Field measurements of NO and NO2 emissions from fertilized and unfertilized soils

Field measurements of NO and NO₂ emissions from soils have been performed in Finthen near Mainz (F.R.G.) and in Utrera near Seville (Spain). The applied method employed a flow box coupled with a chemiluminescent NO _x detector allowing the determination of minimum flux rates of 2 g N m^-2 h^-1 for NO and 3 g m^-2 h^-1 for NO₂.The NO and NO₂ flux rates were found to be strongly dependent on soil surface temperatures and showed strong daily variations with maximum values during the early afternoon and minimum values during the early morning. Between the daily variation patterns of NO and NO₂, there was a time lag of about 2 h which seem to be due to the different physico-chemical properties of NO and NO₂. The apparent activation energy of NO emission calculated from the Arrhenius equation ranged between 44 and 103 kJ per mole. The NO and NO₂ emission rates were positively correlated with soil moisture in the upper soil layer.The measurements carried out in August in Finthen clearly indicate the establishment of NO and NO₂ equilibrium mixing ratios which appeared to be on the order of 20 ppbv for NO and 10 ppbv for NO₂. The soil acted as a net sink for ambient air NO and NO₂ mixing ratios higher than the equilibrium values and a net source for NO and NO₂ mixing ratios lower than the equilibrium values. This behaviour as well as the observation of equilibrium mixing ratios clearly indicate that NO and NO₂ are formed and destroyed concurrently in the soil.Average flux rates measured on bare unfertilized soils were about 10 g N m^-2 h^-1 for NO₂ and 8 g N m^-2 h^-1 for NO. The NO and NO₂ flux rates were significantly reduced on plant covered soil plots. In some cases, the flux rates of both gases became negative indicating that the vegetation may act as a sink for atmospheric NO and NO₂.Application of mineral fertilizers increased the NO and NO₂ emission rates. Highest emission rates were observed for urea followed by NH₄Cl, NH₄NO₃ and NaNO₃. The fertilizer loss rates ranged from 0.1% for NaNO₃ to 5.4% for urea. Vegetation cover substantially reduced the fertilizer loss rate.The total NO _x emission from soil is estimated to be 11 Tg N yr^-1. This figure is an upper limit and includes the emission of 7 Tg N yr^-1 from natural unfertilized soils, 2 Tg N yr^-1 from fertilized soils as well as 2 Tg N yr^-1 from animal excreta. Despite its speculative character, this estimation indicates that NO _x emission by soil is important for tropospheric chemistry especially in remote areas where the NO _x production by other sources is comparatively small.     

Production of N2O,CH4, and CO2 from soils in the tropical savanna during the dry season

Emissions of N₂O, CH₄, and CO₂ from soils at two sites in the tropical savanna of central Venezuela were determined during the dry season in February 1987. Measured arithmetic mean fluxes of N₂O, CH₄, and CO₂ from undisturbed soil plots to the atmosphere were 2.5×10⁹, 4.3×10¹⁰, and 3.0×10¹³ molecules cm^-2 s^-1, respectively. These fluxes were not significantly affected by burning the grass layer. Emissions of N₂O increased fourfold after simulated rainfall, suggesting that production of N₂O in savanna soils during the rainy season may be an important source for atmospheric N₂O. The CH₄ flux measurements indicate that these savanna soils were not a sink, but a small source, for atmospheric methane. Fluxes of CO₂ from savanna soils increased ninefold two hours after simulated rainfall, and remained three times higher than normal after 16 hours. More research is needed to clarify the significance of savannas in the global cycles of N₂O, CH₄, CO₂, and other trace gases, especially during the rainy season.     

Emission of nitrous oxide from temperate forest soils into the atmosphere

N₂O emission rates were measured during a 13-month period from July 1981 till August 1982 with a frequency of once every two weeks at six different forest sites in the vicinity of Mainz, Germany. The sites were selected on the basis of soil types typical for many of the Central European forest ecosystems. The individual N₂O emission rates showed a high degree of temporal and spatial variabilities which, however, were not significantly correlated to variabilities in soil moisture content or soil temperatures. However, the N₂O emission rates followed a general seasonal trend with relatively high values during spring and fall. These maxima coincided with relatively high soil moisture contents, but may also have been influenced by the leaf fall in autumn. In addition, there was a brief episode of relatively high N₂O emission rates immediately after thawing of the winter snow. The individual N₂O emission rates measured during the whole season ranged between 1 and 92 g N₂O-N m^–2 h^–1. The average values were in the range of 3–11 g N₂O-N m^–2 h^–1 and those with a 50% probability were in the range of 2–8 g N₂O-N m^–2 h^–1. The total source strength of temperate forest soils for atmospheric N₂O may be in the range of 0.7–1.5 Tg N yr^–1.     

Field measurements of emission of nitric oxide from fertilized and unfertilized forest soils in Sweden

Application of nitrate fertilizers on two types of forest soils led to a marked increase in the NO emission rate indicating a large potential for NO production in these soils. The largest fluxes on the fertilized plots were up to 60 ng NO–N m^–2 s^–1. About 0.35% of the applied nitrogen was lost as NO within about 14 days after fertilization. The fluxes from the unfertilized forest soils were in the range 0.1 to 0.8 ng NO–N m^–2 s^–1 with a median value of 0.3 ng NO–N m^–2 s^–1. If this value, obtained during June and August to September, is representative for the growing season (150 days), it corresponds to an annual emission of 0.04 kg NO–N ha^–1. This is about 30% of the value obtained for an unfertilized agricultural soil. Because of the large areas occupied by forests in Sweden the flux of NO from forest soils represents a significant contribution to the total flux of NO from soils in Sweden.Earlier observations of equilibrium concentrations for NO have been verified. These were found to range from 0.2 to 2 ppbv for an unfertilized forest soil and up to 170 ppbv for a fertilized soil. At the rural site in Sweden where these measurements were performed the ambient concentrations where found to be less than this equilibrium concentration, and consequently there was generally a net emission of NO.There are still large uncertainties about the global flux of NO from soils. Using direct measurements on three different types of ecosystems and estimates based on a qualitative discussion for the remaining land areas, a global natural source for NO of the order of 1 Tg N a^–1 was obtained. If 0.35% of the total annual production of fertilizer nitrogen is lost as NO, fertilization of soils may contribute with 20% to the natural flux from soils.     

厌氧条件下土壤反硝化气体(N2、N2O、NO)和CO2排放——氦环境培养—气体同步直接测定法的应用初探

反硝化过程是维系闭合氮循环所必需的氮素形态转化环节。土壤反硝化过程速率及产物比的直接测定是研究氮循环过程机理的基础,但却是一个难题。为解决此难题,德国卡尔斯鲁厄技术研究所与中国科学院大气物理研究所最近合作新建了一套通过氦环境培养-气体同步直接测定土壤反硝化气体--氮气（N2）、氧化亚氮（N2O）、一氧化氮（NO）和二氧化碳（CO2）排放的系统和与之配套的三阶段培养方法。为检验该新建系统和配套方法测定土壤反硝化过程的准确性和可靠性,以华北地区广泛分布的盐碱地农田土壤（采自山西运城）为研究对象开展实验室培养试验,在初始可溶性有机碳（DOC）供应比较充足约300 mgC kg–1干土（d.s.）的条件下,测试了不同初始土壤硝态氮含量水平（10、100 mgN kg–1d.s.左右,分别表示为10N和100N）的反硝化气体和CO2排放过程。结果显示：100N的反硝化速率（定义为N2、N2O 和NO 排放速率之和）显著高于10N 处理（统计检验显著水平p＜0.01）;两个处理的反硝化产物均以N2为主（质量比分别占77%和75%）,产物的NO/N2O摩尔比分别为1.2和1.5,N2O/N2摩尔比均为0.19;土壤反硝化气体动态排放速率及相关指标的测定结果表明,培养土壤中消失的硝态氮被回收81%～87%,培养前后的氮平衡率达92%～95%。因此,该新建方法测定土壤反硝化速率和产物比的结果具有很好的可靠性,为定量研究土壤反硝化过程提供了有效的直接测定手段。研究中检测到的土壤反硝化产物NO/N2O摩尔比大于1,不同于以往用液体培养基纯培养反硝化细菌得出的NO/N2O摩尔比远小于1的结论。这意味着,不能用NO/N2O摩尔比小于1与否来推断土壤排放的N2O和NO是主要来源于反硝化作用还是硝化作用。     

Variations in atmospheric CO2 at the Meteorological Research Institute, Tsukuba, Japan

Since April 1986, measurements of the CO₂ concentration in the surface air have been conducted at the Meteorological Research Institure (MRI, 36°04 N, 140°07 E, 25 m above sea level) in Tsukuba, located 50 km northeast of Tokyo, Japan. The CO₂ data measured over times between 11:00 Japan Standard Time (JST) and 16:00 JST (C _N ) were considered to be representative of the air (within a few ppmv) in the planetary boundary layer. To evaluate the representative CO₂ level on a spatial scale larger than that of the C _N record, the CO₂ data with hour-to-hour variation less than 1 ppmv were selected (C _P ). Comparison of these data with those of Ryori (39°02 N, 141°50 E), a continental station operated by the Japan Meteorological Agency, indicates that the C _P record provides a representative CO₂ level in the air on spatial scales of at least a few hundred kilometers.The C _N record allows an investigation of the internanual changes in photosynthesis/respiration against changes in climatological parameters. Within a small temperature anomaly (ca.±1 °C) respiration is sensitive to the temperature change, while photosynthesis is less sensitive. When the temperature anomaly is large, however, photosynthesis and respiration tend to be competitive.     

漂浮通量箱法和扩散模型法测定内陆水体CH_4和N_2O排放通量的初步比较研究

采用漂浮通量箱法和扩散模型法同步地观测了模拟内陆水体在不同条件下的CH4和N2O的水-气交换通量,旨在比较两类方法取得结果的异同。结果显示:这两类方法所测得的绝大多数CH4排放通量都与水中溶解氧呈显著线性负相关(显著性系数P0.001)。同时N2O排放通量与表层水温及水中铵态氮、硝态氮、溶解碳和溶解氧的关系可用包含所有上述水环境因素的Arrhenius动力学方程来表达,这些因素可以共同解释86%~90%的N2O通量变化(P0.0001),且不同方法测定的N2O通量的表观活化能和对表层水温的敏感系数分别介于47~59 kJ mol-1和1.92~2.27之间;扩散模型法所获得的CH4和N2O通量分别是箱法测定值的13%~175%和15%~240%,差异程度因模型而异;不同模型取得通量间相差20%~1200%,平均相差2.3倍。上述结果表明:仅用一种模型方法来取得CH4或N2O排放通量易形成较大偏差;不同扩散模型法和箱法测定的通量在反映CH4和N2O排放的内在规律方面具有一致性,但它们对真实气体通量的测量是否都存在不同程度的系统误差,尚需进一步研究。     

Secular evolution of the vertical column abundances of CHCIF2 (HCFC-22) in the Earth's atmosphere inferred from ground-based IR solar observations at the Jungfraujoch and at Kitt Peak,and comparison with model calculations

Series of high-resolution infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, between 06/1986 and 11/1992, and at Kitt Peak National Observatory, Tucson, Arizona (U.S.A.), from 12/1980 to 04/1992, have been analyzed to provide a comprehensive ensemble of vertical column abundances of CHCIF₂ (HCFC-22; Freon-22) above the European and the North American continents. The columns were derived from nonlinear least-squares curve fittings between synthetic spectra and the observations containing the unresolved 2v ₆ Q-branch absorption of CHCIF₂ at 829.05 cm^–1. The changes versus time observed in these columns were modeled assuming both an exponential and a linear increase with time. The exponential rates of increase at one-sigma uncertainties were found equal to (7.0±0.35)%/yr for the Junfraujoch data and (7.0±0.23)%/yr for the Kitt Peak data. The exponential trend of 7.0%/yr found at both stations widely separated in location can be considered as representative of the global increase of the CHCIF₂ burden in the Earth's atmosphere during the period 1980 to 1992. When assuming two realistic vertical volume mixing ratio profiles for CHCIF₂ in the troposphere, one quasi constant and the other decreasing by about 13% from the ground to the tropopause, the concentrations for mid-1990 were found to lie between 97 and 111 pptv (parts per trillion by volume) at the 3.58 km altitude of the Jungfraujoch and between 97 and 103 pptv at Kitt Peak, 2.09 km above sea level. Corresponding values derived from calculations using a high vertical resolution-2D model and recently compiled HCFC-22 releases to the atmosphere, were equal to 107 and 105 pptv, respectively, in excellent agreement with the measurements. The model calculated lifetime of CHCIF₂ was found equal to 15.6 years. The present results are compared critically with similar data found in the literature. On average, the concentrations found here are lower by 15–20% than those derived from in situ investigations; this difference cannot be explained by the absolute uncertainty of ±11% assigned presently to the infrared remote measurements.     

Emission of aliphatic amines from animal husbandry and their reactions: Potential source of N2O and HCN

We measured the emissions of volatile aliphatic amines and ammonia produced by the manure of beef cattle, dairy cows, swine, laying hens and horses in livestock buildings. The amine emissions consisted almost exclusively of the three methylamines and correlated with those of ammonia. The molar emission ratios of the methylamines to ammonia, and data on NH₃ emissions from animal husbandry in Europe, together with global statistics on domestic animals, were used to estimate the global emissions of amines. Annual global methylamine-N input to the atmosphere from animal husbandry in 1988 was 0.15±0.06 TgN (Tg=10¹² g). Almost 3/4 of these emissions consisted of trimethylamine-N. This represents about half of all methylamine emissions to the atmosphere. Other sources are marine coastal waters and biomass burning.Possible reaction pathways for atmospheric methylamines are shown. Among various speculative but possible products N₂O and HCN are of interest because the emission of methylamines could contribute to the global budgets of these compounds. Maximum atmospheric N₂O production from methylamines are below 0.4 Tg N/year, which is less than 10% of the annual N₂O growth rate. Although we do not expect the methylamine emissions to contribute in a major way to the atmospheric N₂O budget, more studies are needed to establish this conclusion beyond doubt. Similar conclusions hold for HCN.     

Influence of the surface microlayer on the flux of nonconservative trace gases (CO,H2, CH4, N2O) across the ocean-atmosphere interface

Gas exchange experiments were conducted in the tropical Atlantic Ocean during a ship expedition with FS Meteor using a small rubber raft. The temporal change of the mixing ratios of CO, H₂, CH₄ and N₂O in the headspace of a floating glass box and the concentrations of these gases in the water phase were measured to determine their transfer velocities across the ocean-atmosphere interface. The ocean acted as a sink for these gases when the water was undersaturated with respect to the mixing ratio in the headspace. The transfer velocities were different for the individual gases and showed still large differences even when normalized for diffusivity. Applying the laminar film model, film thicknesses of 20 to 70 m were calculated for the observed flux rates of the different gas species. When the water was supersaturated with respect to atmospheric CO, H₂, CH₄ and N₂O, the transfer velocities of the emission process were smaller than those determined for the deposition process. In case of H₂ and CH₄, emission was even not calculable although, based on the observed gradient, the laminar film model predicted significant fluxes at the air-sea interface. The results are interpreted by destruction processes active within the surface microlayer.     

The impact of the Tokyo Metropolitan Emissions Trading Scheme on reducing greenhouse gas emissions: findings from a facility-based study

This paper provides a detailed analysis of the Tokyo Metropolitan Emissions Trading Scheme (Tokyo ETS), Japan’s first emissions trading scheme with mandatory cap initiated by the government of Tokyo. Unlike trading schemes in other countries, the Tokyo ETS covers indirect emissions from the commercial sector. It is well known that a variety of market barriers impede full realization of energy efficiency opportunities, especially in the commercial sector. Experiences with the Tokyo ETS should therefore provide important lessons for the design of climate change mitigation policies, especially when targeting the commercial sector. The emissions from covered entities have been drastically reduced from those at the scheme’s outset, with an average 14% reduction as of the end of the first commitment period of five years (2010–2014) compared with 2009 levels. This paper shows that the Tokyo ETS alone did not cause these reductions; there were other drivers. Among them, the energy savings triggered by the Great East Japan Earthquake in 2011 were crucial. The contribution of credit trading, in contrast, was limited since most of the covered entities reduced emissions by themselves. Through an investigation of official reports, an assessment of the emissions data from the covered entities compared to those of uncovered entities and in-depth interviews with firms covered by the scheme, this paper confirms that the main drivers of emissions reductions by covered entities were separate from the ETS. In fact, the advisory aspect of the scheme seems to be much more important in encouraging energy-saving actions.

Key policy insights

• Most of the observed emission reductions were not caused by the Tokyo ETS alone.

• An advisory instrument was crucial to the effectiveness of the Tokyo ETS.

• The experience of the Tokyo ETS suggests that making full use of the advantages of emissions trading is difficult in the case of the commercial sector.

• Price signals have not provided a stimulus to climate change mitigation actions, which implies that establishing a cap to yield effective carbon prices poses a challenge.

     

The heterogeneous formation of N2O in air containing NO2, O3 and NH3

In a nighttime system and under relatively dry conditions (about 15 ppm H₂O), the reaction mixture of NO₂, O₃, and NH₃ in purified air turns out to result in the formation of nitrous oxide (N₂O). The experiments were performed in a continuous stirred flow reactor, in the concentration region of 0.02–2 ppm.N₂O is thought to arise through the heterogeneous reaction of gaseous N₂O₅ and absorbed NH₃ at the wall of the reaction vessel % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaatCvAUfKttLeary% qr1ngBPrgaiuaacqWFOaakcqWFobGtcqWFibasdaWgaaWcbaGae83m% amdabeaakiab-LcaPmaaBaaaleaacqWFHbqyaeqaaOGaey4kaSIaai% ikaiab-5eaonaaBaaaleaacqWFYaGmaeqaaOGae83ta80aaSbaaSqa% aiab-vda1aqabaGccaGGPaWaaSbaaSqaaiaadEgaaeqaaOGaeyOKH4% Qae8Nta40aaSbaaSqaaiab-jdaYaqabaGccqWFpbWtcqGHRaWkcqWF% ibascqWFobGtcqWFpbWtdaWgaaWcbaGae83mamdabeaakiabgUcaRi% ab-HeainaaBaaaleaacqWFYaGmaeqaaOGae83ta8eaaa!59AC!\[(NH_3 )_a + (N_2 O_5 )_g \to N_2 O + HNO_3 + H_2 O\]In principle, there is competition between this reaction and that of adsorbed H₂O with N₂O₅, resulting in the formation of HNO₃. At high water concentrations (RH>75%), no formation of N₂O was found. Although the rate constant of adsorbed NH₃ with gaseous N₂O₅ is much larger than that of the reaction of adsorbed H₂O with gaseous N₂O₅, the significance of the observed N₂O formation for the outside atmosphere is thought to be dependent on the adsorption properties of H₂O and NH₃ on a surface. A number of NH₃ and H₂O adsorption measurements on several materials are discussed.     

Emission of nitrogen oxides (NO x ) from a flooded soil fertilized with urea: Relation to other nitrogen loss processes

Emissions of nitric oxide and other odd nitrogen oxides (NO _x ) from a flooded rice field were studied after urea had been broadcast into the floodwater.The NO _x flux from the fertilized area was very low (0.2×10^-9 g N m^-2 s^-1) for the first few days after application of urea and was high (0.95×10^-9 g N m^-2 s^-1) in the subsequent period when significant nitrite and nitrate were present in the floodwater. At night, little if any NO _x was exhaled but ambient NO₂ was absorbed by the floodwater. An uptake velocity for NO₂ of 3×10^-4 m s^-1 was measured during one night. Maximum NO _x losses were observed near 1300 h when temperature and solar ultraviolet light were maximum.While the amounts of nitrogen oxides emitted are of little agronomic importance (2×10^-3 per cent of the fertilizer nitrogen was lost as NO _x during the 10-day study period), they may well be of significance as a source for some gas reactions in the atmosphere and for the global nitrogen cycle.Of the fertilizer nitrogen applied (as urea) approximately 30% was lost to the atmosphere by NH₃ volatilization, 15% by denitrification, presumably as N₂, and the remainder, less minor losses of NO and N₂O, remained in the plant/soil/water system.Now at Forestry Department, Australian National University, G.P.O. Box 4, ACT 2601, Australia.     

Tropospheric ozone and oxides of nitrogen over the north-western Pacific in summer

In summer, atmospheric ozone was measured from an aircraft platform simultaneously with nitric oxide (NO), oxides of nitrogen (NO _y ), and water vapor over the Pacific Ocean in east Asia from 34° N to 19° N along the longitude of 138±3°E. NO _y was measured with the aid of a ferrous sulfate converter. The altitude covered was from 0.5 to 5 km. A good correlation in the smoothed meridional distributions between ozone and NO _y was seen. In particular, north of 25° N, ozone and NO _y mixing ratios were considerably higher than those observed in tropical marine air south of 25° N. NO _y and O₃ reached a minimum of 50 pptv and 4 ppbv respectively in the boundary layer at a latitude of 20° N. The NO concentration between 2 and 5 km at the same latitude was 30 pptv. The profiles of ozone and water vapor mixing ratios were highly anti-correlated between 25° N and 20° N. In contrast, it was much poorer at the latitude of 33° N, suggesting a net photochemical production of ozone there.     

Carbon dioxide, methane, and nitrous oxide emissions from a rice-wheat rotation as affected by crop residue incorporation and temperature

Field measurements were made from June 2001 to May 2002 to evaluate the effect of crop residue application and temperature on CO2, CH4, and N2O emissions within an entire rice-wheat rotation season.Rapeseed cake and wheat straw were incorporated into the soil at a rate of 2.25 t hm-2 when the rice crop was transplanted in June 2001. Compared with the control, the incorporation of rapeseed cake enhanced the emissions of CO2, CH4, and N2O in the rice-growing season by 12.3%, 252.3%, and 17.5%,respectively, while no further effect was held on the emissions of CO2 and N2O in the following wheatgrowing season. The incorporation of wheat straw enhanced the emissions of CO2 and CH4 by 7.1%and 249.6%, respectively, but reduced the N2O emission by 18.8% in the rice-growing season. Significant reductions of 17.8% for the CO2 and of 12.9% for the N2O emission were observed in the following wheatgrowing season. A positive correlation existed between the emissions of N2O and CO2 (R2 = 0.445, n =73, p ＜ 0.001) from the rice-growing season when N2O was emitted. A trade-off relationship between the emissions of CH4 and N2O was found in the rice-growing season. The CH4 emission was significantly correlated with the CO2 emission for the period from rice transplantation to field drainage, but not for the entire rice-growing season. In addition, air temperature was found to regulate the CO2 emissions from the non-waterlogged period over the entire rice-wheat rotation season and the N2O emissions from the nonwaterlogged period of the rice-growing season, which can be quantitatively described by an exponential function. The temperature coefficient (Q10) was then evaluated to be 2.3±0.2 for the CO2 emission and 3.9±0.4 for the N2O emission, respectively.     

Ballon-borne and aircraft infrared measurements of ethane (C2H6) in the upper troposphere and lower stratosphere

Quantitative infrared measurements of ethane (C₂H₆) in the upper troposphere and lower stratosphere are reported. The results have been obtained from the analysis of absorption features of the ₉ band at 12.2 m, which have been identified in high-resolution ballon-borne and aircraft solar absorption spectra. The ballon-borne spectral data were recorded at sunset with the 0.02 cm^-1 resolution University of Denver interferometer system from a float altitude of 33.5 km near Alamogordo, New Mexico, on 23 March 1981. The aircraft spectra were recorded at sunset in July 1978 with a 0.06 cm^-1 resolution interferometer aboard a jet aircraft at 12 km altitude, near 35°N, 96°W. The balloon analysis indicates the C₂H₆ mixing ratio decreased from 3.5 ppbv near 8.8 km to 0.91 ppbv near 12.1 km. The results are consistent with the colum value obtained from the aircraft data.     

Post-Kyoto energy strategy of the Russian Federation,outlooks and prerequisites of the Kyoto mechanisms implementation in the country

Abstract

Energy sector emissions from Russia have declined by about 33% from 1990 levels. We estimate that some 60–70% of the reduction is due to economic decline, and about 8–12% of it is due to reforms in the energy sector; the remainder being due to the wider use of natural gas and structural changes in the economy. Vigorous institutional and technological measures to promote energy efficiency could lead to savings of over 100 million t.c.e. per year by 2010, and keep CO₂ emissions fairly close to current levels over the decade. In our view, international emissions trading should not lead to global emissions growth, but should facilitate the best energy saving and efficiency. Consequently, we propose that the available assigned amount should be divided into two components. That part arising from ‘type 1’ reductions, produced by special projects and measures relating to GHG reduction taken since 1990, should be freely traded; whereas the remaining ‘type 2’ surplus, without a clear link to real emission reduction activity, should only be traded if the revenues are recycled into special projects resulting in emissions reduction equal to or more than the amount of emissions sold.     

Kinetics of the Reactions of IO with HO2 and O(3P)

A discharge-flow tube coupled with resonance fluorescence and chemiluminescence detection has been used to investigate the reactions IO + HO₂ products (1) and IO + O(³P) I + O₂(2), at T = 296 ± 1 K and P = 1.7 - 2 Torr. The rate constants k_-1 and k₂ have been found to be (7.1 ± 1.6) × 10^-11 cm³ molecule^-1 s^-1 and (1.35 ± 0.15) × 10^-10 cm³ molecule^-1 s^-1, respectively.     

The correct form of the Webb,Pearman and Leuning equation for eddy fluxes of trace gases in steady and non-steady state,horizontally homogeneous flows

The original density corrections proposed by Webb et al. [Webb EK, Pearman GI, Leuning R (1980) Quart J Roy Meteorol Soc 106:85–100] for calculating the eddy fluxes of trace gases are shown to be correct for both steady and non-steady state, horizontally homogeneous flows. The revised theory replaces the original assumption of zero vertical flux of dry air with the requirement of no sources or sinks of dry air in the layer below the height of measurement.     

Ly(α) absorption cross-section of H2O and O2

The absorption cross-sections of water vapor and oxygen were measured, using a low-pressure radio frequency discharge through traces of hydrogen in argon as a light source for Ly() radiation. The cross-sections are H₂O = 1.59 × 10^–17 cm² and O₂ = 1.13 × 10^–20 + 1.72 × 10^–23 for water and oxygen, respectively, where P is the oxygen pressure in units of Torr. Ly() lamps, such as used for this work, are important light sources for photochemical laboratory work and find applications for trace-gas detection in the atmosphere. For the latter application, accurate cross-sections of water vapor and oxygen are needed.