R. B. Wanty Ridley W. Ian P. J. Lamothe B. A. Kimball P. L. Verplanck R.L. Runkel D.M. Borrok 2009 <p><span>Here the hydrogeochemical constraints of a tracer dilution study are combined with Fe and Zn isotopic measurements to pinpoint metal loading sources and attenuation mechanisms in an alpine watershed impacted by&nbsp;acid mine drainage. In the tested mountain catchment,&nbsp;</span><i>δ</i>⁵⁶<span>Fe and&nbsp;</span><i>δ</i>⁶⁶<span>Zn isotopic signatures of filtered stream water samples varied by ∼3.5‰ and 0.4‰, respectively. The inherent differences in the aqueous geochemistry of Fe and Zn provided complimentary isotopic information. For example, variations in&nbsp;</span><i>δ</i>⁵⁶<span>Fe were linked to redox and precipitation reactions occurring in the stream, while changes in&nbsp;</span><i>δ</i>⁶⁶<span>Zn were indicative of conservative mixing of different Zn sources.&nbsp;Fen&nbsp;environments contributed distinctively light dissolved Fe (&lt;−2.0‰) and isotopically heavy suspended Fe precipitates to the watershed, while Zn from the fen was isotopically heavy (&gt;+0.4‰). Acidic drainage from&nbsp;mine wastes&nbsp;contributed heavier dissolved Fe (∼+0.5‰) and lighter Zn (∼+0.2‰) isotopes relative to the fen.&nbsp;Upwelling&nbsp;of Fe-rich groundwater near the mouth of the catchment was the major source of Fe (</span><i>δ</i>⁵⁶<span>Fe</span><span>&nbsp;</span><span>∼</span><span>&nbsp;</span><span>0‰) leaving the watershed in surface flow, while runoff from&nbsp;mining wastes&nbsp;was the major source of Zn. The results suggest that given a strong framework for interpretation, Fe and Zn isotopes are useful tools for identifying and tracking metal sources and attenuation mechanisms in mountain watersheds.</span></p> application/pdf 10.1016/j.apgeochem.2009.03.010 en Elsevier Application of iron and zinc isotopes to track the sources and mechanisms of metal loading in a mountain watershed article