Environmental Engineering Reference
In-Depth Information
10
3
Wet and Dry
Deposition
10
2
10
1
10
0
10
3
10
2
10
1
10
0
10
-1
10
-2
FIGURE 17.10
Ranges of P and N fluxes from different land-use categories and the rates
of N and P loading from atmospheric deposition (adapted from Loehr
et al.,
1989).
to bloom. This effect has been clearly demonstrated in the Experimental
Lakes Area in Canada; P addition without concurrent N addition led to large
blooms of the nitrogen-fixing cyanobacterium
Aphanizomonon
. This effect
continued for several years until nitrogen fixation brought the lake's nitro-
gen content to match the P addition rates (Hecky
et al.,
1994). Even if total
biomass is reduced somewhat, undesirable species may be selected for when
only N is removed. Because these cyanobacteria have gas vesicles and are
10.0
1.0
0.1
0 0 0 0 0 0 0 0 0 0 0
% watershed in agriculture or urban use
FIGURE 17.11.
Relationship between total N concentration in streams and the percentage
of land in agricultural and urban use from a large river and stream data set in the United
States (adapted from Omernick, 1977).
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