High Contribution of Sea Salt Aerosols on Atmospheric Particles Measured at an Urban Tropical Location in Reunion Island

Chatrapatty Bhugwant, Miloud Bessafi, Olivier Favez, Laura Chiappini, Bruno Sieja, Eva Leoz-Garziandia

Institut National de l’Environnement Industriel et des Risques (INERIS), Verneuil en Halatte, France.
LE2P, University of Réunion Island, Réunion Island, France.
Observatoire Réunionais de l’Air (ORA), Réunion Island, France.

DOI: 10.4236/jep.2013.48097                

Abstract

PM10 was monitored during 2008-2011 period at LUT and BON, two urban tropical stations close to each other at Saint-Pierre city, in Reunion Island (south-western Indian Ocean). During the study period, notable PM10 concentrations are observed at BON close to the coasts. At LUT, a more inland site, the daily PM10 concentration range between 13 and 70 μg/m³. Importantly, the limit value for the protection of the human health is systematically exceeded at BON while it is never exceeded at LUT. Also, the quality objective (QO: 30 μg/m³, on annual average) and the limit value for the human health protection (LV: 40 μg/m³, on annual average) are exceeded at BON each year during 2008-2011, while at LUT no regulatory values are exceeded. Nitrogen dioxide, an atmospheric tracer of anthropogenic activities was also monitored at LUT and BON. The mean diurnal NO₂ variation is of the same level and order of magnitude and exhibits a similar pattern at both stations suggesting that distinct sources influence the PM10 at LUT and at BON. Chemical analysis was performed on daily filters sampled in September-November 2011 at the two stations to determine the sea salt contribution on PM10 across Saint-Pierre city. It showed that the sea salt contribution to the PM10 is 55% at BON in September 2011. The sea salt particles are therefore the main cause for the exceedances of the regulatory values of PM10 recorded at BON. The results importantly suggest that the notable PM10 concentrations measured at this urban marine site might have some but minor impact on human health.

Keywords

PM10; Nitrogen Dioxide; Anthropogenic; Sea Salt Aerosols; Chemical Characterization; Regulatory Values; Human Health; Lung Cancer; Urban; Tropical

1. Introduction

The study of particulate matter is of increasing interest to the scientific community (epidemiologists, researchers…) and to decision makers, in particular to determine the impact of this pollutant on human health [1-3]. It is thus important to conduct the monitoring of this pollutant especially in densely inhabited regions, in order to take adequate measures (e.g. prevent the surrounding population, in particular sensible persons such as children and old ones) if regulatory values are exceeded and also to study its long-term trend and effects. In this sense, since a few decades, decision makers have established regulatory values for the PM10 concentration levels, following the severity of the impact of this pollutant on human health and on the environment [4-6]. European directives, have set air quality standards (limit values, quality objectives) to be achieved for more than a dozen pollutants, among which the PM10 [7].

The European regulations for PM10 (e.g. Decree of 15th February 2002) is based on the following:

• Quality Objective (QO): 30 µg/m³ on annual average;

• Limit values (LV): 90.4% of the daily average must be below 50 µg/m³ (i.e., 35 days of exceedances allowed per calendar year) ;

• Limit values (LV): 40 µg/m³ on annual average.

Importantly, air quality organizations which provide air quality index daily to the population are confronted with the contribution of natural aerosols on particles measurements, especially in marine urban regions, which may in part hamper the air quality index.

Anthropogenic activities such as traffic circulation emit important amounts of particles and gases [8]. Several epidemiological studies indicate that lung cancer and other health effects are possibly associated with atmospheric particles [2,9-14]. In this sense, in June 2012, the International Agency for Research on Cancer (IARC) classified diesel engine exhaust as carcinogenic to humans (Group 1), based on sufficient evidence that this exposure is associated with an increased risk for lung cancer [3].

Natural sources are also a major cause for atmospheric particles [15-18]. In particular, marine aerosols contribute significantly to the global aerosols load and consequently influence the Earth’s radiative budget [19]. Some studies suggest that on coastal regions, sea salt aerosols may notably contribute to the annual mean particulate mass such as PM10 [20-22]. They emit a large amount of halogens, which are highly reactive and thus have a notable impact on the chemistry of hydrocarbons and/or ozone in the atmosphere [23]. Furthermore, sea salt plays an important role in a number of physical and chemical atmospheric processes [24,25]. For example, the reaction of sea salt particles with nitric acid forms sodium nitrate, which may be integrated in the particulate phase of the nitrogen budget [26]. The halogens released by the reaction of acidic gases with sea salt contribute, via heterogeneous reactions, to ozone destruction [27,28]. Sea salt may also indirectly impact vulnerable ecosystems via acid deposition [29,30]. Besides, sea salt aerosols contribute to corrosion of materials (e.g. metals) in coastal regions which cost billions for their rehabilitation [31]. Sea salt aerosols also contribute to cloud condensation nuclei (CCN), especially in marine regions [32,33]. Consequently, sea salt aerosols are essential components of atmospheric constituents at local, regional and global scales [34,35].

A number of studies have been dedicated to the modeling of atmospheric particles in general and sea salt particles in particular [36-38]. Many studies of marine aerosols and their role in the climate system were performed on the global scale [34,39-42]. For air quality assessment on local-to-regional scales, it is important to determine the gradients in sea salt levels and a number of regional models include a large description of sea salt [43-46]. The validation of these models is notably concerned by the limited number of available measurements. However, up to now, few atmospheric measurements have been undertaken with links to mixed sources (e.g. urban and marine aerosols) in particular the southern hemisphere [47-49].

The objective of this study is to quantify the sea salt contribution on the PM10 particles measured at two marine urban locations close to each other. Continuous PM10 measurements and chemical analysis of particles sampled daily on filters to determine the major ions (specific tracers of sea salt aerosols) was undertaken, to establish the distribution of sea salt aerosols on PM10 measured across Saint-Pierre city. These data were analyzed in conjunction with meteorological parameters in order to confirm the air masses origin. Finally, an assessment of the sea salt contribution based on the retrieval of the sea salt contribution on the PM10 measurements is proposed for the recalculation of the air quality index more realistic of anthropogenic activities.

2. Experimental Procedures—Measurement Locations

Réunion Island is a French department located in the South-Western Indian Ocean (21 S; 55 E). This tiny (area: ~2500 km²) and mountainous island (highest point: ~3075 m asl (above sea level)) holds two agglomerations with ~100,000 inhabitants: Saint-Denis, located to the North and Saint-Pierre located to the South of it (see Figure 1). Figure 1(a) is a zoom on Saint-Pierre city illustrating the geographical context of the measurement locations, in particular with respect to the coasts.

Saint-Pierre city is exempt of light/heavy industries susceptible emitting any atmospheric pollution and a significant proportion (~49%) of private cars as well as quite all trucks and buses operate with diesel at Reunion Island [50].

Figure 1(b) shows the configuration of Bons Enfants (BON hereafter) station, highlighting in particular:

• Its position, located about 200 m from the south coast of Reunion Island;

• Its proximity (about 1.5 km) with another urban station Luther King (LUT hereafter), the latter not showing any limit value of PM10 exceeded since 2008 (see Section 4.1.4 here after);

• The two measurement stations are located in the same urban environment, with light traffic circulation and at more than 0.5 to 1 km away from heavy highways. Hence, they are deemed representative of the urban background pollution level linked to anthropogenic activities (mainly traffic circulation);

• The presence of shallow water between the coast and the coral reefs which contributes to an efficient daily sea spray via wind flows and a potential sea salt source over this area. This is not the case for LUT which is downstream the coast too but where there is deep sea water with quite no coral reef and thus much lower sea spray emissions than at BON.

3. Experimental Set-Ups and Measurements

The PM10 and NO₂ (nitrogen dioxide) concentrations

Figure 1. Map of Réunion Island. (a) (Source: Google Earth, 2011) and a zoom on Saint-Pierre agglomeration; (b) With location of Bons Enfants (BON) and Luther King (LUT) stations (Source: ^©IGN-®authorization N˚ 9876).

have been recorded continuously at LUT and BON since August 2007.

The PM10 measurements are subsequently compared with meteorological data. In September 2011, atmospheric samples were also collected on filter on a daily basis for subsequent laboratory analysis in order to characterize the chemical composition of the PM10 particles.

3.1. Atmospheric Sampling Strategy

Figure 2 illustrates BON (upper left) and LUT (upper right) stations implemented at Saint-Pierre since mid- 2007. It may be seen that these two stations have the same characteristics and a similar environment.

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	M. S. O’Neill, D. Loomis, V. M. Torres-Meza, A. Retama and D. Gold, “Estimating Particle Exposure in the Mexico City Metropolitan Area,” Journal of Exposure Analysis and Environmental Epidemiology, Vol. 12, No. 2, 2002, pp. 145-156.
[2]	M. D. Attfield, P. L. Schleiff, J. H. Lubin, A. Blair, P. A. Stewart, R. Vermeulen, J. B. Coble and D. T. Silverman, “The Diesel Exhaust in Miners Study: A Cohort Mortality Study with Emphasis on Lung Cancer,” Journal of the National Cancer Institute, Vol. 104, No. 11, 2011, pp. 869-883. doi:10.1093/jnci/djs035
[3]	IARC (International Agency for Research on Cancer), “Diesel Engine Exhaust Carcinogenic,” Press Release No 213, 2012.
[4]	C. Dir, “Council Directive 1999/30/EC of 22nd April 1999 Relating to Limit Values for Sulphur Dioxide, Nitrogen Dioxide and Oxides of Nitrogen, Particulate Matter and Lead in Ambient Air,” Official Journal of the European Union, L163/41, 1999.
[5]	WHO, “Health Aspects of Air Pollution with Particulate Matter, Ozone and Nitrogen Dioxide,” Report on a WHO Working Group, 2003.
[6]	WHO, “Air Quality Guidelines for Particulate Matter, Ozone, Nitrogen Dioxide and Sulphur Dioxide, Global Update 2005,” Summary of risk Assessment, Geneva, 2006.
[7]	E. Dir, “European Directive 2008/50/EC of the European Parliament and the Council of 21st May 2008 on Ambient Air Quality and Cleaner Air for Europe,” Official Journal of the European Union, L152/1, 2008.
[8]	IPCC (Intergovernmental Panel on Climate Change), S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor and H. L. Miller, “Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change,” Cambridge University Press, Cambridge, 2007.
[9]	R. Bhatia, P. Lopipero and A. H. Smith, “Diesel Exhaust Exposure and Lung Cancer,” Epidemiology, Vol. 9, No. 1, 1998, pp. 84-91. doi:10.1097/00001648-199801000-00017
[10]	EPA, “Fourth External Review Draft of Air Quality Criteria for Particulate Matter,” 2003.
[11]	U. Gehring, J. Heinrich, U. Kramer, V. Grote, M. Hochadel, D. Sugiri, M. Kraft, K. Rauchfuss, H. G. Eberwein and H.-E. Wichmann, “Long-Term Exposure to Ambient Air Pollution and Cardiopulmonary Mortality in Women,” Epidemiology, Vol. 17, No. 5, 2006, pp. 545-551. doi:10.1097/01.ede.0000224541.38258.87
[12]	L. Carbajal-Arroyo, A. Barraza-Villarreal, R. Durand-Pardo, H. Moreno-Macias, R. Espinoza-Lain, P. Chiarella-Ortigosa and I. Romieu, “Impact of Traffic Flow on the Asthma Prevalence among School Children in Lima, Peru,” Journal of Asthma, Vol. 44, No. 3, 2007, pp. 197-202. doi:10.1080/02770900701209756
[13]	C. A. Pope, R. T. Burnett, M. J. Thun, E. E. Calle, D. Krewski, K. Ito and G. D. Thurston, “Lung Cancer, Cardiopulmonary Mortality, and Long-Term Exposure to Fine Particulate Air Pollution,” Journal of the American Medical Association, Vol. 288, No. 9, 2002, pp. 1132-1141.
[14]	C. A. Pope, M. Ezzoti and D. W. Dockery, “Fine Particulate Air Pollution and Life Expectancy in the United States,” The New England Journal of Medicine, Vol. 360, 2009, pp. 376-386. doi:10.1056/NEJMsa0805646
[15]	M. O. Andreae and P. J. Crutzen, “Atmospheric Aerosols: Biogeochemical Sources and Role in Atmospheric Chemistry,” Science, Vol. 276, No. 5315, 1997, pp. 1052-1058. doi:10.1126/science.276.5315.1052
[16]	C. D. O'Dowd, M. H. Smith, I. E. Consterdine and J. A. Lowe, “Marine aerosol, Sea-Salt, and the Marine Sulphur Cycle: A Short Review,” Atmospheric Environment, Vol. 31, No. 1, 1997, pp. 73-80. doi:10.1016/S1352-2310(96)00106-9
[17]	B. J. Finlayson-Pitts, “The Tropospheric Chemistry of Sea-Salt: A Molecular-Level View of the Chemistry of NaCl and NaBr,” Chemical Reviews, Vol. 103, No. 12, 2003, pp. 4801-4822. doi:10.1021/cr020653t
[18]	E. R. Lewis and S. E. Schwartz, “Sea Salt Aerosol Production: Mechanisms, Methods, Measurements, and Models—A Critical Review,” Geophysical Monograph Series, Vol. 152, American Geophysical Union, Washington DC, 2004. doi:10.1029/GM152
[19]	C. D. O’Dowd and G. De Leeuw, “Marine Aerosol Production: A Review of the Current Knowledge,” Philosophical Transactions of the Royal Society A, Vol. 365, No. 1856, 2007, pp. 1753-1774. doi:10.1098/rsta.2007.2043
[20]	N. W. Tindale and P. P. Pease, “Aerosols over the Arabian Sea: Atmospheric Transport Pathways and Concentrations of Dust and Sea Salt,” Deep-Sea Research Part II, Vol. 46, No. 8-9, 1999, pp. 1577-1595. doi:10.1016/S0967-0645(99)00036-3
[21]	J. Putaud, F. Raes, R. VanDingenen, E. Bruggemann, M. Facchini, S. Decesari, S. Fuzzi, R. Gehrig, C. Hueglin, P. Laj, G. Lorbeer, W. Maenhaut, N. Mihalopoulos, K. Mueller, X. Querol, S. Rodriguez, J. Schneider, G. Spindler, H. Ten Brink, K. Torseth and A. Wiedensohler, “European Aerosol Phenomenology-2: Chemical Characteristics of Particulate Matter at Kerbside, Urban, Rural and Background Sites in Europe,” Atmospheric Environment, Vol. 38, No. 16, 2004, pp. 2579-2595. doi:10.1016/j.atmosenv.2004.01.041
[22]	A. M. M. Manders, M. Schaap, X. Querol, M. F. M. A. Albert, J. Vercauteren, T. A. J. Kuhlbusch and R. Hoogerbrugge, “Sea Salt Concentrations across the European Continent,” Atmospheric Environment, Vol. 44, No. 20, 2010, pp. 2434-2442. doi:10.1016/j.atmosenv.2010.03.028
[23]	M. Hess, U. K. Krieger, C. Marcolli, T. Huthwelker, M. Ammann, W. A. Lanford and Th. Peter, “Bromine Enrichment in the Near-Surface Region of Br-Doped NaCl Single Crystals Diagnosed by Rutherford Backscattering Spectrometry,” The Journal of Physical Chemistry A, Vol. 111, No. 20, 2007, pp. 4312-4321. doi:10.1021/jp0674120
[24]	R. C. Easter, S. J. Ghan, Y. Zhang, R. D. Saylor, E. G. Chapman, N. S. Laulainen, H. Abdul-Razzak, H. R. Leung, X. D. Bian and R. A. Zaveri, “MIRAGE: Model Description and Evaluation of Aerosols and Trace Gases,” Journal of Geophysical Research, Vol. 109, No. D20, 2004, Article ID: D20210. doi:10.1029/2004JD004571
[25]	N. Mahowald, J.-F. Lamarque, X. X. Tie and E. Wolff, “Sea Salt Aerosol Response to Climate Change: Last Glacial Maximum, Preindustrial, and Doubled Carbon Dioxide Climates,” Journal of Geophysical Research, Vol. 111, No. D5, 2006, Article ID: D05303. doi:10.1029/2005JD006459
[26]	S. Tamm and M. Schulz, “Open-Ocean Aerosol Composition Obtained during 15 Months on a North Sea Ferry,” Atmospheric Environment, Vol. 37, Suppl. 1, 2003, pp. 133-143. doi:10.1016/S1352-2310(03)00241-3
[27]	E. M. Knipping and D. Dabdub, “Impact of Chlorine Emissions from Sea-Salt Aerosol on Coastal Urban Ozone,” Environmental Science & Technology, Vol. 37, No. 2, 2003, pp. 275-284. doi:10.1021/es025793z
[28]	A. Cohan, W. Chang, M. Carreras-Sospedra and D. Dabdub, “Influence of Sea-Salt Activated Chlorine and Surface-Mediated Renoxification on the Weekend Effect in the South Coast Air Basin of California,” Atmospheric Environment, Vol. 42, No. 13, 2008, pp. 3115-3129. doi:10.1016/j.atmosenv.2007.11.046
[29]	S. C. Pryor and R. J. Barthelmie, “Particle Dry Deposition to Water Surfaces: Processes and Consequences,” Marine Pollution Bulletin, Vol. 41, No. 1-6, 2000, pp. 220-231.
[30]	M. Van Loon, R. Vautard, M. Schaap, R. Bergstrom, B. Bessagnet, J. Brandt, P. Builtjes, J. H. Christensen, J. H. Cuvelier, A. Graf, J. E. Jonson, M. Krol, J. Langner, P. Roberts, L. Rouil, R. Stern, L. Tarrasón, P. Thunis, E. Vignati, L. White and P. Wind, “Evaluation of Long-Term Ozone Simulations from Seven Regional Air Quality Models and Their Ensemble Average,” Atmospheric Environment, Vol. 41, No. 10, 2007, pp. 2083-2097. doi:10.1016/j.atmosenv.2006.10.073
[31]	T. H. Muster and I. S. Cole, “Attachment Efficiencies of Salt Aerosols onto Infrastructure and Implications for Atmospheric Corrosion,” Journal of the Electrochemical Society, Vol. 152, No. 3, 2005, pp. B125-B131. doi:10.1149/1.1859813
[32]	Y. J. Yoon and P. Brimblecombe, “Modelling the Contribution of Sea Salt and Dimethyl Sulfide Derived Aerosol to Marine CCN,” Atmospheric Chemistry and Physics, Vol. 2, No. 1, 2002, pp. 17-30. doi:10.5194/acp-2-17-2002
[33]	V. Vinoj and S. K. Satheesh, “Direct and Indirect Radiative Effects of Sea-Salt Aerosols over Arabian Sea,” Current Science (India), Vol. 86, No. 10, 2004, pp. 1381-1390.
[34]	S. L. Gong, L. A. Bartie, J.-P. Blanchet, “Modeling Sea-Salt Aerosols in the Atmosphere—1. Model Development,” Journal of Geophysical Research, Vol. 102, No. D3, 1997, pp. 3805-3818.
[35]	E. Athanasopoulou, M. Tombrou, S. N. Pandis and A. G. Russell, “The Role of Sea-Salt Emissions and Heterogeneous Chemistry in the Air Quality of Polluted Coastal Areas,” Atmospheric Chemistry and Physics, Vol. 8, No. 19, 2008, pp. 5755-5769. doi:10.5194/acp-8-5755-2008
[36]	B. Finlayson-Pitts and J. N. Pitts Jr., “Chemistry of the Upper and Lower Atmosphere, Theory, Experiments and Applications,” Academic Press, Waltham, 1999.
[37]	H. Hass, M. van Loon, C. Kessler, R. Stern, J. Matthijsen, F. Sauter, Z. Zlatev, J. Langner, V. Foltescu and M. Schaap, “Aerosol Modelling: Results and Intercomparison from European Regional-Scale Modelling Systems,” Special Rep. EUROTRAC-2 ISS, Munchen, 2003.
[38]	B. Bessagnet, A. Hodzic, H. Vautard, M. Beekmann, S. Cheinet, C. Honoré, C. Liousse and L. Rouil, “Aerosol Modeling with CHIMERE: Preliminary Evaluation at the Continental Scale,” Atmospheric Environment, Vol. 38, No. 18, 2004, pp. 2803-2817. doi:10.1016/j.atmosenv.2004.02.034
[39]	S. L. Gong, L. A. Barrie, J.-P. Blanchet, K. von Salzen, U. Lohmann, G. Lesins, L. Spacek, L. M. Zhang, E. Girard, H. Lin, R. Leaitch, H. Leighton, P. Chylek and P. Huang, “Canadian Aerosol Module: A Size-Segregated Simulation of Atmospheric Aerosol Processes for Climate and Air Quality Models 1. Module Development,” Journal of Geophysical Research, Vol. 108, No. D1, 2003, pp. AAC 3-1-AAC 3-16. doi:10.1029/2001JD002002
[40]	W. Guelle, M. Schulz, Y. Balkanski and F. Dentener, “Influence of the Source Formulation on Modeling the Atmospheric Global Distribution of Sea Salt Aerosol,” Journal of Geophysical Research, Vol. 106, No. D21, 2001, pp. 27509-27524. doi:10.1029/2001JD900249
[41]	P. Stier, J. Feichter, S. Kinne, S. Kloster, E. Vignati, J. Wilson, L. Ganzeveld, I. Tegen, M. Werner, Y. Balkanski, M. Schulz, O. Boucher, A. Minikin and A. Petzold, “The Aerosol-Climate Model ECHAM5-HAM,” Atmospheric Chemistry and Physics, Vol. 5, No. 4, 2005, pp. 1125-1156.
[42]	P. Jiménez-Guerrero, O. Jorba, M. T. Pay, J. P. Montávez, S. Jerez, J. J. Gómez-Navarro and J. M. Baldasano, “Comparison of Two Different Sea-Salt Aerosol Schemes as Implemented in Air Quality Models Applied to the Mediterranean Basin,” Atmospheric Chemistry and Physics, Vol. 11, No. 10, 2011, pp. 4833-4850. doi:10.5194/acp-11-4833-2011
[43]	V. L. Foltescu, S. C. Pryor and C. Bennet, “Sea Salt Generation, Dispersion and Removal on the Regional Scale,” Atmospheric Environment, Vol. 39, No. 11, 2005, pp. 2123-2133. doi:10.1016/j.atmosenv.2004.12.030
[44]	B. Langmann, S. Varghese, E. Marmer, E. Vignati, J. Wilson, P. Stier and C. O’Dowd, “Aerosol Distribution over Europe: A Model Evaluation Study with Detailed Aerosol Microphysics,” Atmospheric Chemistry and Physics, Vol. 8, No. 6, 2008, pp. 1591-1607. doi:10.5194/acp-8-1591-2008
[45]	M. Schaap, R. M. A. Timmermans, F. J. Sauter, M. Roemer, G. J. M. Velders, G. A. C. Boersen, J. P. Beck and P. J. H. Builtjes, “The LOTOS-EUROS Model: Description, Validation and Latest Developments,” International Journal of Environment and Pollution, Vol. 32, No. 2, 2008, pp. 270-290. doi:10.1504/IJEP.2008.017106
[46]	A. S. Zakey, F. Giorgi and X. Bi, “Modeling of Sea Salt in a Regional Climate Model: Fluxes and Radiative Forcing,” Journal of Geophysical Research, Vol. 113, No. D14, 2008. doi:10.1029/2007JD009209
[47]	C. Bhugwant, H. Cachier, M. Bessafi and J. Leveau, “Impact of Traffic on Black Carbon Aerosol Concentration at La Reunion Island (Southern Indian Ocean),” Atmospheric Environment, Vol. 34, No. 20, 2000, pp. 3464-3473. doi:10.1016/S1352-2310(99)00405-7
[48]	C. Bhugwant and P. Brémaud, “Simultaneous Measurements of Black Carbon, PM10, Ozone and NOx Variability at a Locally Polluted Island in the Southern Tropics,” Journal of Atmospheric Chemistry, Vol. 39, No. 3, 2001, pp. 261-280. doi:10.1023/A:1010692201459
[49]	C. Bhugwant, M. Bessafi and B. Siéja, “The Potential Impact of Marine Aerosols via the Swell and the Oceanic Waves on the PM10 Concentration Measurements at Urban Marine Locations, Air Pollution Emissions,” Nova Publishers, New York, 2012.
[50]	INSEE, “TER (Tableau Economique de La Réunion),” 2010, p. 3014. in French.
[51]	W. E. Wilson, B. D. Grover, R. W. Long, N. L. Eatough and D. J. Eatough, “The Measurement of Fine-Particulate Semivolatile Material in Urban Aerosols,” Journal of the Air & Waste Management Association, Vol. 56, No. 4, 2006, pp. 384-397. doi:10.1080/10473289.2006.10464527
[52]	B. D. Grover, N. L. Eatough, D. J. Eatough, J. C. Chow, J. G. Watson, J. L. Ambs, M. B. Meyer, P. K. Hopke, R. Al-Horr, D. W. Later and W. E. Wilson, “Measurement of Both Nonvolatile and Semi-Volatile Fractions of Fine Particulate Matter in Fresno, CA,” Aerosol Science and Technology, Vol. 40, No. 10, 2006, pp. 811-826. doi:10.1080/02786820600615071
[53]	J. Wanjura, B. Shaw, C. Parnell, R. Lacey and S. Capareda, “Comparisons of Continuous Monitor (TEOM) and Gravimetric Sampler Particulate Matter Concentrations,” American Society of Agricultural and Biological Engineers, Vol. 51, No. 1, 2008, pp. 251-257.
[54]	C. Bhugwant and J.-L. Hoareau, “Variability of NO2 in Different Environments at a Moderately Polluted Island over the Southwestern Indian Ocean,” Atmospheric Research, Vol. 66, No. 4, 2003, pp. 241-259. doi:10.1016/S0169-8095(03)00038-3
[55]	F. Cavalli, M. Viana, K. E. Yttri, J. Genberg and J.-P. Putaud, “Toward a Standardised Thermal-Optical Protocol for Measuring Atmospheric Organic and Elemental Carbon: The EUSAAR Protocol,” Atmospheric Measurement Techniques, Vol. 3, No. 1, 2010, pp. 79-89. doi:10.5194/amt-3-79-2010
[56]	M. E. Birch and R. A. Cary, “Elemental Carbon-Based Method for Monitoring Occupational Exposures to Particulate Diesel Exhaust,” Aerosol Science and Technology, Vol. 25, No. 3, 1996, pp. 221-241. doi:10.1080/02786829608965393
[57]	O. S. Météo-France, “Atlas Climatique de La Réunion,” Bureau d’étude Climatologique, Direction Interrégionale de La Réunion, Annual Report No. 1657, 2000.
[58]	N. Pérez, J. Pey, M. Cusack, C. Reche, X. Querol, A. Alastuey and M. Viana, “Variability of Particle Number, Black Carbon, and PM10, PM2.5, and PM1 Levels and Speciation: Influence of Road Traffic Emissions on Urban Air Quality,” Aerosol Science and Technology, Vol. 44, No. 7, 2010, pp. 487-499. doi:10.1080/02786821003758286
[59]	M. T. Limon-Sanchez, P. Carbajal-Romero, L. Hernandez-Mena, H. Saldarriaga-Norena, A. Lopez-Lopez, R. Cosio-Ramirez, J. L. Arriaga-Colina and W. Smith, “Black Carbon in PM2.5, Data from Two Urban Sites in Guadalajara, Mexico during 2008,” Atmospheric Pollution Research, Vol. 2, No. 3, 2011, pp. 358-365. doi:10.5094/APR.2011.040
[60]	V. Grondin and C. Bhugwant, “Internship Report, ORA, Etude de l’Impact des Embruns Marins Sur la Qualité de l’Air en Milieu Urbain à la Réunion,” 2008, in French.
[61]	B. J. Turpin, P. Saxena and E. Andrews, “Measuring and Simulating Particle Organics in the Atmosphere: Problems and Prospects,” Atmospheric Environment, Vol. 34, No. 18, 2000, pp. 2983-3013. doi:10.1016/S1352-2310(99)00501-4
[62]	J. C. Cabada, S. N. Pandis, R. Subramanian, A. L. Robinson, A. Polidori and B. Turpin, “Estimating the Secondary Organic Aerosol Contribution to PM2.5 Using the EC Tracer Method Special Issue of Aerosol Science and Technology on Findings from the Fine Particulate Matter Super Sites Program,” Aerosol Science and Technology, Vol. 38, Suppl. 1, 2004, pp. 140-155. doi:10.1080/02786820390229084
[63]	E. Friese and A. Ebel, “Temperature Dependent Thermodynamic Model of the System H+-NH4+-Na+-SO42--NO3--Cl--H2O,” Journal of Physical Chemistry A, Vol. 114, No. 43, 2010, pp. 11595-11631. doi:10.1021/jp101041j