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A stochastic model for man-caused forest fires is developed for a forest with given environmental conditions which is represented by an index. This model is then generalized to take into account both man-caused and natural fires and the mean and the variance of the number of fires is derived. Fitting procedure for given data is suggested.  相似文献   
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We developed a cost-effective and sensitive spectrophotometric method for the determination of arsenic at trace level using a new reagent, leuco malachite green. Here we show that, arsenic reacts with potassium iodate in acidic conditions to liberate iodine, and the liberated iodine selectively oxidizes leuco malachite green to malachite green dye. We studied the Beer’s law at 617 nm, which showed linearity over the concentration range 0.09–0.9 μg ml−1 of arsenic. We show that the molar absorptivity, Sandell’s sensitivity and detection limit of the method are 6.1 × 104 l mol−1 cm−1, 0.0012 μg cm−2 and 0.025 μg ml−1, respectively. We applied the developed method for the determination of arsenic in environmental samples.  相似文献   
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The central message of this paper is that natural forests have multiple uses and multiple users. The paper describes the crisis in Asian forestry and four failures which lie behind the crisis. The first failure is related to economic policy which has consistently underpriced timber, not accounting for the true cost of replacing the felled trees or the value of non-timber goods and services (including environmental services). The second failure stems from the lack of community involvement in managing forests. The third failure is that of forestry institutions which have not been able to adapt to changes required to meet new challenges — away from timber extraction towards environmental services and social forestry. The fourth failure arises from technological constraints, including difficulties in carrying out long-term research (to cover the 20–40 year time horizon in the forestry sector) and ineffective application of research results. A number of specific suggestions for moving toward sustained yield management in Asia are presented. The sustainable management of forests in Asia is crucial not only for indigenous peoples, the environment and economies of the countries of Asia, but also for the biodiversity and health of the global environment.  相似文献   
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Environmental Chemistry Letters - Polycyclic aromatic hydrocarbons are toxic pollutants which persist in the environment. Extraction of polycyclic aromatic hydrocarbons requires large volumes of...  相似文献   
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