Isotope Methods Flashcards
What are isotopes?
Isotopes are different versions of the same element, have different numbers of neutrons which changes the mass
What unstable isotopes?
Isotopes that decay into other products releasing radiation
How do we express the isotope sof water?
Have the isotopes expressed has a ratio, divide it and multiply by a million to get ppm
How do we report isotope ratios compared to a standard?
You take the (Ratio of the sample- ratio of the standard/ratio of the standard) x 1000%
What is the standard water we calculate our relative isotope ratios from?
Vienna standard mean ocean water, is called VSMOW, are it’s deep water collected from around the globe that was mixed, distilled, and analyzed for it’s isotope ratios
What is fractionation?
Any process that changes the standard ratios of isotopes
What processes cause fractionation and how?
Evaporation- light isotopes evaporate more easily
Precipitation- Heavy isotopes fall out first because during condensation the heavy isotopes condense and during ice formation the heavy isotopes form ice easier
In biological processes lighter isotopes are consumed first
Why is all surface sea water not at a ratio of 0 for isotopes? GIve examples
Because of changes between the balance of evaporation and precipitation, the mediterranean sea is heavy because a lot of evaporation happens there, the artic sea more light because big rivers run into so heavy isotopes fall out first.
Why does the rain we see further inland or higher in elevation get isotopically lighter?
Because the water vapour has heavier isotopes fall out first, so a smore precipitation occurs further inland as water vapour travels, the precipitation gets lighter and lighter same with elevation.
How does fractionation form global patterns?
Areas that are long ways away from source regions have lighter isotope ppt, and colder areas have lighter ppt
How do we use isotopes for paleoclimate studies?
Can use foraminfera, are single celled organisms and can look at isotopes in shells to determine the conditions in which they were formed.
How can you use isotopes to determine temperature?
See that in cold places fractionation increases, you can use the relationship between fractionation increasing in cold temps to determine temperature by referring to precipitation isotopes at different temperatures.
How can we use isotopes in storm tracking?
The warm and cold fronts have different isotopic signatures due to their different precipitaton patterns can allow us to track storms.
How can we use isotopes to determine evaporation processes?
2h fractionates much faster than 18o when evaporation is strong so can see the rate of evaporation by plotting 2H over 18O and then see how the fraction deviate from the line called the Global Meteoric Water Line.
How can we use isotopes to trace groundwater?
Longer flow paths might have lighter isotopic signatures, can also use 3H, if water high in it you know that it must’ve seen the atmospher ein the last 50 years
