不同耕作方式对稻田净增温潜势和温室气体强度的影响

免耕技术近年来在南方稻区被广泛推广应用,但该项技术是否有利于减缓稻田综合温室效应目前并不清楚.因此,本文以双季稻-紫云英为研究对象,利用静态箱-气相色谱法分别研究不同耕作方式对稻田CH4和N2O排放、双季稻产量、土壤固碳、稻田净综合增温潜势(GWP)和温室气体强度(GHGI)的影响.试验处理包括常规翻耕(CT)、旋耕(RT)和免耕(NT).结果表明,稻田周年CH4累积排放量为233.5~404.0kg·hm-2·a-1,NT和RT处理分别比CT增加73.1%和35.1%.晚稻生长季CH4排放量占周年CH4排放量的53.7%~66.5%,其中,晚稻移栽至烤田期间CH4累积排放通量占晚稻季排放总量的77.0%~81.3%.稻田N2O累积排放量为4.00~4.82 kg·hm-2·a-1(以N计),但各处理之间没有显著差异.稻田年固碳量为0.36~1.31 t·hm-2·a-1(以C计),其中,NT处理比CT和RT处理分别增加148.4%和261.0%.双季稻周年产量为15.2~17.1 t·hm-2,耕作方式对产量没有显著影响.稻田净GWP为5095.4~7788 kg·hm-2(以CO2当量计),其中,RT和NT处理分别比CT增加52.8%和32.2%.稻田GHGI为0.30~0.46 kg·kg-1(以每kg粮食产量产生的CO2当量计),其中,RT和NT处理分别显著高于CT处理50.1%和45.3%.综上所述,免耕在短期内会增加稻田温室效应,但可以促进土壤固碳量的显著增加,因此,其固碳减排的长期效应还有待观测.     

施氮对稻麦轮作系统综合增温潜势的影响

采用典型区域田间试验结合生物地球化学模型（DNDC模型），以上海市崇明岛为例对稻麦轮作系统作物产量和温室气体排放进行了模拟研究。结果表明：DNDC模型能较好地模拟田间实测到的稻麦轮作系统温室气体排放通量。在常规用量的80%~150%之间增施氮肥对作物产量无显著增加，但稻麦轮作系统综合温室效应呈递增趋势。东滩农业园区稻麦轮作系统最优施氮量为常规用量的6298%，此时单位产量增温潜势（Global Warming Potential,GWP）最小，作物产量为12 8775 kg/(hm2〖DK〗·a)，综合温室效应较常规施氮降低3670%。长江下游地区稻麦两熟制农业生态系统能够通过合理控制农田氮肥用量减少温室气体排放净通量，降低作物单位产量GWP     

双视角下中国畜牧业甲烷排放的温室效应

准确评价甲烷（CH₄）的温室效应是制定有效减排路径的基础.首次采用新提出的、针对短寿命气候污染物（SLCP）设计的气候指标GWP-star （GWP^*）对中国畜牧业CH₄排放的温室效应进行定量评价,并与常用的GWP指标评价结果相比较.结果表明,GWP的视角下我国畜牧业CH₄排放的温室效应持续增加.因此,畜牧业实现碳中和需要完全消除排放,或以增加碳汇、增加资源化利用的形式抵消每年稳定的CH₄排放.在GWP^*的视角下,2015~2019年间畜牧业CH₄排放的温室效应较20年前有所减少,降低的热量相当于从20年前的大气中减少2.1×10⁴万t CO₂的热量,畜牧业只需每年有效降低0.3%的CH₄排放则可在短期内实现自身碳中和.在中国畜牧业持续采取有效减排措施的情况下,采用GWP^*的标准制定减排目标比用GWP制定的减排目标更早达到,但选择GWP还是GWP^*需要综合考虑评价的目的、评价的时间尺度和实际可操作性.     

Effect of elevated tropospheric ozone on methane and nitrous oxide emission from rice soil in north India

Physiological changes in crop plants in response to the elevated tropospheric ozone (O₃) may alter N and C cycles in soil. This may also affect the atmosphere-biosphere exchange of radiatively important greenhouse gases (GHGs), e.g. methane (CH₄) and nitrous oxide (N₂O) from soil. A study was carried out during July to November of 2007 and 2008 in the experimental farm of Indian Agricultural Research Institute, New Delhi to assess the effects of elevated tropospheric ozone on methane and nitrous oxide emissions from rice (Oryza sativa L.) soil. Rice crop was grown in open top chambers (OTC) under elevated ozone (EO), non-filtered air (NF), charcoal filtered air (CF) and ambient air (AA). Seasonal mean concentrations of O₃ were 4.3 ± 0.9, 26.2 ± 1.9, 59.1 ± 4.2 and 27.5 ± 2.3 ppb during year 2007 and 5.9 ± 1.1, 37.2 ± 2.5, 69.7 ± 3.9 and 39.2 ± 1.8 ppb during year 2008 for treatments CF, NF, EO and AA, respectively. Cumulative seasonal CH₄ emission reduced by 29.7% and 40.4% under the elevated ozone (EO) compared to the non-filtered air (NF), whereas the emission increased by 21.5% and 16.7% in the charcoal filtered air (CF) in 2007 and 2008, respectively. Cumulative seasonal emission of N₂O ranged from 47.8 mg m⁻² in elevated ozone to 54.6 mg m⁻² in charcoal filtered air in 2007 and from 46.4 to 62.1 mg m⁻² in 2008. Elevated ozone reduced grain yield by 11.3% and 12.4% in 2007 and 2008, respectively. Global warming potential (GWP) per unit of rice yield was the least under elevated ozone levels. Dissolved organic C content of soil was lowest under the elevated ozone treatment. Decrease in availability of substrate i.e., dissolved organic C under elevated ozone resulted in a decline in GHG emissions. Filtration of ozone from ambient air increased grain yield and growth parameters of rice and emission of GHGs.     

沼泽湿地CO2、CH4、N2O排放对氮输入的响应

利用静态暗箱-气象色谱法，选取小叶章沼泽化草甸进行野外原位试验，研究氮输入对沼泽湿地CO2、CH4和N2O等3种温室气体排放的影响,结果表明：氮输入对沼泽湿地CO2和CH4排放有明显影响，其季节排放总量分别是对照处理的1.3和2.5倍，但对CO2和CH4的季节变化模式无明显影响；氮输入对N2O的排放强度和季节变化模式均有显著影响,CO2排放通量与5cm深土壤温度存在显著的正相关关系，与地表温度和1.5m气温存在指数关系，而CH4和N2O排放与温度之间没有显著的相关性．在20、100和500年时间尺度上氮输入处理的CH4和N2O全球增温潜势（GWP）分别比对照处理增加了150％、150％和80％，表明氮输入在长、短时间尺度上都是增强CH4和N2O的温室效应的。     

秸秆与化肥减量配施对菜地土壤温室气体排放的影响

采用静态箱/气相色谱法,2016年11月至2017年9月通过田间原位试验,设置了无物料还田(CK)、常规化肥(F)、秸秆还田配施100%化肥(100FS)、秸秆还田配施70%化肥(70FS)、秸秆还田配施60%化肥(60FS)、秸秆还田配施50%化肥(50FS),对比分析了在化肥减量的基础上,配施秸秆处理的菜地(莴笋-卷心菜-辣椒轮作)土壤CO_2、CH_4、N_2O动态变化特征及温室效应,研究秸秆与化肥减量配施对菜地温室气体排放的影响.结果表明,土壤CO_2、CH_4、N_2O排放具有一定的季节变化规律,排放高峰主要集中在4~8月,且在施肥灌水后均会出现气体的排放峰.秸秆与化肥配施较常规施肥(F)处理提高了土壤N_2O排放量,累积排放量及其排放系数,其中100FS处理的效果最为明显,辣椒季的累积排放通量明显高于莴笋季和卷心菜季,高达60.76 kg·hm~(-2)(P0.05),N_2O的排放系数(以N_2O-N/N计)为0.138 kg·kg-1,而秸秆与化肥减量配施较100FS处理可以降低氮肥的N_2O排放系数.与对照CK和F处理相比,70FS处理降低了土壤CO_2排放量和累积排放量,分别为55.28~1 831.62 mg·(m2·h)-1和7 502.13~25 988.55 kg·hm~(-2),而其他秸秆与化肥配施处理均增加了CO_2累积排放通量,尤其是60FS和50FS处理.对土壤CH_4排放而言,辣椒季的排放波动较大,除CK外,各处理的土壤CH_4累积排放量多为负值,表现为大气中CH_4汇;秸秆与化肥减量30%~50%配施处理均降低了辣椒季的土壤CH_4排放量和累积排放通量,而100FS处理提高了CH_4排放量和累积排放通量.与CK和F处理相比,除70FS外,100FS、60FS和50FS均显著提高了GWP.总体上,从温室气体排放角度,在常规化肥施用的基础上减量30%再与秸秆配施可以降低土壤CO_2和CH_4排放,缓解温室气体的增温潜势,而对土壤N_2O减排效果不显著.     

红壤丘陵区冬闲稻田CH4和N2O排放通量的研究

CH4和N2O是与全球气候变化密切相关的2种主要温室气体,其排放规律以及减排措施已成为当前研究的热点。休闲期抛荒稻田普遍存在于我国西南和南方地区,而对于其CH4和N2O排放规律的研究还比较少。本实验选取江西红壤丘陵区进行观测,于稻田休闲期采用静态箱-气相色谱法进行原位观测,旨在探讨休闲期CH4和N2O的排放规律,可为制定减排措施提供一定的依据。研究结果表明:红壤丘陵区冬闲稻田CH4和N2O平均排放通量(以CH4和N2O-N计)分别为0.03mg.m-2.h-1和3.27μg.m-2.h-1。冬闲期CH4和N2O平均排放通量与土温、降雨量无明显线性关系(P>0.05)。冬闲稻田排放CH4和N2O的综合温室效应(以CO2-eq计)为7.58 g.m-2,其中,CH4和N2O产生的温室效应(以CO2-eq计)分别为2.33和5.25 g.m-2。N2O排放量是冬闲稻田温室气体观测中不可忽视的部分。     

Home composting as an alternative treatment option for organic household waste in Denmark: An environmental assessment using life cycle assessment-modelling

An environmental assessment of the management of organic household waste (OHW) was performed from a life cycle perspective by means of the waste-life cycle assessment (LCA) model EASEWASTE. The focus was on home composting of OHW in Denmark and six different home composting units (with different input and different mixing frequencies) were modelled. In addition, incineration and landfilling was modelled as alternatives to home composting. The most important processes contributing to the environmental impact of home composting were identified as greenhouse gas (GHG) emissions (load) and the avoided emissions in relation to the substitution of fertiliser and peat when compost was used in hobby gardening (saving). The replacement of fertiliser and peat was also identified as one of the most sensible parameters, which could potentially have a significant environmental benefit. Many of the impact categories (especially human toxicity via water (HTw) and soil (HTs)) were affected by the heavy metal contents of the incoming OHW. The concentrations of heavy metals in the compost were below the threshold values for compost used on land and were thus not considered to constitute a problem. The GHG emissions were, on the other hand, dependent on the management of the composting units. The frequently mixed composting units had the highest GHG emissions. The environmental profiles of the home composting scenarios were in the order of −2 to 16 milli person equivalents (mPE) Mg⁻¹ wet waste (ww) for the non-toxic categories and −0.9 to 28 mPE Mg⁻¹ ww for the toxic categories. Home composting performed better than or as good as incineration and landfilling in several of the potential impact categories. One exception was the global warming (GW) category, in which incineration performed better due to the substitution of heat and electricity based on fossil fuels.     

A historical perspective of Global Warming Potential from Municipal Solid Waste Management

The Municipal Solid Waste Management (MSWM) sector has developed considerably during the past century, paving the way for maximum resource (materials and energy) recovery and minimising environmental impacts such as global warming associated with it. The current study is assessing the historical development of MSWM in the municipality of Aalborg, Denmark throughout the period of 1970 to 2010, and its implications regarding Global Warming Potential (GWP₁₀₀), using the Life Cycle Assessment (LCA) approach. Historical data regarding MSW composition, and different treatment technologies such as incineration, recycling and composting has been used in order to perform the analysis. The LCA results show a continuous improvement in environmental performance of MSWM from 1970 to 2010 mainly due to the changes in treatment options, improved efficiency of various treatment technologies and increasing focus on recycling, resulting in a shift from net emission of 618 kg CO₂-eq. tonne^?1 to net saving of 670 kg CO₂-eq. tonne^?1 of MSWM.     

Aktuelle und künftige Emissionen treibhauswirksamer fluorierter Verbindungen in Deutschland

Zusammenfassung  Die fluorierten Verbindungen Schwefelhexafluorid (SF₆), perfluorierte Fluorkohlenwasserstoffe (CF₄, C₂F₆) und wasserstoffhaltige Fluorkohlenwasserstoffe (H-FKW) z?hlen zu den atmosph?rischen Spurengasen mit extrem hohen Treibhauspotentialen. Untersucht werden für Deutschland ihre realen Emissionen für 1990–1995, und Prognosen für die Jahre bis 2020 werden aufgestellt. Diesen Prognosen zufolge vermindern sich die j?hrlichen Freisetzungen von CF₄/C₂F₆ von 1990 bis 2000 von 335 t/34 t auf 100 t/10 t infolge Automatisierungsma?nahmen an der Hauptquelle (Aluminiumhütten). Die Emissionen von SF₆ bleiben dagegen bis 2020 im Schwankungsbereich zwischen 200 und 300 t j?hrlich. Hauptemittenten sind nicht elektrische Schaltanlagen, da diese relativ dicht sind und über ein Entsorgungs-und Wiederaufarbeitungskonzept für gebrauchtes Gas verfügen, sondern mit gro?em Abstand Autoreifen und Schallschutzscheiben. Bei den erst seit 1990 gezielt als FCKW-Nachfolger eingesetzten H-FKW ist mit fortschreitender FCKW-Substitution in der station?ren und mobilen K?lte-und Klimatechnik, bei PU-Montageschaum und Asthmasprays mit einer sprunghaften Zunahme der Emissionen bis auf über 9700 t/a ab dem Jahr 2007 zu rechnen, sofern sich nicht halogenfreie Alternativen st?rker durchsetzen. Im Jahr 2020 werden bei Annahme dieser Trends die kumulierten Emissionen der genannten fluorierten Verbindungen der Treibhauswirkung von 25 Mio. t CO₂ entsprechen (GWP-Betrachtungszeitraum: 100 Jahre).