Lake environments - Environmental Sedimentology - page 124

Table 4.7 A chemical classification of elements in lake sediments. (Modified after Kemp et al. 1976.)

1. Major elements (Si, Al, K, Na and Mg) make up the largest group of the sediment matrix
2. Carbonate elements (Ca, Mg and CO 3 -C) constitute the second largest group; about 15% of the materials
3. Nutrient elements (org.-C, N and P) account for about 10% in recent lake sediments
4. Mobile elements (Mn, Fe, P and S) make up about 5% of the total sediment weight
5. Trace elements (Hg, Cd, Pb, Zn, Cu, Cr, Ni, Ag, V, etc.), the smallest group accounting for less than 0.1% of the
sediments

Table 4.8 Chemical characteristics of lake sediments from different regions of the world (data from Jones & Bowser 1978).

Region Lake/group type P Organic C Fe Mn Ca K Si Al

Minnesota lakes Low organic 0.13 7.6 5.0 0.6 0.9 1.2 - -

High organic 0.17 21 3.8 0.1 2.0 0.7 - -

High carbonate 0.14 9.9 2.2 0.15 15.2 0.5 - -

Low carbonate 0.08 6.1 2.5 0.4 6.8 0.4 - -

African lakes Kivu - - 5.3 0.09 9.5 - 19 5.0

Tanganyika - - 5.0 0.03 1.2 - 26 10

Edvard - - 2.4 0.03 3.0 - 29 4.3

Albert - - 6.2 0.1 1.4 - 25 12

Great Lakes Ontario 0.07 - 3.7 0.06 0.4 2.3 24 5.1

Erie 0.06 - 2.8 0.06 0.35 2.2 26 4.8

Michigan 0.08 - 1.5 0.08 11 1.3 25 2.8

Superior - 2.3 2.5 0.05 1.2 0.5 24 2.4

generally have loose sediments with high water
contents and low K s values, whereas eutrophic
lakes often have sediments with a water content
of surficial sediments in the range 83-93% ww
and K s

what this means in terms of lake processes
(see Håkanson & Jansson 1983; Pedley 1990).
Table 4.8 is included here to stress this point. It
provides data on sediment chemical properties
(P, organic carbon, Fe, Mn, Ca, K, Si and Al)
for lakes in Minnesota categorized into four
groups (low and high organic, and low and high
carbonate groups), for four large African and
four large American lakes. From Table 4.8 it can
be noted that some of these substances do not
vary a great deal among these lakes (e.g. P and
Si), whereas other substances (such as Ca and
organic C) vary a great deal. This is an import-
ant point. Sediment variables, just like water
variables, can vary among lakes owing to differ-
ences in catchment area characteristics (geology,
soils, land-use, vegetation, etc.) and within lakes
depending on climatological factors, season of
the year, changing winds (such as frequency of
storms) and bottom dynamic conditions. This
means that some variables can reflect typical lake
conditions much better than others, Sediment
phosphorus, manganese and iron are well known
(see Table 4.5) for poorly reflecting typical lake

5. Mesotrophic
and oligotrophic lakes cannot be distinguished
from eutrophic lakes by the water content of
the sediments, but often by the sediment con-
stant, which generally attains higher numerical
values for low-productivity lakes. This depends,
however, on many things, for example supply
of minerogenic matter, which is relatively high
in oligotrophic lakes, and on bioturbation, which
is generally higher (causing higher K s values)
in sediments rich (but not too rich) in organic
matter and food for the bottom fauna.
Chemical analyses of sediment cores can offer
a good key to the history of lakes, and also to the
present conditions. A chemical classification of
elements in lake sediments is given in Table 4.7.
Sediments affect and reflect the characteristics
of lakes. Many studies have been presented
related to the chemical composition of lake water
and sediments and to interpretational codes of

values of about − 2 to −