Can I convert from an emission amount (in tonnes per area) to a concentration (in ppbv)?

Question

Hi, I was wondering if it is possible to estimate the concentration of SO2 given the total mass of SO2 emissions?

Europa's EDGAR has a resource called "Global Emissions EDGAR v4.2" (see http://edgar.jrc.ec.europa.eu/overview.php?v=42). A database of SO2 emissions in Metric Tons per Area is provided, but I need concentration instead.

Currently I am determining the volume of the gas by assuming it's at STP, then I am dividing this by the estimated total containing volume, which I tried to estimate as follows.

Total Containing Volume = (11120 m*11120 m)*altitude

or

Total Containing Volume = (apprx. area of 1° latitude by 1° longitude "square")*altitude

I calculated an altitude that makes the calculation match another database of SO2 concentrations that I have. Unfortunately the other database of SO2 concentrations is limited in the area that it covers, so it is not suitable.

Is this estimation attempt misguided or is there a better way to do it? If there is another database that contains global or continental SO2 concentration grids that would also fix the problem.

Answer 1

What you are doing seems reasonable but there are many hidden assumptions in your technique:

• The data source you are using actually provides a rate, i.e. metric tons per area per year.

• Thus your calculation is also implicitly a rate: the results will be in tons per volume per year.

• You are assuming that the only source of atmospheric $\ce{SO2}$ is the emissions quantified by your data source. It may well be that there are other, natural sources of $\ce{SO2}$, or more likely, natural sinks of $\ce{SO2}$.

• If you want to know actual concentrations, you will need to quantify all the other sources and sinks of $\ce{SO2}$, and integrate all sources and sinks over time.