Environmental Engineering Reference
In-Depth Information
400
A
300
200
100
0
5
6
7
pH
400
B
300
200
100
0
30
80
130
180
g L -1 )
Median weekly aluminum (
μ
FIGURE 14.13 Biomass of trout in Adirondack streams as a function of pH (A) and alu-
minum (B) (reproduced with permission from Baker et al., 1996).
METALS AND OTHER INORGANIC POLLUTANTS
A wide variety of metals and some other inorganic materials act as
toxic pollutants in aquatic ecosystems (Table 14.3). Metals can bioaccu-
mulate in many organisms, and can be bioconcentrated in trophic food
chains. Bioconcentration has led to problems such as excessive lead con-
tamination of fish. Complex pelagic food webs with many lateral links
transfer less metals up the food chain (Stemberger and Chen, 1998), an ad-
ditional argument for maintenance of biodiversity. Atmospheric deposition
and industrial waste releases, particularly mining (Table 14.4), are com-
mon sources of metal contamination. Such mining activities have had ex-
tensive negative impacts in some aquatic habitats (Sidebar 14.1).
Chemical conditions can alter the bioconcentration and toxicity of
metals. For example, it has been demonstrated that cadmium, silver, nickel,
and zinc uptake by invertebrates is highly influenced by reactive sulfides in
sediments (Lee et al., 2000). High-sulfide sediments bind the metals and
render them less toxic. Also, the redox state of metals can influence toxic-
ity; hexavalent chromium is much more toxic than trivalent chromium,
Lead toxicity for waterfowl has been a particular concern in freshwater
systems because of the historical use of lead shot pellets for hunting. Water-
fowl such as ducks, geese, and coots ingest the pellets as grit for their crops.
Less than 10 lead pellets will kill a bird, but marshes frequented by hunters
may have 6 or 7 pellets m 2 in the sediments. For this reason, the U.S. Fish
Search WWH ::




Custom Search