Environmental Engineering Reference
In-Depth Information
Rainbow trout
*embryonic life stage
(
Oncorhyncus mykiss
)
**selected species
Brown trout
(
Salmo trutta
)
Brook trout
(
Salvelinus fontinalus
)
Smallmouth bass
(
Micropterus dolomieu
)
Fathead minnow
(
Pimephalus promelas
)
Pumpkinseed sunfish
(
Lepomis gibbosus
)
Ye llow perch
(
Perca flavescens
)
Bullfrog*
(
Rana catesbeiana
)
Wood frog*
(
R. sylvatica
)
American toad*
(
Bufo americanus
)
Spotted salamander*
(
Ambystoma maculatum
)
Clam**
Crayfish**
Snail**
Mayfly**
6.5
6.0
5.5
5.0
pH
4.5
4.0
3.5
3.0
FIGURE 5.34
Effect of acidity on certain organisms and life stages. (From FISRWG,
Stream Corridor
Restoration: Principles, Processes, and Practices
, Federal Interagency Stream Restoration Working Group,
1998.)
changes may be suficient to result in impacts on aquatic organisms or toxicity. For example, a
pH change of as little as 0.5 units may result in the complete sorption or desorption of some toxic
metals.
The pH also directly impacts the biota of rivers and streams. Deviations toward acidity can
cause direct or indirect mortality, and impacts can vary between speciic species and life stages as
illustrated in Figure 5.34.
As a result of the importance of pH and pH changes to aquatic health, water quality standards for
pH have been promulgated by the U.S. EPA and states. For example, in Mississippi, the pH standard
is given by:
The normal pH of the waters shall be 6.0 to 9.0 and shall not be caused to vary more than 1.0 unit within
this range. Variations may be allowed on a case-by-case basis if the Commission determines that there
will be no detrimental effect on the stream's designated uses as a result of the greater pH change. In
blackwater streams and in those watersheds with highly acidic soils, the pH may be lower than 6.0 due
to natural conditions. (MDEQ 2007)
5.7 NUTRIENTS
As indicated by the National Water Quality Inventories (USEPA 2002, 2004), one of the leading
causes of water quality impairment in rivers and streams is excess nutrients (see Figures 5.9 and
5.10). As with sediments, nutrients are recognized as a major cause of water quality impairment
even in the absence of quantitative criteria to establish the degree or the extent of the impairment.
The majority of the listings of impairments in the 305(b) reports to the U.S. EPA to date, as relected
Search WWH ::
Custom Search