scholarly journals Downstream Evolution of Particulate Organic Matter Composition From Permafrost Thaw Slumps

2021 ◽  
Vol 9 ◽  
Author(s):  
Kirsi H. Keskitalo ◽  
Lisa Bröder ◽  
Sarah Shakil ◽  
Scott Zolkos ◽  
Suzanne E. Tank ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Matter ◽  
Global Climate ◽  
River Networks ◽  
Stream Networks ◽  
Stream Network ◽  
Stream System ◽  
Permafrost Soils ◽  
Peel Plateau

Permafrost soils, which store almost half of the global belowground organic carbon (OC), are susceptible to thaw upon climate warming. On the Peel Plateau of northwestern Canada, the number and size of retrogressive thaw slumps (RTS) has increased in recent decades due to rising temperatures and higher precipitation. These RTS features caused by the rapid thaw of ice-rich permafrost release organic matter dominantly as particulate organic carbon (POC) to the stream network. In this study, we sampled POC and streambank sediments along a fluvial transect (∼12 km) downstream from two RTS features and assessed the composition and degradation status of the mobilized permafrost OC. We found that RTS features add old, Pleistocene-aged permafrost POC to the stream system that is traceable kilometers downstream. The POC released consists mainly of recalcitrant compounds that persists within stream networks, whereas labile compounds originate from the active layer and appear to largely degrade within the scar zone of the RTS feature. Thermokarst on the Peel Plateau is likely to intensify in the future, but our data suggest that most of the permafrost OC released is not readily degradable within the stream system and thus may have little potential for atmospheric evasion. Possibilities for the recalcitrant OC to degrade over decadal to millennial time scales while being transported via larger river networks, and within the marine environment, do however, still exist. These findings add to our understanding of the vulnerable Arctic landscapes and how they may interact with the global climate.

scholarly journals Permafrost-Affected Soils of the Russian Arctic and their Carbon Pools

2014 ◽  
Vol 6 (1) ◽  
pp. 619-655
Author(s):  
S. Zubrzycki ◽  
L. Kutzbach ◽  
E.-M. Pfeiffer
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Sink ◽  
Global Climate ◽  
Fundamental Property ◽  
Climate System ◽  
The Arctic ◽  
Quaternary Period ◽  
Permafrost Regions

Abstract. Permafrost-affected soils have accumulated enormous pools of organic matter during the Quaternary Period. The area occupied by these soils amounts to more than 8.6 million km2, which is about 27% of all land areas north of 50° N. Therefore, permafrost-affected soils are considered to be one of the most important cryosphere elements within the climate system. Due to the cryopedogenic processes that form these particular soils and the overlying vegetation that is adapted to the arctic climate, organic matter has accumulated to the present extent of up to 1024 Pg (1 Pg = 1015 g = 1 Gt) of soil organic carbon stored within the uppermost three meters of ground. Considering the observed progressive climate change and the projected polar amplification, permafrost-affected soils will undergo fundamental property changes. Higher turnover and mineralization rates of the organic matter are consequences of these changes, which are expected to result in an increased release of climate-relevant trace gases into the atmosphere. As a result, permafrost regions with their distinctive soils are likely to trigger an important tipping point within the global climate system, with additional political and social implications. The controversy of whether permafrost regions continue accumulating carbon or already function as a carbon source remains open until today. An increased focus on this subject matter, especially in underrepresented Siberian regions, could contribute to a more robust estimation of the soil organic carbon pool of permafrost regions and at the same time improve the understanding of the carbon sink and source functions of permafrost-affected soils.

scholarly journals Particulate organic matter composition and organic carbon flux in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

2015 ◽  
Vol 12 (18) ◽  
pp. 15655-15685
Author(s):  
Z.-Y. Zhu ◽  
Y. Wu ◽  
S.-M. Liu ◽  
F. Wenger ◽  
J. Hu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Matter ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Concentration Data ◽  
Particulate Nitrogen ◽  
Organic Carbon Flux ◽  
Doc Concentration ◽  
The Face

Abstract. In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier–fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 μM, respectively, in August 2012. Amino acids (AAs) and phytoplankton pigments accounted for ~ 10 % of the particulate organic matter (POM) in the Bayelva River, while AAs represented > 90 % of particulate nitrogen in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounts for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for particulate nitrogen (PN) are much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6, 25 ± 5.6, and 4.7 ± 0.75 t, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 t yr−1) and DOC (0.02 ± 0.01 × 106 t yr−1) fluxes of Svalbard glaciers are small compared with those of the Greenland Ice Sheet, the area-weighted POC flux of Svalbard glaciers is twice that of the Greenland Ice Sheet, while the flux of DOC can be 4 to 7 times higher. Therefore, we propose that valley glaciers are efficient high-latitude sources of organic carbon.

Biogeochemical processes and labile composition of settling particulate organic matter in the south-west Pacific Ocean

2003 ◽  
Vol 54 (3) ◽  
pp. 259 ◽  
Author(s):  
Lallan Prasad Gupta ◽  
Hodaka Kawahata
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Matter ◽  
Deep Trap ◽  
Biogeochemical Processes ◽  
Shallow Trap ◽  
The South ◽  
Coral Sea ◽  
South West ◽  
Tasman Sea

Settling particles collected by sediment traps deployed for approximately 1 year in the Coral Sea and Tasman Sea were analysed to understand the biogeochemical processes controlling the cycling and flux of particulate organic matter (POM) in the south-west Pacific. Samples were analysed for 20 amino acids (AA) and two hexosamines (HA) and the data were interpreted together with already published data on opal (biogenic silica), organic carbon and total nitrogen contents. Mean fluxes of labile carbon and nitrogen at one site were significantly different (P < 0.04, t-test; n = 14–18) from those at other sites. The southernmost trap recorded the highest concentrations of AA, HA and organic carbon normalized AA. At a site in the south, POM was more degraded in the deep trap than in the shallow trap. Occasionally, higher fluxes were also recorded at the deep trap relative to the shallow trap. The C/Natomic ratio coupled with AA- and HA-based parameters clearly suggested contribution of POM through resuspension as well as lateral advection at the more southern site, whereas a strong influence of zooplankton on total mass flux was revealed at the northern site during the period August–September 1995. It is evident from the data that higher flux of particles having higher labile contents (AA and HA) is more prevalent in the Tasman Sea than in the Coral Sea.

scholarly journals Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos

2015 ◽  
Vol 12 (4) ◽  
pp. 1073-1089 ◽  
Author(s):  
E. Gourdin ◽  
S. Huon ◽  
O. Evrard ◽  
O. Ribolzi ◽  
T. Bariac ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Particulate Organic Matter ◽  
Rainy Season ◽  
Overland Flow ◽  
Specific Yield ◽  
Main Stream ◽  
Δ13c And Δ15n ◽  
Suspended Organic Matter

Abstract. The yields of the tropical rivers of Southeast Asia supply large quantities of carbon to the ocean. The origin and dynamics of particulate organic matter were studied in the Houay Xon River catchment located in northern Laos during the first erosive flood of the rainy season in May 2012. This cultivated catchment is equipped with three successive gauging stations draining areas ranging between 0.2 and 11.6 km2 on the main stem of the permanent stream, and two additional stations draining 0.6 ha hillslopes. In addition, the sequential monitoring of rainwater, overland flow and suspended organic matter compositions was conducted at the 1 m2 plot scale during a storm. The composition of particulate organic matter (total organic carbon and total nitrogen concentrations, δ13C and δ15N) was determined for suspended sediment, soil surface (top 2 cm) and soil subsurface (gullies and riverbanks) samples collected in the catchment (n = 57, 65 and 11, respectively). Hydrograph separation of event water was achieved using water electric conductivity and δ18O measurements for rainfall, overland flow and river water base flow (n = 9, 30 and 57, respectively). The composition of particulate organic matter indicates that upstream suspended sediments mainly originated from cultivated soils labelled by their C3 vegetation cover (upland rice, fallow vegetation and teak plantations). In contrast, channel banks characterized by C4 vegetation (Napier grass) supplied significant quantities of sediment to the river during the flood rising stage at the upstream station as well as in downstream river sections. The highest runoff coefficient (11.7%), sediment specific yield (433 kg ha−1), total organic carbon specific yield (8.3 kg C ha−1) and overland flow contribution (78–100%) were found downstream of reforested areas planted with teaks. Swamps located along the main stream acted as sediment filters and controlled the composition of suspended organic matter. Total organic carbon specific yields were particularly high because they occurred during the first erosive storm of the rainy season, just after the period of slash-and-burn operations in the catchment.

Carbon Isotope Ratios of Particulate Organic Matter in the Gulf of St. Lawrence

1979 ◽  
Vol 36 (6) ◽  
pp. 678-682 ◽  
Author(s):  
F. C. Tan ◽  
P. M. Strain
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Organic Carbon ◽  
Carbon Isotope ◽  
Particulate Organic Matter ◽  
Surface Sediments ◽  
Isotope Ratios ◽  
Lawrence Estuary ◽  
Carbon Isotope Ratios ◽  
Surface Samples

Sixteen offshore surface samples within the Gulf of St. Lawrence show low δ13C values and are similar to eight offshore surface samples collected seaward of the Gulf of St. Lawrence. The δ13C surface values are consistent with δ13C values in plankton produced at the temperature found in the euphotic zone in the study area. Higher values are observed in four surface samples from the mouth of the St. Lawrence Estuary and probably result from high carbon demand during periods of high biological productivity. Lower values found in seven deep POC samples indicate changes in the nature of the POC caused by biological degradation of the organic matter. Significant differences (2–6‰) between the uniformly high δ13C values of the organic carbon in surface sediments and the low values of near-bottom water POC have been observed. The similarity between the δ13C values of surface water POC and the surface sediments suggest that surface water POC is an important source of organic carbon in surface sediments. Several observations of large vertical δ13C gradients in deep water POC suggest the presence of resuspended sediments 30–60 m above the sediment–water interface. Key words: particulate organic matter, carbon isotope ratios, isotope fractionation, sediment resuspension, sediment sources, Gulf of St. Lawrence

In Situ Observations of the Occlusion of a Clay-Sugar Compound within Calcite

2022 ◽  
Author(s):  
Jialin Chi ◽  
Chonghao Jia ◽  
Wenjun Zhang ◽  
Christine V Putnis ◽  
Lijun Wang
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Global Climate Change ◽  
Global Climate ◽  
Ecological Systems ◽  
In Situ Observations ◽  
The Stability

The stability of soil organic matter (SOM) plays a key role in controlling global climate change as soil stores a large amount of organic carbon, compared with other ecological systems....

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