Shaw, 1995). Restoring a damaged peatland to previous hydrological and
biodiversity conditions may not be possible (Gorham and Rochefort, 2003). Firstly, the previous conditions for which to aim for with restoration may not be known (Gorham and Rochefort, 2003). Secondly, drainage can permanently damage the hydrological regime of a peatland due to the exposure of previously anoxic peat layers, changing the water storage capabilities and ultimately making it impossible to return the hydrology to a former ‘pristine’ state (Price, 1997; Schlotzhauer and Price, 1999). Alexander et al. (2008) indicated that a peatland that had been damaged could never be returned to its natural state, and that areas where peat extraction occurred via milling were more difficult to restore than block-cut areas due to the deeper drainage required for milling. Chapman et al. (2003) suggested that the spontaneous regeneration of peatland vegetation was harder to establish on areas that had been milled, and that block-cut areas could actually increase biodiversity by creating transition zones and re-establishing vegetation that had previously vanished due to successional changes. Wind-Mulder and Vitt (2000) conducted five years of monitoring on a natural peatland and a peatland where drainage and extraction had occurred. The damaged peatland was previously a bog, but had been returned to the fen-to-bog transition stage due to extraction, and so the peat and water chemistry were different to the original conditions (Wind-Mulder and Vitt, 2000). Haapalehto et al. (2011) studied a peatland that had originally been drained for forestry and was then restored through drain-blocking and deforestation, with a neighbouring undamaged area. Ten years after
Finally, it is important to consider the effect of our experimental design on our findings. Our flux data showed high spatial variability, and this, combined with the small (spatial) sample size, will have affected the outcomes (the power) of our statistical tests. Despite our study involving over 900 gas flux measurements, we recommend greater spatial replication in future studies of blanket bogs. An additional aspect of our experimen- tal design, as shown by Holden et al. (2017), is that the treatments were not wholly hydrologically isolated from each other, partly because the ditches were not aligned exactly with the maximum slope (Fig. 1). Therefore, a reprofiled ditch next to an open ditch (Fig. 1) could have been drier than if it was in a larger area where all ditches had been blocked using the reprofiling method. Such hydrological effects could have influenced the gas flux results and should be borne in mind as a possible con- founding factor in our analysis. Nevertheless, hydrologically-large differences were observed between treatments. The pools that formed behind the dams in the reprofiled treatment gave clearly wetter conditions than in the control or open ditches. Additionally, the infilling of the reprofiled ditches is likely to have had a greater hydrological effect than interactions between treatments and can explain why water-table depths were greater in the reprofiled ditches away from the dams than in the open ditches.
A widely used direct flux measurement technique is the floating chamber (FC) method, where the vertical flux at the air–water interface is calculated from the concentration in- crease within the chamber during the measurement period (Livingston and Hutchinson, 1995). This method has a small source area and is representative of the measurement point only. On the other hand, it can be used to quantify the spatial variability of the gas emissions (Natchimuthu et al., 2016). FC method is laborious, but inexpensive, and does not need extensive data post-processing. However, similar to BLM, it requires automatic data loggers or access to a gas anal- yser, such as a gas chromatograph, in the case of manual sampling. FC measurements also disturb the air–water in- terface and might affect the gas exchange by creating arti- ficial turbulence, especially with anchored chambers in run- ning waters (Lorke et al., 2015). However, these effects are minor for drifting chambers following the water (Lorke et al., 2015). FC measurements on standing water can also corre- spond well with non-invasive methods for certain chamber types and deployment methods (Gålfalk et al., 2013).
In the UK, which formed the initial focus for this review, lowland peat ecosystems are less commonly studied than upland peatlands. In many other areas of the boreo- temperate zone, where continental type bogs and fens pre- dominate, a distinction between ‘upland’ and ‘lowland’ peats is rarely made, with most peatlands (and hence most peat-related research) falling within the latter category. Nevertheless, this systematic review has demonstrated that there are relatively few studies in the evidence base that provide robust comparisons of C and GHG fluxes in relation to management, and that more studies are re- quired on the impacts of land management on lowland peatland systems. We have identified a range of com- monly investigated land management practices and a list of commonly recorded outcome measures. These findings demonstrate the key knowledge gaps within this topic area. They also highlight areas for which some evidence currently exists but where additional data are required to strengthen current findings. Table 10 demonstrates the major gaps in the evidence-base in regards to meta- analysable groups of studies. These knowledge gaps ap- pear to lie in the following areas: the effect of restoration on N 2 O emissions; the effect of fertilizer on fluxes of all
pH and organic matter both declined with distance from plant stems under both species, although these differences were only significant for R. taedigera. In general, differences in peat properties between species were reduced compared to previous studies, with only pH differing significantly at 0.5 m. This lack of significant differences is most likely because this study was conducted in a mixed forest rather than monodominant stand which means that peat properties are likely to be influenced to a lesser extent by the previously reported gradient in nutrient availability and microbial communities (Sjo¨gersten et al. 2011 ; Cheesman et al. 2012 ; Troxler et al. 2012 ). Addition- ally, although individual plants were selected to minimise the presence of nearby understory and canopy vegetation, their influence on peat properties is likely to be limited but cannot be fully discounted. Aerobic decomposition of organic matter under low water table conditions may drive increases in pH through decarboxylation of organic anions, which involves protonation (Yan et al. 1996 ). Lower pH with increasing distance from the stems may therefore be associated with reduced decomposition rates, which is supported by increased organic matter content and C i carbon stocks. Previous studies have indicated that carbon inputs within the rooting zone can substantially increase decomposition, with species specific effects
3.4. Effects of permafrost thawing on regional carbon budgets
Under future warming climate conditions, the thawing permafrost could lead to both enhanced decomposition and plant growth. The sign and magnitude of net carbon balance depends on the relative intensity of stimulation on soil decomposition and plant growth. In this study, two sets of model simulations, with the permafrost-switch on/off, were conducted, and the effect of permafrost thawing on regional carbon budgets was calculated as the difference between these two sets of simulations. Our results indicated that, by excluding the permafrost-thawing effect, our no-policy simulations showed a 8% decrease and a 14% increase in the absolute magnitude of regional CH 4 source (figure 4 (a)) and CO 2 sink (figure 4 (b)) over the 21st century, respectively, which implied that soil decomposition will be more intensified due to thawing permafrost, resulting in a net decrease in ecosystem carbon storage. The net losses of CH 4 and CO 2 associated with permafrost thawing were estimated to about 0.6 Pg CH 4 and 7.5 Pg C over the century. Taken together, the net accumulated GHG sink were reduced by 41.5 Pg CO 2 -eq. over the century, which was almost twice as the accumulated GHG sink (−24.1 Pg CO 2 -eq.) simulated with a permafrost-thawing effect (figure 4 (c)). Thus, the comparison between the no-policy simulations with and without the permafrost-thawing effect suggested that the thawing permafrost resulted in a 63% decrease in accumulated GHG sink over the 21st century. Compared with the no-policy simulation, there were small differences in the estimated carbon and GHG budgets between policy simulations with and without a permafrost-thawing effect.
Natural decomposition of the constituent organic matter produces permanent material changes, including progressive destruction of constituent fibers, disappearance of physical structure/fabric, reduction in water-holding capacity, weakening of adsorption complex, gas generation and reduction in solids volume, which significantly alter the shear strength and compression properties and behavior of fibrous peat (O’Kelly and Pichan 2013, 2014; Pichan and O’Kelly 2013). Hence, an understanding of the relationship between degree of humification and engineering properties is vital from a geotechnical perspective. Comprehensive reviews of the effects of decomposition on the compressibility of fibrous peats are presented in the papers by Pichan and O’Kelly (2012) and O’Kelly and Pichan (2013). The final stage of the decomposition process involves the conversion of humic substances into gases, including carbondioxide and methane, or dissolved organic carbon as end- products, with the total gas void content of natural peat deposits generally ranging 5–10% (Hobbs 1986). These gases accumulate into bubbles, thereby generating a slight buoyancy effect for waterlogged peat material, before they are released from the peat mass to atmosphere through an ebullition process dependent upon ambient barometric pressures. The decomposition rate is generally extremely slow under normal subsurface conditions on account of the non-conducive environment (Pichan and O’Kelly 2013, O’Kelly and Pichan 2014). However, many peatlands are experiencing accelerated degradation due to the effects of large-scale drainage and oxidation, causing their subsidence. Numerous case studies report that the bulk of the subsidence for drained peatland is attributed to the decomposition of organics. For example, 55–80% of the subsidence that occurred for the Sacramento–San Joaquin Delta peat deposit, California, USA, was substantially caused by decomposition (Drexler et al. 2009). Beuving and van den Akker (1996) reported that in grassland on peat, almost 0·5m depth of peat layer is oxidized per 100 years. A similar subsidence rate (i.e. >150 mm over a 35-year monitoring period) reported for ombrotrophic parts of the Komosse Bog Complex, Sweden, was attributed to decomposition that occurred on account of changes in climate, hydrology and rate of nutrient supply (Franzen 2006). Subsidence may be exacerbated by underlying regional groundwater level changes.
are important in stabilizing SOM; leading to soil C depletion, especially in fields planted to annual crops characterized with low root production (Rutberg et al., 1996).
Studies have reported increased CH 4 oxidation in undisturbed forest and grassland soils compared to intensively cultivated fields (Goulding et al., 1996; MacDonald et al., 1996; Prieme and Christensen, 1999). In agreement with these studies, my results both from field (Chapters 3, 4 and 5) and modeling (Chapter 6) studies indicate that the incorporation of shelterbelts into cultivated fields significantly increased soil CH 4 oxidation, although this may be limited to the area occupied by trees. Results of the comparison of CH 4 fluxes (Chapter 3) showed that CH 4 oxidation was significantly greater in the shelterbelts (-0.66 kg CH 4 -C ha -1 yr -1 ) than in the adjacent cropped fields (-0.19 kg CH 4 -C ha -1 yr -1 ). The data on CH 4 fluxes at various distances from the shelterbelt to the cropped field showed similar trends. That is, the size of the CH 4 sink decreased with increasing distance from the center of the shelterbelt, where net cumulative CH 4 uptake was significantly (P < 0.10) greater within the shelterbelt (i.e. 0H; -1447 ± 484 g CH 4 -C ha -1 ) than in the transition zone (i.e. 0.2H at 0.5H; -752 ± 381 g CH 4 -C ha -1 ) and the cropped field (i.e. 1.5H and 5H; -19 ± 342 g CH 4 -C ha -1 ). The data also showed a strong linear relationship between soil CH 4 exchange and root biomass, bulk density and TOC, suggesting that management practices that affect soil properties such as soil moisture levels and gas diffusivity will also affect soil CH 4 exchange. Planted shelterbelts take up excess soil moisture, improve soil organic matter status and decrease soil bulk density, all of which create a favourable environment for methane consumption. In contrast, the lower CH 4 uptake observed within the cropped field relative to the shelterbelts may be related to lower SOC and root biomass and greater soil bulk density, which may have affected gas diffusivity at the cultivated soils. The continuous use of heavy farm machinery, fertilizer application and other agronomic practices within the cropped fields may have increased soil bulk density due to soil compaction, which in turn contributed to the low soil CH 4 oxidation in the cropped fields. Earlier studies have shown that agronomic practices such as tillage, fertilization and use of pesticides and herbicides have various degrees of inhibitory effects on CH 4 uptake in arable lands (Hansen et al., 1993; Arif et al., 1996; Mosier et al., 1997; Powlson et al., 1997; Topp and Pattey, 1997; Hütsch, 2001).
success of restoration can be judged. The statistical methods that will be used to analyse the data will influence data collection. These issues are discussed in more detail in the following section on Analysis and asssessment. Projects should also consider how the
Introduction: The Florida Everglades has undergone significant ecological change spanning the continuum of disturbance to restoration. While the restoration effort is not complete and the ecosystem continues to experience short duration perturbations, a better understanding of long-term C dynamics of the Everglades is needed to facilitate new restoration efforts. This study evaluated temporal trends of different aquatic carbon (C) pools of the northern Everglades Protection Area over a 20-year period to gauge historic C cycling patterns. Dissolved inorganic C (DIC), dissolved organic C (DOC), particulate organic C (POC), and surface water carbondioxide (pCO 2(aq) ) were
One of the functions of capping systems is to control the emission of gases into the atmosphere. Not only these gases are toxic for human health and the environment, but some of them like methane can be valued as a source of energy. However, most geomembrane types, such as LLDPE, offer only limited barrier performance against methane permeation. In addition, the characterization of gas permeation through geomembranes is currently being performed using 40 year old measurement methods mostly based on manometric or volumetric techniques. This has led to research and development efforts to improve the measurement of the gas permeability of geomembranes, which is a critical tool to allow the development of geomembranes with enhanced barrier properties against methane and carbondioxide.
than 1%) as more reactions are considered. As expected, when more reactions were included in the equilibrium calculation for multi-reaction process using MTE method, the results obtained tended to approach that using LUM method. Thus, the LUM method has been proven to be an effective method in predicting the thermodynamic equilibrium compositions for multi-reactions network processes including reforming of methane using carbondioxide process. Therefore, the LUM method was chosen to analyze the equilibrium compositions of the CORM process.
nutrient inputs from the Scheldt inner estuary. We hypothesize that in 2003 there was a stronger input of nutrients compared to the other years, while the input of organic matter was similar to other years. In the Scheldt inner estuary, the input of nutrients from diffuse sources are dependent on freshwater discharge, while organic matter comes mainly from point sources independently of freshwater discharge. This would lead to a stronger GPP in 2003 from the additional nutrient inputs, while alloch- tonous organic carbon inputs would sustain a similar level of heterotrophy as in the other years. We roughly evaluated the flux of dissolved inorganic nitrogen (FDIN) and of total phosphorous (FP tot ) from the Scheldt river to the Scheldt estuarine plume (Table 1). In the BCZ, Phaeo- cystis is overwhelming more important than diatoms in terms of phytoplanktonic biomass and GPP [e.g., [22,25- 28]], hence the computation of nutrient fluxes was not extended to silicate. FDIN values in 2003 were higher than in 2001 and 2004, while FP tot values in 2003 were higher than in 2002 and 2004 but similar to those of 2001. In the Scheldt estuarine plume, primary production during the spring phytoplankton bloom is strongly limited by P tot rather than by DIN [27,33]. Hence the higher FP tot values
In addition to methane, the natural gas from gas well is composed o f a very complex mixture o f different components such as carbondioxide, sulphur, water, nitrogen, mercury, hydrocarbons (light, heavy and aromatic) and other impurities. Carbondioxide removal from natural gas is o f significant importance and must be removed to avoid formation o f solids in cryogenic units and corrosion in steel pipes, and to avoid reduction in the heating value o f natural gas. The average proportion in gas wells is between 0.5-10 vol % and can be as high as 70 vol % in some wells. Thus, the removal o f CO 2 from crude natural gas during processing can be regarded as a key
The flux chamber was carefully positioned to maintain the natural processes that govern gas emission. The chamber was inserted 2.5 cm into the landfill cover soil to prevent environmental effects . The insertion process was performed in regions of predominantly smooth cover soil. A sharp knife was used to cut a part of the surface cover soil where rigid soil was located to facilitate flux chamber base insertion. Once the chamber was in place, the soil around the chamber walls was gently tamped with a density approximately equal to the surrounding soil  to prevent the escape of liberated gases. Four sequential gas samples were extracted from the chamber headspace into a 50 mL gas-tight syringe at predetermined intervals (5 min).
equipped with a tipping bucket, model 52293 (R. M. Young, USA) and a weighing gauge pluviometer (Ott, Germany) to measure rainfall, the HMP155A (Campbell Scientific Inc., USA) to measure air temperature and rela- tive humidity and the CNR4 net radiometer (Kipp & Zonen, Netherlands) to measure the incoming and out- going shortwave and longwave radiations. Furthermore, the CS616 soil moisture probes (Campbell Scientific Inc., USA) were employed to measure the volumetric soil moisture content, at the depth of 0.03 m at each site, while the TCAV thermal sensors (Campbell Scientific Inc., USA), and the HFP01SC self-calibrating heat flux plates (Hukseflux, Netherlands) were used to measure soil temperature at three different depths (0.03, 0.10, and 0.30 m) and soil heat fluxes at 0.08 m respectively. Also in- stalled were MX-Q24M-Sec-D11 web cameras (Mobotix, Germany) to take daily pictures from the surrounding areas for studying the vegetation phenology. In addition, the multi-sensor WXT 520 (Vaisala, Finland) was installed to measure rainfall, air temperature, horizontal wind speed and direction, relative humidity and air pressure. Data from each station were automated and recorded onto the CR3000 and CR1000 data loggers (Campbell Scientific Inc., USA). Two solar panels were built at each station for the power supply of the EC stations and the data transmission unit for an automatic transfer of the measurements on the daily basis.
120. Lee, H.V., Juan, J.C., Abdullah, N.F.B., and Taufiq-Yap, Y.H., Heterogeneous base catalysts for edible palm and non-edible Jatropha-based biodiesel production. Chemistry Central Journal, 2014. 8(1): 30.
121. Kalijadis, A.M., Vukčević, M.M., Jovanović, Z.M., Laušević, Z.V., and Laušević, M.D., Characterization of surface oxygen groups on different carbon materials by the Boehm method and temperature programmed desorption. Journal of the Serbian Chemical Society, 2011. 76(5): 757-768. 122. Mao, D., Yang, W., Xia, J., Zhang, B., Song, Q., and Chen, Q., Highly
these uncertainties to calculate fractional standard devi- ations (equal to the coefficient of variation, the standard deviation divided by the mean value) for each per-ani- mal carbon flux quantity in each global region. However, when combining uncertainties across livestock types within a nation or from multiple nations to the regional or global level, the uncertainties were simply added (not in quadrature), because these estimates are not inde- pendent —i.e. the livestock in all nations within a region share the same carbon flux estimates, emissions coefficients, and uncertainties, and all livestock within a nation share many regional attributes. Using the arith- metic sum, as opposed to adding in quadrature, results in larger uncertainties, which may be considered more conservative.
To solve Eq. (4) for temperature one needs to specify top and bottom boundary conditions as well as a method for the calculation of marginal heat flux, F tz,b (z), at each depth z. The top boundary condition is a well-established heat bal- ance equation, involving net radiation and a scheme for tur- bulent heat fluxes in a surface atmospheric layer based on Monin–Obukhov similarity theory (Paulson, 1970; Businger et al., 1971; Beljaars and Holtslag, 1991). The way of cou- pling the water column to bottom sediments through a lower boundary condition and marginal heat flux is less straightfor- ward. When the heat transfer in bottom sediments is solved by a diffusion-type equation, there are two options for impos- ing boundary conditions at the “water–sediments” interface: – continuity of both heat flux and temperature at the inter-
The aim of this study was to investigate the reforming of methane with carbondioxide under microwave condi- tions. Catalysts of platinum supported on -alumina at several loading levels with different promoters were examined. The effects of temperature, feed gas composi- tions and heating methods were investigated. The reaction was also carried out with conventional heating for comparative purposes.