scholarly journals Sea salt aerosols as a reactive surface for inorganic and organic acidic gases in the Arctic troposphere

2015 ◽  
Vol 15 (19) ◽  
pp. 11341-11353 ◽  
Author(s):  
J. W. Chi ◽  
W. J. Li ◽  
D. Z. Zhang ◽  
J. C. Zhang ◽  
Y. T. Lin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Optical Properties ◽  
Sea Salt ◽  
The Arctic ◽  
Amorphous Coating ◽  
Acidic Gases ◽  
Sea Salt Aerosols ◽  
New Findings ◽  
Arctic Atmosphere ◽  
Inorganic And Organic

Abstract. Sea salt aerosols (SSA) are dominant particles in the Arctic atmosphere and determine the polar radiative balance. SSA react with acidic pollutants that lead to changes in physical and chemical properties of their surface, which in turn alter their hygroscopic and optical properties. Transmission electron microscopy with energy-dispersive X-ray spectrometry was used to analyze morphology, composition, size, and mixing state of individual SSA at Ny-Ålesund, Svalbard, in summertime. Individual fresh SSA contained cubic NaCl coated by certain amounts of MgCl2 and CaSO4. Individual partially aged SSA contained irregular NaCl coated by a mixture of NaNO3, Na2SO4, Mg(NO3)2, and MgSO4. The comparison suggests the hydrophilic MgCl2 coating in fresh SSA likely intrigued the heterogeneous reactions at the beginning of SSA and acidic gases. Individual fully aged SSA normally had Na2SO4 cores and an amorphous coating of NaNO3. Elemental mappings of individual SSA particles revealed that as the particles ageing Cl gradually decreased, the C, N, O, and S content increased. 12C- mapping from nanoscale secondary ion mass spectrometry indicates that organic matter increased in the aged SSA compared with the fresh SSA. 12C- line scan further shows that organic matter was mainly concentrated on the aged SSA surface. These new findings indicate that this mixture of organic matter and NaNO3 on particle surfaces likely determines their hygroscopic and optical properties. These abundant SSA as reactive surfaces adsorbing inorganic and organic acidic gases can shorten acidic gas lifetime and influence the possible gaseous reactions in the Arctic atmosphere, which need to be incorporated into atmospheric chemical models in the Arctic troposphere.

scholarly journals Sea salt aerosols as a reactive surface for inorganic and organic acidic gases in the arctic troposphere

2015 ◽  
Vol 15 (12) ◽  
pp. 16715-16745 ◽  
Author(s):  
J. W. Chi ◽  
W. J. Li ◽  
D. Z. Zhang ◽  
J. C. Zhang ◽  
Y. T. Lin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Optical Properties ◽  
Sea Salt ◽  
Heterogeneous Reactions ◽  
The Arctic ◽  
Amorphous Coating ◽  
Acidic Gases ◽  
Sea Salt Aerosols ◽  
New Findings ◽  
Inorganic And Organic

Abstract. Sea salt aerosols (SSA) are dominant particles in the arctic atmosphere and determine the polar radiative balance. SSA react with acidic pollutants that lead to changes of physical and chemical properties of their surface, which in turn alter their hygroscopic and optical properties. Transmission electron microscopy with energy-dispersive X-ray spectrometry was used to analyze morphology, composition, size, and mixing state of individual SSA at Ny-Ålesund, Svalbard in summertime. Individual fresh SSA contained cubic NaCl coated by certain amounts of MgCl2 and CaSO4. Individual partially aged SSA contained irregular NaCl coated by a mixture of NaNO3, Na2SO4, Mg(NO3)2, and MgSO4. The comparison suggests the hydrophilic MgCl2 coating in fresh SSA likely intrigued the heterogeneous reactions at the beginning of SSA and acidic gases. Individual fully aged SSA normally had Na2SO4 cores and an amorphous coating of NaNO3. Elemental mappings of individual SSA particles revealed that as the particles ageing Cl gradually decreased but the C, N, O, and S content increased. 12C14N− mapping from nanoscale secondary ion mass spectrometry indicates that organic matter increased in the aged SSA compared with the fresh SSA. 12C14N− line scans further show that organic matter was mainly concentrated on the aged SSA surface. These new findings indicate that this mixture of organic matter and NaNO3 on particle surfaces determines their hygroscopic and optical properties. These abundant SSA, whose reactive surfaces absorb inorganic and organic acidic gases in the arctic troposphere, need to be incorporated into atmospheric chemical models.

scholarly journals Aerosol distribution around Svalbard during intense easterly winds

2010 ◽  
Vol 10 (4) ◽  
pp. 1473-1490 ◽  
Author(s):  
A. Dörnbrack ◽  
I. S. Stachlewska ◽  
C. Ritter ◽  
R. Neuber
Keyword(s):  
Sea Salt ◽  
Airborne Lidar ◽  
The Arctic ◽  
Aerosol Layer ◽  
Atmospheric Conditions ◽  
Sea Salt Aerosols ◽  
Aerosol Distribution ◽  
Weather Situation ◽  
Low Level Jet ◽  
Aerosol Plume

Abstract. This paper reports on backscatter and depolarization measurements by an airborne lidar in the Arctic during the ASTAR 2004 campaign. A unique weather situation facilitated the observation of the aerosol concentration under strongly forced atmospheric conditions. The vigorous easterly winds distorted the flow past Svalbard in such a way that mesoscale features were visible in the remote-sensing observations: The formation of a well-mixed aerosol layer inside the Adventdalen and the subsequent thinning of the aerosol plume were observed over the Isfjorden. Additionally, mobilization of sea salt aerosols due to a coastal low-level jet at the northern tip of Svalbard resulted in a sloped boundary layer toward north. Mesoscale numerical modelling was applied to identify the sources of the aerosol particles and to explain the observed patterns.

scholarly journals Biogenic, anthropogenic and sea salt sulfate size-segregated aerosols in the Arctic summer

2016 ◽  
Vol 16 (8) ◽  
pp. 5191-5202 ◽  
Author(s):  
Roghayeh Ghahremaninezhad ◽  
Ann-Lise Norman ◽  
Jonathan P. D. Abbatt ◽  
Maurice Levasseur ◽  
Jennie L. Thomas
Keyword(s):  
Fine Particles ◽  
Coast Guard ◽  
Sea Salt ◽  
The Arctic ◽  
Sulfate Concentration ◽  
Local Pollution ◽  
Fine Aerosol ◽  
Two Samples ◽  
Range Transport ◽  
Arctic Atmosphere

Abstract. Size-segregated aerosol sulfate concentrations were measured on board the Canadian Coast Guard Ship (CCGS) Amundsen in the Arctic during July 2014. The objective of this study was to utilize the isotopic composition of sulfate to address the contribution of anthropogenic and biogenic sources of aerosols to the growth of the different aerosol size fractions in the Arctic atmosphere. Non-sea-salt sulfate is divided into biogenic and anthropogenic sulfate using stable isotope apportionment techniques. A considerable amount of the average sulfate concentration in the fine aerosols with a diameter  <  0.49 µm was from biogenic sources (>  63 %), which is higher than in previous Arctic studies measuring above the ocean during fall (<  15 %) (Rempillo et al., 2011) and total aerosol sulfate at higher latitudes at Alert in summer (>  30 %) (Norman et al., 1999). The anthropogenic sulfate concentration was less than that of biogenic sulfate, with potential sources being long-range transport and, more locally, the Amundsen's emissions. Despite attempts to minimize the influence of ship stack emissions, evidence from larger-sized particles demonstrates a contribution from local pollution. A comparison of δ34S values for SO2 and fine aerosols was used to show that gas-to-particle conversion likely occurred during most sampling periods. δ34S values for SO2 and fine aerosols were similar, suggesting the same source for SO2 and aerosol sulfate, except for two samples with a relatively high anthropogenic fraction in particles  <  0.49 µm in diameter (15–17 and 17–19 July). The high biogenic fraction of sulfate fine aerosol and similar isotope ratio values of these particles and SO2 emphasize the role of marine organisms (e.g., phytoplankton, algae, bacteria) in the formation of fine particles above the Arctic Ocean during the productive summer months.

scholarly journals Vertical profiles of light absorption and scattering associated with black-carbon particle fractions in the springtime Arctic above 79° N

2019 ◽  
Author(s):  
W. Richard Leaitch ◽  
John K. Kodros ◽  
Megan D. Willis ◽  
Sarah Hanna ◽  
Hannes Schulz ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Black Carbon ◽  
Light Absorption ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
The Arctic ◽  
Vertical Profiles ◽  
Near Surface ◽  
Arctic Atmosphere

Abstract. Despite the potential importance of black carbon (BC) to radiative forcing of the Arctic atmosphere, vertically-resolved measurements of the particle light scattering coefficient (Bsp) and light absorption coefficient (Bap) in the springtime Arctic atmosphere are infrequent, especially measurements at latitudes at or above 80oN. Here, relationships among vertically-distributed aerosol optical properties Bap, Bsp, and single scattering albedo or SSA), particle microphysics and particle chemistry are examined for a region of the Canadian archipelago between 79.9oN and 83.4oN from near the surface to 500 hPa. Airborne data collected during April, 2015, are combined with ground-based observations from the observatory at Alert, Nunavut and simulations from the GEOS-Chem-TOMAS model (Kodros et al., 2018) to increase our knowledge of the effects of BC on light absorption in the Arctic troposphere. The results are constrained for Bsp less than 15 Mm-1, which represent 98% of the observed Bsp, because the single scattering albedo (SSA) has a tendency to be lower at lower Bsp, resulting in a larger relative contribution to Arctic warming. At 18.4 m2 g-1, the average BC mass absorption coefficient (MAC) from the combined airborne and Alert observations is substantially higher than the two averaged modelled MAC values (9.5 m2 g-1 and 7.0 m2 g-1) for two different internal mixing assumptions, the latter of which is based on previous observations. The higher observed MAC value may be explained by an underestimation of BC and possible differences in BC microphysics and morphologies between the observations and model. We present Bap and SSA based on the assumption that Bap is overestimated in the observations in addition to the assumption that the higher MAC is explained. Median values of the measured Bap, rBC and organic component of particles all increase by a factor of 1.8±0.1 going from near-surface to 750 hPa, and values higher than the surface persist to 600 hPa. Modelled BC, organics, and Bap agree with the near-surface measurements, but do not reproduce the higher values observed between 900 hPa and 600 hPa. The differences between modelled and observed optical properties follow the same trend as the differences between the modelled and observed concentrations of the carbonaceous components (black and organic). Some discrepancies in the model may be due to the use of a relatively low imaginary refractive index of BC as well as by the ejection of biomass burning particles only into the boundary layer at sources. For the assumption of the higher observed MAC value, the SSA range between 0.88 and 0.94, which is significantly lower than other recent estimates for the Arctic, in part reflecting the constraint of Bsp <15 Mm-1. The large uncertainties in measuring optical properties and BC as well as the large differences between measured and modelled values, here and in the literature, argue for improved measurements of BC and light absorption by BC as well as more vertical profiles of aerosol chemistry, microphysics, and other optical properties in the Arctic.

scholarly journals Toward a minimal representation of aerosols in climate models: description and evaluation in the Community Atmosphere Model CAM5

2012 ◽  
Vol 5 (3) ◽  
pp. 709-739 ◽  
Author(s):  
X. Liu ◽  
R. C. Easter ◽  
S. J. Ghan ◽  
R. Zaveri ◽  
P. Rasch ◽  
...  
Keyword(s):  
Developing Countries ◽  
Optical Properties ◽  
Size Distribution ◽  
Sea Salt ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Model Version ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Aerosol Module

Abstract. A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically-based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. In this paper a description and evaluation of the aerosol module and its two representations are provided. Sensitivity of the aerosol lifecycle to simplifications in the representation of aerosol is discussed. Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7. Differences in primary organic matter (POM) and black carbon (BC) concentrations between MAM3 and MAM7 are also small (mostly within 10%). The mineral dust global burden differs by 10% and sea salt burden by 30–40% between MAM3 and MAM7, mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical and temporal variations of aerosol mass and number concentrations, size distributions, and aerosol optical properties. However, there are noticeable biases; e.g., simulated BC concentrations are significantly lower than measurements in the Arctic. There is a low bias in modeled aerosol optical depth on the global scale, especially in the developing countries. These biases in aerosol simulations clearly indicate the need for improvements of aerosol processes (e.g., emission fluxes of anthropogenic aerosols and precursor gases in developing countries, boundary layer nucleation) and properties (e.g., primary aerosol emission size, POM hygroscopicity). In addition, the critical role of cloud properties (e.g., liquid water content, cloud fraction) responsible for the wet scavenging of aerosol is highlighted.

scholarly journals Biogenic, anthropogenic, and sea salt sulfate size-segregated aerosols in the Arctic summer

2016 ◽  
Author(s):  
Roghayeh Ghahremaninezhad ◽  
Ann-Lise Norman ◽  
Jonathan P. D. Abbatt ◽  
Maurice Levasseur ◽  
Jennie L. Thomas
Keyword(s):  
Fine Particles ◽  
Coast Guard ◽  
Sea Salt ◽  
The Arctic ◽  
Sulfate Concentration ◽  
Local Pollution ◽  
Fine Aerosol ◽  
Two Samples ◽  
Range Transport ◽  
Arctic Atmosphere

Abstract. Size-segregated aerosol sulfate concentrations were measured on board the Canadian Coast Guard Ship (CCGS) Amundsen in the Arctic during July 2014. The objective of this study was to utilize the isotopic composition of sulfate to address the contribution of anthropogenic and biogenic sources of aerosols to the growth of the different aerosol size fractions in the Arctic atmosphere. Non-sea salt sulfate is divided into biogenic and anthropogenic sulfate using stable isotope apportionment techniques. A considerable amount of the average sulfate concentration in the fine aerosols with diameter < 0.49 μm was from biogenic sources (> 70 %) which is higher than previous Arctic studies measuring above the ocean during fall (< 15 %) (Rempillo et al., 2011) and total aerosol sulfate at higher latitudes at Alert in summer (> 30 %) (Norman et al., 1999). The anthropogenic sulfate concentration was less than biogenic sulfate, with potential sources being long range transport and, more locally, the Amundsen’s emissions. Despite attempts to minimize the influence of ship stack emissions, evidence from larger-sized particles demonstrates a contribution from local pollution. A comparison of δ34S values for SO2 and fine aerosols was used to show that gas-to-particle conversion likely occurred during most sampling periods. δ34S values for SO2 and fine aerosols were similar suggesting the same source for SO2 and aerosol sulfate, except for two samples with a relatively high anthropogenic fraction in particles < 0.49 μm in diameter (July 15–17 and 17–19). The high biogenic fraction of sulfate fine aerosol and similar isotope ratio values of these particles and SO2 emphasize the role of marine organisims (e.g. phytoplankton, algea, bacteria) in the formation of fine particles above the Arctic Ocean during the productive summer months.

scholarly journals Vertical profiles of light absorption and scattering associated with black carbon particle fractions in the springtime Arctic above 79° N

2020 ◽  
Vol 20 (17) ◽  
pp. 10545-10563 ◽  
Author(s):  
W. Richard Leaitch ◽  
John K. Kodros ◽  
Megan D. Willis ◽  
Sarah Hanna ◽  
Hannes Schulz ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Black Carbon ◽  
Light Absorption ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
The Arctic ◽  
Vertical Profiles ◽  
Near Surface ◽  
Arctic Atmosphere

Abstract. Despite the potential importance of black carbon (BC) for radiative forcing of the Arctic atmosphere, vertically resolved measurements of the particle light scattering coefficient (σsp) and light absorption coefficient (σap) in the springtime Arctic atmosphere are infrequent, especially measurements at latitudes at or above 80∘ N. Here, relationships among vertically distributed aerosol optical properties (σap, σsp and single scattering albedo or SSA), particle microphysics and particle chemistry are examined for a region of the Canadian archipelago between 79.9 and 83.4∘ N from near the surface to 500 hPa. Airborne data collected during April 2015 are combined with ground-based observations from the observatory at Alert, Nunavut and simulations from the Goddard Earth Observing System (GEOS) model, GEOS-Chem, coupled with the TwO-Moment Aerosol Sectional (TOMAS) model (collectively GEOS-Chem–TOMAS; Kodros et al., 2018) to further our knowledge of the effects of BC on light absorption in the Arctic troposphere. The results are constrained for σsp less than 15 Mm−1, which represent 98 % of the observed σsp, because the single scattering albedo (SSA) has a tendency to be lower at lower σsp, resulting in a larger relative contribution to Arctic warming. At 18.4 m2 g−1, the average BC mass absorption coefficient (MAC) from the combined airborne and Alert observations is substantially higher than the two averaged modelled MAC values (13.6 and 9.1 m2 g−1) for two different internal mixing assumptions, the latter of which is based on previous observations. The higher observed MAC value may be explained by an underestimation of BC, the presence of small amounts of dust and/or possible differences in BC microphysics and morphologies between the observations and model. In comparing the observations and simulations, we present σap and SSA, as measured, and σap∕2 and the corresponding SSA to encompass the lower modelled MAC that is more consistent with accepted MAC values. Median values of the measured σap, rBC and the organic component of particles all increase by a factor of 1.8±0.1, going from near-surface to 750 hPa, and values higher than the surface persist to 600 hPa. Modelled BC, organics and σap agree with the near-surface measurements but do not reproduce the higher values observed between 900 and 600 hPa. The differences between modelled and observed optical properties follow the same trend as the differences between the modelled and observed concentrations of the carbonaceous components (black and organic). Model-observation discrepancies may be mostly due to the modelled ejection of biomass burning particles only into the boundary layer at the sources. For the assumption of the observed MAC value, the SSA range between 0.88 and 0.94, which is significantly lower than other recent estimates for the Arctic, in part reflecting the constraint of σsp<15 Mm−1. The large uncertainties in measuring optical properties and BC, and the large differences between measured and modelled values here and in the literature, argue for improved measurements of BC and light absorption by BC and more vertical profiles of aerosol chemistry, microphysics and other optical properties in the Arctic.

scholarly journals Validation of CAMS AOD using AERONET Data and Trend Analysis at Four Locations in the Indo-Gangetic Basin

2020 ◽  
Author(s):  
Amit Misra ◽  
Sachchida Tripathi ◽  
Harjinder Sembhi ◽  
Hartmut Boesch
Keyword(s):  
Organic Matter ◽  
Trend Analysis ◽  
Black Carbon ◽  
Fine Particles ◽  
Source Area ◽  
Sea Salt ◽  
Agricultural Activity ◽  
Industrial Sites ◽  
Sea Salt Aerosols ◽  
Monitoring Service

Abstract. In this work we have validated Copernicus Aerosol Monitoring Service (CAMS) derived aerosol optical depth (AOD) at four locations (Kanpur, Gandhi College, Jaipur and Lahore) in the Indo-Gangetic Basin and used it to study the aerosol climatology and trend in AOD at these locations. Lahore and Kanpur are urban and industrial sites with agricultural activity in the neighbouring regions. Gandhi College is in a rural agricultural area, whereas Jaipur is a desert dust source area. Aerosol climatology at the four sites are examined with MODIS-derived NDVI and ESA-CCI derived soil moisture data. CAMS-derived AOD for black carbon, sulphate, dust, sea salt and organic matter at the four sites are studied and discussed. It is observed that sulphate AOD has the largest influence on the total aerosol climatology. Contribution from dust and sea salt aerosols is observed only during pre-monsoon and monsoon seasons, whereas non-zero AOD is observed for organic matter, black carbon and sulphate aerosols throughout the year at all sites. Comparison of CAMS AOD with AERONET AOD shows better correlation when aerosol climatology is dominated by coarse particles as compared to when it is dominated by fine particles (e.g., at Kanpur, R2pre-monsoon = 0.63 and R2winter = 0.36). Trend analysis shows largest increase in organic matter (e.g., 0.305 &amp;pm; 0.021 per year at Kanpur) and least in sea salt aerosols (e.g., 0.008 &amp;pm; 0.001 per year at Kanpur).

scholarly journals Toward a minimal representation of aerosol direct and indirect effects: model description and evaluation

2011 ◽  
Vol 4 (4) ◽  
pp. 3485-3598 ◽  
Author(s):  
X. Liu ◽  
R. C. Easter ◽  
S. J. Ghan ◽  
R. Zaveri ◽  
P. Rasch ◽  
...  
Keyword(s):  
Developing Countries ◽  
Optical Properties ◽  
Size Distribution ◽  
Mineral Dust ◽  
Sea Salt ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Model Description ◽  
Accumulation Mode ◽  
Model Version

Abstract. A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. Major approximations in MAM3 include assuming immediate mixing of primary organic matter (POM) and black carbon (BC) with other aerosol components, merging of the MAM7 fine dust and fine sea salt modes into the accumulation mode, merging of the MAM7 coarse dust and coarse sea salt modes into the single coarse mode, and neglecting the explicit treatment of ammonia and ammonium cycles. Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7 as most (~90%) of these aerosol species are in the accumulation mode. Differences of POM and BC concentrations between MAM3 and MAM7 are also small (mostly within 10%) because of the assumed hygroscopic nature of POM, so that much of the freshly emitted POM and BC is wet-removed before mixing internally with soluble aerosol species. Sensitivity tests with the POM assumed to be hydrophobic and with slower aging increase the POM and BC concentrations, especially at high latitudes (by several times). The mineral dust global burden differs by 10% and sea salt burden by 30–40% between MAM3 and MAM7 mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical and temporal variations of aerosol mass and number concentrations, size distributions, and aerosol optical properties. However, there are noticeable biases, e.g., simulated sulfate and mineral dust concentrations at surface over the oceans are too low. Simulated BC concentrations are significantly lower than measurements in the Arctic. There is a low bias in modeled aerosol optical depth on the global scale, especially in the developing countries. There biases in aerosol simulations clearly indicate the need for improvements of aerosol processes (e.g., emission fluxes of anthropogenic aerosols and precursor gases in developing countries, boundary layer nucleation) and properties (e.g., primary aerosol emission size, POM hygroscopicity). In addition the critical role of cloud properties (e.g., liquid water content, cloud fraction) responsible for the wet scavenging of aerosol is highlighted.

scholarly journals Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River, Siberia

2015 ◽  
Vol 12 (15) ◽  
pp. 12321-12347 ◽  
Author(s):  
K. E. Frey ◽  
W. V. Sobczak ◽  
P. J. Mann ◽  
R. M. Holmes
Keyword(s):  
Organic Matter ◽  
Optical Properties ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
River Basin ◽  
Flow Path ◽  
The Arctic ◽  
Pore Waters ◽  
Water Types ◽  
Kolyma River

Abstract. The Kolyma River in Northeast Siberia is among the six largest arctic rivers and drains a region underlain by vast deposits of Holocene-aged peat and Pleistocene-aged loess known as yedoma, most of which is currently stored in ice-rich permafrost throughout the region. These peat and yedoma deposits are important sources of dissolved organic matter (DOM) to inland waters that in turn play a significant role in the transport and ultimate remineralization of organic carbon to CO2 and CH4 along the terrestrial flow-path continuum. The turnover and fate of terrigenous DOM during offshore transport will largely depend upon the composition and amount of carbon released to inland and coastal waters. Here, we measured the optical properties of chromophoric DOM (CDOM) from a geographically extensive collection of waters spanning soil pore waters, streams, rivers, and the Kolyma River mainstem throughout a ∼ 250 km transect of the northern Kolyma River basin. During the period of study, CDOM absorbance values were found to be robust proxies for the concentration of DOM, whereas additional CDOM parameters such as spectral slopes (S) were found to be useful indicators of DOM quality along the flow-path. In particular, CDOM absorption at 254 nm showed a strong relationship with dissolved organic carbon (DOC) concentrations across all water types (r2 = 0.958, p < 0.01). The spectral slope ratio (SR) of CDOM demonstrated statistically significant differences between all four water types and tracked changes in the concentration of bioavailable DOC, suggesting that this parameter may be suitable for clearly discriminating shifts in organic matter characteristics among water types along the full flow-path continuum across this landscape. The heterogeneity of environmental characteristics and extensive continuous permafrost of the Kolyma River basin combine to make this a critical region to investigate and monitor. With ongoing and future permafrost degradation, peat and yedoma deposits throughout the Northeast Siberian region will become more hydrologically active, providing greater amounts of DOM to fluvial networks and ultimately to the Arctic Ocean. The ability to rapidly and comprehensively monitor shifts in the quantity and quality of DOM across the landscape is therefore critical for understanding potential future feedbacks on the arctic carbon cycle.

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