Quiz II - University of Florida



Quiz II Soils for Environmental Professionals Name __________________

True/ False Circle the correct answer

1. Organic matter has no impact on a soil’s acidity. True False

2. The cation exchange capacity of a soil with 20% organic matter is True False

generally greater at pH 8 than at pH 3.

3. Organic matter typically has a greater CEC on a mass basis than most soil clays. True False

4. Organic matter has no impact on soil pH. True False

5. Soil cation exchange capacity has no impact on soil pH. True False

6. Negative exchange sites on organic colloids are generated by substitution of True False

lower charge cations for higher charge cations in the organic matrix.

7. In the absence of other factors, higher-charge cations are preferred over True False

lower-charge cations on negatively charged soil colloids.

8. In the absence of other factors, large cations are preferred over small cations True False

on negatively charged soil colloids.

9. The charge on organic colloids is dependent on soil pH. True False

10. Smectites are 2:1, highly expanding minerals True False

11. Humus is a colloidal fraction of organic matter that is strongly resistant. True False

to microbial breakdown

12. The Hawthorne formation is dominated by 1:1 expanding minerals. True False

13. Organic chemicals with high Koc values are generally water soluble. True False

14. Neutral, non-polar organic molecules are highly soluble in water. True False

15. Calcium chloride is a common liming material True False

Multiple Choice (circle the correct response)

16. When a base is added to a soil

a. the pH increases

b. adsorbed H+ cations can be displaced by a cationic component of the base

c. the soil will tend to buffer the pH

d. all of the above

e. A and B

17. Adding CaCO3 to soils

a. increases acidity b. raises the soil pH

c. lowers the soil pH d. none of the above e. A and C

18. The process by which aluminum contributes hydrogen ions to soil solution is called

a. hydration b. hydrolysis

c. acidification d. dissociation

19. Soil A has a pH of 5.3. Soil B has a pH of 6.2. Which soil has the higher exchangeable acidity?

a. Soil A b. Soil B c. Can’t tell d. They are the same.

20. Soil X and soil Y both have a soil solution pH of 5.5. Soil X has 5% smectite clay and 95% sand.

Soil has 50% smectite clay and 50% sand. They have the same O.M. content. Which has the

higher active acidity?

a. Soil X b. Soil Y c. Can’t tell d. They are the same.

21. From # 20 above, which soil likely has the greatest exchangeable acidity?

a. Soil X b. Soil Y c. Cannot tell d. They are the same.

22. Soils contain about __________ the total carbon than/as all the world’s vegetation combined.

a. twice b. three times c. four times d. the same

23. If a soil solution contains equal amounts of Na+ and Al3+, which will dominate on exchange sites?

a. Na+ b. Al3+ c. neither d. can’t tell

24. Which of the following constituents of organic matter is most resistant to breakdown by microbes?

a. sugars b. starch c. cellulose d. lignins

25. Soil A has 20% organic mattter. Soil B has 5% organic matter. Which soil has the higher CEC?

a. soil A b. soil B c. can not tell d. they are the same

Short Answer

26. Identify two sources (functional groups) of negative charge on organic matter.

Indicate how charge is generated and the conditions that favor charge development.

27. Indicate the ways that organic matter impacts the chemical properties of soil.

28. Examine the plot below. It indicates the amount of two different non-polar solutes (A and B) sorbed on a single soil compared to that remaining in solution at equilibrium.

Which chemical has the higher Kd (distribution coefficient)?________________

Which chemical has the higher Koc? __________________

Which chemical is more strongly sorbed to the soil? ______________________

Which chemical would move more quickly through the soil profile?__________

29. You leach a neutral organic pesticide called “killall” through the two soils described below. Killall has a koc value of 1000 ml/g.

Soil A Soil B

Bulk density(g/cm3) 1.6 1.5

Field capacity water content 13% 25%

Organic carbon (%) 1.5 0.5

Through which soil will the pesticide move more quickly? Why?

You leach a neutral organic pesticide called “killlsome” through the two soils described

below. Killsome has a koc value of 2 ml/g.

Soil C Soil D

Bulk density(g/cm3) 1.6 1.2

Field capacity water content 10% 25%

Organic carbon (%) 1.5 0.80

Through which soil will the pesticide move more quickly? Why?

30. Match all the characteristics (a, b,c, etc) with the colloids below (1,2,3, etc). Colloids may possess more than one characteristic. Any characteristic can apply to more than one colloid.

1. kaolinite _________ a. 1:1 mineral

b. 2:1 mineral

2. smectite _________ c. lowest CEC

d. highest CEC

3. organic matter _________ e. shrink-swell clay

f. non shrink-swell clay

g. layers are hydrogen bonded together

31. Describe how mineral colloids attain charge. Include in your discussion examples of minerals, the relative CEC developed and the implications of charge development.

32. Discuss phosphorus availability in relation to pH (e.g. why P is less available at low and high pH values).

33. Indicate one advantage a Langmuir isotherm has over a Freundlich isotherm.

-----------------------

A

B

Amount on

Soil (mg/g)

Amount in

Solution (mg/L) (mg/g)

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download