Isotope Analysis and Water Quality

Question 1

How do we find part per mill of isotope in lake if we have fraction of water in lake?

Answer 1

time the isotope ratio by the water to get the isotope ratio of total water

Question 2

How do you calculate the relative fractions of water input given the fractions of each isotope in the lake?

Answer 2

Take the total storage fraction Ft, subtract by the second storage fraction term and divide by (storage you’re solving for- second storage term). Then find the rest by subtracting from 1. Write own eqn and look at slide 9-10.

Question 3

How do find discharge of fractions given isotope ratio?

Answer 3

times the total discharge by the relative water input, (f1). F1xQ

Question 4

How can we seperate baseflow using isotopes?

Answer 4

Calculate the fraction of the discharge that is caused by baseflow and then remove that from each point. Do this by finding Fb, times by Qt and then subtratc for each value

Question 5

Why do we get much lower hydrographs when we use isotopes to calculate out baseflow?

Answer 5

Because most of the water a river is actually being fed by groundwater

Question 6

What is an endmember?

Answer 6

When we collect a sample of one of the pure, unmixed components (like groundwater or rain

Question 7

What are tracers?

Answer 7

The chemical characteristics (e.g. (_^18)𝛿O, Cl-) that we measure on our endmembers are called “tracers”.

Question 8

How do we unmix endmembers?

Answer 8

can unmix any number (n) of endmembers, but we need n-1 tracers

Question 9

Good tracers should be what? Explain?

Answer 9

Good tracers should not be correlated, should be conservative (non-reactive), and should have contrasting values for the endmembers. Need contrasting values as the error can make them look the same and we’d have trouble differentating end members, shouldn’t be corrleated as they would fall along a line whihc make sit hard to seperate (is why we can’t use deuterium as it’s correlated with 18O) endmembers, and need to be conservative as tracers can’t chnage after mixing so they don’t effect the stream.

Question 10

What is dissolved oxygen?

Answer 10

The amount of O2 molecules dissolved in water (not bubbles!)

Question 11

Why is dissolved oxygen important?

Answer 11

Any aquatic creatures that breathe oxygen will be in trouble if DO concentration is low.
A useful indicator for a lot of pollution problems.

Question 12

How is DO measured?

Answer 12

Usually concentration (mg/L, ppm) or % saturation
Titration, or by electrode or optode instrument

Question 13

If DO low we have ____ water quality?

Answer 13

low

Question 14

Why is temperature important to dissolved oxygen?

Answer 14

Determines solubility of dissolved oxygen- when water is warm can’t hold oxygen

Question 15

What two ways do we measure water temp? Why?

Answer 15

Obviously, you would usually use a thermometer to measure stream temperature.
-But, you might miss important features, like a groundwater seep that creates a cold plume.
-So, infrared imagery might be very useful.

Question 16

What causes variation in temperature?

Answer 16

Industrial discharge (particularly from power plants)
Low flow + high radiation (if the rivers not getting recharged the water can warm up)
Climate change

Question 17

What is turbidity?

Answer 17

A measure of cloudiness of water
Caused by suspended solids and gas bubbles

Question 18

Why is turbidity important?

Answer 18

High turbidity makes it difficult for fish/insects to breed.
Contaminants (including viruses and bacteria) attach themselves to suspended solids

Question 19

How is turbidity measured?

Answer 19

By light attenuation (see how much light comes out sample)
Secchi disk (uses sun and we detect with eye)

Question 20

What causes variation in turbidity?

Answer 20

Natural events (floods, landslides affect turbidity)
Land use changes
Industrial waste

Question 21

How is nitrogen measured in water?

Answer 21

Titration
Spectrophotometry

Question 22

What causes variation in nitrogen in water?

Answer 22

Runoff from agricultural land contributes nitrogen to watersheds
Excess nitrogen can trigger massive algae blooms

Question 23

What causes eutrophication, why’s it bad?

Answer 23

A high concentration of nitrogen compounds (ususally nitrates) can cause massive algae blooms.
-Initially, that would increase the O2 concentration a bit.
-But then they die, fall to the bottom, and get consumed by microbes that consume oxygen.

-That gives you a low oxygen concentration, and fish can die.
-Certain algae blooms also excrete toxic substances, which is why we are usually asked not to drink water that is experiencing an algae bloom.

Question 24

What causes phosphorus variation in water?

Answer 24

Again, runoff from agriculture
But also, a common ingredient in soaps/detergents.

Question 25

Why is organic matter cause of fish death?

Answer 25

feeds microbes that consume oxygen leaving too little oxygen for fishies.

Question 26

How do we measure organic matter? and how does it work?

Answer 26

The BOD5 (which stands for biochemical oxygen demand over 5 days) works like this:
-Get a sample of water, put it in a dark glass bottle at 20deg C for 5 days. (dark so that no photosynthesis occurs).
-measure the oxygen concentration again.
-the change in oxygen concentration is the BOD5 value, and it tells you something about how much organic matter WAS in the water sample.

Question 27

What causes changes in organic matter in river?

Answer 27

Eutrophication
Poor sewage treatment
Spills

Question 28

Why is pH changes bad for water?

Answer 28

it can mobilize trace metals it can cause acid rain

Question 29

How do we measure ph?

Answer 29

Electrodes, spectrophotometer.

Question 30

What are heavy metals why do they matter for water quality? What causes this?

Answer 30

Are metals of environmental concern, are toxic at low levels, can be caused by industrial spills and road runoff

Question 31

Why does looking at EPT% tell you about water quality?

Answer 31

cause they’re sensitive to pollution so if really reduced you know that wate risbpolluted.

Question 32

If the river has high discharge can it be restored? When can it not?

Answer 32

yes, but if sediment polluted then no