| Patterns depicting variability, both spatially and temporally, of redox conditions of the near-bottom waters of New Croton Reservoir, New York are elucidated through seasonal plots of redox sensitive and associated parameters (DO, NOx, NH3, Mnt, Mnd, Fe t, Fed, SRP, and g440). For instance, during the period of hypolimnetic anoxia, Fed levels at one sampling station exceeded 10,000 mug L-1 and were correlated with Gelbstoff absorbance and SRP levels which peaked at 16.9 m-1 and 241 mug L-1 respectively. The analysis further depicts strong spatial variability in the near-bottom waters with respect to the magnitude of the anticipated thermodynamic sequence of species consumed and evolved by the sediments under reduced conditions. Gradients in depth and volume per unit area occurring along the longitudinal axis of the reservoir reflect its original riverine nature and govern the onset and duration of stratification and magnitude of local hypolimnetic oxygen pools. Additionally, anthropogenic features further heighten variability by affecting longitudinal mixing, local vertical mixing, and depositional processes that distribute organic matter to the sediments. The operations of a hypolimnetic aeration experiment strongly influenced local redox conditions of the near-bottom waters and the importance of knowledge of redox variability within a reservoir was identified as a useful tool for managers to maintain the integrity of drinking water withdrawn from the reservoir. |
