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91.
Patrick Louchouarn Li-Jung Kuo Terry L. Wade Michele Schantz 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5630-5636
The present study tested the extraction efficiency and quantification reproducibility of anhydrosugars in a series of NIST SRMs using two extraction protocols and isotopically-labeled (d7-levoglucosan) vs. chemically analogous (sedoheptulosan) surrogates. In both instances, levoglucosan concentrations in the different versions of the Washington, D.C. urban dust standard (SRM 1649, 1649a, 1649b, and RM 8785) were similar. The present test also showed that levoglucosan concentrations were not affected by long-term shelf storage of dry material. Variability of analyses were similar for both surrogates and averaged <5%. Surrogate recoveries were shown to average 103 ± 7% and 97 ± 7% for d7-levoglucosan and sedoheptulosan, respectively. The choice of solvent was shown to affect recoveries the most (but not variability). Levoglucosan concentrations were either seriously underestimated or overestimated with ethyl acetate extraction when d7-levoglucosan or sedoheptulosan was used as surrogate, respectively. These results point to the need to use some fraction of polar solvent (i.e. methanol) in the solvent mixture. Anhydrosugar concentrations in the urban dust from the Czech Republic (candidate SRMs 2786 and 2787) were characterized by 3- to 7-fold higher anhydrosugar concentrations than those observed in the Washington, D.C. urban dust. The internal anhydrosugar signatures (i.e. levoglucosan/mannosan ratio: L/M) confirm the predominance of biomass combustion sources in both SRM series with mixed inputs from hardwood and softwood combustion in the Washington, D.C. urban dust and a predominantly softwood source in the Prague urban dust. The uniform distribution of anhydrosugars, across the particle size distribution of both SRM series, confirms earlier studies that low temperature charred materials contribute significant inputs to atmospheric ultrafine particles with long atmospheric residence time and transport ranges. 相似文献
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Tatiana V. Komarova Michael E. Bartkow Steve Carter 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):731-736
Semipermeable membrane devices (SPMDs) were deployed in water using four different methods: a typical SPMD cage with and without a mesh cover, a bowl chamber and without any protection. In addition to routinely used performance reference compounds (PRCs), perdeuterated dibenz[a,h]anthracene was added. Due to its high sampler to water partition coefficient no measurable clearance due to diffusion was expected during the deployment period, hence any observed loss could be attributed to photodegradation. The loss of PRCs was measured and SPMD-based water concentrations determined. Results showed that a typical SPMD deployment cage covered with mesh provided the best protection from photodegradation. Samplers which had undergone the highest photodegradation underestimated PAH water concentrations by up to a factor of 5 compared to the most protected SPMDs. This study demonstrates that the potential for photodegradation needs to be addressed when samplers are deployed in water of low turbidity. 相似文献
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Andrew Simon Lauren Klimetz 《Journal of the American Water Resources Association》2008,44(5):1270-1283
Abstract: Sediment is listed as one of the leading causes of water‐quality impairments in surface waters of the United States (U.S.). A water body becomes listed by a State, Territory or Tribe if its designated use is not being attained (i.e., impaired). In many cases, the prescribed designated use is aquatic health or habitat, indicating that total maximum daily loads (TMDL) targets for sediment should be functionally related to this use. TMDL targets for sediment transport have been developed for many ecoregions over the past several years using suspended‐sediment yield as a metric. Target values were based on data from “reference” streams or reaches, defined as those exhibiting geomorphic characteristics of equilibrium. This approach has proved useful to some states developing TMDLs for suspended sediment, although one cannot conclude that if a stream exceeds the target range, the aquatic ecosystem will be adversely impacted. To address this problem, historical flow‐transport and sediment‐transport data from hundreds of sites in the Southeastern U.S. were re‐examined to develop parameters (metrics) such as frequency and duration of sediment concentrations. Sites determined as geomorphically stable from field evaluations and from analysis of gauging‐station records were sorted by ecoregion. Mean‐daily flow data obtained from the U.S. Geological Survey were applied to sediment‐transport rating relations to determine suspended‐sediment load for each day of record. The frequency and duration that a given concentration was equaled or exceeded were then calculated to produce a frequency distribution for each site. “Reference” distributions were created using the stable sites in each ecoregion by averaging all of the distributions at specified exceedance intervals. As with the “reference” suspended‐sediment yields, there is a broad range of frequency and duration distributions that reflects the hydrologic and sediment‐transport regimes of the ecoregions. Ecoregions such as the Mississippi Valley Loess Plains (#74) maintain high suspended sediment concentrations for extended periods, whereas coastal plain ecoregions (#63 and 75) show much lower concentrations. 相似文献
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Simon J. Paech John R. Mecikalski David M. Sumner Chandra S. Pathak Quinlong Wu Shafiqul Islam Taiye Sangoyomi 《Journal of the American Water Resources Association》2009,45(6):1328-1342
Paech, Simon J., John R. Mecikalski, David M. Sumner, Chandra S. Pathak, Quinlong Wu, Shafiqul Islam, and Taiye Sangoyomi, 2009. A Calibrated, High‐Resolution GOES Satellite Solar Insolation Product for a Climatology of Florida Evapotranspiration. Journal of the American Water Resources Association (JAWRA) 45(6):1328‐1342. Abstract: Estimates of incoming solar radiation (insolation) from Geostationary Operational Environmental Satellite observations have been produced for the state of Florida over a 10‐year period (1995‐2004). These insolation estimates were developed into well‐calibrated half‐hourly and daily integrated solar insolation fields over the state at 2 km resolution, in addition to a 2‐week running minimum surface albedo product. Model results of the daily integrated insolation were compared with ground‐based pyranometers, and as a result, the entire dataset was calibrated. This calibration was accomplished through a three‐step process: (1) comparison with ground‐based pyranometer measurements on clear (noncloudy) reference days, (2) correcting for a bias related to cloudiness, and (3) deriving a monthly bias correction factor. Precalibration results indicated good model performance, with a station‐averaged model error of 2.2 MJ m?2/day (13%). Calibration reduced errors to 1.7 MJ m?2/day (10%), and also removed temporal‐related, seasonal‐related, and satellite sensor‐related biases. The calibrated insolation dataset will subsequently be used by state of Florida Water Management Districts to produce statewide, 2‐km resolution maps of estimated daily reference and potential evapotranspiration for water management‐related activities. 相似文献
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99.
Morgane Roger Nathalie Bonnardel Ludovic Le Bigot 《Journal of environmental psychology》2011,31(2):192-199
Tools for assisting human navigation, especially in-vehicle systems, have been extensively investigated. However, few studies have explored the design of speech-based over-the-phone guidance systems. This study examined the effect of landmarks' use and the effect of landmarks’ frames of reference in route instructions on navigation efficiency during map navigation tasks and satisfaction. Twenty-seven participants performed map navigation tasks using a simulated speech navigation system in three experimental conditions: instructions containing no landmarks, instructions containing landmarks located without reference to either the traveler’s body or the surrounding environment, and instructions containing landmarks located with respect to the traveler’s body. Navigation performances on maps were higher and landmarks enable participants to make fewer directional errors and find their routes more efficiently. Satisfaction levels and navigation performances were lower when instructions did not contain any landmarks. Landmarks’ frames of reference shifting turned out to be different between human-human situations previously used and human-computer situations used here. 相似文献
100.
The impact of the management of packaging waste on the environment, economic growth and job creation is analyzed in this paper. This integrated assessment intends to cover a gap in the literature for this type of studies, using the specific case study of the Portuguese packaging waste management system (SIGRE).The net environmental benefits associated with the management of packaging waste, are calculated using the Life Cycle Assessment methodology. The results show that, for the categories studied, the impacts associated to SIGRE's various activities are surpassed by the benefits associated to material and energy recovery, with special focus on recycling. For example, in 2011 SIGRE avoided the emission of 116 kt CO2 equiv. – the equivalent carbon emission of the electricity consumption of 124.000 households in Portugal.The economic impact of SIGRE is evaluated through Input–Output Analysis. It was found that SIGRE's activities also have a significant economic impact. For example, their added value are ranked amongst the upper third of the economic activities with highest multiplier effect at national level: this means that for each Euro of value added generated within SIGRE, 1.25 additional € are added to the rest of the economy (multiplier effect of 2.25).Regarding the social impacts of SIGRE, the number of direct jobs associated with the system is estimated to be more than two thousand and three hundred workers. Out of these, 83% are connected to the management of municipal waste packaging (selective collection and sorting), 15% are connected to the management of non-municipal packaging waste and only 2% are connected to the Sociedade Ponto Verde (SPV, green dot society in English) – the management entity responsible for SIGRE.In general terms, the results obtained provide quantitative support to the EEA (2011) suggestion that moving up the waste hierarchy – from landfilling to recycling – creates jobs and boosts the economy. 相似文献