Geoscience Reference
In-Depth Information
Mass-balance model Effect-load-sensitivity model
Amounts, fluxes and
concentrations
Ecological effects for entire ecosystems
Environmental
sensitivity
variable
or function
Input
load
Ecological
effect
variable
Q
.
C
in
Q
.
C
Compartment
load
Change in sensitivity
may change the
ecological
effect variable
Changes in
C
in
means
change in
C
KT
.
C
.
V
Ecosystem
load
=
dose
variable or function
Change in load,
C
in
or
C
,
may change the ecological
effect variable
Fig. 4.18
Illustration of the fundamental difference between dynamic, mass-balance models and effect-load-sensitivity (ELS) models.
The three wheels indicate that by means of remedial measures one may reduce the load variable in dynamic models and the load and the
sensitivity variables in ELS models. KT is the sedimentation rate. (From Håkanson & Peters 1995.)
with low pH and low bioproduction, a given
load of mercury will cause significantly higher
biouptake of mercury and hence also higher
mercury levels in fish, than in lakes with high
pH and high bioproduction. There are many
documented cases like this (see Håkanson 1999).
One classic way to develop ELS models is to use
dynamic mass-balance models to handle con-
centrations of pollutants and empirical models
(such as regressions) to link these concentrations
to the operational effect variables.
lakes mainly comes from tributaries (alloch-
thonous matter), from living and dead matter
produced in the lake (autochthonous matter) or
from resuspended materials. The SPM regulates
the transport of all types of water pollutants in
dissolved and particulate phases; it regulates
water clarity and the depth of the photic zone,
and hence also primary and secondary produc-
tion; it regulates bacterioplankton production
and biomass, and hence also mineralization,
oxygen consumption and oxygen concentrations;
and it regulates sedimentation, and hence also
the use of sediments as a historical archive, for
example of water pollutants. These matters are
discussed in this chapter. The aim of the infor-
mation given is to structure existing knowledge
on the factors regulating variations among and
within aquatic systems of suspended particulate
matter in a rational manner. This knowledge is
fundamental for an understanding of the func-
tion and structure of aquatic systems.
4.6
SUMMARY
Lake sediments are an important, integral part
of the lake ecosystem. They reflect changes in
land-use and lake characteristics and are often
regarded as a historical archive. They also affect
the present structure and function of lake eco-
systems. Suspended particulate matter (SPM) in
