Photoemission for in situ analysis of particulate combustion emissions

A review on principles of operation, design, and various applications of the aerosol photoemission sensor is given. Influence of intensity and wavelength of the light as well as the type of information, obained by the sensor are discussed. Several applications requiring emission or ambient air measurements demonstrate the features of the sensor.     

能量密度对低温等离子体辅助催化转化柴油机颗粒物和NOx的影响

为了研究低温等离子体辅助催化后处理技术对柴油机有害排放物的作用效果,基于介质阻挡放电理论设计了低温等离子体（NTP）发生器,研究了NTP发生器工作电压随能量密度的变化关系。以涂覆γ-Al2O3的蜂窝状陶瓷为载体,采用柠檬酸凝胶法制备了LaMnO3催化剂,建立了NTP辅助LaMnO3催化试验系统。在台架试验基础上,研究了能量密度变化对NTP辅助LaMnO3催化技术转化（颗粒物）PM和NOx的影响规律。试验结果表明：在相同频率作用下,NTP发生器的能量密度随着工作电压的升高而增加;与原机相比,NTP辅助LaMnO3催化技术作用后NO浓度显著降低,NO2浓度显著增加,NOx浓度降低;随着能量密度的增加,碳烟转化效果越明显,碳烟的不透光烟度最高降低约83%。结果表明NTP辅助LaMnO3催化技术可有效转化PM和NOx,在柴油机排气后处理领域有着广泛的研究前景。     

Reduction in greenhouse gas emissions by no-tilling rice cultivation in Hachirogata polder,northern Japan: Life-cycle inventory analysis

Abstract

The scenarios for conventional puddling and no-tilling rice (Oryza sativa L.) cultivation were compared in terms of greenhouse gas (GHG) emissions from paddy fields, fuel consumption and manufacturing of invested materials using a life cycle inventory (LCI) based analysis. Only the differences between the scenarios were examined. The no-tilling scenario omitted both tilling and puddling, but included spraying of a non-selective herbicide and used a transplanter equipped with a rotor. Fertilization was a basal single application of controlled release fertilizer in nursery boxes for all scenarios. After transplanting, there were no differences in machine work, invested materials or rice yields between the scenarios. The no-tilling scenario saved on fuel consumption, totaling carbon dioxide (CO₂) output of 42 kg ha^?1, which was equal to the 6% reported GHG emissions from fuel consumption by operating machines during rice production in Japan. Methane (CH₄) and nitrous oxide (N₂O) emissions from the paddy fields were also monitored and compared for the scenarios. Methane has a major effect on global warming as part of the GHG emitted from paddy fields. The cumulative CH₄ emissions from the no-tilling cultivation were 43% lower than those from conventional puddling cultivation because the plow layer was more oxidative in no-tilling cultivation. The N₂O emissions were not significantly different between the cultivation scenarios. There were no significant differences in soil respiration, soil carbon contents or straw yields between the cultivation scenarios. The effect of tillage on CO₂ flux in the paddy fields did not seem to be significant in this study. Consequently, the GHG emissions from the no-tilling field counted as CO₂ using global warming potentials were 1,741 kg CO₂ ha^?1 lower than those from the conventional puddling field. In conclusion, no-tilling rice cultivation has the potential to save 1,783 kg CO₂ ha^?1 calculated using the sum of fuel consumption and GHG emissions from paddy fields. No-tilling rice cultivation is considered to be environmentally friendly agriculture with respect to reducing GHG emissions.     

Does the heathland flora in north-western Belgium show an extinction debt?

The large losses of heathland area since the end of the 18th century can be expected to have resulted in the decline or even extinction of many characteristic heathland species. Historical data on plant species distribution patterns can provide valuable information in this context. Therefore, the aims of this research are to study how the loss of heathland area has changed the presence of heathland and forest plant species in north-western Belgium using historical plant distribution data, and to test whether the heathland flora shows an extinction debt. Furthermore, plant traits determining extinction sensitivity are investigated.Our results revealed that, despite the dramatic reduction of heathland area (more than 99% of heathland was destroyed over a 230-year period), the loss of heathland species is relatively limited (11%) and is comparable with that of forest species (11%). Heathland species that have a long-term persistent seed bank or can propagate vegetatively are least sensitive to extinction. For forest species, on the other hand, growth form is the key determinant for extinction sensitivity. Long-lived woody species have a greater chance of persisting.The relatively low extinction numbers probably represent an extinction debt and the full effects of habitat loss may not have been fully manifested yet. Consequently, future extinctions are expected to occur unless environmental conditions are improved. Therefore, heathland restoration and prevention of further heathland area losses is required.     

Sources of data for rural health research: development of an inventory of Canadian databases

Secondary data sources can often be used to help address questions about the health status, health behavior, health resources allocation, and utilization of health services of rural Canadians. But the task of deciding which Canadian databases are amenable to rural health research remains a challenge. As part of a larger research project titled "Canada's Rural Communities: Understanding Rural Health and Its Determinants," an inventory of 51 Canadian databases that have the potential of being used for rural health research was compiled, and it continues to be maintained and updated. The websites maintained by two of Canada's leading statistical data centers were systematically searched, along with other published articles and national reports, to produce this inventory. The criteria used to determine which data sources to include in this inventory are: (1) databases containing data at the national level that can be accessed by researchers, (2) databases containing data that are relevant to a variety of rural health issues, and (3) databases containing data that could be partitioned into rural and non-rural geographies. Detailed information is available by searching the inventory of national rural health research-related databases through the internet (www.cranhr.ca) or by contacting the lead author of this article. This article examines some of the issues in developing this resource and demonstrates the usefulness of its contents to Canadian and other rural health researchers.     

Features of airborne breathable particulate in a remote rural and in an urban area

In order to define the atmosphere pollution role in the lung cancer etiology it is necessary to carefully measure the composition of airborne pollutants. The evaluation of atmosphere pollution by analytic electron microscopy technique has made it possible to analyze the morphology and composition of airborne breathable particulate and to characterize the sources. The comparative study of a rural area and a downtown area in Rome has shown qualitative and quantitative differences in the pollution pattern. In the urban area the data we have obtained point out motor vehicle traffic as the greatest source of pollution. A large amount of heavy metals and mineral fibers, potentially noxious for health, was observed.     

Towards an agronomic assessment of N2O emissions: a case study for arable crops

Agricultural soils are the main anthropogenic source of nitrous oxide (N₂O), largely because of nitrogen (N) fertilizer use. Commonly, N₂O emissions are expressed as a function of N application rate. This suggests that smaller fertilizer applications always lead to smaller N₂O emissions. Here we argue that, because of global demand for agricultural products, agronomic conditions should be included when assessing N₂O emissions. Expressing N₂O emissions in relation to crop productivity (expressed as above‐ground N uptake: ‘yield‐scaled N₂O emissions') can express the N₂O efficiency of a cropping system. We show how conventional relationships between N application rate, N uptake and N₂O emissions can result in minimal yield‐scaled N₂O emissions at intermediate fertilizer‐N rates. Key findings of a meta‐analysis on yield‐scaled N₂O emissions by non‐leguminous annual crops (19 independent studies and 147 data points) revealed that yield‐scaled N₂O emissions were smallest (8.4 g N₂O‐N kg⁻¹N uptake) at application rates of approximately 180–190 kg N ha⁻¹ and increased sharply after that (26.8 g N₂O‐N kg⁻¹ N uptake at 301 kg N ha⁻¹). If the above‐ground N surplus was equal to or smaller than zero, yield‐scaled N₂O emissions remained stable and relatively small. At an N surplus of 90 kg N ha⁻¹ yield‐scaled emissions increased threefold. Furthermore, a negative relation between N use efficiency and yield‐scaled N₂O emissions was found. Therefore, we argue that agricultural management practices to reduce N₂O emissions should focus on optimizing fertilizer‐N use efficiency under median rates of N input, rather than on minimizing N application rates.     

Microbial induced nitrous oxide emissions from an arable soil during winter

Nitrous oxide (N₂O) release rates were measured from an fertilized and unfertilized plot on silty loam (Gleyic Luvisol) cropped with winter wheat. Rates were estimated using a closed soil cover box technique throughout a continuous investigation period of 12 months. The 12 months of investigation were separated into the cropping period (March to November) and the winter period (December to February). Soil management and all N-applications were made during the cropping period. The application of 220 kg N to the soil induced significantly higher N₂O losses throughout the cropping season compared to the unfertilized soil. No significant differences were found during winter, where 70% of the annual N₂O emissions were found. The temporal changes of the N₂O emission rates on both soils were highly correlated (r=0.96; P≤0.001), and could be attributed to temporal changes in soil temperature (r=0.65; P≤0.01) resulting from freezing and thawing cycles. In order to decide whether the N₂O production can be attributed to microbial or non-microbial processes in soil, the time courses of the N₂O emissions from a γ-ray sterilized and a non-sterilized soil were compared in a laboratory experiment, where the freezing and thawing cycles were simulated according to field conditions. The results indicated, that microbial processes were responsible for N₂O production in thawing and even frozen soils.     

Spatial variability of nitrous oxide emissions in an unmanaged old‐growth beech forest

Nitrous oxide (N₂O) is a high‐impact greenhouse gas. Due to the scarcity of unmanaged forests in Central Europe, its long‐term natural background emission level is not entirely clear. We measured soil N₂O emissions in an unmanaged, old‐growth beech forest in the Hainich National Park, Germany, at 15 plots over a 1‐year period. The average annual measured N₂O flux rate was (0.49 ± 0.44) kg N ha^–1 y^–1. The N₂O emissions showed background‐emission patterns with two N₂O peaks. A correlation analysis shows that the distance between plots (up to 380 m) does not control flux correlations. Comparison of measured data with annual N₂O flux rates obtained from a standard model (Forest‐DNDC) without site‐specific recalibration reveals that the model overestimates the actual measured N₂O flux rates mainly in spring. Temporal variability of measured N₂O flux was better depicted by the model at plots with high soil organic C (SOC) content. Modeled N₂O flux rates were increased during freezing only when SOC was > 0.06 kg C kg^–1. The results indicate that the natural background of N₂O emissions may be lower than assumed by most approaches.     

Nitrous oxide emissions from an apple orchard soil in the semiarid Loess Plateau of China

Nitrous oxide (N₂O) fluxes from an apple orchard soil in the semiarid Loess Plateau of China were measured using static chambers from September 2007 to September 2008. In this study, three sites were selected at distance of 2.5 m (D 2.5), 1.5 m (D 1.5), and 0.5 m (D 0.5) from the apple tree row. Nitrous oxide fluxes followed seasonal pattern, with high N₂O emission rates occurring in the hot-humid summer and low rates in the cold-dry winter. Pulses of N₂O emissions occurred after nitrogen fertilizer application, summer rainfall events, and during freeze-thaw cycles. Annual average N₂O emission rates were the highest at D 0.5 site (48.2 ± 39.9 μg N₂O m⁻² h⁻¹), the lowest at D 2.5 site (31.9 ± 18.2 μg N₂O m⁻² h⁻¹), and intermediate at D1.5 site (36.8 ± 32.2 μg N₂O m⁻² h⁻¹), suggesting that N₂O emissions from the apple orchard soil increased when the chamber location was closer to the apple tree row. This may be due to the fertilization close to roots in hot and humid season. Over one third (37.1%) of the annual N₂O emission occurred in the summer. Annual N₂O emissions from the apple orchard soil averaged to 3.22 kg N₂O ha⁻¹ year⁻¹. Annual emission factor of the apple orchard from the applied fertilizer (uncorrected for background emission) was 0.658%. This value was nearly a half (53%) of the default value provided by the Intergovernmental Panel on Climate Change for the application of synthetic fertilizers to cropland (1.25%). Therefore, the amount of N₂O emissions from the semiarid apple orchard soil could be largely overestimated if no regional-specific factor is used.     

Nitrapyrin effectiveness in reducing nitrous oxide emissions decreases at low doses of urea in an Andosol

In the tropics,frequent nitrogen(N)fertilization of grazing areas can potentially increase nitrous oxide(N₂O)emissions.The application of nitrification inhibitors has been reported as an effective management practice for potentially reducing N loss from the soil-plant system and improving N use efficiency(NUE).The aim of this study was to determine the effect of the co-application of nitrapyrin(a nitrification inhibitor,NI)and urea in a tropical Andosol on the behavior of N and the emissions of N₂O from autotrophic and heterotrophic nitrification.A greenhouse experiment was performed using a soil(pH 5.9,organic matter content 78 g kg^-1,and N 5.6 g kg^-1)sown with Cynodon nlemfuensis at 60%water-filled pore space to quantify total N₂O emissions,N₂O derived from fertilizer,soil ammonium(NH₄⁺)and nitrate(NO₃^-),and NUE.The study included treatments that received deionized water only(control,NI).No significant differences were observed in soil NH₄⁺content between the UR and UR+NI treatments,probably because of soil mineralization and NO₃^-produced by heterotrophic nitrification,which is not effectively inhibited by nitrapyrin.After 56 d,N₂O emissions in UR(0.51±0.12 mg N₂O-N concluded that the soil organic N mineralization and heterotrophic nitrification are the main processes of NH₄⁺and NO₃^-production.Additionally,it was found that N₂O emissions were partially a consequence of the direct oxidation of the soil's organic N via heterotrophic nitrification coupled to denitrification.Finally,the results suggest that nitrapyrin would likely exert significant mitigation on N₂O emissions only if a substantial N surplus exists in soils with high organic matter content.     

Nitrous oxide emissions from grassland in an intensive dairy farm in the Basque Country of Spain

Abstract. Intensively managed grasslands are potentially a large source of N₂O in the North Coast of Spain because of the large N input, the wet soil conditions and mild temperatures. To quantify the effect of fertilizer type and management practices carried out by farmers in this area, field N₂O losses were measured over a year using the closed chamber technique. Plots received two types of fertilizer: cattle slurry (536 kg N ha^–1) and calcium ammonium nitrate (140 kg N ha^–1). N₂O losses were less in the slurry treatment than after mineral fertilizer. This was probably due to high, short‐lived peaks of N₂O encountered immediately following mineral N addition. In contrast, the seasonal distribution of N₂O losses from the slurry amended plot was more uniform over the year. The greater N₂O losses in the mineral treatment might have been enhanced by the combined effect of mineral fertilizer and past organic residues present from previous organic amendments. Weak relationships were found between N₂O emission rates and soil nitrate, soil ammonium, soil water content and temperature. Better relationships were obtained in the mineral treatment than in the slurry plots, because of the wider range in soil mineral N. Water filled pore space (WFPS) was a key factor controlling N₂O emissions. In the > 90% WFPS range no relationships were found. The best regressions were found for the mineral treatment in the 40–65% WFPS range, 49% of the variance being explained by soil nitrate and ammonium content. In the 65–90% WFPS range, 43% of the variance was explained by nitrate only, but the inclusion of soil ammonium did not improve the model as it did in the 40–65% WFPS range. This fact indicates that nitrification is likely to be an important process involved in N₂O emissions at the 40–65% WFPS.     

柴油机微粒捕集器喷油助燃再生过程热工特性

为获得柴油机微粒捕集器喷油助燃再生过程热工变化特性,在考虑微粒氧化反应次模型的基础上,建立壁流式蜂窝陶瓷过滤体喷油助燃再生数学模型,通过对速度场、压力场、温度场与微粒浓度场等多场耦合求解,研究其再生过程热工参数变化规律。结果表明:喷油助燃装置热工参数、排气特征对过滤体再生过程影响较大。适当增大气油配比、提高喷油压力与喷油速率及加大补气流量均使再生过程中过滤体孔道壁面峰值温度升高,沉积在过滤体孔道壁面上的微粒层氧化燃烧速率加快,缩短过滤体的再生时间,但随着气油配比、补气流量的进一步增大,空气对流散热损失增强,及喷油速率进一步提高,混合气过浓导致燃烧器燃烧性能恶化等影响,孔道沉积微粒氧化速率、壁面峰值温度下降,再生速率降低。排气流量对再生过程的影响与补气流量相似,但从分析结果来看,排气流量能否合适控制对过滤体的再生过程有重要影响。这些规律的提出,为实现微粒捕集器安全、可靠、高效地再生及其过程控制的优化等方面提供依据和技术参考。     

Studies of forest floor biological activities in an area previously damaged by sulphur dioxide emissions

As part of an environmental control program aimed to assess possible future effects of air contaminants from a new destruction plant for hazardous chemical residuals in Central Sweden, a study was undertaken the year before the plant went into operation to collect base-line information on biological activities in the soils of the surrounding forests. Measurements were made of N-mineralization, respiration, phosphatase-, dehydrogenase-, and nitrogenase activity on sieved samples from the forest floor (0 to 3 cm). The results were evaluated in relation to a previous contamination of the area by air pollutants from a plant for oil production. This plant produced oil from the local alun shale between 1942 and 1966. During these years somewhere between 6 × 10⁵ and 1.2 × 10⁶ tonne of S, mainly in the form of SO₂, were released into the atmosphere. The results showed that the forest floor was not especially acid when compared to similar sites in locally unpolluted areas. The concentration of Cu, however, was five times higher than expected. No disturbances could be detected as regards N-mineralization, respiration or phosphatase activity. Dehydrogenase- and nitrogenase activity were much more difficult to evaluate. A suppression of dehydrogenase activity was indicated on the study plots closest to the previous plant. In the case of nitrogenase activity no appropriate reference material was available to judge whether disturbances existed.     

中国东北苹果园中土壤总硝化作用和氧化亚氮排放状况

A better understanding of nitrogen (N) transformation in agricultural soils is crucial for the development of sustainable and environmental-friendly N fertilizer management and the proposal of effective N₂O mitigation strategies. This study aimed: i) to elucidate the seasonal dynamic of gross nitrification rate and N2O emission, ii) to determine the influence of soil conditions on the gross nitrification, and iii) to confirm the relationship between gross nitrification and N₂O emissions in the soil of an apple orchard in Yantai, Northeast China. The gross nitrification rates and N₂O fluxes were examined from March to October in 2009, 2010, and 2011 using the barometric process separation (BaPS) technique and the static chamber method. During the wet seasons gross nitrification rates were 1.64 times higher than those under dry season conditions. Multiple regression analysis revealed that gross nitrification rates were significantly correlated with soil temperature and soil water-filled pore space (WFPS). The relationship between gross nitrification rates and soil WFPS followed an optimum curve peaking at 60% WFPS. Nitrous oxide fluxes varied widely from March to October and were stimulated by N fertilizer application. Statistically significant positive correlations were found between gross nitrification rates and soil N₂O emissions. Further evaluation indicated that gross nitrification contributed significantly to N₂O formation during the dry season (about 86%) but to a lesser degree during the wet season (about 51%). Therefore, gross nitrification is a key process for the formation of N₂O in soils of apple orchard ecosystems of the geographical region.     

Effects of forest management on carabid beetles in Belgium: implications for biodiversity conservation

We sampled the carabid beetles in 22 forests managed by six different silvicultural systems, defined by treatment and tree species composition: even-aged conifer, even-aged beech, even-aged oak, uneven-aged conifer, uneven-aged beech and group mixed (beech + conifer). In each of these forests, we placed pitfall traps in young, medium-aged and mature stands (3 stages). We evaluated the effect of treatment, tree species composition, silvicultural system, stage and habitat type (silvicultural system + stage) on indicators of community conservation value and ecological structure. The species composition and the ecological structure of carabid beetles of the managed stands were then compared to that of nine unmanaged stands (without tree exploitation). In the managed forests, species richness was highest in large young stands (3-10 years old) and in forests managed by even-aged systems (with large clear-cuts), mainly due to eurytopic and opportunist carabid species with high dispersal abilities. Oak and beech, uneven-aged, and mature stands were mainly inhabited by typical forest species, and even-aged conifer stands mainly by ubiquitous species. Several typical forest species recorded in unmanaged stands were lacking from the managed forests. Large scale clear-cutting allows open-habitat species to enter the forest, which increases the species richness at a landscape level but can disfavour typical forest species by competition. Long rotations should be implemented and more areas left unmanaged in Belgium, in order to help typical forest species to re-colonise managed forests.