海洋中溴甲烷的研究进展

溴甲烷是大气中重要的痕量温室气体,对全球变暖和大气化学具有重要作用.海洋在溴甲烷的生物地球化学循环中作用复杂,海洋既是大气溴甲烷的源也是其汇,开展海洋环境中溶存溴甲烷的化学研究,对大气臭氧层的保护工作具有一定的指导意义,也可为在全球尺度上估算海洋环境中溴甲烷对全球环境变化的贡献提供理论依据.本文从溴甲烷的生物地球化学循环、分析测定方法、浓度分布、海-气通量、源汇平衡等方面综述了国内外海洋环境中溴甲烷的研究进展,探讨了目前该领域研究中存在的不足,并对未来的研究进行了展望.
     

垃圾填埋场氧化亚氮排放控制研究进展

填埋是国内外城市生活垃圾处理的一种主要方式.垃圾填埋场是温室气体氧化亚氮(N2O)和甲烷(CH4)的重要排放源.作为一种高效痕量的温室气体,N2O具有极高的潜在增温效应,其每分子潜在的增温作用是二氧化碳(CO2)的296倍.而且N2O能在大气中长期稳定存在,对臭氧层具有较强的破坏作用.本文针对垃圾填埋场N2O排放的控制研究,概述了垃圾填埋处理过程中主要排放源的N2O排放及其影响因素,提出了现阶段适应我国垃圾填埋场N2O排放控制的一系列措施,并展望了垃圾填埋场温室气体N2O排放控制理论和技术的研究方向.     

苏南丘陵区稻田氧化亚氮的排放特点

氧化亚氮（Ｎ２Ｏ）是一种重要的温室气体,又能破坏臭氧层［１,２］。土壤是大气Ｎ２Ｏ的主要来源［３］,研究结果表明,我国１９９０年排放的Ｎ２Ｏ有９２３６％来自于农田土壤。各种类型稻田Ｎ２Ｏ－Ｎ排放量占化肥施氮量的００３１％～０４８％［４,５］,稻...     

地表自然过程排汞研究进展及展望

地表自然过程排汞包括了自然源排汞过程和先前排放的汞沉降到地表后的再排放过程.已有证据显示,地表自然过程向大气的排汞量可能远大于人为活动直接向大气的排汞量.准确确定自然过程汞的释放通量,不仅对正确评价目前减少人为活动向大气排汞对全球环境汞污染的影响程度具有重要的意义,而且可为全球大气汞的减排政策的制定提供重要科学理论依据.本综述通过对国内外地表自然排放源相关文献的调研分析发现:由于缺少可靠的观测技术、对地表与大气间汞交换过程和机理的准确认识及大气汞沉降对地表自然排汞过程影响的认识还不清楚,因此目前还难以准确估算地表自然过程向大气的排汞量.近年来,随着技术手段的进步,已具备了开展地表自然排汞及先前排汞沉降后的再释放过程、机理和通量研究的可行性.地表自然过程排汞的研究将是汞的生物地球化学循环演化研究领域的前沿之一.     

我国自然源汞排放研究进展

由于特殊的物理化学性质,汞是唯一主要以气态单质形式存在于大气的重金属污染物,可通过大气环流进行全球性的传输。大气汞主要来自于人为活动和自然过程的汞排放。建立和优化全球和区域大气汞排放清单对研究全球大气汞的迁移转化规律及其环境健康效应具有重要意义。由于影响因素较为复杂,目前国内外自然源清单研究与人为源清单研究相比较为滞后。我国约十分之一的国土面积位于环太平洋汞矿化带上,且我国主要自然源汞排放通量与欧洲和北美同类型地区相比偏高。近些年来,国内研究人员在自然源汞排放研究领域开展了大量的研究工作,为建议和优化我国的自然源汞排放清单提供了重要的科学依据。本文总结了近年来我国自然源汞排放的研究进展,分析水体、土壤和植被等自然源汞排放通量分布规律、内在机理和影响因素;同时对我国自然源汞排放存在的不足及未来需要开展的工作进行了展望。     

植物源挥发性有机物的生态意义(综述)

植物释放的挥发性有机气体(volatile organic compounds, VOCs)在对流层大气中通过一系列氧化还原反应,改变大气的化学组成,对臭氧合成、一氧化碳生成、甲烷氧化等有重要作用,其氧化物质对区域乃至全球的环境和气候都产生一定的影响。本文综述植物释放的VOCs对大气化学、温室效应、光化学烟雾的影响;介绍VOCs释放机制、合成途径及排放速率;对今后研究方向和大面积种植林木、城市绿化提出建议。     

大气臭氧层减薄、地表紫外辐射增强与植物的响应

臭氧层减薄、温室效应和酸雨是人类面临的全球性环境问题 ,并受到了广泛的重视。本文主要论述大气臭氧层减薄引起的地表紫外辐射增强 ,以及对植物的影响。1 　大气臭氧层减薄与地表紫外辐射增强大气臭氧层能吸收强烈的太阳紫外辐射 ,使地球生物得以正常生长 ,从而成为地球生命的有效保护层。二十多年前 ,人们注意到平流层臭氧衰减 〔1〕,近十年全球臭氧层平均减少了 2 %～ 3% ,并且还在加剧。臭氧层快速减薄已经通过卫星得到证实 ,最明显的减薄发生在南极大陆上空 ,在春季 ,衰减率高达71 % 〔2〕。过去十年我国北京香河和昆明两个监测站的监…     

垃圾填埋场N_2O排放通量及测定方法研究进展

氧化亚氮(N2O)是第三大温室气体和最主要的臭氧层破坏气体.填埋是目前城市生活垃圾处理处置的主要方式,而垃圾填埋场是N2O的排放源之一.实验室研究和现场测定均表明,生活垃圾填埋场可以有高的N2O释放通量,但不同填埋场测定数据差异很大.目前,对生活垃圾填埋场N2O排放量的原位准确测定以及排放机理和重要性的认识仍有很多不足.本文概述了生活垃圾填埋场N2O排放研究现状,从垃圾堆体和覆土层两部分探讨了传统厌氧卫生填埋场的N2O产生和排放机理,并就此对新型脱氮型生物反应器填埋场做了相应探讨.最后,就静态箱法、涡度相关法等N2O通量测定方法在填埋场的适用性进行了讨论,并展望了填埋场N2O排放的研究方向.     

陆地生态系统卤甲烷释放特点及其生态意义

大气卤甲烷与平流层臭氧破坏密切相关,并参与光化学反应,还具有一定的．温室效应和污染毒害作用。研究发现：(1)大气CH3Cl和CH3Br存在巨大的未知源,它们的已知源分别仅占已知汇的大约1／2～2／3和60％。而CH3I的源和汇还都不确切;(2)陆地生态系统有可能是最大的卤甲烷自然释放源;(3)生物合成和土壤非生物生产是陆地生态系统卤甲烷生产的两个主要途径;(4)沿海湿地、水稻田、热带森林等陆地生态系统是卤甲烷主要释放源;(5)陆地生态系统卤甲烷的自然释放可能在生物竞争、生物代谢和大气环境污染方面具有重要的生态意义;(6)随着大气卤甲烷人为释放源的控制,其自然释放源的相对重要性将更加突出。提出了当前陆地生态系统卤甲烷释放研究的重点方向以及我国开展相关研究的重要意义。     

名刊封面

地球的大气圈大致可分为对流层、平流层(同温层)、中间层和热层4层。大气中的臭氧层主要位于对流层顶部和平流层中,是地球的一道生命防线,它吸收了太阳光中的大部分紫外线,使阳光到达地面时,紫外线辐射大大减弱。如果没有臭氧层的保护,人类将会面临很多问题。1985年南极上空臭氧层空洞的发现让科学家一直很关注这个问题,他们对空洞形成的原因进行了很多研究。     

Genetic control of methyl halide production in Arabidopsis

Methyl chloride (CH(3)Cl) and methyl bromide (CH(3)Br) are the primary carriers of natural chlorine and bromine, respectively, to the stratosphere, where they catalyze the destruction of ozone, whereas methyl iodide (CH(3)I) influences aerosol formation and ozone loss in the boundary layer. CH(3)Br is also an agricultural pesticide whose use is regulated by international agreement. Despite the economic and environmental importance of these methyl halides, their natural sources and biological production mechanisms are poorly understood. Besides CH(3)Br fumigation, important sources include oceans, biomass burning, tropical plants, salt marshes, and certain crops and fungi. Here, we demonstrate that the model plant Arabidopsis thaliana produces and emits methyl halides and that the enzyme primarily responsible for the production is encoded by the HARMLESS TO OZONE LAYER (HOL) gene. The encoded protein belongs to a group of methyltransferases capable of catalyzing the S-adenosyl-L-methionine (SAM)-dependent methylation of chloride (Cl(-)), bromide (Br(-)), and iodide (I(-)) to produce methyl halides. In mutant plants with the HOL gene disrupted, methyl halide production is largely eliminated. A phylogenetic analysis with the HOL gene suggests that the ability to produce methyl halides is widespread among vascular plants. This approach provides a genetic basis for understanding and predicting patterns of methyl halide production by plants.     

Effects of grassland management on the emission of methane from intensively managed grasslands on peat soil

Methane (CH4) is the most important greenhouse gas next to CO2 and as such it contributes to the enhanced greenhouse effect. Peat soils are often considered as sources of CH4. Grasslands on the other hand are generally considered to be a net sink for atmospheric CH4. The aim of this study was twofold: (i) to quantify the net CH4 emission of intensively managed grasslands on peat soil in the Netherlands; and (ii) to assess the effects of grassland management, i.e. drainage, nitrogen (N) fertilization, and grazing versus mowing, on CH4 emission rates. Net CH4 emissions were measured weekly or biweekly for one year with vented closed flux chambers at two sites, one with a mean ground water level of 22 cm below surface and one with a mean ground water level of 42 cm. On each site there were three treatments: mowing without N application, mowing with N application, and grazing with N application. The dominating species was perennial ryegrass (Lolium perenne L.). Net CH4 emissions were low, in general in the range of -0.2 to 0.2 mg CH4 m-2 d-1. In the relatively warm summer of 1994, consumption of atmospheric CH4 peaked at 0.4 mg m-2 d-1. On an annual basis, the sites were net consumers of atmospheric CH4. However, the consumption was small: 0.31 to 0.08 kg CH4 ha-1 yr-1. Effect of mean ground water level was significant, but small. There were no significant effects of withholding N fertilization for some years and grazing versus mowing on net CH4 emissions. We conclude that grassland management of intensively managed grasslands on peat soil is not a suitable tool for reducing net CH4 emissions.     

Spatial and temporal assessment of sources contributing to the annual austral spring mid-tropospheric ozone maxima over the tropical South Atlantic

The primary source of the annual austral spring mid‐tropospheric ozone maxima over the tropical South Atlantic has generally been assumed to be biomass burning. However, ozone precursor emissions from biogenic, lightning, and anthropogenic sources in subequatorial Africa before and during the ozone peak are shown to be comparable, if not greater, in magnitude to regional biomass burning production. Moreover, an investigation of the spatial and temporal characteristics of these ozone precursor sources (i.e. vegetative and microbial activity, lightning‐induced generation, and anthropogenic emissions) suggests that these alternative sources can potentially make a substantial contribution to the seasonal ozone peak. This argument is supported by the practical limitations of atmospheric transport available to regionally produced ozone and ozone precursors.     

Description of toluene inhibition of methyl bromide biodegradation in seawater and isolation of a marine toluene oxidizer that degrades methyl bromide

Methyl bromide (CH3Br) and methyl chloride (CH3Cl) are important precursors for destruction of stratospheric ozone, and oceanic uptake is an important component of the biogeochemical cycle of these methyl halides. In an effort to identify and characterize the organisms mediating halocarbon biodegradation, we surveyed the effect of potential cometabolic substrates on CH3Br biodegradation using a 13CH3Br incubation technique. Toluene (160 to 200 nM) clearly inhibited CH3Br and CH3Cl degradation in seawater samples from the North Atlantic, North Pacific, and Southern Oceans. Furthermore, a marine bacterium able to co-oxidize CH3Br while growing on toluene was isolated from subtropical Western Atlantic seawater. The bacterium, Oxy6, was also able to oxidize o-xylene and the xylene monooxygenase (XMO) pathway intermediate 3-methylcatechol. Patterns of substrate oxidation, lack of acetylene inhibition, and the inability of the toluene 4-monooxygenase (T4MO)-containing bacterium Pseudomonas mendocina KR1 to degrade CH3Br ruled out participation of the T4MO pathway in Oxy6. Oxy6 also oxidized a variety of toluene (TOL) pathway intermediates such as benzyl alcohol, benzylaldehyde, benzoate, and catechol, but the inability of Pseudomonas putida mt-2 to degrade CH3Br suggested that the TOL pathway might not be responsible for CH3Br biodegradation. Molecular phylogenetic analysis identified Oxy6 to be a member of the family Sphingomonadaceae related to species within the Porphyrobacter genus. Although some Sphingomonadaceae can degrade a variety of xenobiotic compounds, this appears to be the first report of CH3Br degradation for this class of organism. The widespread inhibitory effect of toluene on natural seawater samples and the metabolic capabilities of Oxy6 indicate a possible link between aromatic hydrocarbon utilization and the biogeochemical cycle of methyl halides.     

开放式空气CO2增高对稻田CH4和N2O排放的影响

在FACE(free aircarbondioxideenrichment)平台上 ,采用静态暗箱 气相色谱法观测研究了大气CO2 浓度增加对稻田CH4和N2 O排放的影响 .结果表明 ,在 15 0和 2 5 0kgN·hm-2 两种氮肥水平下大气CO2 浓度增加 2 0 0 μmol·mol-1均明显促进水稻生长 ,水稻生物量积累 .大气CO2 浓度增加对 15 0和 2 5 0kgN·hm-2 两种氮肥水平下稻田CH4排放均无显著影响 ,并简要分析了与现有文献报道结果不一致的原因 .大气CO2 浓度增加也未导致 15 0和 2 5 0kgN·hm-2 两种氮肥水平下稻田N2 O排放的明显变化 ,与大多数研究结果一致 .     

Impact of nitrogen and climate change interactions on ambient air pollution and human health

Nitrogen oxides (NO_x) are important components of ambient and indoor air pollution and are emitted from a range of combustion sources, including on-road mobile sources, electric power generators, and non-road mobile sources. While anthropogenic sources dominate, NO_x is also formed by lightning strikes and wildland fires and is also emitted by soil. Reduced nitrogen (e.g., ammonia, NH₃) is also emitted by various sources, including fertilizer application and animal waste decomposition. Nitrogen oxides, ozone (O₃) and fine particulate matter (PM_2.5) pollution related to atmospheric emissions of nitrogen (N) and other pollutants can cause premature death and a variety of serious health effects. Climate change is expected to impact how N-related pollutants affect human health. For example, changes in temperature and precipitation patterns are projected to both lengthen the O₃ season and intensify high O₃ episodes in some areas. Other climate-related changes may increase the atmospheric release of N compounds through impacts on wildfire regimes, soil emissions, and biogenic emissions from terrestrial ecosystems. This paper examines the potential human health implications of climate change and N cycle interactions related to ambient air pollution.     

Characterisation factors for greenhouse gases at a midpoint level including indirect effects based on calculations with the IMAGE model

Background, Aims and Scope  

The traditional method of using Global Warming Potentials (GWPs) to assess the effects of climate change in Life Cycle Assessment (LCA) does not account for indirect atmospheric effects like saturation effects and emissions of ozone precursors. The aim of this paper is to provide GWP values for LCA purposes of the most important climate related gases including indirect effects and assess whether these values are dependent of different background conditions and size of change in emissions fluxes.     

Stratospheric ozone depletion due to nitrous oxide: influences of other gases

The effects of anthropogenic emissions of nitrous oxide (N(2)O), carbon dioxide (CO(2)), methane (CH(4)) and the halocarbons on stratospheric ozone (O(3)) over the twentieth and twenty-first centuries are isolated using a chemical model of the stratosphere. The future evolution of ozone will depend on each of these gases, with N(2)O and CO(2) probably playing the dominant roles as halocarbons return towards pre-industrial levels. There are nonlinear interactions between these gases that preclude unambiguously separating their effect on ozone. For example, the CH(4) increase during the twentieth century reduced the ozone losses owing to halocarbon increases, and the N(2)O chemical destruction of O(3) is buffered by CO(2) thermal effects in the middle stratosphere (by approx. 20% for the IPCC A1B/WMO A1 scenario over the time period 1900-2100). Nonetheless, N(2)O is expected to continue to be the largest anthropogenic emission of an O(3)-destroying compound in the foreseeable future. Reductions in anthropogenic N(2)O emissions provide a larger opportunity for reduction in future O(3) depletion than any of the remaining uncontrolled halocarbon emissions. It is also shown that 1980 levels of O(3) were affected by halocarbons, N(2)O, CO(2) and CH(4), and thus may not be a good choice of a benchmark of O(3) recovery.