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Homework Help: Find flux of CO2: convert (μmolCO2 (mol air)^-1) to (mgC)(m^-2 of ground hr^–1)

  1. May 27, 2010 #1
    1. The problem statement, all variables and given/known data
    I am doing an experiment to find the difference in photosynthesis between different areas of grass.

    I have and am taking more measurements. But essentially I need to convert the data I have into a flux per area over time.

    the data logger records the data of CO2 concentration in (μmolCO2 (mol air)-1). I had it set to do so every second and recorded data fro 4-5 minutes.

    I have the slope of the trendline, but I am unsure what that slope is.

    Is the slope (μmolCO2 (mol air)-1) per second since its rise/run?

    2. Relevant equations
    equations of the data I have

    closed chamber: y = 2.3778x + 588.26

    clear chamber: y = -0.3184x + 399.19

    3. The attempt at a solution

    basically I want to find how much co2 was used. so if I have X amount of co2 being emitted from the ground that is my background noise. I did that with a closed chamber so no light got in and therefor no photosynthesis occurred. Then measured the same grass with a clear chamber and got a decrease. This decrease should be more since there was still background noise. So the grass was using at least as much co2 as was emitted from the ground plus some more.

    I cant actually do the calculations since I am missing an important piece of data in the volume of the chambers. which were different sizes as well.

    I want my flux in (mgC)(m^-2 of ground hr^–1)

    Can anyone give me a basic walkthrough of how to do this?
  2. jcsd
  3. May 27, 2010 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Yeah. The slope of the graph is the rate of change of CO2 concentration with time. Therefore, it has dimensions of [concentration]/[time] in the units you happen to be using for those two quantities (which you indicated).
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