Interactions between groundwater seepage and sediment porewater sulphate concentration profiles in lake anna, Virginia
✍ Scribed by Pamela E. McIntire; Aaron L. Mills; George M. Hornberger
- Book ID
- 102861822
- Publisher
- John Wiley and Sons
- Year
- 1988
- Tongue
- English
- Weight
- 707 KB
- Volume
- 2
- Category
- Article
- ISSN
- 0885-6087
No coin nor oath required. For personal study only.
✦ Synopsis
Most sulphur diagenesis models predict that SO:concentrations decrease exponentially with increasing sediment depth and are lower than that of the overlying water throughout the sediments. Low SO: -concentrations (less than 0.2mM) are common in the sediments of Lake Anna that receive acid mine drainage; however, sediment with as much as 20mM SO4'at about 20cm below the sediment surface is also seen in this section of the lake. A decision tree was proposed to investigate the cause of the high SO4*-concentrations at depth (HSD) in the sediment. The first possibility proposed was that an increase in the quantity of groundwater flowing through Lake Anna sediments may increase groundwater advection of S O :
or oxygen which would induce sulphide oxidation. This hypothesis was tested by measuring groundwater flow. HSD profiles were found in a discrete region of the lake: however, stations having these profiles did not have higher groundwater flow than other sites sampled. Alternate explanations for the HSD profiles were that the region in which they occurred had: (1) unusual sediment chemical compositions;
(2) a different source of regional groundwater, or (3) a lateral intrusion of high SO4'-groundwater. There were no differences in sulphide and organic matter concentrations between the two regions. The area which has HSD in the sediment covers a large area in the middle of the lake, so it is unlikely that it has a unique source of regional groundwater. The third alternative was supported by the fact that in all three sample years, HSD stations were located in the preimpoundment stream channel, which is a likely lateral flow path for groundwater containing high SOa'concentrations.