**1. Introduction**

202 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

et CosmochimicaA cta, 48,2469- 2482

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in central Asia. Geochemistry, Geophysics, Geosystems 1(11).1525-2027.

Carboxylic acids together with water-soluble inorganic ions are an important group of water-soluble organic compounds in the atmospheric aerosols (Jacobson et al., 2000, Bourotte et al., 2007). They are highlighted because they account for substantial portion of atmospheric aerosols, and potentially control chemical and physical properties of the particles. Consequently, they may have direct and indirect effects on the earth's radiation balance by scattering incoming solar radiation, which counteracts the global warming (IPCC, 2007). More attention has been paid to carboxylic acids due to their potential to modify the hygroscopic properties of atmospheric particles, including cloud condensation nuclei activity and hence to change global radiation balance (Kerminen, 2001; Peng et al., 2001). Major water-soluble inorganic ions are associated with atmospheric visibility degradation, adverse human health effects, and acidity of precipitation (Dockery & Pope, 1996; IPCC, 2007).

Among the organic acids, low molecular weight carboxylic acids such as acetic, oxalic and malonic are generally most abundant in the atmospheric aerosols. Carboxylic acids in variable concentrations have been reported in various environments including rural and urban atmosphere (Kawamura & Sakaguchi, 1999; Kerminen et al., 2000; Nicolas et al., 2009) and have different source origin, including biomass burning, fossil fuel combustion (Kawamura 1987; Narukawa et al., 1999), sea spray, traffic and industrial emissions and photochemical oxidation of precursors from anthropogenic and biogenic origin (Kawamura & Sakaguchi, 1999; Limbeck & Puxbaum, 1999; Kumar et al., 2001; Chakraborty & Gupta, 2010). Other sources for carboxylic acids in the marine atmosphere include in-cloud and heterogeneous formations (Warneck, 2003).

© 2012 Mkoma et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Mkoma et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Chemical composition of PM2.5 and even that of PM10 aerosols is important to gain insights into sources and of their toxicity and to evaluate effectiveness of abatement strategies for relevant emission sectors. Particulate matter (PM) with aerodynamic diameter less than 2.5 μm (PM2.5) exhibited stronger relation with health than those with aerodynamic diameter less than 10 μm (PM10), but other studies have reported a strong potential of PM10 to human health (Salma et al., 2002; Kappos et al., 2004). Most studies on low molecular weight carboxylic acids and their related compounds (Limbeck et al., 2001; Limon-Sanchez et al., 2002; Kawamura & Yasui, 2005) and major ions (Harrison et al., 2004; Karthikeyan & Balasubramanian, 2006; Mariani et al., 2007; Kundu et al., 2010; Mkoma et al., 2010) have extensively been reported.

Characteristics of Low-Molecular Weight

Carboxylic Acids in PM2.5 and PM10 Ambient Aerosols From Tanzania 205

**Morogoro Dar es Salaam**

MOZAMBIQUE

KENYA

0 100 200km

Zanzibar

5S

INDIAN OCEAN

10S

at 550 °C during 24 h before use. Samplers operated at a flow rate of 17 L/min and were mounted on grass survey at SMC synoptic station approximately 2.7 m above ground level. The sampling was carried out approximately in 24 h intervals and exchange of filters during sampling periods was done at 7:30 am. A total of 11 sets of actual filed samples and 2 blanks were collected for each sampler and used in this chapter. After sampling the exposed filters were folded in half face to face, placed in polyethylene plastic bags and kept frozen at -4 °C during storage and transported cool to the laboratory of research and development in chemistry (LPQ) at the Institute of chemistry, Federal University of Bahia (UFBA). The samples were stored in a freezer at −20 °C prior to analysis. All the procedures were strictly

quality-controlled to avoid any possible contamination of the samples.

**LAKE VICTORIA**

UGANDA

RWANDA

DEM. REP. OF CONGO

5S

10S

BURUNDI

**LAKE TANGANYIKA**

**Figure 1.** Location of the sampling site in Morogoro, Tanzania

ZAMBIA

**2.3. Aerosol analyses** 

During the sampling period meteorological data were collected from the site. The daily winds were predominantly south-easterly with an average speed of 6.8 m/s. Average temperature was 26.8 oC and average relative humidity was 73%. The recorded maximum temperature and relative humidity were 29.8 °C and 79.5%, while minimum values were 23.7 °C and 63.5%,

30E 35E 40E

**LAKE NYASA**

MALAWI

**TANZANIA**

<sup>0</sup> 30E 35E 40E <sup>0</sup>

For particulate mass measurements, the filter samples were weighed before and after sampling with an analytical microbalance balance Mettler Toledo MX5 (reading precision 1 μg). Before weighing, the filters were conditioned in a chamber equipped with hydro-

respectively. During the campaigns 5 days hand rainfall of a total 19.9 mm.

In Africa similar aerosols measurements especially of organic components are missing. Therefore, a full scenario of air quality is far from being revealed because some pollutants including carboxylic acids have not been measured. The knowledge of elucidating chemical composition, levels, and source profiles of aerosols in the Tanzania atmosphere remains a challenge and is needed for both scientific and policy reasons. The continuous changes in socioeconomic and political environments in Tanzania result in changes in development, particularly in transport, industry, energy, and construction sectors. This chapter reports for the first time in Tanzania, composition of low molecular weight carboxylic acids in PM2.5 and PM10 aerosol samples collected from a rural background atmosphere in Morogoro. An insight of characteristics of water-soluble inorganic ions is also discussed in this chapter.
