Isotope Analysis and Water Quality Flashcards
How do we find part per mill of isotope in lake if we have fraction of water in lake?
time the isotope ratio by the water to get the isotope ratio of total water
How do you calculate the relative fractions of water input given the fractions of each isotope in the lake?
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.
How do find discharge of fractions given isotope ratio?
times the total discharge by the relative water input, (f1). F1xQ
How can we seperate baseflow using isotopes?
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
Why do we get much lower hydrographs when we use isotopes to calculate out baseflow?
Because most of the water a river is actually being fed by groundwater
What is an endmember?
When we collect a sample of one of the pure, unmixed components (like groundwater or rain
What are tracers?
The chemical characteristics (e.g. (_^18)𝛿O, Cl-) that we measure on our endmembers are called “tracers”.
How do we unmix endmembers?
can unmix any number (n) of endmembers, but we need n-1 tracers
Good tracers should be what? Explain?
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.
What is dissolved oxygen?
The amount of O2 molecules dissolved in water (not bubbles!)
Why is dissolved oxygen important?
Any aquatic creatures that breathe oxygen will be in trouble if DO concentration is low.
A useful indicator for a lot of pollution problems.
How is DO measured?
Usually concentration (mg/L, ppm) or % saturation
Titration, or by electrode or optode instrument
If DO low we have ____ water quality?
low
Why is temperature important to dissolved oxygen?
Determines solubility of dissolved oxygen- when water is warm can’t hold oxygen
What two ways do we measure water temp? Why?
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.
What causes variation in temperature?
Industrial discharge (particularly from power plants)
Low flow + high radiation (if the rivers not getting recharged the water can warm up)
Climate change
What is turbidity?
A measure of cloudiness of water
Caused by suspended solids and gas bubbles
Why is turbidity important?
High turbidity makes it difficult for fish/insects to breed.
Contaminants (including viruses and bacteria) attach themselves to suspended solids
How is turbidity measured?
By light attenuation (see how much light comes out sample)
Secchi disk (uses sun and we detect with eye)
What causes variation in turbidity?
Natural events (floods, landslides affect turbidity)
Land use changes
Industrial waste
How is nitrogen measured in water?
Titration
Spectrophotometry
What causes variation in nitrogen in water?
Runoff from agricultural land contributes nitrogen to watersheds
Excess nitrogen can trigger massive algae blooms
What causes eutrophication, why’s it bad?
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.
What causes phosphorus variation in water?
Again, runoff from agriculture
But also, a common ingredient in soaps/detergents.
