ISUS/SUNA nitrate measurements in networked ocean observing systems

MacIntyre, G.; Plache, B.; Lewis, Marlon R.; Andrea, J.; Feener, S.; McLean, Scott; Johnson, Kenneth S.; Coletti, Luke J.; Jannasch, Hans W.

doi:10.23919/oceans.2009.5422251

Cited by 12 publications

(13 citation statements)

References 4 publications

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“…Drift was not detected in either SUNA device throughout the 6 month monitoring period (February through July 2015). This corroborates the findings of Opsahl et al () and can likely be explained by the physical nature of groundwater environments, which appear to be resistant to biofouling and its effect on sensor drift that is typical for marine deployments of the SUNA (Macintyre et al ). The lack of observed drift might also be partially caused by the relatively low sampling frequency used in this study (one sample per hour); sampling less frequently reduces the demands on the sensor in terms of spectrometer lamp hours used.…”

Section: Instrumentation and Methodssupporting

confidence: 90%

“…The SUNA uses a UV light source and quartz sampling chamber to measure absorbance. A curve‐fitting algorithm is then used to back‐calculate dissolved nitrate‐N concentrations (Macintyre et al ).…”

Section: Instrumentation and Methodsmentioning

confidence: 99%

“…The SUNA was retrieved from each well approximately every 3 weeks to 1 month to recalibrate the sensor and check for instrument drift. The SUNA was evaluated for two types of instrument drift that can occur in optical sensors: optical drift, which is caused by biofouling, particularly on the sampling window, and spectral drift, which is caused by actual changes in the absorbance spectra of the device relative to the deionized water (DIW) baseline (Macintyre et al ). After retrieval from the borehole, nitrate‐N concentration measurements were taken using a DIW sample and were compared to pre‐deployment readings.…”

Section: Instrumentation and Methodsmentioning

confidence: 99%

“…The Submersible Ultraviolet Nitrate Analyzer (SUNA, Sea‐Bird Scientific, Bellevue, Washington) is an optical sensor that measures nitrate‐N concentrations in‐situ , with no purge sampling required. Field investigations using the SUNA have mostly been limited to marine and estuarine environments (e.g., Johnson and Coletti ; Macintyre et al ; O'Boyle et al ; Poornima et al ) with some applications in surface water (Sackmann ; Wiebe et al ; Duncan et al ; Hartz et al ) and only one published application to date in groundwater wells (Opsahl et al ). The SUNA was used to reveal rapid changes in groundwater nitrate‐N concentrations following recharge events in two karst bedrock wells through long‐term (>1 year) hourly monitoring.…”

Section: Introductionmentioning

confidence: 99%

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On Methods for In‐Well Nitrate Monitoring Using Optical Sensors

Macdonald¹,

Levison²,

Parker³

2017

Groundwater Monitoring Rem

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Optical sensors are promising for collecting high resolution in-well groundwater nitrate monitoring data. Traditional well purging methods are labor intensive, can disturb ambient conditions and yield an unknown blend of groundwater in the samples collected, and obtain samples at a limited temporal resolution (i.e., monthly or seasonally). This study evaluated the Submersible Ultraviolet Nitrate Analyzer (SUNA) for in-well nitrate monitoring through new applications in shallow overburden and fractured bedrock environments. Results indicated that SUNA nitrate-N concentration measurements during flow cell testing were strongly correlated ( R 2 = 0.99) to purged sample concentrations. Vertical profiling of the water column identified distinct zones having different nitrate-N concentrations in conventional long-screened overburden wells and open bedrock boreholes. Real-time remote monitoring revealed dynamic responses in nitrate-N concentrations following recharge events. The monitoring platform significantly reduced labor requirements for the large amount of data produced. Practitioners should consider using optical sensors for real-time monitoring if nitrate concentrations are expected to change rapidly, or if a site's physical constraints make traditional sampling programs challenging. This study demonstrates the feasibility of applying the SUNA in shallow overburden and fractured bedrock environments to obtain reliable data, identifies operational challenges encountered, and discusses the range of insights available to groundwater professionals so they will seek to gather high resolution in-well monitoring data wherever possible.

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Section: Instrumentation and Methodssupporting

confidence: 90%

Section: Instrumentation and Methodsmentioning

confidence: 99%

Section: Instrumentation and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On Methods for In‐Well Nitrate Monitoring Using Optical Sensors

Macdonald¹,

Levison²,

Parker³

2017

Groundwater Monitoring Rem

View full text Add to dashboard Cite

show abstract

“…However, the preparation of stable standard solutions for H 2 S and NO − 3 measurements is difficult as the shelf life of these standards is limited. By contrast, optical UV sensors such as Nitratax (Hach Lange GmbH, Germany), ISUS/SUNA (Johnson and Coletti, 2002;Johnson et al, 2006;MacIntyre et al, 2009) (Satlantic, Canada), or ProPS/OPUS (Zielinski et al, 2007;Prien et al, 2009) (TriOS GmbH, Germany) do not require any chemical reagents but are influenced by optical/ionic interferences including bromide (Br − ), chloride (Cl − ), turbidity and water color. ISEs such as NISE (Hach Lange GmbH, Germany) and EXO (YSI Inc., USA) are not influenced by turbidity and water color, but deteriorate quite rapidly when used under environmental conditions since the sensor molecules in the membrane change or are leached out.…”

Section: Introductionmentioning

confidence: 99%

In situ Determination of Nitrate and Hydrogen Sulfide in the Baltic Sea Using an Ultraviolet Spectrophotometer

et al. 2018

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Evaluating the health status of marine ecosystems becomes ever increasingly important especially against the backdrop of rising pressures from human activities. This is true especially for coastal seas such as the Baltic Sea that is surrounded by highly industrialized countries. Nutrients and pollutants such as nitrate and hydrogen sulfide, which have a major impact on ecosystem functioning, are two of several key environmental indicators for assessing the status of natural waters, and therefore of considerable interest. The frequency and the spatial coverage of the nitrate and hydrogen sulfide measurements are currently limited by the cost of the laboratory analysis and personnel. Optical in situ sensors can help to overcome this challenge by allowing reagentless and fast detection of dissolved chemical species. A chemicalfree optical sensor has been used for direct and simultaneous measurements of both key parameters, and the results were compared with traditional methods. The data were collected during an observational program conducted in the Baltic Sea in February 2018. We used the OPUS UV spectral sensor, which was deployed for the first time in coastal waters, in combination with a deep-sea telemetry system to enable near-real time measurements during CTD profiling. Data processing was carried out using a multiple linear regression procedure. Measurements from both OPUS and on-board analysis were in good agreement. The results showed, that in situ UV-VIS spectrophotometry provides the capability to determine the concentration distributions of nitrate and hydrogen sulfide in the brackish waters of the Baltic Sea.

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Annual nitrate drawdown observed by SOCCOM profiling floats and the relationship to annual net community production

et al. 2017

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Annual nitrate cycles have been measured throughout the pelagic waters of the Southern Ocean, including regions with seasonal ice cover and southern hemisphere subtropical zones. Vertically resolved nitrate measurements were made using in situ ultraviolet spectrophotometer (ISUS) and submersible ultraviolet nitrate analyzer (SUNA) optical nitrate sensors deployed on profiling floats. Thirty‐one floats returned 40 complete annual cycles. The mean nitrate profile from the month with the highest winter nitrate minus the mean profile from the month with the lowest nitrate yields the annual nitrate drawdown. This quantity was integrated to 200 m depth and converted to carbon using the Redfield ratio to estimate annual net community production (ANCP) throughout the Southern Ocean south of 30°S. A well‐defined, zonal mean distribution is found with highest values (3–4 mol C m−2 yr−1) from 40 to 50°S. Lowest values are found in the subtropics and in the seasonal ice zone. The area weighted mean was 2.9 mol C m−2 yr−1 for all regions south of 40°S. Cumulative ANCP south of 50°S is 1.3 Pg C yr−1. This represents about 13% of global ANCP in about 14% of the global ocean area.

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ISUS/SUNA nitrate measurements in networked ocean observing systems

Cited by 12 publications

References 4 publications

On Methods for In‐Well Nitrate Monitoring Using Optical Sensors

On Methods for In‐Well Nitrate Monitoring Using Optical Sensors

In situ Determination of Nitrate and Hydrogen Sulfide in the Baltic Sea Using an Ultraviolet Spectrophotometer

Annual nitrate drawdown observed by SOCCOM profiling floats and the relationship to annual net community production

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