Part Load Performance and Emission Improvement of Direct Injection Diesel Engine through Porous Medium Combustion Technique

Diesel engines are being extensively used in the transport sector owing to their excellent fuel efficiency, low emissions of carbon dioxide, unburned hydrocarbons and carbon monoxide. However, high emissions of nitrogen oxides (NO_x) and particulate matter (PM) place diesel engines on the down side. It is extremely complex to reduce both emissions at the same time, because of the trade‐off between NO_x and PM emissions. Even though the implementation of high pressure injection and common rail system could reduce both NO_x and PM emissions together, the cost involved would be high and unaffordable for many engine producers and consumers. In this research work, a new combustion technique termed, porous medium combustion, has been proven to be a proficient technique in reducing both NO_x and PM emissions from the direct injection diesel engines. However, the NO_x and PM emissions were found to be higher than the conventional engine at low range of part loads.     

Reduction in Exhaust Gas Temperature of Biodiesel Fueled Engine by Exhaust Gas Recirculation

Biodiesel is a renewable alternative fuel that can be used as substitute for mineral diesel. The use of biodiesel in diesel engines reduces all of the exhaust emissions expect NO_x. The higher temperature in the combustion chamber increases the NO_x emissions. The recirculation of a small percentage of cooled exhaust gases into the combustion chamber through the intake manifold reduces the in‐cylinder temperature. Moreover, the cooling of exhaust gases before mixing with fresh air introduced to the engine does not affect its volumetric efficiency but it absorbs the heat of combustion. This leads to a reduction in NO_x emissions and improves the engine brake thermal efficiency. This paper describes the investigation of the performance and emission characteristics of a biodiesel‐fueled, naturally aspirated, single cylinder diesel engine with cooled exhaust gas recirculation.     

Comparative Performance Assessment of Adsorbents for CO2 Capture via Physisorption in a Diesel Engine Exhaust

The atmospheric carbon dioxide (CO₂) concentration has been consistently increasing each year throughout the world. Internal combustion (IC) engines are significant contributors to CO₂ emissions. This study explores the possibility of employing effective biomass-based adsorbents to mitigate CO₂ from a diesel engine exhaust. As a first step, two distinct agro-wastes, namely, i) corn cob and ii) sugarcane bagasse, are used to prepare inexpensive and efficient activated carbons. The two main steps in the activated carbon preparation are a) carbonization and b) activation. The derived activated carbons are subjected to discrete analytical techniques to examine their structural and textural characteristics, surface functional groups, and physical, chemical, and adsorptive properties. As a second step, the exhaust treatment chamber unit is filled with the adsorbents one by one and is connected to the exhaust of the constant pressure heat addition engine. A single-cylinder, four-stroke, naturally-aspirated, air-cooled, direct injection (DI) compression ignition (CI) engine is used in the experimental investigations. The essential findings show that ≈68 and 60% of CO₂ emissions are adsorbed in the test engine by utilizing corn cob and sugarcane bagasse adsorbents, respectively. The results show that during the D100 and JME20 operations, the prospective adsorbents can curb more than 40% of overall CO₂ emissions.     

Dynamics of aircraft exhaust plumes in the jet-regime

A computational model describing the two-dimensional, turbulent mixing of a single jet of exhaust gas from aircraft engines with the ambient atmosphere is presented. The underlying assumptions and governing equations are examined and supplemented by a discussion of analytical solutions. As an application, the jet dynamics of a B747-400 aircraft engine in cruise and its dependence on key parameters is investigated in detail. The computer code for this dynamical model is computationally fast and can easily be coupled to complex chemical and microphysical models in order to perform comprehensive studies of atmospheric effects from aircraft exhaust emissions in the jet regime.     

Small- and medium-scale effects of high-flying aircraft exhausts on the atmospheric composition

Following numerous model studies of the global impacts of sub- and supersonic aircraft on the atmosphere, this paper assesses the separate aircraft engine exhaust effects of the 45°N cruise flight and at the 10- and 18-km levels of the July atmosphere. A box diffusion photochemical model in the cross-section plane of the flight trajectory is used to compute the effects of gas-phase and heterogeneous reactions on the condensation trail particles in the troposphere, and on the sulphate aerosols in the stratosphere. The enhanced horizontal dispersion of the exhaust plume is considered in the model.A significant but short term depletion of ozone is predicted, which is 99% restored in about 1 h in the wide plume with enhanced horizontal dispersion, but requires more than 24 h in the narrow plume without it. The oxidation rate of NO and NO₂ into the HNO₃ depends on the OH content in the exhausts and varies in all the cases. The heterogeneous photochemistry has only a small influence on the initial evolution of N₂O₅ and HO₂ in the plume.     

Ozone depletion in the plume of a solid-fueled rocket

The local effects of the emission of a solid-fueled rocket on the stratospheric ozone concentration have been investigated by photochemical model calculations. A one-dimensional horizontal model has been applied which calculates the trace gas composition at a single atmospheric altitude spatially resolved around the exhaust plume. Different cases were tested for the emissions of the Space Shuttle concerning the composition of the exhaust and the effects of heterogeneous reactions on atmospheric background aerosol.The strongest depletion of ozone is achieved when a high amount of the emitted chlorine is Cl₂. If it is purely HCl, the effect is smallest, though in this case the heterogeneous reactions show their largest influence. From the results it may be estimated whether ozone depletion caused by rocket launches can be detected by satellite instruments. It appears that the chance of coincidental detection of such an event is rather small.     

On the effect of emissions from aircraft engines on the state of the atmosphere

Emissions from aircraft engines include carbon dioxide, water vapour, nitrogen oxides, sulphur components and various other gases and particles. Such emissions from high-flying global civil subsonic air traffic may cause anthropogenic climate changes by an increase of ozone and cloudiness in the upper troposphere, and by an enhanced greenhouse effect. The absolute emissions by air traffic are small (a few percent of the total) compared to surface emissions. However, the greenhouse effect of emitted water and of nitrogen oxides at cruise altitude is potentially large compared to that of the same emissions near the earth’s surface because of relatively large residence times at flight altitudes, low background concentrations, low temperature, and large radiative efficiency. Model computations indicate that emission of nitrogen oxides has doubled the background concentration in the upper troposphere between 40○N and 60○N. Models also indicate that this causes an increase of ozone by about 5-20%. Regionally, the observed annual mean change in cloudiness is 0.4%. It is estimated that the resultant greenhouse effect of changes in ozone and thin cirrus cloud cover causes a climatic surface temperature change of 0.01-0.1 K. These temperature changes are small compared to the natural variability. Recent research indicates that the emissions at cruise altitude may increase the amount of stratospheric aerosols and polar stratospheric clouds and thereby have an impact on the atmospheric environment. Air traffic is increasing about 5-6% per year, fuel consumption by about 3%, hence the effects of the related emissions are expected to grow. This paper surveys the state of knowledge and describes several results from recent and ongoing research.     

水位变化对干涸湖底沉积物有机碳矿化的影响

人为干扰和气候变化会改变湖泊水位状态,明确不同水位条件下湖泊沉积物有机碳矿化特征及其影响因素,对了解内陆水生态系统碳循环具有重要意义.为探究干旱区典型盐湖沉积物有机碳矿化速率对水位变化的响应,以巴里坤湖干涸湖底原状沉积物为研究对象,初步探究了0（T1）、-9（T2）、-23（T3）、-34（T4）和-45 cm（T5）水位处理对沉积物有机碳矿化速率的影响.结果表明,T1、T2和T3处理有机碳矿化速率在试验初期较高（0~10 d）,10 d后缓慢下降,T4和T5处理有机碳矿化速率呈先增加后降低趋势;T1（1.718 μmol/（m²·s））与T3（1.784 μmol/（m²·s））处理有机碳矿化速率不存在显著差异,T1处理有机碳矿化速率是T2、T4和T5处理的1.09、3.31和3.57倍,不同处理有机碳累积矿化量表现为T3 > T1 > T2 > T4 > T5.有机碳累积矿化量（C_t）占沉积物有机碳（C₀）的比例（C_t/C₀）介于0.012~0.044之间,沉积物有机碳潜在排放量（C_i）占C₀的比例（C_i/C₀）介于0.018~0.045之间;水位降低,沉积物有机碳矿化常数（k值）减小,T1处理k值最大（0.137 d）,T4处理最小（0.032 d）.线性方程C_r=0.008x+0.488能较好地模拟有机碳矿化速率（C_r）与水位（x）的关系;不同水位处理有机碳矿化速率与模拟柱中沉积物5 cm温度呈显著的指数函数关系,T4、T5处理有机碳矿化温度敏感系数（Q₁₀）显著高于T1、T2和T3处理,即水位降低增加了巴里坤湖干涸湖底沉积物Q₁₀.因此,就巴里坤湖干涸湖底沉积物而言,水位从0 cm降至-45 cm时有机碳矿化速率降低,Q₁₀增加;反之水位上升则会促进有机碳矿化分解,Q₁₀降低.水位持续下降抑制有机碳矿化可能是维持干旱区盐湖沉积物碳库稳定的机制之一.     

The Gas-Phase Chemistry Of Urban Atmospheres

This paper reviews the chemistry of urban atmospheres,using recent measurement data to highlight the key concepts. We briefly summarise historical reports of air pollution and the impact that human activities have had on urban atmospheres since the IndustrialRevolution. Although pollution events in the first half of the 20th century were caused by high concentrations of smoke and sulphur dioxide, photochemical pollution has become the major problem in most of the major citiesaround the world. The chemistry of photochemical pollution episodes is discussed in some detail, particularly the crucial role played by volatile organic carbon and nitrogen oxides. Issues to be considered when modelling the chemistry of urban areas are briefly summarised, such as the uncertainties in chemical mechanisms and emission inventories, as well as the complexities of dynamical processes. Finally, we present some recent issues in urban chemistry, including the discovery that the amount of volatile organic carbon in urban atmospheres may be grossly under-estimated. We also use modelling resultsto show the importance of the reaction of ozone with reactive hydrocarbons as a radical source in urban atmospheres. Finally, the use of NO_X-NO₂ relationships to predict annual mean NO₂ concentrations is discussed.     

Identification and Apportionment of Sources of Ozone‐forming Potential for Proper Reduction Strategies

In this study, results of source identification and apportionment for ambient volatile organic compounds (VOCs) from a previous work were used to estimate ozone‐forming potentials (OFPs) of effective sources for developing proper strategies for reduction of tropospheric ozone pollution. The source identification and apportionment of ambient VOC pollution within Yildiz Technical University's Davutpasa Campus (Istanbul, Turkey) was done by positive matrix factorization (PMF). The results suggested five effective source groups with the emissions related with paint use and solvent use having the highest contributions (36.8 and 28.2%). The results from PMF were used along with maximum incremental reactivities to estimate potentials of individual sources for ozone formation. It was found that biogenic emissions (3.78) and traffic related emissions (gasoline and diesel vehicle exhaust) (3.83 and 3.15, respectively) have the highest potential for ozone formation in terms of grams O₃/g VOC emitted. The results were used to suggest proper source‐based reduction strategies for OFP.     

Greenhouse gas emissions (CO2, CH4, and N2O) from several perialpine and alpine hydropower reservoirs by diffusion and loss in turbines

We investigated greenhouse gas emissions (CO₂, CH₄, and N₂O) from reservoirs located across an altitude gradient in Switzerland. These are the first results of greenhouse gas emissions from reservoirs at high elevations in the Alps. Depth profiles were taken in 11 reservoirs located at different altitudes between the years 2003 and 2006. Diffusive trace gas emissions were calculated using surface gas concentrations, wind speeds and transfer velocities. Additionally, methane entering with the inflowing water and methane loss at the turbine was assessed for a subset of the reservoirs. All reservoirs were emitters of carbon dioxide and methane with an average of 970?±?340?mg?m^?2?day^?1 (results only from four lowland and one subalpine reservoir) and 0.20?±?0.15?mg?m^?2?day^?1, respectively. One reservoir (Lake Wohlen) emitted methane at a much higher rate (1.8?±?0.9?mg?m^?2?day^?1) than the other investigated reservoirs. There was no significant difference in methane emissions across the altitude gradient, but average dissolved methane concentrations decreased with increasing elevation. Only lowland reservoirs were sources for N₂O (72?±?22???g?m^?2?day^?1), while the subalpine and alpine reservoirs were in equilibrium with atmospheric concentrations. These results indicate reservoirs from subalpine/alpine regions to be only minor contributors of greenhouse gases to the atmosphere compared to other reservoirs.     

Groundwater impact on methane emissions from flooded paddy fields

High methane (CH₄) fluxes emitted from paddy fields strongly contribute to the accumulation of greenhouse gases into the atmosphere, compromising the eco-compatibility of one of the most important world foods. A strong link exists between infiltration rates of irrigation water and CH₄ emissions. Since depth to the groundwater table affects infiltration rates, a relevant groundwater impact is expected on CH₄ emissions from paddy fields. In this work, a theoretical approach is adopted to investigate the aquifer effect on CH₄ dynamics in paddies. Infiltration rates are strongly affected by the development of different connection states between aquifer and irrigation ponded water. A strong reduction in infiltration rates results from a water table near to the soil surface, when the system is hydraulically connected. When the groundwater level increases, the infiltration rate reduction due to the switch from disconnected to connected state promotes a relevant increase of CH₄ emissions. This is due to a strong reduction of dissolved organic carbon (DOC) percolation, which leads to higher DOC availability for microbial CH₄ production and, consequently, higher CH₄ emissions. Our simulations show that CH₄ fluxes can be reduced by up to 24% when groundwater level is decreased and the aquifer is disconnected from ponding water. In paddies with shallow aquifers, lowering the water table with a drainage system could thus represent a promising CH₄ mitigation option.     

三峡水库CO2、CH4通量监测分析研究

自成库以来,三峡水库CO₂、CH₄等温室气体通量较蓄水前发生明显改变。如何科学认识和客观评估三峡水库修建及运行对其CO₂、CH₄等温室气体通量的影响备受关注。本文简要回顾了自2009年以来在三峡水库开展CO₂、CH₄等温室气体通量监测与分析工作,综述认为,现阶段三峡水库温室气体排放以水-气界面扩散释放为主要途径。陆源输入的有机碳是主导三峡水库CO₂、CH₄产生的主要碳源,但在局部区段或时段自源性有机碳的贡献亦十分显著。同蓄水前相比,三峡水库碳排放量呈现为净增加,淹没效应约占水库C净增量的20%,库区内点面源污染负荷并未对CO₂排放的净增量产生显著贡献,阻隔效应和生态系统重建效应对三峡水库碳排放的净增量产生显著贡献。近10年来,监测方法比对、监测点位优化等工作在一定程度上完善了三峡水库温室气体通量监测体系。新方法、新技术的引入也为三峡水库温室气体通量监测分析提供了有利支撑和保障,但复杂水文环境...     

Hydrocarbon gases (C1–C5) and organic matter in bottom sediments of the Ivankovo Reservoir on the Volga River

The results of studying the composition of hydrocarbon gases (C₁–C₅) and organic matter in bottom sediments of the Ivankovo Reservoir in 1995, 2004, and 2005 are given. The methods used in the study include vapor-phase gas chromatography, instrumental pyrolysis gas chromatography, and mass-spectrometry for determining organic carbon δ ¹³C_org. The gas field of bottom sediments in different regions of the reservoir varies widely in terms of gas saturation and the spectrum of hydrocarbon gases. This suggests the heterogeneous composition of organic matter in the sediments and different conditions of its input and transformation processes. The gases were found to contain saturated hydrocarbons from methane to pentane C₁–C₅, including isomers i-C₄ and i-C₅ and unsaturated compounds C₂–C₄. A correlation was found to exist between methane distribution and the distribution of its more high-molecular homologues, which confirms their genetic relationship in bottom sediments. The obtained results show an increase in the rate of microbiological processes and organic matter transformation for most regions in the Ivankovo Reservoir. The only exceptions are the zones of Moshkovichskii Bay and the sections at Gorodnya and Konakovo, where technogenic organic matter is being accumulated. The high information value of hydrocarbon gases as biogeochemical markers of the sources of organic matter and the rates of its transformation is demonstrated. The isotopic composition of organic-matter carbon in the bottom sediments of the Ivankovo Reservoir δ ¹³C varies from ?26.21 to ?30.86‰.     

The present-day and future impact of NOx emissions from subsonic aircraft on the atmosphere in relation to the impact of NOx surface sources

The effect of present-day and future NO_x emissions from aircraft on the NO_x and ozone concentrations in the atmosphere and the corresponding radiative forcing were studied using a three-dimensional chemistry transport model (CTM) and a radiative model. The effects of the aircraft emissions were compared with the effects of the three most important anthropogenic NO_x surface sources: road traffic, electricity generation and industrial combustion. From the model results, NO_x emissions from aircraft are seen to cause an increase in the NO_x and ozone concentrations in the upper troposphere and lower stratosphere, and a positive radiative forcing. For the reference year 1990, the aircraft emissions result in an increase in the NO_x concentration at 250 hPa of about 20 ppt in January and 50 ppt in July over the eastern USA, the North Atlantic Flight Corridor and Western Europe, corresponding to a relative increase of about 50%. The maximum increase in the ozone concentrations due to the aircraft emissions is about 3-4 ppb in July over the northern mid-latitudes, corresponding to a relative increase of about 3-4%. The aircraft-induced ozone changes cause a global average radiative forcing of 0.025 W/m² in July. According to the ANCAT projection for the year 2015, the aircraft NO_x emissions in that year will be 90% higher than in the year 1990. As a consequence of this, the calculated NO_x perturbation by aircraft emissions increases by about 90% between 1990 and 2015, and the ozone perturbation by about 50-70%. The global average radiative forcing due to the aircraft-induced ozone changes increases by about 50% between 1990 and 2015. In the year 2015, the effects of the aircraft emissions on the ozone burden and radiative forcing are clearly larger than the individual effects of the NO_x surface sources. Taking chemical conversion in the aircraft plume into account in the CTM explicitly, by means of modified aircraft NO_x emissions, a significant reduction of the aircraft-induced NO_x and ozone perturbations is realised. The NO_x perturbation decreases by about 40% and the ozone perturbation by about 30% in July over Western Europe, the eastern USA and the North Atlantic Flight Corridor.     

Variation in the photochemical lability of dissolved organic matter in a large boreal watershed

Boreal watersheds contain a vast quantity of terrestrially derived dissolved organic matter (DOM) originating from wetland and forest soils, yet variation in the potential for photochemical transformation of boreal aquatic DOM sources remains poorly understood. Laboratory solar radiation exposure experiments were conducted on DOM samples collected in three seasons, across nine sites, representing contrasting catchment composition and watershed position to assess variation in the photochemical lability of boreal DOM source and stable carbon isotopic signature (δ¹³C) of photomineralized DOM. Dissolved organic carbon (DOC) loss rates during laboratory exposure were lowest in summer, suggesting that DOM may have been more photo-degraded during summer. DOM from upstream portions of forested stream sites and wetland-influenced sites was more photolabile relative to downstream portions and the river DOM, suggesting potential losses in photolabile DOM downstream and in the lower reaches of the watershed. Increased a₂₅₄:a₃₅₀ and spectral slope following sample exposure suggest photoproduction of low molecular weight (LMW) CDOM and/or a higher photoreactivity of high molecular weight versus LMW compounds. Photomineralization of nitrogen was regulated by organic nitrogen concentration and resulted in NH₄ ⁺-photoproduction rates between 0.01 and 0.3?μM N?h^?1 and ecologically significant increases in NH₄ ⁺ for these waters. The δ¹³C of the photomineralized DOM was positively correlated to initial DOC concentration and generally lower when initial DOC concentrations were lower, suggesting variation in photomineralized DOM δ¹³C may be a result of kinetic isotope fractionation. Results from this study demonstrate significant variation in the photochemical lability of boreal watershed sources of DOM. Such variation suggests landscape and environmental change has the potential to alter the biogeochemical role photochemical transformations play in downstream portions of boreal watersheds.     

Soil carbon losses by sheet erosion: a potentially critical contribution to the global carbon cycle

Despite soil erosion through water being a ubiquitous process and its environmental consequences being well understood, its effects upon the global carbon cycle still remain largely uncertain. How much soil organic carbon (SOC) is removed each year from soils by sheet wash, an important if not the most efficient mechanism of detachment and transport of surficial soil material? What are the main environnemental controls worldwide? These are important questions which largely remain unanswered. Empirical data from 240 runoff plots studied over entire rainy seasons from different regions of the world were analysed to estimate particulate organic carbon (POC) losses (POC_L), and POC enrichment in the sediments compared to the bulk soil (ER), which can be used as a proxy of the fate of the eroded POC. The median POC_L was 9.9 g C m^‐2 y^‐1 with highest values observed for semi‐arid soils (POC_L = 10.8 g C m^‐2 y^‐1), followed by tropical soils (POC_L = 6.4 g C m^‐2 y^‐1) and temperate soils (POC_L = 1.7 g C m^‐2 y^‐1). Considering the mean POC_L of 27.2 g C m^‐2 y^‐1, the total amount of SOC displaced annually by sheet erosion from its source would be 1.32 ± 0.20 Gt C, i.e. 14.6% of the net annual fossil fuel induced C emissions of 9 Gt C. Because of low sediment enrichment in POC, erosion‐induced CO₂ emissions are likely to be limited in clayey environments while POC burial within hillslopes is likely to constitute an important carbon sink. In contrast, most of the POC displaced from sandy soils is likely to be emitted to the atmosphere. These results underpin the major role sheet wash plays in the displacement of SOC from its source and in the fate of the eroded SOC, with large variations across the different pedo‐climatic regions of the world. Copyright © 2015 John Wiley & Sons, Ltd.     

考虑碳减排的水库多目标提前蓄水调度研究

针对当前的水库提前蓄水调度研究尚未考虑碳减排问题,本文基于水库碳排放和有机碳埋藏因子法,构建了考虑碳减排的水库提前蓄水调度模型,采用基于熵权重的逼近理想解排序法(TOPSIS)对提前蓄水调度方案进行了多目标评价,以优选调度方案,在三峡水库开展了实例研究。研究结果表明:三峡水库从9月1日起蓄,于9月30日逐步蓄至167 m的调度方案最优,相较于原设计方案,在不增加防洪风险的前提下,多年平均发电量增加29.91亿kW·h(8.80%),弃水量减少26.03亿m³(27.51%),碳排放量减少69.26亿g(3.94%),有机碳埋藏量增加1.93亿g(1.28%),温室气体的CO₂碳当量减少235.48亿g(3.85%),提前蓄水方案可显著提升三峡水库发电量、供水保障能力和减少碳排放量。本研究为水库提前蓄水的水碳协同调度提供了技术支撑。     

Two episodes of C-depletion in organic carbon in the latest Permian: Evidence from the terrestrial sequences in northern Xinjiang, China

New analyses reveal two intervals of distinctly lower δ¹³C values in the terrestrial organic matter of Permian–Triassic sequences in northern Xinjiang, China. The younger negative δ¹³C_org spike can be correlated to the conspicuous and sharp δ¹³C drops both in carbonate carbon and organic carbon near the Permian–Triassic event boundary (PTEB) in the marine section at Meishan. The geochemical correlation criteria are accompanied by a magnetic susceptibility pulse and higher abundances of distinctive, chain-like organic fossil remains of Reduviasporonites.The older negative δ¹³C_org spike originates within a latest Permian regression. Significant changes in organic geochemical proxies are recorded in the equivalent interval of the marine section at Meishan. These include relatively higher concentrations of total organic carbon, isorenieratane, C₁₄–C₃₀ aryl isoprenoids and lower ratios of pristane/phytane that, together, indicate the onset of anoxic, euxinic and restricted environments within the photic zone. The massive and widespread oxidation of buried organic matter that induced these euxinic conditions in the ocean would also result in increased concentrations of ¹³C-depleted atmospheric CO₂. The latest Permian environmental stress marked by the older negative δ¹³C_org episode can be correlated with the distinct changeover of ostracod assemblages and the occurrences of morphological abnormalities of pollen grains. These observations imply that biogeochemical disturbance was manifested on the land at the end of the Permian and that terrestrial organisms responded to it before the main extinction of the marine fauna.     

The fluvial flux of particulate organic matter from the UK: the emission factor of soil erosion

Soil erosion has been identified as a potential global carbon sink since eroded organic matter is replaced at source and eroded material is readily buried. However, this argument has relied on poor estimates of the total fate of in‐transit particulates and could erroneously imply soil erosion could be encouraged to generate carbon stores. These previous estimates have not considered that organic matter can also be released to the atmosphere as a range of greenhouse gases, not only carbon dioxide (CO₂), but also the more powerful greenhouse gases methane (CH₄) and nitrous oxide (N₂O). As soil carbon lost by erosion is only replaced by uptake of CO₂, this could represent a considerable imbalance in greenhouse gas warming potential, even if it is not significant in terms of overall carbon flux. This work therefore considers the flux of particulate organic matter through UK rivers with respect to both carbon fluxes and greenhouse gas emissions. The results show that, although emissions to the atmosphere are dominated by CO₂, there are also considerable fluxes of CH₄ and N₂O. The results suggest that soil erosion is a net source of greenhouse gases with median emission factors of 5.5, 4.4 and 0.3 tonnes CO_2eq/yr for one tonne of fluvial carbon, gross carbon erosion and gross soil erosion, respectively. This study concludes that gross soil erosion would therefore only be a net sink of both carbon and greenhouse gases if all the following criteria are met: the gross soil erosion rate were very low (<91 tonnes/km²/yr); the eroded carbon were completely replaced by new soil organic matter; and if less than half of the gross erosion made it into the stream network. By establishing the emission factor for soil erosion, it becomes possible to properly account for the benefits of good soil management in minimizing losses of greenhouse gases to the atmosphere as a by‐product of soil erosion. Copyright © 2015 John Wiley & Sons, Ltd.