Environmental Engineering Reference
In-Depth Information
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NH 4 + uptake length, S w (m)
FIGURE 5.4 Uptake length of two forms of dissolved inorganic nitrogen in streams of different sizes,
synthesized from 54 published studies by Tank et al. (2008) . Symbol colors and shapes differentiate
streams by their discharge, the volume of water moving downstream per unit time. Streams with greater
discharge tend to be larger. This analysis suggests several conclusions: (1) that ammonium is taken up
much more rapidly (shorter uptake lengths) than nitrate, especially in small streams (those with lower dis-
charge); (2) that uptake length increases with discharge (which is a function of current velocity and the
cross-sectional area of the stream, so either or both of these factors can be important); (3) that there is a lot
of variation in uptake length among streams; and (4) that there is a paucity of research on nutrient dynam-
ics in larger (high discharge) streams (which are logistically difficult to study).
to one another by the following equations
( Webster and Valett 2006 ):
such as chloride or bromide to a stream for
several hours and then analyzing the
changes in concentrations over time along
the course of the stream ( Tank et al. 2006;
Webster and Valett 2006 ).
This framework has allowed stream ecolo-
gists to make rigorous comparisons of nutri-
ent dynamics across streams ( Figure 5.4
shows an example). Although this frame-
work was developed for and has been
applied almost exclusively to streams, it
could be applied to any system in which
transport is large compared to uptake.
U
v f C
S w 5
5
uzC
U
=
v f 5
uz
=
S w
where u is the average current speed, C is the
nutrient concentration, and z is the average
water depth. In practice, spiraling parameters
usually are estimated by adding nutrients
(sometimes labeled with a stable isotope)
along with a conservative (unreactive) tracer
have accumulated in the atmosphere. The most abundant highly electronegative element
(an element with a strong affinity for electrons), oxygen, is likely to serve as an electron
acceptor in redox reactions (appendix). Additionally, carbon, nitrogen, and sulfur—non-
metals in the interior of the periodic table that are essential nutrients for organisms—occur
in ecological systems in many different oxidation states and hence take many forms within
 
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