measurements, as well as of PM2.5, TSP and black smoke measurements made at a smaller number of locations, are provided in the CETESB report [9] and in earlier annual

The pollutant source profile remains fairly constant throughout the year. Use of absolute principal factor analysis showed that the contributions of different sources to PM2.5 mass during winter and summer were: vehicle emissions (28 and 24% for the two seasons, respectively), re-suspended soil dusts (25 and 39%), oil combustion (18 and 21%), sulphates (23 and 17%) and industrial emissions (5 and 6%). Soil dusts accounted for 75-78% of the mass of coarse particles [51]. Andrade *et al.* [14] reported the results of elemental analyses, using particle-induced X-ray emission (PIXE) analysis of fine and coarse aerosols collected in 1989. Principal component analysis revealed the following sources of fine particles: oil and diesel combustion (explaining 41% of the mass), re-suspended soil dusts (18%), industrial emissions (13%), and a source associated with emissions of Cu and Mg (18%). Sources of coarse particles were: re-suspended soil dusts (59%), industrial emissions (19%),

**4.2. Metropolitan São Paulo (RMSP)** 

present in the fuel tank [9].

reports published by CETESB.

Organic and elemental carbon, emitted mainly from diesel vehicles, together with ammonium sulphate, make up most of the mass of fine particles [54, 55]. In [56] it is reported that 80% of the mass of fine (PM2.5) particles consisted of organic material, with SO42-, NO3 and NH4+ present in the fine fraction, and NO3- , SO42-, Ca2+, and Clpredominant in coarse particles (PM2.5-10). Albuquerque *et al.* [57] found that fine particles were rich in BC, S and Pb, while elements associated with crustal aerosols and/or industrial emissions (Al, Si, Ca, Ti, and Fe), together with ammonium sulphate and BC, composed the coarse mode particles. Other species, including K, Al, Fe and soil minerals, are included as a smaller component of fine particle mass [46]. Both vehicular and industrial emissions are sources of trace metals (Zn, Pb, Cr, Mn, Cd, etc.) [58, 59], and there appear to be continuing emissions of Pb from the road vehicle fleet, despite apparently low levels of Pb in fuels [60].

Aerosol composition similar to that of São Paulo is found in other major conurbations. In Campinas, the second largest city in the State, 100 km inland from São Paulo, fine particles were found to consist of 48% elemental carbon and 22% organic carbon, together with soluble ions and trace elements [61].

The PM concentrations are influenced not only by the magnitudes of emission sources, but also by ventilation and relative humidity. Miranda and Andrade [54] reported that higher PM10 concentrations (105 g.m-3) measured during the winter of 1999, compared to winter 2000 (60 g.m-3), were due to both better ventilation of the city during the latter period, as well as an increase in particle sizes at higher humidity. Similar findings were reported in [53], with lower pollutant levels associated with increased ventilation, precipitation, and relative humidity.

Primary emissions from vehicles result in large diurnal cycles in the concentrations of PM10, BC, CO, NOx and SO2 [51], however the diurnal trends in particle mass concentrations differ between highly polluted and less polluted periods, with concentrations higher during the daytime for the former, and during the nighttime for the latter [57]. A possible influence of humidity on both the mass and size distribution of the Sao Paulo aerosol was suggested by the observation that while the size distribution of ammonium sulphate was unimodal during the daytime (with a maximum at 0,38 m), at night, when humidity is higher, the size distribution was bimodal (with maxima at 0,38 and 0,59 m) [55]. Furthermore, particle growth, observed using a Scanning Mobility Particle Sizer (SMPS), has been found to increase under polluted conditions [57].

Although local sources are by far the most important contributors to particulate air pollution in São Paulo city, back-trajectory analysis has shown that the atmosphere of the city can also be affected by the advection of air masses from distant regions where agricultural biomass burning is practiced, especially northeast Brazil [62]. This could explain the finding that the relative contribution of ammonium sulphate is higher under less polluted conditions [57].

Review of Aerosol Observations by Lidar and Chemical Analysis in the State of São Paulo, Brazil 289

Due to extreme levels of pollution, air quality in the Cubatão region has been monitored by CETESB since the 1980s, and there are currently three sites where PM10 is continuously measured (Figure 5), and one where TSP is measured [9]. The case of Cubatão is unique, since in contrast to the RMSP, by far the largest source of particulates is industrial emissions, rather than road transport. Guideline levels of TSP and PM10 have been frequently exceeded in the industrial zone (Vila Parisi) of Cubatão, and there has been no improvement in PM10 levels in recent years. During 2011, the annual mean PM10 concentrations in the three zones of Cubatão were 99 g.m-3 (Vila Parisi), 61 g.m-3 (Vila Mogi) and 38 g.m-3 (Centro) [9]. At the industrial Vila Parisi site, the annual geometric mean TSP concentration was 236 g.m-3, greatly exceeding the primary and secondary air quality standards for this pollutant species

Although industrial emissions are responsible for the largest proportion of the aerosol loading of the atmosphere near the Cubatão industrial complex, the organic fraction has an important road transport-related component, because concentrations of polycyclic aromatic hydrocarbons (PAHs) are governed by emissions from heavy duty diesel vehicles [69]. In the same work, it was reported that a shift to greater use of biodiesel might decrease

In regions distant from the industrial installations, the aerosol composition reflects mainly natural sources (biogenic, terrigenous and marine). Bourotte *et al.* [70] found that aerosol (PM10) composition in a State Park in the Cunha region was characterized by an abundance

In 2001, an elastic backscattering lidar system (MSP-Lidar) was installed in a suburban area of São Paulo city, on the Campus of the University of São Paulo (23°33' S, 46°44' W; Figure 6) and is being operated by the *Centro de Lasers e Aplicações* (CLA) of the *Instituto de Pesquisas Energéticas e Nucleares* (IPEN). The lidar is collocated with an AERONET sunphotometer, which provides the vertical profile of the aerosol backscatter coefficient at 532 nm up to an altitude of 4–6 km above sea level [72]. The MSP-Lidar comprises a Nd:YAG laser with a wavelength of 532 nm, and is operated with a repetition rate (PRF) of 20 Hz and an energy pulse of up to 120 mJ. The backscattering signal is captured by a Newtonian telescope with 1,5 m focal length. Attached to the telescope is a photomultiplier optimized for the visible spectrum with a 1 nm FWHM interference filter. Observations are being made whenever atmospheric conditions (absence of low or middle clouds; no rain) permit the operation of the lidar, resulting in a vast amount of data having been accumulated, which have so far

In January 2004, the IPEN MSP-Lidar system was installed for 6 weeks at IPMet in Bauru (Figure 6), located in the central part of São Paulo State, to provide the first measurements of

hydrocarbons emitted from biogenic sources in the coastal region.

been exploited in 5 MSc and 4 PhD theses, the most relevant being [73-76].

and Pb, while Vasconcellos *et al.* [71] reported the presence of aliphatic

(80 and 60 g.m-3, respectively).

emissions of the PAHs.

of K+, Ca2+, Na+, Cl-

**5.1. MSP-Lidar** 

**5. Lidar observations** 

An important consequence of the prevalence of fine mode particles in the atmosphere of the city is that the indoor environment provides little or no protection against exposure to these pollutants, since they easily infiltrate buildings. This was observed [63] using simultaneous indoor and outdoor measurements of a range of ionic species associated with both primary emissions (potassium, magnesium, sodium and calcium) and secondary aerosol formation (chloride, acetate, nitrate, formate, pyruvate, nitrite, sulphate, oxalate and ammonium). The measurements were made in offices, restaurants and a hotel. In the fine mode, only oxalate and ammonium showed significantly lower concentrations indoors. In the coarse mode, lower concentrations were normally found indoors (with the exception of acetate, chloride and potassium), reflecting the less efficient infiltration of larger aerosols.

Polycyclic aromatic hydrocarbons are an important component of the urban aerosols. Chrysene, benzo(e)pyrene and benzo(b)fluoranthene were found to be the predominant PAHs in PM10, originating from industry, vehicles and long-range transport [64]. Levels of PM10 similar to those in São Paulo were measured in a city (Araraquara) situated in the rural biomass burning zone, although here PAH concentrations were lower. In both cases, dry deposition appeared to be the main mechanism of removal of PAH-containing aerosols from the atmosphere [65].

Bourotte *et al.* [66] measured the concentrations of 13 PAHs in fine (PM2.5) and coarse (PM2.5-10) aerosols. In both fractions, the predominant compounds were indeno(1,2,3-cd)pyrene, benzo(ghi)perylene and benzo(b)fluoranthene and PAH ratios suggested that automobile exhaust was the main source of the compounds. Factor analysis revealed four source components for the PM2.5 fraction: diesel emissions, stationary combustion, vehicle emissions, and combustion of natural gas and biomass. For the coarse fraction, two components were identified, corresponding to vehicles and a mixture of gas, oil, and waste combustion.

## **4.3. Coastal regions**

Although measurements of atmospheric aerosol are scarce in most of the coastal regions, an exception is the industrialized town of Cubatão, located near sea level at the base of the Serra do Mar scarp, where there is a large industrial complex comprising over 20 heavy industries (petrochemical, chemical, iron and steel, fertilizer, cement, coking and others). The monitoring stations in this area register regular episodes of particulate pollution, with the emissions from the industrial installations being entrained into a sea breeze circulation, when PM10 concentrations can increase by as much as an order of magnitude [67]. Pollutants absorbed into cloud water and precipitation are subsequently deposited to the vegetation of the Serra do Mar Atlantic rainforest, causing extensive ecological damage [68].

Due to extreme levels of pollution, air quality in the Cubatão region has been monitored by CETESB since the 1980s, and there are currently three sites where PM10 is continuously measured (Figure 5), and one where TSP is measured [9]. The case of Cubatão is unique, since in contrast to the RMSP, by far the largest source of particulates is industrial emissions, rather than road transport. Guideline levels of TSP and PM10 have been frequently exceeded in the industrial zone (Vila Parisi) of Cubatão, and there has been no improvement in PM10 levels in recent years. During 2011, the annual mean PM10 concentrations in the three zones of Cubatão were 99 g.m-3 (Vila Parisi), 61 g.m-3 (Vila Mogi) and 38 g.m-3 (Centro) [9]. At the industrial Vila Parisi site, the annual geometric mean TSP concentration was 236 g.m-3, greatly exceeding the primary and secondary air quality standards for this pollutant species (80 and 60 g.m-3, respectively).

Although industrial emissions are responsible for the largest proportion of the aerosol loading of the atmosphere near the Cubatão industrial complex, the organic fraction has an important road transport-related component, because concentrations of polycyclic aromatic hydrocarbons (PAHs) are governed by emissions from heavy duty diesel vehicles [69]. In the same work, it was reported that a shift to greater use of biodiesel might decrease emissions of the PAHs.

In regions distant from the industrial installations, the aerosol composition reflects mainly natural sources (biogenic, terrigenous and marine). Bourotte *et al.* [70] found that aerosol (PM10) composition in a State Park in the Cunha region was characterized by an abundance of K+, Ca2+, Na+, Cl and Pb, while Vasconcellos *et al.* [71] reported the presence of aliphatic hydrocarbons emitted from biogenic sources in the coastal region.
