Nitrogen Determination in Seawater

D’Elia, Christopher F.

doi:10.1016/b978-0-12-160280-2.50028-6

Cited by 8 publications

(3 citation statements)

References 92 publications

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“…!3a shows that only UV+OR irradiation set up yielded lower oxidation efficiency for both TDN and TDP, than the standard oxidation procedure (UV+OR+Bath): 77.8% and 91.3% on average, respectively, indicating that the "batheffect" was more pronounced in the oxidation of organic N than P compounds. This result is in good agreement with previous experiments that showed that some of nitrogenous organic compounds, particularly with N-N bonds, were refractory to UV-oxidation only (Henricksen 1970;D'Elia 1983;Walsh 1989). In the CFA III manifold, while some decomposition of persulfate began in the UV-digestor, thus increasing the oxidation efficiency of some organic P compounds, more complete oxidation of organic N compounds occurred in the heated bath as the result of the further decomposition of potassium persulfate.…”

Section: Cfa Iii: Uv+or Versus Uv+or+ Heated Bath Oxidationssupporting

confidence: 92%

A modified segmented continuous flow analysis method for simultaneous determination of total dissolved nitrogen and phosphorus in marine environments

Dafner

Szmant

2014

Limnology & Ocean Methods

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We present a modified segmented flow analysis method for the simultaneous determination of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) in marine environments based on a combination of photooxidation and alkaline persulfate digestion. The modified Bran+Luebbe ® Continuous Flow Autoanalyzer III (CFA III) manifold consists of a high-energy UV lamp (1.1 W at 185 nm) and a heated bath (90°C). The analytical precision of the method is within 2.1% for TDN and 1.6% for TDP analyses, and within 4.5% for dissolved organic N and P (DON and DOP); the average standard deviation is ± 0.37 μM for DON and ± 0.02 μM for DOP. The detection limit is 1.23 μM for DON and 0.05 μM for DOP analyses. The linear analytical range of the method is up to 200 μM for TDN and up to 6 μM for TDP. The CFA III method was compared with the autoclave alkaline persulfate oxidation (PO) and the high temperature combustion (HTC-TDN) techniques. All methods, when applied to open ocean and coastal samples, produced similar DON concentrations (PO:CFA III = 102% and HTC:CFA III = 100%, on average), but the CFA III method yielded significantly higher oxidation efficiencies for DOP analyses than the PO technique (PO:CFA III = 71%, on average). For CFA III-TDN/TDP analyses samples with different salinities should be analyzed relative to standard solutions prepared with similar matrix. A throughput of 20 samples per hour is easily achieved. This method is simple, fast, reproducible, economical, and is highly suitable for simultaneous TDN and TDP routine analyses.

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Section: Cfa Iii: Uv+or Versus Uv+or+ Heated Bath Oxidationssupporting

confidence: 92%

A modified segmented continuous flow analysis method for simultaneous determination of total dissolved nitrogen and phosphorus in marine environments

Dafner

Szmant

2014

Limnology & Ocean Methods

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“…Precision of the nutrient analyses, as determined from errors between duplicates, was high: f 0.06 PM nitrate, + 0.02 pM nitrite and + 0.06 PM ammonium ( f 2 standard errors; Youden 1959, D'Elia 1983. No change in concentration of ambient seawater controls could be detected over the 1 h incubation period (paired samples t-test on initial and final concentration; nitrate p > 0.5, nitrite p > 0.2, ammonium p > 0.5, n = 96, 82 and 96 respectively).…”

Section: Resultsmentioning

confidence: 99%

Nutrient uptake in the reef-building coral Acropora palmata at natural environmental concentrations

Bythell¹

1990

Mar. Ecol. Prog. Ser.

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Experiments were carried out over 15 mo to assess the net exchange of dissolved inorganic nitrogen (DIN) by the symbiotic coral Acropora palmata (Lamarck) under near-natural environmental conditions. Specimens were enclosed in situ in transparent acrylic chambers and changes in the ambient seawater concentrations of nitrate, nitrite and ammonium determined over 1 h closed incubat i o n~. There was a consistent depletion of nitrate and a more variable but significant mean depletion of ammonium within the experimental chambers, indicating simultaneous net uptake of both ions by the coral. No exchange of nitrite could be detected. No significant changes in concentration of any form of DIN occurred in ambient seawater control chambers. Contrary to previous predictions from studies of uptake kinetics in isolated zooxanthellae and other coral species, mean net rates of nitrate uptake exceeded that of ammonium uptake by a factor of 2. Nitrate uptake was dependent on substrate concentration, with a linear response over the range of ambient seawater concentrations encountered in the study. Rate of ammonium uptake was apparently independent of substrate concentration and the rate of uptake of each ion was independent of the concentration of the others. A diurnal rhythm was noted in nitrate uptake rates, after changes in concentration had been taken into account, which suggests that although uptake continued over the complete 24 h period, maximal rates of uptake were not maintained throughout the night. These results support previous studies which have demonstrated the capability for dual uptake of both nitrate and ammonium by zooxanthellae, but suggest that under natural conditions nitrate rather than ammonium provides the primary external source of dissolved inorganic nitrogen in this species.

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“…It has been supported by approximately 10 000 individual data sets and covers pure materials (100%) to trace levels (ng kg −1 ). For nitrate and ammonium determinations, RSD are variable ranging from 2 to 15% [ D'Elia , 1983, and references therein]. For nitrogen in particulate materials, Nieuwenhuize et al [1994] reported RSD values close to 3.7%.…”

Section: Methodsmentioning

confidence: 99%

Reliability of N flux rates estimated from ¹⁵N enrichment and dilution experiments in aquatic systems

Elskens

Baeyens

Brion

et al. 2005

Global Biogeochemical Cycles

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[1] This paper investigates the estimation behavior of six increasingly complex 15 N models, for estimating flux rates between phytoplankton and dissolved N pools in aquatic ecosystems. The development of these models over the last 40 years reflects increasing realism in the pools and fluxes that constitute the N cycle. The purpose of this paper is to assess how the model results are influenced by the underlying assumptions. For example, with respect to uptake of 15 N by phytoplankton, is anything gained by assuming that regenerated N become isotopically enriched after the introduction of the 15 N label, or is it just as accurate to assume that no source other than the initial 15 N label contributes to the enrichment signal in phytoplankton? To conduct an objective assessment of the models, we compared them to (1) a set of reference values generated numerically by a process oriented model, and (2) real experimental data. The results show that for a number of 15 N models, properties such as accuracy and precision cannot both be optimized under the same conditions, and a compromise must be struck. Oversimplified models risk bias when their underlying assumptions are violated, but overly complex models can misinterpret part of the random noise as relevant processes. Therefore none of the 15 N model solutions can a priori be rejected, but each should carefully be assessed with hypothesis testing. A backward regression strategy based on a statistical interpretation of the cost function (sum of the weighted least squares residuals) was used to select optimal solution subsets corresponding to a given data set.

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Nitrogen Determination in Seawater

Cited by 8 publications

References 92 publications

A modified segmented continuous flow analysis method for simultaneous determination of total dissolved nitrogen and phosphorus in marine environments

A modified segmented continuous flow analysis method for simultaneous determination of total dissolved nitrogen and phosphorus in marine environments

Nutrient uptake in the reef-building coral Acropora palmata at natural environmental concentrations

Reliability of N flux rates estimated from ¹⁵N enrichment and dilution experiments in aquatic systems

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Nitrogen Determination in Seawater

Cited by 8 publications

References 92 publications

A modified segmented continuous flow analysis method for simultaneous determination of total dissolved nitrogen and phosphorus in marine environments

A modified segmented continuous flow analysis method for simultaneous determination of total dissolved nitrogen and phosphorus in marine environments

Nutrient uptake in the reef-building coral Acropora palmata at natural environmental concentrations

Reliability of N flux rates estimated from 15N enrichment and dilution experiments in aquatic systems

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Reliability of N flux rates estimated from ¹⁵N enrichment and dilution experiments in aquatic systems