The Effect of Storage on the Radiocarbon, Stable Carbon and Nitrogen Isotopic Signatures and Concentrations of Riverine DOM

Gulliver, Pauline; Waldron, Susan; Scott, E.M.; Bryant, Charlotte

doi:10.1017/s0033822200046191

Cited by 18 publications

(16 citation statements)

References 22 publications

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“…DOC samples were filtered through pre‐furnaced (8 h at 450°C) 0.7 µm glass fiber filter paper on the day of sampling and stored refrigerated. Samples treated this way show little change in composition over 3 months [ Gulliver et al ., ]. Prior to the measurement of [DOC] by combustion (Thermalox TOC 2020, Analytical Sciences) the samples were acidified to pH 3.9 and degassed to remove any DIC.…”

Section: Methodsmentioning

confidence: 99%

Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

et al. 2016

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We constructed a whole carbon budget for a catchment in the Western Amazon Basin, combining drainage water analyses with eddy covariance (EC) measured terrestrial CO2 fluxes. As fluvial C export can represent permanent C export it must be included in assessments of whole site C balance, but it is rarely done. The footprint area of the flux tower is drained by two small streams (~5–7 km2) from which we measured the dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) export, and CO2 efflux. The EC measurements showed the site C balance to be +0.7 ± 9.7 Mg C ha−1 yr−1 (a source to the atmosphere) and fluvial export was 0.3 ± 0.04 Mg C ha−1 yr−1. Of the total fluvial loss 34% was DIC, 37% DOC, and 29% POC. The wet season was most important for fluvial C export. There was a large uncertainty associated with the EC results and with previous biomass plot studies (−0.5 ± 4.1 Mg C ha−1 yr−1); hence, it cannot be concluded with certainty whether the site is C sink or source. The fluvial export corresponds to only 3–7% of the uncertainty related to the site C balance; thus, other factors need to be considered to reduce the uncertainty and refine the estimated C balance. However, stream C export is significant, especially for almost neutral sites where fluvial loss may determine the direction of the site C balance. The fate of C downstream then dictates the overall climate impact of fluvial export.

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Section: Methodsmentioning

confidence: 99%

Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

et al. 2016

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“…The water samples were stored at 4 • C for approximately 1 year prior to analysis. Cold storage has been shown to be a viable method for the long-term preservation of carbon isotopic signatures (Gulliver et al, 2010). Samples were analysed by accelerator mass spectrometry (AMS) at the Nat-…”

Section: Radiocarbon Dating (Do 14 C)mentioning

confidence: 99%

Fluvial organic carbon fluxes from oil palm plantations on tropical peatland

et al. 2018

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Intact tropical peatlands are dense long-term stores of carbon. However, the future security of these ecosystems is at risk from land conversion and extensive peatland drainage. This can enhance peat oxidation and convert long-term carbon sinks into significant carbon sources. In Southeast Asia, the largest land use on peatland is for oil palm plantation agriculture. Here, we present the first annual estimate of exported fluvial organic carbon in the drainage waters of four peatland oil palm plantation areas in Sarawak, Malaysia. Total organic carbon (TOC) fluxes from the plantation second-and third-order drains were dominated (91 %) by dissolved organic carbon (DOC) and ranged from 34.4 ± 9.7 C m −2 yr −1 to 57.7 %, 16.3 g C m −2 yr −1 (± 95 % confidence interval). These fluxes represent a single-year survey which was strongly influenced by an El Ninõ event and therefore lower discharge than usual was observed. The magnitude of the flux was found to be influenced by water table depth, with higher TOC fluxes observed from more deeply drained sites. Radiocarbon dating on the DOC component indicated the presence of old (pre-1950s) carbon in all samples collected, with DOC at the most deeply drained site having a mean age of 735 years. Overall, our estimates suggest fluvial TOC contributes ∼ 5 % of total carbon losses from oil palm plantations on peat. Maintenance of high and stable water tables in oil palm plantations appears to be key to minimising TOC losses. This reinforces the importance of considering all carbon loss pathways, rather than just CO 2 emissions from the peat surface, in studies of tropical peatland land conversion.

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“…This timeline was acceptable as we tested the impact of storage length on DOC UV absorbance and found < 0.01cm -1 difference (n = 7, SD = 0.008 cm -1 ) was observed among filtered samples before and after being stored for a month. No difference in [DOC] was observed in samples stored for up to 30 days if the samples had been filtered (Gulliver et al, 2010).…”

Section: Samplingmentioning

confidence: 99%

Fluvial dissolved organic carbon composition varies spatially and seasonally in a small catchment draining a wind farm and felled forestry

Zheng

Waldron

Flowers

2018

Science of The Total Environment

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Assessing whether land use, from activities such as wind farm construction and tree-felling, impacts on terrestrial C delivery to rivers has focused on quantifying the loss of dissolved organic carbon (DOC), and not the composition changes. Here we explore how land use influences DOC composition by considering fluvial DOC concentration, [DOC], and spectrophotometric composition of a river draining a peat-rich catchment. We find that in this 5.7km catchment differences occur in both the concentration and composition of the DOC in its sub-catchments. This is attributed to differences in how land was used: one tributary (D-WF) drains an area with wind farm construction and forestry in the headwaters, and one tributary (D-FF) drains an area with felled plantation trees. Generally, [DOC] in both streams showed similar seasonal variation, and autumn maxima. However, the felled catchment had greater mean [DOC] than the wind farm catchment. The SUVA and E/E indicated DOC in both streams had similar aromaticity and fulvic:humic acid for most of the time, but SUVA and E/E indicated less DOC humification in the felled catchment. This may be due to young DOC from the breakdown of residual branches and roots, or more humification in soils in the wind farm area. During the dry months, DOC composition showed more spatial variation: the D-WF DOC had smaller SUVA (less total aromatic material) and SUVA (fewer humic substances). The decreased E/E in both streams indicated the total aromatic carbon decreased more than humic substances content. Moreover, the larger E/E for D-WF in summer indicated that the humic substances were richer in fulvic acids than humic acids. Soil disturbance associated with forestry-felling likely contributed to the higher [DOC] and release of less-humified material in D-FF. This research indicates drivers of different DOC concentration and composition can exist even in small catchments.

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The Effect of Storage on the Radiocarbon, Stable Carbon and Nitrogen Isotopic Signatures and Concentrations of Riverine DOM

Cited by 18 publications

References 22 publications

Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

Fluvial organic carbon fluxes from oil palm plantations on tropical peatland

Fluvial dissolved organic carbon composition varies spatially and seasonally in a small catchment draining a wind farm and felled forestry

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