Diagenesis early

Early diagenesis is typically described as a steady-state phenomenon however, unless very long-term geological timescales are considered, steady-state conditions are generally not common in shallow turbid environments such as estuaries. There are many factors that contribute to these non-steady-state conditions, such as variations in sedimentation rate, inputs of organic matter, chemistry of bottom waters and sediments, bioturbation rates, and resuspension (Lasagna and Holland, 1976). Consequently, numerous attempts 

As a result of particle settlement to the sediment-water interface, there is a mass accumulation of sediments which results in compaction of sediments and the physical upward transport or advection of solutes in porewaters to the overlying water. Similarly, solutes in porewaters can also move by diffusion as a result of concentration gradients. Thus, porewaters can be transported by advection from burials, molecular diffusion, and biological pumping or irrigation (Aller, 2001 Jprgensen and Boudreau, 2001). Diffusion in aqueous environments occurs according to Fick s laws of diffusion (Berner, 1980). Fick s first law, used for steady-state conditions, is as follows  

Fick s second law, used for non-steady-state conditions, is as follows  

To apply Fick s laws to solute fluxes in sediments, adjustments have to be made to these equations to account for the negative interference effects that sediment particles have on the diffusion of solutes in pore waters (Lerman, 1979 Berner, 1980). For example, tortuosity, defined as the length of the tortuous path that a solute travels around particles across a distance across a certain depth interval can be described by the following equation (Berner, 1980 Krom and Berner, 1980a)  

The effects of tortuosity on whole sediment diffusion can be further described as (Berner, 1980)  

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Diffusion as referred to here is molecular diffusion in interstitial water. During early diagenesis the chemical transformation in a sediment depends on the reactivity and concentration of the components taking part in the reaction. Chemical transformations deplete the original concentration of these compounds, thereby setting up a gradient in the interstitial water. This gradient drives molecular diffusion. Diffusional transport and the kinetics of the transformation reactions determine the net effectiveness of the chemical reaction. 

Berner, R. A. (1980). Early diagenesis - a Theoretical Approach." Princeton University Press, Princeton, NJ. 

Degens, E. T. and Mopper, K. (1976). Factors controlling the distribution and early diagenesis of organic material in marine sediments. In "Chemical Oceanography" (J. P. Riley, ed.), Vol. 6, pp. 59-113. Academic Press, New York. 

Emerson, S. and Widmer, G. (1978). Early diagenesis in anaerobic lake sediments II. Equilibrium and kinetic factors controlling the formation of iron phosphate. Geochim. Cosmochim. Acta 42,1307-1316. 

Berner, R.A. "Early Diagenesis A Theoretical Approach" Princeton Univ. Press Princeton, N.J., 1980 p. 241. 

I shall apply the new method of solution to a problem of early diagenesis in carbonate sediments. I calculate the properties of the pore fluid in the sediment as a function of depth and time. The different reservoirs are... 

Schauble EA, Rossman GR, Taylor HP (2001) Theoretical estimates of equilibrium Fe-isotope fractionations from vibrational spectroscopy. Geochim Cosmochim Acta 65 2487-2497 Severmann S, Larsen O, Palmer MR, Nuster J (2002) The isotopic signature of Fe-mineralization during early diagenesis. Geochim Cosmochim Acta 66 A698... 

Schematic diagram of the coupled iron and phosphate cycles during early diagenesis in marine sediments. Light gray ovals and circles represent solid phases black arrows are solid-phase fluxes. White outlined black arrows Indicate reactions white arrows are diffusion pathways. Source From Ruttenberg, K. C. (2003). Treatise on Geochemistry, Elsevier Ltd. pp. 585-643.

Berner RA. 1980. Early Diagenesis A Theoretical Approach. Princeton Princeton University Press. 

Severmann S, Johnson CM, Beard BL, McManus J (2006) The effect of early diagenesis on the Fe isotope composition of porewaters and authigenic minerals in continental margin sediments, Geochim Cosmochim Acta 70 2006-2022... 

Zaback DA, Pratt LM (1992) Isotopic composition and speciation of sulfur in the Miocene Monterey Formation reevaluation of sulfur reactions during early diagenesis in marine environments. Geochim Cosmochim Acta 56 763-774... 

In summary, it seems meaningful to consider both the formation of pyrite from the reaction of H2S with reactive ferric oxides and sulfate recycling as a result of this process in any discussion of the early diagenesis of sulfur and iron in sediments. 

The biofilm concept, applied to sediment-water interactions, breaks with classical strategies to model early diagenesis (i.e., the vertical redox zonation). Although far from completely developed, this concept may overcome modeling problems, such as an adequate description of recycling of substances. 

The redox processes and processes linked to them in the basin sediments can be written in the following or some analogous way. At least some of these processes take place during the early diagenesis, as indicated by the presence of sulfides and iron (II) carbonate in many buried sediments ... 

Widerlund, A. and Ingri, J. (1995) Early diagenesis of arsenic in sediments of the Kalix River estuary, northern Sweden. Chemical Geology, 125(3-4), 185-96. 

Briichert, V. 1998. Early diagenesis of sulfur in estuarine sediments The role of sedimentary humic and fulvic acids. Geochimica et Cosmochimica Acta 62 1567-1586. 

Benner, R., K. Weliky, and J. I. Hedges. 1990. Early diagenesis of mangrove leaves in a tropical estuary Molecular-level analyses of neutral sugars and lignin-derived phenols. Geochimica et Cosmochimica Acta 54 1991-2001. 

Opsahl, S., and R. Benner. 1995. Early diagenesis of vascular plant tissues Lignin and cutin decomposition and biogeochemical implications. Geochimica et Cosmochimica Acta 59 4889-4904. 

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