Fluxes of carbon dioxide, methane and nitrous oxide in two contrastive fringing zones of coastal lagoon, Lake Nakaumi, Japan

We measured fluxes of carbon dioxide (CO(2)), methane (CH(4)), and nitrous oxide (N(2)O) simultaneously in two typical fringing zones, sandy shore and salt marsh, of coastal lagoon, Lake Nakaumi, Japan, in mid-summer 2003. Our aim was to quantify net the greenhouse gases (GHGs) fluxes and examine key factors, which control variation of the GHGs fluxes in the two sites. Net CO(2) and CH(4) fluxes were markedly different between the two sites; magnitudes and variations of the both fluxes in sandy shore were lower than those of salt marsh. Meanwhile, magnitude and variation of net N(2)O flux in the two sites were similar. In sandy shore, temporal and spatial variation of the three GHGs fluxes were highly controlled by water level fluctuation derived from astronomic tide. In salt marsh, spatial variation of the three GHGs fluxes were correlated with aboveground biomass, and temporal variation of CO(2) and CH(4) fluxes were correlated with soil temperature. The sum of global warming potential, which was roughly estimated using the observed GHGs fluxes, was ca. 174-fold higher in salt marsh than in sandy shore.     

Carbon dioxide and methane emissions from the scale model of open dairy lots

To investigate the impacts of major factors on carbon loss via gaseous emissions, carbon dioxide (CO₂) and methane (CH₄) emissions from the ground of open dairy lots were tested by a scale model experiment at various air temperatures (15, 25, and 35 °C), surface velocities (0.4, 0.7, 1.0, and 1.2 m sec^?1), and floor types (unpaved soil floor and brick-paved floor) in controlled laboratory conditions using the wind tunnel method. Generally, CO₂ and CH₄ emissions were significantly enhanced with the increase of air temperature and velocity (P < 0.05). Floor type had different effects on the CO₂ and CH₄ emissions, which were also affected by air temperature and soil characteristics of the floor. Although different patterns were observed on CH₄ emission from the soil and brick floors at different air temperature-velocity combinations, statistical analysis showed no significant difference in CH₄ emissions from different floors (P > 0.05). For CO₂, similar emissions were found from the soil and brick floors at 15 and 25 °C, whereas higher rates were detected from the brick floor at 35 °C (P < 0.05). Results showed that CH₄ emission from the scale model was exponentially related to CO₂ flux, which might be helpful in CH₄ emission estimation from manure management.

Implications: Gaseous emissions from the open lots are largely dependent on outdoor climate, floor systems, and management practices, which are quite different from those indoors. This study assessed the effects of floor types and air velocities on CO₂ and CH₄ emissions from the open dairy lots at various temperatures by a wind tunnel. It provided some valuable information for decision-making and further studies on gaseous emissions from open lots.     

Carbon dioxide fluxes over a grazed prairie and seeded pasture in the Northern Great Plains

Temperate grasslands are vast terrestrial ecosystems that may be an important component of the global carbon (C) cycle; however, annual C flux data for these grasslands are limited. The Bowen ratio/energy balance (BREB) technique was used to measure CO2 fluxes over a grazed mixed-grass prairie and a seeded western wheatgrass [Pascopyrum smithii (Rybd) L?ve] site at Mandan, ND from 24 April to 26 October in 1996, 1997, and 1998. Above-ground biomass and leaf area index (LAI) were measured about every 21 days throughout the season. Root biomass and soil organic C and N content were determined to 110 cm depth in selected increments about mid-July each year. Peak above-ground biomass and LAI coincided with peak fluxes and occurred between mid-July to early August. Biomass averaged 1227 and 1726 kg ha(-1) and LAI 0.44 and 0.59, for prairie and western wheatgrass, respectively. Average CO2 flux for the growing season was 279 g CO2 m(-2) for prairie and 218 g CO2 m(-2) for western wheatgrass (positive flux is CO2 uptake and negative flux is CO2 loss to the atmosphere). Using prior measured dormant season CO2 fluxes from the prairie sites gave annual flux estimates that ranged from -131 to 128 g CO2 m(-2) for western wheatgrass and from -70 to 189 g CO2 m(-2) for the prairie. This wide range in calculated annual fluxes suggests that additional research is required concerning dormant season flux measurements to obtain accurate estimates of annual CO2 fluxes. These results suggest Northern Great Plains mixed-grass prairie grasslands can either be a sink or a source for atmospheric CO2 or near equilibrium, depending on the magnitude of the dormant season flux.     

Fluxes of methane,carbon dioxide and nitrous oxide in boreal lakes and potential anthropogenic effects on the aquatic greenhouse gas emissions

We have examined how some major catchment disturbances may affect the aquatic greenhouse gas fluxes in the boreal zone, using gas flux data from studies made in 1994-1999 in the pelagic regions of seven lakes and two reservoirs in Finland. The highest pelagic seasonal average methane (CH(4)) emissions were up to 12 mmol x m(-2) x d(-1) from eutrophied lakes with agricultural catchments. Nutrient loading increases autochthonous primary production in lakes, promoting oxygen consumption and anaerobic decomposition in the sediments and this can lead to increased CH(4) release from lakes to the atmosphere. The carbon dioxide (CO(2)) fluxes were higher from reservoirs and lakes whose catchment areas were rich in peatlands or managed forests, and from eutrophied lakes in comparison to oligotrophic and mesotrophic sites. However, all these sites were net sources of CO(2) to the atmosphere. The pelagic CH(4) emissions were generally lower than those from the littoral zone. The fluxes of nitrous oxide (N(2)O) were negligible in the pelagic regions, apparently due to low nitrate inputs and/or low nitrification activity. However, the littoral zone, acting as a buffer for leached nitrogen, did release N(2)O. Anthropogenic disturbances of boreal lakes, such as increasing eutrophication, can change the aquatic greenhouse gas balance, but also the gas exchange in the littoral zone should be included in any assessment of the overall effect. It seems that autochthonous and allochthonous carbon sources, which contribute to the CH(4) and CO(2) production in lakes, also have importance in the greenhouse gas emissions from reservoirs.     

潜水丁坝在湖滨带生态恢复中的应用

为保护和稳固湖滨带,在太湖梅梁湾进行生态恢复研究,并成功地实施了示范工程.沿湖滨带共构筑14道潜水丁坝,每道长23～28 m,坝间距为40～80 m,坝上种植芦苇和菰.构筑的潜水丁坝能经受住太湖常见大风袭击和湖流淘蚀,芦苇和菰等长势良好,湖滨原有芦苇带在一定水深范围内每年向湖延伸2～5 cm,坝上其他水生植物和底栖动物螺蛳等自然繁衍.潜水丁坝所起作用为利用自然力改变岸边流场,使泥沙在湖滨带预定沉积区内沉积,减缓岸边侵蚀和降低沉积物再悬浮,从而为湖滨带水生植物生长创造良好的生境条件.研究发现,在微风条件下,潜水丁坝群能有效拦截麇集于岸边的蓝绿藻,并在湖滨带进行消化降解.研究提出的构筑潜水丁坝并种植水生植物的方案为湖滨带生态恢复提供了一种新的探索途径.     

Degradation of littoral habitats by residential development: woody debris in lakes of the Pacific Northwest and Midwest, United States

One of the least understood aspects of aquatic ecology is the role of riparian zones of lakes, and how these habitats and their functions are impacted by human development of lakeshores. We investigated the effects of residential lakeshore development on littoral coarse woody debris (CWD) distribution and on riparian forest characteristics by comparing 18 lakes in the U.S. Pacific Northwest with 16 previously surveyed lakes in the U.S. Upper Midwest. Residential development had a strong negative effect on CWD and riparian forest characteristics at both local and whole-lake scales. There was a strong positive correlation between riparian forest density and littoral CWD abundance in both regions. We found regional variation in CWD and riparian forest characteristics, mostly owing to differences in native forests. Our results suggest the role of local processes in determining CWD distribution and point to potential regional differences in littoral habitat structure associated with forest composition and lakeshore development that may have consequences for littoral-pelagic coupling in lakes.     

垃圾填埋场甲烷氧化菌及甲烷通量的研究

采用静态箱法、滚管计数法和气相色谱法,对6个不同封场时间填埋区的甲烷通量、覆土层甲烷氧化菌数量和甲烷氧化速率的变化趋势进行了测定,并分析了它们与封场时间、植被覆盖率等因素之间的相关性。结果发现6个填埋区甲烷通量的变化范围在-0.34～5.31 mg/(m2.h)之间;覆土层甲烷氧化菌的数量范围为3.10×107～20.77×107 cfu/g干土,甲烷氧化速率在1.65×10-8～4.34×10-8mol/(h.g)之间。覆土层甲烷氧化菌的数量与甲烷氧化速率呈正相关,但前者并不是后者的决定性因素;甲烷通量高时可刺激甲烷氧化菌数量及氧化速率的提高,且三者均与封场时间呈显著负相关,与植被覆盖率呈负相关;当含水率大于15%时,随着覆土层含水率的增加,甲烷氧化速率呈下降趋势;覆土pH、有机质和铵态氮与甲烷氧化速率等无明显相关性。提高覆土层的甲烷氧化速率可有效减少垃圾填埋场的甲烷排放。     

Carbon dioxide emissions,output, and energy consumption categories in Algeria

This study examines the relation between CO₂ emissions, income, non-renewable, and renewable energy consumption in Algeria during the period extending from 1980 to 2011. Our work gives particular attention to the validity of environmental Kuznets curve (EKC) hypothesis. The autoregressive distributed lag (ARDL) with break point method outcome demonstrates the positive effect of non-renewable type of energy on CO₂ emissions consumption. On the contrary, the results reveal an insignificant effect of renewable energy on environment improvement. Moreover, the results accept the existence of EKC hypothesis but the highest gross domestic product value in logarithm scale of our data is inferior to the estimated turning point. Consequently, policy-makers in Algeria should expand the ratio of renewable energy and should decrease the quota of non-renewable energy consumption.     

Carbon dioxide warming of the early Earth

Svante Arrhenius' research in atmospheric physics extended beyond the recent past and the near future states of the Earth, which today are at the center of sociopolitical attention. His plan encompassed all of the physical phenomena known at the time to relate to the formation and evolution of stars and planets. His two-volume textbook on cosmic physics is a comprehensive synopsis of the field. The inquiry into the possible cause of the ice ages and the theory of selective wavelength filter control led Arrhenius to consider the surface states of the other terrestrial planets, and of the ancient Earth before it had been modified by the emergence of life. The rapid escape of hydrogen and the equilibration with igneous rocks required that carbon in the early atmosphere prevailed mainly in oxidized form as carbon dioxide, together with other photoactive gases exerting a greenhouse effect orders of magnitude larger than in our present atmosphere. This effect, together with the ensuing chemical processes, would have set the conditions for life to evolve on our planet, seeded from spores spreading through an infinite Universe, and propelled, as Arrhenius thought, by stellar radiation pressure.     

Quantifying simultaneous fluxes of ozone, carbon dioxide and water vapor above a subalpine forest ecosystem

Assessing the long-term exchange of trace gases and energy between terrestrial ecosystems and the atmosphere is an important priority of the current climate change research. In this regard, it is particularly significant to provide valid data on simultaneous fluxes of carbon, water vapor and pollutants over representative ecosystems. Eddy covariance measurements and model analyses of such combined fluxes over a subalpine coniferous forest in southern Wyoming (USA) are presented. While the exchange of water vapor and ozone are successfully measured by the eddy covariance system, fluxes of carbon dioxide (CO(2)) are uncertain. This is established by comparing measured fluxes with simulations produced by a detailed biophysical model (FORFLUX). The bias in CO(2) flux measurements is partially attributed to below-canopy advection caused by a complex terrain. We emphasize the difficulty of obtaining continuous long-term flux data in mountainous areas by direct measurements. Instrumental records are combined with simulation models as a feasible approach to assess seasonal and annual ecosystem exchange of carbon, water and ozone in alpine environments. The viability of this approach is demonstrated by: (1) showing the ability of the FORFLUX model to predict observed fluxes over a 9-day period in the summer of 1996; and (2) applying the model to estimate seasonal dynamics and annual totals of ozone deposition and carbon, and water vapor exchange at our study site. Estimated fluxes above this subalpine ecosystem in 1996 are: 195 g C m(-2) year(-1) net ecosystem production, 277 g C m(-2) year(-1) net primary production, 535 mm year(-1) total evapo-transpiration, 174 mm year(-1) canopy transpiration, 2.9 g m(-2) year(-1) total ozone deposition, and 1.72 g O(3) m(-2) year(-1) plant ozone uptake via leaf stomata. Given the large portion of non-stomatal ozone uptake (i.e. 41% of the total annual flux) predicted for this site, we suggest that future research of pollution-vegetation interactions should relate plant response to actively assimilated ozone by foliage rather than to total deposition. In this regard, we propose the Physiological Ozone Uptake Per Unit of Leaf Area (POUPULA) as a practical index for quantifying vegetation vulnerability to ozone damage. We estimate POUPULA to be 0.614 g O(3) m(-2) leaf area year(-1) at our subalpine site in 1996.     

Ecotoxicological effects of metal pollution in two mollusc species from the Spanish South Atlantic littoral

Metal accumulation and some of their biochemical effects have been studied in oysters (Crassostrea angulata) and mussels (Mytilus galloprovincialis) of the South Atlantic Spanish littoral. Especial attention has been paid to antioxidant defences and oxidative damage to biomolecules. Deep differences in the response of oysters and mussels to metal pollution were found. Oysters, with the higher metal loads of both species, showed increased antioxidant defences, and less extensive oxidative damage. In contrast, mussels, which accumulated much lower metal concentrations, showed clear increases in oxidized biomolecules, in agreement with their low increases in the antioxidant defence mechanisms. Our results suggest that mussels are more sensitive and less well adapted to metal pollution, probably explaining their absence in the most contaminated studied site, Mazagón. We conclude that oysters can be used as more sensitive bioindicator of pollution in the South Spanish littoral, and as a suitable model to study the adaptation to metal pollution.     

Concentration field and turbulent fluxes during the mixing of two buoyant plumes

In this work an experimental study of mixing of two identical plumes, carried out in a turbulent neutral boundary layer generated in a wind tunnel, is presented. Measurements have been performed with fast flame ionisation detectors (FFIDs) and a two-component Laser-Doppler Anemometer system. Results allow the study of both the average and the fluctuating concentration field, including the turbulent vertical and longitudinal mass fluxes, in single plumes and during the interaction of two identical plumes. This information gives insight into the details of the mixing phase of the two plumes. Results of trajectories and additional rise (due to plume interactions) have been compared with previous measurements carried out in laminar cross-flows, showing similar behaviour. Concentration distributions in plume cross-sections in turbulent cross-flows differ from those measured in laminar cross-flows. Average vertical and longitudinal velocity measurements into the plume core show the strength of the shielding effect of the upwind plume and some details of interaction between the counter-rotating vortex pairs (CVPs). For large values of the alignment angle φ, between the line joining the stacks and the cross-flow, an average negative vertical velocity is measured in the middle of the plume even if its centre of mass is rising. This downward velocity is induced by the slow interaction of the CVPs and generates a vertical stretching of the plume and negative rise enhancement. Vertical turbulent fluxes change sign on the plume centreline and are of opposite sign with respect to the longitudinal turbulent fluxes. Results indicate a good linearity between vertical turbulent fluxes and concentration gradients, with different proportionality for the top and bottom parts of the plume (especially in the near field) indicating that dispersion could be described by a gradient-transfer model.     

Carbon dioxide mineralization process design and evaluation: concepts,case studies,and considerations

Numerous carbon dioxide mineralization (CM) processes have been proposed to overcome the slow rate of natural weathering of silicate minerals. Ten of these proposals are mentioned in this article. The proposals are described in terms of the four major areas relating to CM process design: pre-treatment, purification, carbonation, and reagent recycling operations. Any known specifics based on probable or representative operating and reaction conditions are listed, and basic analysis of the strengths and shortcomings associated with the individual process designs are given in this article. The processes typically employ physical or chemical pseudo-catalytic methods to enhance the rate of carbon dioxide mineralization; however, both methods have its own associated advantages and problems. To examine the feasibility of a CM process, three key aspects should be included in the evaluation criteria: energy use, operational considerations as well as product value and economics. Recommendations regarding the optimal level of emphasis and implementation of measures to control these aspects are given, and these will depend very much on the desired process objectives. Ultimately, a mix-and-match approach to process design might be required to provide viable and economic proposals for CM processes.     

Seasonal fluxes and temperature-dependent accumulation of persistent organic pollutants in lakes: The role of internal biogeochemical cycling

A dynamic flux model for lakes taking into account the interactions between atmospheric depositional and biogeochemical processes (BIODEP model) was used to assess the importance of internal cycling and biogeochemical processes with respect to accumulation of four different polychlorinated biphenyls (PCBs) (congeners 28, 52, 101 and 153) in Lake Redo, a high-altitude lake in the Spanish Pyrenees. To investigate the effect of temperature on sediment accumulation, the model was run at different temperatures and corresponding sediment inventories were plotted vs. reciprocal temperature. In line with measurements from a previous study looking at sediment inventories of 19 European high-altitude lakes (MOLAR study), we found a stronger temperature dependence of lake sediment concentrations for the less volatile/less soluble PCBs. Seasonal and annual mass balances were investigated and highlighted the importance of internal lake processes controlling the differences in sediment accumulation for the different PCB congeners. For example, the higher temperature dependence of sediment inventories for the high chlorinated congeners is due to the fast dynamics of water-to-sediment transport in comparison to atmospheric deposition processes.     

Local-scale fluxes of carbon dioxide in urban environments: methodological challenges and results from Chicago

Much attention is being directed to the measurement and modeling of surface-atmosphere exchanges of CO2 for different surface types. However, as yet, few measurements have been conducted in cities, even though these environments are widely acknowledged to be major sources of anthropogenic CO2. This paper highlights some of the challenges facing micrometeorologists attempting to use eddy covariance techniques to directly monitor CO2 fluxes in urban environments, focusing on the inherent variability within and between urban areas, and the importance of scale and the appropriate height of measurements. Results from a very short-term study of CO2 fluxes, undertaken in Chicago, Illinois in the summer of 1995, are presented. Mid-afternoon minimum CO2 concentrations and negative fluxes are attributed to the strength of biospheric photosynthesis and strong mixing of local anthropogenic sources in a deep mixed layer. Poor night-time atmospheric mixing, lower mixed layer depths, biospheric respiration, and continued missions from mobile and fixed anthropogenic sources, account for the night-time maxima in CO2 concentrations. The need for more, longer-term, continuous eddy covariance measurements is stressed.     

Effect of ammonium and oxygen on methane and nitrous oxide fluxes across sediment-water interface in a eutrophic lake

Eutrophication has decreased the O(2) content and increased the NH(4)(+) availability in freshwaters. These changes may affect carbon and nitrogen transformation processes and the production of CH(4) and N(2)O, which are important greenhouse gases. We studied release of CH(4) and N(2)O from a eutrophic lake sediment under varying O(2) and NH(4)(+) conditions. Intact sediment cores were incubated in a laboratory microcosm with a continuous anoxic or oxic water flows containing 0, 50, 500, 5,000, or 15000 microM NH(4)(+). With the anoxic flow, the sediment released CH(4), up to 7.9 mmol m(-2)d(-1). With the oxic flow, the CH(4) emissions were small indicating limited CH(4) production and/or effective CH(4) oxidation. Addition of NH(4)(+) did not affect sediment CH(4) release, evidence that the CH(4) oxidizing bacteria were not disturbed by the extra NH(4)(+). The release of N(2)O from the sediment was highest, up to 7.6 micromol m(-2)d(-1), with the oxic flow without NH(4)(+) addition. Oxygen was the key factor regulating the production of NO(3)(-), which enabled denitrification and production of N(2)O. However, the highest NH(4)(+) addition increased nitrification and associated O(2) consumption causing a decrease in sediment O(2) content and in accumulation of NO(3)(-) and N(2)O, which were effectively reduced to N(2) in denitrification. In summary, sediment CH(4) and N(2)O dynamics are regulated more by the availability of O(2) than extra NH(4)(+). Anoxia in eutrophic lakes favouring the CH(4) production, is the major contributor to the atmospheric consequences of water eutrophication.     

Changes in the density, population structure, growth and reproduction of perch, Perca fluviatilis L. in two acidic forest lakes in southern Finland

The density of the perch populations decreased rapidly during the 1980s in two acidified lakes in southern Finland. In an acid-humic lake the density of the perch population decreased from 240 to 60 ha(-1) and in an acid clearwater lake from 150 to 20 ha(-1). In both lakes the rapid decrease was mainly due to failures in reproduction, although post-spawning mortality of adult fish was also recorded. The perch spawned annually in both lakes but according to the field exposures of egg strands, most of the eggs died before hatching. Nevertheless, some new recruits appeared in both lakes. These perch, born in 1983-1986, grew faster than those of the more abundant year-classes of the late 1970s, indicating a clear density-dependent growth response. According to the mortality estimate and the age distribution of perch, the latest year-classes that produced more than 100 adult perch ha(-1) were born in 1978 or 1979 in both lakes. It was calculated that the density of both populations was >500 ha(-1) in the early 1980s.     

Carbon dioxide emissions,urbanization level,and industrial structure: empirical evidence from North China

Environmental Science and Pollution Research - This paper aims to examine the nexus among carbon dioxide (CO2) emissions, urbanization level and industrial structure in North China over the period...     

Comparison of microbial community between two shallow freshwater lakes in middle Yangtze basin, East China

In order to investigate the role of the microbial community in aquatic ecology and nutrient transformations in the development of eutrophication in large shallow freshwater lakes along Yangtze River, the microbial community in the depth-related sediment in Lake Chaohu and Lake Longganhu were compared. Lake Chaohu is one of the three most polluted lakes in China. However, the neighboring Lake Longganhu, a mesotrophic lake, is relatively pristine. The total phosphorous (TP) and total nitrogen (TN) concentration in water was detected at 0.193 mgl(-1) and 3.035 mgl(-1) for Lake Chaohu, 0.051 mgl(-1) and 0.774 mgl(-1) for Lake Longganhu, respectively. The population of the microorganisms with various ecological nutrient transforming functions (e.g. phosphate solubilizing, denitrifying and cellulose decomposing) and a batch of environmental parameters concerning the nutrient accumulating and transforming (e.g. total organic carbon, total nitrogen, and total phosphorous concentrations) were assayed in the depth-related sediment samples from several defined points in both lakes. The sediment samples from Lake Chaohu showed higher density of actinomycetes (P<0.05) and phosphate-solubilizing bacteria (P<0.001) and less profusion of denitrifying bacteria (P<0.05) and cellulolytic microbes (P<0.001), compared with those of Lake Longganhu. The data suggested that the current microbial community in the sediment of Lake Chaohu is in favor of sustaining or further accelerating the process of the lake eutrophication. A possible positive feedback loop which consists of sustained growth of microorganisms and gradual decline of lake eutrophic status is worth further discussing.