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131.
Kristi A. Gebhart Derek E. Day Anthony J. Prenni Bret A. Schichtel J.L. Hand Ashley R. Evanoski-Cole 《Journal of the Air & Waste Management Association (1995)》2018,68(5):477-493
Oil and gas activities have occurred in the Bakken region of North Dakota and nearby states and provinces since the 1950s but began increasing rapidly around 2008 due to new extraction methods. Three receptor-based techniques were used to examine the potential impacts of oil and gas extraction activities on airborne particulate concentrations in Class I areas in and around the Bakken. This work was based on long-term measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network. Spatial and temporal patterns in measured concentrations were examined before and after 2008 to better characterize the influence of these activities. A multisite back-trajectory analysis and a receptor-based source apportionment model were used to estimate impacts. Findings suggest that recent Bakken oil and gas activities have led to an increase in regional fine (PM2.5—particles with aerodynamic diameters <2.5 µm) soil and elemental carbon (EC) concentrations, as well as coarse mass (CM = PM10–PM2.5). Influences on sulfate and nitrate concentrations were harder to discern due to the concurrent decline in regional emissions of precursors to these species from coal-fired electric generating stations. Impacts were largest at sites in North Dakota and Montana that are closest to the most recent drilling activity.
Implications: The increase in oil and gas activities in the Bakken region of North Dakota and surrounding areas has had a discernible impact on airborne particulate concentrations that impact visibility at protected sites in the region. However, the impact has been at least partially offset by a concurrent reduction in emissions from coal-fired electric generating stations. Continuing the recent reductions in flaring would likely be beneficial for the regional visual air quality. 相似文献
132.
The purpose of this study was to determine the hexavalent chromium (CrVI) biosorption capacities of several agricultural wastes from aqueous solutions. Samples were tested unaltered and after hydrochloric acid (HCl) treatment. Additional parameters tested include sample dose, contact time, particle size, mixing temperature, and the concentrations and pH of the CrVI solutions. Desorption studies were performed to determine if the removed CrVI could be recovered. In addition, tests were conducted to determine if the agricultural waste samples (AWS) could be reused for additional CrVI biosorption cycles. The results of this study demonstrate a wide range of CrVI biosorption proficiencies ranging from 13 to 98 percent removal. The parameters that resulted in higher CrVI removal include HCl treatment, higher sample dose, lower CrVI solution concentration, and lower mixing temperature. Desorption results showed an 8 to 25 percent CrVI recovery rate. Reused AWS were effective at removing CrVI during subsequent trials. Therefore, all AWS can be reused for additional CrVI biosorption cycles. Hence, these could reduce hazardous waste disposal inefficiencies and costs by avoiding disposing of spent AWS following each CrVI biosorption cycle. 相似文献
133.
McKinley AC Miskiewicz A Taylor MD Johnston EL 《Environmental pollution (Barking, Essex : 1987)》2011,159(6):1499-1509
Changes to larval fish assemblages may have far reaching ecological impacts. Correlations between habitat modification, contamination and marine larval fish communities have rarely been assessed in situ. We investigated links between the large-scale distribution of stressors and larval fish assemblages in estuarine environments. Larval fish communities were sampled using a benthic sled within the inner and outer zones of three heavily modified and three relatively unmodified estuaries. Larval abundances were significantly greater in modified estuaries, and there were trends towards greater diversity in these systems. Differences in larval community composition were strongly related to sediment metal levels and reduced seagrass cover. The differences observed were driven by two abundant species, Paedogobius kimurai and Ambassis jacksoniensis, which occurred in large numbers almost exclusively in highly contaminated and pristine locations respectively. These findings suggest that contamination and habitat alteration manifest in substantial differences in the composition of estuarine larval fish assemblages. 相似文献
134.
Laundering fabrics with chlorine bleach plays a role in health and hygiene as well as aesthetics. However, laundry bleaching may create chlorinated by-products with potentially adverse human health effects. Studies have shown that toxic chlorinated gases are produced in the headspace of washing machines when hypochlorite-containing bleach is used. Laundry bleaching has also been implicated in contributing dissolved organochlorine to municipal wastewater. However, there have been no reports of organochlorines produced and retained in fabric as a result of laundry bleaching. We have used a chlorine-specific X-ray spectroscopic analysis to demonstrate the formation of organochlorine by-products in cotton fabrics laundered with chlorine bleach under typical household conditions. Organochlorine formation increases at higher wash temperature. At least two pools of organochlorine are produced in bleached fabric: a labile fraction that diminishes over several months of storage time as well as a more stable fraction that persists after more than 1 year. Our results also suggest that residual hypochlorite remains in fabric after laundering with bleach, presenting the possibility of direct and sustained dermal contact with reactive chlorine. This study provides a first step toward identifying a new risk factor for elevated organochlorine body burdens in humans. 相似文献
135.
Ton Snelder Anthony Lehmann Nicolas Lamouroux John Leathwick Karin Allenbach 《Environmental management》2009,44(4):658-670
Numerical clustering has frequently been used to define hierarchically organized ecological regionalizations, but there has
been little robust evaluation of their performance (i.e., the degree to which regions discriminate areas with similar ecological
character). In this study we investigated the effect of the weighting and treatment of input variables on the performance
of regionalizations defined by agglomerative clustering across a range of hierarchical levels. For this purpose, we developed
three ecological regionalizations of Switzerland of increasing complexity using agglomerative clustering. Environmental data
for our analysis were drawn from a 400 m grid and consisted of estimates of 11 environmental variables for each grid cell
describing climate, topography and lithology. Regionalization 1 was defined from the environmental variables which were given
equal weights. We used the same variables in Regionalization 2 but weighted and transformed them on the basis of a dissimilarity
model that was fitted to land cover composition data derived for a random sample of cells from interpretation of aerial photographs.
Regionalization 3 was a further two-stage development of Regionalization 2 where specific classifications, also weighted and
transformed using dissimilarity models, were applied to 25 small scale “sub-domains” defined by Regionalization 2. Performance
was assessed in terms of the discrimination of land cover composition for an independent set of sites using classification
strength (CS), which measured the similarity of land cover composition within classes and the dissimilarity between classes.
Regionalization 2 performed significantly better than Regionalization 1, but the largest gains in performance, compared to
Regionalization 1, occurred at coarse hierarchical levels (i.e., CS did not increase significantly beyond the 25-region level).
Regionalization 3 performed better than Regionalization 2 beyond the 25-region level and CS values continued to increase to
the 95-region level. The results show that the performance of regionalizations defined by agglomerative clustering are sensitive
to variable weighting and transformation. We conclude that large gains in performance can be achieved by training classifications
using dissimilarity models. However, these gains are restricted to a narrow range of hierarchical levels because agglomerative
clustering is unable to represent the variation in importance of variables at different spatial scales. We suggest that further
advances in the numerical definition of hierarchically organized ecological regionalizations will be possible with techniques
developed in the field of statistical modeling of the distribution of community composition. 相似文献
136.
Male seahorses (genus Hippocampus) provide all post-fertilization parental care, yet despite high levels of paternal investment, these species have long been
thought to have conventional sex roles, with female mate choice and male–male competition. Recent studies of the pot-bellied
seahorse (Hippocampus abdominalis) have shown that sex-role reversal occurs in high-density female-biased populations, indicating that male mating preferences
may lead to sexual selection on females in this species. Egg size, egg number, and offspring size all correlate positively
with female body size in Hippocampus, and by choosing large mating partners, male seahorses may increase their reproductive success. While male brood size is
also positively correlated with body size, small H. abdominalis males can carry exceptionally large broods, suggesting that the fecundity benefits of female preference for large partners
may be limited. We investigated the importance of body size in reproductive decisions of H. abdominalis, presenting focal individuals of both sexes with potential mating partners of different sizes. Mating preferences were quantified
in terms of time spent courting each potential partner. Male seahorses were highly active throughout the mate-choice trials
and showed a clear behavioral preference for large partners, while females showed significantly lower levels of activity and
equivocal mating preferences. The strong male preferences for large females demonstrated here suggest that sexual selection
may act strongly on female body size in wild populations of H. abdominalis, consistent with predictions on the importance of female body size for reproductive output in this species.
An erratum to this article can be found at 相似文献
137.
138.
Total annual nutrient loads are a function of both watershed characteristics and the magnitude of nutrient mobilizing events.
We investigated linkages among land cover, discharge and total phosphorus (TP) concentrations, and loads in 25 Kansas streams.
Stream monitoring locations were selected from the Kansas Department of Health and Environment stream chemistry long-term
monitoring network sites at or near U.S. Geological Survey stream gauges. We linked each sample with concurrent discharge
data to improve our ability to estimate TP concentrations and loads across the full range of possible flow conditions. Median
TP concentration was strongly linked (R
2 = 76%) to the presence of cropland in the riparian zones of the mostly perennial streams. At baseflow, discharge data did
not improve prediction of TP, but at high flows discharge was strongly linked to concentration (a threshold response occurred).
Our data suggest that on average 88% of the total load occurred during the 10% of the time with the greatest discharge. Modeled
reductions in peak discharges, representing increased hydrologic retention, predicted greater decreases in total annual loads
than reductions of ambient concentrations because high discharge and elevated phosphorus concentrations had multiplicative
effects. No measure of land use provided significant predictive power for concentrations when discharge was elevated or for
concentration rise rates under increasing discharge. These results suggest that reductions of baseflow concentrations of TP
in streams without wastewater dischargers may be managed by reductions of cropland uses in the riparian corridor. Additional
measures may be needed to manage TP annual loads, due to the large percentage of the TP load occurring during a few high-flow
events each year. 相似文献
139.
140.
Planetary Stewardship in an Urbanizing World: Beyond City Limits 总被引:1,自引:0,他引:1
Sybil P. Seitzinger Uno Svedin Carole L. Crumley Will Steffen Saiful Arif Abdullah Christine Alfsen Wendy J. Broadgate Frank Biermann Ninad R. Bondre John A. Dearing Lisa Deutsch Shobhakar Dhakal Thomas Elmqvist Neda Farahbakhshazad Owen Gaffney Helmut Haberl Sandra Lavorel Cheikh Mbow Anthony J. McMichael Joao M. F. deMorais Per Olsson Patricia Fernanda Pinho Karen C. Seto Paul Sinclair Mark Stafford Smith Lorraine Sugar 《Ambio》2012,41(8):787-794
Cities are rapidly increasing in importance as a major factor shaping the Earth system, and therefore, must take corresponding responsibility. With currently over half the world’s population, cities are supported by resources originating from primarily rural regions often located around the world far distant from the urban loci of use. The sustainability of a city can no longer be considered in isolation from the sustainability of human and natural resources it uses from proximal or distant regions, or the combined resource use and impacts of cities globally. The world’s multiple and complex environmental and social challenges require interconnected solutions and coordinated governance approaches to planetary stewardship. We suggest that a key component of planetary stewardship is a global system of cities that develop sustainable processes and policies in concert with its non-urban areas. The potential for cities to cooperate as a system and with rural connectivity could increase their capacity to effect change and foster stewardship at the planetary scale and also increase their resource security. 相似文献