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Exam 17: Water Pollution

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Question 1

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Biochemical oxygen demand is the amount of oxygen needed

A) By humans to breathe.
B) By all organisms in a system, both plants and animals.
C) For aerobic breakdown of organic matter in a system.
D) To destroy all chemical pollutants in a system.

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Question 2

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Which of the following statements is not true?

A) Chemical treatment of sediment can be effective in reducing pollution problems, but it must be repeated every few years
B) Fast-flowing streams are generally better aerated than are lakes
C) A body of water is described as "dead" when it contains fatal concentrations of toxic chemicals
D) An oxygen sag curve describes changes in a stream's dissolved oxygen content along its length below an organic-matter source

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Question 3

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Naturally occurring concentrations of some toxic elements,such as arsenic,may exceed both recommended "safe" levels and wastewater standards for industry.

Over time,dissolved magnesium concentration in a lake has reached equilibrium.Input is from streams draining into the lake; magnesium is removed by precipitation in lake sediments.If wastewater discharge upstream doubles the rate at which magnesium is delivered to the lake,

Dredging of a lake bottom

Pollution of surface water has nothing to do with pollution of groundwater.

Groundwater pollution in situ is commonly handled by

Discharge of effluent from a water treatment plant into a stream increases the BOD of the water.

Ground water contaminated with acid rain percolates through a limestone aquifer.With longer residence time in the aquifer system,

Groundwater pollution is most often and most effectively treated in situ,which minimizes the risk of spreading the pollution.

After the dangers of DDT were recognized,use of toxic organic chemicals in agriculture was virtually eliminated in the United States.

In water,the organic matter load is explained by the

Point sources of pollution include all of the following except

Given the quantitative definition of residence time,the effect of increasing the rate of input of a chemical into a natural system at equilibrium would be to increase the chemical's residence time.

Chemical decontamination is principally used for small toxic-waste spills in surface waters.

Concern about environmental pollution is such that comprehensive health hazard information has now been determined for most synthetic drugs and agricultural and industrial chemicals.

Mercury is so toxic in all its forms that it is no longer used except as a poison,as in fungicides.

The toxicity of industrial pollutants may go unrecognized for all of the following reasons except

Eutrophication does not occur naturally; it is the result of human activities altering the nutrient balance in water.

Dumping lawn clippings into a stream will reduce this