Geology Reference
In-Depth Information
9. a.
What is the most likely source of contamination of Big
Four Hollow Creek?
PART B. SOURCES AND AMOUNTS
OF CONTAMINATION
Contamination of surface-water sources, such as lakes
and water courses, commonly results from (1) point-
source discharge of effluent (wastewater) directly into
the water, (2) non-point-source discharge such as
runoff from fields, and (3) inflow of contaminated
groundwater. Although it may be relatively easy to
determine the location of a surface outfall and to
measure both the rate of the effluent discharge and its
composition, it is much more difficult to evaluate non-
point-source pollution and to detect areas where cont-
aminated groundwater affects the quality of surface
water.
The principle that "dilution is the solution to pol-
lution" has been used for centuries. During the 1970s
in an effort to clean up the streams and rivers of North
America, reduction and/or pretreatment of industrial
effluent was implemented.
However, dilution is still an important concept.
The reasoning behind this is that generally effluent
discharge is many times smaller than the discharge
of the receiving stream, and consequently the waste
ultimately will be diluted to an acceptable concentra-
tion for most uses by humans and for aquatic life.
For example, contaminated groundwater is con-
stantly being diluted as it slowly moves through the
ground.
The quantity of contaminated groundwater seep-
ing into a stream is generally quite small relative to the
flow of the stream, and the contaminant may be so
diluted that it is undetectable in stream waters even in
areas of discharge.
The concentration of a contaminant in a stream is
also directly related to the physical properties of the
stream. Many organic and inorganic chemicals may
become attached to silt or clay particles. These chemi-
cals can be released later and contaminate ground or
surface water that otherwise might not be contami-
nated. Suspended sediment in water (turbidity) is also
a contaminant (Table 13.1).
As indicated in the Introduction to Water
Resources and Contamination and this exercise,
major sources of water pollution come from indus-
trial, municipal (domestic and industrial sources),
and agricultural activities (Table 13.6). Physical,
chemical, or biological contaminants may adversely
affect water quality. Some constituents affect taste
(chloride, sulfate, phenols, iron), others may be cor-
rosive (high in dissolved solids, low pH) and a few
may be health hazards (heavy metals, nitrate, patho-
genic bacteria, and viruses). Increased temperature
or increased biological oxygen demand (BOD) from
organic wastes causes a reduction in the amount of
dissolved oxygen (DO) in water. DO is important for
fish survival.
b.
Could this water be detrimental to health if consumed?
Explain.
c.
What taste should it have?
10.
Why do you think that the well water in Wichita is more
highly mineralized than the well water in Shreveport? (Con-
sider climate as well as possible differences in geology.)
11.
Why does the public water supply in Seattle contain
fewer dissolved solids than the supply in Buffalo? (Consider
geology climate, and topography.)
12.
Lake Erie was once considered to be strongly contami-
nated and even "dead" by some environmentalists. Do the
data in Table 13.4 support this idea or are other data needed
(e.g., water quality factors for fish? Explain.
13.
Recall the relationship between dissolved solids (TDS) and
specific conductance (see Introduction to Exercise 13) and
detenriine the probable specific conductance for water from the
a.
Mahoning River?
b.
Big Four Hollow Creek?
14.
From the data in these tables, would you expect most
water supplies to be acidic or alkaline?
15.
What is the source of water where you are now living? If
possible, check with your local water treatment facility by
phone or online, determine its dissolved solids content and
record it here.
