Selective adsorption of dissolved organic matter to mineral soils

Kothawala, Dolly N.; Roehm, C. L.; Blodau, Christian; Moore, Tim R.

doi:10.1016/j.geoderma.2012.07.001

Cited by 86 publications

(71 citation statements)

References 37 publications

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“…Markedly higher SUVA and aromaticity of pore water DOC in the VS probably reflect a mix of DOC molecules containing more aromatic compounds than the DOC in the UVS (Chin et al 1994;Weishaar et al 2003;Kothawala et al 2012). Given the difference in spectrophotometric properties between DOC in the VS and UVS, the reactivity and bioavailability of the DOC could have differed between the two sediment types.…”

Section: Discussionmentioning

confidence: 99%

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Influence of emergent vegetation on nitrate cycling in sediments of a groundwater-fed river

et al. 2013

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Emergent vegetation in river beds can play a significant role in nutrient cycling in riverine sediments. We analysed and compared pore water NO 3 -concentration gradients in the sediments of the River Leith, Cumbria, UK, in the presence and absence of emergent vegetation (dominated by Sparganium spp.). High resolution (1 cm interval), in situ, vertical profiles of NO 3 -to 30 cm depth were measured using deployment of diffusive equilibrium in thin films probes on four occasions from July to September 2010. We found significantly (p \ 0.05) lower NO 3 -concentration under vegetated sediments (VS) compared to those under adjacent un-vegetated sediments (UVS). Concentrations of dissolved oxygen, measured in pore water collected from multi-level piezometers at 10, 20, 25, 30 and 35 cm depths at the VS and UVS sties, were generally lower under VS (median concentration = 28 lM) than under UVS (median = 132 lM) and correlated significantly with NO 3 -concentration (Spearman's r = 0.74, p \ 0.05). Similarly, pore water dissolved organic carbon (DOC) concentration was 2.8 times higher under VS compared to UVS, and correlated negatively with NO 3 -concentration (Spearman's r = -0.39, p \ 0.05). Specific ultra-violet absorption at 254 nm (SUVA) and per cent aromaticity values of DOC were significantly higher under VS (p \ 0.05), suggesting that the DOC contained more complex (aromatic) compounds than DOC recorded under UVS. We suggest that, the higher quantity of DOC and its distinct SUVA and percentage aromaticity under VS may have supported faster dissolved oxygen consumption, with the creation of anoxic zones conducive for NO 3 -reduction mainly through denitrification. Metabolic uptake and immobilization of NO 3-by plants and microbes may have further contributed to lower NO 3 -concentrations under VS. As Sparganium spp. is a common plant growing in river beds in the UK, its role in NO 3 -cycling should be considered in attempts to accurately budget N cycling in river beds.

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Section: Discussionmentioning

confidence: 99%

“…The absorbance at 250 and 280 nm was recorded for the determination of SUVA @254nm (specific UV absorption (L mg -1 C m -1 ) = (A 254nm 9 100)/DOC) and percent aromaticity (% aromaticity = [0.05 (A 280nm 9 1,000) ? 6.74)] (Chin et al 1994;Roehm et al 2009;Kothawala et al 2012).…”

Section: Laboratory Processing Of Detmentioning

confidence: 99%

Influence of emergent vegetation on nitrate cycling in sediments of a groundwater-fed river

et al. 2013

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“…Interestingly, the mineral content of RICEC was also high, ∼5 times greater than the mineral content of the wood chars (Table 3). Aromatic compounds, including BC, have been shown to preferentially interact with and sorb to mineral surfaces in soils (Brodowski et al, 2005;Kothawala et al, 2012) which suggests that mineral content may be an important control in the mobilization of DBC. However, no significant correlation was observed between mineral content of source soils and chars and net amount of DBC leached (R 2 = 0.03; p = 0.66; n = 24).…”

Section: Comparing the Quantity And Quality Of Dissolved Black Carbonmentioning

confidence: 99%

A New Perspective on the Apparent Solubility of Dissolved Black Carbon

2017

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Black carbon (BC), pyrogenic organic matter generated from the incomplete combustion of biomass, is ubiquitous in the environment. The molecular structures which comprise the BC pool of compounds are defined by their condensed aromatic core structures polysubstituted with O-containing functionalities (e.g., carboxyl groups). Despite the apparent hydrophobicity of BC molecules, a considerable portion of BC is translocated from terrestrial to aquatic systems in the form of dissolved BC (DBC). However, the specific biogeochemical mechanisms which control the transfer of BC from the land to the water remain elusive. In the current study, the apparent solubility of DBC was inferred from octanol-water partition coefficients (K ow ) modeled for proposed DBC structures with varying degrees of polycondensation and polar functionality. Modeled K ow values indicated that DBC molecules with small aromatic ring systems and high degrees of hydrophilic functionality may be truly solubilized in the aqueous phase. However, large and highly condensed DBC structures yielded high K ow values, which suggested that a considerable portion of the DBC pool which has been quantified in aquatic environments is not truly dissolved. We hypothesized that other DOM components may act as mediators in the solubilization of condensed aromatic molecules and serve to increase the solubility of DBC via hydrophobic, intermolecular associations. This hypothesis was tested through controlled leaching experiments to determine whether the mobilization of DBC from particulate soils and chars became enhanced in the presence of DOM. However, we observed that characteristics inherent to each sample type had a greater influence than added DOM on the apparent solubility of DBC. In addition, the direct comparison of molecular marker (benzenepolycarboxylic acids) and ultrahigh resolution mass spectral data (FT-ICR/MS) on leachates obtained from the same set of soils and char did not show a clear overlap in DBC quantification or characterization between the two analytical methods. Correlations between FT-ICR/MS results and BPCA were not significant possibly due to differences in the methodological windows and/or small sample size. Our results were unable to provide evidence in support of proposed hydrophobic interactions between DOM and DBC, suggesting that other physical/chemical mechanisms play important roles in the dissolution of BC.

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“…DOM, the most viable electron shuttle in natural systems, mediates the reduction of iron from Fe(III) to Fe(II) Weber, 2009, 2012). The distribution of Fe(II) at solid-water interfaces is influenced by DOM in natural environments (Strathmann and Stone, 2002;Colón et al, 2008;Ding et al, 2011;Kothawala et al, 2012). Furthermore, DOM undergoes ligand exchange with hydroxyl groups at mineral surfaces to form stable mineral-DOM bonds, decreasing the availability of hydroxyl groups for interaction with Fe(II) (Rose and Waite, 2003;Colón et al, 2008;Li et al, 2009;Aeschbacher et al, 2012).…”

Section: Introductionmentioning

confidence: 99%