:: Section 2
Sources of Atmospheric Aerosol
Natural and anthropogenic aerosols have different sources and different magnitudes. Table 1 lists these sources.
| TABLE 1 Sources and Estimates of Global Emissions of Atmospheric Aerosols (Reference: W.C. Hinds, Aerosol Technology, 2nd Edition, Wiley Interscience) |
| Source |
Amount, Tg/yr [106 metric tons/yr] |
Range |
Best Estimate |
| Natural
|
|
|
Soil dust |
1000 - 3000 |
1500 |
Sea salt |
1000 - 10000 |
1300 |
Botanical debris |
26 - 80 |
50 |
Volcanic dust |
4 - 10000 |
30 |
Forest fires |
3 - 150 |
20 |
Gas-to-particle conversion |
100 - 260 |
180 |
Photochemical |
40 - 200 |
60 |
Total for natural sources |
2200 - 24000 |
3100 |
| Anthropogenic
|
|
|
Direct emissions |
50 - 160 |
120 |
Gas-to-particle conversion |
260 - 460 |
330 |
Photochemical |
5 - 25 |
10 |
Total for anthropogenic sources |
320 - 640 |
460 |
The wide range of the estimates given for natural aerosol sources reflects the uncertainty of the assumption upon which these estimates are based. The majority of the particulate mass from soil dust, volcano aerosol emissions, and anthropogenic direct emissions is likely to be large particles that fall out near the source. The other sources produce fine particles that remain suspended for many days, long enough to travel global distances. Among anthropogenic sources, combustion plays a very important role. You can find out later in this module that combustion has significant contribution to direct emissions and gas-to-particle conversion.
 |
Definition |
|
| Gas-to-particle conversion: |
Certain gas phase reactions result in formation of low-vapor-pressure reaction products. Because of their low vapor pressure, they exist at high supersaturations and can form particles. |
 |
Which emission source is larger? Natural or anthropogenic? |
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