Seasonal changes in Diel cycling of dissolved iron species in a coal mine drainage impacted creek

Diel fluctuations of pH, specific conductance and Fe species have been documented in Dillan Creek, a small coal mine-impacted tributary to Deckers Creek, WV. Samples were collected hourly over 16-20 hour periods and analyzed for dissolved Fe(II) and dissolved total Fe using a Hach DR2800 spectrophotometer. Fe(II) concentrations increased during the day and decreased at night during late winter sampling. Sampling conducted in the summer shows an opposite trend with Fe(II) increasing at night and decreasing during the day. Discrepancies between timing of cycles indicate a seasonal variation of controlling mechanisms. In winter, iron cycles are likely controlled by photoreduction reactions dependent on solar cycles. In summer, increased bacterial activity likely causes cycling of iron through daily Fe(II) oxidation and nightly Fe(III) reduction. Iron cycles in Dillan Creek may also be affected by mixing ratio changes induced by evapotranspiration driven water level fluctuations in groundwater.