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81.
Edgar PJ Hursthouse AS Matthews JE Davies IM Hillier S 《Journal of environmental monitoring : JEM》2006,8(9):887-896
An intertidal site in the Clyde Estuary, UK, was selected to evaluate the role of sediment geochemistry on the bioaccumulation of polychlorinated biphenyls (PCBs) by mussels (Mytilus edulis). The area had previously been identified as showing anomalously high levels of PCB contamination (over 1,500 microg kg(-1) total PCB in sediment, 22 congeners). Samples of surface sediment and M. edulis were collected from two closely located sites, one within the anomalous area and another representing typical PCB contamination in the estuary. Sediment samples were separated into grain size fractions and analysed for a range of biomarker compounds, PCBs and sediment mineralogy. The anomalous site showed an atypical association of PCBs with sediment properties, despite both locations showing influence of both petrogenic and pyrogenic organic contamination. Interrogation of data using correlation and principal component analysis showed that sediment mineralogy as well as organic matter composition influenced PCB congener distribution. One sediment source was found to control the PCB concentration in mussels at both locations and clay mineralogy appears to control PCB uptake by biota with preference for higher molecular weight congeners. Overall bioavailability is determined by sediment TOC. 相似文献
82.
Christy L. Hoffman Angelina V. Ruiz-Lambides Edgar Davila Elizabeth Maldonado Melissa S. Gerald Dario Maestripieri 《Behavioral ecology and sociobiology》2008,62(11):1711-1718
In sexually promiscuous mammals, female reproductive effort is mainly expressed through gestation, lactation, and maternal
care, whereas male reproductive effort is mainly manifested as mating effort. In this study, we investigated whether reproduction
has significant survival costs for a seasonally breeding, sexually promiscuous species, the rhesus macaque, and whether these
costs occur at different times of the year for females and males, namely in the birth and the mating season, respectively.
The study was conducted with the rhesus macaque population on Cayo Santiago, Puerto Rico. Data on 7,402 births and 922 deaths
over a 45-year period were analyzed. Births were concentrated between November and April, while conceptions occurred between
May and October. As predicted, female mortality probability peaked in the birth season whereas male mortality probability
peaked in the mating season. Furthermore, as the onset of the birth season gradually shifted over the years in relation to
climatic changes, there was a concomitant shift in the seasonal peaks of male and female mortality. Taken together, our findings
provide the first evidence of sex differences in the survival costs of reproduction in nonhuman primates and suggest that
reproduction has significant fitness costs even in environments with abundant food and absence of predation. 相似文献
83.
Daniel Bienstock Robert L. Amsler Edgar R. Bauer Jr. 《Journal of the Air & Waste Management Association (1995)》2013,63(8):442-445
Nitrogen oxides are a potential atmospheric pollutant. Their formation and decomposition were studied in an experimental pulverized-coal-fired furnace. The concentration of nitrogen oxides (NOx) was a maximum in the combustion zone and decreased as the combustion gas cooled. At a coal burning rate of 2 Ib/hr and 22% excess air, reduction of nitrogen oxides was obtained by selective secondary-air distribution. With 105% cf the stoichiometric air fed to the coal-combustion zone and 17% additional air fed just beyond the flame front, 62% reduction of NOx occurred with good combustion efficiency. Lowering the quantity of excess air lowered the NOx concentration, but at the expense of combustion efficiency. When 22% excess air was fed to the primary combustion zone, NOx concentration in the effluent was 550 ppm and carbon in the fly ash 2.0%. With 5% excess air, the NOx concentration fell to 210 ppm and carbon in the fly ash rose to 13.8%. With stoichiometric combustion the NOx was 105 ppm a reduction of 81 %, and the carbon was 42.3%. Recirculation of combustion gas was not an effective means of lowering NOx formation. 相似文献
84.
The objective of this paper is to analyse the effect of mining on economic and social development in the region of Antofagasta from 1985 to 2008. Analysis of development is restricted to spheres described by available indicators used by several international and non-governmental organizations such as income distribution, education, health, poverty, human development and security, satisfaction, cost of living, income per capita, GDP per capita, employment, productive activity, added value and its distribution. Correlation between some of these variables is estimated as well as the gap between these indicators and those of developed countries. 相似文献
85.
Neubauer CP Hall GB Lowe EF Robison CP Hupalo RB Keenan LW 《Environmental management》2008,42(6):1101-1114
The St. Johns River Water Management District (SJRWMD) has developed a minimum flows and levels (MFLs) method that has been
applied to rivers, lakes, wetlands, and springs. The method is primarily focused on ecological protection to ensure systems
meet or exceed minimum eco-hydrologic requirements. MFLs are not calculated from past hydrology. Information from elevation
transects is typically used to determine MFLs. Multiple MFLs define a minimum hydrologic regime to ensure that high, intermediate,
and low hydrologic conditions are protected. MFLs are often expressed as statistics of long-term hydrology incorporating magnitude
(flow and/or level), duration (days), and return interval (years). Timing and rates of change, the two other critical hydrologic
components, should be sufficiently natural. The method is an event-based, non-equilibrium approach. The method is used in
a regulatory water management framework to ensure that surface and groundwater withdrawals do not cause significant harm to
the water resources and ecology of the above referenced system types. MFLs are implemented with hydrologic water budget models
that simulate long-term system hydrology. The method enables a priori hydrologic assessments that include the cumulative effects
of water withdrawals. Additionally, the method can be used to evaluate management options for systems that may be over-allocated
or for eco-hydrologic restoration projects. The method can be used outside of the SJRWMD. However, the goals, criteria, and
indicators of protection used to establish MFLs are system-dependent. Development of regionally important criteria and indicators
of protection may be required prior to use elsewhere. 相似文献
86.
Christian Solli Rahul Anantharaman Anders H. Strømman Xiangping Zhang Edgar G. Hertwich 《International Journal of Greenhouse Gas Control》2009,3(2):152-160
This study presents a comparison of different concepts for delivering combined heat and power (CHP) to a refinery in Norway. A reference case of producing high pressure steam from natural gas in boilers and electricity in a combined cycle power plant, is compared to a: (1) natural gas fueled CHP without any CO2 capture; (2) hydrogen fueled CHP with hydrogen produced from steam methane reforming (SMR); (3) hydrogen fueled CHP with hydrogen produced from autothermal reforming (ATR); and finally (4) natural gas fueled CHP with postcombustion CO2 removal. The options are compared on the basis of first law efficiency, emissions of CO2 and a simplified cash flow evaluation. Results show that in terms of efficiency the standard natural gas fueled CHP performs better than the reference case as well as the options with carbon capture. The low carbon options in turn offer lower emissions of greenhouse gases while maintaining the same efficiency as the reference case. The cash flow analysis shows that for any option, a certain mix of prices is required to produce a positive cash flow. As expected, the relationship between natural gas price and electricity price affects all options. Also the value of heat and CO2 emissions plays an important role. 相似文献
87.
Edgar Hiller Slavomír Čerňanský Zoltán Krascsenits Ján Milička 《Environmental science and pollution research international》2009,16(5):546-554
Background, aim, and scope Herbicide fate and its transport in soils and sediments greatly depend upon sorption–desorption processes. Quantitative determination
of herbicide sorption–desorption is therefore essential for both the understanding of transport and the sorption equilibrium
in the soil/sediment–water system; and it is also an important parameter for predicting herbicide fate using mathematical
simulation models. The total soil/sediment organic carbon content and its qualitative characteristics are the most important
factors affecting sorption–desorption of herbicides in soil or sediment. Since the acetochlor is one of the most frequently
used herbicides in Slovakia to control annual grasses and certain annual broad-leaved weeds in maize and potatoes, and posses
various negative health effects on human beings, our aim in this study was to investigate acetochlor sorption and desorption
in various soil/sediment samples from Slovakia. The main soil/sediment characteristics governing acetochlor sorption–desorption
were also identified.
Materials and methods The sorption–desorption of acetochlor, using the batch equilibration method, was studied on eight surface soils, one subsurface
soil and five sediments collected from the Laborec River and three water reservoirs. Soils and sediments were characterized
by commonly used methods for their total organic carbon content, distribution of humus components, pH, grain-size distribution,
and smectite content, and for calcium carbonate content. The effect of soil/sediment characteristics on acetochlor sorption–desorption
was examined by simple correlation analysis.
Results Sorption of acetochlor was expressed as the distribution coefficient (K
d). K
d values slightly decreased as the initial acetochlor concentration increased. These values indicated that acetochlor was moderately
sorbed by soils and sediments. Highly significant correlations between the K
d values and the organic carbon content were observed at both initial concentrations. However, sorption of acetochlor was most
closely correlated to the humic acid carbon, and less to the fulvic acid carbon. The total organic carbon content was found
to also significantly influence acetochlor desorption.
Discussion Since the strong linear relationship between the K
d values of acetochlor and the organic carbon content was already released, the corresponding K
oc values were calculated. Considerable variation in the K
oc values suggested that other soil/sediment parameters besides the total soil organic carbon content could be involved in acetochlor
sorption. This was revealed by a significant correlation between the K
oc values and the ratio of humic acid carbon to fulvic acid carbon (CHA/CFA).
Conclusions When comparing acetochlor sorption in a range of soils and sediments, different K
d values which are strongly correlated to the total organic carbon content were found. Concerning the humus fractions, the
humic acid carbon content was strongly correlated to the K
d values, and it is therefore a better predictor of the acetochlor sorption than the total organic carbon content. Variation
in the K
oc values was attributed to the differences in distribution of humus components between soils and sediments. Desorption of acetochlor
was significantly influenced by total organic carbon content, with a greater organic carbon content reducing desorption.
Recommendations and perspectives This study examined the sorption–desorption processes of acetochlor in soils and sediments. The obtained sorption data are
important for qualitative assessment of acetochlor mobility in natural solids, but further studies must be carried out to
understand its environmental fate and transport more thoroughly. Although, the total organic carbon content, the humus fractions
of the organic matter and the CHA/CFA ratio were sufficient predictors of the acetochlor sorption–desorption. Further investigations of the structural and chemical
characteristics of humic substances derived from different origins are necessary to more preciously explain differences in
acetochlor sorption in the soils and sediments observed in this study. 相似文献
88.
Edgar R. Stephens Frank R. Burleson 《Journal of the Air & Waste Management Association (1995)》2013,63(12):929-936
The diversity of hydrocarbons which are present in ambient polluted air provide a potentially rich source of information concerning the nature of this type of pollution. Measurements of the relative amounts of various hydrocarbons can be correlated with the various possible sources. Since hydrocarbon reactivities vary widely it is also possible to estimate the extent to which various individual hydrocarbons have reacted. Except for samples taken deliberately near sources of hydrocarbon pollution these air samples invariably resemble auto exhaust with an addition of natural gas and of C3–C5 paraffins which resemble gasoline vapor. Samples taken in industrial areas and near the smoke plume from a brush fire showed distinctive differences in composition. During the smog season in the fall of 1968 good data were obtained of “typical” or “representative” samples of light, medium and heavy smog. These show the expected depletion of more reactive hydrocarbons in a much more convincing way than before. By comparing these distributions with composition in unreacted samples and by making use of data from bottle irradiations, it was possible to estimate the contribution of the various hydrocarbons in terms of “amount reacted.” The amounts of higher hydrocarbons present and reacted were also estimated from gasoline composition. 相似文献
89.
John F. Sacco Edgar C. Leduc 《Journal of the Air & Waste Management Association (1995)》2013,63(6):416-419
Air pollution control, a significant problem facing state governments, receives a varying amount of fiscal resources in each state. The purpose of this paper is to examine social, economic, and political factors that may be related to state air pollution control expenditures. The indicators of the social-economic factors are urbanization, industrial pollution potential, income, and industrialization. The indicators of the political system are interparty competition, malapportionment, voter participation, local control effort, and general state expenditure efforts. The findings show that the few states expending for air pollution control in 1963 were, for the most part, characterized by a high level of economic development. In 1967, states at all levels of economic development allocated revenues for air pollution, although the more developed continued to hold an edge. In neither year did the political variables differentiate between levels of expenditure. The reasons advanced for the expenditure behavior in 1963 are the historical predominance of local control and the structural limitations of state governments. The wider, and increased, expenditures in 1967 are assessed to be the result of federal grants, the vigorous effort put forth by state control officials, and the increased public concern for the problem. 相似文献
90.
Norman E. Hester Edgar R. Stephens O. Clifton Taylor 《Journal of the Air & Waste Management Association (1995)》2013,63(6):591-595
Ambient air concentrations of fluorocarbon 11 (fluorotrichloromethane) and fluoro-carbon 12 (dichlorodifluoromethane) have been measured using a gas chro-matograph equipped with a pulsed, electron capture detector. Air samples taken on a moderately smoggy day in July 1970, at several locations near Los Angeles gave average readings of fluorocarbon 12, 0.7 ppb and fluorocarbon 11, 0.56 ppb. These readings were contrasted with those taken in early February 1973 when the air was clear and marked with turbulence due to several seasonal rain storms. The readings of both fluorocarbon 1 1 and 12 averaged about 25% less during clear weather than those taken during moderate smog. The effects of weather conditions on the concentration were also dramatically pointed out by the February samples, in that as much as a tenfold change in concentrations of both fluorocarbons from location to location and from day to day at the same location was observed. A concentration versus altitude study clearly revealed that fluorocarbons are trapped by an inversion layer. Examination of air samples taken in the vicinity of factories known to be users of fairly large quantities of fluorocarbons revealed in part how large users contribute to the atmospheric concentrations of fluorocarbons. A comparison of fluorocarbon levels in homes and public buildings with ambient outside air levels revealed that the concentrations in some homes and buildings may be as much as several thousand times as high as levels in outside air. Inside the homes and public buildings, levels were as high as one-half of a part per million. Long term photolysis studies in simulated sunlight of both fluorocarbons 11 and 12 in ambient air samples and in air samples with 1 ppm of hydrocarbon and 1 ppm of nitrogen oxides revealed that the two fluorocarbons are photochemically stable even when photolyzed for several weeks. 相似文献