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1.
Faxiang Tao 《中国地球化学学报》2017,36(4):658-666
The carbon cycle of global inland waters is quantitatively comparable to other components in the global carbon budget. Among inland waters, a significant part is man-made lakes formed by damming rivers. Man-made lakes are undergoing a rapid increase in number and size. Human impacts and frequent algae blooms lead to it necessary to make a better constraint on their carbon cycles. Here, we make a primary estimation on the air–water CO2 transfer flux through an algae bloom year for a subtropical man-made lake—Hongfeng Lake, Southwest China. To do this a new type of glass bottles was designed for content and isotopic analysis of DIC and other environmental parameters. At the early stage of algae bloom, CO2 was transferred from the atmosphere to the lake with a net flux of 1.770 g·C·m?2. Later, the partial pressure (pCO2) of the aqueous CO2 increased rapidly and the lake outgassed to the atmosphere with a net flux of 95.727 g·C·m?2. In the remaining days, the lake again took up CO2 from the atmosphere with a net flux of 14.804 g·C·m?2. As a whole, Lake Hongfeng released 4527 t C to the atmosphere, accounting for one-third of the atmosphere/soil CO2 sequestered by chemical weathering in the whole drainage. With an empirical mode decomposition method, we found air temperature plays a major role in controlling water temperature, aqueous pCO2 and hence CO2 flux. This work indicates a necessity to make detailed and comprehensive carbon budgets in man-made lakes. 相似文献
2.
《Applied Geochemistry》1993,8(3):207-221
The gases dissolved in Lake Nyos, Cameroon, were quantified recently (December 1989 and September 1990) by two independent techniques: in-situ measurements using a newly designed probe and laboratory analyses of samples collected in pre-evacuated stainless steel cylinders. The highest concentrations of CO2 and CH4 were 0.30 mol/kg and 1.7 mmol/kg, respectively, measured in cylinders collected 1 m above lake bottom. Probe measurements of in-situ gas pressure at three different stations showed that horizontal variations in total dissolved gas were negligible. Total dissolved-gas pressure near the lake bottom is 1.06 MPa (10.5 atm), 50% as high as the hydrostatic pressure of 2.1 MPa (21 atm). Comparing the CO2 profile constructed from the 1990 data to one obtained in May 1987 shows that CO2 concentrations have increased at depths to below 150 m. Based on these profiles, the average rate of CO2 input to bottom waters was 2.6 × 108 mol/a. Increased deep-water temperatures require an average heat flow of 0.32 MW into the hypolimnion over the same time period. The transport rates of CO2, heat, and major ions into the hypolimnion suggest that a low-temperature reservoir of free CO2 exists a short distance below lake bottom and that convective cycling of lake water through the sediments is involved in transporting the CO2 into the lake from the underlying diatreme. Increased CH4 concentrations at all depths below the oxycline and a high14C content (41% modern) in the CH4 4 m above lake bottom show that much of the CH4 is biologically produced within the lake. The CH4 production rate may vary with time, but if the CO2 recharge rate remains constant, CO2 saturation of the entire hypolimnion below 50 m depth would require ∼140a, given present-day concentrations. 相似文献
3.
The spatial and temporal variations of the flux of CO2 were determined during 2007 in the Recife estuarine system (RES), a tropical estuary that receives anthropogenic loads from one of the most populated and industrialized areas of the Brazilian coast. The RES acts as a source of nutrients (N and P) for coastal waters. The calculated CO2 fluxes indicate that the upstream inputs of CO2 from the rivers are largely responsible for the net annual CO2 emission to the atmosphere of +30 to +48 mmol m?2 day?1, depending on the CO2 exchange calculation used, which mainly occurs during the late austral winter and early summer. The observed inverse relationship between the CO2 flux and the net ecosystem production (NEP) indicates the high heterotrophy of the system (except for the months of November and December). The NEP varies between ?33 mmol m?2 day?1 in summer and ?246 mmol m?2 day?1 in winter. The pCO2 values were permanently high during the study period (average ~4,700 μatm) showing a gradient between the inner (12,900 μatm) and lower (389 μatm) sections on a path of approximately 30 km. This reflects a state of permanent pollution in the basin due to the upstream loading of untreated domestic effluents (N/P?=?1,367:6 μmol kg?1 and pH?=?6.9 in the inner section), resulting in the continuous mineralization of organic material by heterotrophic organisms and thereby increasing the dissolved CO2 in estuarine waters. 相似文献
4.
Carbon dioxide (CO2) emission from the river-type reservoir is an hotspot of carbon cycle within inland waters. However, related studies on the different types of reservoirs are still inadequate. Therefore, we sampled the Three Gorges Reservoir (TGR), a typical river-type reservoir having both river and lake characteristics, using an online system (HydroCTM/CO2) and YSI-6600v2 meter to determine the partial pressure of carbon dioxide (pCO2) and physical chemical parameters in 2013. The results showed that the CO2 flux from the mainstream ranged from 26.1 to 92.2 mg CO2/m2 h with average CO2 fluxes of 50.0 mg/m2 h. The CO2 fluxes from the tributary ranged from ?10.91 to 53.95 mg CO2/m2 h with area-weighted average CO2 fluxes of 11.4 mg/m2 h. The main stream emits CO2 to the atmosphere the whole year; however, the surface water of the tributary can sometimes act as a sink of CO2 for the atmosphere. As the operation of the TGR, the tributary became more favorable to photosynthetic uptake of CO2 especially in summer. The total CO2 flux was estimated to be 0.34 and 0.03 Tg CO2/year from the mainstream and the tributaries, respectively. Our emission rates are lower than previous estimates, but they are in agreement with the average CO2 flux from temperate reservoirs estimated by Barros et al. (Nat Geosci 4(9):593–596, 2011). 相似文献
5.
We made direct measurements of the partial pressure of CO2 (PCO 2) in the tidal-freshwater portion of the Hudson River Estuary over a 3.5-yr period. At all times the Hudson was supersaturated in CO2 with respect to the atmosphere. PCO 2 in surface water averaged 1125±403 (SD) μatm while the atmosphere averaged 416±68 μatm. Weekly samples at a single, mid-river station showed a pronounced and reproducible seasonal cycle with highest values (～2000 μatm) in mid-to-late summer, and lowest values (～500 μatm) generally in late winter. Samples taken along the length of the 190-km section of river showed a general decline in CO2 from north to south. This decline was most pronounced in summer and very slight in spring. Diel and vertical variation were small relative to the standing stock of CO2. Over six diel cycles, all taken during the algal growing season, the mean range was 300±114 μatm. CO2 tended to increase slightly with depth, but the gradient was small, about 0.5 μmol m?1, or an increase of 190 μatm from top to within 1 m of the bottom. For a large subset of the samples (n=452) we also calculated CO2 from measurements of pH and total DIC. Calculated and measured values of CO2 were in reasonably good agreement and a regression of calculated versus measured values had a slope of 0.85±0.04 and an r2 of 0.60. Combining our measurements with recent experimental studies of gas exchange in the Hudson, we estimate that the Hudson releases CO2 at a rate of 70–162 g C m?2 yr?1 from the river to the atmosphere. 相似文献
6.
Emission of gaseous carbon dioxide from salt-marsh sediments and its relation to other carbon losses
Rates of CO2 emission from bare salt-marsh sediments in areas of short and tall formSpartina alterniflora were measured monthly for 1 yr. Maximum emission rates, as high as 325 ml CO2m?2h?1, were observed during summer months, while minimum rates, 10.2 ml CO2 m?2h?1, were observed during the winter. An exponential function of inverse soil temperature explained most of the seasonal variability, but other factors are involved in regulating CO2 emissions as demonstrated by rates that were higher in spring than in late summer at equivalent temperatures. Annual CO2 emissions from bare sediments were 27.3 and 18.6 mol C m?2 yr?1 in communities of short and tallS. alterniflora, respectively. It was estimated that losses of dissolved inorganic carbon from the turnover of pore water, up to 14.6 mol C m?2 yr?1 at the creek bank (tall,S. alterniflora) site, and diffusion of CO2 from the root system ofS. alterniflora through the culms, 12.3 to 16.2 mol C m?2 yr?1, could also be important pathways of carbon loss from marsh sediments. If the internal flux of CO2 from the root system through the culm is refixed within the leaves, then the observed rate of 9.8 μI CO2 min?1 cm?2 of culm cross sectional area appears to make a small but significant contribution to total photosynthesis. 相似文献
7.
Lakes worldwide are commonly oversaturated with CO2, however the source of this CO2 oversaturation is not well understood. To examine the magnitude of the C flux to the atmosphere and determine if an excess of respiration (R) over gross primary production (GPP) is sufficient to account for this C flux, metabolic parameters and stable isotopes of dissolved O2 and C were measured in 23 Québec lakes. All of the lakes sampled were oversaturated with CO2 over the sampling period, on average 221 ± 25%. However, little evidence was found to conclude that this CO2 oversaturation was the result of an excess of pelagic R over GPP. In lakes Croche and à l’Ours, where CO2 flux, R and GPP were measured weekly, the annual difference between pelagic GPP and R, or net primary production (NPP), was not sufficient to account for the size of the CO2 flux to the atmosphere. In Lac Croche average annual NPP was 14.4 mg C m−2 d−1 while the average annual flux of CO2 to the atmosphere was 34 mg C m−2 d−1. In Lac à l’Ours average annual NPP was −9.1 mg C m−2 d−1 while the average annual flux of CO2 to the atmosphere was 55 mg C m−2 d−1. In all of the lakes sampled, O2 saturation averaged 104.0 ± 1.7% during the ice-free season and the isotopic composition of dissolved O2 (δ18ODO) was 22.9 ± 0.3‰, lower than atmospheric values and indicative of net autotrophy. Carbon evasion was not a function of R, nor did the isotopic signature of dissolved CO2 in the lakes present evidence of excess R over GPP. External inputs of C must therefore subsidize the lake to explain the continued CO2 oversaturation. The isotopic composition of dissolved inorganic C (δ13CDIC) indicates that the CO2 oversaturation cannot be attributed to in situ aerobic respiration. δ13CDIC reveals a source of excess C enriched in 13C, which may be accounted for by anaerobic sediment respiration or groundwater inputs followed by kinetic isotope fractionation during degassing under open system conditions. 相似文献
8.
It is important to have qualitative as well as quantitative understanding of the hydraulic exchange between lake and groundwater for effective water resource management. Dal, a famous urban fresh water lake, plays a fundamental role in social, cultural and economic dynamics of the Kashmir Valley. In this paper geochemical, isotopic and hydrological mass balance approaches are used to constrain the lake water–groundwater interaction of Dal Lake and to identify the sources of lake water. Water samples of precipitation (n = 27), lake water (n = 18) and groundwater (n = 32) were collected across the lake and its catchment for the analysis of δ18O and δ2H. A total of 444 lake water samples and 440 groundwater samples (springs, tube wells and dug wells) were collected for the analysis of Ca2+, Mg2+, HCO3 ?, SO4 2?, Cl?, NO3 ?, Na+ and K+. Water table and lake water level were monitored at 40 observation locations in the catchment. Water table map including pH and EC values corroborate and verify the gaining nature of the Dal Lake. Stable isotopes of lake water in Boddal and Gagribal basins showed more deviation from the global meteoric water line than Hazratbal and Nigeen basins, indicating the evaporation of lake water. The isotopic and geochemical mass balance suggested that groundwater contributes a significant proportion (23–40%) to Dal Lake. The estimated average groundwater contribution to Dal Lake ranged from 31.2 × 103 to 674 × 103 m3 day?1 with an average of 276 × 103 m3 day?1. The study will be useful to delineate the possible sources of nutrients and pollutants entering the lake and for the management of lake water resources for sustainable development. 相似文献
9.
Rachel F. S. Massaro Eric Heinen De Carlo Patrick S. Drupp Fred T. Mackenzie Stacy Maenner Jones Katie E. Shamberger Christopher L. Sabine Richard A. Feely 《Aquatic Geochemistry》2012,18(4):357-386
In this paper, we present the results of the first automated continuous multi-year high temporal frequency study of CO2 dynamics in a coastal coral reef ecosystem. The data cover 2.5?years of nearly continuous operation of the CRIMP-CO2 buoy spanning particularly wet and dry seasons in southern Kaneohe Bay, a semi-enclosed tropical coral reef ecosystem in Hawaii. We interpret our observational results in the context of how rapidly changing physical and biogeochemical conditions affect the pCO2 of surface waters and the magnitude and direction of air–sea exchange of CO2. Local climatic forcing strongly affects the biogeochemistry, water column properties, and gas exchange between the ocean and atmosphere in Kaneohe Bay. Rainfall driven by trade winds and other localized storms generates pulses of nutrient-rich water, which exert a strong control on primary productivity and impact carbon cycling in the water column of the bay. The “La Ni?a” winter of 2005–2006 was one of the wettest winters in Hawaii in 30?years and contrasted sharply with preceding and subsequent drier winter seasons. In addition, short-term variability in physical forcing adds complexity and helps drive the response of the CO2–carbonic acid system of the bay. Freshwater pulses to Kaneohe Bay provide nutrient subsidies to bay waters, relieving the normal nitrogen limitation of this system and driving phytoplankton productivity. Seawater pCO2 responds to the blooms as well as to physical forcing mechanisms, leading to a relatively wide range of pCO2 in seawater from about 250 to 650?μatm, depending on conditions. Large drawdowns in pCO2 following storms occasionally cause bay waters to switch from being a source of CO2 to the atmosphere to being a sink. Yet, during our study period, the southern sector of Kaneohe Bay remained a net source of CO2 to the atmosphere on an annualized basis. The integrated net annual flux of CO2 from the bay to the atmosphere varied between years by a factor of more than two and was lower during the wet “La Ni?a” year, than during the following year. Over the study period, the net annualized flux was 1.80?mol?C?m?2?year?1. Our CO2 flux estimates are consistent with prior synoptic work in Kaneohe Bay and with estimates in other tropical coral reef ecosystems studied to date. The high degree of climatological, physical, and biogeochemical variability observed in this study suggests that automated high-frequency observations are needed to capture the short-, intermediate-, and long-term variability of CO2 and other properties of these highly dynamic coastal coral reef ecosystems. 相似文献
10.
He Haibo Liu Zaihua Chen Chongying Wei Yu Bao Qian Sun Hailong Hu Yundi Yan Hao 《中国地球化学学报》2019,38(5):613-626
Biological carbon pumping (BCP) is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matter (AOC). However, the mechanisms underlying BCP and the amount of generated AOC deposited effectively, are still poorly understood. Therefore, we conducted a systematic study combining modern hydrochemical monitoring and a sediment trap experiment in Fuxian Lake (Yunnan, SW China), the second-deepest plateau, oligotrophic freshwater lake in China. Temperature, pH, EC (electrical conductivity), DO (dissolved O2), [HCO3−], [Ca2+], SIc, partial CO2 (pCO2) pressure, and carbon isotopic compositions of HCO3− (δ13CDIC) in water from Fuxian Lake all displayed distinct seasonal and vertical variations. This was especially apparent in an inverse correlation between pCO2 and DO, indicating that variations of hydrochemistry in the lake water were mainly controlled by the metabolism of the aquatic phototrophs. Furthermore, the lowest C/N ratios and highest δ13Corg were recorded in the trap sediments. Analyses of the C/N ratio demonstrated that the proportions of AOC ranged from 30% to 100% of all OC, indicating that AOC was an important contributor to sedimentary organic matter (OC). It was calculated that the AOC flux in Fuxian Lake was 20.43 t C km−2 in 2017. Therefore, AOC produced by carbonate weathering and aquatic photosynthesis could potentially be a significant carbon sink and may have an important contribution to solving the lack of carbon sinks in the global carbon cycle.
相似文献11.
Streams and rivers are major exporters of C and other dissolved materials from watersheds to coastal waters. In streams and rivers, substantial amounts of terrigenous organic C is metabolized and degassed as CO2 to the atmosphere. A long-term evaluation of CO2 dynamics in streams is essential for understanding factors controlling CO2 dynamics in streams in response to changes in climate and land-use. Long-term changes in the partial pressure of CO2 (pCO2) were computed in the Anacostia River and the lower Potomac River in the Chesapeake Bay watershed. Long-term estimates were made using routine monitoring data of pH, total alkalinity, and dissolved nutrients from 1985 to 2006 at 14 stations. Longitudinal variability in pCO2 dynamics was also investigated along these rivers downstream of the urban Washington D.C. metropolitan area. Both rivers were supersaturated with CO2 with respect to atmospheric CO2 levels (392 μatm) and the highly urbanized Anacostia waters (202–9694 μatm) were more supersaturated than the Potomac waters (557–3800 μatm). Long-term variability in pCO2 values may be due to changes in river metabolism and organic matter and nutrient loadings. Both rivers exchange significant amounts of CO2 with the atmosphere (i.e., Anacostia at 0.2–72 mmol m−2 d−1 and Potomac at 0.12–24 mmol m−2 d−1), implying that waterways receiving organic matter and nutrient subsidies from urbanized landscapes have the potential to increase river metabolism and atmospheric CO2 fluxes along the freshwater–estuarine continuum. 相似文献
12.
Rising atmospheric pCO2 and ocean acidification originating from human activities could result in increased dissolution of metastable carbonate minerals
in shallow-water marine sediments. In the present study, in situ dissolution of carbonate sedimentary particles in Devil’s
Hole, Bermuda, was observed during summer when thermally driven density stratification restricted mixing between the bottom
water and the surface mixed layer and microbial decomposition of organic matter in the subthermocline layer produced pCO2 levels similar to or higher than those levels anticipated by the end of the 21st century. Trends in both seawater chemistry
and the composition of sediments in Devil’s Hole indicate that Mg-calcite minerals are subject to selective dissolution under
conditions of elevated pCO2. The derived rates of dissolution based on observed changes in excess alkalinity and estimates of vertical eddy diffusion
ranged from 0.2 mmol to 0.8 mmol CaCO3 m−2 h−1. On a yearly basis, this range corresponds to 175–701 g CaCO3 m−2 year−1; the latter rate is close to 50% of the estimate of the current average global coral reef calcification rate of about 1,500 g
CaCO3 m−2 year−1. Considering a reduction in marine calcification of 40% by the year 2100, or 90% by 2300, as a result of surface ocean acidification,
the combination of high rates of carbonate dissolution and reduced rates of calcification implies that coral reefs and other
carbonate sediment environments within the 21st and following centuries could be subject to a net loss in carbonate material
as a result of increasing pCO2 arising from burning of fossil fuels. 相似文献
13.
《Geochimica et cosmochimica acta》1999,63(19-20):3357-3372
Lac Pavin is a volcanic crater lake in the Massif Central (France), characterized by a permanent vertical density stratification resulting from a strong and persistent chemocline between about 60 and 70 m depth. The deep water below the chemocline forms the monimolimnion, in which most dissolved ions as well as helium, carbon dioxide, and methane are strongly enriched. The 3He/4He isotope ratio of the excess helium is (9.09 ± 0.01) · 10−6, or (6.57 ± 0.01) Ra. These findings clearly indicate a flux of mantle-derived magmatic gases into the monimolimnion.In order to derive the fluxes of magmatic volatiles into Lac Pavin, it is essential to understand the hydrologic characteristics of the lake. Previously published two-box models have assumed groundwater input at the lake bottom, a short residence time in the monimolimnion, and biogenic origin of the CO2. We propose an alternative model with a flux of magmatic gases, but not of water, into the monimolimnion, and a weak diffusive coupling between the monimolimnion and the overlying mixolimnion which leads to a long deep-water residence time (≈ 70 yr). We reassess the carbon budget of the lake and conclude that the major part of the accumulated CO2 in the monimolimnion is of magmatic origin. From the model-derived water exchange rates, we calculated a mantle 4He flux of (6 ± 2) · 1011 atoms m−2 s−1. This value lies near the lower end of the range found in comparable volcanic lakes. The flux of magmatic CO2 is estimated as (1.2 ± 0.4) · 10−7 mol m−2 s−1, which is also comparatively low. The monimolimnion appears to be in steady state with respect to these fluxes, therefore no further, potentially hazardous, accumulation of CO2 takes place. 相似文献
14.
The carbonate system of waters of the inner, middle, and outer shelves was studied for a long period in the eastern part of the Laptev Sea. It is shown that the inner and middle shelves is a heterotrophic province and is a source of CO2 to the atmosphere during August–September. The average CO2 flux is 7.9 mmol m–2 day–1 and during one month waters of inner and middle shelves release into the atmosphere up to 0.7 Tg of carbon (C). The outer part of the shelf absorbs up to ~0.1 Tg C at an average rate of 3.9 mmol m–2 day–1 during the month. Generally, the ice-free zone of the eastern shelf of the Laptev Sea is a source of CO2 in the studied season: the amount of C released into the atmosphere within a month is ~0.6 Tg. 相似文献
15.
In situ measurements of the exchange of ammonia, nitrate plus nitrite, phosphate, and dissolved organic phosphorus between sediments and the overlying water column were made in a shallow coastal lagoon on the ocean coast of Rhode Island, U.S.A. The release of ammonia from mud sediments in the dark (20–440 μmol per m2 per h) averaged ten times higher than from a sandy tidal flat (0–60 μmol per m2 per h), and while mud sediments also released nitrate and phosphate, sandy sediments took up these nutrients. Fluxes of nutrients from mud sediments, but not from sandy areas, markedly increased with temperature. Ammonia release rates for mud sediments in the light (0–350 μmol per m2 per h) were lower than those in the dark and it is estimated that some 25% of the ammonia released to the water column on an annual basis may be intercepted by the benthic microfloral community. Estimates of the annual net exchange of nutrients across the sediment-water interface, weighted by sediment type for the lagoon as a whole, showed a release of 450 mmol per m2 of ammonia, 5 mmol per m2 of phosphate, 5 mmol per m2 of dissolved organic phosphorus, and an uptake of 80 mmol per m2 of nitrate. Although rates of ammonia and nitrate exchange were comparable to those described for the deeper heterotrophic bottom communities of nearby Narragansett Bay, rates of benthic phosphate release were significantly lower. On an annual basis the Bay benthos released approximately 20 times more inorganic phosphate per unit area than did the lagoon benthos. As a result., the N/P ratio for the flux from the sediments was 74∶1 in the lagoon, compared with 16∶1 in “average” marine plankton and 8∶1 for the benthic flux from Narragansett Bay. The lack of remineralized phosphate in the lagoon, is reflected in water, column phosphate concentrations (always <1 μm) and water column N/P ratios (annual N/P=27) and suggests that the lagoon may show phosphate limitation rather than the nitrogen limitation commonly associated with marine systems. 相似文献
16.
西藏阿里地区泽错大型盐湖锂（硼）矿床的发现及开发利用前景 总被引：1，自引：0，他引：1
2016—2018年中国地质调查局天津地质调查中心联合西藏自治区地质矿产勘查开发局第五地质大队组建盐湖调查队伍,针对西藏羌塘盆地西段泽错盐湖开展调查评价工作,探获大型锂(硼)矿产地1处。泽错湖表水体长16.3 km,宽3.3～11.3 km,湖表面积113.8 km2。湖水深度变化较大,四周水较浅,逐渐向中间变深,最深处达44 m,湖水平均深度为24 m,湖面海拔4940 m。泽错盐湖位于藏北羌塘—三江复合板块内,矿区第四纪地层可划分为更新统湖积,全新统现代湖水,全新统冲洪积,全新统冲积和全新统湖积。湖盆可划分基岩裂隙水层、亚砂土孔隙含水层、亚黏土孔隙含水层和湖表卤水4个水文地质单元。经计算直接补充到湖盆表面的大气降水量为1.081×107m3/a,地表水补给湖水量为8.262×107m3/a,地下水补给量为2.052×107m3/a,泽错年补给水量为11.395×107m3/a左右。自然蒸发为泽错湖盆的主要排泄方式,泽错湖水年蒸发量为12.745×107m3/a,年均水量变化值为1.35×107m3/a,地表水补给湖水带入的总盐量为7.8×104t/a。泽错湖盆卤水中主要成盐元素有Cl-、Na+、SO42-、K+、CO32-、HCO3-、B2O3、Mg2+、Li+等,平均矿化度41.57 g/L,pH值为9.31,泽错湖水为高矿化度盐水,水化学类型为硫酸钠亚型。泽错盐湖LiCl平均品位为376.02 mg/L,LiCl资源量为102.68×104t,远景规模达到大型;B2O3平均品位为840 mg/L,B2O3资源量为229.38×104t,远景规模达到大型。在综合分析锂、硼资源需求、提锂技术、盐田建设、气候条件、经济价值等方面的基础上,对泽错盐湖的开发利用前景进行了展望。 相似文献
17.
Christopher W. Hunt Joseph E. Salisbury Douglas Vandemark 《Estuaries and Coasts》2014,37(5):1078-1091
Repeated surveys of the Kennebec estuary, a macrotidal river estuary in Maine, USA, between 2004 and 2008 found spatial and temporal variability both in sources of carbon dioxide (CO2) to the estuary and the air–sea flux of estuary CO2. On an annual basis, the surveyed area of the Kennebec estuary had an area-weighted average partial pressure of CO2 (pCO2) of 559 μatm. The area-weighted average CO2 flux to the atmosphere was 3.54 mol C m?2 year?1. Overall, the Kennebec estuary was an annual source of 7.2?×?107 mol CO2 to the atmosphere. Distinct seasonality in estuarine pCO2 was observed, with shifts in the seasonal pattern evident between lower and higher salinities. Fluxes of CO2 from the estuary were elevated following two summertime storms, and inputs of riverine CO2 outweighed internal estuarine CO2 inputs in nearly all months. River and estuarine inputs of CO2 represented 68 and 32 % of the total CO2 contributions to the estuary, respectively. This study examines the variability of CO2 in a large New England estuary, and highlights the comparatively high contribution of CO2 from riverine sources. 相似文献
18.
Evaporation and energy balance estimates over a large inland lake in the Tibet-Himalaya 总被引：2，自引：1，他引：1
The process of evaporation from the lake surface is one of the main mechanisms in the energy and water budgets of the lake
hydrologic cycle, and an essential component of the water balance especially for inland lakes. In this study, using routine
meteorological data as input, a one-layer potential evaporation model was employed to simulate evaporation and energy fluxes
over Lake Yamdrok Yumco, the largest high-elevation inland lake in the mountain area of the Tibet-Himalaya in China. Then,
the calculation results were compared with the measured values from a big pan evaporator of 20 m2 near the lake. The results show that the average annual input radiation flux R
↓ is 128.2 W m−2, the lake storage heat flux G is 19.4 W m−2, the sensible heat flux H is 20.4 W m−2 and the latent heat flux lE is 107.8 W m−2. The R
↓ and G exhibit similar seasonal variations. The lE reaches a maximum in October, lagging nearly 4 months behind the R
↓ and the G, which indicates the large heat capacity of the lake. The simulated annual evaporation ranges from 1,113.2 to 1,429.1 mm
and its mean value is 1,252.5 mm during 1961–2005. The simulated annual evaporation is in good agreement with the measured
value, and the measured average lake temperature is as expected when compared with the measured lake surface temperature. 相似文献
19.
The quantification of carbon burial in lake sediments, and carbon fluxes derived from different origins are crucial to understand modern lacustrine carbon budgets, and to assess the role of lakes in the global carbon cycle. In this study, we estimated carbon burial in the sediment of Lake Qinghai, the largest inland lake in China, and the carbon fluxes derived from different origins. We find that: (1) The organic carbon burial rate in lake sediment is approximately 7.23 g m−2 a−1, which is comparable to rates documented in many large lakes worldwide. We determined that the flux of riverine particulate organic carbon (POC) is approximately 10 times higher than that of dissolved organic carbon (DOC). Organic matter in lake sediments is primarily derived from POC in lake water, of which approximately 80% is of terrestrial origin. (2) The inorganic carbon burial rate in lake sediment is slightly higher than that of organic carbon. The flux of riverine dissolved inorganic carbon (DIC) is approximately 20 times that of DOC, and more than 70% of the riverine DIC is drawn directly and/or indirectly from atmospheric CO2. (3) Both DIC and DOC are concentrated in lake water, suggesting that the lake serves as a sink for both organic and inorganic carbon over long term timescales. (4) Our analysis suggests that the carbon burial rates in Lake Qinghai would be much higher in warmer climatic periods than in cold ones, implying a growing role in the global carbon cycle under a continued global warming scenario. 相似文献
20.
Methane and carbon dioxide flux from a macrotidal salt marsh,Bay of Fundy,New Brunswick 总被引：1，自引：0，他引：1
Fluxes of methane (CH4) and carbon dioxide (CO2) to the atmosphere at 52 sites within a salt marsh were measured by a dark static chamber technique from mid July to mid September. Mean CH4 fluxes ranged from 0.2 mg m?2 d?1 to 11.0 mg m?2 d?1, with an overall average of 1.6 mg m?2 d?1. Flux of CH4 was inversely correlated (r2=0.23, p = 0.001) with salinity of the upper porewater at the site, suggesting the dominant role of SO4 2? in inhibiting methanogenesis in salt-marsh sediments. The combination of salinity and water table position was able to explain only 29% of the variance in CH4 emission. Mean soil flux of CO2 ranged from 0.3 g m?2 d?1 to 3.7 g m?2 d?1, with an overall average of 2.5 g m?2 d?1; it was correlated with aboveground biomass (positive, r2=0.38, p = 0.001) and position of the water table (negative, r2 = 0.55, p = 0.001). The combination of biomass and water table position accounted for 63% of the variance in CO2 flux. There were high variations in gas flux within the six plant communities. The sequences were CH4: upland edge > panne > pool > middle marsh > low marsh > high marsh, and CO2: middle marsh > low marsh > upland edge > high marsh > panne > pool. Compared to other salt-marsh systems, this Bay of Fundy marsh emits small amounts of CH4 and CO2. 相似文献