Wilhelm, S. M., and Bigham, G. N., 5th International Conference on Mercury as a Global Pollutant, Minamata, Japan, 2002.
 

We have compiled and evaluated data on the concentration of mercury in crude oil processed by U.S. refineries. The range of total mercury concentrations in crude oil spans 5 or 6 orders of magnitude, from parts per trillion (ppt) to parts per million (ppm) concentrations. The exact range of total mercury concentrations in crude oil cannot be assigned at present, and a defensible mean concentration can only be stated very approximately because of uncertainty in the quality of the analyses and the representativeness of the results.