Anthropogenic component, atmospheric

To quantify atmospheric input of these elements to the reservoir sediments, we must recognize any contribution of these elements from local rocks and soils. Rock weathering is a source of natural material, whereas soils may provide both natural and anthropogenic components to the reservoirs. Our approach to tracing these rock and soil inputs is to compare element concentrations normalized to Ti in reservoir sediments to the same ratio in rocks and soils. The underlying assumption is that Ti is insoluble during weathering of sedimentary materials, and thus is conservative and tracks their physical transport (Norton, 1986). 

Using a peat core from Denmark which was cut into 1 cm slices and age dated using both °Pb and " 0 (atmospheric bomb pulse curve), Pb was separated into lithogenic and anthropogenic components using Ti as the reference element, and the isotopic composition of the Pb determined using TIMS [166]. The data show that the maximum concentration of anthropogenic Pb (1954)... 

It is clear that both atmospheric and surface dusts are complex materials and not all that easy to describe. A summary is given in Fig. 2 of the sources of atmospheric and surface dusts and their inter-connection. Both natural and anthropogenic sources contribute to both dusts. The inter-connection between the two dusts is wet and dry deposition from the atmosphere to the ground, and the re-entrainment of surface dust through wind and human activity into the atmosphere. Dust is an important global component of our earth, and impinges on the wellbeing of people. 

Concerns over atmospheric methane as a greenhouse gas and the large contribution of biomethanogenesis as a source of this gas make it important to determine the relative significance of various components of this activity. A recent paper (8) summarized estimates (28-30) of source fluxes of atmospheric methane based on several carbon isotopic studies and presented new data on natural sources and biomass burning. These data (Table III) show that of a total flux of 594 million tons (Tg) per year, 83% is produced via biomethanogenesis from a combination of natural (42%) and anthropogenic (41%) sources. 

As discussed in Section C.la, sea salt particles in the marine boundary layer have been shown to likely play a major role in backscattering of solar radiation (Murphy et al., 1998), i.e., to the direct effect of aerosol particles. However, they also contribute to the indirect effect involving cloud formation, since they can also act as CCN. Since such particles are a natural component of the marine atmosphere, their contribution will not play a role in climate change, unless their concentration were somehow to be changed by anthropogenic activities, e.g., through changes in wind speed over the... 

The contribution of savannah fires exceeds 40% of the global level of biomass burning as a result of which the atmosphere receives minor gas components, such as non-methane hydrocarbons, carbon monoxide, methane, etc., as well as aerosols. According to available estimates for the period 1975-1980, 40%-70% of savannahs were burnt every year, about 6% of such fires took place in Africa. In 1990 about 2 1091 of vegetable biomass were burnt, and as a result 145TgCO got into the atmosphere, which constituted about 30% of anthropogenic CO emissions. 

The time of relaxation in this case constitutes 16 s, and therefore the equilibrium between NO, N02, and 03 in the atmosphere can be considered stable. However, the equilibrium N2 + 02v 2N0 under anthropogenic conditions relates to NO transforming into N02 over several hours. Therefore, from the viewpoint of global modeling, the separate consideration of the components NO and N02 is unnecessary here as well. In other words, we shall consider atmospheric nitrogen as a generalized component of the global model. 

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