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Using tracers to investigate hydrology and biogeochemistry BEE 3710 Spring 2011.

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Presentation on theme: "Using tracers to investigate hydrology and biogeochemistry BEE 3710 Spring 2011."— Presentation transcript:

1 using tracers to investigate hydrology and biogeochemistry BEE 3710 Spring 2011

2  Dissolved constituents, isotopes, particles or physical properties of water that are used to track the movement of water through watersheds Source: USGS circular 1139

3  naturally occurring (e.g. chloride, silica, stable isotopes, organic compounds)  artificial or researcher introduced (e.g. various dyes, plastic microspheres)  sometimes unintentionally introduced! (e.g. tritium, chlorofluorocarbons, certain radioactive isotopes)  a less common isotopic form of an element  physical property of water (e.g. temperature)

4 General: Used to identify flow paths, travel times, etc. Specific uses:  Subsurface processes  e.g. preferential flow, groundwater movement  Surface processes  Biogeochemical interactions  e.g. biological nitrogen uptake

5 Image source: sediment pollutants nutrients

6  Same # of protons and electrons; different # neutrons, so different masses!  Some isotopes not very dominant

7  Represented as ‘delta’ or ‘per mil’  δ(in ‰) = (R sample /R standard - 1)1000  where "R" is the ratio of the heavy to light isotope in the sample or standard  A positive δ value means that the sample contains more of the heavy isotope than the standard; a negative δ value means that the sample contains less of the heavy isotope than the standard

8  Fractionation: when the relative amounts of a particular isotope change due to the mass differences  ie: lighter H & O isotopes are preferentially evaporated  Equilibrium vs Kinetic fractionation  Equilibrium: redistribution occurs, but reaction rates same for forward/backward direction  Kinetic: reaction rates not same if products become isolated from reactants

9 (SAHRA)

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12 (Bowen et al 2006)

13  Useful in surface and groundwater studies  In subsurface, useful for investigating infiltration patterns, flow patterns for contaminants  In streams, useful for quickly evaluating travel time & mixing

14  Low toxicity  High visibility  Consistent absorbance spectrum (Flury & Wai 2003)

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18  Types:  Conservative  Don’t react biologically or strongly sorb to sediment  ie: bromide, chloride  Reactive  Compounds affected by biological and physical reactions  ie: NO 3 -

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21  Studying flood effects on stream interactions

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26  Hyporheic flow from woody debris sediment stream FLOW SUBSURFACE FLOW

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28 (Bohlke et al 2004)

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30  Fit model to N 2 /N 2 O data

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33 (Ritchie & McHenry 1990)

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35 (Zhang & Walling 2005)

36 (Walling 2006)

37 Polylactic acid forms the framework Magnetic iron oxide nanoparticles to enable capture DNA for identification (and ability to have multiple “tags”) DNA: a polymer of four types of monomers (A, T, C, G) Tracer of length m: X 1 X 2 X 3 X 4 …X m X i = {A, T, C, G} Number of potential tracers = 4 m

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39 1 4 Collection point

40 InletOutlet Tracer 2Tracer m 2.20 m 2.85 m

41  Simple modified one dimensional advection dispersion model with a dispersion coefficient of m 2 /s and a loss factor of 6.6: Tracer 1 Tracer 2

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43  Excess phosphorus applied as fertilizer can end up in streams and lakes in the watershed  Phosphorus can be sorbed on sediment on on colloidal (<0.45 um ) particles/ dissolved in water  If we want to know where the P is coming from….sediment tracing works for P sorbed on sediment, but what about dissolved P?

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45 P + biomarker A + biomarker B P + biomarker A P + biomarker B

46 (Fanelli& Lautz 2008)

47 Cs137 dye N15 bromide 18O /2H Tracers help figure out what’s going on in a complicated world! biomarkers CFCs/ 3H


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