Chemical Exchange at the Sediment-Water Interface of Cannonsville Reservoir
Titel:
Chemical Exchange at the Sediment-Water Interface of Cannonsville Reservoir
Auteur:
Erickson, Michael J. Auer, Martin T.
Verschenen in:
Lake and reservoir management
Paginering:
Jaargang 14 (1998) nr. 2-3 pagina's 266-277
Jaar:
1998-09-01
Inhoud:
Rates of chemical exchange at the sediment-water interface of Cannonsville Reservoir were determined using intact sediment cores. Reference sites for coring were selected based on the results of a surficial sediment survey. Higher levels of volatile suspended solids, chemical oxygen demand, total organic carbon, total nitrogen, and total phosphorus were noted at deep water stations proximate to the dam and near the discharge of the West Branch of the Delaware River (WBDR, the reservoir's major tributary). Rates of sediment oxygen demand (SOD), measured at 20 °C at the three reference sites, ranged from 0.66 to 1.67 gO2 · m-2 · d-1 with a mean±s.d. of 1.06±0.23 gO2 · m-2 · d-1. No statistically significant variation in SOD with location in the reservoir was noted. No phosphorus (P) release was detected under aerobic conditions. Rates for cores incubated under anaerobic conditions ranged from 9.2 to 15.6 mgP · m · -2 · d-1, with a reservoir-wide mean±s.d. of 12.9 ± 2.2 mgP · m-2 · d-1. P-release rates at P-enriched sites (surficial sediment survey) were higher than at mid-reservoir locations with lower sediment-P. Rates of ammonia-nitrogen (NH3-N) release ranged from 19.6 to 43.2 mgNH3-N · m-2 · d-1 with a reservoir-wide mean ± s.d. of 31.8 ± 7.2 mgNH3-N · m-2 · d-1. A general trend of decreasing sediment NH3-N release with distance from the discharge of the WBDR was noted. Rates of sediment exchange measured here are consistent with those reported for other systems of a similar degree of nutrient enrichment and trophic state. Downcore profiles of sediment chemistry suggest that while organic carbon and nitrogen are undergoing diagenesis in the reservoir (SOD is exerted and NH3-N release is observed), P deposited to the sediment remains in the particulate form and is not recycled. The sediments are, however, rich in the forms of particulate P which support release. High rates of P exchange maybe expected if trophic state conditions deteriorate further, resulting in extended anoxia.
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