Sources and cycling of dissolved black carbon (DBC) in rivers and ocean revealed by carbon isotopes

2020 ◽  
Author(s):  
Xuchen Wang
Keyword(s):  
Black Carbon ◽  
Carbon Isotope ◽  
Drainage Basin ◽  
Solid Phase ◽  
Stable Carbon Isotope ◽  
Balance Model ◽  
Isotope Mass Balance ◽  
World Rivers ◽  
Spe Method ◽  
Isotope Mass Balance Model

<p><strong>Abstract</strong></p><p>Dissolve black carbon (DBC) has been recently recognized as an important fraction of dissolved organic carbon (DOC) in both rivers and ocean. It is estimated that about 10% of the riverine DOC transported by the world rivers could be DBC. The sources and fate of DBC in both rivers and ocean, however, is not well known. In this study, we present radiocarbon (<sup>14</sup>C) and stable carbon isotope (<sup>13</sup>C) measurements of DBC in several large rivers in China, and in coastal and open ocean waters. DBC was concentrated using solid phase extraction (SPE) method and quantified by chemothermal oxidation (CTO) method.</p><p>Concentrations of DBC varied in rivers depending on the drainage basin of the river and accounted for 3.7-7.6% of the riverine DOC pool. DBC was slightly lower, accounted for 2.9-5.9% of DOC in coastal and open oceans. Carbon isotope results indicate that DBC δ<sup>13</sup>C values were all slightly enriched (by 2-3‰) than the values of DOC in both rivers and ocean. The DBC Δ<sup>14</sup>C values varied largely in rivers and the values were significantly higher than DOC Δ<sup>14</sup>C values in rivers but similar to DOC Δ<sup>14</sup>C values in the ocean. Using a two-end member isotope mass balance model, we calculated that the most DBC (80%) with relatively young <sup>14</sup>C ages in the rivers was derived from biomass burning. Laboratory incubation studies also found that DBC released from recent charcoal was able to be utilized by bacteria, supporting the speculation that river transported DOC could be decomposed during estuaries mixing. Our study suggests that DBC is cycled in the same time scales with the DOC pool in the ocean and no extremely older DBC was identified as reported in other studies previously.</p>

scholarly journals APPLYING URANIUM-SERIES ISOTOPE GEOCHEMISTRY AND GEOCHRONOLOGY TO GREAT BASIN PLEISTOCENE PALEOHYDROLOGY

2018 ◽  
Author(s):  
Daniel Enrique Ibarra
Keyword(s):  
Mass Balance ◽  
Lake Level ◽  
Climate Model ◽  
Balance Model ◽  
Mass Balance Model ◽  
Model Simulations ◽  
Isotope Mass Balance ◽  
Climate Model Simulations ◽  
Lake Systems ◽  
Isotope Mass Balance Model

The widespread lake systems of the Basin and Range during the late Pleistocene indicate substantially greater moisture availability during glacial periods relative to modern. To determine the hydrography of the most recent lake cycle, we dated shoreline tufa deposits from wave-cut lake terraces in Surprise Valley, California. The lake hydrograph is constrained by 230Th-U ages on 22 tufa samples paired with 15 radiocarbon ages. This new lake hydrograph places the highest lake level 176 m above the present- day playa at >15.23 ± 0.36 ka cal BP (14C age). During the Last Glacial Maximum (LGM, ~19 to 26 ka), Lake Surprise stood at moderate levels, 65 to 99 m above modern playa. Temporally, the Lake Surprise highstand slightly postdates the Lake Lahontan highstand and corresponds to several post-LGM highstands and stillstands of smaller lake systems farther east. To further evaluate climatic forcings associated with lake-level changes, we use an oxygen isotope mass balance model combined with an analysis of predictions from the Paleoclimate Model Intercomparison Project 3 (PMIP3) climate model ensemble. Our isotope mass balance model predicts minimal precipitation increases of only 2.5 to 18.2% (average = 9.5%) during the LGM relative to modern, compared to an approximately 75% increase in precipitation during the 15.23 ka highstand when lake surface area increased by 138%. LGM PMIP3 climate model simulations corroborate these findings, predicting an average precipitation increase of only 6.5% relative to modern, accompanied by a 28% decrease in total evaporation propelled by a 7°C decrease in mean annual temperature. LGM climate model simulations also suggest a seasonal decoupling of runoff and precipitation, with peak runoff shifting to the late spring. Based on our coupled analysis, we propose that moderate lake levels during the LGM were driven by reduced evaporation, a result of reduced summer insolation, and not by increased precipitation. Reduced evaporation primed Basin and Range lake systems, particularly smaller, isolated basins such as Surprise Valley, to rapidly respond to increased precipitation during late-Heinrich Stadial 1 (HS1, ~14.5 to 19 ka). Post-LGM highstands were potentially driven by increased rainfall during HS1 brought by latitudinally extensive and strengthened mid-latitude westerly storm tracks, the effects of which are recorded in the lacustrine and glacial records as far south as ~32°N. These results suggest that seasonal insolation, in particular the effect of summer insolation on lake evaporation, provides a previously under-investigated long-term driver of moisture availability in the western United States.

scholarly journals Method for determination of stable carbon isotope ratio of methylnitrophenols in atmospheric PM

2011 ◽  
Vol 4 (3) ◽  
pp. 3199-3231
Author(s):  
S. Moukhtar ◽  
M. Saccon ◽  
A. Kornilova ◽  
S. Irei ◽  
L. Huang ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Stable Isotope ◽  
Carbon Isotope ◽  
Isotope Ratio ◽  
Solid Phase ◽  
Stable Carbon Isotope ◽  
Stable Isotope Ratio ◽  
Atmospheric Particulate Matter ◽  
Stable Carbon ◽  
Ms Analysis

Abstract. A technique for the measurement of the stable isotope ratio of methylnitrophenols in atmospheric particulate matter (PM) is presented. It has been found in numerous laboratory studies that these compounds are photooxidation products of toluene in PM. Atmospheric samples from rural and suburban areas were collected for evaluation of the procedure. PM was collected on quartz fibre filters using dichotomous high volume air samplers for PM 2.5. Methylnitrophenols were extracted from the filters using acetonitrile. The sample was then purified using a combination of high-performance liquid chromatography (HPLC) and solid phase extraction (SPE). The final solution was then divided into two aliquots. To one aliquot, a derivatising agent, Bis(trimethylsilyl)trifluoroacetamide (BSTFA), was added to the solution for Gas Chromatography/Mass Spectroscopy (GC/MS) analysis. The second half of the sample was stored at low temperature. When GC/MS analysis showed high enough concentrations the remaining sample was derivatized with BSTFA and analysed for stable isotope ratio using a Gas Chromatography/Isotope Ratio Mass Spectrometry (GC-IRMS). In all atmospheric PM samples analysed, 2-methyl-4-nitrophenol was found to be the most abundant methylnitrophenol. Nevertheless, due to low pollution levels occurring in the rural area, no samples had concentrations high enough to perform stable carbon isotope composition measurements of the methylnitrophenols. Samples collected in the suburban area could be analysed for carbon stable isotope ratio using GC-IRMS. The procedure described in this paper provides a very sensitive and selective method for the analysis of methylnitrophenols in atmospheric PM at concentrations as low as 1 pg m−3. For accurate (within ±0.5‰) stable isotope ratio analysis significantly higher concentrations in the range of 100 pg m−3 or more are required.

Source Apportionment of Particulate Matter Based on Carbon Isotope Mass Balance Model

2013 ◽  
Vol 295-298 ◽  
pp. 1565-1569 ◽  
Author(s):  
Jian Qiang Zhang ◽  
Lin Peng ◽  
Hui Ling Bai ◽  
Xiao Feng Liu ◽  
Ling Mu
Keyword(s):  
Mass Balance ◽  
Source Apportionment ◽  
Coal Dust ◽  
Balance Model ◽  
Mass Balance Model ◽  
Soil Dust ◽  
Vehicle Exhaust ◽  
Carbon Isotopic ◽  
Isotope Mass Balance ◽  
Isotope Mass Balance Model

In the process of source apportionment for particulate matter by mass balance model, the colinearity between various source profiles leads to the different analyzing results. For this reason, carbon isotopic apportionment based on the difference in carbon isotopic composition of particulate from different sources was put forward in this study. On the basis of chemical mass balance model, carbon isotope mass balance model is built to discriminate the sources including soil dust, coal dust and vehicle exhaust dust. This improved method has been used in the source apportionment of particulate in Taiyuan, and the results showed that the contributions of vehicle exhaust dust, coal dust and soil dust to air particulate in Taiyuan are 45%,13% and 18% respectively in heating season, while 23%,21% and16% in non-heating season. Therefore, the control of ash fly from burning coal is a long-term and arduous task.

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