Biomedical Engineering Reference
In-Depth Information
10.3.5 Enhanced Nutrient Exchange by Burrowing
Macrozoobenthos Species ........................................... 387
10.4 Future Prospectives ......................................................... 391
10.5 References ................................................................... 391
10.1 Introduction
Theories initially developed to describe transport phenomena through the clas-
sical porous medium “soil” and “ground” (Darcy 1856) are encountered liter-
ally everywhere in everyday life, in nature, and in technical applications. The
reason is that except metals, some plastics and dense rocks, almost all solids
and semisolid materials can be considered as “porous” to varying degrees.
Hence, there exist many types of different technology that depend on or make
use of theories in porous media. The most prominent examples are given in the
field of (1) hydrology, which deals with the water movement in earth and soil
structures (e.g., dams, wells, filter beds, sewage), (2) petroleum engineering,
which deals with exploration and production of oil and gas, and (3) chemi-
cal engineering (e.g., heterogeneous catalysis, chromatography, in particular,
gel chromatography, separation processes using porous polymers, biological,
and inorganic membranes). Also it has been long discovered that granular
material sintering (Chen et al. 2005) is a very large tonnage technology, where
pore structures are significant, and finds application in manufacturing ceramic
products, paper, textile, and so forth.
However, the use of porous media theories in the field of marine microbiol-
ogy is rather new, and was initiated by the discovery of the role of the seabed
in regulation of the chemical composition of water masses in world oceans,
and with it the role of oceans in the global cycles (Pamatmat and Banse 1969;
Smith Jr. and Teal 1973; Sayles 1979; Emerson et al. 1980; Berelson et al.
1982; Glud et al. 1996, 2007; Ivey et al. 2000; Nikora et al. 2002; Oldham
et al. 2004).
It has been found that at the bottom of rivers, lakes, sees, and oceans an
enhanced transport of solutes and particulate matter can be encountered in
a thin layer, which comprises of a tiny portion of the seawater layer from top
and a tiny portion of the porewater layer from below, referred to as the benthic
boundary layer (BBL). The BBL has been found to have a direct impact on
all physical, chemical, biological, and biogeochemical processes occurring in
aquatic systems (Boudreau and Jørgensen 2001).
Most direct denitrification rate measurements for continental shelves have
been made on fine-grained, muddy sediments, which cover only 30% of global
shelf area. The remaining 70% of continental shelf area is covered by sandy
sediments. These sandy sediment environments are generally characterized
by low organic matter and high pore water dissolved oxygen concentrations,
properties typically considered unfavorable for heterotrophic denitrification
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