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- Calculate diffusion rate of gas emitted from pond

Trying to determine diffusion rate of a gas emitted from a body of water. I believe Fick's first law may apply:

J = -D * (dc/dx)

where:

J = diffusion rate [mg/s×cm2]

D = diffusivity constant (can be looked up based on type of gas and local air temperature)

dc = change in concentration from water surface to some distance above

dx = height from water surface to some distance above

So I can look up D, I know the concentration as measured at height "h" above the water, and dx = h. I don't know the concentration at the water surface. Can Fick's first law be used to compute diffusion rate in this situation, or is there a better

approach?

Thanks!

J = -D * (dc/dx)

where:

J = diffusion rate [mg/s×cm2]

D = diffusivity constant (can be looked up based on type of gas and local air temperature)

dc = change in concentration from water surface to some distance above

dx = height from water surface to some distance above

So I can look up D, I know the concentration as measured at height "h" above the water, and dx = h. I don't know the concentration at the water surface. Can Fick's first law be used to compute diffusion rate in this situation, or is there a better

approach?

Thanks!