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A qualitative method is described, using ultraviolet spectroscopy, to determine the source origins of polycyclic aromatic hydrocarbons present in the environment. The technique takes advantage of the fact that aromatic compounds exhibit strong absorption in the ultraviolet region. It offers a fast and convenient alternative to other methods, which normally require extensive sample clean-up to avoid or limit interference from other materials during analysis. In contrast, this method requires only basic column chromatography to isolate the compounds of interest. Examples of the application of the technique are presented; the results are corroborated by those previously obtained by other methods. 相似文献
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Tradeoffs,synergies and traps among ecosystem services in the Lake Victoria basin of East Africa 总被引:1,自引:0,他引:1
Brent M. Swallow Joseph K. Sang Meshack Nyabenge Daniel K. Bundotich Anantha K. Duraiappah Thomas B. Yatich 《Environmental Science & Policy》2009,12(4):504-519
Lake Victoria is a crucial ecosystem for over 25 million people in Kenya, Uganda, Tanzania, Rwanda and Burundi who live in the basin, and for the greater Nile river system downstream of the lake. Ecosystem management in the Lake Victoria basin has been highly extractive for most of the last 60 years, with the 1990s a period of marked decline in food production, economic contraction, rising poverty, increased burden of human disease, and more frequent floods. Lake Victoria itself is becoming eutrophic, with related problems of species extinctions and invasive species. There is evidence of poverty–environment traps: some households and areas appear to be caught in vicious cycles of low income, low investment in soil management, declines in soil fertility, and soil loss, while other households and areas are able to achieve higher incomes and investments, maintain soil fertility, and conserve soil on their farms.Concepts and approaches from the Millenium Ecosystem Assessment (MA) were applied in a study of ecosystem service tradeoffs, synergies and traps in two of the river basins that flow into Lake Victoria from Kenya (Yala and Nyando). Hydrologic units are the main geographic unit used in the analysis, with predictions of sediment yield serving as the main measure of regulating services. Provisioning services are evaluated through a spatially disaggregated analysis of agricultural production, yield and area that combines spatial data from aerial photographs with division-level price and yield estimates.The results illustrate considerable year-to-year variation in land use, agricultural production and sediment yield in the two basins. While overall production appears to be relatively stable at the basin level, there have been shifts in the geographic locus of production toward the upper parts of both basins. A spatial overlay of production and sediment yield indicates that different parts of the basins exhibit tradeoffs, synergies and traps. Results from this study have multiple uses in rural planning, agricultural investment, and watershed management. The results also suggest that the poverty traps conceptual framework may help to enrich the interpretative content of the MA approach. 相似文献
3.
Zhang Yao Liu Wenxin Khan Sufyan Ullah Swallow Brent Zhou Chaohui Zhao Minjuan 《Environmental science and pollution research international》2022,29(5):6886-6899
Environmental Science and Pollution Research - Economies that depend on natural resources can experience a resource drag effect when economic growth is limited by constraints on the availability of... 相似文献
4.
The elongated eye span of male Diopsid flies is a sexually selected character that scales positively with body size. Previously,
the duration of agonistic contests was found to increase as rival body size and eye span disparities decreased. Hence, along
with its role in mate choice, eye span seems to facilitate mutual assessment of rival size. However, such results are also
expected in the absence of rival assessment, when each individual persists according to its own size-dependent internal threshold.
Here, we reanalyze these contests to distinguish between these two hypotheses using two measures of size: body length and
eye span. Mutual assessment predicts that contest duration should increase with loser size and decrease with winner size.
In contrast, our results were more consistent with self-assessment: We found a positive relationship between loser size and
contest duration, whereas winner size did not affect contest duration. Thus, flies did not appear to assess the size of their
rivals, indicating that the mutual assessment function of eye span elongation may be less important than previously suspected.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
PW Kok HY Ong MK Wong WK Au KT Tan WH Phoon CN Ong 《Environmental monitoring and assessment》1997,44(1-3):425-431
Occupational exposure to benzene was measured in two gasoline marketing terminals and five major refineries in Singapore. A total of 280 workers were monitored over two years. This assessment was carried out with two primary objectives: (1) To find out the extent of occupational exposure to benzene in the petroleum industry in Singapore, (2) To identify suitable biomarkers for monitoring of low levels of benzene exposure. The exposure was measured in five different categories of petroleum and petrochemical workers, i.e., truck drivers, despatch assistant, process operators, oil movements operators and laboratory technicians. The results revealed wide variations in exposure, from 0.01 to 13.6 ppm for personal time weighted average (TWA) exposure over the whole workshift. The exposure of truck drivers appeared to be the highest, with geometric mean (GM) of 1.98 ppm (ranged from 0.25 to 13.6 ppm). The average benzene exposure for process operators was relative low with a GM of 0.04 ppm. Lowest benzene exposure was found in the laboratory technicians, with a GM of 0.02 ppm. As cigarette smoking is known to affect metabolism of benzene, data analyses on the relationships with environmental exposure were conducted only on the 190 nonsmokers. The results showed that urinary trans, trans-muconic acid (ttMA), unmetabolized benzene in urine (UBZ) and benzene in blood (BBZ) were better biomarkers for low level benzene exposure as compared to urinary phenolic metabolites in urine, such as hydroquinone, phenol and catechol. 相似文献
6.
Forestry-based carbon sequestration projects in Africa: Potential benefits and challenges 总被引:3,自引:0,他引:3
Carbon sequestration through forestry and agroforestry can help mitigate global warming. For Africa, carbon sequestration also represents an opportunity to fund sustainable development through financial inflows. However, with a low share of global carbon trade, there are strong concerns that African countries are losing out on this valuable opportunity. Through a comprehensive review of 23 carbon sequestration projects across 14 countries, this paper discusses ways to overcome critical challenges to scale up carbon investments in Africa. These projects are expected to sequester 26.85 million tCO2 beyond the baseline situation. Within the continent, East Africa is the preferred destination for carbon investors. Most projects are non‐Kyoto compliant and represent voluntary emission reductions. While project benefits such as increased local incomes and improved natural resources are promising, there are concerns that conversion of grasslands into tree plantations can harm local ecosystems. Insecure land tenure constrains new investments and increases the risk that local communities will lose access to forests. Another challenge is that projects with smallholders have high transaction costs. These costs can be overcome by building strong community institutions and simplifying project guidelines. To attract more projects, African governments will need to build their capacity to identify relevant opportunities. 相似文献
7.
Understanding the mechanisms and determinants of conflict resolution is of great theoretical and practical importance because the outcome of contests between males over limited resources such as mates, territories, and food has profound fitness consequences. Despite the large literature on the theory of conflict resolution, relatively few empirical studies explicitly test predictions related to contest structure for these models. In sexually dimorphic species of stalk-eyed flies (Diopsidae), males engage in characteristic aggressive interactions over both females and food resources. We used sequential analysis of aggressive interactions between dyads of male stalk-eyed flies to investigate patterns of escalation, behavioral matching, and physical contact in order to distinguish between three common models of conflict resolution: the sequential assessment model, the cumulative assessment model, and the energetic war of attrition. Stalk-eyed flies were shown to engage in both low- and high-intensity behaviors during interactions with patterns of escalation and no de-escalation. Aggressive interactions did not demonstrate behavioral matching between winners and losers. Stalk-eyed flies also escalated to behaviors that included physical contact without injuries. Our results provide support for the sequential assessment model based on patterns of escalation with no de-escalation, behavioral mismatching, and behaviors which include physical contact but no injuries. 相似文献
8.
Stephen K. Swallow Peter J. Parks David N. Wear 《Journal of Environmental Economics and Management》1990,19(3)
This paper challenges common assumptions about convexity in forest rotation models which optimize timber plus nontimber benefits. If a local optimum occurs earlier than the globally optimal age, policy based on marginal incentives may achieve suboptimal results. Policy-relevant nonconvexities are more likely if (i) nontimber benefits dominate for young stands while the optimal age depends primarily on timber benefits, or (ii) nontimber benefits dominate for mature stands and also determine the optimal age. Nonconvexities may create either temporary or persistent difficulties. Policymakers may improve efficiency by exploiting the relationship between the timber-only optimum and the global optimum. 相似文献
9.
Dana Marie Bauer Stephen K. Swallow Robert J. Johnston 《Journal of Land Use Science》2017,12(5):351-374
Most land-use surveys of exurban residents focus on eliciting preferences for residential development and open space conservation. This article, in contrast, reports on a stated preference study of exurban residents that assesses the relative attractiveness of a variety of commercial and recreational land uses. Focus group participants and town planners proclaimed a demand for certain commercial services such as modern grocery stores and fine-dining restaurants, but survey respondents generally exhibit a strong preference for no additional development beyond the current rate of development. Results show that if additional development is to occur, then recreational services are generally preferred over more traditional commercial development. Combining two commercial services in a single development project are strongly preferred to stand-alone developments. Our approach illustrates how planners may uncover misconceptions about and priorities for land conversion through examining residents’ preferences. 相似文献
10.
Previous experiences can play a significant role in determining future behaviors. Winner and loser effects, where the outcome
of previous aggressive encounters influences the behavioral approach to and outcomes of future conflicts, have been documented
in many taxa and illustrate this phenomenon. These effects are prevalent in species that interact frequently because modulation
of these potentially costly social interactions may influence fitness. Stalk-eyed flies of the dimorphic species Teleopsis dalmanni engage in frequent fights over food resources, as well as over access to harems of females, with larger males typically prevailing
when size disparities exist. However, whether and how prior experience influences fighting decisions and outcomes remains
unexplored. To test for winner and loser effects in stalk-eyed flies, sexually mature flies were paired in size-mismatched
dyads to establish winning and losing experiences. After their first contest, the flies were paired with size-matched individuals
and allowed to interact. We determined whether an initial winning or losing experience significantly altered the outcome probabilities
in the second size-matched encounter. Initial winning experience did not significantly affect the second interaction, providing
no evidence for a winner effect. However, initial losers were significantly more likely to lose a subsequent interaction which
provides evidence for a loser effect in stalk-eyed flies. In addition, smaller males experienced an increased probability
of losing their second interaction regardless of prior winning or losing experience. This effect was not seen in large males.
Our data suggest that the loser effects we observed, which were more pronounced in small males, could result from the energetic
costs of fighting that they were less able to absorb than large males. 相似文献
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