Abstract A synthesis of the impacts of domestic and industrial wastes on oxygen resources and redox conditions of polluted Onondaga Lake, Syracuse, N.Y., is presented based on a long-term (1978–2005) monitoring program. Insights from this retrospective analysis are used to evaluate management alternatives for the remediation of oxygen resources and redox conditions. Reduced byproducts of anaerobic metabolism accumulated annually in the hypolimnion, causing low dissolved oxygen (DO) concentrations in the upper waters during fall turnover. The high natural sulfate (SO4 2−) concentration of the lake promoted DO depletion and the production of methylmercury (CH3Hg+). Severe depletions of DO occurred annually in the upper waters during fall mixing, representing violations of water quality standards for extended intervals from 1978 to 1996. Depletions of DO during fall were less severe from 1997 to 2004. The improvement is reported to be in response to: (1) more routine occurrence of spring turnover following closure of an industry; (2) reduction in primary productivity; (3) return of large bodied Daphnia from closure of the industry; (4) satisfaction of historic debt from earlier higher primary production levels; and (5) year-round nitrification at a contributing domestic wastewater facility. Additional improvements in oxygen resources and decreases in SO4 2− reduction are anticipated based on mandated future upgrades of phosphorus and ammonia treatment at the wastewater facility. Prevailing DO conditions during fall turnover, particularly within the context of anticipated improvements from the mandated upgrades, indicate hypolimnetic aeration or oxygenation is not required to meet water quality goals. Amendments to the hypolimnetic pool of NO3 − are recommended instead of aeration or oxygenation to inhibit production of CH3Hg+ by SO4 2− reducing bacteria. Key words: anoxiadissolved oxygneeutrophicationhypolimnetic anoxialake rehabilitationmercuryoxygenationredoxsediment diagenesis
ABSTRACT Algal bioassays and chemical fractionation analyses were applied in determining the bioavailability of phosphorus (P) discharged to Cannonsville Reservoir from its major tributary, the West Branch of the Delaware River (WBDR) and in reservoir bottom sediment. Soluble phase (soluble reactive and dissolved organic) P discharged by WBDR was found to be 100% bioavailable, in a single, dry-weather sample. Tributary particulate-phase P bioavailability varied with hydrologic conditions: 48% for a dry-weather sample and 25% for a wet-weather sample. The P-bioavailability of reservoir bottom sediments (24%) was comparable to that for the wet-weather tributary sample. Phosphorus released over the course of the tributary bioassays came from the Fe/Al-P and extractable biogenic-P pools, while that generated in reservoir bottom sediment bioassays originated entirely from the Fe/Al-P pool (despite the presence of a significant extractable biogenic-P fraction). WBDR sediment had approximately two times more total phosphorus (TP) and five times more bioavailable phosphorus (BAP) than did the reservoir's bottom sediment. Losses in particulate P between introduction and export occurred largely from the extractable biogenic-P fraction. Kinetic coefficients developed here (fraction bioavailable, solubilization coefficient) were used within the context of a nutrient-phytoplankton model to identify the sources of P ultimately realized by the algal community. Tributary soluble P accounted for 91–97% of the realized algal P. Tributary particulate P has a lesser impact due to its smaller loading contribution, lower bioavailability and because much of it is lost to sedimentation, adsorption following solubilization, and export. Depending upon the TDP:PP ratio in the tributary and bioavailability characteristics of the particulate phase P, soluble P contributes 4–7 times more P to the algal available pool than does the particulate phase.
ABSTRACT A one-dimensional hydrothermal model is used to forecast the impact of a proposed hypolimnetic discharge of treated municipal wastewater on stratification and mixing in Onondaga Lake, NY. Important simulated impacts are increased temperatures in the hypolimnion, reductions in density stratification, increased mixing and homogeneity within the hypolimnion, and reductions in the duration of summer stratification. Predictions from this analysis serve as input to water quality models that simulate related impacts of this management action. Features of the hydrothermal model include simulation of entrainment associated with plunging inflows, capability for simulations during ice cover, and a submodel to simulate the near-field mixing associated with a multiport diffuser. The model successfully simulated six consecutive years of historical stratification conditions. The model performs well in simulating the dimensions and temperatures of layers, and the timing/duration of stratification. The model is less successful in simulating the more subtle effects of dense saline inflows that linger from a recently closed soda ash/chlor-alkali facility, such as intermittent formation of chemical stratification during spring and fall mixing.
Abstract An array of in situ and laboratory measurements were made and in situ settling velocity experiments were conducted to support identification of model structure features necessary to simulate transient turbidity impacts in Schoharie Reservoir, NY, from runoff events. The program included: (1) extended deployments of recording instruments measuring temperature (T) and specific conductivity (SC) in the primary tributary and the reservoir surface waters; (2) automatic sampling of the tributary during runoff events for laboratory turbidity (Tn) measurements; (3) collection of vertically detailed profiles of T, SC, and the beam attenuation coefficient at 660 nm (c660; a surrogate of Tn) at multiple sites along the longitudinal and lateral axes of the reservoir with rapid profiling instrumentation; (4) chemical and morphometric characterizations of individual particles from the tributary and reservoir during dry weather conditions and for a runoff event with scanning electron microscopy coupled with automated image analysis and X-ray microanalysis (SAX); and (5) in situ measurements of settling velocity (SV) as a function of particle size with a LISST-ST®. A strong positive relationship between Tn, associated primarily with clay minerals, and tributary flow (Q), and a negative relationship between SC and Q, were reported. The entry of the primary tributary as a plunging turbid density current because of its lower T, and associated spatial and temporal patterns in c660 and SC imparted in the reservoir, were documented for two runoff events. SC was identified as a viable tracer of the movement of density currents in the reservoir, and the internal contribution of resuspension to c660 levels was depicted. The results of SAX analyses demonstrated a substantial fraction (i.e., 30–40%) of the Tn that enters the reservoir from the primary tributary was associated with particles >9.1 μm in diameter that do not contribute to Tn levels in the lacustrine portions of the reservoir. Higher SV values were observed for larger particles, but were much lower than Stokes Law conditions, suggesting that they existed as aggregates. The monitoring and SV experiment results were considered within the context of the structural needs of turbidity models, for two levels of complexity, to simulate the transient impacts of runoff events on the reservoir. A two- or three-dimensional transport submodel will be necessary to represent spatial patterns, and a kinetics submodel will need to represent (either implicitly or explicitly) size dependent settling, particle coagulation, and sediment resus-pension.
The historical development of environmental stressors in the watershed of Onondaga Lake (N.Y.) and the adjoining Seneca River is outlined as a prelude to the presentation of a novel approach for accessing assimilative capacity in this water quality-limited system. Proposed efforts to reclaim lost uses in the lake through heroic treatment at a major metropolitan wastewater treatment plant with continued discharge to the lake have been called into question. One option, diversion of the treatment plant effluent to the Seneca River, is complicated by phenomena impacting receiving water oxygen resources. A dual discharge strategy, which takes advantage of seasonal variations in assimilative capacity and the differing response times of the lake–river systems, is proposed as an alternative. In this approach, the effluent is routed to the river except when oxygen standards may be compromised, in which case all or part of the effluent is routed to the lake. Mathematical models demonstrate the feasibility of this option to meet water quality goals for both the lake (phosphorus) and the river (oxygen).
A sediment heat flux submodel was developed, based on the findings of related limnological studies, and incorporated into a mixed‐layer (integral‐energy) lake‐stratification model. The basic and modified versions of the mixed‐layer model were applied to three years of field data for four different lakes. The inclusion of the submodel was necessary to adequately calibrate the model to the stratification conditions observed in the two shallow transparent lakes. The stratification regimes of the two other deeper lakes were accurately simulated without accommodating sediment heat flux. These results suggest that the accurate simulation of thermal stratification in shallow transparent lakes requires consideration of sediment heat flux. Sediment and water budgets calculated with the modified model support the developed sediment heat flux submodel.
