Volcanic eruptions particles

Trace elements are delivered to the ocean by atmospheric, or aeolian, processes in both particulate and soluble forms. Most of the aeolian particles entering the ocean are less than 10 pm in size and are referred to as aerosols. Aeolian transport of particles occurs when winds, such as the Trades, pick up small particles from the land s surface and carry them over the ocean. Some trace elements, such as mercury, have a high enough vapor pressure that they are present as atmospheric gases. Still others are ejected during volcanic eruptions in either particulate or gaseous form. 

The composition and sources of particles are discussed in detail in Chapter 9. Major natural sources of particles include terrestrial dust caused by winds, sea spray, biogenic emissions, volcanic eruptions, and wild-... 

However, the eruption of large volcanoes also injects large quantities of S02 into the stratosphere, increasing the concentration of SSA significantly. For example, typical number concentrations of SSA are about 1-10 particles cm-3 under nonvolcanically perturbed conditions the number density increases by 1-2 orders of magnitude after major volcanic eruptions (e.g., see Russell et al., 1996). 

The finding that the heterogeneous chemistry that occurs on polar stratospheric clouds also occurs in and on liquid solutions in the form of liquid aerosol particles and droplets in the atmosphere provided a key link in understanding the effects of volcanic eruptions on stratospheric ozone in both the polar regions and midlatitudes. As discussed herein, the liquid particles formed from volcanic emissions are typically 60-80 wt% H2S04-H20, and hence the chemistry discussed in the previous section can also occur in these particles (Hofmann and Solomon, 1989). We discuss briefly in this section the contribution of volcanic emissions to the chemistry of the stratosphere and to ozone depletion on a global scale. For a brief review of this area, see McCormick et al. (1995). 

Volcanic eruptions can be sufficiently energetic that they inject large quantities of gases and particles directly into the stratosphere (rather than by diffusion from the upper troposphere). The gases include S02, HC1, HF, and SiF4 (Mankin and Coffey, 1984 Symonds et al., 1988 Bekki, 1995 Francis et al., 1995). The particles can include inorganic mineral particles such... 

Figure 12.29 shows the ratio of the particle surface area at an altitude of 20 km and 45°N latitude to that in 1978-1979 for the period from 1979 to 1995 based on satellite measurements (Solomon et al., 1996). The increases due to volcanic eruptions are evident, particularly the Mount Pinatubo eruption. 

Thus, the effect of heterogeneous bromine chemistry is primarily to amplify the chlorine-catalyzed destruction of ozone through the more rapid conversion of the reservoir species HC1 back into active forms of chlorine (Lary et al., 1996 Tie and Brasseur, 1996). This becomes particularly important under conditions of enhanced aerosol particles, e.g., after major volcanic eruptions. 

Volcanic eruptions provide one test of the relationship between light scattering by sulfate particles and the resulting change in temperature, since they generate large concentrations of sulfate aerosol in the lower stratosphere and upper troposphere. These aerosol... 

Second, reaction 8.9 and other relevant reactions appear to occur preferentially on available solid surfaces, which are often ice crystals but may also be particles of sulfate hazes from volcanic eruptions or human activity. Third, volatile bromine compounds are even more effective (via Br atoms) than chlorine sources at destroying ozone methyl bromide is released into the atmosphere naturally by forest fires and the oceans, but anthropogenic sources include the use of organic bromides as soil fumigants (methyl bromide, ethylene dibromide) and bromofluorocarbons as fire extinguishers (halons such as CFsBr, CF2BrCl, and C2F4Br2). 

A hypothetical aerosol size/composition distribution is shown in Figure 12.1, indicating that crustal materials (e.g., COf, Si, Al, Fe, Ca, and Mn), sea spray (e.g., Mg, Na, and Cl), and biogenic organic particles (e.g., pollen, spores, and plant fragments) are usually found in the coarse aerosol fraction (2.5 < r/ae < 10pm) (Meszaros et al., 1997 Krivacsy and Molnar, 1998 Matsumoto et al., 1998 Seinfeld and Pandis, 1998 Maenhaut et al., 2002 Smolik et al., 2003). Wind erosion, primary emissions, mechanical disruption, sea spray, and volcanic eruptions all contribute to the concentrations of these species (Seinfeld, 1986 Seinfeld and Pandis, 1998). 

Nature may be responsible for generating pollutants when natural substances are liberated in amounts that can harm health or cause alterations in ecosystems. This is the case with volcanic eruptions that generate abnormal levels of particles and gases in the atmosphere. Processes such as wind erosion and natural anaerobic processes (involving the production of CO2, CH4, and H2S) may also contribute to abnormal levels of natural substances. Other examples include ... 

The natural mechanisms of atmospheric aerosol generation are as follows soil-wind erosion, ejections to the atmosphere of salt particles from sea and ocean surfaces, emission of gases and vapors by photo-synthesizing plants and by decay products, ejections of the products (soot aerosol, first of all) of natural fires of forests, steppes, peat bogs, and also volcanic eruptions. 

At an early stage it was proved that small particles derived from volcanic eruptions and from sand storms in deserts could be transported... 

Aerosol particles resulting from the 1991 eruption of Mount Pinatubo (Philippines) are widely cited in the recent atmospheric literature because of their global effects on atmospheric radiation and climate (Hansen et al., 1992 McCormick et al., 1995). However, volcanic eruptions occur every year, and some have been far larger than Pinatubo. For comparison, Krakatoa (1883 between Java and Sumatra, Indonesia) and Tambora (1815 Sumbawa, Indonesia), respectively, emitted double and ten times as much pyroclastic debris into the atmosphere as Pinatubo, and significantly reduced sunlight around the globe for months (Sparks et al., 1997). Their effects on the atmosphere have been profound. 

Some natural events also produce noxious gases and particles that can have a major effect on climate. e.g. large volcanic eruptions. When the volcano Tambora (Indonesia) erupted in 1815, the dust cloud in the upper atmosphere kept out sunlight from many places in the world, so that 1816 was known as the year without a summer . 

In the United States it is estimated that more than 15 million tons of particulate matter from anthropogenic sources are emitted into the air each year (9). Natural sources of particulate emissions from windborne dust, volcanic eruptions, and sea spray can contribute more than 10 times this amount. These estimates do not take into consideration the quantity of particles formed through photochemical and other atmospheric reactions however, gas-to-particle reactions are not likely to generate new metal-containing particles. 

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