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September 1996 -8- 963-2128.002 <br /> example Neuman, et al. (1987) found that extractable Cu levels in mine soils from selected <br /> western coal mines (e.g., Spoil =1.4 ppm and Spoil overlain with 0.6 m topsoil =1.0 ppm) <br /> were far below phytotoxic levels - probably by two orders of magnitude. Their conclusions <br /> were that Cu toxicity is probably of little concern and should only be suspected in mine soils <br /> that are acidic. The NH4OAc - extraction method used to estimate plant available Cu in <br /> biosolids from the Silverthorne Dillon Joint Venture (SDJV) POTW estimated a <br /> concentration of 2.2 mg/kg. Considering the findings of Neuman et al. (1987) the <br /> exchangeable Cu in biosolids from the SDJV is well below phyotoxic limits. <br /> Analysis of plant tissue rather than soil samples is generally of greater value in identifying <br /> potential problems with toxic substances because of difficulties in obtaining representative <br /> soil samples and because plants biologically integrate/indicate the soil environment and they <br /> represent the final usable product on agricultural lands (Smith et al. 1989 and others). <br /> Literature and plant tissue data will be presented below to demonstrate the low potential for <br /> Cu-induced phytotoxicity as a result of biosolid additions to tailings and waste rock at the <br /> Climax Mine. <br /> 2.5 Plant Species Behavior <br /> Although some heavy metals (e.g., Cu and Zn) are essential for plant growth, it is now well <br /> documented that when present at elevated levels in soils they are generally phytotoxic and <br /> can ultimately cause death of plants (Antonovics, Bradshaw and Turner 1971; and Smith and <br /> Bradshaw 1979). The term phytotoxicity is normally associated with phenomena whereby a <br /> potentially harmful substance has accumulated in the plant tissues to a level affecting optimal <br /> growth and development of the plant (Beckett and Davis 1977; Davis et al. 1977). Although <br /> phytotoxicity of Cu has been extensively reported, data suitable to delineate the cause-and- <br /> effect relationship between leaf tissue concentration of Cu and the extent of plant growth <br /> retardation are sparse (Chang, Granato, and Page 1992). <br /> iuu�zueux noc Golder Associates <br />