Info

Free Power Secrets

Making Your Own Fuel

Get Instant Access

h Defined as having lifetimes < 1 day under typical tropospheric conditions.

' Defined as having lifetimes of > 1 day.

h Defined as having lifetimes < 1 day under typical tropospheric conditions.

' Defined as having lifetimes of > 1 day.

Table 2.2 shows one estimate of the global annual organic emissions from biogenic and oceanic sources and biomass burning. Such estimates are highly uncertain because the factors controlling biogenic emissions are complex, leading to large variations with time of day, season, geographical location, etc. (Lamb et al., 1993; Geron et al., 1994; Monson et al., 1995). Illustrative of this is the significant difference in the VOC emission estimates between Tables 2.2 and 2.1. Some sources are not included in these estimates, such as small amounts of isoprene produced by phytoplankton in oceans (e.g., Bonsang et al., 1992; Moore et al., 1994). A biogenics emission inventory for the United States is given by Pierce et al. (1998). The role of biogenic VOC in tropospheric chemistry is discussed in Chapter 6. For a review of VOC in natural and polluted atmospheres, see the book edited by Hewitt (1999).

3. Carbon Monoxide

Carbon monoxide is produced by the incomplete combustion of fossil fuels, and in major urban areas of developed nations a major source is the exhaust from light-duty motor vehicles (LDMV). Figure 2.7 shows the distribution of sources within the United States in 1996. A total of 89 X 106 short tons, or 81 Tg, of CO were emitted, about 60% of which comes from highway vehicles (EPA, 1997).

Natural sources of CO include CO from biomass burning and the oxidation of organics such as methane and isoprene, CO from biological processes in soils, CO from vegetation and termites, and CO from the ocean.

4. Sulfur Compounds

Ninety percent or more of the sulfur in fossil fuels is emitted in the form of sulfur dioxide (S02) during

Non-Road Engines and Vehicles 19%

FIGURE 2.7 Contribution of various sources to the total anthropogenic CO emissions in the United States in 1996 (from EPA, 1997).

Non-Road Engines and Vehicles 19%

FIGURE 2.7 Contribution of various sources to the total anthropogenic CO emissions in the United States in 1996 (from EPA, 1997).

combustion, the remainder being primarily in the form of sulfates. Therefore, its emissions can be calculated for a given source with some accuracy from the rate of fuel consumption and the percentage of sulfur in the fuel. For example, Fig. 2.8 shows the S02 emissions from a number of countries as a function of total fuel consumption (Kato and Akimoto, 1992). Clearly, there is a relatively linear relationship between the two. In the United States in 1996, a total of 19 X 106 short tons, or 17 Tg, of S02 were emitted by anthropogenic sources, with the distribution of sources shown in Fig. 2.9 (EPA, 1997).

Figure 2.10 shows the trend in S02 emissions from North America, Europe, the USSR, and Asia from 1970 to 1986 (Hameed and Dignon, 1992). While S02 emissions from North America have decreased significantly, those from Europe have remained about the same and in the USSR have increased somewhat. However, S02 emissions from Asia have increased dramatically due to the increased combustion of fossil fuels, particularly from the use of coal in China and from biomass burning in Southeast Asia (Arndt et al., 1997). For example, Fig. 2.11 shows the 1987 annual emission fluxes of S02 in Asia, where China is seen to be a major source (Akimoto and Narita, 1994). Emissions from ships are also thought to contribute significantly (e.g., Streets et al., 1997; Corbett and Fishbeck, 1997).

Natural emissions of sulfur compounds to the atmosphere occur from a variety of sources, including volcanic eruptions, sea spray, and a host of biogenic processes (e.g., Aneja, 1990). Most of the volcanic sulfur is emitted as S02, with smaller and highly variable amounts of hydrogen sulfide and dimethyl sulfide (CH3SCH3). Sea spray contains sulfate, some of which is carried over land masses.

Was this article helpful?

0 0
Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

Get My Free Ebook


Post a comment