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1.
The uncertainty associated with the Austrian Greenhouse Gas emission inventory has been determined for the gases CO 2, CH 4 and N 2O and for the overall greenhouse potential. Expert interviews were conducted to obtain uncertainties in inventory input data. Based on these interviews, error distributions were developed and combined using Monte-Carlo analysis. Results for all sources and gases combined indicate an overall uncertainty between 10.5% and 12% depending on the base year considered. Excluding emissions and the uncertainty associated with forest sinks and natural sources, overall uncertainty decreased by 2% points. The mere ‘random error’, which is considered the level of uncertainty to be achieved with the current methodology (excluding all systematic errors) is 5% points lower. Detailed evaluation shows that much of the overall uncertainty derives from a lack of understanding the processes associated with N 2O emissions from soils. Other important contributors to GHG emission uncertainties are CH 4 from landfills and forests as CO 2 sinks. The uncertainty of the trend has been determined at near 5% points, with solid waste production (landfills) having the strongest contribution. Theoretical considerations do not permit a decrease of the trend uncertainty—even when forest sinks are not considered—below 3% points. 相似文献
2.
The open lots and manure stockpiles of dairy farm are major sources of greenhouse gas (GHG) emissions in typical dairy cow housing and manure management system in China. GHG (CO 2, CH 4 and N 2O) emissions from the ground level of brick-paved open lots and uncovered manure stockpiles were estimated according to the field measurements of a typical dairy farm in Beijing by closed chambers in four consecutive seasons. Location variation and manure removal strategy impacts were assessed on GHG emissions from the open lots. Estimated CO 2, CH 4 and N 2O emissions from the ground level of the open lots were 137.5±64.7 kg hd -1 yr -1, 0.45±0.21 kg hd -1 yr -1 and 0.13±0.08 kg hd -1 yr -1, respectively. There were remarkable location variations of GHG emissions from different zones (cubicle zone vs. aisle zone) of the open lot. However, the emissions from the whole open lot were less affected by the locations. After manure removal, lower CH 4 but higher N 2O emitted from the open lot. Estimated CO 2, CH 4 and N 2O emissions from stockpile with a stacking height of 55±12 cm were 858.9±375.8 kg hd -1 yr -1, 8.5±5.4 kg hd -1 yr -1 and 2.3±1.1 kg hd -1 yr -1, respectively. In situ storage duration, which estimated by manure volatile solid contents (VS), would affect GHG emissions from stockpiles. Much higher N 2O was emitted from stockpiles in summer due to longer manure storage. Implications: This study deals with greenhouse gas (GHG) emissions from open lots and stockpiles. It’s an increasing area of concern in some livestock producing countries. The Intergovernmental Panel on Climate Change (IPCC) methodology is commonly used for estimation of national GHG emission inventories. There is a shortage of on-farm information to evaluate the accuracy of these equations and default emission factors. This work provides valuable information for improving accounting practices within China or for similar manure management practice in other countries. 相似文献
3.
In this paper the authors have estimated for 1990 and 1995 the inventory of greenhouse gases CO 2, CH 4 and N 2O for India at a national and sub-regional district level. The district level estimates are important for improving the national inventories as well as for developing sound mitigation strategies at manageable smaller scales. Our estimates indicate that the total CO 2, CH 4 and N 2O emissions from India were 592.5, 17, 0.2 and 778, 18, 0.3 Tg in 1990 and 1995, respectively. The compounded annual growth rate (CAGR) of these gases over this period were 6.3, 1.2 and 3.3%, respectively. The districts have been ranked according to their order of emissions and the relatively large emitters are termed as hotspots. A direct correlation between coal consumption and districts with high CO 2 emission was observed. CO 2 emission from the largest 10% emitters increased by 8.1% in 1995 with respect to 1990 and emissions from rest of the districts decreased over the same period, thereby indicating a skewed primary energy consumption pattern for the country. Livestock followed by rice cultivation were the dominant CH 4 emitting sources. The waste sector though a large CH 4 emitter in the developed countries, only contributed about 10% the total CH 4 emission from all sources as most of the waste generated in India is allowed to decompose aerobically. N 2O emissions from the use of nitrogen fertilizer were maximum in both the years (more than 60% of the total N 2O). High emission intensities, in terms of CO 2 equivalent, are in districts of Gangetic plains, delta areas, and the southern part of the country. These overlap with districts with large coal mines, mega power plants, intensive paddy cultivation and high fertilizer use. The study indicates that the 25 highest emitting districts account for more than 37% of all India CO 2 equivalent GHG emissions. Electric power generation has emerged as the dominant source of GHG emissions, followed by emissions from steel and cement plants. It is therefore suggested, to target for GHG mitigation, the 40 largest coal-based thermal plants, five largest steel plants and 15 largest cement plants in India as the first step. 相似文献
4.
In this research, in order to develop technology/country-specific emission factors of methane (CH 4) and nitrous oxide (N 2O), a total of 585 samples from eight gas-fired turbine combined cycle (GTCC) power plants were measured and analyzed. The research found that the emission factor for CH 4 stood at “0.82 kg/TJ”, which was an 18 % lower than the emission factor for liquefied natural gas (LNG) GTCC “1 kg/TJ” presented by Intergovernmental Panel on Climate Change (IPCC). The result was 8 % up when compared with the emission factor of Japan which stands at “0.75 kg/TJ”. The emission factor for N 2O was “0.65 kg/TJ”, which is significantly lower than “3 kg/TJ” of the emission factor for LNG GTCC presented by IPCC, but over six times higher than the default N 2O emission factor of LNG. The evaluation of uncertainty was conducted based on the estimated non-CO 2 emission factors, and the ranges of uncertainty for CH 4 and N 2O were between ?12.96 and +13.89 %, and ?11.43 and +12.86 %, respectively, which is significantly lower than uncertainties presented by IPCC. These differences proved that non-CO 2 emissions can change depending on combustion technologies; therefore, it is vital to establish country/technology-specific emission factors. 相似文献
5.
To assess the effects of nitrogen (N) deposition on greenhouse gas (GHG) fluxes in alpine grassland of the Tianshan Mountains in central Asia, CH 4, CO 2 and N 2O fluxes were measured from June 2010 to May 2011. Nitrogen deposition tended to significantly increase CH 4 uptake, CO 2 and N 2O emissions at sites receiving N addition compared with those at site without N addition during the growing season, but no significant differences were found for all sites outside the growing season. Air temperature, soil temperature and water content were the important factors that influence CO 2 and N 2O emissions at year-round scale, indicating that increased temperature and precipitation in the future will exert greater impacts on CO 2 and N 2O emissions in the alpine grassland. In addition, plant coverage in July was also positively correlated with CO 2 and N 2O emissions under elevated N deposition rates. The present study will deepen our understanding of N deposition impacts on GHG balance in the alpine grassland ecosystem, and help us assess the global N effects, parameterize Earth System models and inform decision makers. 相似文献
6.
Manure-based soil amendments (herein “amendments”) are important fertility sources, but differences among amendment types and management can significantly affect their nutrient value and environmental impacts. A 6-month in situ decomposition experiment was conducted to determine how protection from wintertime rainfall affected nutrient losses and greenhouse gas (GHG) emissions in poultry (broiler chicken and turkey) and horse amendments. Changes in total nutrient concentration were measured every 3 months, changes in ammonium (NH 4+) and nitrate (NO 3?) concentrations every month, and GHG emissions of carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O) every 7–14 days. Poultry amendments maintained higher nutrient concentrations (except for K), higher emissions of CO 2 and N 2O, and lower CH 4 emissions than horse amendments. Exposing amendments to rainfall increased total N and NH 4+ losses in poultry amendments, P losses in turkey and horse amendments, and K losses and cumulative N 2O emissions for all amendments. However, it did not affect CO 2 or CH 4 emissions. Overall, rainfall exposure would decrease total N inputs by 37% (horse), 59% (broiler chicken), or 74% (turkey) for a given application rate (wet weight basis) after 6 months of decomposition, with similar losses for NH 4+ (69–96%), P (41–73%), and K (91–97%). This study confirms the benefits of facilities protected from rainfall to reduce nutrient losses and GHG emissions during amendment decomposition. Implications: The impact of rainfall protection on nutrient losses and GHG emissions was monitored during the decomposition of broiler chicken, turkey, and horse manure-based soil amendments. Amendments exposed to rainfall had large ammonium and potassium losses, resulting in a 37–74% decrease in N inputs when compared with amendments protected from rainfall. Nitrous oxide emissions were also higher with rainfall exposure, although it had no effect on carbon dioxide and methane emissions. Overall, this work highlights the benefits of rainfall protection during amendment decomposition to reduce nutrient losses and GHG emissions. 相似文献
7.
High-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH 4 retention, 99.8% (CH 4 mean flux of 12 mg C m -2 h -1) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m -2 h -1) of the same landfill age. Fresh waste at the working face emitted a large fraction of N 2O, with average fluxes of 10 mg N m -2 h -2, while N 2O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH 4 emissions were elevated under high air temperatures but decreased as landfill age increased. N 2O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO 2 was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr -1 in CO 2 equivalents for the landfill site, of which the OWC-covered section contributed the most CH 4 (41.9%), while the working face contributed the most N 2O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control. Implications: Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N2O, which should draw attention. High CH4 fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH4 retention, and therefore is a recommended cover material for GHG control. 相似文献
8.
Agriculture is an important source of NH 3, which contributes to acidification and eutrophication, as well as emissions of the greenhouse gases CH 4 and N 2O. Because of their common sources, emission reduction measures for one of these gases may affect emissions of others. These interrelations are often ignored in policy making. This study presents an analysis of the effects of measures to reduce NH 3 emissions on emissions of N 2O and CH 4 from agriculture in Europe. The analysis combines information from the NH 3 module of the Regional Air pollution INformation and Simulation (RAINS) model for Europe with the IPCC method for national greenhouse gas inventories. The IPCC method for estimating agricultural emissions of N 2O and CH 4 is adjusted in order to use it in combination with the RAINS database for the European agricultural sector. As an example, we applied the adjusted method to the agricultural sector in the Netherlands and found that application of several NH 3 abatement options may result in a substantial increase in N 2O emissions while the effect on CH 4 emissions is relatively small. In Part 2 of this paper we focus on the resulting emissions for all European countries for 1990 and 2010. 相似文献
9.
Agriculture is an important source of NH 3, which contributes to acidification and eutrophication, as well as emissions of the greenhouse gases CH 4 and N 2O. Because of their common sources, emission reduction measures for one of these gases may affect emissions of others. These interrelations are often ignored in policy making. This study presents an analysis of the effects of measures to reduce NH 3 emissions on emissions of N 2O and CH 4 from agriculture in Europe. The analysis combines information from the NH 3 module of the Regional Air pollution INformation and Simulation (RAINS) model for Europe with the IPCC method for national greenhouse gas inventories. The IPCC method for estimating agricultural emissions of N 2O and CH 4 is adjusted in order to use it in combination with the RAINS database for the European agricultural sector. As an example, we applied the adjusted method to the agricultural sector in the Netherlands and found that application of several NH 3 abatement options may result in a substantial increase in N 2O emissions while the effect on CH 4 emissions is relatively small. In Part 2 of this paper we focus on the resulting emissions for all European countries for 1990 and 2010. 相似文献
10.
Patches of dung and urine are major contributors to the feedlot gas emissions. This study investigated the impacts of dung deposition frequency (partly reflecting animal stocking density of a feedlot), dairy feedlot floor conditions (old floor indicated with the presence of consolidated manure pad [CMP] vs. new floor with the absence of consolidated manure pad [CMPn]), and application of dicyandiamide (DCD) and hydroquinone (HQ) on nitrous oxide (N 2O) and methane (CH 4) emissions from patches in the laboratory, and the integrative impacts were expressed in terms of global warming potential (CO 2-equivalent). Dung deposition frequency, feedlot floor condition, and application of inhibitors showed inverse impacts on N 2O and CH 4 emissions from patches. Greenhouse gas (GHG) emissions from the dung, urine, and dung+urine patches on the CMP feedlot surface were approximately 7.48, 87.35, and 7.10 times those on the CMPn feedlot surface ( P < 0.05). Meanwhile, GHG emissions from CMP and CMPn feedlot surfaces under high deposition frequency condition were approximately 10 and 1.7 times those under low-frequency condition. Moreover, application of HQ slightly reduced the GHG emission from urine patches, by 14.9% ( P > 0.05), while applying DCD or DCD+HQ significantly reduced the GHG, by 60.3% and 65.0%, respectively ( P < 0.05). Overall, it is necessary to include feedlot management such as animal stocking density and feedlot floor condition to the process of determining emission factors for feedlots. In the future, field measurements to quantitatively evaluate the relative contribution of nitrification and denitrification to the N 2O emissions of feedlot surfaces are highly required for effective N 2O control. Implications: This study shows that feedlot CH4 and N2O emissions inversely respond to the dicyandiamide (DCD) application. Applying DCD significantly reduces GHG emissions of feedlot urine patches. Feedlot floor condition and stocking density strongly impact feedlot GHG emissions. Including feedlot floor condition and stocking density in the feedlot EF determining process is necessary. 相似文献
11.
针对我国现在主流的城市污水污泥处置方法:填埋,焚烧,堆肥。用IPCC中推荐的方法和缺省值,对处置过程中产生的温室气体的直接排放、间接排放和替代排放做了计算和分析。填埋过程计算排放的温室气体有CH4,焚烧过程计算排放的有温室气体CO2和N2O,堆肥过程计算的排放的有温室气体CO2和N2O,最终比较的结果都折算成CO2的排放。结果表明,污泥填埋、焚烧、堆肥所产生的CO2的净排放量分别为695.847 kg CO2/t、443.643 kg CO2/t、511.817 kgCO2/t。由于考虑了堆肥以后的有机肥利用,从减排以及污泥资源化的角度分析,得出堆肥是相对好的污泥处置方式。 相似文献
12.
In coastal Antarctica, freezing and thawing influence many physical, chemical and biological processes for ice-free tundra ecosystems, including the production of greenhouse gases (GHGs). In this study, penguin guanos and ornithogenic soil cores were collected from four penguin colonies and one seal colony in coastal Antarctica, and experimentally subjected to three freezing–thawing cycles (FTCs) under ambient air and under N 2. We investigated the effects of FTCs on the emissions of three GHGs including nitrous oxide (N 2O), carbon dioxide (CO 2) and methane (CH 4). The GHG emission rates were extremely low in frozen penguin guanos or ornithogenic soils. However, there was a fast increase in the emission rates of three GHGs following thawing. During FTCs, cumulative N 2O emissions from ornithogenic soils were greatly higher than those from penguin guanos under ambient air or under N 2. The highest N 2O cumulative emission of 138.24 μg N 2O–N kg ?1 was observed from seal colony soils. Cumulative CO 2 and CH 4 emissions from penguin guanos were one to three orders of magnitude higher than those from ornithogenic soils. The highest cumulative CO 2 (433.0 mgCO 2–C kg ?1) and CH 4 (2.9 mgCH 4–C kg ?1) emissions occurred in emperor penguin guanos. Penguin guano was a stronger emitter for CH 4 and CO 2 while ornithogenic soil was a stronger emitter for N 2O during FTCs. CO 2 and CH 4 fluxes had a correlation with total organic carbon (TOC) and soil/guano moisture (M c) in penguin guanos and ornithogenic soils. The specific CO 2–C production rate (CO 2–C/TOC) indicated that the bioavailability of TOC was markedly larger in penguin guanos than in ornithogenic soils during FTCs. This study showed that FTC-released organic C and N from sea animal excreta may play a significant role in FTC-related GHG emissions, which may account for a large proportion of annual fluxes from tundra ecosystems in coastal Antarctica. 相似文献
13.
Greenhouse gas (GHG) emissions by constructed wetlands (CWs) could mitigate the environmental benefits of nutrient removal in these man-made ecosystems. We studied the effect of 3 different macrophyte species and artificial aeration on the rates of nitrous oxide (N 2O), carbon dioxide (CO 2) and methane (CH 4) production in CW mesocosms over three seasons. CW emitted 2-10 times more GHG than natural wetlands. Overall, CH 4 was the most important GHG emitted in unplanted treatments. Oxygen availability through artificial aeration reduced CH 4 fluxes. Plant presence also decreased CH 4 fluxes but favoured CO 2 production. Nitrous oxide had a minor contribution to global warming potential (GWP < 15%). The introduction of oxygen through artificial aeration combined with plant presence, particularly Typha angustifolia, had the overall best performance among the treatments tested in this study, including lowest GWP, greatest nutrient removal, and best hydraulic properties. 相似文献
14.
Great efforts have been devoted to assessing the effects of straw managements on greenhouse gas (GHG) emissions, global warming potential (GWP), and net economic budget in rice monoculture (RM). However, few studies have evaluated the effects of straw managements on GHG emissions and net ecosystem economic budget (NEEB) in integrated rice-crayfish farming (RC). Here, a randomized block field experiment was performed to comprehensively evaluate the effects of aquatic breeding practices (feeding or no feeding of forage) and straw managements (rice straw returning or removal) on soil NH4+–N and NO?3–N contents, redox potential (Eh), CH4 and N2O emissions, GWP, and NEEB of fluvo-aquic paddy soil in a rice-crayfish co-culture system in Jianghan Plain of China. We also compared the differences in CH4 and N2O emissions, GWP, and NEEB between RM and RC. Straw returning significantly increased CH4 and N2O emissions by 34.9–46.1% and 6.2–23.1% respectively compared with straw removal. Feeding of forage decreased CH4 emissions by 13.9–18.7% but enhanced N2O emissions by 24.4–33.2% relative to no feeding. Compared with RM treatment, RC treatment decreased CH4 emissions by 18.1–19.6% but increased N2O emissions by 16.8–21.0%. Moreover, RC treatment decreased GWP by 16.8–22.0% while increased NEEB by 26.9–75.6% relative to RM treatment, suggesting that the RC model may be a promising option for mitigating GWP and increasing economic benefits of paddy fields. However, the RC model resulted in a lower grain yield compared with the RM model, indicating that more efforts are needed to simultaneously increase grain yield and NEEB and decrease GWP under RC model. 相似文献
15.
Intensive beef production has increased during recent decades in Brazil and may substantially increase both methane (CH 4) and nitrous oxide (N 2O) emissions from manure management. However, the quantification of these gases and methods for extrapolating them are scarce in Brazil. A case study examines CH 4 and N 2O emissions from one typical beef cattle feedlot manure management continuum in Brazil and the applicability of Manure-DNDC model in predicting these emissions for better understand fluxes and mitigation options. Measurements track CH 4 and N 2O emissions from manure excreted in one housing floor holding 21 animals for 78 days, stockpiled for 73 days and field spread (360 kg N ha ?1). We found total emissions (CH 4 + N 2O) of 0.19 ± 0.10 kg CO 2eq per kg of animal live weight gain; mostly coming from field application (73%), followed housing (25%) and storage (2%). The Manure-DNDC simulations were generally within the statistical deviation ranges of the field data, differing in ?28% in total emission. Large uncertainties in measurements showed the model was more accurate estimating the magnitude of gases emissions than replicate results at daily basis. Modeled results suggested increasing the frequency of manure removal from housing, splitting the field application and adopting no-tillage system is the most efficient management for reducing emissions from manure (up to about 75%). Since this work consists in the first assessment under Brazilian conditions, more and continuous field measurements are required for decreasing uncertainties and improving model validations. However, this paper reports promising results and scientific perceptions for the design of further integrated work on farm-scale measurements and Manure-DNDC model development for Brazilian conditions. 相似文献
16.
Measuring greenhouse gas (GHG) source emissions provides data for validation of GHG inventories, which provide the foundation for climate change mitigation. Two Toyota RAV4 electric vehicles were outfitted with high-precision instrumentation to determine spatial and temporal resolution of GHGs (e.g., nitrous oxide, methane [CH 4], and carbon dioxide [CO 2]), and other gaseous species and particulate metrics found near emission sources. Mobile measurement platform (MMP) analytical performance was determined over relevant measurement time scales. Pollutant residence times through the sampling configuration were measured, ranging from 3 to 11 sec, enabling proper time alignment for spatial measurement of each respective analyte. Linear response range for GHG analytes was assessed across expected mixing ratio ranges, showing minimal regression and standard error differences between 5, 10, 30, and 60 sec sampling intervals and negligible differences between the two MMPs. GHG instrument drift shows deviation of less than 0.8% over a 24-hr measurement period. These MMPs were utilized in tracer-dilution experiments at a California landfill and natural gas compressor station (NGCS) to quantify CH 4 emissions. Replicate landfill measurements during October 2009 yielded annual CH 4 emissions estimates of 0.10 ± 0.01, 0.11 ± 0.01, and 0.12 ± 0.02 million tonnes of CO 2 equivalent (MTCO 2E). These values compare favorably to California GHG Emissions Inventory figures for 2007, 2008, and 2009 of 0.123, 0.125, and 0.126 MTCO 2E/yr, respectively, for this facility. Measurements to quantify NGCS boosting facility-wide emissions, during June 2010 yielded an equivalent of 5400 ± 100 TCO 2E/yr under steady-state operation. However, measurements during condensate transfer without operational vapor recovery yield an instantaneous emission rate of 2–4 times greater, but was estimated to only add 12 TCO 2E/yr overall. This work displays the utility for mobile GHG measurements to validate existing measurement and modeling approaches, so emission inventory values can be confirmed and associated uncertainties reduced.Implications:? Measuring greenhouse gas (GHG) source emissions provides data and validation for GHG inventories, the foundation for climate change mitigation. Mobile measurement platforms with robust analytical instrumentation completed tracer-dilution experiments in California at a landfill and natural gas compressor station (NGCS) to quantify CH4 emissions. Data collected for landfill CH4 agree with the current California emissions inventory, while NGCS data show the possible variability from this type of facility. This work displays the utility of mobile GHG measurements to validate existing measurement and modeling approaches, such that emission inventory values can be confirmed, associated uncertainties reduced, and mitigation efforts quantified. 相似文献
17.
A decentralized emission inventories are prepared for road transport sector of India in order to design and implement suitable technologies and policies for appropriate mitigation measures. Globalization and liberalization policies of the government in 90's have increased the number of road vehicles nearly 92.6% from 1980–1981 to 2003–2004. These vehicles mainly consume non-renewable fossil fuels, and are a major contributor of green house gases, particularly CO 2 emission. This paper focuses on the statewise road transport emissions (CO 2, CH 4, CO, NO x, N 2O, SO 2, PM and HC), using region specific mass emission factors for each type of vehicles. The country level emissions (CO 2, CH 4, CO, NO x, N 2O, SO 2 and NMVOC) are calculated for railways, shipping and airway, based on fuel types. In India, transport sector emits an estimated 258.10 Tg of CO 2, of which 94.5% was contributed by road transport (2003–2004). Among all the states and Union Territories, Maharashtra's contribution is the largest, 28.85 Tg (11.8%) of CO 2, followed by Tamil Nadu 26.41 Tg (10.8%), Gujarat 23.31 Tg (9.6%), Uttar Pradesh 17.42 Tg (7.1%), Rajasthan 15.17 Tg (6.22%) and, Karnataka 15.09 Tg (6.19%). These six states account for 51.8% of the CO 2 emissions from road transport. 相似文献
18.
Introduction Korea has been making efforts to reduce greenhouse gas (GHG) emissions, including a voluntary commitment to the target of a 30% reduction, based on business-as-usual of the total GHG emission volume, by 2020; 2006 IPCC Guidelines provided default values, applying country-specific emission factors was recommended when estimating national greenhouse gas emissions. Results and discussion This study focused on anthracite produced in Korea in order to provide basic data for developing country-specific emission factor. This study has estimated CO 2 emission factors to use worksheet of which five steps consisted according to the fuel analysis method. Conclusion As a result, the average of net colorific value for 3 years (2007??2009) was 4,519 kcal/kg, and the CO 2 emission factor was calculated to be 111,446 kg/TJ, which is about 11.8% lower than the 2006 IPCC guidelines default value, and about 7.9% higher than the US EPA emission factor. 相似文献
19.
Chamber techniques can easily be applied to field trials with multiple small plots measuring carbon- and nitrogen-trace gas fluxes. Nevertheless, such chamber measurements are usually made weekly and rarely more frequently than once daily. However, automatic chambers do allow flux measurements on sub-daily time scales. It has been hypothesized that sub-daily measurements provide more reliable results, as diurnal variations are captured better compared to manual measurements. To test this hypothesis we compared automatic and manual measurements of N 2O, CO 2 and CH 4 fluxes from tilled and non-tilled plots of a rice–wheat rotation ecosystem over a non-waterlogged period. Our results suggest that both techniques, i.e., either manual or automatic chambers of N 2O and CO 2 emissions resulted in biased fluxes. The manual measurements were adequate to capture either day-to-day or seasonal dynamics of N 2O, CO 2 and CH 4 exchanges, but overestimated the cumulative N 2O and CO 2 emissions by 18% and 31%, respectively. This was due to neglecting temperature-dependent diurnal variations of C and N trace gas fluxes. However, the automatic measurements underestimated the cumulative emissions of N 2O and CO 2 by 22% and 17%, respectively. This underestimation resulted from chamber effects upon soil moisture during rainfall processes. No significant difference was detected between the two methods in CH 4 exchanges over the non-waterlogged soils. The bias of manual chambers may be significant when pronounced diurnal variations occur. The bias of automatic measurements can only be avoided/minimized if chamber positions are frequently changed and/or if chambers are automatically opened during rainfall events. We therefore recommend using automatic chambers together with continuous measurements of soil chamber moisture to allow for soil moisture correction of fluxes or to correct flux estimates as derived by manual chambers for possible diurnal variations. 相似文献
20.
Water management is one of the most important practices that affect methane (CH 4) and nitrous oxide (N 2O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH 4 and N 2O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH 4 and N 2O emissions from paddy fields were very clear. The peaks of CH 4 emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH 4 emission was observed in a short period after re-flooding. N 2O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N 2O emissions, whereas no substantial N 2O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH 4 emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N 2O emissions were increased by 135.4% on the average. The integrative global warming potential of CH 4 and N 2O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH 4 and N 2O emissions from paddy fields while ensuring the rice yield. 相似文献
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