长春城市水体夏秋季温室气体排放特征

为掌握我国东北地区城市湖泊水体温室气体的释放/吸收特征,本研究分别于夏季和秋季,对位于吉林省长春市的7个城市湖泊(南湖、北湖、雁鸣湖、胜利公园、地理所内湖、天嘉公园和长春公园)表层水中的CO_2和CH_4分压[p(CO_2)和p(CH_4)]进行了监测,并对影响p(CO_2)和p(CH_4)季节变化的相关环境和水质参数进行了分析.研究结果表明在夏季和秋季这7个城市湖泊表层水体中CH_4都处于过饱和状态;除夏季的南湖和胜利公园内湖,其它湖泊CO_2也都处于过饱和状态,且不同湖泊间的温室气体分压具有显著性差异(P0.05),通量也同样具有显著性差异(P0.05).除了南湖和胜利公园内湖外,其它各湖泊在夏秋季节都是大气CO_2和CH_4的"源",且对大气中温室气体的贡献都以CO_2为主.环境参数与p(CO_2)或p(CH_4)之间的相关性分析表明,在夏季,城市湖泊表层水体中p(CO_2)和p(CH_4)都与日照时数呈显著负相关(r_(p(CO_2))=-0.48,P0.05;r_(p(CH_4))=-0.63,P0.01),日照时数通过影响水生植物的光合作用进而影响水体中CO_2和溶解氧浓度,p(CH_4)还与降水量呈显著正相关(r_(p(CH_4))=0.44,P0.05);在秋季,p(CO_2)与气温呈显著负相关(r_(p(CO_2))=-0.39,P0.05).另外,水质参数与p(CO_2)和p(CH_4)的相关性分析表明,这些城市湖泊表层水体的p(CO_2)和p(CH_4)都与水体pH显著负相关(r_(p(CO_2))=-0.51,r_(p(CH_4))=-0.82,P0.01),与盐度显著正相关(r_(p(CO_2))=0.38,P0.05;r_(p(CH_4))=0.75,P0.01),p(CH_4)还与水体DOC、TN和TP均具有显著相关性(P0.01).从研究结果可以推测在这7个富营养城市湖泊中,水体的营养物水平及其所决定的浮游植物生物量并不是影响表层水体p(CO_2)的最主要因素,而日照时数、水体pH和盐度与夏秋季表层水体中的p(CO_2)和p(CH_4)有较大关联.     

有机硫恶臭物质采样和分析检测技术研究

本研究以二甲二硫醚和甲硫醇为代表对有机硫恶臭物质的采样浓缩,热解析和ＧＣ,ＧＣ／ＭＳ的色谱分离,定性鉴定和定量检测方法进行了实验技术研究。与此同时研制开发了恶臭污染监测的系列配套装置－采样管,微型采样泵,热解析色谱进行装置和标准气体物质发生装置。经筛选确认,国产ＧＤＸＥ１０５采样管可对ＤＭＤＳ和ＣＨ３ＳＨ实现直接常温采样浓缩,样品回收率分别为１００％和６０％。ＧＣ／ＦＰＤ对二种硫化物的检出下限分别     

卫河新乡市区段春季溶解CH4与N2O浓度特征

对卫河新乡市区段春季CH_4与N_2O浓度进行调查分析,初步探讨了城市河流中典型温室气体的溶存量空间变化及其影响因素.结果表明,受到水中污染物质浓度及人类活动影响,春季卫河表层水中CH_4与N_2O浓度处于超饱和状态,饱和度分别为147.59~2 667.85和4.06~188.25.影响市区内N_2O浓度的主要环境因素为NH~+_4-N(P0.01),而新区污水处理厂排水输入显著提高了N_2O的溶存量,说明污染物类型影响温室气体的产生和积累,NH~+_4-N的硝化过程是城市河流N_2O产生的主要来源.逐步回归分析表明CH_4浓度是NH~+_4-N浓度与水温的相关函数,其中CH_4浓度与NH~+_4-N极显著相关(R2=0.70,P0.01),说明春季卫河中NH~+_4-N浓度是影响卫河春季CH_4溶存的关键因素.此外研究结果显示在NO~-_3-N浓度较低并且NH~+_4-N浓度高时水中CH_4与N_2O浓度具有显著正相关关系,表明有效态氮浓度差异影响CH_4与N_2O产生过程的耦合机制.     

Responses of greenhouse gas fluxes to experimental warming in wheat season under conventional tillage and no-tillage fields

Understanding the effects of warming on greenhouse gas(GHG, such as N_2O, CH_4 and CO_2 )feedbacks to climate change represents the major environmental issue. However, little information is available on how warming effects on GHG fluxes in farmland of North China Plain(NCP). An infrared warming simulation experiment was used to assess the responses of N_2O, CH_4 and CO_2 to warming in wheat season of 2012–2014 from conventional tillage(CT) and no-tillage(NT) systems. The results showed that warming increased cumulative N_2O emission by 7.7% in CT but decreased it by 9.7% in NT fields(p 0.05). Cumulative CH_4 uptake and CO_2 emission were increased by 28.7%–51.7% and 6.3%–15.9% in both two tillage systems,respectively(p 0.05). The stepwise regressions relationship between GHG fluxes and soil temperature and soil moisture indicated that the supply soil moisture due to irrigation and precipitation would enhance the positive warming effects on GHG fluxes in two wheat seasons.However, in 2013, the long-term drought stress due to infrared warming and less precipitation decreased N_2O and CO_2 emission in warmed treatments. In contrast, warming during this time increased CH_4 emission from deep soil depth. Across two years wheat seasons, warming significantly decreased by 30.3% and 63.9% sustained-flux global warming potential(SGWP) of N_2O and CH_4 expressed as CO_2 equivalent in CT and NT fields, respectively. However, increase in soil CO_2 emission indicated that future warming projection might provide positive feedback between soil C release and global warming in NCP.     

Choice of precipitant and calcination temperature of precursor for synthesis of NiCo2O4 for control of CO–CH4 emissions from CNG vehicles

Compressed natural gas(CNG)is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants(Na_2CO_3,KOH and urea)for nickel cobaltite(Ni Co_2O_4)catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400°C.The catalysts were used for oxidation of a mixture of CO and CH_4(1:1).The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na_2CO_3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH_4mixture at the lowest temperature(T_(100)=350°C).Whereas,for catalyst prepared using urea,T_(100)=362°C.On the other hand the conversion of CO-CH_4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400°C.Further,the effect of higher calcination temperatures of 500 and600°C was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410°C over catalysts calcined at 500 and 600°C respectively.Thus,the best precipitant established was Na_2CO_3and the optimum calcination temperature of 400°C was found to synthesize the Ni Co_2O_4catalyst for the best performance in CO-CH_4oxidation.     

亏缺灌溉对冬小麦农田温室气体排放的影响

为研究不同时期亏水量对冬小麦农田土壤温室气体排放的影响,优化灌溉管理措施,试验采用静态箱-气相色谱法对关中平原冬小麦(2016年10月～2017年6月)农田温室气体(CO_2、N_2O和CH_4)排放通量进行了监测研究.试验在冬小麦3个生育期(越冬期、拔节至抽穗期、抽穗至灌浆期)各设置3个灌水水平(充分灌溉,100%;轻度水分亏缺,80%;重度水分亏缺,60%),共6个处理(CK、T1、T2、T3、T4、T5,其中CK处理为充分灌溉处理,其它处理均为不同程度的水分亏缺处理).阐述了3种气体(CO_2、N_2O和CH_4)在全生育期的动态变化特征,并用作物产量、长远增温效应(net GWP_L)和当季增温效应(net GWPS)这3个指标综合评估不同生育期亏水水平对关中平原小麦经济效应和生态效应的影响.结果表明,生育期灌溉后CO_2、N_2O排放通量基本上呈增加趋势,以CK处理最高,而灌溉后土壤CH_4吸收通量迅速减小,高水分处理甚至出现排放特征.与CK处理相比,T1、T2、T3、T4和T5处理下小麦季CO_2排放总量分别显著降低了13. 32%、25. 98%、5. 55%、15. 47%和17. 52%(P 0. 05),N_2O排放总量分别显著降低了12. 20%、18. 00%、5. 63%、11. 54%和13. 53%(P 0. 05),CH_4吸收总量分别显著增加了46. 47%、75. 78%、19. 47%、53. 40%和62. 33%(P 0. 05); T1、T2、T3、T4和T5处理net GWP_L较CK处理分别显著降低了10. 07%、12. 77%、6. 50%、6. 81%和11. 53%(P 0. 05);除T3处理外,其他处理较CK处理net GWPS分别显著降低了13. 21%、37. 65%、24. 60%和19. 86%(P 0. 05); T1、T2、T3、T4和T5处理小麦产量较CK处理分别显著减少了12. 56%、32. 53%、2. 25%、20. 93%和18. 14%(P 0. 05),T3处理较CK处理减产2. 25%,但无显著性差异(P 0. 05).亏缺灌溉显著降低了小麦地温室气体的排放,但会造成不同程度的减产,综合考虑不同生育期亏水水平处理下小麦地的经济效应和生态效应,T3处理更有利于关中平原冬小麦的保产节水减排.     

三峡库区香溪河秋末至中冬CO2和CH4分压特征分析

为揭示三峡库区支流库湾表层水体秋末至中冬CH_4和CO_2的分压特征及其影响因素,于2014年相应时间段在香溪河库湾每天定点定时采取表层水样,利用顶空气相色谱技术测定水中溶解CH_4和CO_2的浓度,通过亨利定律计算CH_4和CO_2的分压,并同步监测相关环境因子.结果表明,表层水体CH_4分压变化范围0.64~4.43 Pa,平均值为(1.69±0.94)Pa,CO_2分压变化范围49.90~868.91 Pa,平均值为(328.48±251.63)Pa.水体CO_2和CH_4分压的变化呈显著负相关(r=-0.618,P0.01),p CH_4和p CO_2与溶解氧、总磷、叶绿素a、p H水温和水位相关性明显,其中p CO_2与各环境因子的相关性较p CH_4更为密切.     

Characteristics of greenhouse gas emission in three full-scale wastewater treatment processes

Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of greenhouse gases （GHG）, including carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N2O）. Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4： the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A^2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.     

保护性耕作对后茬冬小麦土壤CO2和N2O排放的影响

为研究保护性耕作对后茬冬小麦土壤CO2和N2O排放的影响,在前茬进行常规耕作(T)、免耕(NT)、免耕+秸秆覆盖(NTS)、常规耕作+秸秆施用(TS)这4种处理,采用静态箱-气相色谱法分析土壤CO2和N2O排放通量.结果表明,保护性耕作没有改变后茬土壤CO2和N2O排放的季节性规律,对冬小麦生物量无明显影响;保护性耕作显著减少了土壤CO2和N2O累积排放量.与T相比,TS、NT、NTS的全生育期土壤CO2累积排放量分别降低了5.95%(P=0.132)、12.94%(P=0.007)和13.91%(P=0.004),土壤N2O累积排放量分别减少了31.23%(P=0.000)、61.29%(P=0.000)和33.08%(P=0.000).本研究表明免耕与秸秆施用能减少后茬作物生长季土壤的CO2和N2O排放量.     

The role of CH4 and N2O emission reductions in the cost-effective control of the greenhouse gas emissions from Finland

The reduction of carbon dioxide (CO₂) emissions may be quite expensive and it is necessary to consider reduction measures for other anthropogenic greenhouse gases, such as methane (CH₄) and nitrous oxide (N₂O) as well. Their contribution to the total GHG emission from Finland is about 15–20%. In Finland most of the CH₄ emissions are due to waste management, agriculture and burning processes. N₂O emissions originate from burning processes, agriculture, industry and atmospheric deposition of nitrogen. The cost-effective reduction of the Finnish GHG emissions has been studied with the EFOM-ENV model, which is a quasi-dynamic linear energy system optimisation model. The target function to be minimised is the total discounted cost for the modelled system. In this study the model has been expanded to cover all well-known anthropogenic CO₂, CH₄ and N₂O sources and reduction measures. The results indicate it is economic to reduce the emissions of CO₂, CH₄ and N₂O in Finland. It is profitable to exploit the economic reduction potential of CH₄ and N₂O, because then the abatement of CO₂ emissions does not need to be as extensive as when the reduction is aimed only at CO₂ emissions. The inclusion of CH₄ and N₂O decreases the annual reduction costs about 20% in the year 2010.     

生物炭添加对半干旱地区土壤温室气体排放的影响

为确定生物炭添加对半干旱地区农田土壤温室气体释放的影响,采用小区定位试验,利用锯末(J)和槐树皮(H)及3种添加比例(1%、3%、5%,质量百分比),研究了生物炭添加6个月内表层土壤CO2、CH4和N2O等3种温室气体排放的动态变化.结果表明,与对照相比,各处理土壤CO2排放通量随生物炭的添加呈现增加的趋势,锯末和槐树皮等两种生物炭处理的土壤CO2平均排放通量分别增加了1.89%和3.34%,但差异不显著.CH4排放随着生物炭添加量的增加而降低,各生物炭处理的土壤表层CH4排放量平均降幅分别为:J1:1.17%、J3:2.55%、J5:4.32%、H1:2.35%、H3:5.83%、H5:7.32%.其中,锯末生物炭仅在5%添加量时较对照差异显著(P0.05),而槐树皮生物炭处理在3%和5%的添加量与对照差异均达显著水平(P0.05).生物炭对N2O的排放影响没有明显规律性.研究表明,生物炭在短期内对半干旱地区农田土壤CO2和N2O的排放没有显著影响,而对CH4排放则影响显著(P0.05).就生物炭类型而言,槐树皮生物炭在抑制CH4排放方面优于锯末生物炭,差异显著(P=0.048).     

Greenhouse gas emissions from oilfield-produced water in Shengli Oilfield, Eastern China

Greenhouse gas(GHG) emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield,the second largest oilfield in China. The results showed that methane(CH4) and carbon dioxide(CO2) were the primary gases released naturally from the oilfield-produced water.The atmospheric temperature and release time played important roles in determining the CH4 and CO2emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2was released from the oilfield-produced water during the first release period, 0–2 hr, for each temperature, with a maximum average emission rate of 0.415 g CH4/(m3·hr) and 3.934 g CO2/(m3·hr), respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems.     

Elevated atmospheric CO2 and drought effects on leaf gas exchange properties of barley

Atmospheric CO₂ concentration (C_a) is rising, predicted to cause global warming, and alter precipitation patterns. During 1994, spring barley (Hordeum vulgare L. cv. Alexis) was grown in a strip-split-plot experimental design to determine the effects that the main plot C_a treatments [A: Ambient at 370 μmol (CO₂) mol⁻¹; E: Enriched with free-air CO₂ enrichment (FACE) at ∼550 μmol (CO₂) mol⁻¹] had on several gas exchange properties of fully expanded sunlit primary leaves. The interacting strip-split-plot irrigation treatments were Dry or Wet [50% (D) or 100% (W) replacement of potential evapotranspiration] at ample nitrogen (261 kg N ha⁻¹) and phosphorous (29 kg P ha⁻¹) fertility. Elevated C_a facilitated drought avoidance by reducing stomatal conductance (g_s) by 34% that conserved water and enabled stomata to remain open for a longer period into a drought. This resulted in a 28% reduction in drought-induced midafternoon depression in net assimilation rate (A). Elevated C_a increased A by 37% under Dry and 23% under Wet. Any reduction in A under Wet conditions occurred because of nonstomatal limitations, whereas under Dry it occurred because of stomatal limitations. Elevated C_a increased the diurnal integral of A (A′) that resulted in an increase in the seasonal-long integral of A′ (A″) for barley leaves by 12% (P = 0.14) under both Dry and Wet - 650, 730, 905 and 1020 ± 65 g (C) m⁻² y⁻¹ for AD, ED, AW and EW treatments, respectively. Elevated C_a increased season-long average dry weight (DW_S; crown, shoots) by 14% (P = 0.02), whereas deficit irrigation reduced DW_S by 7% (P = 0.06), although these values may have been affected by a short but severe pea aphid [Acyrthosiphon pisum (Harris)] infestation. Hence, an elevated-C_a-based improvement in gas exchange properties enhanced growth of a barley crop.     

河流氧化亚氮产生和排放研究综述

氧化亚氮(N2O)是仅次于二氧化碳(CO2)和甲烷(CH4)的重要温室气体.由于人类活动对土地的影响导致河流系统中氮的可利用性增加,河流生态系统的N2O排放量正日益增长.本文对国内外河流水体N2O溶存浓度和饱和度、水-气界面排放通量及沉积物-水界面交换通量等数据进行了收集,并总结和分析了河流生态系统中N2O的产生机制及主要影响因子.     

长江口盐沼带湿地生态演替过程中甲烷排放研究

甲烷(CH4)作为河口湿地碳循环的重要中间产物,是大气中仅次于二氧化碳(CO2)的第二大温室气体,其排放清单对于全球气候变暖趋势的预测具有重要意义.因此,本研究采用静态箱-气相色谱技术,针对长江口盐沼带湿地CH4的排放通量展开了为期2年、每月1次的现场观测.研究结果表明,长江口盐沼带湿地持续表现为大气CH4的净排放源,其中,2011年在海三棱藨草覆盖情况下,全年CH4平均排放通量达到了1.00 mg·m-2·h-1,2012年互花米草大规模入侵后,海三棱藨草生物量显著减小,全年CH4排放通量减小为0.55 mg·m-2·h-1.Pearson相关性分析表明,沉积物有机碳含量、光合有效辐射及含水率等均不是影响长江口盐沼带湿地CH4排放的重要环境因子.在2011年,海三棱藨草生物量(p=0.001,r=0.928)、气温(p0.01,r=0.432)均与CH4排放通量呈现显著正相关,全年CH4最大排放通量出现在生物量最大的夏季8月份;2012年随着互花米草的入侵,CH4排放通量在5月份达到了最大值,自5月份之后逐渐减小,互花米草的入侵使长江口中潮滩盐沼带湿地CH4排放通量整体呈现出了下降的趋势.     

碳底物含量对厌氧条件下水稻土N2、N2O、NO、CO2和CH4排放的影响

理解底物碳氮对厌氧条件下水稻土排放氮素气体——氮气(N2)、氧化亚氮(N2O)和一氧化氮(NO)以及二氧化碳(CO2)和甲烷(CH4)的影响,有助于制定合理的温室气体减排措施,定量了解反硝化产物组成对碳底物水平的依赖性,也有助于氮转化过程模型研发中制定正确的关键过程参数选取方法或参数化方案.本研究采用粉砂壤质水稻土为研究对象,设置对照(CK)和加碳(C+)两个处理,前者的初始硝态氮和可溶性有机碳(DOC)含量分别为~50 mg·kg-1和~28 mg·kg-1,后者的分别为~50 mg·kg-1和~300 mg·kg-1.采用氦环境培养-气体及碳氮底物直接同步测定系统,研究了完全厌氧条件下碳底物水平对上述气体排放的影响.结果表明,CK处理无CH4排放,而C+处理可观测到CH4排放;C+处理的综合增温潜势显著高于CK处理(P<0.01);NO、N2O和N2排放量占这3种氮素气体排放总量的比重,在CK处理分别约为9%、35%和56%,在C+处理分别约为31%、50%和19%,处理间差异显著(P<0.01).由此表明,碳底物水平可显著改变所排放氮素气体的组成;对于旱地阶段硝态氮比较丰富的水稻土,避免在淹水前或淹水期间施用有机肥,有利于削减温室气体排放.     

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.     

Methane and nitrous oxide emissions from a subtropical coastal embayment (Moreton Bay, Australia)

Surface water methane (CH₄) and nitrous oxide (N₂O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH₄ and N₂O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH₄ and N₂O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH₄ varied between 500% and 4000% saturation while N₂O varied between 128 and 255% in the two bays. Average seasonal CH₄ fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH₄/(m²·day) while N₂O varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N₂O/(m²·day). Weighted emissions (t CO₂-e) were 63%-90% N₂O dominated implying that a reduction in N₂O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas (GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH₄ and N₂O and puts the estimated fluxes into the global context with measurements done from other climatic regions.     

模拟酸雨对福州平原水稻田温室气体排放的影响

农田生态系统是温室气体的重要排放源,研究酸雨对水稻田温室气体排放及其综合增温潜势的影响,对我国酸雨背景下农田生态系统固碳减排具有重要的现实意义.本文以福州平原水稻田为研究区,通过模拟酸雨探讨其对水稻田CO_2、CH_4和N_2O排放通量及其综合增温潜势的影响.结果表明:模拟酸雨并未显著改变早、晚稻田CO_2、CH_4和N_2O排放的季节变化规律,但降低了其排放通量.与对照组相比,pH=4.5酸雨作用下,早稻田CO_2、CH_4和N_2O平均排放通量依次降低11.54%、133.33%和22.22%,晚稻田CO_2和N_2O平均排放通量依次降低39.53%、156.00%,而CH_4平均排放通量与对照组差异不显著;pH=3.5酸雨作用下,早稻田CO_2、CH_4和N_2O平均排放通量分别降低10.82%、75.00%、54.00%,晚稻田平均排放通量分别降低17.32%、20.00%和197.67%.综合增温潜势表明,CO_2的增温潜势显著高于CH_4和N_2O,是稻田生态系统中温室效应的主要温室气体,在pH=4.5和pH=3.5的酸雨作用下,早、晚稻田生态系统温室气体综合增温潜势均降低.     

猪粪化肥配施对双季稻田CH4和N2O排放及其全球增温潜势的影响

以湖南典型红壤双季稻田系统为研究对象,采用静态箱-气相色谱法研究了水稻生长季基肥配施猪粪条件下CH4和N2O的排放特征,并估算了排放的CH4和N2O的全球增温潜势(GWP).结果表明,与施用化肥处理相比,猪粪化肥配施对稻田CH4和N2O排放的季节变化模式无明显影响,但影响其排放量大小.两个稻季,猪粪替代50%化学氮肥处理(1/2N+PM)CH4累积排放量较不施氮肥处理(0N)、50%化学氮肥处理(1/2N)、100%化学氮肥处理(N)分别提高54.83%、33.85%和43.30%(P<0.05);1/2N+PM处理N2O累积排放量较N处理显著降低67.50%,较0N处理、1/2N处理分别提高129.43%、119.23%(P<0.05).水稻生长季CH4是GWP的主要贡献者,占CH4和N2O综合GWP的99%以上.1/2N+PM处理的GWP显著高于其他处理(P<0.05),且1/2N+PM处理单位产量GWP最高,较N处理、1/2N处理、0N处理分别提高58.21%、26.82%、20.63%.因此,双季稻田猪粪替代部分化学氮肥较全部施用化学氮肥增加了双季稻田CH4和N2O排放的综合温室效应,其对温室气体排放的影响需在区域温室气体排放清单中加以考虑.