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991.
Inundation influences on bioavailability of phosphorus in managed wetland sediments in agricultural landscapes 总被引:1,自引:0,他引:1
Kröger R Lizotte RE Douglas Shields F Usborne E 《Journal of environmental quality》2012,41(2):604-614
Agricultural runoff carries high nutrient loads to receiving waters, contributing to eutrophication. Managed wetlands can be used in integrated management efforts to intercept nutrients before they enter downstream aquatic systems, but detailed information regarding sorption and desorption of P by wetland sediments during typical inundation cycles is lacking. This study seeks to quantify and elucidate how inundation of wetland sediments affects bioavailability of P and contributions of P to downstream systems. A managed wetland cell in Tunica County, Mississippi was subjected to a simulated agricultural runoff event and was monitored for bioavailable phosphorus (water-extractable P [P], Fe-P, and Al-P) of wetland sediments and water level during the runoff event and for 130 d afterward. Inundation varied longitudinally within the wetland, with data supporting significant temporal relationships between inundation and P desorption. Concentrations of P were significantly higher at the site that exhibited variable hydroperiods (100 m) as compared with sites under consistent inundation. This suggests that sites that are inundated for longer periods of time desorb less P immediately to the environment than sites that have periodic or ephemeral inundation. Concentrations of iron oxalate and NaOH-P were significantly higher at the least inundated site as compared with all other sites (F = 5.43; = 0.001) irrespective of time. These results support the hypothesis that increased hydraulic residence time decreases the bioavailability of P in wetland sediments receiving agricultural runoff. This finding suggests that the restoration of wetlands in the mid-southern United States may be hydrologically managed to improve P retention. 相似文献
992.
The Fine Sediment Biotic Index (FSBI) is a regional, stressor-specific biomonitoring index to assess fine sediment (<2 mm)
impacts on macroinvertebrate communities in northwestern US streams. We examined previously collected data of benthic macroinvertebrate
assemblages and substrate particle sizes for 1,139 streams spanning 16 western US Level III Ecoregions to determine macroinvertebrate
sensitivity (mostly at species level) to fine sediment. We developed FSBI for four ecoregion groupings that include nine of
the ecoregions. The grouping were: the Coast (Coast Range ecoregion) (136 streams), Northern Mountains (Cascades, N. Rockies,
ID Batholith ecoregions) (428 streams), Rockies (Middle Rockies, Southern Rockies ecoregions) (199 streams), and Basin and
Plains (Columbia Plateau, Snake River Basin, Northern Basin and Range ecoregions) (262 streams). We excluded rare taxa and
taxa identified at coarse taxonomic levels, including Chironomidae. This reduced the 685 taxa from all data sets to 206. Of
these 93 exhibited some sensitivity to fine sediment which we classified into four categories: extremely, very, moderately,
and slightly sensitive; containing 11, 22, 30, and 30 taxa, respectively. Categories were weighted and a FSBI score calculated
by summing the sensitive taxa found in a stream. There were no orders or families that were solely sensitive or resistant
to fine sediment. Although, among the three orders commonly regarded as indicators of high water quality, the Plecoptera (5),
Trichoptera (3), and Ephemeroptera (2) contained all but one of the species or species groups classified as extremely sensitive.
Index validation with an independent data set of 255 streams found FSBI scores to accurately predict both high and low levels
of measured fine sediment. 相似文献
993.
During the post-World War II era, the Mojave Desert Region of San Bernardino County, California, has experienced rapid levels
of population growth. Over the past several decades, growth has accelerated, accompanied by significant shifts in ethnic composition,
most notably from predominantly White non-Hispanic to Hispanic. This study explores the impacts of changing ethnicity on future
development and the loss of open space by modeling ethnic propensities regarding family size and settlement preferences reflected
by U.S. Census Bureau data. Demographic trends and land conversion data were obtained for seven Mojave Desert communities
for the period between 1990 and 2001. Using a spatially explicit, logistic regression-based urban growth model, these data
and trends were used to project community-specific future growth patterns from 2000 to 2020 under three future settlement
scenarios: (1) an “historic” scenario reported in earlier research that uses a Mojave-wide average settlement density of 3.76
persons/ha; (2) an “existing” scenario based on community-specific settlement densities as of 2001; and (3) a “demographic
futures” scenario based on community-specific settlement densities that explicitly model the Region’s changing ethnicity.
Results found that under the demographic futures scenario, by 2020 roughly 53% of within-community open space would remain,
under the existing scenario only 40% would remain, and under the historic scenario model the communities would have what amounts
to a deficit of open space. Differences in the loss of open space across the scenarios demonstrate the importance of considering
demographic trends that are reflective of the residential needs and preferences of projected future populations. 相似文献
994.
Dearing JA Bullock S Costanza R Dawson TP Edwards ME Poppy GM Smith GM 《Environmental management》2012,49(4):767-775
The ‘Perfect Storm’ metaphor describes a combination of events that causes a surprising or dramatic impact. It lends an evolutionary
perspective to how social-ecological interactions change. Thus, we argue that an improved understanding of how social-ecological
systems have evolved up to the present is necessary for the modelling, understanding and anticipation of current and future
social-ecological systems. Here we consider the implications of an evolutionary perspective for designing research approaches.
One desirable approach is the creation of multi-decadal records produced by integrating palaeoenvironmental, instrument and
documentary sources at multiple spatial scales. We also consider the potential for improved analytical and modelling approaches
by developing system dynamical, cellular and agent-based models, observing complex behaviour in social-ecological systems
against which to test systems dynamical theory, and drawing better lessons from history. Alongside these is the need to find
more appropriate ways to communicate complex systems, risk and uncertainty to the public and to policy-makers. 相似文献
995.
Luke D. Ziemba Jack E. Dibb Robert J. Griffin L. Gregory Huey Pieter Beckman 《Atmospheric environment (Oxford, England : 1994)》2010,44(13):1649-1657
Observations of particle size distributions suggest that particles grow significantly just above the snow surface at a remote, Arctic site. Measurements were made at Summit, Greenland (71.38°N and 31.98°W) at approximately 3200 m above sea level. No new particle formation was observed locally, but growth of ultrafine particles was identified by continuous evolution of the geometric mean diameter (GMD) during four events. The duration of the growth during events was between 24 and 115 h, and calculated event-average growth rates (GR) were 0.09, 0.30, 0.27, and 0.18 nm h?1 during each event, respectively. Four-hour GR up to 0.96 nm h?1 were observed. Events occurred during below- and above-average temperatures and were independent of wind direction. Correlation analysis of hourly-calculated GR suggested that particle growth was limited by the availability of photochemically produced precursor gases. Sulfuric acid played a very minor role in particle growth, which was likely dominated by condensation of organic compounds, the source of which was presumably the snow surface. The role of boundary layer dynamics is not definite, although some mixing at the surface is necessary for the observation of particle growth. Due to the potentially large geographic extent of events, observations described here may provide a link between long-range transport of mid-latitude pollutants and climate regulation in the remote Arctic. 相似文献
996.
997.
Christian C. Voigt Otto von Helversen Robert Michener Thomas H. Kunz 《Behavioral ecology and sociobiology》2001,50(1):31-36
Saccopteryx bilineata has a polygynous mating system in which males defend females in a harem territory. Harem defense and courtship include energetically costly flight maneuvers and hovering displays. We tested if (1) harem males have a greater field metabolic rate than non-harem males or females and if (2) the field metabolic rate of harem males is correlated with the number of females in a harem territory. We measured the energy budget in 32 S. bilineata with the doubly labeled water method and compared these estimates with behavioral observations in the daytime roost. Among adult bats, field metabolic rate varied with body mass by an exponent of approximately two. We found no significant difference in field metabolic rate or mass-specific field metabolic rate between harem and non-harem males. The mass-specific field metabolic rate of harem-males increased with harem size. The latter finding supports the hypothesis that the energy costs of courtship display and territorial defense influence the energy budget of harem males. Overall, field metabolic rates of S. bilineata were lower than those of similarly sized bats of the temperate zone and only 2.3 times above the basal metabolic rate recorded for this species. We suggest that male S. bilineata did not take advantage of their metabolic capacity because a prudent allocation of energy to activities of harem maintenance is an adaptive strategy for males in this mating system. 相似文献
998.
Sinsheimer P Grout C Namkoong A Gottlieb R 《Journal of the Air & Waste Management Association (1995)》2007,57(2):172-178
The vast majority of dry cleaners worldwide use the toxic chemical perchloroethylene (PCE), which is associated with a number of adverse health and environmental impacts. Professional wet cleaning was developed as a nontoxic alternative to PCE dry cleaning but has not been widely adopted as substitute technology. In the greater Los Angeles, CA, region, a demonstration project was set up to showcase this technology and evaluate its commercial viability by converting seven cleaners from PCE dry cleaning to professional wet cleaning. The demonstration site cleaners who switched to professional wet cleaning were able to maintain their level of service and customer base while lowering operating costs. The cleaners were able to transition to professional wet cleaning without a great degree of difficulty and expressed a high level of satisfaction with professional wet cleaning. Crucial to this success was the existence of the demonstration project, which helped to develop a supporting infrastructure for professional wet cleaning that had otherwise been lacking in the garment care industry. 相似文献
999.
Assessing depleted uranium (DU) contamination of soil, plants and earthworms at UK weapons testing sites 总被引:1,自引:0,他引:1
Oliver IW Graham MC MacKenzie AB Ellam RM Farmer JG 《Journal of environmental monitoring : JEM》2007,9(7):740-748
Depleted uranium (DU) weapons testing programmes have been conducted at two locations within the UK. An investigation was therefore carried out to assess the extent of any environmental contamination arising from these test programmes using both alpha spectrometry and mass spectrometry techniques. Uranium isotopic signatures indicative of DU contamination were observed in soil, plant and earthworm samples collected in the immediate vicinity of test firing points and targets, but contamination was found to be localised to these areas. This paper demonstrates the superiority of the (235)U : (238)U ratio over the (234)U : (238)U ratio for identifying and quantifying DU contamination in environmental samples, and also describes the respective circumstances under which alpha spectrometry or mass spectrometry may be the more appropriate analytical tool. 相似文献
1000.
A small subsurface ion mobility spectrometer (SS-IMS) was constructed and tested with several environmental contaminants to determine its potential for monitoring gaseous volatile organic compounds in the vadose zone. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were detected and separated in IMS for the first time. Detection limits as low as 1 part per billion volume-to-volume (ppb(v)) were observed. Reduced mobility (K(0)) values were reported for 11 environmental contaminants. These data demonstrated the potential of ion mobility spectrometry as a viable technology for detecting and separating environmental soil-gas contaminants in the field, which may lead to a practical and simple approach for long-term monitoring of contaminated soils. 相似文献