Iron as a source of color in river waters

Xiao, Yihua; Räike, Antti; Hartikainen, Helka Helinä; Vähätalo, Anssi V.

doi:10.1016/j.scitotenv.2015.06.092

Cited by 33 publications

(21 citation statements)

References 43 publications

(78 reference statements)

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“…Our median 330 values for riverine tDOC is 234 μmol C mol photons −1 and about half of the 479 μmol C mol photons −1 used to estimate the amount of DIC photoproduction in inland waters (Koehler et al, 2014). High 330 values correlate positively with CDOM, the specific UV absorption coefficient, and the aromaticity of tDOC , which are typically highest for tDOC imported freshly from land to inland waters without earlier exposure to solar radiation (Salonen & Vähätalo, 1994;Xiao et al, 2013Xiao et al, , 2015. Additionally, ferric iron associated to tDOC and acidity increase 330 values in freshwaters (Gu et al, 2017).…”

Section: 1002/2017gb005698mentioning

confidence: 93%

“…High φ 330 s correlate positively with CDOM, the specific UV absorption coefficient and the aromaticity of tDOC , which are typically highest for tDOC imported freshly from land to inland waters without earlier exposure to solar radiation [Salonen and Vähätalo, 1994;Xiao et al, 2013Xiao et al, , 2015.…”

Section: The Annual Areal Rates Of Dic Photoproduction From Tdoc In Rmentioning

confidence: 99%

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Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

Aarnos

Gélinas

Kasurinen

et al. 2018

Global Biogeochemical Cycles

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When terrigenous dissolved organic carbon (tDOC) rich in chromophoric dissolved organic matter (tCDOM) enters the ocean, solar radiation mineralizes it partially into dissolved inorganic carbon (DIC). This study addresses the amount and the rates of DIC photoproduction from tDOC and the area of ocean required to photomineralize tDOC. We collected water samples from 10 major rivers, mixed them with artificial seawater, and irradiated them with simulated solar radiation to measure DIC photoproduction and the photobleaching of tCDOM. The linear relationship between DIC photoproduction and tCDOM photobleaching was used to estimate the amount of photoproduced DIC from the tCDOM fluxes of the study rivers. Solar radiation was estimated to mineralize 12.5 ± 3.7 Tg C yr−1 (10 rivers)−1 or 18 ± 8% of tDOC flux. The irradiation experiments also approximated typical apparent spectral quantum yields for DIC photoproduction (ϕλ) over the entire lifetime of the tCDOM. Based on ϕλs and the local solar irradiances in river plumes, the annual areal DIC photoproduction rates from tDOC were calculated to range from 52 ± 4 (Lena River) to 157 ± 2 mmol C m−2 yr−1 (Mississippi River). When the amount of photoproduced DIC was divided by the areal rate, 9.6 ± 2.5 × 106 km2 of ocean was required for the photomineralization of tDOC from the study rivers. Extrapolation to the global tDOC flux yields 45 (31–58) Tg of photoproduced DIC per year in the river plumes that cover 34 (25–43) × 106 km2 of the ocean.

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Section: 1002/2017gb005698mentioning

confidence: 93%

Section: The Annual Areal Rates Of Dic Photoproduction From Tdoc In Rmentioning

confidence: 99%

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

Aarnos

Gélinas

Kasurinen

et al. 2018

Global Biogeochemical Cycles

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“…An acidic (pH 1) stock solution (0.5 mmol L −1 Fe 2 (SO 4 ) 3 · nH 2 O in 0.1 mol L −1 HCl) (Titrisol®, Merck) was used as a source of Fe(III) in all experiments with introduced Fe(III). The stock solution of ALW was prepared according to Kester et al [] and was added to form the final inorganic ion concentrations presented in Table and an ionic strength of 0.87 (calculated as mmol L −1 ), which is close to the average ionic strength of Finnish river waters (0.8) [ Xiao et al , ]. The nutrients N and P were introduced as separate solutions of NH 4 Cl and GlyP, respectively (Table ).…”

Section: Methodsmentioning

confidence: 99%

The effect of iron on the biodegradation of natural dissolved organic matter

Xiao

Hoikkala²,

Kasurinen

et al. 2016

JGR Biogeosciences

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Iron (Fe) may alter the biodegradation of dissolved organic matter (DOM), by interacting with DOM, phosphorus (P), and microbes. We isolated DOM and a bacterial community from boreal lake water and examined bacterial growth on DOM in laboratory experiments. Fe was introduced either together with DOM (DOM‐Fe) or into bacterial suspension, which led to the formation of insoluble Fe precipitates on bacterial surfaces (Fe coating). In the latter case, the density of planktonic bacteria was an order of magnitude lower than that in the corresponding treatment without introduced Fe. The association of Fe with DOM decreased bacterial growth, respiration, and growth efficiency compared with DOM alone at the ambient concentration of dissolved P (0.16 µmol L−1), indicating that DOM‐associated Fe limited the bioavailability of P. Under a high concentration (21 µmol L−1) of P, bacterial biomass and respiration were similar or several times higher in the treatment where DOM was associated with Fe than in a corresponding treatment without Fe. Based on the next generation sequencing of 16S rRNA genes, Caulobacter dominated bacterial communities grown on DOM‐Fe. This study demonstrated that association of Fe with a bacterial surface or P reduces bacterial growth and the consumption of DOM. In contrast, DOM‐Fe is bioavailable and bound Fe can even stimulate bacterial growth on DOM when P is not limiting.

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“…The color of water is a defining feature of freshwater ecosystems primarily caused by inputs of brown-pigmented dissolved organic carbon (DOC) from terrestrial runoff (Xiao et al, 2015). Recent concerns have been raised regarding widespread increases in color and DOC concentrations in the Northern Hemisphere caused by a combination of factors involving a warmer climate (Lepistö et al, 2014;Pagano et al, 2014), an intensified hydrological cycle (Weyhenmeyer et al, 2012;Fasching et al, 2016), and the release of DOC previously immobilized in soils due to acidification (Monteith et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes

et al. 2018

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Abstract. Dissolved organic carbon (DOC) may be removed, transformed, or added during water transit through lakes, resulting in changes in DOC composition and pigmentation (color). However, the process-based understanding of these changes is incomplete, especially for headwater lakes. We hypothesized that because heterotrophic bacteria preferentially consume noncolored DOC, while photochemical processing removes colored fractions, the overall changes in DOC color upon water passage through a lake depend on the relative importance of these two processes, accordingly. To test this hypothesis we combined laboratory experiments with field studies in nine boreal lakes, assessing both the relative importance of different DOC decay processes (biological or photochemical) and the loss of color during water transit time (WTT) through the lakes. We found that influence from photo-decay dominated changes in DOC quality in the epilimnia of relatively clear headwater lakes, resulting in systematic and selective net losses of colored DOC. However, in highly pigmented brown-water lakes (absorbance at 420 nm > 7 m −1 ) biological processes dominated, and there was no systematic relationship between color loss and WTT. Moreover, in situ data and dark experiments supported our hypothesis on the selective microbial removal of nonpigmented DOC, mainly of low molecular weight, leading to persistent water color in these highly colored lakes. Our study shows that brown headwater lakes may not conform to the commonly reported pattern of the selective removal of colored constituents in freshwaters, as DOC can show a sustained degree of pigmentation upon transit through these lakes.

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Iron as a source of color in river waters

Cited by 33 publications

References 43 publications

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

The effect of iron on the biodegradation of natural dissolved organic matter

Quality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processes

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