Δ 14 C and Concentra.on of Black Carbon in California Coastal Sediments

Transcription

1 Δ 14 C and Concentra.on of Black Carbon in California Coastal Sediments Alysha Coppola, Lori Ziolkowski and Ellen Druffel University of California Irvine- Druffel Group 1 st IWA Natural Organic MaGer Conference

2 DefiniIons Dissolved Organic Carbon (DOC) Dissolved Inorganic Carbon (DIC) Sedimentary Organic Carbon (SOC) Black Carbon (BC)

3 Black Carbon s Importance BC ConInuum RadiaIve balance Carrier of organic pollutants Air quality, health effects Char Soot FormaIon of atmospheric brown clouds SequestraIon of carbon: Biochar

4 Black Carbon is produced from Incomplete CombusIon Soot BC Char BC Goldberg, 1985

5 Imbalance in the Global Cycle of BC Emission as aerosols Atmospheric BC vegeta.on fires Tg C/yr Residues of biomass burning Fluxes in Gt/yr Standing stocks 5-27 Gt C/yr Fossil fuel burning <10% Soils??? <10% River DOC To ocean Gt C/yr Deposi.on open ocean surface coastal ocean surface Oceanic BC In DOC?? ~0.01 Gt C/yr Deposi.on to sediments 0.01 ~15% (Kuhlbusch, 1998; Suman et al., 1997; Penner et al., 1993; Masiello 2000)

6 Start by looking in ocean sediments: Emission as aerosols Atmospheric BC vegeta.on fires Tg C/yr Residues of biomass burning Fluxes in Gt/yr Standing stocks 5-27 Gt C/yr Fossil fuel burning <10% Soils??? <10% River DOC To ocean Gt C/yr Deposi.on open ocean surface coastal ocean surface Oceanic BC In DOC?? Deposi.on ~0.01 to Gt sediments C/yr 0.01 ~15% (Kuhlbusch, 1998; Suman et al., 1997; Penner et al., 1993; Masiello 2000)

7 Imbalance in the Global Cycle of BC Emission as aerosols Atmospheric BC vegeta.on fires Tg C/yr Residues of biomass burning Fluxes in Gt/yr Standing stocks QuanIfying the BC reservoir in 5-27 Gt C/yr Fossil fuel burning sediments offers clues as to where the missing BC resides <10% Soils??? <10% River DOC To ocean Gt C/yr Deposi.on open ocean surface coastal ocean surface Oceanic BC In DOC?? ~0.01 Gt C/yr Deposi.on to sediments 0.01 ~15% (Kuhlbusch, 1998; Suman et al., 1997; Penner et al., 1993; Masiello 2000)

8 Use of Different Methods Difficult to give global esimates of BC in reservoirs MulIple methods Inter- comparison study (Hammes et al., 2007)

9 Δ 14 C in atmospheric CO 2 and ocean DI 14 C McNichol and Aluwihare, 2007

10 Radiocarbon in the Environment McNichol and Aluwihare, 2007

11 A refractory component in DOC: DOC 4,000-6, C yrs DIC 700-2, C yrs Δ 14 C ( ) DOC ~2, C yrs older than DIC N. AtlanIc N.C. Pacific Southern Ocean Depth (km) DOC DIC (Druffel and Bauer, 2000)

12 EsImaIng the amount of BC in DOC using SOC NE Pacific (Masiello and Druffel, 1998) BC BC Residence Ime= 2, C yrs Flux of OC to oceans=0.01 Gt C/yr Non- BC SOC Non- BC SOC DOC pool=685 Gt C How much BC could be in DOC? (O.01 Gt C/yr)*(2, C yrs) 685 Gt C = ~4% of DOC could be BC in the NE Pacific ~2μM

13 My findings in NE Pacific sediments Using BPCA method Same sediment core Residence Ime=5, C yrs (O.01 Gt C/yr)*(5, C yrs) 685 Gt C ~9±3% of DOC could be BC in the NE Pacific = Depth (cm) C age (kyr BP) Non-BC SOC BC 30 5,900 ± C yr

14 RaIo of BC/OC in sediments Using BPCA method, BC/OC 4% BC/OC % BC/OC using dichromate sulfuric acid method (Masiello and Druffel, 1998) Less BC is present, but 14 C ages are older using BPCA method Sediment Depth (cm) BPCA, this work Masiello and Druffel (1998) 30 70% lower

15 BC structure in sediments 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% nmnm depth from surface (cm) B6CA B5CA B4CA B3CA Increasing resistance against degradaion

16 BC in DOC and Sediments DOC BC had less condensed structure of BC 100% 80% 60% 40% 20% 0% B5CA B4CA B3CA NE Pacific BC in DOC # Depth (m) BC in DOC: 20,100 ± C yrs BC in Sediments: 9,500 ± C yrs (Ziolkowski and Druffel, 2010) DOC: 4,500-6, C yrs

17 BC in DOC and Sediments DOC BC had less condensed structure of BC Sedimentary BC had more condensed structure B6CA (resistant to degradaion) may be present in low molecular weight DOC pool NE Pacific BC in sediments 100% 80% 60% 40% 20% 0% B6CA B5CA B4CA B3CA # Depth (m) BC in DOC: 20,100 ± C yrs BC in Sediments: 9,500 ± C yrs DOC: 4,500-6, C yrs

18 Summary and Future Work! dfsd Imbalance in the BC budget Use of BPCA method for same sediments BC/OC ~70% lower ±900 Tg 14 C/yr C yrs older than dichromate sulfuric acid method in mixed layer Pacific Ocean Future work: 5-27 Gt C/yr 0.02 Gt C/yr Measure BC in DOC Compare to DOC Δ<10% 14 C profiles to BC Δ 14 C measurements Other missing BC reservoirs? BC measurements with complementary DOC measurements How much of the missing BC is in DOC? ~0.01 Gt C/yr (Ziolkowski and Druffel, 2010)

19 Green River Shale vs. Sediments 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% average sediment distribuion green river shale Shale BPCA distribuion is not addiive, suggests shale is not present Asphaltene would produce mainly B3CAs, which are not abundant in sediments

20 A change in structure is also observed from riverine BC to oceanic BC Emission as aerosols Atmospheric BC BPCA DistribuIon Fossil fuel combusion Tg C/yr Tg C/yr Residues of vegetaion fires 5-27 Gt C/yr Biomass Burning Tg C/yr Soil BC <10% <10% 20 Tg C/yr Soil erosion River runoff 0.02 Gt C/yr Suwanee Amazon Mid- AtlanIc AtlanIc NC Pacific NE Pacific Sedimentary BC DeposiIon BC in DOC?? ~0.01 Gt C/yr ~10 Tg C/yr (Kuhlbusch, 1998; Suman et al., 1997; Penner et al., 1993; Masiello 2000) Ziolkowski and Druffel, 2010