The amount of GEM that was scavenged (i.e. is "missing") in the plume is simply the difference between observed plume GEM concentrations and GEM concentrations that would be expected in the absence of any scavenging (see section 2.3.5). We estimate that 160 (64; 290) µg of GEM was scavenged per gram of PM0.7DMPS, and 10.4 (3.3; 24) µg of GEM was scavenged per gram of PM0.95sulfate proxy (see Figure ). If we hypothesize that all "missing GEM" was taken up by particles in the volcanic plumes, then these values correspond directly to the resulting Hg mass fractions (in PPM) in the respective particle type (PM0.7DMPS or PM0.95sulfate).