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<br />~. ~: 4 <br /> <br />Issue 8: Impacts on the Soil-Scdiment-Aquatic Continum and the Related <br />Process of Sewage Treabnent <br /> <br />This issue, which is closely related to that of IXJssible abiotic concentration, <br />novanent, and disIXJsition of seeding agents, does involve real long-term issues <br />of interest to various groups. The rrajor points of. concern are those of: IXJssiple <br />effects of transient seeding agent levels on algal primry prcx:1uction in. aqUatic <br />systems (a p::>ssible transient. concem, as IIDst of these rraterials adsorb to <br />solid surfaces and accumulate in l:xJttom muds), and IXJssible direct effects on <br />fish iopulations (considered to be of minor scientific concern based on current <br />knowledge) . <br /> <br />An additional issue related to concerns on toth microbiological processes in <br />lx>ttom muds and sediments is that os IXJssible effects on anaerobic processes <br />of rrethane prcx1uction and denitrification. The available evidence does not <br />indicate that this is a significant IXJssibility with the extreme adsorptive <br />capabilities of mud cOIl1fX)nents and the formation of silver sulfides. <br /> <br />" <br /> <br />In sunmary, when silver enters a lake-type system, silver (and other rretals) <br />will tend to acc1ID1Ulate in anaerobic muds where they will cease to be in contact <br />with active microorganisms of aquatic higher organisms unless this layer turns <br />over a seasonal basis. <br /> <br />In the related biological process of rrethanogenesis in se\Vcl.ge treabnent r the <br />possible role of se\vage sludge fonmtion as a method of concentrating silver <br />in slu:1ges used. as fertilizers should be recognized. <br /> <br />l <br /> <br />The lay public might have greater concerns with these processes as water is a <br />nore visible environment related to sIXJrt and recreation interests, as OpfX)sed <br />to the soil-plant continuum discussed as Issue 7. <br /> <br />Recomnendations <br /> <br />Possible research on nucleating agent effects at transient imp::>sition concen- <br />trations on algal growth and productivity should be considered, but only in the <br />context of realistic concentrations and using field-relevant conditions. <br />This is needed prirrarily to fill an inforrration gap and is not expected to be <br />of high ecological priority. <br /> <br />Irrproved IIDni toring capabilities for silver levels and fonns are required to <br />m2et c;1 wide spectrum of inforrration needs. <br /> <br />studies of the chemistry and biological aspects of silver or other seeding <br />agents in various aquatic zones can be beneficial, especially relation to rretal <br />effects in se\Vcl.ge sludges which might be returned to soil-plant systems. <br /> <br />Issue 9: Personal Health of Seeding Equipment Operators <br /> <br />There nay be a low-level concern about health hazards associated with the hand- <br />ling, transport, or storage of toxic rraterials used as seeding agents. These <br />concerns are associated nore with industry safety organizations such as OSHA <br /> <br />c <br />