I recently ran across an article that was written by an experienced Surfer user, Joseph A. Ricker. The article, A Practical Method to Evaluate Ground Water Contaminant Plume Stability, provides a workflow for determining the average contaminant plume concentration that I thought our Surfer community may find interesting. Below, I've summarized the workflow outlined in Mr. Ricker's article and provided the exact steps required to duplicate this in Surfer 14.
First, grid the contaminant concentration data using Surfer. In Mr. Ricker's example the values range from non-detectable (0) to 9400 µg/L so applying a Log, save as linear Z transform would be recommended. This prevents the areas of high concentration from being ignored, or from having too large an effect on the surrounding area. Since we are gridding concentration data, a minimum Z of 0 can also be defined to prevent the grid z values from becoming negative. To grid the data with these options:
Next, calculate the volume of the plume where the concentration is above the accepted safe level.
Finally, divide the volume (in units of µg/L*m2) by the planar area (in units of m2) to get the average plume concentration above the cutoff or safe concentration.
This workflow is a great example of the many ways Surfer's gridding algorithms and grid-based calculations are used in the field.
Hi Carlos - Thank you for your question! The data used for the article has some additional rows of data which would explain why your results are different. You can download the data used here: https://goldensoftware.sharefile.com/d-sfd62bd04fea46658.
A blanking polygon was not used during this example, but you could use one during this workflow if desired.
If you have any additional questions, feel free to email us at firstname.lastname@example.org.
Thank you - Golden Software
Dear Katie, thanks for the tips about Mr. Ricker's article. However, I am having trouble reproducing your result. I am using the data presented in the article's Table 1. In this table we have only 24 data, I am using them, but my results are completely diferent from yours. In your tips, I see that the data columns are 39 points, Why is that? Did you use a different data collection? And about the grid, did you use a blank polygon? What numbers did you use for ND concentration? Can you please, help me? thank you, Best Regards.