IT’S SEDIMENTARY, MY DEAR



WATSON



OBJECTIVES



The students will do the following:



1. Determine the amount of solid material or sedi-

ment suspended in water samples.



2. Explain turbidity observations of water samples.



3. Explain ways in which sediment disturbs organ-

isms.



4. Determine possible local nonpoint sources of sedi-

ment present in water samples. :



BACKGROUND INFORMATION



Heavy rains or snow melt can wash a variety of sus-

pended materials or sediment into water bodies and

make water cloudy or turbid. Turbidity is a measure of

the amount of suspended material (cloudiness) in the

water. Many other pollutants such as bacteria, nutri-

ents, and harmful chemicals can attach to sediment

particles and be transported with the sediment. While

the process is natural, human activities can increase the

rate faster than ecosystems can adjust. Improperly

managed construction sites may cause a 2,000-fold

increase in erosion rates and poorly managed farmland

may cause a 200-fold increase, compared to rates of

similar undisturbed forest lands. Sediment can inter-

fere with aquatic life, commercial and recreational

activities, and hydroelectric power generation. Sedi-

ment can decrease light transmission through the wa-

ter, thus decreasing plant photosynthesis and repro-



a >



SUBJECTS:

General Science, Earth Science, Ecology,

Chemistry, Biology



TIME:

2-4 class periods



MATERIALS:



thermometers



local topographic map



filter paper



funnels



stirring rods



balances (electronic preferred)



shovel or spades (to collect soil, optional)



turbidimeter (optional)



clean, dry, wide-mouth collection bottles

with lids (two per student or lab team)



beakers



large watch glasses



stick-on labels or masking tape



permanent ink markers or grease pencils



area land use maps



samples of water from local streams or

lakes



data table (included)



cooler with ice (optional)



calculators (optional)



soil—preferably clay type (optional)



sun lamp or grow light (optional)



data sheet (optional; included)



graph paper



"Collecting a Water Sample" handout (in-

cluded; see page 60)



"It's Sedimentary" Quiz (optional, in-



cluded)



_/



duction. Also, sediment absorbs heat causing the temperature of the water to increase. A decrease in

photosynthesis and /or an increase in water temperature can result in a decrease in the level of dissolved

oxygen. Moreover, sediment can interfere with feeding and reproductive patterns of aquatic life. When

sediment settles, it may create blankets which smother the aquatic plants and animals, and disrupt the

food chain. Sediment can gradually fill lakes and streams. This can reduce flood storage capacity and

hydroelectric power potential in reservoirs and cause navigation problems in rivers. The best way to

solve nonpoint problems caused by sediment is to prevent or reduce soil erosion caused by human



activities.



ERG - Nonpoint Source Pollution Prevention



A&WMA,; 9-12 © 1993