Long-term nitrate removal in a denitrification wall

May combine two claims.

Under moderate loading rates, removal in small streams decreases because they are oversupplied with N, but larger streams begin to respond in terms of denitrification and N export decreases.

“Under moderate loading rates, removal in small streams decreases because they are oversupplied with N, but the larger streams begin to respond in terms of denitrification and N export decreases.”

• cites Mulholland et al., 2008 sourceDisputed

  The paper’s stream-network modeling discussion supports the claim that, at moderate loading, removal efficiency falls in smaller streams while removal in larger streams responds. But it says this limits N export, not that export decreases. The same discussion states that downstream nitrate export increases as loading rises. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Regulations in New Zealand limit effluent applied to pastures to 150-200 kg N ha-1 yr-1 as the maximum to minimize potential leaching loss of NO3- to groundwater.

“Regulations have been created in New Zealand to limit the amount of effluent that can be applied to pastures; 150 -200 kg N ha -1 yr -1 is the maximum application to minimize potential leaching loss of NO 3 -to the groundwater (Wang et al., 2004).”

• cites Wang et al., 2004 sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

NH4+ is highly volatile and waste application can lead to N loss through NH3 volatilization.

“NH 4 + is highly volatile and waste application can lead to N loss through NH 3 volatilization (Wang et al., 2004).”

• cites Wang et al., 2004 sourcePartly supported

  The “Odours and gaseous emissions” section says that ammonia volatilisation during and after farm-effluent application can cause significant nitrogen loss. It identifies ammonium-N as a major component of treated effluent, but does not say that NH4+ itself is highly volatile; it describes the volatile loss as ammonia. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Land application of farm effluents is being encouraged in New Zealand and waste stabilization ponds are slowly being phased out.

“As a potential solution to this problem, land application of farm effluents is being encouraged in New Zealand and the waste stabilization ponds are slowly being phased out (Wang et al., 2004).”

• cites Wang et al., 2004 sourcePartly supported

  The Introduction says New Zealand regional councils encourage land application of farm effluents. It says that direct discharge of effluent from ponds to surface water has been gradually phased out, not that waste stabilisation ponds themselves are being phased out. The supplied passage has no page number. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

Classified as probably not a substantial claim. May combine two claims.

Robertson et al. (2008) took cores from the denitrification wall and then ran NO3- through them in a lab; a full field sampling was not undertaken.

“Robertson et al. (2008) took cores from the denitrification wall and then ran NO 3 -through them in a lab; a full field sampling was not undertaken.”

• cites Robertson et al., 2008 sourcePartly supported

  Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured

May combine two claims.

Wetlands promote denitrification, but incomplete denitrification can lead to increased N2O emissions when NO3- concentrations are high, shifting the problem from water pollution to greenhouse gas emission.

“Wetlands promote denitrification, but incomplete denitrification can lead to increased N 2 O emissions when NO 3 -concentrations are high, thereby shifting the problem from water pollution to greenhouse gas emission (Zaman et al., 2008).”

• cites Zaman et al., 2008 sourceSupported

May combine two claims.

Streams have a high capacity for denitrification, but often have low denitrification efficiency during the period of the year when they receive high flow and high NO3-.

“While streams have a high capacity for denitrification, they often have low denitrification efficiency during the period of the year where they receive high flow and high NO 3 - (Royer et al., 2004;Mulholland et al., 2008).”

• cites Royer et al., 2004 sourceNot checked — no full text of the source
• cites Mulholland et al., 2008 sourcePartly supported

  The paper reports that streams can be important nitrate sinks and that denitrification efficiency declines as nitrate concentration increases (main text, passages 6–7). It does not establish that this occurs during a particular high-flow, high-nitrate period of the year; the main text (passage 4) explicitly says seasonal and discharge-related variation was not addressed. Page numbers are not provided in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

At low N loading rates, N removal is high in small streams, but is limited in large streams due to N availability.

“Mulholland et al. (2008) describes the effects of stream size and N loading rates: at low N loading rates, N removal is high in small streams, but is limited in large streams due to N availability.”

• cites Mulholland et al., 2008 sourceSupported

May combine two claims.

At high loading rates, removal becomes ineffective across all stream sizes and the stream network exports most of the N input.

“At high loading rates, removal becomes ineffective across all stream sizes and the stream network exports most of the N input.”

• cites Mulholland et al., 2008 sourceSupported

May combine two claims.

The Canada denitrification wall constructed from 20% sawdust mixed with soil still removed NO3 after 15 years, with near-complete NO3 removal over time.

“The only other decadal study to date demonstrated that a denitrification wall constructed in Ontario, Canada from 20% sawdust mixed with soil (Robertson and Cherry, 1995) still removed NO 3 -after 15 years (Robertson et al., 2008).Input NO 3 -concentrations in the Canada wall ranged from <2 mg N L -1 up to 100 mg N L -1 over the 15 years of performance and the wall achieved near-complete NO 3 -rem”

• cites Robertson et al., 2008 sourceSupported

May combine two claims.

The only decadal study of NO3 removal in a denitrification wall was performed in Canada, which showed continued effectiveness in NO3 removal after 15 years.

“The only decadal study of NO 3 removal in a denitrification wall was performed in Canada, which showed continued effectiveness in NO 3 -removal after 15 years (Robertson et al., 2008).”

• cites Robertson et al., 2008 sourcePartly supported

  The Introduction describes 15 years of monitoring at a barrier in southern Ontario, and Long-Term Barrier Performance reports relatively complete nitrate removal over that period. But the Introduction says “few if any decadal studies” were available; it does not establish that this was the only one. Page numbers are unavailable in our copy. (LLM, conf=0.88)

  Experimental — accuracy not yet measured

May combine two claims.

Robertson et al. (2008) found that denitrification walls were still effective after 15 years, and a denitrification wall constructed in Canada was effective after 15 years.

“Moorman et al. (2010) and Robertson et al. (2008) which found that denitrification walls were still effective after 9 years and 15 years respectively.”

• Also stated in: § 4.2 Future Research · plain

  “A denitrification wall constructed in Canada was effective after 15 years (Robertson et al., 2008)”

• cites Robertson et al. (2008) sourceSupported
• cites Robertson et al., 2008 sourceSupported

May combine two claims. The quote only partly states this claim.

Groundwater NO3- concentrations entering the denitrification wall averaged 2.6 mg N L-1 in winter 2010, a decrease from an average of 9 mg N L-1 in 2002.

“Groundwater NO 3 -concentrations entering the wall averaged 2.6 mg N L -1 , which was a decrease from 2002 where NO 3 -entered the wall at an average of 9 mg N L -1 .”

May combine two claims.

Available C within the wall decreased significantly between year 1 and year 2, but did not significantly decline thereafter, averaging 1.9 μg C g-1 hr-1 (SE 0.21) in year 14.

“Available C within the wall significantly decreased between the first and second year of operation (from 5.4 µg C g -1 hr -1 with a SE of 0.49 to 2.3 µg C g -1 hr -1 with a SE of 0.21; p = 0.04), but has not significantly declined since (with an average of 1.9 µg C g -1 hr -1 and a SE of 0.21 in year 14; Figure 3.5).”

May combine two claims.

The denitrification wall in this study remained effective for 14 years, where more than 90% of NO3 input was removed.

“The denitrification wall in this study remained effective for 14 years, where more than 90% of NO 3 -input was removed.”

May combine two claims.

DEA averaged 695 ng N g-1 hr-1 (SE 82; excluding June) in year 14, similar to the year 1 average of 740 ng N g-1 hr-1 (SE 72).

“Over 3 months of measurement in year 14, DEA averaged 695 ng N g -1 hr -1 (SE of 82; excluding June), which was similar to year 1 (average of 740 ng N g -1 hr -1 , SE of 72).”

May combine two claims.

DEA rates after 14 years were similar to those measured in year 1, and denitrification rates were nearly as high as when the wall was initially installed.

“We found that DEA rates after 14 years were similar to those measured in year 1”

• Also stated in: § 3.6 Conclusions · plain

  “Denitrification rates (using DEA as an index) were found to be nearly as high as they were when the denitrification wall was initially installed.”

May combine two claims.

The denitrification wall was still removing 92% of NO3 input, and 92% NO3 removal from groundwater was found in year 14.

“the denitrification wall was still removing 92% of NO 3 -input”

• Also stated in: § 4.1 Conclusions · plain

  “I found 92% NO 3 -removal from groundwater, high rates of DEA, and continued supply of available C in year 14.”

May combine two claims.

After 14 years, the denitrification wall removed 92% of NO3 input, which ranged from 2.2 to 3.7 mg N L-1.

“After 14 years, the denitrification wall removed 92% of NO 3 -input, which ranged from 2.2 to 3.7 mg N L -1 .”

May combine two claims.

Groundwater within the wall had a NO3 concentration of 0.2 mg N L-1 (SE 0.04) in year 14, corresponding to 92% removal, similar to 91% removal over the first 5 years.

“Groundwater within the wall had a NO 3 -concentration of 0.2 mg N L -1 (SE of 0.04) in year 14 corresponding to 92% removal, similar to the 91% removal measured over the first 5 years (Figure 3.3).”

May combine two claims.

Groundwater NO3 input to the wall averaged 2.6 mg N L-1 (SE 0.4) in year 14, significantly less (p = 0.01) than the average of 9 mg N L-1 (SE 0.7) over the first 5 years after installation.

“Groundwater NO 3 -input averaged 2.6 mg N L -1 (standard error (SE) of 0.4) in year 14, which was significantly less (p = 0.01) than an average of 9 mg N L -1 (SE of 0.7) through the first 5 years after the wall was installed.”

May combine two claims.

NO3 entered the wall at a concentration of 2.6 mg N L-1 and declined to 0.2 mg N L-1 within the wall.

“NO 3 -entered the wall at a concentration of 2.6 mg N L -1 and declined to 0.2 mg N L -1 within the wall”

May combine two claims.

Available C had plateaued and was not useful in predicting C decline into the future.

“available C had plateaued and was not be useful in predicting C decline into the future”

Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based).

DEA is greater lower in the denitrification wall.

“Total C, available C, and DEA are greater lower in the denitrification wall.”

May combine two claims.

A first order C decay curve fitted to total C data from the previous 14 years predicted total C to 0.1% of soil in year 66 with a prediction interval of (0.04%, 0.264%) (R2 = 0.92; p < 0.05); total C in the New Zealand denitrification wall will not be depleted for a total 66 years, and will not decline below 0.1% for another 52 years.

“A first order C decay curve was fitted to the total C data from the previous 14 years (Schipper and Vojvodic-Vukovic, 1998;2001) where total C was predicted to 0.1% of soil in year 66 with a prediction interval of (0.04%, 0.264%) (R 2 = 0.92; p < 0.05).”

• Also stated in: § 3.6 Conclusions · plain

  “We predicted that the total C in the New Zealand denitrification wall will not be depleted for a total 66 years”

• Also stated in: § 4.1 Conclusions · hedged

  “I predicted that the total C in the denitrification wall would not decline below 0.1% for another 52 years (66 years in total).”

• cites Schipper and Vojvodic-Vukovic, 1998 sourceNot checked — no full text of the source
• cites Schipper and Vojvodic-Vukovic, 2001 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Long-term manure applications change the chemical, physical, and biological properties of soil, which could alter nutrient release patterns.

“Furthermore, the chemical, physical, and biological properties of soil are changed by long-term manure applications, which could alter nutrient release patterns (Whalen et al., 2001).”

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

May combine two claims.

The right conditions exist in shallow groundwater to promote denitrification, except that there is insufficient organic C available to stimulate dissolved O2 and NO3- reduction.

“Examination of denitrification in a range of ecosystems, suggests that the right conditions exist in shallow groundwater to promote denitrification, except that there is insufficient organic C available to stimulate dissolved O 2 and NO 3 -reduction (Seitzinger et al., 2006).”

• cites Seitzinger et al., 2006 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Through nitrification, NH4+ is oxidized to NO3-, which can potentially be leached into downstream water bodies causing eutrophication or lead to N2O emissions, a greenhouse gas.

“Through the process of nitrification, NH 4 + is oxidized to NO 3 -, which can potentially be leached into downstream water bodies causing eutrophication or it can lead to N 2 O emissions, a greenhouse gas (Camargo and Alonso, 2006).”

• cites Camargo and Alonso, 2006 sourceNot checked — no full text of the source

May combine two claims.

Denitrification walls are cost-effective solutions to removing NO3- from groundwater because they can be effective for a number of years without maintenance.

“This long-term study suggested that denitrification walls are cost-effective solutions to removing NO 3 -from groundwater as they can be effective for a number of years without any maintenance.”

• AssumptionRests on an assumption: Denitrification walls are low-cost and low-maintenance.
• AssumptionRests on an assumption: The denitrification wall at Bardowie Farm is representative of denitrification walls generally.

May combine two claims.

Approximately the first 50 cm in the soil profile can become quite dry and aerobic during summer months, which would increase sawdust decomposition.

“Approximately the first 50 cm in the soil profile can become quite dry and aerobic during summer months which would increase sawdust decomposition (Schipper and Vojvodic-Vukovic, 2001)”

• cites Schipper and Vojvodic-Vukovic, 2001 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

A number of approaches have been investigated to increase the availability of C to denitrifying bacteria in soils and shallow aquifers.

“A number of approaches have been investigated to increase the availability of C to denitrifying bacteria in soils and shallow aquifers (Schipper et al., 2010a).”

• cites Schipper et al., 2010a sourceNot checked — no full text of the source

May combine two claims.

To promote denitrification, there needs to be an absence of O2, NO3- available as an electron acceptor, and labile carbon (C) to act as an energy source for the denitrifying microbes.

“To promote denitrification, there needs to be an absence of O 2 , NO 3 available as an electron acceptor, and labile carbon (C) to act as an energy source for the denitrifying microbes (Soares, 2000).”

• cites Soares, 2000 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Manure from livestock operations is applied to lands near the farm dairy shed, leading to high frequency and high rates of application to the same land.

“In general, the manure from livestock operations is applied to lands in the near vicinity of the farm dairy shed, which tends to lead to high frequency and high rates of application to the same land (Whalen et al., 2001).”

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

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Irrigation of dairy effluents up to 150-200 kg N ha-1 can add large amounts of potassium to soil, increasing potassium uptake by pasture and causing calcium and magnesium deficiencies that increase milk fever and grass staggers in livestock.

“Bolan et al. (2004) observed that irrigation of dairy effluents up to 150 -200 kg N ha -1 can result in large amounts of potassium (K) being added to the soil, in turn increasing K uptake by pasture; this results in calcium and magnesium deficiencies increasing the occurrence of milk fever and grass staggers in livestock.”

• cites Bolan et al., 2004 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S2 (checkable).

More information is needed on long-term performance of denitrification walls in a wide variety of settings.

“More information is needed on long-term performance in wide variety of settings.”

Classified as probably not a substantial claim.

Long-term data on the efficacy of denitrification walls remain limited.

“however, long-term data on the efficacy of denitrification walls remain limited.”

Classified as probably not a substantial claim.

Previous work showed a substantial decline in denitrifying enzyme activity (DEA) after 5-7 years in this wall.

“Although previous work showed a substantial decline in denitrifying enzyme activity (DEA) after 5 -7 years in this wall, (Schipper and Vojvodic-Vukovic, 2001;Schipper et al., 2005)”

• cites Schipper and Vojvodic-Vukovic, 2001 sourceNot checked — no full text of the source
• cites Schipper et al., 2005 sourceNot checked — no full text of the source

Classified as probably not a substantial claim.

Denitrification rates in the wall remained high enough to support significant NO3- removal.

“they also found that denitrification rates in the wall remained high enough to support significant NO 3 -removal.”

• cites Schipper and Vojvodic-Vukovic, 2001 sourceNot checked — no full text of the source
• cites Schipper et al., 2005 sourceNot checked — no full text of the source

May combine two claims.

Denitrification in agricultural streams tends to be C limited as NO3- concentrations are generally high.

“Denitrification in agricultural streams tends to be C limited as NO 3 -concentrations are generally high (Inwood et al., 2007).”

• cites Inwood et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

Denitrification at the Rotorua forest site was limited by low moisture content of the soil because there should have been enough C present for denitrification to occur.

“Denitrification at this site was limited by low-moisture content of the soil because there should have been enough C present for denitrification to occur (Barton et al., 1999).”

• cites Barton et al., 1999 sourceNot checked — no full text of the source

May combine two claims.

In the experimental field, the two-year average denitrification rate ranged from 11-37% of applied N, but higher denitrification coincided with higher N2O evolution; average N2O production over the four quadrants was 29% of denitrification.

“In this case, the two year average rate of denitrification ranged from 11 -37% of the applied N, however, the higher rates of denitrification also coincided with higher rates of N 2 O evolution; the average N 2 O production over the four quadrants was 29% of denitrification.”

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

May combine two claims.

Plant biomass as an additional C source in artificial marshes resulted in NO3-removal lower than methanol at 91%, but the biomass was produced on site and reduced costs.

“While NO 3 -removal was lower than when methanol was added at 91%, the biomass was produced on site and reduced costs.”

• cites Gersberg et al., 1983 sourceNot checked — no full text of the source

May combine two claims.

Denitrification is the only way to permanently remove NO3- from ecosystems, although the production of N2O during the process can contribute to atmospheric problems.

“Denitrification is the only way to permanently remove NO 3 -from ecosystems, although the production of N 2 O during the process can contribute to atmospheric problems.”

May combine two claims.

Artificial drainage of agricultural fields can increase crop yields and reduce the risk of saturated soils and ponding, but the drainage water tends to be high in nutrients from fertilizer application.

“Artificial drainage of agricultural fields can increase crop yields and reduce the risk of saturated soils and ponding on fields (Strock et al., 2007), but the drainage water tends to be high in nutrients from fertilizer application.”

• cites Strock et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

A high water table may stimulate denitrification, but the anaerobic conditions can damage plant roots and decrease yields.

“The disadvantage in terms of crop production is that while a high water table may stimulate denitrification, the anaerobic conditions can damage plant roots and decrease yields (Jacinthe et al., 1999).”

• cites Jacinthe et al., 1999 sourceNot checked — no full text of the source

May combine two claims.

These pathways are not permanent N sinks; only denitrification or anammox completes the cycle back to N2 gas.

“These pathways are not permanent N sinks; only denitrification or anammox completes the cycle back to N 2 gas.”

May combine two claims.

NO3-removal from agricultural streams occurs through denitrification as well as microbial and plant uptake.

“NO 3 -removal from agricultural streams occurs through denitrification as well as microbial and plant uptake (Strock et al., 2007).”

• cites Strock et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

An N budget using natural abundance 15N tracers showed that about 50% of added N was stored in the forest, 13% in wetland biomass, and only 2% was denitrified.

“An N budget of the system measured with natural abundance 15 N tracers showed that about 50% of the added N was stored in the forest, the majority in the soil, while 13% was stored in wetland biomass, and only 2% was denitrified (Tozer et al. 2005).”

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

Probably not a substantial claim: may not pass S3 (load-bearing).

C is often the limiting factor for denitrification in wetlands because the organic C content of wetland soils can be low.

“C is often the limiting factor for denitrification in wetlands, because the organic C content of the wetland soils can be low (Leverenz et al., 2010).”

• cites Leverenz et al., 2010 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Treatment wetlands have been used for treatment of agricultural, residential, and municipal wastewaters due to low cost and simple design.

“For many years, treatment wetlands have been used for the treatment of agricultural, residential, and municipal wastewaters due to the low cost and simple design (Kadlec and Knight, 1996).”

• cites Kadlec and Knight, 1996Not matched

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

May combine two claims.

Since free-draining soils do not hold much water, water-filled pore space is likely lower and therefore not much denitrification is expected.

“Since the soils are free draining and do not hold much water, the water filled pore space (WFPS) is likely to be lower at this site and therefore not much denitrification is expected to occur (Lowrance et al., 1998).”

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

Probably not a substantial claim: may not pass S3 (load-bearing).

Constructed treatment wetlands offer a low-energy alternative to other waste treatment technologies for livestock and other agricultural farms.

“Constructed treatment wetlands offer a low-energy (i.e.lowmaintenance and operation costs) alternative to other waste treatment technologies for livestock and other agricultural farms (Knight et al., 2000).”

• cites Knight et al., 2000 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Upland soils with higher moisture contents do support higher denitrification rates.

“However, upland soils with higher moisture contents do support higher denitrification rates (Lowrance et al., 1998).”

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

May combine two claims.

Drainage water can be controlled so that soils in the outflow ditch stay wetter, which promotes denitrification and reduces NO3- concentrations.

“The drainage water can be controlled so that the soils in the outflow ditch stay wetter, which then promotes denitrification and reduces NO 3 -concentrations (Gilliam and Skaggs, 1986).”

• cites Gilliam and Skaggs, 1986 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

In a swine lagoon wastewater treatment wetland in North Carolina, very high rates of denitrification were measured, particularly in the suspended sludge layer.

“For example, in a swine lagoon wastewater treatment wetland in North Carolina, very high rates of denitrification were measured, particularly in the suspended sludge layer (Hunt et al., 2009).”

• cites Hunt et al., 2009 sourceNot checked — no full text of the source

May combine two claims.

N2 generally comprises a much larger portion of the denitrification end product than N2O under water table management, but this was not the case under free drainage.

“N 2 generally comprises a much larger portion of the denitrification end product than N 2 O under water table management, but this was not the case under free drainage (Elmi et al., 2005).”

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

Probably not a substantial claim: may not pass S3 (load-bearing).

Denitrification accounted for up to 59% of NO3-removal in a riparian wetland receiving NO3-laden groundwater in Kingston, Rhode Island.

“Similarly, denitrification accounted for up to 59% of NO 3 -removal in a riparian wetland receiving NO 3 --laden groundwater in Kingston, Rhode Island (Hanson et al., 1994)”

• cites Hanson et al., 1994 sourceNot checked — no full text of the source

May combine two claims.

In a corn/soybean rotation in Iowa, controlling drainage through water table management decreased N flux by 70% without affecting yield.

“In a study on a corn/soybean rotation in Iowa, controlling drainage through water table management decreased N flux by 70% without affecting yield (Woli et al., 2010).”

• cites Woli et al., 2010 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Denitrification can also be limited due to competition with wetland plants for groundwater NO3-.

“Denitrification can also be limited due to competition with wetland plants for groundwater NO 3 - (Hanson et al., 1994).”

• cites Hanson et al., 1994 sourceNot checked — no full text of the source

May combine two claims.

In a Waikato seepage wetland, gas production accounted for only 6-7% of NO3-removal, so the majority of NO3- was most likely taken up by plants, immobilized by microbes, or removed through DNRA.

“Since gas production only accounted for 6 -7% of removal, the majority of NO 3 -was most likely taken up by plants, immobilized by microbes, or removed through DNRA.”

• cites Zaman et al., 2009Not matched

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

May combine two claims.

Added glucose caused an additional 10% of NO3-removal but also promoted accumulation of NO2-, which is toxic to plants and microorganisms.

“The added glucose caused an additional 10% of NO 3 -removal but also promoted the accumulation of NO 2 -, which is toxic to plants and microorganisms.”

• cites Songliu et al., 2009Not matched

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

May combine two claims.

Water pumped through a heterotrophic denitrification reactor utilizing cotton removed 90% of the NO3- present in the water, although there were high levels of TOC output.

“For example, water pumped through a heterotrophic denitrification reactor utilizing cotton removed 90% of the NO 3 -present in the water, although there were high levels of TOC output (Rocca et al., 2005).”

• cites Rocca et al., 2005Not matched

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

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Methanol addition has been shown to remove 50% of NO3- in aquifers and is the least expensive of all simple C sources, but it is not permitted for use as treatment in potable water supplies in some countries as it can be toxic to humans.

“Addition of methanol has been shown to remove 50% of NO 3 -in aquifers and is the least expensive of all the simple C sources, but it is not permitted for use as treatment in potable water supplies in some countries as it can be toxic to humans (Kruithof et al., 1985;Soares, 2000).”

• cites Kruithof et al., 1985Not matched

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

• cites Soares, 2000 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The removal of N from groundwater can occur through denitrification or discharge of NO3- to surface waters.

“The removal of N from groundwater can occur through denitrification or discharge of NO 3 -to surface waters (Galloway et al., 2003).”

• cites Galloway et al., 2003 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Two-stage channel systems may provide greater stability, increased water flow capacity, increased denitrification, greater nutrient assimilation, and reduced maintenance, but they have not been widely studied.

“While these systems may provide greater stability, increased water flow capacity, increased denitrification, greater nutrient assimilation, and reduced maintenance, two-stage systems have not been widely studied.”

• cites Powell et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

At the septic tank site, the site was N-limited, so the low removal rate accounted for 87-98% of the NO3 entering the system.

“However, the site was N-limited, so this low rate accounted for 87 -98% of the NO 3 entering the system (Robertson et al., 2005).”

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

Probably not a substantial claim: may not pass S3 (load-bearing).

N2O production rates were higher in 12 headwater streams in southwest Michigan receiving agricultural runoff than rates observed for rivers, lakes, and estuaries.

“In one study, N 2 O production rates were shown to be higher in a study of 12 headwater streams in southwest Michigan, USA receiving agricultural runoff, than rates observed for rivers, lakes, and estuaries (Beaulieu et al., 2009).”

• cites Beaulieu et al., 2009 sourceNot checked — no full text of the source

May combine two claims.

After two years, the labile media continued to have higher NO3-removal rates than wood media, but it is unknown how long these rates could be sustained.

“After two years, the labile media continued to have higher NO 3 -removal rates than wood media, but it is unknown how long these rates could be sustained.”

• cites Cameron and Schipper, 2010 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Reactive porous media such as sawdust and woodchips has been used as an organic C source rather than a liquid carbon source in bioreactors.

“Reactive porous media (e.g.sawdust, woodchips) has been used as an organic C source rather than a liquid carbon source in bioreactors (Schipper et al., 2010a).”

• cites Schipper et al., 2010a sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Beds in stream banks had removal rates of 3.2-9.8 g N m-3 d-1, or 20-30% of the NO3- present.

“Beds in stream banks had removal rates of 3.2 -9.8 g N m -3 d -1 , or 20 -30% of the NO 3 -present (van Driel et al., 2006).”

• cites van Driel et al., 2006 sourceNot checked — no full text of the source

May combine two claims.

When sediment is excavated from a ditch, vegetation and microbial communities are also unintentionally removed, disrupting the N cycling process.

“The disadvantage in terms of water quality is that when the sediment is excavated from the ditch, vegetation and microbial communities are also unintentionally removed, disrupting the N cycling process (Strock et al., 2007).”

• cites Strock et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

There have also been issues with biofouling, gas build up, and clogging.

“There have also been issues with biofouling, gas build up, and clogging (Robertson et al., 2007).”

• cites Robertson et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

The advantages of using a reactive porous media barrier are that once installed, the barrier does not require reservoirs or plumbing systems and requires no energy or maintenance for long periods of time.

“The advantages of using a reactive porous media barrier is that once installed, the barrier does not require any reservoirs or plumbing systems and require no energy or maintenance for long periods of time (Hunter, 2001;Robertson and Cherry, 1995).”

• cites Hunter, 2001 sourceNot checked — no full text of the source
• cites Robertson and Cherry, 1995 sourceNot checked — no full text of the source

May combine two claims.

NO3-removal was greatest in experimental barrels with maize cob, and in general the more labile C sources removed greater amounts of NO3- than the wood media.

“NO 3 -removal was greatest in the barrels with maize cob, and in general, the more labile C sources removed greater amounts of NO 3 -than the wood media.”

• cites Cameron and Schipper, 2010 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

In situ experiments with ethanol have been effective in removing up to 50% NO3-.

“In situ experiments with ethanol have also been tested and have been effective in removing up to 50% NO 3 - (Janda et al., 1988).”

• cites Janda et al., 1988 sourceNot checked — no full text of the source

May combine two claims.

Another study in Canada near a septic system showed removal rates of 2.6 g N m-3 d-1 or 80% of the NO3-input.

“while another study in Canada near a septic system showed removal rates of 2.6 g N m -3 d -1 or 80% of the NO 3 -input (Robertson et al., 2000).”

• cites Robertson et al., 2000 sourceNot checked — no full text of the source

May combine two claims.

In the vegetable oil-coated sand study, initially enough NO3- was removed to comply with EPA standards of 10 mg N L-1, but by the end of the 30 week study the majority of the oil was consumed, suggesting oil would have to be injected every 10-20 weeks to remain effective.

“Initially enough NO 3 -was removed to comply with EPA standards of 10 mg N L -1 , but by the end of the 30 week study, the majority of the oil was consumed suggesting that oil would have to be injected every 10 -20 weeks in order to remain effective (Hunter, 2001).”

• cites Hunter, 2001 sourceNot checked — no full text of the source

May combine two claims.

One of the most prevalent problems in using simple C sources is clogging; above ground reactor filters tend to clog if not flushed regularly and in situ systems the aquifer clogs with time.

“One of the most prevalent problems in using simple C sources is clogging; for above ground reactors, the filters tend to clog if they are not flushed regularly and for in situ systems, the aquifer clogs with time (Soares, 2000).”

• cites Soares, 2000 sourceNot checked — no full text of the source

May combine two claims.

In situ use of vegetable oil-coated sand as a C source has been shown to be very effective in NO3-removal, although efficiency declined with time.

“In situ use of vegetable oil-coated sand as a C source has also been shown to be very effective in NO 3 -removal, although efficiency declined with time (Hunter, 2001).”

• cites Hunter, 2001 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Previous studies have attributed clogging of filters to increased microbial biomass or gas buildup.

“Previous studies have attributed clogging of filters to increased microbial biomass (Soares, 2000) or gas buildup (Soares et al., 1991).”

• cites Soares, 2000 sourceNot checked — no full text of the source
• cites Soares et al., 1991Not matched

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

Probably not a substantial claim: may not pass S3 (load-bearing).

Denitrification is highest in the upper 5 cm of benthic sediment and then largely decreases with depth.

“Denitrification is highest in the upper 5 cm of benthic sediment and then largely decreases with depth (Inwood et al., 2007).”

• cites Inwood et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

These three studies suggest that relatively small sawdust additions (5%; 20%) are just as sustainable as 100% woodchip additions, although NO3 input varied between the studies.

“These three studies suggest that relatively small sawdust additions (5%; 20%) are just as sustainable as 100% woodchip additions, although NO 3 -input varied between the studies.”

May combine two claims.

After 14 years, the denitrification wall continued to remove a large proportion of groundwater NO3 entering the wall, likely through denitrification.

“After 14 years, the denitrification wall continued to remove a large proportion of groundwater NO 3 entering the wall, likely through denitrification (Schipper and Vojvodic-Vukovic, 1998).”

• cites Schipper and Vojvodic-Vukovic, 1998 sourceNot checked — no full text of the source

May combine two claims.

Over the course of a year, the first denitrification wall removed between 72% (during peak water usage in September) and 97% of NO3-, corresponding to a removal rate of 3.2-6 g N m-3 d-1.

“Over the course of a year, the wall removed between 72% (during peak water usage in September) to 97% of NO 3 -, corresponding to a removal rate of 3.2 -6 g N m -3 d -1 .”

• cites Robertson and Cherry, 1995 sourceNot checked — no full text of the source

May combine two claims.

Flow rates through denitrification walls are likely to be 0.05-0.5 m day-1 and retention times are likely to be 3-10 days depending on wall width.

“Flow rates are likely to be 0.05 -0.5 m day -1 and retention times are likely to be 3 -10 days depending on wall width (Schipper et al., 2010a).”

• cites Schipper et al., 2010a sourceNot checked — no full text of the source

May combine two claims.

Over a 5 year period, wood chip walls in Iowa reduced NO3- concentrations from 20-25 mg N L-1 by approximately 60% to an average of 8.8 mg N L-1, below the EPA standard of 10 mg N L-1, corresponding to a removal rate of 0.622 g N m-3 d-1.

“Over a 5 year period of study, NO 3 -concentrations were reduced from 20 -25 mg N L -1 by approximately 60% to an average of 8.8 mg N L -1 , which is below the EPA standard of 10 mg N L -1 ; this corresponds to a removal rate of 0.622 g N m -3 d -1 .”

• cites Jaynes et al., 2008 sourceNot checked — no full text of the source

May combine two claims.

The Iowa denitrification wall may be subjected to more frequent aerobic conditions as water table varied and higher temperatures more often than the wall in this study.

“suggesting that the Iowa denitrification wall may be subjected to more frequent aerobic conditions as water table varied and higher temperatures more often than the wall in this study”

May combine two claims.

The long-term study suggested that denitrification walls are cost effective solutions for remediating groundwater NO3 pollution, as they can be effective for a number of years without any maintenance.

“This long-term study suggested that denitrification walls are cost effective solutions for remediating groundwater NO 3 -pollution, as they can be effective for a number of years without any maintenance.”

May combine two claims.

DEA rates measured in year 14 were similar to year 1, indicating that denitrification was still an important mechanism for NO3 removal.

“DEA rates measured in year 14 were similar as measured in year 1 indicating that denitrification was still an important mechanism for NO 3 -removal.”

May combine two claims.

There was still sufficient C available in the denitrification wall for denitrifiers because DEA rates had remained high over 14 years and there was no increase in DEA when C was added.

“It would appear that there was still sufficient C available in the denitrification wall for denitrifiers because DEA rates had remained high over 14 years and there was no increase in DEA when C was added (the wall was not C limited, Table 3-2).”

May combine two claims.

The continued supply of C to denitrifiers and the maintenance of elevated hydraulic conductivity are the two factors that will affect longevity of denitrification walls.

“The continued supply of C to denitrifiers and the maintenance of elevated hydraulic conductivity are the two factors that will affect longevity of denitrification walls (Schipper et al., 2010).”

• Also stated in: § Sustainability of denitrification walls · plain

  “Two factors will affect longevity; the availability of labile C and the maintenance of hydraulic conductivity (Schipper et al., 2010a).”

• cites Schipper et al., 2010 sourceNot checked — no full text of the source

May combine two claims.

In the New Zealand sawdust wall, incoming groundwater contained 5-16 mg N L-1 while concentrations in the wall were <2 mg N L-1, significantly reducing NO3- in the groundwater at a rate of 0.252 g N m-3 d-1.

“Incoming groundwater contained 5 -16 mg N L -1 while concentrations in the wall were < 2 mg N L -1 thereby significantly reducing the amount of NO 3 -in the groundwater, by a rate of 0.252 g N m -3 d -1 .”

• cites Schipper and Vojvodic-Vukovic, 1998 sourceNot checked — no full text of the source

May combine two claims.

The Iowa denitrification wall was not limited by C and was NO3-limited.

“Similar to the New Zealand denitrification wall, the Iowa denitrification wall was not limited by C (i.e.glucose additions did not stimulate denitrification), suggesting that the wall was NO 3 -limited.”

• cites Moorman et al., 2010 sourceNot checked — no full text of the source

May combine two claims.

No denitrification walls have yet failed due to C depletion, because C in denitrification walls appears to decay slowly.

“No denitrification walls have yet failed due to C depletion, because C in denitrification walls appears to decay slowly (Schipper and Vojvodic-Vukovic, 2001;Moorman et al., 2010).”

• cites Schipper and Vojvodic-Vukovic, 2001;Moorman et al., 2010Not matched

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

May combine two claims.

Schipper et al. (2004) constructed a second denitrification wall in Cambridge, New Zealand in 1999, but observed that the majority of groundwater flowed under the wall, decreasing potential NO3-removal.

“Schipper et al. (2004) constructed a second denitrification wall in Cambridge, New Zealand in 1999, but observed that the majority of groundwater flowed under the wall decreasing potential NO 3 -removal.”

• cites Schipper et al., 2004 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The decrease in NO3 input to the wall since construction was attributed to a change in upslope irrigation practices on the farm.

“The NO 3 -input to the wall had decreased since first constructed, which was attributed to a change in upslope irrigation practices on the farm.”

Probably not a substantial claim: may not pass S3 (load-bearing).

There has been some evidence that C in denitrification walls becomes less effective in removing NO3 over time as the C degrades.

“There has been some evidence that the C in denitrification walls becomes less effective in removing NO 3 -over time as the C degrades (Robertson, 2010)”

• cites Robertson, 2010 sourceNot checked — no full text of the source

May combine two claims.

C decayed more slowly at depth in the denitrification wall, most likely due to anaerobic conditions.

“which suggested that C decayed more slowly at depth most likely due to anaerobic conditions”

Probably not a substantial claim: may not pass S3 (load-bearing).

DEA rates may have been so high in year 14 due to the flush of water in June after a long dry period, where the water table was below the wall, so that incomplete aerobic decomposition may have released substantial C available to denitrifiers.

“DEA rates may have been so high in year 14 due to the flush of water in June after a long dry period, where the water table was below the wall, so that incomplete aerobic decomposition may have released substantial C that would be available to denitrifiers”

May combine two claims.

Denitrification in the wall remained NO3 limited, indicating that the wall had not been oversupplied with NO3.

“Further, denitrification in the wall remained NO 3 limited indicating that the wall had not been oversupplied with NO 3 -.”

May combine two claims.

Although removal rates varied across the three wall studies, denitrification walls are typically N limited and so NO3-removal rates are functions of NO3- concentrations.

“Although removal rates varied across these three studies, denitrification walls are typically N limited and so NO 3 -removal rates are functions of NO 3 -concentrations (Schipper and Vojvodic-Vukovic, 1998).”

• cites Schipper and Vojvodic-Vukovic, 1998 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Using a stoichiometric approach, it was estimated that a 20% sawdust denitrification wall near a single-family septic system had enough C available to support 200 years of denitrification, assuming 100% of C would be used by denitrifiers.

“Using a stoichiometric approach, it was estimated that a 20% sawdust denitrification wall near a single-family septic system had enough C available to support 200 years of denitrification, assuming 100% of C would be used by denitrifiers (Robertson and Cherry, 1995).”

• cites Robertson and Cherry, 1995 sourceNot checked — no full text of the source

May combine two claims.

The Iowa denitrification wall constructed from 100% woodchips was still effective after 9 years, achieving around 60% NO3 removal over the first two years and 50% thereafter, with NO3 input averaging 22 mg N L-1.

“A denitrification wall constructed in Iowa, USA from 100% woodchips was found to still be effective after 9 years (Moorman et al., 2010).The Iowa denitrification wall achieved around 60% NO 3 -removal over the first two years and 50% thereafter, where NO 3 -input to the wall averaged 22 mg N L -1 .”

• cites Moorman et al., 2010 sourceNot checked — no full text of the source

May combine two claims.

In Iowa, 75% of C was decomposed at the 90-100 cm depth while only 13% of C was decomposed at the 155-170 cm depth after 9 years.

“in Iowa, 75% of C was decomposed at the 90 -100 cm depth while only 13% of C was decomposed at 155 -170 cm depth after 9 years (Moorman et al., 2010)”

• cites Moorman et al., 2010 sourceNot checked — no full text of the source

Classified as probably not a substantial claim. May combine two claims.

Each of the three denitrification walls was constructed with various C sources: 5% sawdust by weight amended with site soil, 20% sawdust amended with soil, and 100% woodchips.

“Each of the three denitrification walls was constructed with various C sources, 5% sawdust by weight amended with site soil (Schipper and Vojvodic-Vukovic, 1998), 20% sawdust amended with soil (Robertson and Cherry, 1995), and 100% woodchips (Jaynes et al., 2008).”

• cites Schipper and Vojvodic-Vukovic, 1998 sourceNot checked — no full text of the source
• cites Robertson and Cherry, 1995 sourceNot checked — no full text of the source
• cites Jaynes et al., 2008 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S4 (based).

The cost of construction would become prohibitive if the water table is too deep.

“the cost of construction would become prohibitive if the water table is too deep.”

Probably not a substantial claim: may not pass S4 (based).

As long as there is sufficient C and a sufficient microbial population to degrade C to a usable form, NO3-removal will remain high as the denitrification wall ages.

“As long as there is sufficient C and a sufficient microbial population to degrade the C to a usable form, NO 3 -removal will remain high as the denitrification wall ages.”

Classified as probably not a substantial claim.

These studies show the effectiveness of denitrification walls in different climates.

“and so these studies show the effectiveness of denitrification walls in different climates.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The various types and amounts of carbon used in the three long-term denitrification walls may affect their longevity.

“It is also important to note that all three walls were constructed with various types and amounts of C which may affect longevity.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Cameron and Schipper (2010) found that maize cobs had the highest NO3-removal rate after 2 years compared to green waste, wheat straw, and various sizes of Pinus radiata woodchip.

“Using 0.2 m 3 barrels that imitated denitrification beds, Cameron and Schipper (2010) found that maize cobs had the highest NO 3 -removal rate after 2 years compared to green waste, wheat straw, and various sizes of Pinus radiata woodchip”

• cites Cameron and Schipper (2010) sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

In order to compare this study to the 1996 study on the denitrification wall, measurements were made according to Schipper and Vojvodic-Vukovic (1998), including DEA, microbial biomass C, available C, soil water content, total C, and groundwater NO3- concentrations.

“In order to compare this study to the 1996 study on the denitrification wall, measurements were made according to Schipper and Vojvodic-Vukovic (1998), including: DEA; microbial biomass C; available C; soil water content; total C; and groundwater NO 3 -concentrations.”

• cites Schipper and Vojvodic-Vukovic (1998) sourceNot checked — no full text of the source

May combine two claims.

The difference between laboratory and field results is probably due to NO3-loading as NO3 remained limited in the New Zealand denitrification wall.

“The difference is probably due to NO 3 -loading as NO 3 -remained limited in the New Zealand denitrification wall.”

Probably not a substantial claim: may not pass S3 (load-bearing).

NO3-removal decreases by half in denitrification walls after the first year under idealized laboratory conditions.

“This would suggest that NO 3 -removal decreases by half in denitrification walls after the first year under idealized laboratory conditions”

Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

If denitrification walls are used wisely (e.g., in areas of confined shallow aquifers), they are a realistic and affordable technology that could be used in a wide variety of settings.

“If these walls are used wisely (e.g. in areas of confined shallow aquifers), they are a realistic and affordable technology that could be used in a wide variety of settings.”

May combine two claims.

Moorman et al. (2010) found that denitrification walls were still effective after 9 years, and a wall in Iowa, USA was still functioning after 9 years.

“Moorman et al. (2010) and Robertson et al. (2008) which found that denitrification walls were still effective after 9 years and 15 years respectively.”

• Also stated in: § 4.2 Future Research · plain

  “a wall in Iowa, USA was still functioning after 9 years (Moorman et al., 2010)”

• cites Moorman et al. (2010) sourceNot checked — no full text of the source
• cites Moorman et al., 2010 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Using laboratory column tests, 2-year old and 7-year old wood chip material was 50% less effective in removing NO3 than fresh woodchips.

“using laboratory column tests, it was shown that 2-year old and 7-year old wood chip material was 50% less effective in removing NO 3 -than fresh woodchips (Robertson, 2010)”

• cites Robertson, 2010 sourceNot checked — no full text of the source

May combine two claims.

C decay was slower at lower depth, most likely due to anaerobic conditions below the water table.

“indicating that C decay was slower at lower depth, most likely due to anaerobic conditions below the water table”