Differential Spectrophotometry on Humic Acids.

Lindqvist, Ingvar; Bergman, B; Nevald, R.; Frank, V.; Brunvoll, J.; Bunnenberg, E.; Djerassi, Carl; Records, Ruth

doi:10.3891/acta.chem.scand.20-0918

Cited by 2 publications

(1 citation statement)

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“…Environmental factors that could cause a change in the absorption characteristics of CDOM without necessarily requiring a change in the quantity of CDOM are pH [Lindqvist and Bergman, 1966;Lindqvist, 1968;Laane, 1982b] and temperature. To test the hypothesis that pH or temperature were driving the in situ changes we observed, their effects on CDOM absorption were determined.…”

Section: Consideration Of Environmental Factorsmentioning

confidence: 99%

Separating in situ and terrigenous sources of absorption by dissolved materials in coastal waters

Twardowski¹,

Donaghay²

2001

J. Geophys. Res.

116

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Abstract. It is presently unclear to what extent coastal and oceanic chromophoric dissolved organic matter (CDOM) is remnant of diluted inputs from the terrestrial biosphere, is the product of in situ biological processes, or is a derivative of both sources. The development of a persistent phytoplankton thin layer (2-4 m thick) in East Sound, Washington, provided an opportunity to study the link between CDOM formation and in situ phytoplankton production. Spectral CDOM absorption a a(h), spectral particulate absorption ap(X), and hydrographic parameters were simultaneously recorded in highresolution vertical profiles. Significant fine-scale variability was observed in a a(412). The majority of this fine structure covaried with salinity, consistent with mixing between an oceanic end member water type (low CDOM, high salinity) and a riverine one (high CDOM, low salinity). During the development of the thin layer, deviations from this a a(412)-salinity relationship were observed. To isolate only the changes in a a(412) resulting from in situ processes, the initial state, represented by the aa(412)-salinity relationship, was subtracted from the measured a a(412). The remaining "in situ change" or residual a a(412) fraction was linearly correlated with oxygen supersaturation and ap(440). Above the phytoplankton layer centered at 3-6 m the a a residual was negative, suggesting removal by photodegradation. A positive a a residual within the thin layer is the first direct evidence for rapid in situ CDOM production associated with phytoplankton primary production. Although the in situ fraction was 10% or less of the total CDOM absorption in East Sound during this period, in the open ocean this fraction may comprise nearly all of the absorption by dissolved materials.

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Section: Consideration Of Environmental Factorsmentioning

confidence: 99%