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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has ...

Toho University

We developed a method for quantifying trace NHOH in brackish- and sea-water samples. Previously reported methods applicable to fresh water cannot be applied to such samples. We determined that interference in seawater owing to the bromide ion can be removed by the addition of phenol. In our procedure, phenol and hypochlorite solutions were added to a sample solution to oxidize NHOH to NO. NO in the sample was then quantified by headspace analysis. The method is not affected by the salt content or ammonia, nitrate, or nitrite at concentrations of 300 μgN L or less. It has a limit of detection of 0.2 μgN L, and can quantify NHOH in natural water samples with a wide range of salinity. It was applied to samples from Lake Nakaumi, a brackish lake located in the eastern part of Shimane Prefecture, Japan.

Sensitive Method for the Oxidation-determination of Trace Hydroxylamine in Environmental Water Using Hypochlorite Followed by Gas Chromatography.

Algae-derived dissolved organic matter (AOM) is an important nutrient source for heterotrophic bacteria, while AOM such as humic substances pose significant challenges during water treatment processing. We hypothesized that the parasitic infection of algae could change the composition and concentration of AOM. This study investigated the quality and quantity of DOM and bacterial abundance in diatom (Synedra) cultures, with and without parasitic fungi (chytrids). The quality of DOM was analyzed using three-dimensional excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) and was compared to changes in algal and bacterial cell numbers. Bacterial abundance was higher and dissolved organic carbon concentrations were lower in the diatom cultures infected with parasitic fungi. Among the DOM compounds, the concentrations of tryptophan-like material derived from algae were significantly lower and the concentrations of humic substance-like material were higher in the infected treatment. The parasitic fungi may have consumed tryptophan-like material and stimulated the release of humic substances. These results provide the first evidence that fungal infection may modulate algal-bacterial interactions, which are associated with changes in the nature of AOM.

Yukiko Senga

Department of Chemistry,
Faculty of Science,
Department of Chemistry, Faculty of Science

Toho University

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on ¹⁴NH₄⁺/¹⁵NH₄⁺ Analyses via Sequential Conversion to N₂O

Yukiko Senga

Department of Chemistry,Faculty of Science,Department of Chemistry, Faculty of Science

Toho University

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

Department of Chemistry,
Faculty of Science,
Department of Chemistry, Faculty of Science

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on ¹⁴NH₄⁺/¹⁵NH₄⁺ Analyses via Sequential Conversion to N₂O