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111.
Rick D. Saylor Eric S. Edgerton Benjamin E. Hartsell Karsten Baumann D. Alan Hansen 《Atmospheric environment (Oxford, England : 1994)》2010,44(38):4994-5004
Continuous ammonia (NH3) measurements with a temporal resolution of 5 min were implemented at selected SEARCH sites in the southeastern U. S. during 2007. The SEARCH continuous NH3 instrument uses a citric acid denuder difference technique employing a dual-channel nitric oxide-ozone chemiluminescence analyzer. Data from two SEARCH sites are presented, Jefferson Street, Atlanta (JST) (urban), and Yorkville, Georgia (YRK) (rural), for the period July–December, 2007. Highest NHx (total ammonia = gaseous NH3 + PM2.5 NH4+) values were observed in August and September at both JST and YRK. Highest NH3 values occurred in August and September at JST, but in August through October at YRK. Lowest NH3 and NHx values occurred in December at both sites. YRK is significantly impacted by nearby poultry sources, routinely experiencing hourly average NH3 mixing ratios above 20 ppbv. Wind sector analysis clearly implicates the nearby poultry operations as the source of the high NH3 values. Weekday versus weekend differences in composite hourly mean diurnal profiles of NH3 at JST indicate that mobile sources have a measurable but relatively small impact on NH3 observed at that site, and little or no impact on NH3 observed at YRK. A distinctive composite mean hourly diurnal variation was observed at both JST and YRK, exhibiting maxima in the morning and evening with a broad minimum during midday. Analysis of observed NH3 diurnal variations from the literature suggests a hypothesized mechanism for the observed behavior based on interaction of local emissions and dry deposition with the formation and collapse of the dynamically mixed atmospheric boundary layer during the day and shallow nocturnal layer at night. Simple mixed layer concentration box model simulations confirm the plausibility of the suggested mechanism. 相似文献
112.
David W. Neumann Edith A. Zagona Balaji Rajagopalan 《Journal of the American Water Resources Association》2006,42(5):1275-1284
ABSTRACT: Warm summer stream temperatures due to low flows and high air temperatures are a critical water quality problem in many western United States river basins because they impact threatened fish species’habitat. One way to alleviate this problem is for local and federal organizations to purchase water rights to be used to increase flows, hence decrease temperatures. Presented is a Decision Support System (DSS) that can be used in an operations mode to effectively use water acquired to mitigate warm stream temperatures. The DSS uses a statistical model for predicting daily stream temperatures and a rule‐based module to compute reservoir releases. Water releases are calculated to meet fish habitat temperature targets based on the predicted stream temperature and a user specified confidence of the temperature predictions. Strategies that enable effective use of a limited amount of water throughout the season have also been incorporated in the DSS. The utility of the DSS is demonstrated by an example application to the Truckee River near Reno, Nevada, using hypothetical operating policy and 1988 through 1994 inflows. Results indicate that the DSS could substantially reduce the number of target temperature violations (i.e., stream temperatures exceeding the target temperature levels detrimental to fish habitat). 相似文献
113.
Dorte Krause-Jensen Anne Lise Middelboe Jacob Carstensen Karsten Dahl 《Marine Biology》2007,152(1):25-36
Based on a large monitoring data set from Danish coastal waters we tested the hypotheses: (1) The vertical pattern of algal
abundance is regulated by exposure in shallow water and by light limitation towards deeper water, resulting in a bell-shaped
abundance curve, with peak abundance located deeper at more exposed sites, (2) in deeper water, total algal abundance and
abundance of perennial algae decrease along a eutrophication gradient while (3) abundance and relative abundance of opportunists
increase. The vertical pattern of algal abundance showed a peak at intermediate water depths which was located deeper in more
exposed areas and thus confirmed our first hypothesis. For algae growing from depths of peak abundance and deeper, the study
demonstrated that total algal abundance and abundance of perennials and opportunists at given depths decreased significantly
along a eutrophication gradient and the relationships had high explanatory power (R
2 = 0.53–0.73). These results confirmed our second hypothesis. By contrast, the relative abundance of opportunists responded solely
to salinity and was largest in the most brackish areas, in contradiction to hypothesis three. The lack of coupling between
eutrophication and relative abundance of opportunists arises because both opportunists and the entire algal community were
light limited and their ratio therefore relatively insensitive to changing water clarity. The analyses indicated that algal
abundance initially responded slowly to increasing eutrophication but showed a more marked response at TN concentrations of
35–40 μM. However, the existence of possible threshold nutrient levels demands further analyses. 相似文献
114.
A. Kranzmann T. Neddemeyer A.S. Ruhl D. Huenert D. Bettge G. Oder R. Saliwan Neumann 《International Journal of Greenhouse Gas Control》2011
Basic research on the corrosive effect of flue gases has been performed at the BAM Federal Institute for Materials Research and Testing (Germany). Conditions at both high and low temperatures were simulated in specially designed experiments. Carburization occured in flue gases with high CO2 content and temperatures higher than 500 °C. In SO2 containing flue gases sulphur was detected in the oxide scale. At lower temperatures no corrosion was observed when gases with low humidity were investigated. Humidity higher than 1500 ppm was corrosive and all steels with Cr contents lower than 12% revealed corroded surfaces. At low temperatures below 10 °C a mixture of sulphuric and nitric acid condensed on metal surfaces. Acid condensation caused severe corrosion. Humidity, CO2, O2, and SO2 contents are the important factors determining corrosion. Below 300 °C acid condensation is the primary reason for corrosion. Low humidity and low temperatures are conditions which can be expected in the CO2 separation and treatment process. This work includes major conditions of the flue gas and CO2 stream in CCS plants and CCS technology. 相似文献
115.
116.
Butyltin was measured in tissue, water and sediment samples collected throughout Coos Bay estuary between 1986 and 1997. Butyltin-induced shell deformation in commercial oysters prompted this assessment. Butyltins are released from tributyltin oxide (TBTO)-containing boat paint. Clams from three sites contained tributyltin (TBT) levels ranging from 168 to 457 microg/kg in 1992-1994. Consequently, Oregon Health Division (OHD) issued a shellfish consumption advisory in 1995; it was rescinded in 1997 after US Environmental Protection Agency (EPA) revised the TBTO oral reference dose (RfD). The revised RfD changed the tissue screening level from 112 to 1120 microg TBT/kg. Fifty percent of sediment samples collected during 1991-1997 and analyzed for total butyltins (TotBT) exceeded the Puget Sound Dredge Disposal Analysis Screening Level (PSDDA SL) of 73 microg TBT/kg dw. TotBT at three shipyards selected for site assessment by EPA ranged from 24 to 68,613 microg/kg dw. Sediment and tissue butyltins have been decreasing in all but one area of the estuary. 相似文献
117.
The intertidal midge Clunio, which reproduces on exposed rocky seashores, becomes enclosed in an irregularly shaped air bubble during short submersion
by incoming waves. This water-repellent property of Clunio’s cuticle is caused by a complete cover of hydrophobic microtrichia offering an effective surf tolerance. These microtrichia
not only trap a thin air layer above the cuticle but also maintain a larger air bubble between the insect’s ventral side and
legs. The effectiveness of the water repellence was quantitatively characterised on the basis of a known model (Crisp and
Thorpe, Discuss Faraday Soc 3:210–220, 1948). The parameters of the model are the contact angle θ (>90°) at the contact line of air/water/microtrichia and the distance between individual microtrichia and their radius. When
the microtrichia are 1.1 μm apart and have a radius of 0.1 μm and an estimated contact angle θ of 140°, the air layer is stable against hydrostatic pressures of up to 3 m water column. As shown by a modified version
of the model, considerably larger air bubbles can be trapped by the microtrichia cover of the legs up to distances of 0.5 mm
from the body. The widely spaced (about 8 μm apart) and longer setae of Clunio are not involved in the formation of air layers and air bubble. 相似文献
118.
Linked river basin and coastal water models were applied to analyse the effects of an optimal nitrogen management scenario
in the Oder/Odra river basin on water quality in the Oder (Szczecin) Lagoon and the Pomeranian Bay (Baltic Sea). This scenario
would reduce nitrogen loads into the coastal waters by about 35%, a level which is similar to the load of the late 1960’s.
During summer the primary production and algae biomass in the Oder estuary is limited by nitrogen, which makes a nitrogen
management reasonable. The comparison of the late 1960’s and the mid 1990’s shows that an optimal nitrogen management has
positive effects on coastal water quality and algae biomass. However, this realistic nitrogen reduction scenario would not
ensure a good coastal water quality according to the European Water Framework Directive. A good water quality in the river
will not be sufficient to ensure a good water quality in the lagoon. Nitrogen load reductions bear the risk of increased potentially
toxic, blue-green algae blooms, especially in the Baltic coastal sea. However, to reach water quality improvements in lagoons
and inner coastal waters, nitrogen cuts are necessary. A mere focus on phosphorus is not sufficient. 相似文献
119.
Lasse Marohn Enno Prigge Karsten Zumholz Andreas Klügel Heike Anders Reinhold Hanel 《Marine Biology》2009,156(5):927-933
Otolith microchemistry is widely used as a tool to track individual migration pathways of diadromous fish under the assumption
that the elemental composition of fish otoliths is directly influenced by the physicochemical properties of the surrounding
water. Nevertheless, several endogenous factors are reported to affect element incorporation into fish otoliths and might
lead to misinterpretations of migration studies. This study experimentally examined the influence of eight different diets
on the microchemical composition of European eel (Anguilla anguilla) otoliths using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Seven natural prey types and one
artificial diet were fed during 8 weeks in freshwater circuits. Results show for the first time that food has no significant
influence on the incorporation of Na, Sr, Ba, Mg, Mn, Cu and Y into European eel otoliths. This indicates that the incorporation
of elements usually chosen for migration studies is not affected by diet and that individual feeding behaviour of A. anguilla will not lead to any misinterpretation of migration pathways. 相似文献
120.