Background metals

EPA. 1979. Water-related environmental fate of 129 priority pollutants. Vol. I Introduction and technical background, metals and inorganics, pesticides and PCB s. Washington, DC U.S. Environmental Protection Agency, Office of Water Planning and Standards. EPA-440/4-79-029a, 27.1-27.16. 

In the former class, the photopolymerIsed coating Is a hard residue on the developed plate and the polymerised material Is usually oleophllllc and hydro-phobic. The background (usually a metal substrate) In contrast Is usually hydrophllllc and oleophoblc. In actual practice, the background metal lands are periodically desensitized with a suspension of colloidal particles In an acidic medium. 

Callahan, M. A., M. W. Slimak, and N. W. Gabel. 1979. Water-Related Environmental Fate of 129 Priority Pollutants. Volume I. Introduction and Technical Background, Metals and Inorganics, Pesticides and PCBs. Office of Water Planning and Standards, Washington, DC, by Versar Incorporated, Springfield, VA. EPA/440/4-79/029a. 

Another set of uncertainties involve how background tissue concentrations for essential metals influence the results of field studies, and whether it is possible to distinguish true increases in metal residues due to trophic transfer from inherent differences between species. Unfortunately, background metal concentrations in tissues are rarely measured. This hinders interpretation of data from lab and field studies, but not biokinetic studies that use radio-isotopes, where TTFs are based on accumulation and efflux of new metal, and therefore are not subject to interference from background metal concentrations. 

Fig. 17. Schematic representation of elution profiles produced by the binding of background metal ions to macromolecular ligands. [M] - = total metal concentration [M] = free metal concentration [ML] = concentration of metal-ligand complex [L] = free ligand concentration [M]o = concentration of free metal ion in the eluent. Elution proceeds from frame 1 to 3. The bottom illustration is a schematic representation of resulting chromatogram obtained by monitoring the metal content of the column effluent. See text for discussion.

---