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A procedure for the determination of atmospheric acrylic acid in air at the microgram m-3 to mg m-3 level is described. Diffusion-based sampling, designed to discriminate gaseous analytes from their particulate counterparts, has been used. Acrylic acid is collected with an efficiency of > 98% in tubular denuders coated with sodium hydroxide-barium hydroxide-hydroquinone monomethyl ether, and analyzed by high performance liquid chromatography with UV absorbance detection. The detection limit is 2.9 micrograms m-3 at a flow rate of 0.5 L min-1 and 30 min sampling time. A precision (p = 0.95, n = 10) of 7.5% of the overall procedure was achieved at the 100 micrograms m-3 level. Results of laboratory studies concerning the effect of the coating reagent and the relative humidity on the sampling efficiency as well as possible interferences, in particular by ozone, and the elimination of these interferences are discussed. This method was developed to monitor workplace atmospheres as well as ambient air in industrial environments. 相似文献
13.
Craig Loehle T. Bently Wigley Erik Schilling Vickie Tatum John Beebe Eric Vance Paul Van Deusen Philip Weatherford 《Environmental management》2009,44(6):1136-1148
Managed forests are a primary land use within the Coastal Plain of the southern United States. These forests are generally
managed under standards, guidelines, or regulations to conserve ecosystem functions and services. Economic value of commercial
forests provides incentives for landowners to maintain forests rather than convert them to other uses that have substantially
reduced environmental benefits. In this review, we describe the historical context of commercial forest management in the
southern United States Coastal Plain, describe how working forests are managed today, and examine relationships between commercial
forest management and maintenance of functional aquatic and wetland systems and conservation of biological diversity. Significant
challenges for the region include increasing human population and urbanization and concomitant changes in forest area and
structure, invasive species, and increased interest in forest biomass as an energy feedstock. Research needs include better
information about management of rare species and communities and quantification of relationships between ecosystem attributes
and forest management, including biomass production and harvest. Incentives and better information may help commercial forest
managers in the Coastal Plain more efficiently contribute to landscape-scale conservation goals. 相似文献
14.
S. Reth W. Graf O. Gefke R. Schilling H. K. Seidlitz J. C. Munch 《Water, Air, & Soil Pollution: Focus》2008,8(2):129-137
Despite many studies of the N2O emission, there is a lack of knowledge on the role of subsoil for N2O emission, particularly in sandy soils. To obtain insight into the entrapment, diffusion, convection and ebullition of N2O in the soil, the N2O concentration in the soil atmosphere was measured over a period of 1 year in 4 lysimeters (agricultural soil monoliths of
1 m2 × 2 m) at 30, 50, 80, 155, and 190 cm depth with altogether 86 gas probes. Additionally the N2O emission into the atmosphere was measured in 20 closed chambers at the soil surface. Concurrently the soil temperature and
soil water content were recorded in order to quantify their effects on the fate of N2O in the soil. Results of the continuous measurements between January and December 2006 were: N2O concentrations were highest in the deeper soil; maximum concentration was found at a depth of 80 cm, where the water content
was high and the gas transport reduced. The highest N2O concentration was recorded after ‘special events’ like snowmelt, heavy rain, fertilization, and grubbing. The combination
of fertilization and heavy rain led to an increase of up to 2,700 ppb in the subsoil. 相似文献
15.
Lockaby BG Governo R Schilling E Cavalcanti G Hartsfield C 《Journal of environmental quality》2005,34(1):390-396
The influence of sedimentation rates on biogeochemistry of riparian forests was studied near ephemeral streams at Fort Benning, GA. Upper reaches of seven ephemeral streams had received varying rates of sedimentation stemming from erosion along unpaved roadways at the military installation. Two reference catchments were also included in the study. Decomposition of foliar litter, microbial C and N, N mineralization, and arthropod populations were compared within and among catchments. Rates of sedimentation over the past 25 yr ranged from 0 in references to 4.0 cm yr(-1). Decomposition rates declined exponentially with sedimentation rates as low as 0.20 to 0.32 cm yr(-1) and appeared to reach an equilibrium at a sedimentation rate of 0.5 cm yr(-1). Nitrogen mineralization and microbial C and N followed the same trend. Sedimentation had no discernible effect on arthropod populations. These data suggest that biogeochemical cycles may be altered by sedimentation rates that commonly occur in some floodplain forests. 相似文献
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Keith E. Schilling Thomas M. Isenhart Jason A. Palmer Calvin F. Wolter Jean Spooner 《Journal of the American Water Resources Association》2011,47(4):672-686
Schilling, Keith E., Thomas M. Isenhart, Jason A. Palmer, Calvin F. Wolter, and Jean Spooner, 2011. Impacts of Land‐Cover Change on Suspended Sediment Transport in Two Agricultural Watersheds. Journal of the American Water Resources Association (JAWRA) 47(4):672‐686. DOI: 10.1111/j.1752‐1688.2011.00533.x Abstract: Suspended sediment is a major water quality problem, yet few monitoring studies have been of sufficient scale and duration to assess the effectiveness of land‐use change or conservation practice implementation at a watershed scale. Daily discharge and suspended sediment export from two 5,000‐ha watersheds in central Iowa were monitored over a 10‐year period (water years 1996‐2005). In Walnut Creek watershed, a large portion of land was converted from row crop to native prairie, whereas in Squaw Creek land use remained predominantly row crop agriculture. Suspended sediment loads were similar in both watersheds, exhibiting flashy behavior typical of incised channels. Modeling suggested that expected total soil erosion in Walnut Creek should have been reduced 46% relative to Squaw Creek due to changes in land use, yet measured suspended sediment loads showed no significant differences. Stream mapping indicated that Walnut Creek had three times more eroding streambank lengths than did Squaw Creek suggesting that streambank erosion dominated sediment sources in Walnut Creek and sheet and rill sources dominated sediment sources in Squaw Creek. Our results demonstrate that an accounting of all sources of sediment erosion and delivery is needed to characterize sediment reductions in watershed projects combined with long‐term, intensive monitoring and modeling to account for possible lag times in the manifestation of the benefits of conservation practices on water quality. 相似文献
19.
Keith E. Schilling Eileen McLellan E. Arthur Bettis III 《Environmental management》2013,52(6):1440-1452
In this paper, we argue that there is tremendous potential for nitrate-N reductions to occur throughout the Corn Belt region of the USA if we simply let naturally occurring wet spots on the landscape be wet. Geologic and hydrologic data gathered in the Walnut Creek watershed located in south-central Iowa provides compelling evidence that substantial nutrient-processing capacity exists in this dissected glacial landscape. Self-similarity of stratigraphy, sedimentology and hydrology observed at all spatial scales in the watershed suggests that Holocene alluvial fill deposits provide a natural bioreactor for denitrification of upland groundwater nitrate-N; the occurrence of such deposits can be mapped to identify potential nitrogen sinks across the landscape. This approach to identifying potential nitrogen sinks is geology focused and extends potential locations for nutrient processing upstream into the headwater catchments of individual fields. 相似文献
20.
Scents form the basis for the fragrance industry and various research activities have been developed in different scientific
disciplines all being linked by a common interest in odors and odor perception. In this paper, four different topics have
been selected for a short discussion. Following a short overview on the history of perfumery, the first topic (Natural scents)
is providing some insight into the investigation of natural scents and how this work has strongly stimulated fragrance creation
as well as the quest to find new odoriferous substances for the perfumer’s palette. The second subject (Fragrance chemistry)
gives a historical overview over the chemistry of fragrances and briefly describes the rational behind the synthesis and composition
of new scents. Body odors and their biochemical formation concern the third topic (Body odor biochemistry) which describes
our current understanding of this scientifically interesting field and how knowledge may find use to improve future deodorant
products. The fourth subject (Olfactory mechanisms) deals with the biochemistry in the human nose when odorants are activating
olfactory receptors and enzymes appear to rapidly metabolize the inhaled odorous stimuli. This review does not attempt to
be comprehensive, but it describes selected successes in the fragrance industry and the motivation behind conducting various
types of research. Ultimately, the activities are aiming to bring new ingredients onto the market and improve the quality
of scented products but also to advance our understanding of the power of communication through fragrance. 相似文献