Land-atmosphere fluxes

The agricultural emissions of NHj, NjO and NO must be considered in context the processes which lead to net loss from the soil and vegetation are natural and form a part of the land-atmosphere cycling of this vital nutrient. The current agricultural processes, however, create conditions in which the small natural background fluxes, in the range of a few ngNm s are dwarfed by losses from fertilized land. 

Primary processes regulating land-atmosphere exchange (secondary) Availability of data and including models to calculate annual fluxes ... 

The surface s role in land-atmosphere water exchange deals with the subdivision of the phase space into at least two levels soil and ground water. The soil level plays the role of a buffer zone between precipitation and ground water. The simplest parameterization of fluxes between these levels is reduced to their linear dependences WsH(t,i,j) = XijWs(t,iJ) and wHS(t,i,j) = However, a more strict... 

A major LAII research project is the Flux Study, whose principal purpose is a regional estimate of the present and future movement of material between the land, atmosphere, and ocean in the Kuparuk River basin in northern Alaska. 

This increase in atmospheric CO2 concentration for the past 200 years is primarily a result of the increased flux of carbon gases (CO2, CO, CH4) to the atmosphere from the land because of the burning of fossil fuels and deforestation and cultivation practices of society. It is likely that land use fluxes were more important than fossil fuel sources in the 19th and early 20th century, but during much of the latter century fossil fuel CO2 releases appear to have been greater than... 

Romero, O.E., Dupont, L., Wyputta, U., Jahns, S., and Wefer, G (2003) Temporal variability of fluxes of eolian-transported freshwater diatoms, phytoliths, and pollen grains off Cape Blanc as reflection of land-atmosphere-ocean interface in northwest Africa. J. Geophys. Res. 108, 3153. 

The average calcium content in deposition over land is about 3 mg/L, and the annual flux to the global terrestrial ecosystem is 0.34 x 10 tons. Thus, the overall annual calcium fluxes in the land-atmosphere system is 0.41 x 10 tons per year. 

The land use change flux and the residual terrestrial sink add up to the land-to-atmosphereflux. The residual terrestrial sink is estimated as the difference between the land-to-atmosphere flux and tiie land use change flux. Both the land-to-atmosphere flux and the residual terrestrial sink are inferred values whose magnitude are those required... 

The cycles of carbon and the other main plant nutrients are coupled in a fundamental way by the involvement of these elements in photosynthetic assimilation and plant growth. Redfield (1934) and several others have shown that there are approximately constant proportions of C, N, S, and P in marine plankton and land plants ("Redfield ratios") see Chapter 10. This implies that the exchange flux of one of these elements between the biota reservoir and the atmosphere - or ocean - must be strongly influenced by the flux of the others. 

Rainwater and snowmelt water are primary factors determining the very nature of the terrestrial carbon cycle, with photosynthesis acting as the primary exchange mechanism from the atmosphere. Bicarbonate is the most prevalent ion in natural surface waters (rivers and lakes), which are extremely important in the carbon cycle, accoxmting for 90% of the carbon flux between the land surface and oceans (Holmen, Chapter 11). In addition, bicarbonate is a major component of soil water and a contributor to its natural acid-base balance. The carbonate equilibrium controls the pH of most natural waters, and high concentrations of bicarbonate provide a pH buffer in many systems. Other acid-base reactions (discussed in Chapter 16), particularly in the atmosphere, also influence pH (in both natural and polluted systems) but are generally less important than the carbonate system on a global basis. 

A small flux is shown between the land and atmosphere. This represents the transport of dust particles to the atmosphere (F28) and the deposition of these particles back on land either as dry deposition or associated with atmospheric precipitation (F82). Similarly, fluxes that represent the transport of seasalt from the surface ocean to the atmosphere (Fss) and the deposition of soluble (F85) and insoluble (F81) atmospheric forms are also shown. As already discussed for the river fluxes, the insoluble particulate flux is represented as a direct transport of P to the sediment reservoir. 

While the natural exchange of mercury between the land and atmosphere and the atmosphere and oceans is balanced, human activity has tipped this balance. There is now about three times more mercury in the atmosphere and fluxes of more than four times to and from the atmosphere. 

The transport rate of mercury flowing from the land to the oceans in rivers has been increased by a factor of about three by human activity. While the increased rate is still relatively less important than the total transport of Hg through the atmosphere, it can represent a significant stress on the exposed organisms, particularly since the increased flux is unevenly distributed. That is, human activity has created local environments where the transport of mercury or its concentration in a river or estuary is many tens of times higher than background levels. 

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