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191.
A High‐Resolution National‐Scale Hydrologic Forecast System from a Global Ensemble Land Surface Model 下载免费PDF全文
Alan D. Snow Scott D. Christensen Nathan R. Swain E. James Nelson Daniel P. Ames Norman L. Jones Deng Ding Nawajish S. Noman Cédric H. David Florian Pappenberger Ervin Zsoter 《Journal of the American Water Resources Association》2016,52(4):950-964
Warning systems with the ability to predict floods several days in advance have the potential to benefit tens of millions of people. Accordingly, large‐scale streamflow prediction systems such as the Advanced Hydrologic Prediction Service or the Global Flood Awareness System are limited to coarse resolutions. This article presents a method for routing global runoff ensemble forecasts and global historical runoff generated by the European Centre for Medium‐Range Weather Forecasts model using the Routing Application for Parallel computatIon of Discharge to produce high spatial resolution 15‐day stream forecasts, approximate recurrence intervals, and warning points at locations where streamflow is predicted to exceed the recurrence interval thresholds. The processing method involves distributing the computations using computer clusters to facilitate processing of large watersheds with high‐density stream networks. In addition, the Streamflow Prediction Tool web application was developed for visualizing analyzed results at both the regional level and at the reach level of high‐density stream networks. The application formed part of the base hydrologic forecasting service available to the National Flood Interoperability Experiment and can potentially transform the nation's forecast ability by incorporating ensemble predictions at the nearly 2.7 million reaches of the National Hydrography Plus Version 2 Dataset into the national forecasting system. 相似文献
192.
Nitrate has become an increased regulatory concern due to gradual deterioration of surface and groundwater quality primarily related to widespread fertilizer use. Remediation of nitrate is a relatively straightforward process; however, nitrate impacts to groundwater are often a symptom of a sustained source from another nitrogen form (e.g., ammonia, ammonium nitrate, urea), analogous to how nonaqueous phase liquid can serve as a long‐term source of volatile organic compounds in groundwater. Understanding the various nitrogen transformation reactions when selecting, implementing, or documenting a remedy associated with nitrate is therefore critical to successfully reaching remedial endpoints. Case studies are presented that highlight in situ remedial successes with nitrogen‐impacted groundwater and discuss the key considerations that should be factored into remedy application. ©2015 Wiley Periodicals, Inc. 相似文献
193.
Jerome S. Puskin Christopher B. Nelson 《Journal of the Air & Waste Management Association (1995)》2013,63(7):915-920
Indoor radon has been judged to be the most serious environmental carcinogen which the EPA must address for the general public. The optimal strategy for dealing with this problem depends on the magnitude of the risk, how the risk is distributed within the population, as well as the effectiveness and costs of mitigation measures. Based on current exposure and risk estimates, radon exposure in single-family houses may be a causal factor in roughly 20,000 lung cancer fatalities per year. Most of these projected fatalities are attributable to exposures in houses with average or moderately elevated radon levels (below 10 pCi/L). Hence to appreciably reduce radon-induced lung cancers, remediation efforts must include houses not highly elevated in radon. From either an individual risk or a cost-benefit standpoint, reduction of a few pCi/L per home appears to be justified. The optimal strategy for dealing with the indoor radon problem depends on the magnitude of the risk per unit exposure, the distribution of exposures in houses, and the effectiveness and costs of mitigation. EPA’s current views with respect to these factors and the associated uncertainties are discussed. 相似文献
194.
Steven H. Cadle Patricia Mulawa Eric C. Hunsanger Ken Nelson Ronald A. Ragazzi Richard Barrett 《Journal of the Air & Waste Management Association (1995)》2013,63(9):164-174
ABSTRACT A study of particulate matter (PM) emissions from in-use, light-duty vehicles was conducted during the summer of 1996 and the winter of 1997 in the Denver, CO, region. Vehicles were tested as received on chassis dynamometers on the Federal Test Procedure Urban Dynamometer Driving Schedule (UDDS) and the IM240 driving schedule. Both PM10 and regulated emissions were measured for each phase of the UDDS. For the summer portion of the study, 92 gasoline vehicles, 10 diesel vehicles, and 9 gasoline vehicles with visible smoke emissions were tested once. For the winter, 56 gasoline vehicles, 12 diesel vehicles, and 15 gasoline vehicles with visible smoke were tested twice, once indoors at 60 °F and once outdoors at the prevailing temperature. Vehicle model year ranged from 1966 to 1996. Impactor particle size distributions were obtained on a subset of vehicles. Continuous estimates of the particle number emissions were obtained with an electrical aerosol analyzer. This data set is being provided to the Northern Front Range Air Quality Study program and to the State of Colorado and the U.S. Environmental Protection Agency for use in updating emissions inventories. 相似文献
195.
Michael J. McFarland Glenn R. Palmer Scott Peters Arthur C. Olivas Tim M. Nelson 《Journal of the Air & Waste Management Association (1995)》2013,63(3):365-372
Abstract To effectively reduce the environmental compliance costs associated with meeting specific requirements under the Aerospace Manufacturing and Rework Facility’s National Emission Standard for Hazardous Air Pollutants rule, the U.S. Environmental Protection Agency’s (EPA) Data Quality Objective (DQO) process has been proposed as a suitable framework for developing a scientifically defensible surface compliance monitoring program. By estimating the variability associated with the air cap pressure of high-volume, low-pressure (HVLP) surface-coating spray equipment, the number of monitoring samples necessary for an affected facility to claim compliance with a desired statistical confidence level was established. Using data taken from the pilot test facility, the DQO process indicated that the mean of at least 21 HVLP air cap pressure samples taken over the compliance period must be ≤10 pounds per square inch (psig) gauge for the facility to claim regulatory compliance with 99.99% statistical confidence. Fewer compliance samples could be taken, but that decision would lead to a commensurate reduction in the compliance confidence level. Implementation of the DQO-based compliance sampling plan eliminates the need for an affected facility to sample all regulated HVLP surface-coating processes while still maintaining a high level of compliance assurance. 相似文献
196.
Agreement between breast milk dioxin levels by CALUX bioassay and chemical analysis in a population survey in Hong Kong 总被引:1,自引:0,他引:1
Chemically-activated luciferase gene expression (CALUX) bioassay and gas chromatography/mass spectrometry (GC/MS) are used to determine dioxin levels in food and humans. Valid measures of the agreement between the two methods would improve interpretation of bioassay results. Paired breast milk samples from 250 mothers, as 11 pooled samples, were analysed by GC/MS for total WHO-TEQ (7 polychlorinated dibenzo-para-dioxins, 10 polychlorinated dibenzofurans and 12 dioxin-like polychlorinated biphenyls) and as individual samples by CALUX. Mean difference between total WHO-TEQ (weighted by TEF system derived in 1997) and mean CALUX-TEQ in each pool was 1.6 pg/g fat (95% CI: 0.7, 2.4), indicating a statistically significant overestimation of CALUX-TEQ compared to WHO-TEQ, probably due to the presence of Ah-receptor agonists. CALUX estimated toxicity of 13 pg/g fat was greater than the WHO-TEQ by 0.9, 3.1 and 0.3 pg/g fat for mothers from Hong Kong, mainland China and overseas territories, respectively. When the 2005 TEF system was applied, a reduction of 14-26% in the WHO-TEQ and a larger but less disperse discrepancy between WHO-TEQ and CALUX-TEQ (3.9 pg/g fat, 95% CI: 3.5, 4.4) were observed. Our study suggested that the mothers' place of residence explained the discrepancy between CALUX-TEQ and WHO-TEQ and should be considered in inter-country comparisons for CALUX-TEQ. For regulatory purposes bioassays for detecting quantitative dioxin contents in any setting must be combined with adequate extraction, clean-up and validation with WHO-TEQs. The larger difference between the two measurements after using the new TEF system warrants further investigation. 相似文献
197.
Kahl JS Nelson SJ Fernandez I Haines T Norton S Wiersma GB Jacobson G Amirbahman A Johnson K Schauffler M Rustad L Tonnessen K Lent R Bank M Elvir J Eckhoff J Caron H Ruck P Parker J Campbell J Manski D Breen R Sheehan K Grygo A 《Environmental monitoring and assessment》2007,126(1-3):9-25
This paper is an overview of this special issue devoted to watershed research in Acadia National Park (Acadia NP). The papers
address components of an integrated research program on two upland watersheds at Acadia NP, USA (44° 20′ N latitude; 68° 15′
E longitude). These watersheds were instrumented in 1998 to provide a long-term foundation for regional ecological and watershed
research. The research was initiated as part of EPA/NPS PRIMENet (Park Research and Intensive Monitoring of Ecosystems Network),
a system of UV-monitoring stations and long-term watershed research sites located in US national parks. The initial goals
at Acadia NP were to address research questions about mercury, acid rain, and nitrogen saturation developed from prior research.
The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in
1947. There is no evidence of fire in the reference watershed for several hundred years. We are testing hypotheses about controls
on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The unburned 47-ha Hadlock
Brook watershed is 70% spruce-fir mature conifer forest. In contrast, burned 32-ha Cadillac Brook watershed, 4 km northeast
of the Hadlock watershed, is 20% regenerating mixed northern hardwoods and 60% shrub/rocky balds. Differences in atmospheric
deposition are controlled primarily by forest stand composition and age. The watersheds are gauged and have water chemistry
stations at 122 m (Cadillac) and 137 m (Hadlock); watershed maximum elevations are 468 and 380 m, respectively. The stream
water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest
vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed,
reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences
in internal cycling and bioavailabilty. 相似文献
198.
Schauffler M Nelson SJ Kahl JS Jacobson GL Haines TA Patterson WA Johnson KB 《Environmental monitoring and assessment》2007,126(1-3):39-53
Paleoecological reconstructions of forest stand histories for two upland watersheds at Acadia National Park in Maine were
completed to support related watershed chemistry studies. The project hypothesis was that forest type and fire history influence
long-term cycling and storage of atmospheric mercury and nitrogen within watersheds. The reconstructions document differences
in major vegetation composition and disturbance between the burned and unburned watersheds during the past several centuries.
Pollen and charcoal stratigraphies from organic sediment accumulations in forested wet depressions indicate that the present
experimental design of contrasting disturbance and forest histories has persisted during recent centuries. The unburned watershed
has been dominated by spruce (Picea rubens) and fir (Abies balsamea) for 500 years or more and has not recently burned or been substantially cleared. The burned watershed is dominated by a
heterogeneous forest of patchy hardwood, mixed wood, and softwood stands. A large portion of this watershed burned severely
in 1947 and probably more than once in the 1800s, and has supported heterogeneous successional forests for 200 years or longer.
Overall, these results support the underlying premise that the experimental design of this watershed research can be used
to infer landscape controls on biogeochemical processes. 相似文献
199.
200.
The influence of aridity and fire on holocene prairie communities in the eastern Prairie Peninsula 总被引:1,自引:0,他引:1
The role of climate and fire in the development, maintenance, and species composition of prairie in the eastern axis of the tallgrass Prairie Peninsula intrigued early North American ecologists. However, evaluation of the long-standing hypotheses about the region's environmental history has been hampered by the scarcity of paleorecords. We conducted multiproxy analyses on early and middle Holocene sediments from two Illinois, USA, lakes to assess long-term climatic, vegetational, and fire variability in the region. Sediment mineral composition, carbonate delta18O, ostracode assemblages, and diatom assemblages were integrated to infer fluctuations in moisture availability. Pollen and charcoal delta13C were used to reconstruct vegetation composition, and charcoal influx was used to reconstruct fire. Results indicate that fire-sensitive trees (e.g., Ulmus, Ostrya, Fraxinus, and Acer saccharum) declined and prairie taxa expanded with increased aridity from 10,000 yr BP to 8500 yr BP. Between approximately 8500 yr BP and approximately 6200 yr BP, aridity declined, and prairie coexisted with fire-sensitive and fire-tolerant (e.g., Quercus and Carya) trees. After approximately 6200 yr BP, prairie taxa became dominant, although aridity was not more severe than it was around 8500 yr BP. Along with aridity, fire appears to have played an important role in the establishment and maintenance of prairie communities in the eastern Prairie Peninsula, consistent with the speculations of the early ecologists. Comparison of our data with results from elsewhere in the North American midcontinent indicates that spatial heterogeneity is a characteristic feature of climatic and vegetational variations on millennial time scales. 相似文献