Sunlight-Induced Photochemistry of Humic Substances in Natural Waters: Major Reactive Species

Cooper, William J.; Zika, Rod G.; Petasne, Robert G.; Fischer, Anne M.

doi:10.1021/ba-1988-0219.ch022

Cited by 186 publications

(213 citation statements)

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“…Its photochemical products include dissolved inorganic carbon, DIC (CO 2 , HCO 3 À , and CO 3 À2 ); [Chen et al, 1978;Miles and Brezonik, 1981;Allard et al, 1994;Vähätalo et al, 2000;Miller and Zepp, 1995;Granéli et al, 1996;Moore, 1999], CO [Kettle, 1994;Valentine and Zepp, 1993], H 2 O 2 Zika, 1993a, 1993b;Miller and Kester, 1994;Moore et al, 1993], OH . Mopper and Zhou, 1990], oxygen radicals [Cooper et al, 1989;Blough and Zepp, 1995], and many small, biologically labile organic molecules [Bushaw et al, 1996;Moran and Zepp, 1997].…”

Section: Introductionmentioning

confidence: 99%

Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

2003

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[1] The absorption of ultraviolet and visible radiation by colored or chromophoric dissolved organic matter (CDOM) drives much of marine photochemistry. It also affects the penetration of ultraviolet radiation (UV) into the water column and can confound remote estimates of chlorophyll concentration. Measurements of ocean color from satellites can be used to predict UV attenuation and CDOM absorption spectra from relationships between visible reflectance, UV attenuation, and absorption by CDOM. Samples were taken from the Bering Sea and from the Mid-Atlantic Bight, and water types ranged from turbid, inshore waters to the Gulf Stream. We determined the following relationships between in situ visible radiance reflectance, L u /E d (l) (sr À1 ), and diffuse attenuation of UV,. Consistent with published observations, these empirical relationships predict that the spectral slope coefficient of CDOM absorption increases as diffuse attenuation of UV decreases. Excluding samples from turbid bays, the ratio of the CDOM absorption coefficient to K d is 0.90 at 323 nm, 0.86 at 338 nm, and 0.97 at 380 nm. We applied these relationships to SeaWiFS images of normalized water-leaving radiance to calculate the CDOM absorption and UV attenuation in the Mid-Atlantic Bight in May, July, and August 1998. The images showed a decrease in UV attenuation from May to August of approximately 50%. We also produced images of the areal distribution of the spectral slope coefficient of CDOM absorption in the Georgia Bight. The spectral slope coefficient increased offshore and changed with season.

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Section: Introductionmentioning

confidence: 99%

Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

2003

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“…Humic substances are among the most highly UV absorbing compounds in natural waters and act as initiators of photoreactions, some of which involve secondary products (Cooper et al ., 1989) . A potential sequence of reactions leads to formation of hydrogen peroxide (H202) .…”

Section: Resultsmentioning

confidence: 99%

UV-sensitive P compounds: release mechanism, seasonal fluctuation and inhibitory effects on alkaline phosphatase activity in a shallow Chinese freshwater lake (Donghu Lake)

Zhou

1996

Hydrobiologia

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Filtrable phosphorus compounds in a shallow Chinese freshwater lake (Donghu Lake) were fractionated by Sephadex G-25 gel-filtration chromatography . Some portions of those compounds released soluble reactive phosphorus upon irradiation with low dose ultraviolet light . Catalase and a hydroxyl radical scavenger (mannitol) markedly prevented photosensitive phosphorus release . The observed effects may be explained by the action of oxidizing reagents such as hydroxyl radicals, produced in photochemical reactions between UV irradiation and humic substances in the water. There was a strong seasonality in UV sensitive P (UVSP) release . Michaels constants (Km ) of total alkaline phosphatase in the lake water showed a direct positive relation to UVSP . Plot of Km against the UVSP/phosphomonoester ratio reveals a strong relationship between the two variables . These results suggest that in some situations UVSP may be a competitive inhibitor of alkaline phosphatase activity in the lake . The competitive inhibition of fractionated UVSP on alkaline phosphatase reagent (Sigma) apparently supports this hypothesis .

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“…With the important exception of hydrogen peroxide (Cooper et al, 1988;Petasne and Zika, 1987), the transient reactants involved in these photoreactions are usually very short-lived and too dilute to be directly observed on continuous irradiation by commonly used light sources. In some cases, it .is possible to directly observe these transients through laser flash photolysis (Fischer et aL, 1987;Frimmel et al, 1987;Kanner et al, 1989;Power et aL, 1987;Zafiriou and Bonneau, 1987;Zepp et al, 1987a).…”

Section: Experimental Approachesmentioning

confidence: 99%

“…Other studies have shown that sunlight-induced reaction rates of a given organic substance in various natural water samples can vary by orders of magnitude (Skurlatov et aL, 1983;Simmons and Zepp, 1986;Haag and Hoigné, 1986;Larson and Zepp, 1988). This great variability largely can be attributed to changes in the nature and concentration of short~lived transient reactants that are produced photochemically in natural waters (Zafiriou et al, 1984;Hoigné et al, 1988;Cooper et aL., 1988;Zepp, 1988;Haag and Mil, 1989). Transients that have been identified thus far include singlet molecular oxygen, triplet states, hydroxyl radicals, superoxide radicals, organoperoxyl radicals, carbonate radicals, solvated electrons, and hydrogen peroxide.…”

Section: Introductionmentioning

confidence: 99%

Effects of solar ultraviolet radiation on biogeochemical dynamics in aquatic environments : report of a workshop, Marine Biological Laboratory, Woods Hole, Massachusetts, October 23-26, 1989

Blough¹,

Zepp²

1990

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Sunlight-Induced Photochemistry of Humic Substances in Natural Waters: Major Reactive Species

Cited by 186 publications

References 0 publications

Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

UV-sensitive P compounds: release mechanism, seasonal fluctuation and inhibitory effects on alkaline phosphatase activity in a shallow Chinese freshwater lake (Donghu Lake)

Effects of solar ultraviolet radiation on biogeochemical dynamics in aquatic environments : report of a workshop, Marine Biological Laboratory, Woods Hole, Massachusetts, October 23-26, 1989

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