Implications of redox processes for the rehabilitation of an urban lake, Onondaga Lake, New York

TPe levels that continued to the late 1990s (~50 mg/L) and up to the mandated decrease in Metro effluent concentration to 0.12 mg/L (through 2004) resulted in only a small degree of nutrient limitation.

“However, the available evidence indicates that the TPe levels that continued to the late 1990s (~50 mg/L; Connors et al. 1996), and even up to the mandated decrease in the Metro effluent concentration to 0.12 mg/L ( e.g. , through 2004), resulted in only a small degree of nutrient limitation.”

• cites Connors et al. 1996 sourceDisputed

  The citation is attached to the claimed Metro effluent concentration of approximately 50 mg/L. The Study System section (p. 4) instead reports an average effluent total-phosphorus concentration of about 0.6 mg/L since the late 1980s; this 1996 paper does not establish levels through the late 1990s. Its discussion of a small degree of nutrient limitation (p. 9) concerns the 1989–1992 study period, not the later period in the citing sentence. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured

Through the late 1990s, the Metro input represented 80% of effective phosphorus loading to Onondaga Lake.

“Through the late 1990s the Metro input represented 80% of the total nitrogen (N) loading (Matthews et al. 2001) and 80% of the effective ( i.e. , can support phytoplankton growth) P loading (Effler et al. 2002).”

• cites Effler et al. 2002 sourceSupported

By the onset of fall turnover, CH4 and ∑S 2- were eliminated from the water column as a result of rapid oxidation.

“By the onset of fall turnover, CH 4 and ∑S 2were eliminated from the water column as a result of the rapid oxidation of these constituents (Effler et al. 1988, Addess and Effler 1996, Gelda and Auer 1996).”

• cites Effler et al. 1988 sourceNot checked — no full text of the source
• cites Addess and Effler 1996 sourceSupported
• cites Gelda and Auer 1996 sourcePartly supported

  The Reduced Chemical Species Oxygen Demand section (p. 7) identifies methane and sulfide among the reduced species oxidized as fall turnover approaches. The Reduced Species section (p. 9) says their concentrations decline during fall mixing, not that they have been eliminated from the water column by the onset of turnover. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

In 1990, the minimum dissolved oxygen concentration was 1.6 mg/L.

“Progressive increases occurred after the mid-October minimum (DOmin = 1.6 mg/L; Fig. 3a) in response to inputs from atmosphere exchange and photosynthesis exceeding sink processes (Gelda and Auer 1996).”

• cites Gelda and Auer 1996 sourcePartly supported

  The Dissolved Oxygen – UML section (p. 10) describes a fall 1990 oxygen minimum followed by recovery, but it does not give the minimum as 1.6 mg/L. The cited paper supports the recovery discussed after the parenthetical value, not that specific number. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

The vertical pattern of progressive increases with depth is recurring for the byproducts of the various metabolic pathways, reflecting localization of decomposition processes within the sediments or at the sediment-water interface in combination with limited mixing within the hypolimnion.

“This vertical pattern is recurring for the byproducts of the various metabolic pathways (Fig. 4b-e), reflecting the localization of these decomposition processes within the sediments (or at the sediment-water interface) in combination with limited mixing within the hypolimnion (Effler et al. 1988, Addess and Effler 1996).”

• cites Effler et al. 1988 sourceNot checked — no full text of the source
• cites Addess and Effler 1996 sourceSupported

The hypereutrophic condition of Onondaga Lake caused depletion of dissolved oxygen in the upper waters during the fall mixing period associated with oxidation of reduced byproducts.

“depletion of DO in the upper waters during the fall mixing period associated with the oxidation of these byproducts (Gelda and Auer 1996)”

• cites Gelda and Auer 1996 sourceSupported

The hypereutrophic condition of Onondaga Lake caused subsequent accumulation of reduced byproducts of anaerobic metabolism, including sulfide and methane.

“subsequent accumulation of reduced byproducts of anaerobic metabolism, including ∑S 2(Effler et al. 1988) and CH4 (Addess and Effler 1996)”

• cites Effler et al. 1988 sourceNot checked — no full text of the source
• cites Addess and Effler 1996 sourceSupported

The effects of the industrial facility on Onondaga Lake were largely eliminated by closure of the facility.

“These effects were largely eliminated by the closure of the facility (Effler and Matthews 2003).”

• cites Effler and Matthews 2003 sourcePartly supported

  The Synthesis/Management Perspectives (p. 19) reports dramatic improvements in Onondaga Lake’s water quality and ecology after closure. But the same section (p. 20) says residual ionic waste loading continued and “a number of the impacts have only been reduced not eliminated,” so the claim overstates the extent of recovery. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

Saline wastes from soda ash manufacture had profound impacts on the biological, chemical, and physical characteristics of Onondaga Lake.

“Saline wastes (Ca 2+ , Na + , Cl -) from the manufacture of soda ash had profound impacts on the biological, chemical, and physical characteristics of the lake (Effler and Matthews 2003).”

• cites Effler and Matthews 2003 sourceSupported

The hypereutrophic condition of Onondaga Lake caused exodus of fish from the lake during the fall mixing interval of years of severe dissolved oxygen depletion.

“exodus of fish from the lake during the fall mixing interval of years of severe DO depletion ( e.g. , Tango and Ringler 1996)”

• cites Tango and Ringler 1996 sourceSupported

The explanation that retains thermodynamic consistency is that CH4 was produced in subsurface sediment depths deeper than the favored electron acceptors DO, NO3-, and SO4 2- can reach through diffusion from the overlying water column.

“The explanation that retains thermodynamic consistency is that CH 4 was produced in subsurface sediment depths deeper than the favored electron acceptors, DO, NO 3 -, and SO4 2, can reach through diffusion from the overlying water column (Fig. 1; Matthews et al. 2008).”

• cites Matthews et al. 2008 sourceSupported

Summer average epilimnetic concentrations of total phosphorus (TPe) have generally decreased in response to reductions in Metro's effluent concentrations.

“The summer average epilimnetic concentrations of TP (TP e ) have generally decreased (Fig. 7b) in response to reductions in Metro's effluent concentrations (Effler et al. 2005).”

• cites Effler et al. 2005 sourceSupported

Increased P loading from the Metro facility in 2003 and 2004 likely also contributed to higher AHOD values.

“Increased P loading from the Metro facility in 2003 and 2004 likely also contributed to higher AHOD values (Matthews et al. 2008).”

• cites Matthews et al. 2008 sourceSupported

The abrupt reduction in salinity following closure of the industry caused a shift to shorter durations of stratification.

“The abrupt reduction in salinity (S‰) following closure of the industry caused a shift to shorter durations of stratification (Effler and Owens 1996), and more regular occurrence of spring turnover (Fig. 7c and 7d; Owens and Effler 1989).”

• cites Effler and Owens 1996 sourceSupported

Most fish left Onondaga Lake in response to severe DO depletion during the 1991 event.

“Evidence for the exodus of most fish from the lake in response to severe DO depletion (seasonality in gill net collections, radio tagging results, and enclosure experiments) was developed during the 1991 event (Ringler et al. 1996, Tango and Ringler 1996).”

• cites Ringler et al. 1996Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Tango and Ringler 1996 sourcePartly supported

  The Refugia Effects on Fish Community Structure section (p. 9) reports that tagged fish moved into the Seneca River as dissolved oxygen declined in 1991, and that several species disappeared from autumn net catches. It does not establish that most individual fish left the lake: gizzard shad and alewife remained despite lakewide hypoxia. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

Dissolved P entrained into the upper productive layers from the enriched hypolimnion during the fall mixing period is not a concern for the subsequent year's summer stratification interval because it is either deposited or exported in the interim because of the lake's high flushing rate.

“The dissolved P entrained into the upper productive layers from the enriched hypolimnion during the fall mixing period is not a concern for the subsequent year's summer stratification interval because it is either deposited or exported in the interim because of the lake's high flushing rate (Effler et al. 2002).”

• cites Effler et al. 2002 sourceSupported

• AssumptionRests on an assumption: The lake's high flushing rate will continue to export or deposit dissolved P before the next summer stratification interval.

Reduced byproducts of anaerobic metabolism accumulated annually in the hypolimnion of Onondaga Lake.

“Reduced byproducts of anaerobic metabolism accumulated annually in the hypolimnion, causing low dissolved oxygen (DO) concentrations in the upper waters during fall turnover.”

Severe depletions of dissolved oxygen occurred annually in the upper waters of Onondaga Lake during fall mixing.

“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.”

Dissolved oxygen depletions during fall in Onondaga Lake were less severe from 1997 to 2004.

“Depletions of DO during fall were less severe from 1997 to 2004.”

The severe fall dissolved oxygen depletions in Onondaga Lake represented violations of water quality standards for extended intervals from 1978 to 1996.

“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.”

Internal loading of methylmercury from pelagic sediments of Onondaga Lake is indicated by hypolimnetic increases observed during intervals of anoxia.

“Internal loading of methyl Hg (CH3Hg + ), the primary bioaccumulating toxic form, from pelagic sediments is indicated by hypolimnetic increases that have been observed during intervals of anoxia (Bloom and Effler 1990, PTI Environmental Services 1994, Sharpe 2004).”

• cites Bloom and Effler 1990Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites PTI Environmental Services 1994Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Sharpe 2004Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Vertical dissolved oxygen profiles for early September of 1990 and 2003 depict anoxia in deeper portions of the water column.

“Vertical DO profiles are presented for early September of both years that depict anoxia in deeper portions of the water column.”

By mid-summer, the nitrate pool in Onondaga Lake had been eliminated through denitrification.

“the NO3 -pool had been eliminated through denitrification (Fig. 4b and c)”

By mid-summer, the hypolimnion of Onondaga Lake was anoxic.

“By mid-summer the hypolimnion of the lake was anoxic (Matthews and Effler 2006b) and the NO3 -pool had been eliminated through denitrification (Fig. 4b and c).”

• cites Matthews and Effler 2006bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

In 1990, an extended interval of about two weeks of violations of the minimum dissolved oxygen standard of 4 mg/L occurred.

“corresponding to an extended interval (~2 weeks) of violations of the minimum DO standard of 4 mg/L”

Time series of dissolved oxygen concentration that bound fall turnover depict an oxygen sag experienced annually in the upper waters of Onondaga Lake with the approach to fall turnover as hypolimnetic layers are entrained into the deepening epilimnion.

“Time series of DO concentration that bound fall turnover depict an 'oxygen sag' that is experienced annually in the upper waters of the lake with the approach to fall turnover as hypolimnetic layers are entrained into the deepening epilimnion (Fig. 3).”

Violations of the dissolved oxygen standard did not occur in 2003.

“Violations of the DO standard did not occur in 2003, and progressive increases were again observed following the onset of turnover.”

DO depletion was localized at the sediment-water interface, associated with the exertion of sediment oxygen demand (SOD).

“The DO depletion was localized at the sediment-water interface, associated with the exertion of sediment oxygen demand (SOD; Matthews and Effler 2006a).”

• cites Matthews and Effler 2006aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

A nearly linear decrease in the hypolimnetic mass of DO was observed in Onondaga Lake.

“A nearly linear decrease in the hypolimnetic mass of DO was observed in Onondaga Lake (Fig. 5a; Matthews and Effler 2006a) and many other lakes (Wetzel 2001).”

• cites Matthews and Effler 2006aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The AHOD values were similar for 1990 and 2004.

“The AHOD values were similar for 1990 and 2004 (Fig. 5a).”

Similar depletion rates of NO3- were observed for 1990 and 2004.

“Similar depletion rates of NO 3 -were observed for the two years.”

Decomposition processes were clearly operating in Onondaga Lake by mid-summer 1990, as manifested by the presence of CH4 and ∑S 2-.

“were clearly operating by mid-summer 1990 as manifested in the presence of CH4 and ∑S 2- (Fig. 4c).”

The fate of T-NH3, another potential source of oxygen demand, varied among years.

“The fate of the other potential source of oxygen demand, T-NH3, varied among years.”

Oxygen depletion was substantially more severe in 1990 than in 2003.

“Oxygen depletion was substantially more severe in 1990 (Fig. 3a), corresponding to an extended interval (~2 weeks) of violations of the minimum DO standard of 4 mg/L.”

Methanogenesis and sulfate reduction were clearly operating by mid-summer 1990 as manifested in the presence of methane and sulfide.

“Methanogenesis and SO4 2reduction were clearly operating by mid-summer 1990 as manifested in the presence of CH4 and ∑S 2- (Fig. 4c).”

The general AHOD pattern following closure was similar to that observed for CH4 accumulation rates and the CH4 oxygen demand through 2002.

“The general AHOD pattern following closure was similar to that observed for CH4 accumulation rates (Matthews et al. 2005, Matthews and Effler 2006a,) and the CH4 oxygen demand (Fig. 7h) through 2002.”

• cites Matthews et al. 2005 sourceNot checked — no full text of the source
• cites Matthews and Effler 2006aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The hypolimnetic accumulations of oxygen-demanding reduced byproducts of decomposition processes and the subsequent DO depletion during the approach to fall turnover were consistent for 1990 and 2004.

“The consistency between the hypolimnetic accumulations of oxygen-demanding reduced byproducts of decomposition processes and the subsequent DO depletion during the approach to fall turnover is depicted for 1990 and 2004 (Fig. 6).”

Decreases in CH4 flux from the sediments occurred following the abrupt decrease in POCdf.

“Decreases in CH4 flux from the sediments occurred following the abrupt decrease in POCdf .”

Areal hypolimnetic oxygen deficit values were higher before closure of the industry (average 2.1 g/m2/d).

“Areal hypolimnetic oxygen deficit values were higher before closure of the industry (average 2.1 g/m 2 /d; Fig. 7i).”

Violations of the DO standard in Onondaga Lake extended 20 or more consecutive days in four of the years during 1978-1996.

“The violations of the DO standard in the lake extended 20 or more consecutive days in four of these years (Fig. 3a; Matthews and Effler 2006b).”

• cites Matthews and Effler 2006bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The onset of anoxia has been extended to mid- to late June in most recent years.

“This has been extended to mid- to late June in most recent years (Fig. 7j).”

Substantial interannual variations in the occurrence and duration of spring turnover persist, at least in part associated with natural meteorological variability.

“Substantial interannual variations in the occurrence and duration of spring turnover persist, at least in part associated with natural meteorological variability (Owens and Effler 1989).”

• cites Owens and Effler 1989 sourceNot checked — no full text of the source

Failure of, or incomplete, spring turnover was observed in 1978, 1979, 1980, 1985, 1986, 1993, 1994, and 2001.

“Failure of, or incomplete, turnover was observed in 1978, 1979, 1980, 1985, 1986, 1993, 1994, and 2001 (Fig. 7d).”

Downward flux of particulate organic carbon (POCdf) showed systematic reductions for the lake (~37%) starting the year after closure of the soda ash industry.

“The shorter record of downward flux of particulate organic carbon (POCdf; Fig. 7e; Effler et al. 2001b) depicts systematic reductions for the lake (~37%) starting the year after closure of the soda ash industry.”

• cites Effler et al. 2001bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Another potential contributing factor to reductions in deposition was the return of large-bodied, salinity-intolerant native Daphnia following closure of the industry.

“Another potential contributing factor identified (Effler et al. 2001b) was the return of the large-bodied, salinity-intolerant native Daphnia following closure of the industry (Hairston et al. 2005).”

• cites Effler et al. 2001bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Hairston et al. 2005 sourceNot checked — no full text of the source

The observed oxygen deficit was 24% lower in 2004 than in 1990.

“the observed oxygen deficit was 24% lower”

The two lowest DOmin values occurred in 1978 and 1985.

“The two lowest DO min values occurred in 1978 and 1985; however, failure of spring turnover did not always result in severe DO depletion in fall, suggesting the importance of other mediating factors.”

The reduction in AHOD since the closure of the industry has been accompanied by an extension of the portion of the stratification interval that supports decomposition by aerobic metabolism.

“The reduction in AHOD since the closure of the industry has been accompanied by an extension of the portion of the stratification interval that supports decomposition by aerobic metabolism.”

Reductions in primary production and deposition were driven primarily by the decrease in salinity rather than reductions in P loading from Metro.

“Reductions in primary production and deposition were driven primarily by the decrease in S (Fig. 8c) rather than reductions in P loading from Metro (Effler et al. 2001b).”

• cites Effler et al. 2001bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The rapidly exerted oxygen debt component (CH4 plus ∑S 2-) was 40% lower in 2004 than in 1990.

“the rapidly exerted component (CH 4 plus ∑S 2) was 40% lower”

On average, DOmin values were significantly higher during 1997-2004 than during 1978-1996 (Welch t-test, p < 0.001).

“On average, DOmin values were significantly higher during 1997-2004 than during 1978-1996 (Welch t-test, p &lt; 0.001).”

The observed DO depletions in 1990 and 2004 were generally consistent with the antecedent oxygen debts represented by the hypolimnetic accumulations of reduced substances.

“Though this analysis is imperfect because it fails to accommodate other time varying sinks and sources of DO, it serves to demonstrate that the observed DO depletions in these two years were generally consistent with the antecedent oxygen debts represented by the hypolimnetic accumulations of these reduced substances.”

In 12 of the 19 years monitored during 1978-1996, DOmin was below the standard of 4 mg/L.

“In 12 of the 19 years monitored during the 1978-1996 period, DOmin was below the standard of 4 mg/L;”

Before closure, anoxia was established in the lowermost lake layers by early-to-late May.

“Before closure, anoxia was established in the lowermost lake layers by early-to-late May (Fig. 7j).”

The decreases in CH4 flux were manifested first as a decrease in the ebullitive component in 1992, without noteworthy change in the soluble oxygen-demanding diffusive component.

“These were manifested first as a decrease in the ebullitive component in 1992, without noteworthy change in the soluble oxygen-demanding diffusive component (Fig. 7g and 7h).”

Values of DOmin <2 mg/L were observed in 1978, 1985, 1990, 1991, and 1995.

“values of &lt;2 mg/L were observed in 1978, 1985, 1990, 1991, and 1995 (Fig. 7a).”

Relatively uniform POCdf fluxes were observed both before and after the abrupt decrease in salinity.

“Relatively uniform fluxes were observed both before and after the abrupt decrease in S .”

Interannual variations in the hypolimnetic accumulation rate of CH4 explained 46% (p = 0.01) of the variations in AHOD over the 1989 to 2002 interval.

“Matthews et al. (2005) reported that interannual variations in the hypolimnetic accumulation rate of CH4 explained 46% (p = 0.01) of the variations in AHOD over the 1989 to 2002 interval.”

• cites Matthews et al. 2005 sourceNot checked — no full text of the source

The absence of clear water phase maxima for the 2003-2005 interval, after 16 consecutive years of occurrence, reflects the loss of Daphnia associated with major increases in the alewife population.

“The absence of the clear water phase maxima for the 2003-2005 interval, after 16 consecutive years of occurrence, reflects the loss of Daphnia associated with major increases in the alewife population ( Alosa pseudoharengus ; an obligate and efficient planktivore; Brooks and Dodson 1965).”

• cites Brooks and Dodson 1965 sourceNot checked — no full text of the source

No violations of the 4 mg/L DO standard were observed from weekly sampling during 1997-2004.

“However, the status with respect to the DO standard has improved in recent years, with no violations of the 4 mg/L standard observed from weekly sampling during 1997-2004.”

Total potential oxygen debt was 53% lower in 2004 than in 1990.

“total potential debt was 53% lower”

The flux of the dissolved fraction, and its annual maximum DO demand, decreased in a generally progressive manner following the decrease in ebullition.

“The flux of the dissolved fraction, and its annual maximum DO demand (Fig. 7h), decreased in a generally progressive manner following the decrease in ebullition (Matthews et al. 2005).”

• cites Matthews et al. 2005 sourceNot checked — no full text of the source

Failure of spring turnover did not always result in severe DO depletion in fall.

“The two lowest DO min values occurred in 1978 and 1985; however, failure of spring turnover did not always result in severe DO depletion in fall, suggesting the importance of other mediating factors.”

More regular occurrence of spring turnover followed the abrupt reduction in salinity after closure of the industry.

“The abrupt reduction in salinity (S‰) following closure of the industry caused a shift to shorter durations of stratification (Effler and Owens 1996), and more regular occurrence of spring turnover (Fig. 7c and 7d; Owens and Effler 1989).”

• cites Owens and Effler 1989 sourceNot checked — no full text of the source

The ebullitive component decreased from 35 to 9% of the CH4 flux from before to after 1992.

“The ebullitive component decreased from 35 to 9% of the CH4 flux from before to after 1992 (Fig. 7g; Matthews et al. 2005).”

• cites Matthews et al. 2005 sourceNot checked — no full text of the source

Wide interannual variations in DOmin were observed.

“Wide interannual variations in DOmin were observed.”

A demonstration project that adopts NO3- as an electron acceptor to decrease SRB activity and methylation of Hg is essentially already underway associated with the discharge of large quantities of NO3- from Metro.

“A demonstration project that adopts NO3 -as an electron acceptor to decrease SRB activity and methylation of Hg is essentially already underway associated with the discharge of large quantities of NO 3 -from Metro.”

Overlap occurs in the populations of DOmin observations for the 1978-1996 and 1997-2004 intervals.

“For example, despite the substantial improvements, overlap occurs in the populations of observations for the 1978-1996 and 1997-2004 intervals (Fig. 7a).”

Relatively high ∑S2- oxygen demand was observed in other years of DO violations, including 1981, 1988, 1995.

“Relatively high ∑S 2- oxygen demand was observed in other years of DO violations, including 1981, 1988, 1995,”

An early sign of positive response to increased P treatment was the decrease in AHOD from 2003 and 2004 to 2005.

“An early sign of positive response to increased P treatment was the decrease in AHOD from 2003 and 2004 to 2005 (Fig. 7i), the first year of increased P treatment.”

The size of the ∑S2- pool has clearly been much more variable than the CH4 pool.

“The size of the ∑S 2pool has clearly been much more variable than the CH 4 pool.”

The ∑S2- oxygen demand was particularly high in 1985, the year the lowest DOmin was observed.

“The ∑S 2- oxygen demand was particularly high in 1985, the year the lowest DO min was observed.”

Benefits with respect to decreases in SO42- reduction and ∑S2 formation are already being observed.

“Benefits with respect to decreases in SO 4 2reduction and ∑S 2formation are already being observed, as reported here.”

Systematic improvements in DOmin and its drivers, in response to the closure of the primary industrial polluter and execution of early portions of the rehabilitation program for Metro, have been documented.

“Systematic improvements in DOmin and its drivers, in response to the closure of the primary industrial polluter and execution of early portions of the rehabilitation program for Metro, have been documented.”

Onondaga Lake responds rapidly to changes in external loading.

“The lake flushes rapidly, approximately 4 times per year on average (Effler 1996), and thereby responds rapidly to changes in external loading (Doerr et al. 1994, Effler et al. 2001a).”

• cites Doerr et al. 1994Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Effler et al. 2001aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Onondaga Lake flushes rapidly, approximately four times per year on average.

“The lake flushes rapidly, approximately 4 times per year on average (Effler 1996), and thereby responds rapidly to changes in external loading (Doerr et al. 1994, Effler et al. 2001a).”

• cites Effler 1996Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The high natural sulfate concentration of Onondaga Lake promoted dissolved oxygen depletion.

“The high natural sulfate (SO 4 2-) concentration of the lake promoted DO depletion and the production of methylmercury (CH 3 Hg + ).”

The accumulation of reduced byproducts of anaerobic metabolism caused low dissolved oxygen concentrations in the upper waters of Onondaga Lake during fall turnover.

“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 concentration of Onondaga Lake promoted production of methylmercury.

“The high natural sulfate (SO 4 2-) concentration of the lake promoted DO depletion and the production of methylmercury (CH 3 Hg + ).”

Through the late 1990s, the Metro input represented 80% of total nitrogen loading to Onondaga Lake.

“Through the late 1990s the Metro input represented 80% of the total nitrogen (N) loading (Matthews et al. 2001) and 80% of the effective ( i.e. , can support phytoplankton growth) P loading (Effler et al. 2002).”

• cites Matthews et al. 2001 sourceNot checked — no full text of the source

Prevailing dissolved oxygen conditions during fall turnover, particularly within the context of anticipated improvements from mandated upgrades, indicate that hypolimnetic aeration or oxygenation is not required to meet water quality goals.

“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.”

• AssumptionRests on an assumption: The mandated future upgrades of phosphorus and ammonia treatment at the wastewater facility will improve oxygen resources and decrease sulfate reduction in Onondaga Lake.

The improvement in fall dissolved oxygen depletion from 1997 to 2004 is attributable to more routine occurrence of spring turnover following closure of an industry.

“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.”

The improvement in fall dissolved oxygen depletion from 1997 to 2004 is attributable to reduction in primary productivity.

“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.”

Increased inputs of domestic and industrial wastes resulted in severe deterioration and loss of uses of Onondaga Lake.

“Increased inputs of domestic and industrial wastes that accompanied development of the watershed resulted in severe deterioration and loss of uses of the lake (Effler 1996).”

• cites Effler 1996Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

In 1990, the major reduction in T-NH3 and increase in NO3- with the onset of turnover reflect the operation of nitrification and the exertion of the associated oxygen demand.

“The major reduction in T-NH3 and increase in NO3 -with the onset of turnover (Fig. 4d and f) in 1990 reflect the operation of the nitrification process in that year, and the exertion of the associated oxygen demand [Eq. (3)], as substantiated by Gelda et al. (2000) through application of validated nitrogen and oxygen models.”

• cites Gelda et al. (2000)Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The hypereutrophic condition of Onondaga Lake caused rapid loss of oxygen from the hypolimnion.

“rapid loss of oxygen from the hypolimnion (Matthews and Effler 2006a)”

• cites Matthews and Effler 2006aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The much higher initial pool sizes of NO3- in April 2004 reflected the establishment of year-round nitrification treatment at Metro.

“The much higher initial pool sizes of NO3 - in April 2004 (Fig. 5b) reflected the establishment of year-round nitrification treatment at Metro.”

High salinity levels in Onondaga Lake eliminated large-bodied efficient grazing zooplankton (Daphnia).

“high salinity levels eliminated largebodied efficient grazing zooplankton ( Daphnia ; Hairston et al. 2005)”

• cites Hairston et al. 2005 sourceNot checked — no full text of the source

The mercury discharge resulted in extensive and continuing contamination of the biota, water column, and sediments of Onondaga Lake.

“resulting in extensive and continuing contamination of the biota (Effler 1996), water column (Bloom and Effler 1990), and sediments (NYSDEC 2004) of the lake.”

• cites Effler 1996Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Bloom and Effler 1990Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites NYSDEC 2004Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Marked progressive increases in total ammonia with depth within the hypolimnion reflect production as a byproduct of both aerobic and anaerobic metabolism.

“Marked progressive increases in T-NH 3 with depth within the hypolimnion (Fig. 4b) reflect production as a byproduct of both aerobic and anaerobic metabolism.”

The primary industrial polluter of Onondaga Lake was a chemical manufacturing facility that operated during 1884-1986 along the western shore.

“The primary industrial polluter of the lake was a chemical manufacturing facility that operated during 1884-1986 along the western shore (Fig. 2a).”

Metro's phosphorus load caused Onondaga Lake to be hypereutrophic.

“Metro's P load caused the lake to be hypereutrophic, which was manifested as: (1) severe phytoplankton blooms including nuisance cyanobacteria; (2) poor water clarity; (3) rapid loss of oxygen from the hypolimnion (Matthews and Effler 2006a);”

Differences in the timing of the peak pool sizes for ∑S 2- and CH4 between 1990 and 2004 (mid-September vs. late September) reflect interannual differences in the mixing/stratification regime (meteorology).

“Differences in the timing of the peak pool sizes for both ∑S 2- (Fig. 5c) and CH 4 (Fig. 5d) between the two years (mid-September vs. late September) reflect the effects of interannual differences in the mixing/stratification regime ( i.e. , meteorology; Owens and Effler 1989).”

• cites Owens and Effler 1989 sourceNot checked — no full text of the source

High calcium concentrations promoted increased phytoplankton production in Onondaga Lake through enhanced deposition of phytoplankton.

“high Ca 2+ promoted increased phytoplankton production through enhanced deposition of phytoplankton (Effler et al. 2001b)”

• cites Effler et al. 2001bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The monitoring site in Onondaga Lake's southern basin near its maximum depth is generally representative of lake-wide conditions.

“All data presented here were collected from a site in Onondaga Lake's southern basin near its maximum depth (19.5 m; Fig. 2), a site generally representative of lake-wide conditions (Effler 1996).”

• cites Effler 1996Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Approximately 75,000 kg of mercury were discharged to Onondaga Lake by the chemical manufacturing industry associated with chlor-alkali manufacture.

“Approximately 75,000 kg of Hg were discharged to the lake by this industry associated with chlor-alkali manufacture (USEPA 1973)”

• cites USEPA 1973Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The substrates for methanogenesis are older and more recalcitrant.

“Accordingly, the substrates for methanogenesis are older and more recalcitrant (Matthews et al. 2005).”

• cites Matthews et al. 2005 sourceNot checked — no full text of the source

The rate of methanogenesis should be expected to be insensitive to seasonal variations in the downward flux of organic material from the productive layers.

“Thus the rate of this process should be expected to be insensitive to seasonal variations in the downward flux of organic material from the productive layers.”

The coincidence with the major increase in the alewife population and coupled loss of large-bodied Daphnia suggest these food web effects contributed to increased deposition of particulate organic material in 2003 and 2004.

“The coincidence with the major increase in the alewife population and coupled loss of large-bodied Daphnia suggest these food web effects contributed to increased deposition of particulate organic material in 2003 and 2004.”

The return of the 2005 AHOD to the earlier lower level may depict compensation for these food web effects by decreased primary production from decreased Metro P loading that commenced in early spring 2005.

“The return of the 2005 AHOD to the earlier lower level may depict compensation for these food web effects by decreased primary production from decreased Metro P loading that commenced in early spring 2005.”

The time course of the decrease in CH4 flux, and the associated DO demand, following the decrease in POCdf depicts feedback from sediments deposited during earlier more productive years.

“The time course of the decrease in CH4 flux, and the associated DO demand (Fig. 7h), following the decrease in POCdf (Fig. 7e), depicts feedback from sediments deposited during earlier more productive years (Matthews et al. 2005).”

• cites Matthews et al. 2005 sourceNot checked — no full text of the source

The nearly equal AHOD values for 1990 and 2004 suggest a compensating higher rate of deposition of organic matter in 2004, at least during the interval of aerobic decomposition.

“Assuming the upward flux of CH 4 via the sediment pore waters is essentially equal to the CH4 accumulation rate (Gelda et al. 1995), adjusted for vertical mixing (Matthews et al. 2005), the nearly equal AHOD values for the two years suggest a compensating higher rate of deposition of organic matter in 2004, at least during the interval of aerobic decomposition.”

• AssumptionThe authors state this as an assumption: The upward flux of CH4 via the sediment pore waters is essentially equal to the CH4 accumulation rate, adjusted for vertical mixing.

The much lower initial T-NH3 pool size in 2004 was a result of effective nitrification treatment at Metro over the preceding winter months.

“The much lower initial pool size of 2004 was a result of effective nitrification treatment at Metro over the proceeding winter months ( e.g. , lower effluent T-NH3 concentrations, consistent with the ACJ).”

More regular spring turnover is more important in this system because it determines whether the lower layers are replenished with oxygen and NO3- following winter stratification under the ice.

“The latter effect is more important in this system because it determines whether the lower layers are replenished with oxygen and NO 3 -following winter stratification under the ice (Effler and Perkins 1987).”

• cites Effler and Perkins 1987 sourceNot checked — no full text of the source

Other mediating factors are important in determining severe DO depletion in fall.

“The two lowest DO min values occurred in 1978 and 1985; however, failure of spring turnover did not always result in severe DO depletion in fall, suggesting the importance of other mediating factors.”

The changes in oxygen debt components between 1990 and 2004 are not proportional because factors not accommodated in the simple budget analysis may differ year to year.

“These changes are not proportional because factors not accommodated in this simple budget analysis may differ year to year (subsequently).”

Monitoring supported the estimate of ∑S2- oxygen demand for six years before CH4 measurements commenced.

“Monitoring supported the estimate of ∑S 2- oxygen demand for six years before CH 4 measurements commenced.”

The shorter durations of stratification reduced the interval of isolation of the hypolimnion from sources of oxygen.

“The first of these features reduced the interval of isolation of the hypolimnion from sources of oxygen.”

A likely source of unexplained variations in AHOD is year-to-year differences in the deposition of new particulate organic material.

“Since this CH 4 flux is arguably associated with SODd (older deposits; see Fig. 1), a likely source of unexplained variations is year-to-year differences in the deposition of new ( e.g. , that year) particulate organic material.”

Large-bodied, salinity-intolerant native Daphnia produce rather diffuse egestion products that settle slowly and are more subject to recycle within the upper productive layers than the waste material from other zooplankton.

“These cladocerans produce rather diffuse egestion products that settle slowly and are more subject to recycle within the upper productive layers than the waste material from other zooplankton (Evans et al. 1998).”

• cites Evans et al. 1998 sourceNot checked — no full text of the source

The oxygen demand of the annual maximum ∑S2- accumulation and the oxygen demand time series for CH4 together represent the certain (and rapid) portion of the oxygen debt to be satisfied during the fall mixing interval.

“The oxygen demand of the annual maximum ∑S 2- accumulation is presented with the oxygen demand time series for CH 4 (Fig. 7h) because together these represent the certain (and rapid) portion of the oxygen debt to be satisfied during the fall mixing interval.”

The high levels of CH3Hg+ that have developed in Onondaga Lake's hypolimnion are consistent with the large supply of organic substrate, the prevalence of anaerobic conditions, and high concentrations of SO42-.

“The high levels of CH 3 Hg + that have developed in Onondaga Lake's hypolimnion (Bloom and Effler 1990, PTI Environmental Services 1994, Sharpe 2004) are consistent with the large supply of organic substrate, the prevalence of anaerobic conditions, and high concentrations of SO 4 2.”

• cites Bloom and Effler 1990Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites PTI Environmental Services 1994Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Sharpe 2004Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Forthcoming improvements from rehabilitation elements will cause a shift in the distribution of DOmin to higher values.

“Forthcoming improvements from rehabilitation elements (Table 1) will cause a shift in the distribution of DOmin to higher values, but substantial overlap with existing conditions should be expected.”

Recent (2005 and 2006) reductions in Metro P loading have resulted in decreases in primary production.

“For example, recent (2005 and 2006) reductions in Metro P loading have resulted in decreases in primary production (Effler 2007).”

• cites Effler 2007Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Substantial overlap with existing DOmin conditions should be expected after forthcoming improvements.

“but substantial overlap with existing conditions should be expected.”

External inputs of CH3Hg+ are insufficient to account for its accumulation in sediments and biota in most systems, establishing internal production as the dominant source in these cases.

“Further, external inputs of CH 3 Hg + are insufficient to account for its accumulation in sediments and biota in most systems, establishing internal production as the dominant source in these cases (Benoit et al. 2001).”

• cites Benoit et al. 2001Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

The primary sources of future interannual variability in DOmin will be natural variations in photosynthetic and atmospheric inputs of oxygen and shifts in food web effects.

“The primary sources of this variability will be natural variations in photosynthetic and atmospheric inputs of oxygen and shifts in food web effects;”

Sulfate stimulates CH3Hg+ production by promoting the activity of SO42--reducing bacteria, the principal methylators of inorganic Hg in freshwater sediments.

“Sulfate stimulates CH 3 Hg + production by promoting the activity of SO 4 2-reducing bacteria (SRB; Gilmour et al. 1992), the principal methylators of inorganic Hg in freshwater sediments (Benoit et al. 2003).”

• cites Gilmour et al. 1992 sourceNot checked — no full text of the source
• cites Benoit et al. 2003Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Control of internal P loading from pelagic sediments currently is not a noteworthy issue in the context of Onondaga Lake's cultural eutrophication problems.

“Thus, control of internal P loading from pelagic sediments currently is neither a noteworthy issue in the context of the lake's cultural eutrophication problems nor a stated goal of the ACJ (1997).”

A sediment injection procedure resulted in the oxidation of the upper 15-20 cm of anaerobic lake sediment.

“A sediment injection procedure resulted in the oxidation of the upper 15-20 cm of anaerobic lake sediment (Ripl 1976).”

• cites Ripl 1976Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Additional improvements in DOmin are anticipated from forthcoming treatment upgrades at Metro.

“Further, additional improvements in DOmin are anticipated from the forthcoming treatment upgrades at Metro.”

• AssumptionRests on an assumption: Forthcoming treatment upgrades at Metro will be implemented as planned.

Lasting reductions in SOD were reported at one application site eight years later.

“Lasting reductions in SOD were reported at one application site eight years later (Ripl 1976).”

• cites Ripl 1976Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Losses of added NO3- were reported to be almost entirely in the form of N2 gas.

“Losses of added NO 3 -were reported to be almost entirely in the form of N 2 gas.”

• cites Ripl 1976Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Ripl 1981Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Ripl and Lindmark 1978Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Review of related literature does not provide an a priori basis to select either oxygenation or NO3- addition as preferred to reduce hypolimnetic accumulation of CH3Hg+.

“Review of related literature does not provide an a priori basis to select either of these general approaches as preferred to reduce hypolimnetic accumulation of CH 3 Hg + .”

Deep-water discharge of NO3--rich effluents would be expected to prevent or reduce SO42- reduction and the production of ∑S2.

“This would also be expected to prevent or reduce SO 4 2reduction and the production of ∑S 2.”

The greater variability of the ∑S2- pool is consistent with the vertical limits of SO4 2- reduction in the sediments that restricts decomposition via this metabolic pathway to more recently deposited organic material.

“This is consistent with the vertical limits of SO 4 2reduction in the sediments (Fig. 1) that restricts decomposition via this metabolic pathway to more recently deposited organic material.”

Oxygenation appears unnecessary to routinely meet the ACJ requirements.

“Although oxygenation appears unnecessary to routinely meet the ACJ requirements, other possible attributes need to be considered, such as potential reductions in internal loading of P and CH3 Hg + .”

Continued wide interannual variations in DOmin, such as observed since 1997, are anticipated in the future.

“Continued wide interannual variations in DOmin, such as observed since 1997, are anticipated in the future.”

The addition of NO3- as Ca(NO3)2 to prevent or abate P release from pelagic sediments within anoxic hypolimnia was developed and tested by Ripl and coworkers and also applied by others.

“The addition of NO3 - , in the form of Ca(NO 3 ) 2 , as treatment to prevent or abate P release from pelagic sediments within anoxic hypolimnia was developed and tested by Ripl and coworkers (Ripl 1976, 1981, Ripl and Lindmark 1978) and also applied by others (Willenbring et al. 1984, Foy 1986).”

• cites Ripl 1976Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Ripl 1981Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Ripl and Lindmark 1978Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

NO3- addition represents the continuation and extension of an ongoing management action, manifested in the high NO3- concentration of the effluent presently being discharged to the lake from Metro.

“Perhaps the most compelling support for such an approach is that it represents the continuation and extension of an ongoing management action, manifested in the high NO3 - concentration of the effluent presently being discharged to the lake from Metro.”

NO3- addition likely could be more easily implemented on an irregular, as-needed basis, guided by monitoring of the hypolimnetic NO3- pool.

“Further, it likely could be more easily implemented on an irregular, as-needed basis, guided by monitoring of the hypolimnetic NO3 - pool.”

The positive changes in drivers that have caused improvements in DOmin should be lasting, except for food web effects.

“The positive changes in drivers that have caused improvements in DOmin (Table 1) should be lasting, with the exception of the food web effects ( e.g. , Daphnia /alewives).”

Anthropogenic impacts on the metabolism of both trophogenic and tropholytic zones of Onondaga Lake, particularly within the context of oxygen resources and redox processes, are central features of both observed degradations and proposed rehabilitation measures.

“Anthropogenic impacts on the metabolism of both trophogenic and tropholytic zones of this urban lake, particularly within the context of oxygen resources and redox processes, are central features of both observed degradations and proposed rehabilitation measures.”

Anticipated benefits of recent and future rehabilitation actions could result in aerobic and denitrification pathways being adequate to stabilize inputs of decomposable organics, thereby eliminating SO42- reduction.

“Anticipated benefits of recent and future rehabilitation actions (Table 1) could result in aerobic and denitrification pathways being adequate to stabilize inputs of decomposable organics, thereby eliminating SO4 2- reduction.”

Higher temperatures of the hypolimnion that would accompany increased mixing from aeration/oxygenation could increase methylation rates.

“Additionally, higher temperatures of the hypolimnion that would accompany increased mixing from aeration/oxygenation could increase methylation rates (Bodaly et al. 1993, Ramlal et al. 1993).”

• cites Bodaly et al. 1993 sourceNot checked — no full text of the source
• cites Ramlal et al. 1993 sourceNot checked — no full text of the source

Prevailing DOmin conditions and the anticipated improvements indicate aeration/oxygenation is not needed to meet the requirements of the enforcement action related to domestic waste (ACJ).

“Prevailing DO min conditions and the anticipated improvements indicate aeration/oxygenation is not needed to meet the requirements of the enforcement action related to domestic waste (ACJ).”

These improvements would at least reduce the amount of NO3- necessary to add to the hypolimnion to abate SRB metabolism.

“These improvements would at least reduce the amount of NO3 -necessary to add to the hypolimnion to abate SRB metabolism.”

The observed benefits in delayed SO42- reduction manifested following increases in the hypolimnetic pool of NO3- support an approach of additional increases in this pool to abate SRB-mediated accumulations of CH3Hg+ in the hypolimnion.

“The observed benefits in delayed SO 4 2reduction manifested following increases in the hypolimnetic pool of NO 3 -support an approach of additional increases in this pool to abate SRB-mediated accumulations of CH3Hg + in the hypolimnion.”