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761.
To quantify the possible sources of the high ambient ozone concentration in the low troposphere over Taiwan, ozone sounding data from a two-year intensive field measurement program conducted in April and early May of 2004 and 2005 in northern Taiwan has been examined. We found that the vertical ozone distributions and occurrence of enhanced ozone in the lower troposphere (below 6 km) mainly resulted from (1)Type NE: the long-range transport of ozone controlled by the prevailing northeasterly winds below 2 km, (2)Type LO: the local photochemical ozone production process, and (3)Type SW: the strong southwest/westerly winds aloft (2–6 km). In the boundary layer (BL), where Asian continental outflow prevails, the average profile for type NE is characterized by a peak ozone concentration of nearly 65 ppb at about 1500 m altitude. For type LO, high ozone concentration with an average ozone concentration greater than 80 ppb was also found in the BL in the case of stagnant atmospheric and sunny weather conditions dominated. For type SW, significant ozone enhancement with average ozone concentration of 70–85 ppb was found at around 4 km altitude. It is about 10 ppb greater than that of the types NE and LO at the same troposphere layer owing to the contribution of the biomass burning over Indochina. Due to Taiwan's unique geographic location, the complex interaction of these ozone features in the BL and aloft, especially features associated with northeasterly and south/southwesterly winds, have resulted in complex characteristics of ozone distributions in the lower troposphere over northern Taiwan.  相似文献   
762.
The effect of sampling protocol on ambient air hydrocarbon mixing ratios was examined on eight sampling days in Los Angeles during 2007 and 2008. Four protocols, which were based on previously published multi-city urban hydrocarbon studies in the United States, were compared and differences were quantified. Whole air canister samples were collected and analyzed for nonmethane hydrocarbons (NMHCs). Differing sampling protocols resulted in large differences in mixing ratios, up to an order of magnitude, for certain NMHCs on the same sampling day. However, the magnitude of the variability between NMHC levels obtained by the four protocols was not consistent throughout the eight sampling days. It was found that sampling time, followed by sampling location, had the greatest influence on the magnitude of the mixing ratio. Ratios between hydrocarbons, often used in urban studies to gain information on emission sources, also varied depending on the protocol used. Comparison of absolute NMHC mixing ratios collected in urban environments using differing sampling protocols should be made with care.  相似文献   
763.
Atmospheric ions are produced by many natural and anthropogenic sources and their concentrations vary widely between different environments. There is very little information on their concentrations in different types of urban environments, how they compare across these environments and their dominant sources. In this study, we measured airborne concentrations of small ions, particles and net particle charge at 32 different outdoor sites in and around a major city in Australia and identified the main ion sources. Sites were classified into seven groups as follows: park, woodland, city centre, residential, freeway, power lines and power substation. Generally, parks were situated away from ion sources and represented the urban background value of about 270 ions cm?3. Median concentrations at all other groups were significantly higher than in the parks. We show that motor vehicles and power transmission systems are two major ion sources in urban areas. Power lines and substations constituted strong unipolar sources, while motor vehicle exhaust constituted strong bipolar sources. The small ion concentration in urban residential areas was about 960 cm?3. At sites where ion sources were co-located with particle sources, ion concentrations were inhibited due to the ion-particle attachment process. These results improved our understanding on air ion distribution and its interaction with particles in the urban outdoor environment.  相似文献   
764.
765.
According to various reports, climate change is responsible for the change in rainfall amount and pattern accompanied by the various degrees of extreme events in Sahelian West Africa in recent years. Other reports also suggest that there has been a “recovery” of the rainy season (Nicholson 2005). In this study, temporal characteristics of meteorological droughts in the Volta basin, a semi-arid region in West Africa, are investigated in order to provide a guide for sustainable water resource management. For this purpose, drought intensity, areal extent and recurrence frequency is analysed using the standardised precipitation index (SPI) for a time series between 1961 and 2005 from 52 meteorology stations across the Volta basin. Using this analysis the severity of the historical droughts of 1961, 1970, 1983, 1992 and 2001 that occurred in the region are assessed and their intensity, areal extent and return periods are obtained. The drought intensity is lower than −2.0 over nearly 75% of the region, meaning that a major part of the region was under extreme drought conditions during this year. The drought of 1983/1984 has a probability of occurrence of up to 0.1 from records spanning 44 years. The areal extent of extreme drought conditions is about 90% during this drought period.  相似文献   
766.
This paper examines quantitatively the patterns of collaboration over geographical boundaries in the emerging field of sustainability science by empirically analyzing the bibliometric data of scientific articles. The results indicate that an increasing number of countries are engaged in research on sustainability, with the proportion of articles published through international collaboration rising as well. The number of countries engaged in international collaboration on sustainability research has been increasing, and the diversity of countries engaged in research collaboration beyond national borders is also increasing. The geographical patterns of collaboration on sustainability show that research collaboration tends to be conducted between countries which are geographically located closely, suggesting that communication and information exchange might be limited within the regional clusters. The focused fields of research activities on sustainability are significantly different between countries, as each country has its focused fields of research related to sustainability. The specialization of research activities is also observed in international collaboration. While these patterns of international collaboration within regional clusters focusing on specific fields could be effective in promoting the creation, transmission, and sharing of knowledge on sustainability utilizing the already existing regional networks, they could pose a serious obstacle to collecting, exchanging, and integrating diverse types of knowledge, especially when it is necessary to deal with problems involving large-scale complex interactions with long-term implications, such as climate change. It would be of critical importance to establish inter-regional linkages by devising appropriate institutional arrangements for global research collaboration on sustainability science.  相似文献   
767.
This paper investigates the structure, function and wealth distribution within the Pangasius hypophthalmus and Henicorhynchus spp./Labiobarbus spp. value chains in the Mekong Delta of Vietnam. The analysis is driven by key questions relating to the form and function of value chains, their contribution to the livelihoods of farmers and fishers, the effectiveness of government policy and the potential for value chain governance mechanisms, such as contracts and certification, to steer towards sustainable production. The results indicate that actors in the high value Pangasius hypopthalmus export chain have a higher potential income, but face considerably higher economic vulnerability from global markets. Alternatively, Henichorhychus/Labiobarbus spp. fishers are severely constrained in their ability to negotiate higher prices for their fish but appear to be less vulnerable to economic and environmental change. The paper concludes that for value chain governance to improve the livelihoods of fishers and farmers in both high and low value chains, new arrangements are needed that better accommodate customary institutions and informal market relations.  相似文献   
768.
Developed countries are major markets for developing country fresh produce. Demand by developed country consumers for spotless produce has encouraged developing country consumers to rely increasingly on pesticides in producing fresh export vegetables. However developed country pesticide standards enacted in response to reports of increased farmer and farm worker pesticide poisoning and the food safety scandals of the 1980s and 1990s require changes in the way growers use pesticides. The EU has especially developed stringent food safety standards relating to, among other things, pesticide usage. Under EU pesticide standards (EU-PS) farmers are trained by their buyers on safe use of pesticides and then closely monitored under contract. This paper looks at the impact of these standards on developing country farmers’ use of alternative pest management practices, pesticide protective clothing and the actual usage of pesticides. It finds that compliance with EU-PS increases the use of alternative pest management practices and protective clothing. However, EU-PS has mixed effect on the quantity of pesticides used. The paper also finds that farmer’s education and access to information play an important role in the use of alternative pest management practices. The paper concludes that EU-PS encourage the use of alternative pest management practices and pesticide protective gear in production of fresh export vegetables. The findings imply that EU-PS promote environmentally-friendly methods of production of fresh export vegetables in developing countries.  相似文献   
769.
While the role Aboriginal people play in environmental governance programs are often underpinned by the Crown, Aboriginal peoples are ratifying negotiated agreements with mining proponents to ensure their issues and concerns are addressed. This paper examines Aboriginal participation in mine development to show how more inclusive social and environmental development models can support a more sustainable development. Through two complementary processes, negotiated agreements and environmental impact assessment, Aboriginal peoples are maximizing their benefits and minimizing the adverse impacts of a project to create a more sustainable resource development. Case study analysis of the Galore Creek Project in northwestern British Columbia, Canada, illustrates how environmental impact assessment and negotiated agreements can co-exist to positively contribute to a successful mineral development, and hence operationalize sustainability within this context.  相似文献   
770.
Negotiations of the Kyoto Protocol reached what has been called a moral position on biocarbon sinks which saw important limitations on their use in the Clean Development Mechanism (CDM), the Protocol’s main carbon offset system. After outlining this moral position, this article examines the consequences of these limitations on the viability of community forest participation in the CDM through a case study of three community forests in West Africa. Results suggest that there is significant carbon mitigation potential from forest conservation, reforestation as well as from improved fuelwood cookstoves at the community level. Yet under the current rules of the CDM, little of this overall carbon mitigation potential is able to be realized. Using qualitative research methodologies, it was learned that community respondents showed a pragmatic, yet cautious interest in the CDM while also emphasizing a need for land-use flexibility. The paper closes with a political discussion of the “‘moral position” on biocarbon sinks in the carbon market and concludes with policy recommendations for biocarbon sinks, in both the CDM and REDD, in the post-Kyoto climate change regime.  相似文献   
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