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88 )ournal of Weather Modification Volume 41 <br />In the following Sections we discuss the rele- <br />vance of these factors to the SPERP. <br />7.2 Soil and Soil Ornanic Matter <br />Organic matter in soil wiil bind sflver ions in the <br />same way as dissoNed organlc matter in water <br />binds silver ion, as discussed In detail earlier. As <br />part of a recent study on fhe influenve of aeolian <br />dust deposits in tlhe KNP, Johnston (2001) re- <br />ported that the percentage of organic carbon in <br />the ten centimetres of soil profiles from Mt. Clark <br />and Mt. Twynam (within the KNP) to be 12.1 % <br />and 12.796 respectively. Concentrations of or- <br />ganic matter of this order would be expected to <br />be very significant in immobilising silver in the <br />ecosystem. <br />The pH of soils in the Kosciuszko alpine area, <br />also reported by Johnston (2001), fall within the <br />range (pH 4.5 - 4.8) levels found by Spark et al. <br />(1997) to facilitate formadon of inetal-humate <br />species due to lncreased dissolution of humic <br />substances. <br />Costin (ISC 2002) has noted that the alpine hu- <br />mus soiis in the KNP reflect an accumulation of <br />soil oolloids and nutrients in the surface soils. <br />And, that the "soil buiiding processes involve re- <br />cycling by deep-rooted snow grasses and other <br />major herbs (possibly in assodation with soil my- <br />corfiiza), accretion of windblown dusts, and vig- <br />orous decomposiflon and redistribution of plant <br />remains by soil organisms, particularly inverte- <br />brates...". <br />The role of groundwater in soils is controlling the <br />spreading and filtering of catchment run-off be- <br />Tabis 5: Assessment ofAmeliorating Factors <br />fore it enters streams was noted by Costin (ISC, <br />2002). <br />Silver also adsorbs to manganese dioxide, ferric <br />compounds and clay minerals meaning that <br />these compounds are involved in silver seques- <br />tration in soil and sediments. <br />Data reported by Johnston (2001) oonfirms a <br />modest cation exchange capacity ("CEC") for <br />soils in the KNP. This means that some binding <br />of silver to clay minerals wouid be expected for <br />the soils in the study area. <br />The relatively high organic nature of the soils in <br />the SPERP target area (see Snowy Hydro Lim- <br />ited 2005 and others) suggests that DOC and soit <br />organic matter will be one of the most significant <br />factors regulating the bioavailability of silver ion. <br />Concentraaons of organic matter of this order <br />would be expected to be very significant in immo- <br />bilising siiver in the ecosystem. <br />The signfflcance and relevance of each of the <br />ameliorating factors in regulating the bioavailabil- <br />ity of silver ion in the present trial cannot be over- <br />stated. <br />7.3 Water chemistrv <br />in the lndependent Scientific Committee's ("ISC") <br />report (ISC 2002) on the KNP, Marchant <br />(Chepter 6) has noted that the water in the alpine <br />lakes is very fresh, with extremety low salinities <br />(< 3 ppm) and slightly acid with pH's ranging <br />from 6.0 to 6.2. Furthertnore, at least for Lake <br />Albina and Blue Lake, significant amounts of de- <br />composed leaves and twigs occurred in the bot- <br />tom sediments. <br />- Scientific Papers -