Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Denitrification Deposition

The maximum critical load for nitrogen acidity represents a case of no S deposition. The value of CLmaxN not only takes into account the nitrogen sinks summarized as CLminN, but consider also deposition-dependent denitrification as a denitrification fraction /de. Both sulfur and nitrogen contribute to acidification, but one equivalent of S contributes, in general, more to excess acidity than one equivalent of N, since nitrogen is also an important nutrient, which is deficient in the most natural ecosystems. [Pg.54]

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002). Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).
CNcrit, included in the calculation of critical nitrogen leaching, Ni(crit), values, the input of this endpoint parameter into the uncertainty of CL(N) is expressed in a lesser degree. Furthermore, the runoff processes are practically not significant for ecosystems of Luvic Phaeozems, Chernozems and Kashtanozems due to low P PE ratio. During the calculations of CL(N) for ecosystems of North East Asia, the values of critical immobilization and denitrification from N depositions as the endpoints both in relative and absolute meanings played a subordinate role that obviously reflects their minor contribution into uncertainty and sensitivity analysis of the computed output values of ecosystem sensitivity to acidic deposition. [Pg.349]

Sediment deposition on the seafloor traps interstitial water. After deposition, complex reactions take place in the sediment, most of them fueled by the decay of organic matter, such as sulfate reduction, denitrification,... Because of fast diffusion rates of most cations in seawater, the presence of interstitial water makes exchange between overlying sedimentary layers a much easier process than if sediment deposition was dry. The book by Berner (1980) is entirely dedicated to these processes and only a short example is given here. [Pg.461]

It is thought that little net NO is produced in denitrification, it being readily reduced to N2O, and nitrification is therefore the main source of NO (Anderson and Levine, 1986 Skiba et al, 1993). Nitrous oxide is also produced in both nitrification and denitrification. At low O2 concentrations in otherwise aerobic soil, small amounts of N2O are formed as a by-product of nitrification, N2O not itself being reduced to NO,. In denitrification, the proportion of N2O produced relative to N2 increases as the availability of O2 increases and that of carbon decreases (Tiedje, 1988). In general only a small fraction of the N nitrified or denitrified in these pathways is released as NO or N2O. The emission is therefore sensitive to the amount of mineral N in the system, which is driven principally by additions of nitrogen fertilizers and deposition of nitrogen from the atmosphere. [Pg.249]

Estimates of denitrification rates range from 54 to 345 xmol/m2 per hour in streams with high rates of organic matter deposition, 12 to 56 xmol/m2 per hour in nutrient-poor oligotrophic lakes, and 42 to 171 xmol/m2 per hour in eutrophic lakes (62). Rudd et al. (64) reported an increase in the rate of denitrification from less than 0.1 to over 20 xmol/m2 per hour in an oligotrophic lake when nitric acid was added in a whole-lake experimental acidification. This result suggests that freshwater denitrification may be limited by N03" availability. In deep muds of slow-flowing streams, the process can effectively reduce N03" concentrations in... [Pg.233]

Mass balance calculations for the Amazon shelf seabed provide important insights into N cycling in the study area. If all of the riverine particulate N regeneration is assumed to take place in the water column, the total supply of N to the seabed (including marine PON deposition and the diffusive flux across the sediment-water interface) equals 5 7 x 10 mol d . This value is 4.4 x 10 mol d i greater than the burial term for N on the Amazon shelf (1.3 x 10 mol d O. Based on the observation of denitrification reactions in the seabed (Aller et al. 1986,... [Pg.343]

Rao, A. M. P., McCarthgy, M. J., Gardner, W. S., andjahnke, R. (2007). respiration and denitrification in permeable continental shelf deposits on the South Atlantic Bight Rates of Carbon and nitrogen cycling from sediment column experiments. Continental shey Res. 27, 1801—1819. [Pg.299]

Figure 13-13 Nitrogen budget for the North Atlantic, modified from Galloway et al. (1996), demonstrating the m or fluxes (xlO mol year ) across the boundaries of the hasin as well as sinks (denitrification) and new sources (nitrogen fixation nitrogen deposition (N dep.)) of reactive N. Fluxes into the m or physical realms of the North Atlantic (open ocean, shelf waters, and estuaries) are highlighted hy diagonal-line fills loss terms and exchange fluxes between realms are indicated by open arrows. Figure 13-13 Nitrogen budget for the North Atlantic, modified from Galloway et al. (1996), demonstrating the m or fluxes (xlO mol year ) across the boundaries of the hasin as well as sinks (denitrification) and new sources (nitrogen fixation nitrogen deposition (N dep.)) of reactive N. Fluxes into the m or physical realms of the North Atlantic (open ocean, shelf waters, and estuaries) are highlighted hy diagonal-line fills loss terms and exchange fluxes between realms are indicated by open arrows.
The continental shelves receive N from the open ocean (820 x 10 molyear ), from estuaries (250 x 10 mol year ), from major rivers (350 x 10 mol year ) and from atmospheric deposition (130 x 10 mol year ). Some is lost to the sediments (120 x 10 mol year ) and fish catch (32 x 10 mol year ), but the majority is removed from the system via sedimentary denitrification (1400 x 10 mol year ). Nitrogen introduced to the shelves from the open ocean appears to contribute the most to shelf denitrification (Seitzinger and Gibhn, 1996). [Pg.621]

We wiU treat external N loading (riverbome N, atmospheric deposition, N2 fixation), N uptake by phytoplankton, denitrification and N losses to sediments and adjacent seas. It would be impossible to treat nitrogen in isolation. Thus, the question of nitrogen versus phosphorus as the hmiting nutrient will be discussed. Comparisons between the Baltic Sea and the Mediterranean Sea, an inland sea with characteristics very different from the Baltic Sea, will be made at the end of the... [Pg.683]


See other pages where Denitrification Deposition is mentioned: [Pg.356]    [Pg.333]    [Pg.251]    [Pg.56]    [Pg.664]    [Pg.691]    [Pg.701]    [Pg.705]    [Pg.794]    [Pg.210]    [Pg.124]    [Pg.257]    [Pg.144]    [Pg.228]    [Pg.233]    [Pg.235]    [Pg.239]    [Pg.243]    [Pg.323]    [Pg.349]    [Pg.95]    [Pg.344]    [Pg.33]    [Pg.34]    [Pg.37]    [Pg.40]    [Pg.529]    [Pg.598]    [Pg.619]    [Pg.620]    [Pg.647]    [Pg.664]    [Pg.670]    [Pg.698]    [Pg.699]   
See also in sourсe #XX -- [ Pg.8 , Pg.17 , Pg.18 , Pg.20 , Pg.21 , Pg.24 , Pg.42 , Pg.59 , Pg.77 , Pg.78 , Pg.79 , Pg.83 , Pg.87 , Pg.88 , Pg.89 , Pg.94 , Pg.97 , Pg.98 , Pg.99 , Pg.103 , Pg.104 , Pg.105 , Pg.106 , Pg.107 , Pg.108 , Pg.113 , Pg.114 , Pg.126 , Pg.127 , Pg.135 , Pg.167 , Pg.168 , Pg.169 , Pg.200 , Pg.221 , Pg.302 , Pg.305 , Pg.306 , Pg.319 , Pg.332 , Pg.335 , Pg.336 , Pg.340 , Pg.346 , Pg.348 , Pg.348 , Pg.349 , Pg.349 , Pg.353 , Pg.353 ]




SEARCH



Denitrification

© 2024 chempedia.info