Availability of electron acceptors

Permeability The rate of microbial ability to metabolize hydrocarbons is limited primarily by the availability of electron acceptors and nutrient supply. In... 

Thus, natural attenuation studies of hydrocarbons often focus on the availability of electron acceptors (e.g.. Barker and Wilson, 1997 Cozzarelli et al., 1995 Gieg et al., 1999 McGuire et al., 2002 Skubal et al., 2001). Numerous studies have focused on the availability of electron acceptors in both the sediment (e.g., Baedecker et al., 1993 Bekins et al., 2001a Chapelle et al., 2002 Cozzarelli et al., 2001a Heron and Christensen, 1994 Heron and Christensen, 1995 Heron and Christensen, 1995) and the aqueous phase (e.g.. Ball and Reinhard, 1996 Cozzarelli et al., 1999) as a key control of the fate of hydrocarbons in subsurface environments. In most sediment, Fe(III)s, as iron oxides, is abundant... 

The conceptual model of biogeochemical zones developed for the Norman Landhll study (Figure 7) provides a framework for understanding the transport of organic contaminants and provides insight into the natural attenuation of the concentration of leachate compounds in the aquifer. This type of approach to assessing the active microbial processes and the availability of electron acceptors can be applied at other sites contaminated with leachate. Once the biogeochemical framework of a system is established, detailed experiments on the rates of processes and the fate and transport of the compounds of concern can be undertaken. 

In summary, there seems to be a wide variation in the intrinsic potential for MTBE biodegradation depending on time and degree of the MTBE contamination, availability of electron acceptors, concentrations and types of co-contaminants as well on the geological and hydrogeological site conditions [11-14]. These very different natural conditions have to be taken into account if ENA measures are being considered. 

Availability of electron acceptors with higher reduction potentials... 

Availability of Electron Acceptors with Higher Reduction Potentials... 

In wetland soils, organic matter decomposition is frequently limited by electron acceptor availability, rather than carbon availability as in upland ecosystems. The concentration and type of electron acceptors available in soils determine the types of microbial communities involved and the rate of decomposition process. Much of the detrital matter produced in wetlands is deposited on the soil surface. It is unlikely that there is enough oxygen in this matrix to decompose this material. Therefore, the decomposition of detrital matter is also dependent on the activity of anaerobic microorganisms using alternate electron acceptors. Similarly, the rate of organic matter decomposition in soils is dependent on the availability of electron acceptors (see for discussion in Chapters 3 and 4). 

It is evident that oxygen-, nitrate-, sulfate-reducing and methanogenic conditions have a profound effect on various biogeochemical properties regulating organic matter decomposition in wetland soils (Table 5.14). A review on the comparison of microbial dynamics in marine and freshwater system as influenced by the availability of electron acceptors is presented by Capone and Kiene... 

---