scholarly journals Evaluation of a 2-step thermal method for separating organic and elemental carbon for radiocarbon analysis

2014 ◽  
Vol 7 (1) ◽  
pp. 131-169 ◽  
Author(s):  
U. Dusek ◽  
M. Monaco ◽  
M. Prokopiou ◽  
F. Gongriep ◽  
R. Hitzenberger ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Humic Acid ◽  
Organic Carbon ◽  
Organic Compounds ◽  
Strong Evidence ◽  
Elemental Carbon ◽  
Intermediate Temperature ◽  
Thermal Method ◽  
Intermediate Step ◽  
Temperature Step

Abstract. We thoroughly characterized a system for thermal separation of organic carbon (OC) and elemental carbon (EC) for subsequent radiocarbon analysis. Different organic compounds as well as ambient aerosol filter samples were introduced into an oven system and combusted to CO2 in pure O2. The main objective was to test which combustion times and temperatures are best suited to separate OC and EC. The final separation step for OC was combustion at 360 °C for 15 min. Combustion at this temperature proved enough to remove several organic test substances from the filter (including high molecular weight humic acid) but did not remove substantial amounts of EC. For isolation of EC, OC first needs to be completely removed from the filter. This was achieved by water extraction of the filter, followed by combustion of the water insoluble OC at 360 °C and combustion at an intermediate temperature step of 2 min at 450 °C. This last step removed the most refractory OC together with some EC. Finally, the remaining EC was combusted to CO2 at 650 °C. The recovery of black carbon after the intermediate 450 °C step was approximately 80%. Several tests provided strong evidence that OC was removed efficiently during the intermediate temperature step: (i) brown carbon, indicative of refractory OC, was removed; (ii) the fraction modern of EC did not decrease significantly if the temperature of the intermediate step was further increased. Based on tests with various organic compounds, we estimated that charred organic carbon could contribute 4–8% to an elemental carbon sample that was isolated according to our method.

scholarly journals Evaluation of a two-step thermal method for separating organic and elemental carbon for radiocarbon analysis

2014 ◽  
Vol 7 (7) ◽  
pp. 1943-1955 ◽  
Author(s):  
U. Dusek ◽  
M. Monaco ◽  
M. Prokopiou ◽  
F. Gongriep ◽  
R. Hitzenberger ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Humic Acid ◽  
Organic Carbon ◽  
Organic Compounds ◽  
Strong Evidence ◽  
Elemental Carbon ◽  
Intermediate Temperature ◽  
Thermal Method ◽  
Intermediate Step ◽  
Temperature Step

Abstract. We thoroughly characterized a system for thermal separation of organic carbon (OC) and elemental carbon (EC) for subsequent radiocarbon analysis. Different organic compounds as well as ambient aerosol filter samples were introduced into an oven system and combusted to CO2 in pure O2. The main objective was to test which combustion times and temperatures are best suited to separate OC and EC. The final separation step for OC was combustion at 360 °C for 15 min. Combustion at this temperature proved enough to remove several organic test substances from the filter (including high molecular weight humic acid) but did not remove substantial amounts of EC. For isolation of EC, OC first needs to be completely removed from the filter. This was achieved by water extraction of the filter, followed by combustion of the water insoluble OC at 360 °C and combustion at an intermediate temperature step of 2 min at 450 °C. This last step removed the most refractory OC together with some EC. Finally, the remaining EC was combusted to CO2 at 650 °C. The recovery of black carbon after the intermediate 450 °C step was approximately 80%. Several tests provided strong evidence that OC was removed efficiently during the intermediate temperature step: (i) brown carbon, indicative of refractory OC, was removed; (ii) the fraction modern of EC did not decrease significantly if the temperature of the intermediate step was further increased. Based on tests with various organic compounds, we estimated that charred organic carbon could contribute 4–8% to an elemental carbon sample that was isolated according to our method.

scholarly journals Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

2017 ◽  
Author(s):  
Ryan D. Cook ◽  
Ying-Hsuan Lin ◽  
Zhuoyu Peng ◽  
Eric Boone ◽  
Rosalie K. Chu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Carbon ◽  
High Molecular Weight ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Water Samples ◽  
Cloud Water ◽  
Molecular Composition ◽  
Oxidation Products ◽  
Aerosol Formation

Abstract. Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York during August–September 2014 were analyzed by ultrahigh-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous phase processes of the observed high molecular weight organic compounds. The molecular composition of the cloud water depended on the influencing sources (biogenic, urban, wildfire) and showed evidence of aqueous-phase processes. Cloud water acidity was correlated with the average oxygen:carbon ratio of the organic constituents, suggesting the influence of aqueous acid-catalyzed oxidation processes. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C10-12) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic/urban, and urban-influenced).

scholarly journals Association of fresh low-molecular-weight organic compounds with clay-sized mineral fraction in soils of different organic carbon loading

Geoderma ◽  
2022 ◽  
Vol 409 ◽  
pp. 115657
Author(s):  
Tianyi Wu ◽  
Alexander D. Ost ◽  
Jean-Nicolas Audinot ◽  
Martin Wiesmeier ◽  
Tom Wirtz ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Carbon ◽  
Organic Compounds ◽  
Low Molecular Weight ◽  
Mineral Fraction ◽  
Organic Carbon Loading ◽  
Carbon Loading

scholarly journals Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

2017 ◽  
Vol 17 (24) ◽  
pp. 15167-15180 ◽  
Author(s):  
Ryan D. Cook ◽  
Ying-Hsuan Lin ◽  
Zhuoyu Peng ◽  
Eric Boone ◽  
Rosalie K. Chu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Carbon ◽  
High Molecular Weight ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Water Samples ◽  
Cloud Droplet ◽  
Cloud Water ◽  
Molecular Composition ◽  
Cloud Droplets

Abstract. Organic aerosol formation and transformation occurs within aqueous aerosol and cloud droplets, yet little is known about the composition of high molecular weight organic compounds in cloud water. Cloud water samples collected at Whiteface Mountain, New York, during August–September 2014 were analyzed by ultra-high-resolution mass spectrometry to investigate the molecular composition of dissolved organic carbon, with a focus on sulfur- and nitrogen-containing compounds. Organic molecular composition was evaluated in the context of cloud water inorganic ion concentrations, pH, and total organic carbon concentrations to gain insights into the sources and aqueous-phase processes of the observed high molecular weight organic compounds. Cloud water acidity was positively correlated with the average oxygen : carbon ratio of the organic constituents, suggesting the possibility for aqueous acid-catalyzed (prior to cloud droplet activation or during/after cloud droplet evaporation) and/or radical (within cloud droplets) oxidation processes. Many tracer compounds recently identified in laboratory studies of bulk aqueous-phase reactions were identified in the cloud water. Organosulfate compounds, with both biogenic and anthropogenic volatile organic compound precursors, were detected for cloud water samples influenced by air masses that had traveled over forested and populated areas. Oxidation products of long-chain (C10−12) alkane precursors were detected during urban influence. Influence of Canadian wildfires resulted in increased numbers of identified sulfur-containing compounds and oligomeric species, including those formed through aqueous-phase reactions involving methylglyoxal. Light-absorbing aqueous-phase products of syringol and guaiacol oxidation were observed in the wildfire-influenced samples, and dinitroaromatic compounds were observed in all cloud water samples (wildfire, biogenic, and urban-influenced). Overall, the cloud water molecular composition depended on air mass source influence and reflected aqueous-phase reactions involving biogenic, urban, and biomass burning precursors.

Phase-partitioning and chemical reactions of low molecular weight organic compounds in fog

Tellus B ◽  
1992 ◽  
Vol 44 (5) ◽  
pp. 533-544 ◽  
Author(s):  
M. C. Facchini ◽  
S. Fuzzi ◽  
J. A. Lind ◽  
H. Fierlinger-Oberlinninger ◽  
M. Kalina ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Compounds ◽  
Chemical Reactions ◽  
Low Molecular Weight ◽  
Phase Partitioning

Characteristics of fouling due to clay-organic substances in potable water treatment by ultrafiltration

1996 ◽  
Vol 34 (9) ◽  
pp. 157-164 ◽  
Author(s):  
Kim C.-H. ◽  
M. Hosomi ◽  
A. Murakami ◽  
M. Okada
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Humic Acid ◽  
Fulvic Acid ◽  
Size Distribution ◽  
Ultrafiltration Membrane ◽  
Organic Substances ◽  
Decomposition Products ◽  
Microbial Decomposition ◽  
Fouling Materials

Effects of clay on fouling due to organic substances and clay were evaluated by model fouling materials and kaolin. Model fouling materials selected were protein, polysaccharide, fulvic acid, humic acid and algogenic matter (EOM:ectracellular organic matter, microbial decomposition products) and kaolin was selected as the clay material. Polysulfone membrane (MWCO(Molecular Weight Cut-Off) 10,000, 50,000 and 200,000) was used as an ultrafiltration membrane. In particular, the flux measurement of solutions containing algogenic matter used an ultrafiltration membrane of MWCO 50,000. The flux of protein and polysaccharide with coexistence of kaolin increased in the case of the ratio of MW/MWCO being greater than one, but did not increase in the case of the MW/MWCO ratio being below one. In contrast, the flux of fulvic acid and humic acid with coextence of kaolin decreased regardless of the ratio of MW/MWCO. The addition of dispersion agent and coagulant in the organic substances and kaolin mixture solution changed the size distribution of kaolin, and resulted in a change of the flux. EOM and microbial decomposition products decreased with the increase of the fraction of organic matter having molecular weight more than MWCO of membrane. The flux of the algogenic organic matter with coexistence of kaolin decreased with the increase of the amount of kaolin. It was suggested that the decline of the flux with coexistence of kaolin was due to the change of the resistance of the kaolin cake layer corresponding to the change in kaolin size distribution with charge.

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