Global Source Estimates

Because of the uniform CO/CO2 ratios reported, we can give a reasonable indication of the magnitude of the CO emissions. 

The same may apply to CH4 and H2. It is clear, however, that any estimations are much less reliable for NOx, N2O, COS and CH3CI. However, we can still indicate the potential importance of biomass burning as a source of these gases to the atmosphere. 

With a relative H2/CO2 emission ratio of 3.3 %, the production of H2 would amount to 15 x 10 g H2 year , with an estimated range of 9-21 x 10 g H2 year . Schmidt [21] estimated the total worldwide source of H2 to be 36.5 x 10 g year , including an anthropogenic contribution of 25.5 x 10 g year. Although our analysis shows that fires are probably important no such contribution was considered in his budget. 

As explained above, the derivation of global source estimates for N2O, NOx, COS and CH3CI is not trivial. The resulting fluxes which we will derive for these gases are, therefore, less reliable than those derived for CO, H2 and CH4. The simplest way of estimating the flux would be to apply the same procedure as for CO, H2 and CH4. With an approximate N2O/CO2 emission factor of 0.22 %, the estimated nitrous oxide source would be 20 x 10 g N2O year . Similar calcu- 

The indicated emissions of NO and N2O both seem very important from a 

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Hydrocarbons are known to be released from anthropogenic sources, from vegetation and soils, and from the oceans. Duce et al. (1983) have reviewed available emission rates. These refer almost entirely to bulk emissions and not to individual compounds, because information on the distribution of hydrocarbons being emitted is in many cases incomplete. Ehhalt et al. (1986) have prepared a more detailed global source estimate for the C2-C5 hydrocarbons. Source distributions for the light hydrocarbons are now reasonably well known. The following presentation includes information on source distributions as far as possible. 

Michard, G., C. Fouillac, D. Grimaud and J. Denis, 1981, Une methode globale d estimation des temperatures des reservoirs alimentant les sources thermales, exemple du Massif Centrale Franqais. Geochimica Cosmochimica Acta 45, 1199-1207. 

This value characterizes the upper level of relative scattering of estimated elements concentration in all the considered snow samples, which is associated both with estimation errors in groups 1-3 and natural variation of the elements abundance in samples. Thus, the results of successive testing of ypotheses Ht -H3 allow us to conclude that the basic hypothesis Hb is true and only global source of chemical contamination exists on the territory of Karabash. 

TABLE 2.1 Global Emission Estimates for CO, NOx, CH4, and VOC from Both Anthropogenic and Natural Sources (in Tg/yr)u... 

The atmospheric deposition rate in this midcontinental area, which has increased by a factor of about 3.7, suggests that natural Hg concentrations were only about 25% of modern levels. Current estimates of recent increases in global atmospheric Hg support this conclusion, and indicate that increased anthropogenic Hg emissions, rather than enhanced removal by atmospheric oxidants, are responsible for elevated Hg deposition. Moreover, the increase appears to be relatively uniform across our study area, implying regional if not global sources for the Hg falling on these remote sites. 

Biomass combustion is a major global source and may even be the major source of atmospheric CH3C1 (223, 282-288). These studies indicate that CH3C1 production is maximized in low intensity fires, from incomplete combustion, and by increased chloride concentration. It is estimated that six billion tons of biomass are consumed... 

Meybeck, in a recent (1987) comprehensive article on the global sources of dissolved constituents in world s rivers, arrived at a balance more similar to the one presented here. He presented a compilation of various authors estimates of the sources, given here in Table 9.10. There is seemingly good agreement between the works of Holland (1978), Wollast and Mackenzie (1983 this book), Berner et al. (1983), and Meybeck s latest work (1987). Table 9.10 provides the reader with some idea of the history of source estimates for the dissolved materials of rivers and their range of values. 

The HS radical reacts with either oxygen or ozone, the latter giving the HSO radical. The oxidation processes ultimately yield SO2. The typical lifetime for atmospheric H2S is 3d. Global sources and sinks of H2S are estimated as 7.72 1.25 Tg a and 8.50 2.80 Tg a respectively, with an imbalance that was indefinable (Watts, 2000). 

Poultry fat production rates are difficult to determine, because there are no formal governmental talleys for this commodity. U.S. industry sources estimate current annual production of rendered poultry fat in that country to be 900,000 metric tons, or about one-tenth of global tallow production (61). This probably represents a sizeable proportion of global poultry fat production. Presently most of this goes into animal feeds. Historically this was the poultry feed market, although recently there has been an increase in use in other animal feeds as well. 

TABLE 4-18 Two Estimates of Global Sources of Nitrous Oxidea i... 

Table 4-7. Anthropogenic and Other Nonbiogenic Sources of Methane and Global Strength Estimates...

In the southern hemisphere the oceans cover about two-thirds of the global surface area. In Section 6.1.2 estimates for emission rates from the ocean were given as 0.3 pg/m2 h for ethane and 0.4 pg/m2 h for propane. This leads to global source strengths of Q(C2H6) = 0.63 Tg/yr and Q(C3H8) = 0.84 Tg/yr for the southern hemisphere. If the ocean provided... 

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