In order to understand more about how micronutrient and toxic metal concentrations in wild food plants changes, I sampled and tested a number of populations across the southern plateau region of North America. Cadmium (Cd) concentration is extremely variable, and in a number of populations was above the European Union’s Maximum Limits (ML) of concentration. In an effort to understand why Cd concentrations differed between populations, I used GIS to graphically represent the concentration of Cd (5 levels, 2 below /3 above ML) based on sample location. I added the NHD layers which corresponded to major bodies of water, and in an effort to account for hydrogeology between large bodies of water, used a modified version of the NHDMajorstreams layer, by extracting the records labeled as artificial path. Artificial path records represent the midpoint of water flow between large bodies of water.
I then buffered both major bodies of water, as well as artificial stream flow (.5 and 1 mile respectively). Of the 5 populations which were above ML for Cd, 4 were within the buffer areas, and population in both buffered areas generally had higher concentrations. Of the 7 populations below ML, 6 fell outside of the buffered areas, and the remaining population was nearly outside the buffered region for the Little Spokane. Based on these parameters, you could determine if a population contained safe levels of Cd 83% of the time by proximity alone.
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