Tracing sediment loss from eroding farm tracks using a geochemical fingerprinting procedure combining local and genetic algorithm optimisation

Eroding farm tracks represent important spatially distributed features in many agricultural landscapes and there is concern over their role in catchment sediment problems. It is, however, important to place eroding farm tracks in the context of catchment sediment sources more generally, especially since the former afford potential for targeted sediment mitigation. A sediment source tracing procedure was therefore used to assess the importance of eroding farm track surfaces as a contemporary primary suspended sediment source relative to inputs from pasture or cultivated topsoils and channel banks/subsurface sources, in the upper River Piddle catchment (~ 100 km²), in southern England. The study provided a timely opportunity to assess the performance of both local and global (genetic algorithm; GA) optimisation techniques in the sediment geochemistry mass balance modelling used to apportion sources. Over the duration of the study, average median source contributions for individual time-integrated suspended sediment samples collected from three sub-catchments ranged between 1 ± 1 and 19 ± 3% for farm track surfaces, 31 ± 3 and 55 ± 2% for pasture topsoils, 1 ± 1 and 19 ± 1% for cultivated topsoils and 23 ± 2 and 49 ± 1% for channel banks/subsurface sources. Comparison of the local and GA optimisation techniques demonstrated that GA with random initial values improved the minimisation of the objective functions compared to local searching by 0.01-0.04% of 5000 repeat Monte Carlo iterations. GA informed by the outputs of the local optimisation as initial values improved corresponding performance by 0.05-0.20%. These findings increased confidence in the outputs from the local optimisation mass balance modelling, but fingerprint property datasets should be treated on an individual basis. Future sediment source tracing studies should always endeavour to combine local and global search tools to avoid the risk of using localised solutions for source apportionment estimates.     

Addressing climate change in comfort standards

According to the Buildings Energy Data Book published by the U.S. Department of Energy, in 2006 the building sector consumed 38.9% of the total primary energy used in the United States. Of this energy, 34.8% is used by buildings for space heating, ventilation, and air conditioning. This energy often involves the combustion of fossil fuels, contributing to carbon dioxide emissions and climate change. Even if greenhouse gas concentrations are stabilized in the atmosphere, extreme climate events and sea level rise will continue for several centuries due to inertia of the atmosphere. Therefore, adaptation will be a necessary compliment to carbon dioxide mitigation efforts. This paper argues that both mitigation of greenhouse gases and adaptation to climate change should be added to our building codes and standards. Since space heating, ventilation, and air-conditioning utilize a large amount of energy in buildings, we should begin by redefining our thermal comfort standards and add strategies that mitigate carbon dioxide emissions and adapt to predicted climate variability.     

Experimental mitigation of NO x emission in exhaust gases of CI engine fuelled with methyl ester of cottonseed oil blend

ABSTRACT

This paper discusses the development of a B20 cottonseed oil blend for passenger vehicle with vanadium-based Selective Catalytic Reduction (SCR) technology addition on exhaust system. SCR is a progressive emissions governor technology organism that injects a liquid-Urea (also called aqueous urea, Ad Blue or Diesel Exhaust Fluid) through an injector nozzle into the exhaust manifold of diesel engine. The methyl ester of cottonseed oil blend was analysed in a single cylinder, 4-stroke, computerised water-cooled, diesel engine of 5.2?kW rated power for performance and emission characteristics with SCR. The results indicate that the emissions of the CI engine running on B20 blend with the catalytic convertor reduced NO _x emission up to 76% with different quantity of dosing. However, it is noted that the brake thermal efficiency is reduced slightly by 2% for SCR due to the back pressure created by the SCR system.     

贯彻落实《国家中长期教育改革和发展规划纲要(2010—2020年)》 深化全国化工学科教育改革

本文介绍了国际工程教育的发展态势,总结了近几年全国化工学科教育改革研究与实践进展,并根据《国家中长期教育改革和发展规划纲要(2010—2020年)》要求,提出了深化化工学科教育改革的建议。     

A review of low-temperature proton exchange membrane fuel cell degradation caused by repeated freezing start

Proton exchange membrane fuel cell (PEMFC) has advantages of zero emission, fast response and high-power density. There are still obstacles such as manufacturing cost, life span, infrastructure construction and subzero temperature star-up restricting commercialization of PEMFC. The low-temperature start-up is one of them that needs to be solved in the field of fuel cell vehicle. This paper presents research progresses involving PEMFC degradation caused by the low-temperature start-up. Degradation phenomena and mechanism under component-level caused by repeated freezing start, influencing factors and mitigation strategies are summarized and reviewed. Conclusions are made that frequent ice freezing and melting causes the membrane electrode assembly damaged irreversibly, the quality of cold start and low temperature influence the degradation strongly and purge after shutdown, better materials and optimal fuel cell structure design are helpful to reduce the impact of cold start on fuel cell performances. It is suggested that future work should be focused on optimizing strategies of the shutdown purge, promoting the quality of cold start, enhancing properties of the materials, improving internal structure design of stack and developing low-temperature attenuation models.     

Potential of native forests for the mitigation of greenhouse gases in Salta, Argentina

Carbon stocks were assessed in three archetypal forest ecosystems in the province of Salta, Argentina, namely Yungas, Chaco, and shrublands located around Chaco. Over a total area of about 7000 m², detailed measurements of woody biomass were conducted using structural information such as diameter at breast height (dbh), total height, and stem height. At the same time, the wet weight of herbaceous, shrubs, and litter was registered within that area. Soil samples were also collected to determine parameters such as bulk density and organic carbon. The above-ground tree biomass (AGB) was quantified by two non-destructive methods. This biomass was expressed from each reservoir studied in t.ha⁻¹ and the carbon content was then calculated using a factor of 0.5. Carbon stocks in the ecosystems studied were 162, 92, and 48 tC.ha⁻¹ for Yungas, Chaco, and shrublands, respectively. Our results show that carbon is concentrated in the soil or as AGB. The latter is the most important reservoir in Yungas, while the soil plays this role in the other two, drier environments. In the province of Salta, native forests play a significant role in the mitigation of greenhouse gases. Our results reveal the magnitude of carbon stocks in some characteristic regional native forests, and estimate their carbon sequestration potential. These results could be useful to inform policy makers in charge of negotiations related to conservation and sustainable management of native forests, and be a relevant input for the formulation of more comprehensive land use planning processes in the region.     

Regional differences in the factors that influence China’s energy-related carbon emissions,and potential mitigation strategies

Energy-related carbon emissions in China have increased significantly. To mitigate these emissions, it is necessary to estimate the trends (increase or decrease) and the magnitudes of the influences (tons of carbon emitted) as a result of four causal factors that affect emissions: GDP, economic structure, energy intensity, and fuel mix. To do so, we have divided the study period into three intervals (from 1995 to 2009) based on China’s three most-recent 5-year plans. We then divided China’s 30 provinces into four categories based on the individual and net effects of these factors on carbon emissions. On this basis, we discuss potential strategies for reducing China’s carbon emissions. Increasing GDP caused the largest increase in carbon emissions, whereas decreasing energy intensity significantly decreased emissions. Changes in the economic structure increased emissions, with the economic structure becoming more carbon-intensive; efforts to optimize the fuel mix slightly decreased emissions during the first and third periods, but increased emissions during the second period. Our analysis also revealed differences between provinces and regions, allowing local managers to focus on the most important problems for their area. To reduce future energy-related carbon emissions, China’s economic structure, energy intensity, and fuel mix must all be improved.     

Eco-driving: An overlooked climate change initiative

The actions individuals can take to mitigate climate change are, in the aggregate, significant. Mobilizing individuals to respond personally to climate change, therefore, must be a complementary approach to a nation's climate change strategy. One action item overlooked in the United States has been changing driver behavior or style such that eco-driving becomes the norm rather than the exception. Evidence to date indicates that eco-driving can reduce fuel consumption by 10%, on average and over time, thereby reducing CO₂ emissions from driving by an equivalent percentage. A sophisticated, multi-dimensional campaign, going well beyond what has been attempted thus far, will be required to achieve such savings on a large scale, however, involving education (especially involving the use of feedback devices), regulation, fiscal incentives, and social norm reinforcement.     

Keeping warming within the 2 °C limit after Copenhagen

The object of the United Nations Climate Change Conference in Copenhagen in December 2009 was to reach an agreement on a new international legal architecture for addressing anthropogenic climate change post-2012. It failed in this endeavour, producing a political agreement in the form of the Copenhagen Accord. The Accord sets an ambitious goal of holding the increase in the global average surface temperature to below 2 °C. This paper describes 45 CO₂-only mitigation scenarios that provide an indication of what would need to be done to stay within the 2 °C limit if the international climate negotiations stay on their current path. The results suggest that if developed countries adopt a combined target for 2020 of ≤20% below 1990 levels, global CO₂ emissions would probably have to be reduced by ≥5%/yr, and possibly ≥10%/yr, post-2030 (after a decade transitional period) in order to keep warming to 2 °C. If aggressive abatement commitments for 2020 are not forthcoming from all the major emitting countries, the likelihood of warming being kept within the 2 °C limit is diminutive.