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761.
D. W. Johnson R. B. Susfalk T. G. Caldwell J. D. Murphy W. W. Miller R. F. Walker 《Water, Air, & Soil Pollution: Focus》2004,4(2-3):263-275
Estimates of C and N loss by gasification during a wildfire in a Jeffrey pine (Pinus Jeffreyii [Grev. and Balf.]) forest in Little Valley, Nevada are compared to potential losses in more mesic forests in the Integrated Forest Study (IFS). In Little Valley, the fire consumed the forest floor, foliage, and an unknown amount of soil organic matter, but little standing large woody material. On an ecosystem level, the fire consumed approximately equal percentages of C and N (12 and 9%, respectively), but a considerably greater proportion of aboveground N (71%) than C (21%). Salvage logging was the major factor in loss, and C lost from the site will not be replenished until forest vegetation is established and succeeds the current shrub vegetation. N2 fixation by Ceanothus velutinus [Dougl.] in the post-fire shrub vegetation appears to have more than made up for N lost by gasification in the fire over the first 16 yr, and may result in long-term increases in C stocks once forest vegetation takes over the site. N loss from the fire equaled > 1,000 years of atmospheric N deposition and > 10,000 years of N leaching at current rates. Calculations of C and N losses from theoretical wildfires in the IFS sites show similar patterns to those in Little Valley. Calculated losses of N in most of the IFS sites would equal many centuries of leaching. Conceptual models of biogeochemical cycling in forests need to include episodic events such as fire. 相似文献
762.
Kathleen J. Miller 《Journal of the American Water Resources Association》2005,41(2):257-265
ABSTRACT: A series of gravel terraces support a shallow aquifer that is the sole source of drinking water for three public water supplies and more than 400 private wells on the Greenfields Bench in west‐central Montana. Farming practices on the Greenfields Bench include irrigation of malting barley and the yearly application of herbicides for the control of weeds. The most commonly used herbicide (imazamethabenz‐methyl, U.S. trade name Assert®) has been found in the ground water on the Greenfields Bench. An experiment was conducted in 2000 and 2001 to characterize the transport of Assert and its acid metabolite to ground water under three irrigation methods: flood, wheel line sprinkler, and center pivot sprinkler. Results show that Assert concentrations in ground water are controlled by hydraulic loading rates of each irrigation method, Assert persistence in soil, hydraulic characteristics of the aquifer, and adsorption/desorption of Assert onto clay particles and organic matter. 相似文献
763.
Michael Greenberg K. Tyler Miller Karen Lowrie Mary Anne Carletta Joanna Burger 《补救:环境净化治理成本、技术与工艺杂志》2003,14(1):69-83
This article presents a database developed to determine the potential reuse of contaminated sites for primarily ecologically and culturally based activities. The database consists of 172 quantitative and qualitative measures of on‐site land suitability, ecological, cultural, and recreational value, and off‐site suitability, economic, and demographic information. Using sites owned by the U.S. Department of Energy (DOE) as a case study, the article evaluates the quality of available data and suggests ways of using it for planning ecologically sensitive remediation activities and future land use. This type of database can be developed and used by anyone who needs to select, review, or evaluate site remediation and future land use options. Also discussed are the challenges associated with compiling and using data that has been generated by many sources over several years. © 2003 Wiley Periodicals, Inc. 相似文献
764.
Richard H. French Julianne Miller Steve Curtis 《Journal of the American Water Resources Association》2003,39(2):477-486
ABSTRACT: On February 23–24, 1998, a frontal system moved across the U.S. Department of Energy's 3,500 km2 Nevada Test Site (NTS) and resulted in significant depths of precipitation at all recording gages on the NTS. A preliminary analysis suggested that this precipitation event was of the magnitude and duration for which many flood mitigation structures have been designed. Given the data and field observations available and the potential implications of the event on the methodologies used to size flood mitigation structures throughout the West, a detailed analysis of this event was undertaken. The goals of this study were to compare this event with the regulatory design precipitation event, compare the estimated peak flow rates from the rainfall/runoff model used to size the flood mitigation structures at a radioactive waste management site with the estimated peak flows from the precipitation event, and examine if modification of the standard source of the design depths of precipitation is warranted. 相似文献
765.
Theodore K. Miller Lawrence J. Onesti 《Journal of the American Water Resources Association》1988,24(6):1207-1217
ABSTRACT: Stream channel development is a complicated process involving many factors. A major goal of research in fluvial geomorphology is to develop an understanding of the relations between channel form, water discharge, and sediment discharge characteristics. The concept of thresholds has been introduced as an element in fluvial processes, with the implication that the factors involved in a process might change in some way as threshold boundaries are passed. This study is focused on the extent to which a particular regional boundary represents a threshold in the process of stream channel development. Twenty-four alluvial stream channels from the Great Plains region and 24 from the Central Lowlands region are compared with regard to the distributional form, central tendency and dispersion characteristics, and correlation structure of ten variables, including indicators of discharge, channel sediment, and channel morphology. The results suggest that these aspects of the data are very similar between the regions, except for certain differences in central tendency characteristics, which are assumed to reflect underlying differences between the regions in geology and climate. In general, the results support the idea that this regional boundary is not an effective threshold with respect to the stream channel development process, and that, therefore, stream channels develop in these environmentally distinct regions by way of a similar process. 相似文献
766.
J. W. Delleur W. L. Miller H. R. Potter 《Journal of the American Water Resources Association》1976,12(4):759-777
ABSTRACT The patterns of land use and their relationship to urban water resources are examined from the point of view of population growth, consumer behavior, and preferences of price, income, and land use controls. The changes that need to be made in present social attitudes or water resources laws to satisfy the desired new developments are examined. Several implementation methods that are feasible and effective for changing urban development patterns are considered as well as models for assessing alternate development plans. The needs for research are outlined. 相似文献
767.
768.
We determined the association between radionuclide deposition levels from nuclear testing at the Nevada Test Site (NTS) and
cancer mortality rates in 513 counties of the Midwestern states of Iowa, Illinois, Kansas, Missouri, and Nebraska. The 10-day
cumulative deposition for 54 radionuclides and 1-year cumulative deposition for 19 radionuclides were determined with isotope
ratios based on each test and 131I levels in the 513 counties obtained from the US National Cancer Institute’s 131I fallout study. Deposition calculations were done for each test and each radionuclide. Age-adjusted cancer mortality rates
for 84 organ-gender combinations for the periods 1950–1959, 1960–1969, 1970–1979, and 1979–1995 were used. Analyses included
permutation-based randomization tests for Spearman rank correlation (adjusted for multiple testing). Age-adjusted cancer mortality
rates for connective and soft tissue sarcoma, thymus, and female lymphosarcoma and cancer of the colon, brain, thyroid, and
uterus were significantly correlated with total fallout and total precipitation during 1951–1957 and 1962. 187W had the highest cumulative deposition density at 10 days postshot (2783 MBq/m2) among the NTS radionuclides considered. The most significant correlations were observed for 10-day cumulative deposition
density of 181W, 185W, 54Mn, 187W, 24Na, 185W, 199Au, 7Be, 60Co, and deposition density of 185W, 54Mn, 7Be, and 60Co present at 1-year with mortality for cancers such as female connective and soft tissue sarcoma, male and female thymus,
female colon, male and female thyroid, female brain, male multiple myeloma, female breast, and uterine cancer. Significant
correlations included isotopic forms of mutagenic metals such as antimony, beryllium, cadmium, cobalt, cesium, manganese,
rhodium, selenium, tellurium, and tungsten. The large number of significant correlation tests beyond expectation warrants
deeper questions related to the toxicology of fission products and induced radionuclides, validity of kriging procedures,
and new studies on core sampling of watersheds and trees in regions assumed to receive the greatest levels of environmental
radiocontamination.
The text was submitted by the authors in English. 相似文献
769.
Charles G. Hanlon R. L. Miller B. F. McPherson 《Journal of the American Water Resources Association》1998,34(4):951-961
ABSTRACT: Relationships between wind velocity and the vertical light attenuation coefficient (K0) were determined at two locations in a large, shallow lake (Lake Okeechobee, Florida, USA). K0 was significantly correlated with antecedent wind conditions, which explained as much as 90 percent of the daily variation in K0. Sub-surface irradiance began to change within 60 to 90 minutes of the time when wind velocity exceeded or dropped below a threshold value. Maximum one hour changes in K0 were > 50 percent, however, 20 to 30 percent changes were more common. The magnitude of change in K0 varied spatially based on differences in sediment type. K0 never exceeded 2.8 at a location where bottom sediments were dominated by a mixture of coarse sand and shells. In comparison, K0 exceeded 9 during episodic wind events where the bottom sediment was comprised of fine grain mud. Underwater irradiance data can be used to determine threshold wind velocity and account for the influence sediment type has on K0. Once a threshold velocity has been established, the frequency, rate, and duration of expected change in underwater irradiance can be evaluated. This is critical information for scientists who are studying algal productivity or other light-related phenomena. 相似文献
770.