Absorption of sunlight by chromophoric dissolved natural organic matter (CDOM) is environmentally significant because it controls photic zone depth and causes photochemistry that affects elemental cycling and contaminant fate. Both the optics (absorbance and fluorescence) and photochemistry of CDOM display unusual properties that cannot easily be ascribed to a superposition of individual chromophores. These include (i) broad, unstructured absorbance that decreases monotonically well into the visible and near IR, (ii) fluorescence emission spectra that all fall into a single envelope regardless of the excitation wavelength, and (iii) photobleaching and photochemical quantum yields that decrease monotonically with increasing wavelength. In contrast to a simple superposition model, these phenomena and others can be reasonably well explained by a physical model in which charge-transfer interactions between electron donating and accepting chromophores within the CDOM control the optical and photophysical properties. This review summarizes current understanding of the processes underlying CDOM photophysics and photochemistry as well as their physical basis.

The importance of charge-transfer interactions in determining chromophoric dissolved organic matter (CDOM) optical and photochemical properties

Photo-oxidation of dissolved organic carbon (DOC) to inorganic carbon (DIC) in five oligotrophic south Swedish lakes of different humic content (3.9-19 mg DOC liter-r, O-140 mg Pt liter-*, Secchi depth 7.61.5 m) was investigated. Sterile-filtered (0.2 pm) water was incubated in UV-transparent quartz tubes and in tubes covered with aluminum foil. Samples were incubated at different depths (0,0.20,0.65, and 2.00 m) from sunrise to sunset (0400 to 2200 hours) in July. Inorganic C was measured before and after incubation. Total plankton respiration in unfiltered lake-water (production of DIC) was also measured. At the surface, photo-oxidative DIC production was 86410 mg C m-3 d-l, while plankton community respiration was 10 l-274 mg C m-3 d-l. Photo-oxidation integrated over depth was 44-l 7 1 mg C m-2 d-r, while respiration was 201-547 mg C m-2 d-r to a depth of 2 m and 398-860 mg C m-2 d-* over the depth of the epilimnion. Depth-integrated photo-oxidation was independent of water color or DOC concentration in the lakes. Photooxidation was detected deeper than the penetration of UV-B radiation, indicating that longer wavelengths (UV-A and possibly PAR) are also active. DIC production was linearly related to loss of fluorescence (excitation 355 nm, emission 455 nm) in light-incubated samples. Our study shows that photo-oxidation of DOC may be an important process causing the regularly observed supersaturation of DIC in lakes.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1996.41.4.0698

Photo-oxidative production of dissolved inorganic carbon in lakes of different humic content

This chapter reviews and synthesizes the current state of knowledge on sources, transformations, cycling, and fluxes of dissolved organic carbon (DOC) in river-estuarine and coastal ocean systems. Because estuarine waters represent a complex interface between terrestrial, marine, seafloor, and even atmospheric environments, significant consideration is given to the diverse sources of organic matter contributing to estuarine and coastal marine DOC pools. Distributions of bulk DOC, its stable (δ 13 C) and radioactive (Δ 14 C) isotopes, and its biochemical components are reviewed with representative estuaries globally highlighted as examples of the variable types of DOC mixing and processing dynamics in different systems. The significant microbial, photochemical, and physical transformation processes affecting both the amounts and characteristics of DOC during estuarine transport are also evaluated. The chapter concludes by providing some examples of important and compelling recent studies of land–river estuary–coastal ocean DOC fluxes and transfers and their observed long-term changes, both natural and anthropogenically driven.

5.02 – Dissolved Organic Carbon Cycling and Transformation

Quantification of photochemical O 2 uptake provides a measure of total chemical photooxidation of dissolved organic matter (DOM). Here we study this process and present estimates suggesting that photooxidation has the potential to significantly modify marine DOM pools, complementing or exceeding oxidation via coupled chemicalbiological pathways. We measured apparent quantum yields (AQYs) of photobleaching, O2 uptake, and H2O2 production in several coastal marine samples and in dilutions of a tropical estuarine water with oligotrophic seawater. O2-loss AQYs varied little among samples or with dilution but decreased linearly from 1.2 3 10 23 at 300 nm to 0.3 3 10 23 at 400 nm and dropped about threefold to near-constant values with increasing absorbed light dose. H2O2 production, about 45% of O2 uptake, showed similar dependencies, whereas singlet oxygen (O2( 1 Dg)) reactions contributed less than 1% of O2 uptake for typical coastal water. Implications of these findings for photochemical O2 ,H 2O2, and DOM cycling are discussed. Modeling the dose-dependence of O2 loss and photobleaching at 310 nm required three DOM pools. In the simplest case, about 90% is a weakly absorbing, low-AQY pool of DOM admixed with two similar-sized pools of more photochemically reactive DOM. This result suggests that rigorously extrapolating laboratory data to the environment requires detailed mapping of dose-wavelength-photobleaching AQY surfaces. Action spectra and DOM flux estimates for coastal photooxidative chemistry were derived. Site-specific potential rates are comparable to available in situ data. Globally, the DOM photolysis capacity appears to be larger than estimated coastal DOM inputs, especially in tropical and temperate areas, including areas with maximal DOM inputs.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2000.45.2.0267

Photochemical oxygen consumption in marine waters: A major sink for colored dissolved organic matter?

Cycling of nutrient elements in the North Sea

Oxygen consumption from natural waters by photo-oxidizing processes

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.

A. Eversdijk

Author Tools

Chat about Author

Papers

Oxygen consumption from natural waters by photo-oxidizing processes