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51.
A supercritical fluid extraction (SFE) method was developed for the extraction of polycyclic aromatic hydrocarbons (PAHs) from fresh and fallen pine needles. Toluene-modified CO2 was used as the extracting fluid, and the extracted PAHs were analyzed by GC-MS. Using a two-stage extraction procedure, a static extraction at 180 degrees C and a dynamic extraction at 60 degrees C, and an in-cell silica gel plug plus a post-oven silica gel column, the extraction and fractionation of PAHs can be accomplished in one step. Over a seven month period, a significant variation was observed for PAHs in urban samples, while PAHs in mountain samples were at much lower levels (by a factor of approximately 8) and showed little seasonal change. Although dry fallen needles and fresh needles contained similar amounts of PAHs, in the fallen needles the lower molecular weight PAHs were partially lost while the higher molecular weight PAHs were slightly enriched. Pollution in urban areas was found to be highly localized, and buildings and trees are believed to be important factors in the restriction of atmospheric PAHs. 相似文献
52.
53.
Populations of the sand dollars Encope grandis and Mellita grantii were studied at Playa Hermosa in the northern Gulf of California, Mexico. Intertidal distribution and abundance were estimated for the two species from 1969 to 1972. They occurred in the lower intertidal (-0.4 to -1.3 m) and on into the subtidal. Density of E. grandis varied from a high of 380/m2 in the spring of 1970 to a low of 0.1/m2 in the fall of 1971. Density of M. grantii ranged from a high of 56/m2 in 1970 to a low of 0.8/m2 in 1971. Growth curves were constructed based on shifts in the modes of the size distributions, and rates of mortality were estimated from the growth parameters and size distributions. It is estimated that E. grandis would attain 95% of its maximum size (74 mm) in about 6 years with an annual mortality rate of 18%. M. grantii would reach 95% of its maximum size (38 mm) in about 5 years with an annual mortality rate of 58%. The populations of these sand dollars appear to be limited by the physical environment. 相似文献
54.
Ould-Dada Z Tucker S Webbe-Wood D Mondon K Hunt J 《Journal of environmental radioactivity》2002,59(3):273-291
This paper presents the method used by the UK Food Standards Agency (FSA) to assess the potential impact of proposed radioactive discharges from the Sellafield nuclear site on food and determine their acceptability. It explains aspects of a cautious method that has been adopted to reflect the UK government policy and uncertainties related to people's habits with regard to food production and consumption. Two types of ingestion doses are considered in this method: 'possible' and 'probable' doses. The method is specifically applied to Sellafield discharge limits and calculated possible and probable ingestion doses are presented and discussed. Estimated critical group ingestion doses are below the dose limit and constraint set for members of the public. The method may be subject to future amendments to take account of changes in government policy and the outcome of a recent Consultative Exercise on Dose Assessments carried out by FSA. Uncertainties inherent in dose assessments are discussed and quantified wherever possible. 相似文献
55.
Hasanov Fakhri J. Hunt Lester C. Mikayilov Jeyhun I. 《Environmental science and pollution research international》2021,28(31):41965-41987
Environmental Science and Pollution Research - This paper contributes to the environmental literature by (i) demonstrating that the estimated coefficients and the statistical significance of the... 相似文献
56.
Nitrification and denitrification gene abundances in swine wastewater anaerobic lagoons 总被引:2,自引:0,他引:2
Although anaerobic lagoons are used globally for livestock waste treatment, their detailed microbial cycling ofN is only beginning to become understood. Within this cycling, nitrification can be performed by organisms that produce the enzyme ammonia monooxygenase. For denitrification, the reduction of nitrite to nitric oxide can be catalyzed by two forms of nitrite reductases, and N,O can be reduced by nitrous oxide reductase encoded by the gene nosZ The objectives of this investigation were to (i) quantify the abundance of the amoA, nirK, nirS, and nosZ genes; (ii) evaluate the influence of environmental conditions on their abundances; and (iii) evaluate their abundance relative to denitrification enzyme activity (DEA). Samples were analyzed via real-time quantitative polymerase chain reaction and collected from eight typical, commercial anaerobic, swine wastewater lagoons located in the Carolinas. The four genes assayed in this study were present in all eight lagoons. Their abundances relative to total bacterial populations were 0.04% (amoA), 1.33% (nirS), 5.29% (nirK), and 0.27% (nosZ). When compared with lagoon chemical characteristics, amoA and nirK correlated with several measured variables. Neither nirS nor nosZ correlated with any measured environmental variables. Although no gene measured in this study correlated with actual or potential DEA, nosZ copy numbers did correlate with the disparity between actual and potential DEA. Phylogenetic analysis ofnosZdid not reveal any correlations to DEA rates. As with other investigations, analyses of these genes provide useful insight while revealing the underlying greater complexity of N cycling within swine waste lagoons. 相似文献
57.
Abstract Sustainability has come to play a dominant discursive role in the UK planning system, particularly relating to urban regeneration. The purpose of this paper is to evaluate the role that sustainability plays in a major regeneration programme, known as Eastside, currently underway in Birmingham, the UK. That this £6 billion redevelopment is now widely talked about by such key players as Birmingham City Council and the Regional Development Agency, Advantage West Midlands, as having a central sustainability agenda points to the growing importance of the ideal of sustainability in planning and regeneration agendas. In this paper, we investigate in detail how and why sustainability has become part of the planning discourse for Eastside and critically evaluate what impact, if any, this is having on public policy decision-making. 相似文献
58.
Meadow Restoration Increases Baseflow and Groundwater Storage in the Sierra Nevada Mountains of California
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Luke J.H. Hunt Julie Fair Maxwell Odland 《Journal of the American Water Resources Association》2018,54(5):1127-1136
In mountains of the western United States, channel incision has drawn down the water table across thousands of square kilometers of meadow floodplain. Here climate change is resulting in earlier melt and reduced snowpack and water resource managers are responding by investing in meadow restoration to increase springtime storage and summer flows. The record‐setting California drought (2012–2015) provided an opportunity to evaluate this strategy under the warmer and drier conditions expected to impact mountain water supplies. In 2012, 0.1 km2 of meadow floodplain was reconnected by filling an incised channel through Indian Valley in the central Sierra Nevada Mountains of California. Despite sustained drought conditions after restoration, summer baseflow from the meadow increased 5–12 times. Before restoration, the total summer outflow from the meadow was 5% more than the total summer inflow. After restoration, total summer outflow from the meadow was between 35% and 95% more than total summer inflow. In the worst year of the drought (2015), when inflow to the meadow ceased for at least one month, summer baseflow was at least five times greater than before restoration. Groundwater levels also rose at four out of five sites near the stream channel. Filling the incised channel and reconnecting the meadow floodplain increased water availability and streamflow, despite unprecedented drought conditions. 相似文献
59.
Alan S. Kolok Marlo K. Sellin Jeffries Lindsey Knight Daniel D. Snow Shannon L. Bartelt‐Hunt 《Journal of the American Water Resources Association》2014,50(2):266-274
Recent research has suggested that the fate of biologically active compounds (BACs) originating from point sources such as wastewater treatment plants is fundamentally different from that of similar compounds released from nonpoint sources through runoff from agricultural landscapes. Downstream from wastewater treatment plants, BACs will degrade via a variety of mechanisms; however, their concentration in the water adjacent to the point of discharge may not decrease over time, as the compounds are continually released. In contrast, in agricultural systems, BACs are episodically introduced to surface water during snowmelt and rainstorm events, and under these circumstances, may be found in water for only hours or days after a storm event. Recent research in our laboratories as well as others, has suggested that sediments play an important role in the persistence of herbicides and steroids in watersheds after nonpoint source loading events. Conceptually, the sediment serves as both a sink and a source, equilibrating with BACs during storm events then slowly releasing them back into the water over time, long after the initial pulse of chemicals has moved downstream. 相似文献
60.
C. D. Dubischar E. A. Pakhomov L. von Harbou B. P. V. Hunt U. V. Bathmann 《Marine Biology》2012,159(1):15-24
Two species of salps, Salpa thompsoni and Ihlea racovitzai, were sampled during three cruises to the Lazarev Sea, Southern Ocean, in summer (December–January) 2005/2006, Autumn (April–May)
2004 and Winter (July–August) 2006. Dry weight, carbon, nitrogen, protein, lipid and carbohydrate contents were measured to
characterize the potential value of salps as a food source for predators in the Antarctic ecosystem. Biochemical composition
measurements showed that despite having a high percentage of water (~94% of wet weight), both species had relatively high
carbon and protein contents in their remaining dry weight (DW). In particular I. racovitzai showed high carbon (up to 22% of DW) and protein (up to 32% of DW) values during all seasons sampled, compared to lower values
for S. thompsoni (carbon content only about 15% of the DW, protein content about 10% of the DW). At the same time, carbohydrates (CH) and
lipids (Lip) only accounted for a small portion of salp DW in both species (1.4% CH and 3.6% Lip for I. racovitzai; 2.1% CH and 2.9% Lip for S. thompsoni). There was little variability in the biochemical composition of either salp species between the seasons sampled. Both biochemical
composition and life cycle characteristics suggest that Antarctic salps, especially I. racovitzai, may be important prey items for both cold and warm-blooded predators in an environment where food is often very scarce. 相似文献