Terrestrial c sequestration at elevated co2 and temperature: the role of dissolved organic n loss
Summary (2 min read)
1. INTRODUCTION
- Sandia National Laboratories has been a leader in the development of decontamination technologies for use against chemical and biological warfare (CBW) agents, toxic industrial chemicals and other toxins for use in both the military and civilian arenas.
- In the case of DF-200, the cleavage at this bond is enhanced by the presence of cationic micelles, which serve to attract and provide a nucleophilic-rich environment of the anionic species hydroxide, hydroperoxicarbonate, and hydroperoxide ions.
- Data collected under the micellar partition study can be compared to kinetics performance, to deduce how changes in the formulation chemistry impact performance.
- Potential customers and sponsors include DHS, military agencies (the Defense Threat Reduction Agency, and US Army Chemical Materials Agency), and public health and transportation industries.
2.1. Initial Dynamic Light Scattering Techniques
- Dynamic Light Scattering (DLS) - Dynamic light scattering measures the Brownian motion of molecules and particles in solution, from which size and size distributions may be determined.
- Consistent information on micelle size could not be acquired for the surfactant solutions using these dynamic or static light scattering techniques.
- Effervescence from the breakdown of peroxide (concentrations 3-5%) in solution interfered with the light scattering process, as gas particles passed through the detector cells.
- In parallel with the internal collection of DLS particle size data, Particle Technology Labs, an industry leader in particle analysis, was contacted to outsource analysis of select surfactant solutions for the determination of micelle size.
- Through recommendation of a fellow Sandian, UMN Characterization Facility personnel were contacted to perform scoping SAXS and cryo-TEM analyses, discussed in Section 2.2.1 and 2.3.
2.2. Small Angle Light Scattering
- In addition to cryo-TEM, Small Angle Light Scattering (SAXS) analyses was sought to characterize micelles in solution.
- For a brief overview of SAXS methodology, refer to the publication authored by Aswal.
- Several facilities with SAXS competency were identified and contacted.
- Two of the facilities, the University of Minnesota Characterization Facility and Argonne Advanced Photon Source expressed interest in collecting solution-based micelle characterization data.
- These independent efforts are described in the following sections.
2.2.3. Argonne Advanced Photon Source
- The purpose of the study undertaken at the Argonne Advanced Photon Source facility was to perform a controlled experiment, in which SAXS technique was used to characterize the surfactant phase changes (e.g., shape, size, etc.) of micelles following the addition of the components within the standard DF-200 formulation - note that peroxide was not included in this study.
- Note that the composition of solutions #5 and #6 are nearly the same; solution #5 was prepared in-house at Sandia National Laboratories, and solution #6 was the Part 1 surfactant mixture of the three-part commercial DF-200 product, EasyDecon.
- The set-up parameters for the experiments were: Photon energy, 12 KeV; Distance of sample to SAXS detector, 2.2 meters; Sample to WAXS detector distance, 48 cm. Solution 2, Solution 3, and Solution 4 displayed two broad peaks, but were not indicative of forming any micelle structure.
2.2.4. Conclusions of SAXS analyses
- Collectively, the results obtained by the SAXS technique provided insight to the micellar structures and approximate micelle sizes of the key surfactant component within the DF-200 base formulation and a variety of prospective surfactant solutions.
- The SAXS analyses were performed at three different facilities using differing instrumentation and methods, without the benefit of a standardized test method.
- Regardless, the micelle sizes were measured to be primarily in the range of 2-3 nm.
- The baseline data is novel in that it served as the initial indications of the micellar environment of surfactants representative of DF-200 and other prospective CBW decontamination formulations.
- To be of most value, future test matrices should be expanded to collect micellar characterization data over a range of surfactant, co-solvent and ionic concentrations.
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Citations
748 citations
Cites background from "Terrestrial c sequestration at elev..."
...The long-term CO2 stimulation of ecosystem C sequestration on a time scale of decades or longer relies on increases in total ecosystem N stocks (Rastetter et al. 1997, 2005, Luo et al. 2004)....
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Cites background from "Terrestrial c sequestration at elev..."
...This distinction is not reflected in current SOM models of SOM dynamics (Jenkinson et al., 1991; Parton et al. 1991; McGuire et al., 1997; Currie, 2003; Rastetter et al., 2005)....
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Cites background from "Terrestrial c sequestration at elev..."
...Some first-ordermodels include nutrients with nonlinear functions that capture the costs and benefits of nutrient acquisition [Rastetter et al., 2001, 2005;Wang et al., 2007; Houlton et al., 2008], but generally apply a first-order approach to soil C decomposition [equation (1)]....
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Frequently Asked Questions (14)
Q2. What are the future works in "Running head: role of don losses in carbon sequestration carbon sequestration in terrestrial ecosystems under elevated co2 and temperature: role of dissolved organic versus inorganic nitrogen loss" ?
The best potential for testing their ideas in a timely manner would be to experimentally manipulate ecosystems where the masking effects of within-ecosystem responses are likely to be small relative to the effects of DON losses to determine if there is a trend toward high C sequestration with low DON losses relative to DIN losses. Thus the manipulations should be on ecosystems where the C: N ratio of vegetation is low ( i. e., close to the C: N ratio of soils so that the redistribution of N has a smaller effect ), where the vegetation is unlikely to increase in woodiness ( i. e., to avoid the masking effects of increasing C: N ratios ), and where the total throughput of DON plus DIN is high ( i. e., a high potential to sequester N ). Their aim in this paper has been to examine how considering the relative magnitudes of DON versus DIN losses might influence assessments of potential C sequestration in terrestrial ecosystems. Their conclusions are that it is vital to quantify these fluxes at least in regards to evaluations of the long-term potential for C sequestration.
Q3. What can be done to help mask the effects of DON losses?
In addition, increases in plant and soil C:N ratios can contribute to the withinecosystem responses and help mask the effects of DON losses.
Q4. What is the effect of carbon sequestration in terrestrial ecosystems?
Terrestrial ecosystems are thought to sequester about 25% of the carbon (C) currentlyemitted through fossil-fuel burning and land-use change (IPCC 2001).
Q5. What is the way to test the effects of DON loss on the ecosystem?
The best potential for testing their ideas in a timely manner would be to experimentally manipulate ecosystems where the masking effects of within-ecosystem responses are likely to be small relative to the effects of DON losses to determine if there is a trend toward high C sequestration with low DON losses relative to DIN losses.
Q6. How long did the gradual-change simulations take to develop?
With high DON losses, N gains and losses were small during the first 100 years of all the simulations, and the dynamics in the gradual-change simulations generally lagged behind those in the instantaneous-change simulations by about two decades.
Q7. What is the effect of the gradual-change simulations on the sequestration of N?
Increases in plant and soil C:N ratios contributed less to C sequestration, but in amounts proportionately equivalent to their contributions in the instantaneous-change simulations.
Q8. What is the potential for accumulating N by limiting N losses in terrestrial ecosystems?
In this paper the authors argue that the amount of C sequestered in terrestrial ecosystems in response to elevated CO2 depends on the fraction of N losses that are in the form of dissolved organic N (DON) versus dissolved inorganic N (DIN); because plants can curtail DIN losses as N demand increases in response to elevated CO2, but plants have little control over DON losses, the potential for accumulating N by limiting N losses should be small if DON losses are high.
Q9. What is the effect of increasing the C:N ratio of soils on the ecosystem?
Because the C:N ratio of soils is about 25 and that of plants is about 143 (initial C:N values), this redistribution of N results in a net increase in the amount of C stored per unit N in the ecosystem.
Q10. What is the standard model of carbon sequestration in terrestrial ecosystems?
Their assessment of C sequestration in relation to DON losses relies upon threemodifications to what has been called "the standard model" of N accumulation in terrestrial ecosystems (Vitousek et al. 1998).
Q11. How much of the C sequestered in the ecosystems with low DON losses?
On average, the ecosystems sequestered only about 1 kg C m-2 between years 60 and 1000 or about 7% of the C sequestered during the first 60 years and 6% of the C sequestered in the ecosystems with low DON losses (Fig. 1).
Q12. How long does the C sequestration continue?
Sequestration of C continues for the duration of all low-DON-loss simulations, although at a rate that is only about 17% of that during the first 60 years (Fig. 1,Table 3).
Q13. Why did the models exhibit higher DOC loss?
Because of the explicit linkages between DOC and DON in the various model structures,simulations with higher DON loss also exhibit higher DOC loss.
Q14. What is the effect of elevated CO2 on the N stored in the ecosystem?
with a combination of elevated CO2 and warming, increases in woody tissues and the consequent increase in plant C:N ratio contributed significantly to an increase the C stored per unit N in the ecosystem (Fig. 2).