N itrogen emissions to the atmosphere due to human activity remain elevated in industrialized regions of the world and are accelerating in many developing regions (Galloway 1995). Although the deposition of sulfur has been reduced over much of the United States and Europe by aggressive environmental protection policies, current nitrogen deposition reduction targets in the US are modest. Nitrogen deposition remains relatively constant in the northeastern United States and is increasing in the Southeast and the West (Fenn et al. in press). The US acid deposition effects

/pdf/nitrogen-saturation-in-temperate-forest-ecosystems-29ixssxci4.pdf

Nitrogen Saturation in Temperate Forest Ecosystems

https://digital.csic.es/bitstream/10261/49123/3/Effect_of_fire.pdf

The effect of fire on soil organic matter--a review.

Black carbon (BC), the product of incomplete combustion of fossil fuels and biomass (called elemental carbon (EC) in atmospheric sciences), was quantified in 12 different materials by 17 laboratories from different disciplines, using seven different methods. The materials were divided into three classes: (1) potentially interfering materials, (2) laboratory-produced BC-rich materials, and (3) BC-containing environmental matrices (from soil, water, sediment, and atmosphere). This is the first comprehensive intercomparison of this type (multimethod, multilab, and multisample), focusing mainly on methods used for soil and sediment BC studies. Results for the potentially interfering materials (which by definition contained no fire-derived organic carbon) highlighted situations where individual methods may overestimate BC concentrations. Results for the BC-rich materials (one soot and two chars) showed that some of the methods identified most of the carbon in all three materials as BC, whereas other methods identified only soot carbon as BC. The different methods also gave widely different BC contents for the environmental matrices. However, these variations could be understood in the light of the findings for the other two groups of materials, i.e., that some methods incorrectly identify non-BC carbon as BC, and that the detection efficiency of each technique varies across the BC continuum. We found that atmospheric BC quantification methods are not ideal for soil and sediment studies as in their methodology these incorporate the definition of BC as light-absorbing material irrespective of its origin, leading to biases when applied to terrestrial and sedimentary materials. This study shows that any attempt to merge data generated via different methods must consider the different, operationally defined analytical windows of the BC continuum detected by each technique, as well as the limitations and potential biases of each technique. A major goal of this ring trial was to provide a basis on which to choose between the different BC quantification methods in soil and sediment studies. In this paper we summarize the advantages and disadvantages of each method. In future studies, we strongly recommend the evaluation of all methods analyzing for BC in soils and sediments against the set of BC reference materials analyzed here.

/pdf/comparison-of-quantification-methods-to-measure-fire-derived-10x3leu0m6.pdf

Comparison of quantification methods to measure fire-derived (black/elemental) carbon in soils and sediments using reference materials from soil, water, sediment and the atmosphere

1. From the data presented herein it is possible to deduce the following distribution of total N in humic substances and soils: proteinaceous materials (proteins, peptides, and amino acids) – ca. 40%; amino sugars – 5–6%; heterocyclic N compounds (including purines and pyrimidines) – ca. 35%; NH3–19%; approximately 1/4 of the NH3 is fixed NH4
+. Thus, proteinaceous materials and heterocyclics appear to be major soil N components. 2. Natural 15N abundance levels in soils and humic materials are so low that direct analysis by 15N NMR is very difficult or impossible. To overcome this difficulty, the soil or humic material is incubated with 15N-enriched fertilizer. Even incubation in the laboratory for up to 630 days does not produce the same types of 15N compounds that are formed in soils and humic materials over hundreds or thousands of years. For example, very few 15N-labelled heterocyclics are detected by 15N NMR. Does this mean that heterocyclics are not present? Or are the heterocyclics that are present not labelled under these experimental conditions and therefore not detected by the 15N NMR spectrometer ? Another possibility is that a large number of N heterocyclics occur in soils, but each type occurs in very low concentrations. Until the sensitivity is improved, 15N NMR will not provide results that can be compared with data obtained from the same soil and humic material samples by chemical methods and mass spectroscopy. 3. What is most important with respect to agricultural is that all major N forms in soils are available to organisms and are sources of NH3 or NH4
+ for plant roots and microbes. Naturally, some of the NH3 will enter the N cycle. 4. From chemical and pyrolysis-mass spectrometric analyses it appears that N heterocylics are significant components of the SOM, rather than degradation products of other molecules due to pyrolysis. The arguments in favor of N heterocyclics as genuine SOM components are the following: a) Some N-heterocyclics originate from biological precursors of SOM, such as proteinaceous materials, carbohydrates, chlorophyll, nucleic acids, and alkaloids, which enter the soil system as plant residues or remains of animals. b) In aquatic humic substances and dissolved organic matter (DOM) at considerably lower pyrolysis temperatures (200 to 300°C), free and substituted N-heterocyclics such as pyrroles, pyrrolidines, pyridines, pyranes, and pyrazoles, have been identified by analytical pyrolysis (Schulten et al 1997b). c) Their presence in humic substances and soils was also detected without pyrolysis by gel chromatography – GC/MS after reductive acetylation (Schnitzer and Spiteller 1986), by X-ray photoelectron spectroscopy (Patience et al. 1992), and also by spectroscopic, chromatographic, chemical, and isotopic methods (Ikan et al. 1992). 5. While we can see light at the end of the tunnel as far as soil-N is concerned, further research is needed to identify additional N-containing compounds such as N- heterocyclics, to determine whether these are present in the soil or humic materials in the form in which they were identified or whether they originate from more complex structures. If the latter is correct, then we need to isolate these complex N-molecules and attempt to identify them.

http://www.ci.esapl.pt/mbrito/OM%20a%20review.pdf

The chemistry of soil organic nitrogen : a review

http://directory.umm.ac.id/Data%20Elmu/jurnal/O/Organic%20Geochemistry/Vol31.Issue10.Oct2000/1041.pdf

The molecularly-uncharacterized component of nonliving organic matter in natural environments

Elucidation of the nitrogen forms in melanoidins and humic acid by nitrogen-15 cross polarization-magic angle spinning nuclear magnetic resonance spectroscopy

We made a chemical and NMR study of a set of phenolic polymers of the type long proposed as possible synthetic models for humic acid. Twelve polymers were prepared by air oxidation of p-benzoquinone, and p-benzoquinone plus ammonium chloride, glycine, diglycine, triglycine, alanine, dialanin

A HYDROGEN-1, CARBON-13, AND NITROGEN-15 NUCLEAR MAGNETIC RESONANCE STUDY OF p-BENZOQUINONE POLYMERS INCORPORATING AMINO NITROGEN COMPOUNDS (“SYNTHETIC HUMIC ACIDS”)

Few nmr studies with whole soil have been successfully attempted. Solid-state 13C nmr spectra were obtained for Bainsville clay loam an orthic humic gleysol with 3% carbon, using the CPMAS technique (cross-polarization magic-angle spinning). Results for the whole soil were limited by poor signal/noise and lack of resolution, possibly due to line-broadening by iron. Better results were obtained by employing a < 50 μm fine-size fraction, and difference spectra techniques, allowing observation of added 13C-labelled acetate, and its transformation during incubation. Key words: 13C nmr, CPMAS, labelling, soil

13c-labelling for nmr studies of soils: cpmas nmr observation of 13c-acetate transformation in a mineral soil

Melanoidins and Soil Organic Matter: Evidence of Strong Similarities Revealed by 13C CP-MAS NMR1

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

John A. Ripmeester

Author Tools

Chat about Author

Papers

Elucidation of the nitrogen forms in melanoidins and humic acid by nitrogen-15 cross polarization-magic angle spinning nuclear magnetic resonance spectroscopy

A HYDROGEN-1, CARBON-13, AND NITROGEN-15 NUCLEAR MAGNETIC RESONANCE STUDY OF p-BENZOQUINONE POLYMERS INCORPORATING AMINO NITROGEN COMPOUNDS (“SYNTHETIC HUMIC ACIDS”)

13c-labelling for nmr studies of soils: cpmas nmr observation of 13c-acetate transformation in a mineral soil

Melanoidins and Soil Organic Matter: Evidence of Strong Similarities Revealed by 13C CP-MAS NMR1