In Situ Measurement of the Settling Velocity Profile of Particulate Organic Carbon in Lake Ontario

Depth profiles of calm water settling velocities were measured in situ using specially constructed sampling bottles. Samples of water were taken at specific depths and the settling process commenced as soon as the samples were taken. Just before retrieval of the bottles, the samples were subdivided into upper and lower portions so that settling velocities could be calculated; these varied between − 0.4 and + 2.0 m day−1. Net settling velocities measured at the top of the thermocline were used to estimate net settling fluxes from the epilimnion; these varied between − 0.074 and + 0.336 mmoles of phosphorus m−2 day−1. Net settling flux can differ from sedimentation flux out of the epilimnion and the necessity for a clear distinction between these two values is emphasized.

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The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

10.26434/chemrxiv.7803698 ◽

2019 ◽

Author(s):

Michael Stukel ◽

Thomas Kelly

Keyword(s):

Organic Carbon ◽

Water Column ◽

Particulate Organic Carbon ◽

Transport Model ◽

California Current ◽

In Situ Measurements ◽

Power Law Distribution ◽

Sinking Particles ◽

Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

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Estimation of the Particulate Organic Carbon to Chlorophyll-a Ratio Using MODIS-Aqua in the East/Japan Sea, South Korea

Remote Sensing ◽

10.3390/rs12050840 ◽

2020 ◽

Vol 12 (5) ◽

pp. 840 ◽

Cited By ~ 1

Author(s):

Dabin Lee ◽

SeungHyun Son ◽

HuiTae Joo ◽

Kwanwoo Kim ◽

Myung Joon Kim ◽

...

Keyword(s):

Organic Carbon ◽

Particulate Organic Carbon ◽

Chlorophyll A ◽

Primary Productivity ◽

Seasonal Variability ◽

Japan Sea ◽

Global Ocean ◽

Phytoplankton Communities

In recent years, the change of marine environment due to climate change and declining primary productivity have been big concerns in the East/Japan Sea, Korea. However, the main causes for the recent changes are still not revealed clearly. The particulate organic carbon (POC) to chlorophyll-a (chl-a) ratio (POC:chl-a) could be a useful indicator for ecological and physiological conditions of phytoplankton communities and thus help us to understand the recent reduction of primary productivity in the East/Japan Sea. To derive the POC in the East/Japan Sea from a satellite dataset, the new regional POC algorithm was empirically derived with in-situ measured POC concentrations. A strong positive linear relationship (R2 = 0.6579) was observed between the estimated and in-situ measured POC concentrations. Our new POC algorithm proved a better performance in the East/Japan Sea compared to the previous one for the global ocean. Based on the new algorithm, long-term POC:chl-a ratios were obtained in the entire East/Japan Sea from 2003 to 2018. The POC:chl-a showed a strong seasonal variability in the East/Japan Sea. The spring and fall blooms of phytoplankton mainly driven by the growth of large diatoms seem to be a major factor for the seasonal variability in the POC:chl-a. Our new regional POC algorithm modified for the East/Japan Sea could potentially contribute to long-term monitoring for the climate-associated ecosystem changes in the East/Japan Sea. Although the new regional POC algorithm shows a good correspondence with in-situ observed POC concentrations, the algorithm should be further improved with continuous field surveys.

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Source, transport and fluxes of Amazon River particulate organic carbon: Insights from river sediment depth-profiles

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2014.02.032 ◽

2014 ◽

Vol 133 ◽

pp. 280-298 ◽

Cited By ~ 66

Author(s):

Julien Bouchez ◽

Valier Galy ◽

Robert G. Hilton ◽

Jérôme Gaillardet ◽

Patricia Moreira-Turcq ◽

...

Keyword(s):

Organic Carbon ◽

Particulate Organic Carbon ◽

River Sediment ◽

Amazon River ◽

Sediment Depth ◽

Depth Profiles

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Volatile and intermediate volatility organic compounds in suburban Paris: variability, origin and importance for SOA formation

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-10439-2014 ◽

2014 ◽

Vol 14 (19) ◽

pp. 10439-10464 ◽

Cited By ~ 47

Author(s):

W. Ait-Helal ◽

A. Borbon ◽

S. Sauvage ◽

J. A. de Gouw ◽

A. Colomb ◽

...

Keyword(s):

Organic Carbon ◽

Particulate Organic Carbon ◽

Organic Compounds ◽

Regional Scale ◽

Integrated Approach ◽

Anthropogenic Sources ◽

Time Resolved ◽

Times Series

Abstract. Measurements of gaseous and particulate organic carbon were performed during the MEGAPOLI experiments, in July 2009 and January–February 2010, at the SIRTA observatory in suburban Paris. Measurements comprise primary and secondary volatile organic compounds (VOCs), of both anthropogenic and biogenic origins, including C12–C16 n-alkanes of intermediate volatility (IVOCs), suspected to be efficient precursors of secondary organic aerosol (SOA). The time series of gaseous carbon are generally consistent with times series of particulate organic carbon at regional scale, and are clearly affected by meteorology and air mass origin. Concentration levels of anthropogenic VOCs in urban and suburban Paris were surprisingly low (2–963 ppt) compared to other megacities worldwide and to rural continental sites. Urban enhancement ratios of anthropogenic VOC pairs agree well between the urban and suburban Paris sites, showing the regional extent of anthropogenic sources of similar composition. Contrary to other primary anthropogenic VOCs (aromatics and alkanes), IVOCs showed lower concentrations in winter (< 5 ppt) compared to summer (13–27 ppt), which cannot be explained by the gas-particle partitioning theory. Higher concentrations of most oxygenated VOCs in winter (18–5984 ppt) suggest their dominant primary anthropogenic origin. The respective role of primary anthropogenic gaseous compounds in regional SOA formation was investigated by estimating the SOA mass concentration expected from the anthropogenic VOCs and IVOCs (I / VOCs) measured at SIRTA. From an integrated approach based on emission ratios and SOA yields, 38 % of the SOA measured at SIRTA is explained by the measured concentrations of I / VOCs, with a 2% contribution by C12–C16 n-alkane IVOCs. From the results of an alternative time-resolved approach, the average IVOC contribution to SOA formation is estimated to be 7%, which is half of the average contribution of the traditional aromatic compounds (15%). Both approaches, which are based on in situ observations of particular I / VOCs, emphasize the importance of the intermediate volatility compounds in the SOA formation, and support previous results from chamber experiments and modeling studies. They also support the need to make systematic the IVOCs' speciated measurement during field campaigns.

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Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)

Biogeosciences ◽

10.5194/bg-9-2045-2012 ◽

2012 ◽

Vol 9 (6) ◽

pp. 2045-2062 ◽

Cited By ~ 62

Author(s):

S. Bouillon ◽

A. Yambélé ◽

R. G. M. Spencer ◽

D. P. Gillikin ◽

P. J. Hernes ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Particulate Organic Carbon ◽

Seasonal Variations ◽

Dissolved Inorganic Carbon ◽

Low Flow ◽

Tropical Rivers ◽

Particulate Nitrogen ◽

Congo River

Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long, 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8‰, and −31.8 to −27.1‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6‰ in δ13C signatures. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions, consistent with major seasonal variations in the sources of dissolved organic matter. We observed a strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q < 1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. The low POC/PN ratios, high %POC and low and variable δ13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent approaches averaged 105 and 204 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions. The total annual flux of TSM, POC, PN, DOC and DIC are 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~30% higher and bicarbonate fluxes were ~35% lower than previous reports. DIC represented 58% of the total annual C flux, and under the assumptions that carbonate weathering represents 25% of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~50% of terrestrial-derived riverine C transport.

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Particulate organic carbon–234Th relationships in particles separated by settling velocity in the northwest Mediterranean Sea

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2008.12.017 ◽

2009 ◽

Vol 56 (18) ◽

pp. 1519-1532 ◽

Cited By ~ 18

Author(s):

J. Szlosek ◽

J.K. Cochran ◽

J.C. Miquel ◽

P. Masqué ◽

R.A. Armstrong ◽

...

Keyword(s):

Organic Carbon ◽

Mediterranean Sea ◽

Particulate Organic Carbon ◽

Settling Velocity

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In situ measurement of the settling velocity of organic carbon particles and 10 species of phytoplankton

Limnology and Oceanography ◽

10.4319/lo.1980.25.5.0855 ◽

1980 ◽

Vol 25 (5) ◽

pp. 855-864 ◽

Cited By ~ 86

Author(s):

N. M. Burns ◽

F. Rosa

Keyword(s):

Organic Carbon ◽

Settling Velocity ◽

In Situ Measurement ◽

Carbon Particles

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High variability of particulate organic carbon export along the North Atlantic GEOTRACES section GA01 as deduced from <sup>234</sup>Th fluxes

Biogeosciences ◽

10.5194/bg-15-6417-2018 ◽

2018 ◽

Vol 15 (21) ◽

pp. 6417-6437 ◽

Cited By ~ 10

Author(s):

Nolwenn Lemaitre ◽

Frédéric Planchon ◽

Hélène Planquette ◽

Frank Dehairs ◽

Debany Fonseca-Batista ◽

...

Keyword(s):

Organic Carbon ◽

Particulate Organic Carbon ◽

North Atlantic ◽

Size Fraction ◽

Material Surface ◽

The North ◽

Poc Export ◽

The North Atlantic ◽

Iberian Margin

Abstract. In this study we report particulate organic carbon (POC) export fluxes for different biogeochemical basins in the North Atlantic as part of the GEOTRACES GA01 expedition (GEOVIDE, May–June 2014). Surface POC export fluxes were deduced by combining export fluxes of total Thorium-234 (234Th) with the ratio of POC to 234Th of sinking particles at the depth of export. Particles were collected in two size classes (>53 and 1–53 µm) using in situ pumps and the large size fraction was considered representative of sinking material. Surface POC export fluxes revealed latitudinal variations between provinces, ranging from 1.4 mmol m−2 d−1 in the Irminger basin, where the bloom was close to its maximum, to 12 mmol m−2 d−1 near the Iberian Margin, where the bloom had already declined. In addition to the state of progress of the bloom, variations of the POC export fluxes were also related to the phytoplankton size and community structure. In line with previous studies, the presence of coccolithophorids and diatoms appeared to enhance the POC export flux, while the dominance of picophytoplankton cells, such as cyanobacteria, resulted in lower fluxes. The ratio of POC export to primary production (PP) strongly varied regionally and was generally low (≤14 %), except at two stations located near the Iberian Margin (35 %) and within the Labrador basin (38 %), which were characterized by unusual low in situ PP. We thus conclude that during the GEOVIDE cruise, the North Atlantic was not as efficient in exporting carbon from the surface, as reported earlier by others. Finally, we also estimated the POC export at 100 m below the surface export depth to investigate the POC transfer efficiencies. This parameter was also highly variable amongst regions, with the highest transfer efficiency at sites where coccolithophorids dominated.

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