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151.
Monitoring of contaminant accumulation in fish has been conducted in East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee
since 1985. Bioaccumulation trends are examined over a twenty year period coinciding with major pollution abatement actions
by a Department of Energy facility at the stream’s headwaters. Although EFPC is enriched in many contaminants relative to
other local streams, only polychlorinated biphenyls (PCBs) and mercury (Hg) were found to accumulate in the edible portions
of fish to levels of human health concern. Mercury concentrations in redbreast sunfish were found to vary with season of collection,
sex and size of individual fish. Over the course of the monitoring, waterborne Hg concentrations were reduced >80%; however,
this did not translate into a comparable decrease in Hg bioaccumulation at most sites. Mercury bioaccumulation in fish did
respond to decreased inputs in the industrialized headwater reach, but paradoxically increased in the lowermost reach of EFPC.
As a result, the downstream pattern of Hg concentration in fish changed from one resembling dilution of a headwater point
source in the 1980s to a uniform distribution in the 2000s. The reason for this remains unknown, but is hypothesized to involve
changes in the chemical form and reactivity of waterborne Hg associated with the removal of residual chlorine and the addition
of suspended particulates to the streamflow. PCB concentrations in fish varied greatly from year-to-year, but always exhibited
a pronounced downstream decrease, and appeared to respond to management practices that limited episodic inputs from legacy
sources within the facility. 相似文献
152.
This paper considers the problem of reverse engineering strategies for trading in the financial markets. We investigate this problem in the context of a trading tournament in which student teams used delta hedging and other mechanisms to attempt to achieve benchmark performance in managing a hedge fund in a simulated market. Our hypothesis is that machine learning models can be trained to solve the apprenticeship learning problem; that is, these models can learn to trade like tournament participants. After reviewing classical return-matching approaches and recent work in inverse reinforcement learning, we propose a supervised learning methodology that makes use of recursive partitioning (RP). Our proposed RP approach is based on a feature representation for actions that, we argue, corresponds to the information structures readily available to tournament participants. RP achieves high accuracy in predicting the type and scale of participant trades and in tracking overall portfolio performance. Our results suggest that further research on our proposed approach is warranted and should include an expansion to testing on data from real markets. 相似文献
153.
Catherine R. Darst Philip J. Murphy Nathan W. Strout Steven P. Campbell Kimberleigh J. Field Linda Allison Roy C. Averill-Murray 《Environmental management》2013,51(3):786-800
Ensuring the persistence of at-risk species depends on implementing conservation actions that ameliorate threats. We developed and implemented a method to quantify the relative importance of threats and to prioritize recovery actions based on their potential to affect risk to Mojave desert tortoises (Gopherus agassizii). We used assessments of threat importance and elasticities of demographic rates from population matrix models to estimate the relative contributions of threats to overall increase in risk to the population. We found that urbanization, human access, military operations, disease, and illegal use of off highway vehicles are the most serious threats to the desert tortoise range-wide. These results suggest that, overall, recovery actions that decrease habitat loss, predation, and crushing will be most effective for recovery; specifically, we found that habitat restoration, topic-specific environmental education, and land acquisition are most likely to result in the greatest decrease in risk to the desert tortoise across its range. In addition, we have developed an application that manages the conceptual model and all supporting information and calculates threat severity and potential effectiveness of recovery actions. Our analytical approach provides an objective process for quantifying threats, prioritizing recovery actions, and developing monitoring metrics for those actions for adaptive management of any at-risk species. 相似文献
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155.
Sujoy B. Roy Paolo F. Ricci Karen V. Summers Chih-Fang Chung Robert A. Goldstein 《Journal of the American Water Resources Association》2005,41(5):1091-1108
To evaluate the long term sustainability of water withdrawals in the United States, a county level analysis of the availability of renewable water resources was conducted, and the magnitudes of human withdrawals from surface water and ground water sources and the stored water requirements during the warmest months of the year were evaluated. Estimates of growth in population and electricity generation were then used to estimate the change in withdrawals assuming that the rates of water use either remain at their current levels (the business as usual scenario) or that they exhibit improvements in efficiency at the same rate as observed over 1975 to 1995 (the improved efficiency scenario). The estimates show several areas, notably the Southwest and major metropolitan areas throughout the United States, as being likely to have significant new storage requirements with the business‐as‐usual scenario, under the condition of average water availability. These new requirements could be substantially eliminated under the improved efficiency scenario, thus indicating the importance of water use efficiency in meeting future requirements. The national assessment identified regions of potential water sustainability concern; these regions can be the subject of more targeted data collection and analyses in the future. 相似文献
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In the area of end-of-life vehicle (ELV) recycling, Japan passed the Automobile Recycling Law in January 2005, the first in Asia. Korea followed suit with the passage of the resource circulation method in 2009. China is expected make a new recycling law in 2011. In contribution to these initiatives, Tohoku University made a comparative analysis of ELV recycling laws, advance dismantling experiments and scenario analysis to promote international cooperation. This is envisioned to introduce ELV recycling system in Japan, China and Korea and in developing countries as well. 相似文献
160.
Das Basanta Kumar Roy Aparna Som Sukanya Chandra Ganesh Kumari Suman Sarkar Uttam Kumar Bhattacharjya Birendra Kumar Das Archan Kanti Pandit Arun 《Environmental science and pollution research international》2022,29(6):8452-8463
Environmental Science and Pollution Research - The COVID-19 pandemic has created unprecedented human health crisis in recent global history with rippling social and economic effects. The outbreak... 相似文献