溶解性有机碳（DOC）的输移过程是流域碳循环中重要的组成部分，对全球碳循环产生重要影响。以大兴安岭多年冻土区的典型森林小流域—老爷岭流域为研究对象，获得2021年4月9日到6月30日冻融期降雨量、气温、土温等气象数据及逐日径流量、径流DOC浓度，计算了冻融循环期（4月9日—28日）和融化期（4月29日—6月30日）流域径流DOC的输出通量，揭示了径流DOC浓度及输出通量的影响因素。结果表明：（1）研究时段内，老爷岭流域径流DOC浓度变化范围为3.88—33.75 mg/L,流域上游的径流DOC浓度变化趋势与下游基本一致，DOC浓度随着温度的升高呈现下降趋势，4月份平均径流DOC浓度明显高于5、6月份。（2）研究时段内流域径流DOC总输出通量为3215.48 kg/km2,其中5月径流DOC输出通量高于4、6月份。径流量与径流DOC输出通量存在显著正相关关系（P<0.05）,是流域DOC输出通量的主导因素。（3）研究时段内流域DOC浓度与平均气温呈极显著负相关（R2=0.5048,P<0.001）;降水样品中的DOC浓度变化范围为1...

土壤温度和含水量是影响可溶性有机碳（DOC）变化的重要因素。然而，多年冻土泥炭地土壤DOC变化对秋季冻结期土壤水热变化的响应尚不明确。本研究选取大兴安岭3种多年冻土泥炭地[小叶章泥炭地（CP）、兴安落叶松-泥炭藓泥炭地（LP）、白毛羊胡子苔草泥炭地（EP）]作为研究对象，开展野外原位试验探究秋季冻结期土壤水热变化对多年冻土泥炭地土壤DOC变化的影响。结果表明：秋季冻结期土壤DOC含量表现为EP>CP>LP，平均含量分别为83.99、45.75和43.13mg·L-1。在秋季冻结前期3种类型多年冻土泥炭地土壤DOC含量均呈波动下降趋势，中、后期CP,LP土壤DOC变化较平缓。在秋季冻结前期，CP整体土壤DOC含量随浅层土壤温度的降低而减少；在后期CP浅层和整体土壤DOC含量随浅层土壤含水量的增加而增加。在秋季冻结中期，LP浅层土壤温度升高和含水量的减少，降低了土壤DOC含量；LP整体土壤DOC的变化随着浅层温度的升高逐渐降低。在秋季冻结后期，EP深层和整体土壤DOC含量随深层含水量增加而增加。在整个秋季冻结期，LP浅层土壤DOC主要受地表温度驱动，深层土...

The carbon release and transport in rivers are expected to increase in a warming climate with enhanced melting. We present a continuous dataset of DOC in the river, precipitation, and groundwater, including air temperature, discharge, and precipitation in the source region of the Yangtze River (SRYR). Our study shows that the average concentrations of DOC in the three end-members are characterized as the sequence of groundwater > precipitation > river, which is related to the water volume, cycle period, and river flow speed. The seasonality of DOC in the river is observed as the obvious bimodal structure at Tuotuohe (TTH) and Zhimenda (ZMD) gauging stations. The highest concentration appears in July (2.4 mg L-1 at TTH and 2.1 mg L-1 at ZMD) and the secondary high value (2.2 mg L-1 at TTH 1.9 mg L-1 at ZMD) emerges from August to September. It is estimated that 459 and 6751 tons of DOC are transported by the river at TTH and ZMD, respectively. Although the wet deposition flux of DOC is nearly ten times higher than the river flux, riverine DOC still primarily originates from soil erosion of the basin rather than precipitation settlement. Riverine DOC fluxes are positively correlated with discharge, suggesting DOC fluxes are likely to increase in the future. Our findings highlight that permafrost degradation and glacier retreat have a great effect on DOC concentration in rivers and may become increasingly important for regional biogeochemical cycles.

The Qinghai-Tibet Plateau (QTP) is experiencing severe permafrost degradation, which can affect the hydrological and biogeochemical processes. Yet how the permafrost change affects riverine carbon export remains uncertain. Here, we investigated the seasonal variations of dissolved inorganic and organic carbon (DIC and DOC) during flow seasons in a watershed located in the central QTP permafrost region. The results showed that riverine DIC concentrations (27.81 +/- 9.75 mg L-1) were much higher than DOC concentrations (6.57 +/- 2.24 mg L-1). DIC and DOC fluxes were 3.95 and 0.94 g C m(-2) year(-1), respectively. DIC concentrations increased from initial thaw (May) to freeze period (October), while DOC concentrations remained relatively steady. Daily dissolved carbon concentrations were more closely correlated with baseflow than that with total runoff. Spatially, average DIC and DOC concentrations were positively correlated with vegetation coverage but negatively correlated with bare land coverage. DIC concentrations increased with the thawed and frozen depths due to increased soil interflow, more thaw-released carbon, more groundwater contribution, and possibly more carbonate weathering by soil CO2 formed carbonic acid. The DIC and DOC fluxes increased with thawed depth and decreased with frozen layer thickness. The seasonality of riverine dissolved carbon export was highly dependent on active layer thawing and freezing processes, which highlights the importance of changing permafrost for riverine carbon export. Future warming in the QTP permafrost region may alter the quantity and mechanisms of riverine carbon export.

Dissolved organic carbon (DOC) in snow plays an important role in river ecosystems that are fed by snowmelt water. However, limited knowledge is available on the DOC content in snow of the Chinese Altai Mountains in Central Asia. In this study, DOC in the snow cover of the Kayiertesi river basin, southern slope of Altai Mountains, was investigated during November 2016 to April 2017. The results showed that average concentrations of DOC in the surface snowcover (1.01 +/- 0.52 mgL(-1)) were only a little higher than those in glaciers of the Tibetan Plateau, European Alps, and Alaska, but much higher than in Greenland Ice Sheet. Depth variations of DOC concentrations from snowpack profiles indicated higher values in the surface layer. During the observation period, scavenging efficiency for DOC in snow cover is estimated to be 0.15 +/- 0.10, suggesting that DOC in snow can be affected more by the meltwater during ablation season than during accumulation season. The average mass absorption cross at 365 nm and the absorption Angstrom exponent of DOC were 0.45 +/- 0.35 m(2) g(-1) and 2.59 +/- 1.03, respectively, with higher values in March and April 2017. Fraction of radiative forcing caused by DOC relative to black carbon accounted for about 10.5%, implying DOC is a non-ignorable light-absorber of solar radiation in snow of the Altai regions. Backward trajectories analysis and aerosol vertical distribution images from satellites showed that DOC in the snow of the Altai Mountains was mainly influenced by air masses from Central Asia, Western Siberia, the Middle East, and some even from Europe. Biomass burning and organic carbon mixed with mineral dust contributed significantly to the DOC concentration. This study highlights the effects of DOC in the snow cover for radiative forcing and the need to study carbon cycling for evaluation of quality of the down-streams ecosystems. (c) 2018 Elsevier B.V. All rights reserved.

Geomorphic disturbances to surrounding terrain induced by thermal degradation of permafrost often lead to surface ponding or soil saturation. However, interactions between soil moisture and temperature on belowground carbon processes are not fully understood. We conducted batch incubation for three temperature treatments [constant freezing (CF), constant thawing (CT), and fluctuating temperatures (FTC)] and two soil moisture conditions (ponded and unsaturated). Extracellular enzyme activity was higher under ponded conditions than under unsaturated conditions, resulting in higher dissolved organic carbon (DOC) levels for ponded conditions. More CO2 and less CH4 were emitted under unsaturated conditions than under ponded conditions. Carbon dioxide emission was similar for CT and FTC treatments regardless of moisture conditions. However, CH4 emission was higher under ponded conditions than under unsaturated conditions for CT treatments, but was very low for FTC treatments regardless of moisture conditions. Little CO2 and CH4 were produced in CF treatments. Despite similar CO2 and CH4 emission levels for CT and FTC treatments, lower DOC levels were observed in the latter, indicating slower soil organic carbon (SOC) decomposition. Similar DOC variation patterns between CT and CF treatments indicated that SOC decomposition was considerable and further degradation to CO2 or CH4 was negligible even for CF treatments. The SOC decomposition and CO2 and CH4 emissions were considerable for FTC treatments. Our results suggest that labile-C produced during SOC decomposition in seasonally frozen soils and permafrost may provide supplemental substrates that would enhance the positive feedback to climate change with rising temperatures and wetter conditions.

选取青藏高原多年冻土区12条河流样品进行分析,结合流域内植被类型、流量大小、多年冻土面积与河流溶解性有机碳(DOC)的质量浓度、化学组成、生物可利用性之间的关系及分解动力学进行讨论.结果表明,分别在高寒草甸(AM)、高寒沼泽草甸-高寒草甸(ASM-AM)、高寒草甸-高寒草原(AM-AS)、高寒草甸-高寒草原-裸地(AM-AS-BL)为主的流域内,河流DOC的质量浓度依次为(5.17±0.21)、(5.02±0.50)、(3.55±0.25)和(2.79±0.41)mg·L-1,DOC的生物可降解性程度(BDOC)依次为(23.54±2.62)%、(23.66±3.31)%、(18.17±5.26)%和(11.72±15.56)%;相应地,流域内植被覆盖度越小,河流DOC的芳香性程度越大,DOC的可生物降解性和降解速率随着降低,并且BDOC在培养的过程中的反应遵循一级反应动力学原理;此外,连续多年冻土区河流的BDOC大于非连续多年冻土区的河流BDOC,大河的BDOC小于源头小河的BDOC.研究表明,流域内植被类型是影响多年冻土区河流BDOC的主要影响因素,同时,流量大小和多年冻土对BDO...

A large reservoir of organic carbon is stored in the permafrost region. Therefore, understanding the export of dissolved organic carbon (DOC) from rivers in the permafrost zone is important in the context of climate change. This study investigated the dynamics of DOC export from the wetlands of the Kandu River catchment located in a cold temperate region in northeast China during the growing seasons of 2011 and 2012. Our findings indicated that subsurface flow was the primary runoff pathway that transports DOC from wetland soil to stream discharge. The organic-mineral soil structure resulted in substantial differences in water sources, as well as in DOC resources, between the flood and base flow volume during the growing seasons. The active layer depth is key, as it affects runoff generation and the DOC concentration and chemical characteristics of stream discharge. The DOC flux from our study area was estimated to be up to 1039.66 t during the growing season, which represents more than one third of the net ecosystem exchange (NEE) in wetlands. Given the expected increase in air temperature and precipitation, our results indicate that there will be an increase in the total DOC flux for the study region in the future as a result of increased DOC concentration. (C) 2015 Elsevier B.V. All rights reserved.

Over the next century, near-surface permafrost across the circumpolar Arctic is expected to degrade significantly. particularly for land areas south of 70 degrees N. This is likely to cause widespread impacts on arctic hydrology, ecology, and trace gas emissions. Here. we present a review of recent Studies investigating linkages between permafrost dynamics and river biogeochemistry in the Arctic, including consideration of likely impacts that warming-induced changes in permafrost may be having (or will have in the future) oil the delivery of organic matter, inorganic nutrients, and major ions to the Arctic Ocean. These interacting processes can be highly complex and undoubtedly exhibit spatial and temporal variabilities associated with current permafrost conditions, sensitivity to permafrost thaw, mode of permafrost degradation (overall permafrost thaw, active layer deepening, and/or thermokarst processes), and environmental characteristics of watersheds (e.g. land cover, soil type, and topography). One of the most profound consequences of permafrost thaw projected for the future is that the arctic terrestrial freshwater system is likely to experience a transition from a Surface water-dominated system to a groundwater-dominated system. Along with many other cascading impacts from this transition, mineral-rich groundwater may become an important contributor to streamflow, in addition to the currently dominant contribution from mineral-poor surface water. Most Studies observe or predict an increase in major ion, phosphate, and silicate export with this shift towards greater groundwater contributions. However, we see conflicting accounts of whether the delivery of inorganic nitrogen and organic matter will increase or decrease with warming and permafrost thaw. It is important to note that uncertainties in the predictions of the total flux of biogeochemical constituents are tightly linked to future uncertainties in discharge of rivers. Nonetheless, it is clear that over the next Century there will be important shifts in the river transport of organic matter, inorganic nutrients, and major ions. which may in turn have critical implications for primary production and carbon cycling oil arctic shelves and in the Arctic Ocean basin interior. Copyright (C) 2008 John Wiley & Sons, Ltd.