Two models for absorption by coloured dissolved organic matter (CDOM)

Jill N. Schwarz, Piotr Kowalczuk, Slawomir Kaczmarek, Glenn F. Cota, B.Greg Mitchell, Mati Kahru, Francisco P. Chavez, Alex Cunningham, David J.C. McKee

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

The standard exponential model for CDOM absorption has been applied to data from diverse waters. Absorption at 440 nm (ag440) ranged between close to zero and 10 m-1, and the slope of the semilogarithmic absorption spectrum over a minimum range of 400 to 440 nm (s440) ranged between < 0.01 and 0.04 nm-1. No relationship was found between ag440 or s440 and salinity. Except in the southern Baltic, s440 was found to have a broad distribution (0.0165 ± 0.0035), suggesting that it should be introduced as an additional variable in bio-optical models when ag440 is large. An alternative model for CDOM absorption was applied to available high quality UV-visible absorption spectra from the Wisla river (Poland). This model assumes that the CDOM absorption spectrum comprises distinct Gaussian absorption bands in the UV, similar to those of benzene. Five bands were fit to the data. The mean central energy of all bands was higher in early summer (E~7.2, 6.6, 6.4, 6.2 and 5.5 eV or 172, 188, 194, 200 and 226 nm) than in winter. The higher energy bands were found to decay in both height and width with increasing salinity, while lower energy bands broadened with increasing salinity. s440 was found to be correlated with shape parameters of the bands centred at 6.4 and 5.5 eV. While the exponential model is convenient for optical modelling and remote sensing applications, these results suggest that the Gaussian model offers a deeper understanding of chemical interactions affecting CDOM molecular structure.
LanguageEnglish
Pages209-241
Number of pages32
JournalOceanologia
Volume44
Issue number2
Publication statusPublished - May 2002

Fingerprint

dissolved organic matter
Biological materials
Absorption spectra
absorption spectrum
salinity
Band structure
energy
chemical interactions
Molecular structure
benzene
Remote sensing
Benzene
chemical structure
remote sensing
Rivers
Poland
deterioration
winter
summer
rivers

Keywords

  • CDOM
  • Gelbstoff
  • ocean colour
  • UV absorption

Cite this

Schwarz, J. N., Kowalczuk, P., Kaczmarek, S., Cota, G. F., Mitchell, B. G., Kahru, M., ... McKee, D. J. C. (2002). Two models for absorption by coloured dissolved organic matter (CDOM). Oceanologia, 44(2), 209-241.
Schwarz, Jill N. ; Kowalczuk, Piotr ; Kaczmarek, Slawomir ; Cota, Glenn F. ; Mitchell, B.Greg ; Kahru, Mati ; Chavez, Francisco P. ; Cunningham, Alex ; McKee, David J.C. / Two models for absorption by coloured dissolved organic matter (CDOM). In: Oceanologia. 2002 ; Vol. 44, No. 2. pp. 209-241.
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Schwarz, JN, Kowalczuk, P, Kaczmarek, S, Cota, GF, Mitchell, BG, Kahru, M, Chavez, FP, Cunningham, A & McKee, DJC 2002, 'Two models for absorption by coloured dissolved organic matter (CDOM)' Oceanologia, vol. 44, no. 2, pp. 209-241.

Two models for absorption by coloured dissolved organic matter (CDOM). / Schwarz, Jill N.; Kowalczuk, Piotr; Kaczmarek, Slawomir; Cota, Glenn F.; Mitchell, B.Greg; Kahru, Mati; Chavez, Francisco P.; Cunningham, Alex; McKee, David J.C.

In: Oceanologia, Vol. 44, No. 2, 05.2002, p. 209-241.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Two models for absorption by coloured dissolved organic matter (CDOM)

AU - Schwarz, Jill N.

AU - Kowalczuk, Piotr

AU - Kaczmarek, Slawomir

AU - Cota, Glenn F.

AU - Mitchell, B.Greg

AU - Kahru, Mati

AU - Chavez, Francisco P.

AU - Cunningham, Alex

AU - McKee, David J.C.

N1 - Strathprints' policy is to record up to 8 authors per publication, plus any additional authors based at the University of Strathclyde. More authors may be listed on the official publication than appear in the Strathprints' record.

PY - 2002/5

Y1 - 2002/5

N2 - The standard exponential model for CDOM absorption has been applied to data from diverse waters. Absorption at 440 nm (ag440) ranged between close to zero and 10 m-1, and the slope of the semilogarithmic absorption spectrum over a minimum range of 400 to 440 nm (s440) ranged between < 0.01 and 0.04 nm-1. No relationship was found between ag440 or s440 and salinity. Except in the southern Baltic, s440 was found to have a broad distribution (0.0165 ± 0.0035), suggesting that it should be introduced as an additional variable in bio-optical models when ag440 is large. An alternative model for CDOM absorption was applied to available high quality UV-visible absorption spectra from the Wisla river (Poland). This model assumes that the CDOM absorption spectrum comprises distinct Gaussian absorption bands in the UV, similar to those of benzene. Five bands were fit to the data. The mean central energy of all bands was higher in early summer (E~7.2, 6.6, 6.4, 6.2 and 5.5 eV or 172, 188, 194, 200 and 226 nm) than in winter. The higher energy bands were found to decay in both height and width with increasing salinity, while lower energy bands broadened with increasing salinity. s440 was found to be correlated with shape parameters of the bands centred at 6.4 and 5.5 eV. While the exponential model is convenient for optical modelling and remote sensing applications, these results suggest that the Gaussian model offers a deeper understanding of chemical interactions affecting CDOM molecular structure.

AB - The standard exponential model for CDOM absorption has been applied to data from diverse waters. Absorption at 440 nm (ag440) ranged between close to zero and 10 m-1, and the slope of the semilogarithmic absorption spectrum over a minimum range of 400 to 440 nm (s440) ranged between < 0.01 and 0.04 nm-1. No relationship was found between ag440 or s440 and salinity. Except in the southern Baltic, s440 was found to have a broad distribution (0.0165 ± 0.0035), suggesting that it should be introduced as an additional variable in bio-optical models when ag440 is large. An alternative model for CDOM absorption was applied to available high quality UV-visible absorption spectra from the Wisla river (Poland). This model assumes that the CDOM absorption spectrum comprises distinct Gaussian absorption bands in the UV, similar to those of benzene. Five bands were fit to the data. The mean central energy of all bands was higher in early summer (E~7.2, 6.6, 6.4, 6.2 and 5.5 eV or 172, 188, 194, 200 and 226 nm) than in winter. The higher energy bands were found to decay in both height and width with increasing salinity, while lower energy bands broadened with increasing salinity. s440 was found to be correlated with shape parameters of the bands centred at 6.4 and 5.5 eV. While the exponential model is convenient for optical modelling and remote sensing applications, these results suggest that the Gaussian model offers a deeper understanding of chemical interactions affecting CDOM molecular structure.

KW - CDOM

KW - Gelbstoff

KW - ocean colour

KW - UV absorption

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M3 - Article

VL - 44

SP - 209

EP - 241

JO - Oceanologia

T2 - Oceanologia

JF - Oceanologia

SN - 0078-3234

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Schwarz JN, Kowalczuk P, Kaczmarek S, Cota GF, Mitchell BG, Kahru M et al. Two models for absorption by coloured dissolved organic matter (CDOM). Oceanologia. 2002 May;44(2):209-241.