Water and Environmental Lecture 3

What is turbidity?

The measure of water clarity

What is a Secchi disk?

A disk used to gauge water clarity by measuring depth at which it is no longer visible from the surface

What is turbidity caused by?

Suspended matter (clay,silt, inorganic/organic matter, microscopic organisms etc)

Sources of turbidity?

runoff from drainage basins, waste discharges, algae, high iron concentration, air bubbles from treatment process

How are the total solids measured?

by evaporating a water sample in a pre-weight dish (B) at 103 degrees then weighing the dish and remaining residues (A)

Difference between TSS and turbidity

turbidity measures water clarity

TSS measures suspended particles

High TSS means ___ water

turbid

Why does a high TSS result in turbid water?

prevents light reaching submerged vegetation reducing photosynthesis which reduces dissolved oxygen level in water

Environmental problems with high TSS?

gets trapped in fish gills

sedimentation prevents fish eggs from hatching

reduced visibility affects predation

deposition in rivers can cause flooding

What are total dissolved solids? (TDS)

anything in water other than H2O and suspended solids

How are TDS measured?

by evaporating water sample which has been passed through a filter, in a pre-weighed dish (B mg) at 103 degrees then weighing dish and remaining residue (A mg)

what does electrical conductivity do?

estimates the amount of dissolved ions by measuring ability to conduct an electric current

TDS = ___________

conductivity x K

Local geology

rock composition determines chemistry of freshwater in a drainage basin

examples of pH measurement

pH indicator paper

liquid colorimetric indicators

electronic pH meters

What is unpolluted water pH controlled by?

carbonate buffering system

What is alkalinity?

a measure of ability of water to neutralize acid & resist a change in pH

What is hardness?

the measure of mineral content of water (total concentration of calcium and magnesium ions)

Total Hardness