1 DR. BOTHNER: I guess that just says there's a fairly uniform 



2 layer somewhere above 20 meters. 



3 DR. KRAEUTER: I didn't know whether there was just a sample 



4 missing or that it was actually a drop and then an increase? 



5 DR. BOTHNER: Right. I guess we've got the answer, there's just 



6 no sample. 



7 DR. HECKER: While we've got this up, this is also on my question. 



8 Now you find very high lead in say the 500-meter depth interval in the 



9 canyon, is that because the fine material is being continually 



10 resuspended so that's it doing a very good job of actively scavenging? 



11 Is it because of the resuspension? 



12 DR. BOTHNER: Yes, I think it's because of the resuspension. 



13 There may be a biological cycle in the scavenging of lead as well. We 



14 may be getting it from the surface waters and pumping it down, so it's 



15 quite high. 



16 In fact, I have data which I didn't show that takes the sediment 



17 trap material and compares it in the same way that I compare the bottom 



18 sediments of Lydonia Canyon, remember the histogram comparing it to 



19 average shale. 



20 The interesting point is that the resuspended sediment in the 



21 canyon axis has got more lead in it than the continental slope in the 



22 upper reaches of the canyon, the very head of the canyon. 



23 I showed you the enrichment factor as being very close to one on 



24 those four metals that were measured on the bottom sediments. For lead 



25 the enrichment factor is three and a half, as a minimum, for all the 



26 suspended matter that is collected in this sediment trap study. 



27 I think that tells me that whenever the suspended matter is having 



28 an opportunity to collect lead, that's it's doing a pretty good job. 



29 It's only in the canyon axis that we find a very, very high level. So, 



30 the scavenging seems to be having an effect on the lead concentrations. 



31 DR. BUTMAN: Mike, just to emphasize what you said, the high 



32 levels of lead in the axis can be due to two things. One is 



33 resuspension and scavenging of lead from the water column, or second, 



72 



