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41.
G. B. Howe R. K. M. Jayanty A. V. Rao W. F. Gutknecht C. E. Decker D. J. von Lehmden 《Journal of the Air & Waste Management Association (1995)》2013,63(9):823-826
A repository of 38 gaseous organic compounds in compressed gas cylinders has been established by EPA. This repository was established to provide standards for source test performance audits, that is, quantitative quality assurance tests. Among these compounds are ten halogenated organic species, which are the focus of this paper. Stability studies of all ten compounds have been performed to determine the feasibility of using them as performance audit standards. Results indicate that all of the halocarbons tested are adequately stable to be used as reliable audit standards. Subsequent to completion of stability studies, four of the ten halocarbons were used in source test performance audits. Results are available at this time for two of the four compounds; the results show agreement within 10% of the concentrations previously established by Research Triangle Institute. 相似文献
42.
Friedrich U von Oheimb G Dziedek C Kriebitzsch WU Selbmann K Härdtle W 《Environmental pollution (Barking, Essex : 1987)》2011,159(12):3553-3559
We analysed growth strategies (biomass allocation, nutrient sequestration and allocation) of heather (Calluna vulgaris) and purple moor-grass (Molinia caerulea) seedlings in monocultures and mixtures in relation to N, P, and N + P fertilisation in a greenhouse experiment in order to simulate a heath’s pioneer phase under high airborne nitrogen (N) loads. N fertilisation increased the total biomass of both species in monocultures. In mixtures, M. caerulea sequestered about 65% of the N applied, while C. vulgaris suffered from N shortage (halving of the total biomass). Thus, in mixtures only M. caerulea will benefit from airborne N loads, and competition will become increasingly asymmetric with increasing N availability. Our results demonstrate that the heath’s pioneer phase is the crucial tipping point at which the competitive vigour of M. caerulea (high belowground allocation, efficient use of belowground resources, shortened reproductive cycles) induces a shift to dominance of grasses under increased N availability. 相似文献
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Uwe Heiser Stefan Norra Doris Stüben Magnus von Wagner 《Umweltwissenschaften und Schadstoff-Forschung》1999,11(1):15-19
Für die Anwendung der sequentiellen Schwermetallextraktion auf Proben, die nur im Milligramm-Bereich erhalten werden k?nnen
(Mikroproben, wie z. B. Staubniederschl?ge), wurde die Methode vonZeien &Brümmer (1989) weiterentwickelt. Der Extraktionsma?stab wurde um den Faktor 1∶100 verringert und die Reproduzierbarkeit des Verfahrens
mit variablen Probenmengen um 20mg und einem Extraktionsvolumen von 500 μl mit Hilfe von Standardb?den nachgewiesen. M?gliche
Einflüsse variabler Extraktionsverh?ltnisse (Verh?ltnis von Probenmenge zu Extraktionsvolumen) sowie eine aufwendige Vorbehandlung
von Staubproben, die nach der Bergerhoff-Methode (VDI 2119/2, 1972) gesammelt wurden, lagen bei diesen Untersuchungen weitgehend
im Variationsbereich des Verfahrens. Die sequentielle Extraktion kann folglich zur Untersuchung der Mobilisierbarkeit von
Schwermetallen auch aus Mikroproben mit variablen Probenmengen eingesetzt werden.
Mit Hilfe dieses Verfahrens wurden die Mobilisierbarkeiten von Zink, Kupfer und Blei der Schluff- und Tonfraktion von Stra?ensedimenten
mit Staubniederschl?gen an zwei urbanen Standorten mit unterschiedlicher, verkehrsbedingter Schwermetallbelastung verglichen.
Diese Untersuchungen werden in Teil 2 (“Sequentielle Schwermetallextraktion von st?dtischen St?uben”) vorgestellt. 相似文献
45.
In Europe, the use of direct methods using lysimeters for measuring water and solute flow in soils increased in recent years.
Large weighable lysimeters are best suitable for obtaining reliable data about seepage water quantity and quality. Field lysimeters
– lysimeters built in directly in agriculturally used areas – of high technical standard allow a precise determination of
the influence of different cropping systems on groundwater quality. They combine the advantages of true field conditions and
laboratory possibilities of varying parameters, handling and maintenance. Due to the specific needs of each application the
instrumentation varies. Based on general remarks on the advantages of precise weighing lysimeters four standardized lysimeter
configurations are presented. Beside the specific needs of design and setup of lysimeter stations, there is need to define
general requirements to enable comparable results based on standardized basic design and to reduce individual mistakes. 相似文献
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Surface runoff is one of the most important pathways for pesticides to enter surface waters. Mathematical models are employed to characterize its spatio-temporal variability within landscapes, but they must be simple owing to the limited availability and low resolution of data at this scale. This study aimed to validate a simplified spatially-explicit model that is developed for the regional scale to calculate the runoff potential (RP). The RP is a generic indicator of the magnitude of pesticide inputs into streams via runoff. The underlying runoff model considers key environmental factors affecting runoff (precipitation, topography, land use, and soil characteristics), but predicts losses of a generic substance instead of any one pesticide. We predicted and evaluated RP for 20 small streams. RP input data were extracted from governmental databases. Pesticide measurements from a triennial study were used for validation. Measured pesticide concentrations were standardized by the applied mass per catchment and the water solubility of the relevant compounds. The maximum standardized concentration per site and year (runoff loss, RLoss) provided a generalized measure of observed pesticide inputs into the streams. Average RP explained 75% (p < 0.001) of the variance in RLoss. Our results imply that the generic indicator can give an adequate estimate of runoff inputs into small streams, wherever data of similar resolution are available. Therefore, we suggest RP for a first quick and cost-effective location of potential runoff hot spots at the landscape level. 相似文献
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