Organic carbon profiles

Organic carbon profiles (Figure 4F) in all three subenvironments show the same decreasing profile with depth (13). The evaporative panne (core 1) contain the highest amounts of organic carbon which corresponds to an abundance of Spartina roots and filamentous algae visible in hand specimen. 

The two prime mechanisms of carbon transport within the ocean are downward biogenic detrital rain from the photic zone to the deeper oceans and advection by ocean currents of dissolved carbon species. The detrital rain creates inhomogeneities of nutrients illustrated by the characteristic alkalinity profiles (Fig. 11-9). The amount of carbon leaving the photic zone as sinking particles should not be interpreted as the net primary production of the surface oceans since most of the organic carbon is recycled... 

Boyer JN, Groffman PM (1996) Bioavailability of water extractable organic carbon fractions in forest and agricultural soil profiles. Soil Biol Biochem 28 ... 

Armstrong and Boalch [60] have examined the ultraviolet absorption of seawater, particularly in the wavelengths between 250 and 300 nm, where the absorption is considered to result from the presence of aromatic compounds. Light absorption is a particularly useful measure, if it can be made to work, since it is not too difficult to construct an in situ colorimeter which can produce continuous profiles of dissolved organic carbon with distance or depth [71]. 

HBEF, much of the lead entering the ecosystem from the atmosphere appears to be retained in the forest floor. Concentrations and fluxes of lead in bulk deposition are much greater than in Oa horizon leachate. Solution concentrations and fluxes of Pb decrease through the soil profile and losses in stream water are low. There was a strong correlation between concentrations of Pb and dissolved organic carbon (DOC) in soil solution and stream water at Hubbard Brook Driscoll et al., 1994, 1998). 

In sediments that lie in coastal waters, organic carbon levels are high enough to support denitrification, iron respiration, sulfate reduction and methanogenesis. As shown in the idealized profile presented in Figure 12.3b, the depth of O2 penetration in organic-rich sediments is typically so shallow as to make the zones of aerobic respiration. 

Tables 12.2 and 12.3. The effect of vertical variability is shown in Table 12.2, while the lateral spatial variability is shown in Table 12.3. The vertical and lateral spatial variabilities were defined on the basis of either the measured adsorption coefficient K), as generated from adsorption isotherms on soil profiles, or on adsorption coefficients on soil organic matter calculated as adsorption on organic carbon per unit weight of soil. We see that both vertical (Table 12.2) and lateral (Table 12.3) variability of soil affect the adsorption coefficients. A comparison between the bromide (conservative) and the two nonconservative herbicides distributions with depth after about 900mm of leaching is shown in Fig. 12.3. We see that, in the case of bromide, there is a continuous displacement of the center of mass with cumulative infiltration. In contrast, the bulk of the herbicide contaminant mass remains in the upper soil layer, with very little displacement.

A subsurface peak in HgT was evident at 2-4 cm in most cores. A mechanistic explanation for this observation is not clear. Dissolved organic carbon (DOC) concentrations ranged from about 2.5 to 4 mg/L and generally increased with increasing depth of the core. Thus, a clear correlation was not seen between Hg and DOC (38). Similarly, there was no apparent relationship between dissolved Hg and dissolved Fe or Mn. The distribution of Hg in aqueous and solid phases is the net result of many geochemical processes (e.g., redox, complexation, and solubility). Information available to our group thus far cannot explain the observed subsurface peak in the pore-water Hg profile. 

Acetazolamide can produce severe lactic acidosis, with an increased lactaterpyruvate ratio, ketosis with a low beta-hydroxybutyrateracetoacetate ratio, and a urinary organic acid profile consistent with pyruvate carboxylase deficiency. The acquired enzymatic injury that results from inhibition of mitochondrial carbonic anhydrase V, which provides bicarbonate to pyruvate carboxylase, can damage the tricarboxylic acid cycle. 

Figure 2.4. Soil inventory carbon in soil organic matter (SOM) (a), A14C of SOM (b), noncrystalline minerals (c), and crystalline minerals (d) versus age of soil substrate. Filled circles, total profile filled triangles, surface (O and A) horizons. Reprinted from Torn, M. S.,Trumbore, S. E., Chadwick, O. A., et al. (1997). Mineral control of soil organic carbon storage and turnover. Nature 289,170-173, with permission from Macmillan.

Figure 7.8 Water column profiles of (a) dissolved organic carbon (DOC) and (b) values (particulate uranium/dissolved uranium) across the redox transition in the stratified Framvaren fjord (Norway). (Modified from Swarzenski et al., 1999.)...

Figure 13.16 Down-core sediment profiles of (a) total organic carbon (TOC) and (b) atomic C N ratios at two locations in the York River estuary. (Modified from Arzayus...

Figure 13.18 Down-core profiles of porewater dissolved organic carbon (DOC), C N ratios, and total ECO2 at three stations in Chesapeake Bay. (Modified from Burdige and Zheng, 1998.)...

Alperin, M.J., Martens, C.S., Albert, D.B., Suayah, I.B., Benninger, L.K., Blair, N.E., and Jahnke, R.A. (1999) Benthic fluxes and porewater concentration profiles of dissolved organic carbon in sediments from the North Carolina continental slope. Geochim. Cosmochim. Acta 63, 427 148. 

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