Grazing management significantly influences greenhouse gas(GHG)emissions and the global warming potential(GWP)in grasslands.Yet,a limited understanding of the impact of grazing and grazing exclusion on GHG emis-sions ...Grazing management significantly influences greenhouse gas(GHG)emissions and the global warming potential(GWP)in grasslands.Yet,a limited understanding of the impact of grazing and grazing exclusion on GHG emis-sions and GWP in grasslands hinders progress towards grassland ecosystem sustainability and GHG mitigation.We conducted a global meta-analysis of 75 published studies to investigate the effects of grazing and grazing exclusion on methane(CH_(4)),carbon dioxide(CO_(2)),nitrous oxide(N_(2 )O),and GWP.Our results revealed that grazing and grazing exclusion significantly increased the CO_(2) and CH4 emissions,respectively.The responses of GHG emissions and GWP to grazing were regulated by grazing intensity and elevation.We also found that light grazing significantly decreased GWP but heavy grazing increased GWP.Reducing grazing intensity was a simple and effective method through stocking rate adjustment,which promised a large GHG mitigation poten-tial.Our results demonstrated that GHG emissions increased with elevation under grassland grazing,implying that irrational grazing in high-elevation grasslands promoted GHG emissions.In comparison with grazing,only long-term grazing exclusion reduced the GWP,and CH4 emissions enhanced with grazing exclusion duration.However,long-term grazing exclusion may shift economic demand and grazing burden to other areas.Overall,we suggested that regulating the grazing intensity,rather than grazing exclusion,was an effective way to re-duce GHG emissions.Our study contributed to the enhancement of sustainable grazing management practices for GHG balance and GWP in global grasslands,and offered a global picture for understanding the changes in GHG emissions and GWP under different grazing management regimes.展开更多
Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate...Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.展开更多
The significant increase in the demand for biomass waste treatment after garbage classification has led to housefly larvae treatment becoming an attractive treatment option.It can provide a source of protein while tre...The significant increase in the demand for biomass waste treatment after garbage classification has led to housefly larvae treatment becoming an attractive treatment option.It can provide a source of protein while treating biomass waste,which means that nutrients can be returned to the natural food chain.However,the performance of this technology in terms of its environmental impacts is still unclear,particularly with regards to global warming potential(GWP).This study used a life cycle assessment(LCA)approach to assess a housefly larvae treatment plant with a treatment capacity of 50 tons of biomass waste per day.The LCA results showed that the 95% confidence intervals for the GWP in summer and winter were determined to be 24.46-32.81 kg CO_(2) equivalent(CO_(2)-eq)/ton biomass waste and5.37-10.08 kg CO_(2)-eq/ton biomass waste,respectively.The greater GWP value in summer is due to the longer ventilation time and higher ventilation intensity in summer,which consumes more power.The main GWP contributions are from(1)electricity needs(accounting for 78.6% of emissions in summer and 70.2%in winter)and(2)product substitution by mature housefly larvae and compost(both summer and winter accounting for 96.8% of carbon reduction).展开更多
Perfluorocarbon gas is widely used in the semiconductor industry.However,perfluorocarbon has a negative effect on the global environment owing to its high global warming potential(GWP) value.An alternative solution is...Perfluorocarbon gas is widely used in the semiconductor industry.However,perfluorocarbon has a negative effect on the global environment owing to its high global warming potential(GWP) value.An alternative solution is essential.Therefore,we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF_3 with C_6F_(12)O,which has a low GWP and is in a liquid state at room temperature.In this study,silicon oxynitride(SiON) films were plasma-etched using inductively coupled CF4+C_6F_(12)O+O_2 mixed plasmas.Subsequently,the etching characteristics of the film,such as etching rate,etching profile,selectivity over Si,and photoresist,were investigated.A double Langmuir probe was used and optical emission spectroscopy was performed for plasma diagnostics.In addition,a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film surface.Consequently,the etching characteristics of the C_6F_(12)O mixed plasma exhibited a lower etching rate,higher SiON/Si selectivity,lower plasma damage,and more vertical etched profiles than the conventional CHF_3 mixed plasma.In addition,the C_6F_(12)O gas can be recovered in the liquid state,thereby decreasing global warming.These results confirmed that the C_6F_(12)O precursor can sufficiently replace the conventional etching gas.展开更多
We developed two radiation parameterizations with different resolutions （17-band and 998-band） for perfluorocarbons （PFCs） and sulfur hexafluoride （SF6） using the updated High-resolution Transmission Molecular A...We developed two radiation parameterizations with different resolutions （17-band and 998-band） for perfluorocarbons （PFCs） and sulfur hexafluoride （SF6） using the updated High-resolution Transmission Molecular Absorption （HITRAN） 2004 database and the correlated k-distribution method. We analyzed the impacts of the two radiation schemes on heating rates. Then we studied their instantaneous radiative efficiency, stratospheric adjusted radiative efficiency, global warming potential （GWP）, and global temperature potential （GTP）, for both clear- and all-sky conditions using a high-resolution radiation scheme. We found that the stratosphere-adjusted radiative efficiencies of C2F6, CF4, and SF6 for the whole sky were 0.346, 0.098, and 0.680 W m^-2 ppbv^-1, respectively. Radiative forcing from the industrial revolution to 2005 was 0.001, 0.007, and 0.004 W m^-2, respectively; and was predicted to rise to 0.008, 0.036, and 0.037 W m^-2, respectively, by 2100, according to emission scenarios provided by the IPCC. The GWPs of C2F6, CF4, and SF6 are 17035, 7597, and 31298, respectively, for a time horizon of 100 years relative to CO2. Their GTPs of pulse and sustained emissions, GTPv and GTPs, are 22468, 10052, and 40935 and 16498, 7355, and 30341, respectively, for a 100-year time horizon.展开更多
This paper presents a theoretical method to calculate the minimum inerting concentration(MIC)of binary and ternary blends(refrigerants)that are used in small refrigeration systems.MIC is the concentration of the dilut...This paper presents a theoretical method to calculate the minimum inerting concentration(MIC)of binary and ternary blends(refrigerants)that are used in small refrigeration systems.MIC is the concentration of the dilutant which makes the flammable mixture into just non-flammable(at non-zero quenching potential).In this study,the refrigerant safety parameters such as flammability,Global Warming Potential(GWP)and performance(COP)are analyzed for twelve binary and thirteen ternary blends containing one flammable and two nonflammable(dilutant)components.Flammability investigation was carried out with the hydrocarbon refrigerants R290,R600,R600a each mixed with dilutants R227ea,R125,R245fa,R13I1 and R134a at different concentrations respectively.Two methods,thermal balance method(TBM)and modified thermal balanced method(MTBM),are used to estimate the MIC(which decides the flammable zone).Thirteen ternary blends were identified based on the MIC values estimated using MTBM.In the case of ternary blends,it was observed that the non-flammable zone is high for the compositions of the Mixture G,Mixture H and Mixture I.It was also estimated that the COPs of the proposed mixtures M22,M24,M25 and M27 are 4%greater than the COP of R134a(for the same operating conditions).Further,it was also understood that the corresponding GWP value is reduced by 90%to 97%for the mixtures(M21,M22,M24,M25 and M27)when compared to R134a(GWP=1300).Therefore,out of the thirteen proposed ternary mixtures(M15 to M27),the mixtures(M21,M22,M24,M25 and M27)are safe in terms of flammability,GWP and possess reasonable COP which can be a potential alternative refrigerant mixture to R134a in small refrigeration systems.展开更多
Due to the large amount of greenhouse gas(GHG)emissions and the high dependence on fossil energy,the aviation industry has attracted a lot of attention for emission reduction and sustainable development.Biomass is a g...Due to the large amount of greenhouse gas(GHG)emissions and the high dependence on fossil energy,the aviation industry has attracted a lot of attention for emission reduction and sustainable development.Biomass is a green and sustainable renewable resource,and its chemical conversion to produce bio-jet fuel is considered to be an effective way to replace fossil jet fuel and achieve emission reduction.In this study,the cradle-to-grave life cycle analysis is conducted for three bio-jet fuel conversion pathways,including biomass aqueous phase reforming(APR),hydrogenated esters and fatty acids(HEFA),and hydrothermal liquefaction(HTL).Compared with fossil jet fuels,the three bio-jet fuels have a great advantage on global warming potential(GWP),contributing 29.2,43.6 and 51.2 g CO_(2)-eq/MJ respectively.In general,as a relatively new bio-jet fuel conversion technology,the technology of aqueous phase reforming has minimal environmental impact.If the barriers of raw material availability and economy could be broken down,bio-jet fuel will have great development potential in replacing fossil jet fuel and realizing sustainable development.展开更多
Unanticipated sabotage of two underwater pipelines in the Baltic Sea(Nord Stream 1 and 2)happened on 26September 2022.Massive quantities of natural gas,primarily methane,were released into the atmosphere,which lasted ...Unanticipated sabotage of two underwater pipelines in the Baltic Sea(Nord Stream 1 and 2)happened on 26September 2022.Massive quantities of natural gas,primarily methane,were released into the atmosphere,which lasted for about one week.As a more powerful greenhouse gas than CO_(2),the potential climatic impact of methane is a global concern.Using multiple methods and datasets,a recent study reported a relatively accurate magnitude of the leaked methane at 0.22±0.03 million tons(Mt),which was lower than the initial estimate in the immediate aftermath of the event.Under an energy conservation framework used in IPCC AR6,we derived a negligible increase in global surface air temperature of 1.8×10^(-5)℃ in a 20-year time horizon caused by the methane leaks with an upper limit of 0.25 Mt.Although the resultant warming from this methane leak incident was minor,future carbon release from additional Earth system feedbacks,such as thawing permafrost,and its impact on the methane mitigation pathways of the Paris Agreement,warrants investigation.展开更多
Returning rice straw and leguminous green manure alone or in combination to soil is effective in improving soil fertility in South China.Despite the popularity of this practice,our understanding o f the underlying pro...Returning rice straw and leguminous green manure alone or in combination to soil is effective in improving soil fertility in South China.Despite the popularity of this practice,our understanding o f the underlying processes for straw and manure combined application is relatively poor.In this study,rice straw(carbon(C)/nitrogen(N)ratio of 63),green manure(hairy vetch,C/N ratio of 14),and their mixtures(C/N ratio of 25 and 35)were added into a paddy soil,and their effects on soil N availability and C or N loss under waterlogged conditions were evaluated in a 100-d incubation experiment.All plant residue treatments significantly enhanced C〇2 and CH4 emissions,but decreased N2O emission.Dissolved organic C(DOC)and N(DON)and microbial biomass C in soil and water-soluble organic C and N and mineral N in the upper aqueous layer above soil were also enhanced by all the plant residue treatments except the rice straw treatment,and soil microbial biomass N and mineral N were lower in the rice straw treatment than in the other treatments.Changes in plant residue C/N ratio,DOC/DON ratio,and cellulose content significantly affected greenhouse gas emissions and active C and N concentrations in soil.Additionally,the treatment with green manure alone yielded the largest C and N losses,and incorporation of the plant residue mixture with a C/N ratio of 35 caused the largest net global warming potential(nGWP)among the amended treatments.In conclusion,the co-incorporation of rice straw and green manure can alleviate the limitation resulting from only applying rice straw(N immobilization)or the sole application of leguminous green manure(high C and N losses),and the residue mixture with a C/N ratio of 25 is a better option because of lower nGWP.展开更多
Pollutant gases emitted from the civil jet are doing more and more harm to the environ- ment with the rapid development of the global commercial aviation transport. Low environmental impact has become a new requiremen...Pollutant gases emitted from the civil jet are doing more and more harm to the environ- ment with the rapid development of the global commercial aviation transport. Low environmental impact has become a new requirement for aircraft design. In this paper, estimation method for emis- sion in aircraft conceptual design stage is improved based on the International Civil Aviation Orga- nization （ICAO） aircraft engine emissions databank and the polynomial curve fitting methods. The greenhouse gas emission （CO2 equivalent） per seat per kilometer is proposed to measure the emis- sions. An approximate sensitive analysis and a multi-objective optimization of aircraft design for tradeoff between greenhouse effect and direct operating cost （DOC） are performed with five geom- etry variables of wing configuration and two flight operational parameters. The results indicate that reducing the cruise altitude and Mach number may result in a decrease of the greenhouse effect but an increase of DOC. And the two flight operational parameters have more effects on the emissions than the wing configuration. The Pareto-optimal front shows that a decrease of 29.8% in DOC is attained at the expense of an increase of 10.8% in greenhouse gases.展开更多
Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we condu...Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane（CH4） emission compared with continuous flooding, however,the decrement was far lower than the global average level. The N2O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH4 emissions at low level（75 kg N/ha）. But both CH4 and N2O emissions were uninfluenced at the levels of 150 kg N/ha and 225 kg N/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150 kg N/ha. From our results, we recommended that the intermittent irrigation and 150 kg N/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.展开更多
Reducing CH4 and N20 emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying （AWD） irrigati...Reducing CH4 and N20 emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying （AWD） irrigation is one promising practice that has been shown to reduce CH4 emissions. However, little is known about the impact of this practice on N20 emissions, in particular under Mediterranean climate. To close this knowledge gap, we assessed how AWD influenced grain yield, fluxes and annual budgets of CH4 and N20 emissions, and global warming potential （GWP） in Italian rice systems over a 2-year period. Overall, a larger GWP was observed under AWD, as a result of high N20 emissions which offset reductions in CH4 emissions. In the first year, with 70% water reduction, the yields were reduced by 33%, CH4 emissions decreased by 97%, while N20 emissions increased by more than 5-fold under AWD as compared to PF; in the second year, with a 40% water saving, the reductions of rice yields and CH4 emissions （13% and 11%, respectively） were not significant, but N20 fluxes more than doubled. The transition from anaerobic to aerobic soil conditions resulted in the highest N20 fluxes under AWD. The duration of flooding, transition to aerobic conditions, water level above the soil surface, and the relative timing between fertilization and flooding were the main drivers affecting greenhouse gas mitigation potential under AWD and should be carefully planned through site-specific management options.展开更多
To understand methane （CH4） and nitrous oxide （N2O） emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years （from late 2002 t...To understand methane （CH4） and nitrous oxide （N2O） emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years （from late 2002 to early 2005） in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a non-rice season （PF）, a rice-wheat rotation system （RW） and a rice-rapeseed rotation system （RR） in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3±52.1 and 215.0±45.4 kg CH4 hm^-2 during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5±0.6 kg N2O hm^-2 yr^-1. The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential （GWP）. Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period （ca. 58%, P〈0.05）. However, this change in cultivation system substantially increased N2O emissions, especially in the non-rice season, by a factor of 3.7 to 4.5. On the 100-year horizon, the integrated GWP of total annual CH4 and N2O emissions satisfies PF〉〉RR≈RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW and RR, respectively. These results suggest that changing PF to RW and RR can substantially reduce not only CH4 emission but also the total GWP of the CH4 and N2O emissions.展开更多
Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth...Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth;however,the simultaneous effects of organic fertilizers on N_(2)O and CH_(4)emissions and crop yield in paddy fields remain poorly understood and quantified.In this study,experimental plots were established in conventional double-cropping paddy fields in the Pearl River Delta,China,including an unfertilized control and five fertilizer treatments with fresh organic fertilizer (FOF),successively composted organic fertilizer (SOF),chemically composted organic fertilizer (COF),COF supplemented with inorganic fertilizer (COIF),and chemical fertilizers (CFs)(TFOF,TSOF,TCOF,TCOIF,and TCF,respectively).Paddy field soils behaved simultaneously as an N_(2)O sink (cumulative N_(2)O emission:-196 to-381 g N ha^(-1)) and as a CH_(4)source (cumulative CH_(4)emission:719 to 2 178 kg ha^(-1)).Compared to CFs,the effects of organic fertilizers on N_(2)O emission were not significant.In contrast,total annual CH_(4)emission increased by 157%,132%,125%,and 37%in TFOF,TCOF,TSOF,and TCOIF,respectively,compared to TCF.In TCOIF,rice yield was maintained,while CH_(4)emission was not significantly increased from the paddy fields characterized by a prolonged flood period.An important next step is to extend these field-based measurements to larger rice cultivation areas to quantify the regional and national-scale impacts on greenhouse gas emissions and to help determine the optimum practice for fertilizer use.展开更多
Currently, the refrigerant used in the automotive air conditioning system is R134 a which has a high global warming potential(GWP) value, so people are eager to find a good replacement for it. According to recent stud...Currently, the refrigerant used in the automotive air conditioning system is R134 a which has a high global warming potential(GWP) value, so people are eager to find a good replacement for it. According to recent studies, R1234 yf is considered as one of the top candidates to replace R134 a. In this article, the performances of R1234 yf "drop-in" system and the optimization to the R1234 yf system are experimentally studied and investigated.The expansion valve used for the R1234 yf system is optimized by changing the charged fluid and adjusting the spring force. The results indicate that it can improve the performance of R1234 yf system significantly through adjusting the thermostatic expansion valve. For the thermostatic expansion valves(TEVs) charged with R134 a in thermal bulb, the system performance is optimal. Compared to the original expansion valve, for the R1234 yf system applying the adjusted expansion valves, under different working conditions the cooling capacity increases by 11.3% averagely and the coefficient of performance(COP) increases by 8% averagely.展开更多
The application of nitrogen（N） fertilizer to increase crop yields has a significant influence on soil methane（CH_4） and nitrous oxide（N_2O） emission/uptake.A meta-analysis was carried out on the effect of N appl...The application of nitrogen（N） fertilizer to increase crop yields has a significant influence on soil methane（CH_4） and nitrous oxide（N_2O） emission/uptake.A meta-analysis was carried out on the effect of N application on（i） CH_4 emissions in rice paddies,（ii） CH_4 uptake in upland fields and（iii） N_2O emissions.The responses of CH_4 emissions to N application in rice paddies were highly variable and overall no effects were found.CH_4 emissions were stimulated at low N application rates（〈100 kg N ha^（-1）） but inhibited at high N rates（〉200 kg N ha^（-1）） as compared to no N fertilizer（control）.The response of CH_4 uptake to N application in upland fields was 15%lower than control,with a mean CH_4 uptake factor of-0.001 kg CH_4-C kg^（-1） N.The mean N_2O emission factors were 1.00 and 0.94%for maize（Zea mays） and wheat（Triticum aestivum）,respectively,but significantly lower for the rice（Oryza sativa）（0.51%）.Compared with controls,N addition overall increased global warming potential of CH_4 and N_2O emissions by 78%.Our result revealed that response of CH_4 emission to N input might depend on the CH_4concentration in rice paddy.The critical factors that affected CH_4 uptake and N_2O emission were N fertilizer application rate and the controls of CH_4 uptake and N_2O emission.The influences of application times,cropping systems and measurement frequency should all be considered when assessing CH_4 and N_2O emissions/uptake induced by N fertilizer.展开更多
Addressing concerns about mitigating greenhouse gas （GHG） emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In...Addressing concerns about mitigating greenhouse gas （GHG） emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide （N2O） and methane （CH4） fluxes during the maize （Zea mays L.） season under various agricultural management regimes including conventional treatment （CONT） with high N fertilizer application at a rate of 300 kg N ha-1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment （OPTIT）, optimal fertilization 2 treatment （OPT2T）, and controlled-release urea treatment （CRUT） with reduced N fertilizer application and irrigation, and a control （CK） with no N fertilizer. In contrast to CONT, balanced N fertilization treatments （OPT1T, OPT2T, and CRUT） and CK demonstrated a significant drop in cumulative N20 emission （1.70 v.s. 0.43-1.07 kg N ha-l）, indicating that balanced N fertilization substantially reduced N20 emission. The vMues of the N20 emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPTIT, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N20 emission, were estimated to be 188 kg CO2-eq ha-1 for CK and 419-765 kg CO2-eq ha-1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPTIT, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.展开更多
Deserts are sensitive to environmental changes caused by human interference and are prone to degradation.Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand.However,the ...Deserts are sensitive to environmental changes caused by human interference and are prone to degradation.Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand.However,the effects of grazing,which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification,on the greenhouse gas(GHG)fluxes from soils remain unknown.Herein,we investigated GHG fluxes in the Hobq Desert,Inner Mongolia Autonomous Region of China,at the mobile(desertified),fixed(vegetated),and grazed(re-desertified)sites from January 2018 to December 2019.We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential(GWP).CO_(2)was emitted at an average rate of 4.2,3.7,and 1.1 mmol/(m^(2)•h)and N_(2)O was emitted at an average rate of 0.19,0.15,and 0.09μmol/(m^(2)•h)at the grazed,fixed,and mobile sites,respectively.Mean CH_(4) consumption was as follows:fixed site(2.9μmol/(m^(2)•h))>grazed site(2.7μmol/(m^(2)•h))>mobile site(1.1μmol/(m^(2)•h)).GHG fluxes varied seasonally,and soil temperature(10 cm)and soil water content(30 cm)were the key micrometeorological factors affecting the fluxes.The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO_(2)and N_(2)O emissions and decreased CH_(4) absorption.Grazing also significantly increased the GWP of the soil(P<0.05).This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage.These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.展开更多
In the age of global warming, energy saving features and overall reduction of environmental impact are critical components that must be addressed when developing new HVAC （heating ventilation and air conditioning） u...In the age of global warming, energy saving features and overall reduction of environmental impact are critical components that must be addressed when developing new HVAC （heating ventilation and air conditioning） units. We chose R32 refrigerant, with its lower LCCP （life cycle climate performance） as a more sustainable choice than R410A. However, R32 has its drawbacks. Due to its smaller molecular weight, internal leakage loss is higher for R32. Moreover, high discharge gas temperature decreases the reliability of the compressor, and makes a large overheating loss increase. In this study, we will describe the technologies （reducing the piston pressurizing force, heat-insulating structure, optimizing the port diameter） that were developed to overcome these drawbacks. We will also oresent the performance and reliability of the newly develoned high efficiency swing, comnressor series for R32 refrigerant.展开更多
Tillage and fertilization practices used in row crop production are thought to alter greenhouse gas emissions from soil. This study was conducted to determine the impact of fertilizer sources, land management practice...Tillage and fertilization practices used in row crop production are thought to alter greenhouse gas emissions from soil. This study was conducted to determine the impact of fertilizer sources, land management practices, and fertilizer placement methods on greenhouse gas （CO2, CH4, and N2O） emissions. A new prototype implement developed for applying poultry litter in subsurface bands in the soil was used in this study. The field site was located at the Sand Mountain Research and Extension Center in the Appalachian Plateau region of northeast Alabama, USA, on a Hartsells fine sandy loam （fine-loamy, siliceous, subactive, thermic Typic Hapludults）. Measurements of carbon dioxide （CO2）, methane （CH4）, and nitrous oxide （N20） emissions followed GRACEnet （greenhouse gas reduction through agricultural carbon enhancement network） protocols to assess the effects of different tillage （conventional vs. no-tillage） and fertilizer placement （subsurface banding vs. surface application） practices in a corn （Zea mays L.） cropping system. Fertilizer sources were urea-ammonium nitrate （UAN）, ammonium nitrate （AN） and poultry litter （M） applied at a rate of 170 kg ha^（-1） of available N. Banding of fertilizer resulted in the greatest concentration of gaseous loss （CO2 and N2O） compared to surface applications of fertilizer. Fertilizer banding increased CO2 and N2O loss on various sampling days throughout the season with poultry litter banding emitting more gas than UAN banding. Conventional tillage practices also resulted in a higher concentration of CO2 and N2O loss when evaluating tillage by sampling day. Throughout the course of this study, CH4 flux was not affected by tillage, fertilizer source, or fertilizer placement method. These results suggest that poultry litter use and banding practices have the potential to increase greenhouse gas emissions.展开更多
基金supported by National Natural Science Foundation of China(Grant No.72394401).
文摘Grazing management significantly influences greenhouse gas(GHG)emissions and the global warming potential(GWP)in grasslands.Yet,a limited understanding of the impact of grazing and grazing exclusion on GHG emis-sions and GWP in grasslands hinders progress towards grassland ecosystem sustainability and GHG mitigation.We conducted a global meta-analysis of 75 published studies to investigate the effects of grazing and grazing exclusion on methane(CH_(4)),carbon dioxide(CO_(2)),nitrous oxide(N_(2 )O),and GWP.Our results revealed that grazing and grazing exclusion significantly increased the CO_(2) and CH4 emissions,respectively.The responses of GHG emissions and GWP to grazing were regulated by grazing intensity and elevation.We also found that light grazing significantly decreased GWP but heavy grazing increased GWP.Reducing grazing intensity was a simple and effective method through stocking rate adjustment,which promised a large GHG mitigation poten-tial.Our results demonstrated that GHG emissions increased with elevation under grassland grazing,implying that irrational grazing in high-elevation grasslands promoted GHG emissions.In comparison with grazing,only long-term grazing exclusion reduced the GWP,and CH4 emissions enhanced with grazing exclusion duration.However,long-term grazing exclusion may shift economic demand and grazing burden to other areas.Overall,we suggested that regulating the grazing intensity,rather than grazing exclusion,was an effective way to re-duce GHG emissions.Our study contributed to the enhancement of sustainable grazing management practices for GHG balance and GWP in global grasslands,and offered a global picture for understanding the changes in GHG emissions and GWP under different grazing management regimes.
基金sponsored by the National Natural Science Foundation of China,China(Grant Nos.31470529,32125027)Zhejiang A&F University Research and Development Fund,China(Nos.2022LFR006,2021LFR060).
文摘Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.
基金supported by the National Key Research and Development Program of China(No.2018YFD1100600)Shanghai Municipal Government State-Owned Assets Supervision and Administration Commission(No.2022028)。
文摘The significant increase in the demand for biomass waste treatment after garbage classification has led to housefly larvae treatment becoming an attractive treatment option.It can provide a source of protein while treating biomass waste,which means that nutrients can be returned to the natural food chain.However,the performance of this technology in terms of its environmental impacts is still unclear,particularly with regards to global warming potential(GWP).This study used a life cycle assessment(LCA)approach to assess a housefly larvae treatment plant with a treatment capacity of 50 tons of biomass waste per day.The LCA results showed that the 95% confidence intervals for the GWP in summer and winter were determined to be 24.46-32.81 kg CO_(2) equivalent(CO_(2)-eq)/ton biomass waste and5.37-10.08 kg CO_(2)-eq/ton biomass waste,respectively.The greater GWP value in summer is due to the longer ventilation time and higher ventilation intensity in summer,which consumes more power.The main GWP contributions are from(1)electricity needs(accounting for 78.6% of emissions in summer and 70.2%in winter)and(2)product substitution by mature housefly larvae and compost(both summer and winter accounting for 96.8% of carbon reduction).
基金supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP)the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20172010105910)。
文摘Perfluorocarbon gas is widely used in the semiconductor industry.However,perfluorocarbon has a negative effect on the global environment owing to its high global warming potential(GWP) value.An alternative solution is essential.Therefore,we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF_3 with C_6F_(12)O,which has a low GWP and is in a liquid state at room temperature.In this study,silicon oxynitride(SiON) films were plasma-etched using inductively coupled CF4+C_6F_(12)O+O_2 mixed plasmas.Subsequently,the etching characteristics of the film,such as etching rate,etching profile,selectivity over Si,and photoresist,were investigated.A double Langmuir probe was used and optical emission spectroscopy was performed for plasma diagnostics.In addition,a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film surface.Consequently,the etching characteristics of the C_6F_(12)O mixed plasma exhibited a lower etching rate,higher SiON/Si selectivity,lower plasma damage,and more vertical etched profiles than the conventional CHF_3 mixed plasma.In addition,the C_6F_(12)O gas can be recovered in the liquid state,thereby decreasing global warming.These results confirmed that the C_6F_(12)O precursor can sufficiently replace the conventional etching gas.
基金supported by National Natural Science Foundation of China (Grant No. 40775006)National Basic Research Program of Chnia (Grant No. 2010CB955703)the Special Foundation for Climate Change (Grant No. 2010-2200509)
文摘We developed two radiation parameterizations with different resolutions （17-band and 998-band） for perfluorocarbons （PFCs） and sulfur hexafluoride （SF6） using the updated High-resolution Transmission Molecular Absorption （HITRAN） 2004 database and the correlated k-distribution method. We analyzed the impacts of the two radiation schemes on heating rates. Then we studied their instantaneous radiative efficiency, stratospheric adjusted radiative efficiency, global warming potential （GWP）, and global temperature potential （GTP）, for both clear- and all-sky conditions using a high-resolution radiation scheme. We found that the stratosphere-adjusted radiative efficiencies of C2F6, CF4, and SF6 for the whole sky were 0.346, 0.098, and 0.680 W m^-2 ppbv^-1, respectively. Radiative forcing from the industrial revolution to 2005 was 0.001, 0.007, and 0.004 W m^-2, respectively; and was predicted to rise to 0.008, 0.036, and 0.037 W m^-2, respectively, by 2100, according to emission scenarios provided by the IPCC. The GWPs of C2F6, CF4, and SF6 are 17035, 7597, and 31298, respectively, for a time horizon of 100 years relative to CO2. Their GTPs of pulse and sustained emissions, GTPv and GTPs, are 22468, 10052, and 40935 and 16498, 7355, and 30341, respectively, for a 100-year time horizon.
文摘This paper presents a theoretical method to calculate the minimum inerting concentration(MIC)of binary and ternary blends(refrigerants)that are used in small refrigeration systems.MIC is the concentration of the dilutant which makes the flammable mixture into just non-flammable(at non-zero quenching potential).In this study,the refrigerant safety parameters such as flammability,Global Warming Potential(GWP)and performance(COP)are analyzed for twelve binary and thirteen ternary blends containing one flammable and two nonflammable(dilutant)components.Flammability investigation was carried out with the hydrocarbon refrigerants R290,R600,R600a each mixed with dilutants R227ea,R125,R245fa,R13I1 and R134a at different concentrations respectively.Two methods,thermal balance method(TBM)and modified thermal balanced method(MTBM),are used to estimate the MIC(which decides the flammable zone).Thirteen ternary blends were identified based on the MIC values estimated using MTBM.In the case of ternary blends,it was observed that the non-flammable zone is high for the compositions of the Mixture G,Mixture H and Mixture I.It was also estimated that the COPs of the proposed mixtures M22,M24,M25 and M27 are 4%greater than the COP of R134a(for the same operating conditions).Further,it was also understood that the corresponding GWP value is reduced by 90%to 97%for the mixtures(M21,M22,M24,M25 and M27)when compared to R134a(GWP=1300).Therefore,out of the thirteen proposed ternary mixtures(M15 to M27),the mixtures(M21,M22,M24,M25 and M27)are safe in terms of flammability,GWP and possess reasonable COP which can be a potential alternative refrigerant mixture to R134a in small refrigeration systems.
基金supported by the National Key R&D Program of China(2018YFB1501500).
文摘Due to the large amount of greenhouse gas(GHG)emissions and the high dependence on fossil energy,the aviation industry has attracted a lot of attention for emission reduction and sustainable development.Biomass is a green and sustainable renewable resource,and its chemical conversion to produce bio-jet fuel is considered to be an effective way to replace fossil jet fuel and achieve emission reduction.In this study,the cradle-to-grave life cycle analysis is conducted for three bio-jet fuel conversion pathways,including biomass aqueous phase reforming(APR),hydrogenated esters and fatty acids(HEFA),and hydrothermal liquefaction(HTL).Compared with fossil jet fuels,the three bio-jet fuels have a great advantage on global warming potential(GWP),contributing 29.2,43.6 and 51.2 g CO_(2)-eq/MJ respectively.In general,as a relatively new bio-jet fuel conversion technology,the technology of aqueous phase reforming has minimal environmental impact.If the barriers of raw material availability and economy could be broken down,bio-jet fuel will have great development potential in replacing fossil jet fuel and realizing sustainable development.
基金supported by the National Key Research and Development Program(Grant No.2017YFA0603503)the National Natural Science Foundation of China(Grant No.41605057)。
文摘Unanticipated sabotage of two underwater pipelines in the Baltic Sea(Nord Stream 1 and 2)happened on 26September 2022.Massive quantities of natural gas,primarily methane,were released into the atmosphere,which lasted for about one week.As a more powerful greenhouse gas than CO_(2),the potential climatic impact of methane is a global concern.Using multiple methods and datasets,a recent study reported a relatively accurate magnitude of the leaked methane at 0.22±0.03 million tons(Mt),which was lower than the initial estimate in the immediate aftermath of the event.Under an energy conservation framework used in IPCC AR6,we derived a negligible increase in global surface air temperature of 1.8×10^(-5)℃ in a 20-year time horizon caused by the methane leaks with an upper limit of 0.25 Mt.Although the resultant warming from this methane leak incident was minor,future carbon release from additional Earth system feedbacks,such as thawing permafrost,and its impact on the methane mitigation pathways of the Paris Agreement,warrants investigation.
基金This work was supported by the China Agriculture Research System-Green Manure,the Virtual Joint Nitrogen Centre(N-Circle)(No.B B/N 013484/1)the Science and Technology Innovation Project of Chinese Academy of Agricultural Sciences(2013-2017)the Chinese Outstanding Talents Program in Agricultural Science.
文摘Returning rice straw and leguminous green manure alone or in combination to soil is effective in improving soil fertility in South China.Despite the popularity of this practice,our understanding o f the underlying processes for straw and manure combined application is relatively poor.In this study,rice straw(carbon(C)/nitrogen(N)ratio of 63),green manure(hairy vetch,C/N ratio of 14),and their mixtures(C/N ratio of 25 and 35)were added into a paddy soil,and their effects on soil N availability and C or N loss under waterlogged conditions were evaluated in a 100-d incubation experiment.All plant residue treatments significantly enhanced C〇2 and CH4 emissions,but decreased N2O emission.Dissolved organic C(DOC)and N(DON)and microbial biomass C in soil and water-soluble organic C and N and mineral N in the upper aqueous layer above soil were also enhanced by all the plant residue treatments except the rice straw treatment,and soil microbial biomass N and mineral N were lower in the rice straw treatment than in the other treatments.Changes in plant residue C/N ratio,DOC/DON ratio,and cellulose content significantly affected greenhouse gas emissions and active C and N concentrations in soil.Additionally,the treatment with green manure alone yielded the largest C and N losses,and incorporation of the plant residue mixture with a C/N ratio of 35 caused the largest net global warming potential(nGWP)among the amended treatments.In conclusion,the co-incorporation of rice straw and green manure can alleviate the limitation resulting from only applying rice straw(N immobilization)or the sole application of leguminous green manure(high C and N losses),and the residue mixture with a C/N ratio of 25 is a better option because of lower nGWP.
基金supported by the Fundamental Research Funds for the Central Universities (NUAA NN2012071)China Postdoctoral Science Foundation (2011M500919)
文摘Pollutant gases emitted from the civil jet are doing more and more harm to the environ- ment with the rapid development of the global commercial aviation transport. Low environmental impact has become a new requirement for aircraft design. In this paper, estimation method for emis- sion in aircraft conceptual design stage is improved based on the International Civil Aviation Orga- nization （ICAO） aircraft engine emissions databank and the polynomial curve fitting methods. The greenhouse gas emission （CO2 equivalent） per seat per kilometer is proposed to measure the emis- sions. An approximate sensitive analysis and a multi-objective optimization of aircraft design for tradeoff between greenhouse effect and direct operating cost （DOC） are performed with five geom- etry variables of wing configuration and two flight operational parameters. The results indicate that reducing the cruise altitude and Mach number may result in a decrease of the greenhouse effect but an increase of DOC. And the two flight operational parameters have more effects on the emissions than the wing configuration. The Pareto-optimal front shows that a decrease of 29.8% in DOC is attained at the expense of an increase of 10.8% in greenhouse gases.
基金supported by the China Postdoctoral Science Foundation(No.2012M511005)National Key Technology Support Program of China(No.2015BAC02B02)+6 种基金the Agro-scientific Research Programs in Public Interest(No.201303102)National Natural Science Foundation of China(No.31501263)the Postdoctoral Financial Assistance of Heilongjiang Province(No.LBH-Z12232)the Scientific Research Initiation Fund for Introduction of Ph.D Talent of Heilongjiang Academy of Agricultural Sciences(No.201507-14)the State Key Program of China(No.2016YFD0300900)the Major Project of Research and Development of Applied Technology of Heilongjiang Province(No.GA15B101)the Provincial Matching Funds to the National Foundation of Applied Technology Research and Development Program in Heilongjiang Province(No.GX16B002)
文摘Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane（CH4） emission compared with continuous flooding, however,the decrement was far lower than the global average level. The N2O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH4 emissions at low level（75 kg N/ha）. But both CH4 and N2O emissions were uninfluenced at the levels of 150 kg N/ha and 225 kg N/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150 kg N/ha. From our results, we recommended that the intermittent irrigation and 150 kg N/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.
基金funded by Mars Belgium NV (Mars Food) and Ministero delle Politiche Agrarie, Alimentari e Forestali of Italy (POLORISO project, D.M.5337, Dec.5, 2011)
文摘Reducing CH4 and N20 emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying （AWD） irrigation is one promising practice that has been shown to reduce CH4 emissions. However, little is known about the impact of this practice on N20 emissions, in particular under Mediterranean climate. To close this knowledge gap, we assessed how AWD influenced grain yield, fluxes and annual budgets of CH4 and N20 emissions, and global warming potential （GWP） in Italian rice systems over a 2-year period. Overall, a larger GWP was observed under AWD, as a result of high N20 emissions which offset reductions in CH4 emissions. In the first year, with 70% water reduction, the yields were reduced by 33%, CH4 emissions decreased by 97%, while N20 emissions increased by more than 5-fold under AWD as compared to PF; in the second year, with a 40% water saving, the reductions of rice yields and CH4 emissions （13% and 11%, respectively） were not significant, but N20 fluxes more than doubled. The transition from anaerobic to aerobic soil conditions resulted in the highest N20 fluxes under AWD. The duration of flooding, transition to aerobic conditions, water level above the soil surface, and the relative timing between fertilization and flooding were the main drivers affecting greenhouse gas mitigation potential under AWD and should be carefully planned through site-specific management options.
文摘To understand methane （CH4） and nitrous oxide （N2O） emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years （from late 2002 to early 2005） in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a non-rice season （PF）, a rice-wheat rotation system （RW） and a rice-rapeseed rotation system （RR） in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3±52.1 and 215.0±45.4 kg CH4 hm^-2 during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5±0.6 kg N2O hm^-2 yr^-1. The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential （GWP）. Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period （ca. 58%, P〈0.05）. However, this change in cultivation system substantially increased N2O emissions, especially in the non-rice season, by a factor of 3.7 to 4.5. On the 100-year horizon, the integrated GWP of total annual CH4 and N2O emissions satisfies PF〉〉RR≈RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW and RR, respectively. These results suggest that changing PF to RW and RR can substantially reduce not only CH4 emission but also the total GWP of the CH4 and N2O emissions.
基金funded by the National Natural Science Foundation of China(No.41771291)the Jiangsu Agricultural Science and Technology Innovation Fund,China(No.CX(21)3183)+1 种基金the Jiangsu Specially Appointed Professor Program,Chinathe Jiangsu Six Talent Peaks Program,China(No.NY-083)。
文摘Rice fields are a major source of greenhouse gases,such as nitrous oxide (N_(2)O) and methane (CH_(4)).Organic fertilizers may potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth;however,the simultaneous effects of organic fertilizers on N_(2)O and CH_(4)emissions and crop yield in paddy fields remain poorly understood and quantified.In this study,experimental plots were established in conventional double-cropping paddy fields in the Pearl River Delta,China,including an unfertilized control and five fertilizer treatments with fresh organic fertilizer (FOF),successively composted organic fertilizer (SOF),chemically composted organic fertilizer (COF),COF supplemented with inorganic fertilizer (COIF),and chemical fertilizers (CFs)(TFOF,TSOF,TCOF,TCOIF,and TCF,respectively).Paddy field soils behaved simultaneously as an N_(2)O sink (cumulative N_(2)O emission:-196 to-381 g N ha^(-1)) and as a CH_(4)source (cumulative CH_(4)emission:719 to 2 178 kg ha^(-1)).Compared to CFs,the effects of organic fertilizers on N_(2)O emission were not significant.In contrast,total annual CH_(4)emission increased by 157%,132%,125%,and 37%in TFOF,TCOF,TSOF,and TCOIF,respectively,compared to TCF.In TCOIF,rice yield was maintained,while CH_(4)emission was not significantly increased from the paddy fields characterized by a prolonged flood period.An important next step is to extend these field-based measurements to larger rice cultivation areas to quantify the regional and national-scale impacts on greenhouse gas emissions and to help determine the optimum practice for fertilizer use.
基金the National Key Technologies Research and Development Program of China During the 12th Five-Year Plan Period(No.SQ2011GX03D03999)
文摘Currently, the refrigerant used in the automotive air conditioning system is R134 a which has a high global warming potential(GWP) value, so people are eager to find a good replacement for it. According to recent studies, R1234 yf is considered as one of the top candidates to replace R134 a. In this article, the performances of R1234 yf "drop-in" system and the optimization to the R1234 yf system are experimentally studied and investigated.The expansion valve used for the R1234 yf system is optimized by changing the charged fluid and adjusting the spring force. The results indicate that it can improve the performance of R1234 yf system significantly through adjusting the thermostatic expansion valve. For the thermostatic expansion valves(TEVs) charged with R134 a in thermal bulb, the system performance is optimal. Compared to the original expansion valve, for the R1234 yf system applying the adjusted expansion valves, under different working conditions the cooling capacity increases by 11.3% averagely and the coefficient of performance(COP) increases by 8% averagely.
基金financed by the Chinese Academy of Sciences for Strategic Priority Research Program(XDA05050602)the Key Technologies R&D Program of China during the 12th Five-Year Plan period of China(2012BAD14B01-1)
文摘The application of nitrogen（N） fertilizer to increase crop yields has a significant influence on soil methane（CH_4） and nitrous oxide（N_2O） emission/uptake.A meta-analysis was carried out on the effect of N application on（i） CH_4 emissions in rice paddies,（ii） CH_4 uptake in upland fields and（iii） N_2O emissions.The responses of CH_4 emissions to N application in rice paddies were highly variable and overall no effects were found.CH_4 emissions were stimulated at low N application rates（〈100 kg N ha^（-1）） but inhibited at high N rates（〉200 kg N ha^（-1）） as compared to no N fertilizer（control）.The response of CH_4 uptake to N application in upland fields was 15%lower than control,with a mean CH_4 uptake factor of-0.001 kg CH_4-C kg^（-1） N.The mean N_2O emission factors were 1.00 and 0.94%for maize（Zea mays） and wheat（Triticum aestivum）,respectively,but significantly lower for the rice（Oryza sativa）（0.51%）.Compared with controls,N addition overall increased global warming potential of CH_4 and N_2O emissions by 78%.Our result revealed that response of CH_4 emission to N input might depend on the CH_4concentration in rice paddy.The critical factors that affected CH_4 uptake and N_2O emission were N fertilizer application rate and the controls of CH_4 uptake and N_2O emission.The influences of application times,cropping systems and measurement frequency should all be considered when assessing CH_4 and N_2O emissions/uptake induced by N fertilizer.
基金Supported by the National Natural Science Foundation of China(Nos.30870414 and 31170489)the Special Fund for Agroscientific Research in the Public Interest of China(No.201103039)
文摘Addressing concerns about mitigating greenhouse gas （GHG） emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide （N2O） and methane （CH4） fluxes during the maize （Zea mays L.） season under various agricultural management regimes including conventional treatment （CONT） with high N fertilizer application at a rate of 300 kg N ha-1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment （OPTIT）, optimal fertilization 2 treatment （OPT2T）, and controlled-release urea treatment （CRUT） with reduced N fertilizer application and irrigation, and a control （CK） with no N fertilizer. In contrast to CONT, balanced N fertilization treatments （OPT1T, OPT2T, and CRUT） and CK demonstrated a significant drop in cumulative N20 emission （1.70 v.s. 0.43-1.07 kg N ha-l）, indicating that balanced N fertilization substantially reduced N20 emission. The vMues of the N20 emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPTIT, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N20 emission, were estimated to be 188 kg CO2-eq ha-1 for CK and 419-765 kg CO2-eq ha-1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPTIT, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.
基金supported by the Inner Mongolia Science and Technology Project of China(2022YFDZ0027)the Mongolia Basic Geographical Factors and Land Use/Cover Survey of China(2017FY101301-4)。
文摘Deserts are sensitive to environmental changes caused by human interference and are prone to degradation.Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand.However,the effects of grazing,which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification,on the greenhouse gas(GHG)fluxes from soils remain unknown.Herein,we investigated GHG fluxes in the Hobq Desert,Inner Mongolia Autonomous Region of China,at the mobile(desertified),fixed(vegetated),and grazed(re-desertified)sites from January 2018 to December 2019.We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential(GWP).CO_(2)was emitted at an average rate of 4.2,3.7,and 1.1 mmol/(m^(2)•h)and N_(2)O was emitted at an average rate of 0.19,0.15,and 0.09μmol/(m^(2)•h)at the grazed,fixed,and mobile sites,respectively.Mean CH_(4) consumption was as follows:fixed site(2.9μmol/(m^(2)•h))>grazed site(2.7μmol/(m^(2)•h))>mobile site(1.1μmol/(m^(2)•h)).GHG fluxes varied seasonally,and soil temperature(10 cm)and soil water content(30 cm)were the key micrometeorological factors affecting the fluxes.The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO_(2)and N_(2)O emissions and decreased CH_(4) absorption.Grazing also significantly increased the GWP of the soil(P<0.05).This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage.These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.
文摘In the age of global warming, energy saving features and overall reduction of environmental impact are critical components that must be addressed when developing new HVAC （heating ventilation and air conditioning） units. We chose R32 refrigerant, with its lower LCCP （life cycle climate performance） as a more sustainable choice than R410A. However, R32 has its drawbacks. Due to its smaller molecular weight, internal leakage loss is higher for R32. Moreover, high discharge gas temperature decreases the reliability of the compressor, and makes a large overheating loss increase. In this study, we will describe the technologies （reducing the piston pressurizing force, heat-insulating structure, optimizing the port diameter） that were developed to overcome these drawbacks. We will also oresent the performance and reliability of the newly develoned high efficiency swing, comnressor series for R32 refrigerant.
基金Supported by the United States Department of Agriculture, Agricultural Research Service (USDA-ARS) fundsthe Alabama Wheat and Feed Grains Commodity Grant, USA
文摘Tillage and fertilization practices used in row crop production are thought to alter greenhouse gas emissions from soil. This study was conducted to determine the impact of fertilizer sources, land management practices, and fertilizer placement methods on greenhouse gas （CO2, CH4, and N2O） emissions. A new prototype implement developed for applying poultry litter in subsurface bands in the soil was used in this study. The field site was located at the Sand Mountain Research and Extension Center in the Appalachian Plateau region of northeast Alabama, USA, on a Hartsells fine sandy loam （fine-loamy, siliceous, subactive, thermic Typic Hapludults）. Measurements of carbon dioxide （CO2）, methane （CH4）, and nitrous oxide （N20） emissions followed GRACEnet （greenhouse gas reduction through agricultural carbon enhancement network） protocols to assess the effects of different tillage （conventional vs. no-tillage） and fertilizer placement （subsurface banding vs. surface application） practices in a corn （Zea mays L.） cropping system. Fertilizer sources were urea-ammonium nitrate （UAN）, ammonium nitrate （AN） and poultry litter （M） applied at a rate of 170 kg ha^（-1） of available N. Banding of fertilizer resulted in the greatest concentration of gaseous loss （CO2 and N2O） compared to surface applications of fertilizer. Fertilizer banding increased CO2 and N2O loss on various sampling days throughout the season with poultry litter banding emitting more gas than UAN banding. Conventional tillage practices also resulted in a higher concentration of CO2 and N2O loss when evaluating tillage by sampling day. Throughout the course of this study, CH4 flux was not affected by tillage, fertilizer source, or fertilizer placement method. These results suggest that poultry litter use and banding practices have the potential to increase greenhouse gas emissions.
