Apparent quantum yield of photochemical dissolvedorganic carbon mineralization in lakes

• Up to one tenth of the carbon dioxide (CO2) emissions from inland waters worldwide are directly inducedby the photochemical mineralization of dissolved organic matter (DOM). The photochemical production ofdissolved inorganic carbon (DIC) per photon absorbed by chromophoric DOM (CDOM) decreases exponentiallywith increasing irradiance wavelength, and is commonly described by an “apparent quantum yield”(AQY) spectrum. Although an essential model parameter to simulate photochemical mineralization the AQYremains poorly constrained. Here, the AQY of photochemical DIC production for 25 lakes located in boreal,polar, temperate, and tropical areas, including four saline lagoons, was measured. The wavelength-integratedAQY (300–500 nm; mol DIC mol CDOM-absorbed photons21) ranged from 0.05 in an Antarctic lake to 0.61in a humic boreal lake, averaging 0.2460.03 SE. AQY was positively linearly correlated with the absorptioncoefficient at 420 nm (a420) as a proxy for CDOM content (R2 of 0.64 at 300 nm and 0.26 at 400 nm), withspecific UV absorption coefficients as a proxy for DOM aromaticity (R2 of 0.56 at 300 nm and 0.38 at400 nm), and with the humification index (R2 of 0.41 at 300 nm and 0.42 at 400 nm). Hence, a considerablefraction of the AQY variability was explained by water optical properties in inland waters. The correlation ofAQY with a420 opens up the possibility to improve large-scale model estimates of sunlight-induced CO2 emissionsfrom inland waters based on water color information derived by satellite remote sensing.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Oceanografi, hydrologi och vattenresurser (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Oceanography, Hydrology and Water Resources (hsv//eng)

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Miljövetenskap

Environmental Science

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