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61.
Joseph P. Herring Richard C. Schultz Thomas M. Isenhart 《Journal of the American Water Resources Association》2006,42(1):145-155
An observational study was conducted at the watershed scale using land cover (vegetation) data to assess the absence or presence of riparian buffers in three northeastern Missouri watersheds. Forests and grasslands lying within a 61 m (200 ft) parallel band directly adjacent to streams were considered “buffers” for improving or protecting water quality and were characterized according to their length, width, and vegetation type. Results indicated that riparian buffers were abundant throughout the watersheds but were typically narrow along first‐order and second‐order streams; in many cases they may not have been wide enough to provide adequate stream protection. At least 90 percent of all streams had buffer vegetation immediately adjacent to the streambanks, but as few as 31 percent of first‐order streams had buffers extending to 61 m from the stream on at least one side. On‐site evaluations are needed to determine the condition of these forests and grasslands and their ability to process nonpoint source pollutants. The results will be useful for providing natural resource managers with knowledge of current watershed conditions as well as in identifying specific locations for future conservation efforts within each watershed. 相似文献
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Results of analyses of eight samples of technical pentachlorophenol conducted by three different analytical methods are presented and discussed. 相似文献
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Gas-liquid chromatography was used to study the effects of saponification/methylation and thin-layer chromatographic isolation on the analyses of polyunsaturated fatty acids. Using selected procedures, the qualitative and quantitative distribution of these acids in marine organisms can be determined with a high degree of accuracy. 相似文献
66.
Paasivirta J Kukkola J Knuutinen J Pessala P Schultz E Herve S 《Environmental science and pollution research international》2005,12(6):375-380
Background, Aim and Scope At present, large-scale paper manufacture involves delignification and bleaching by elemental chlorine free (ECF) or totally
chlorine free (TCF) processes. The wastewater is purified by secondary treatment (mechanical, chemical and biological) which
removes most of the toxic substances from the discharge. However, we found residual toxicity in the high molecular (> 1000
D) matter (HMWM) of the discharge by test of the RET (reverse electronic transfer) inhibition.
This fraction consists mainly of polydisperse lignin (LIG) and carbohydrate (CH) macromolecules. Structural units in these
molecules are studied by pyrolysis gas chromatography / mass spectrometry (Pyr-GC/MS). In the present work, our aim was to
find out those structural units which could explain the RET toxicity of LIG or CH molecules. We compared statistically RET
toxicity values of the HMWM samples from treated wastewaters of pilot pulping experiments and intensity variation of the pyrolysis
product gas chromatograms of these samples. This application is a novel study procedure.
Methods Pyrolysis products (Py-GC/MS results) and inhibition of RET (reverse electronic transport toxicity) as TU50 and TU20 of HMWM
(High Molecular Weight Material; Mw > 1000 D) were compared by multivariate statistics. The samples were from laboratory pilot
stages of TCF (Totally Chlorine Free) and ECF (Elemental Chlorine Free) manufacture of softwood pulp. Py-GC/MS was done without
and with addition of TMAH (Tetra Methyl Ammonium Hydroxide). The name and structure of each abundant fragment compound was
identified from its retention time and mass spectrum compared to authentic reference compounds or literature. Four sets of
Toxicity Units (TUs) and GC peak areas of the pyrolysis fragments were obtained. The data were normalized by division with
LIG (lignin content of each sample). TU values were dependent and the fragment values independent (explanatory) variables
in statistical treatments by SPSS system. Separate analyses of correlations, principal components (PCA) and stepwise multiple
linear regression (SMLR) were performed from the four sample sets TCF and ECF with and without TMAH.
Results and Discussion From the CH fragments, 2-furfural in TCF, and from the LIG fragments, styrene in ECF showed the highest probabilities to
originate from source structures of toxicity. Other possible compounds in concern were indicated to be CH fragment 2-methyl-2-cyclopenten-1-one
in ECF and LIG fragments 2-methoxy-4-methylphenol, 4,5-dimethoxy-2-methylphenol and 2-methylphenol in TCF. 相似文献
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A new ant species of Megalomyrmex conducts mass raids to usurp gardens of the fungus-growing ant Cyphomyrmex longiscapus, then lives in the gardens and consumes the cultivated fungus. Unlike attine ants, however, Megalomyrmex sp. does not forage for substrate to manure the gardens; therefore, when gardens become depleted, Megalomyrmex sp. must locate and usurp new gardens. Megalomyrmex sp. workers feed their larvae with attine brood, but only after removing the fungal mycelium that covers the attine larval integument,
suggesting that this fungal coat may provide partial protection against other predators. Unlike other known Megalomyrmex species, which coexist as social parasites in attine colonies, Megalomyrmex sp. expels its attine hosts during the garden raids. Megalomyrmex sp. thus maintains a unique agro-predatory lifestyle that is described here for the first time.
Received: 18 August 2000 / Accepted in revised form: 1 November 2000 相似文献
68.
ebnem Andreani-Aksoyolu Johannes Keller Carlos Ordez Michel Tinguely Martin Schultz Andr S.H. Prvt 《Ecological modelling》2009,217(3-4):209
In this study, we investigated the effect of numerous regulations enforced since 1985 to improve air quality on ozone in Europe with the focus on Switzerland, using the Comprehensive Air Quality Model with Extensions (CAMx) for a specific summer period. Several emission scenarios for the year 2010 were also considered. The model results suggest that the emission reductions of ozone precursors should have been effective to reduce ozone production between 1985 and 2000 in northern Switzerland. However, observations do not indicate any significant change in surface ozone levels since early 1990s, except in the region of Zurich where there is a small negative trend. On the other hand, the model predictions match very well the spatial variability of the trends but the calculated trends are around 0.5 ppb year−1 lower than those observed. This difference is similar to the background ozone increase as suggested by the long-term observations at the high Alpine station Jungfraujoch. These results support the hypothesis that the decrease in local ozone production due to emission reductions might have been partly or completely compensated by the simultaneous increase in the background ozone. In 2010, a strict application of the Gothenburg Protocol in Europe would lead to a decrease in peak ozone concentrations by about 5% in Switzerland under the meteorological conditions applied. Our calculations also indicated that emission controls only in Switzerland would not be very effective to improve the air quality in the future. The further development of the background ozone will in any case be very important for the tropospheric ozone levels. 相似文献
69.
Kris W. Knight Richard C. Schultz Cathy M. Mabry Thomas M. Isenhart 《Journal of the American Water Resources Association》2010,46(2):311-322
Knight, Kris W., Richard C. Schultz, Cathy M. Mabry, and Thomas M. Isenhart, 2010. Ability of Remnant Riparian Forests, With and Without Grass Filters, to Buffer Concentrated Surface Runoff. Journal of the American Water Resources Association (JAWRA) 46(2):311-322. DOI: 10.1111/j.1752-1688.2010.00422.x Abstract: Riparian forest buffers established according to accepted conservation practice standards have been recommended as one of the most effective tools for mitigating nonpoint source pollution. The midwestern United States is characterized by many kilometers of narrow, naturally occurring forests along streams. However, little is known about the relative effectiveness of these remnant forests compared with these newly established buffers. This study compared the ability of naturally occurring remnant forests with and without adjacent planted grass filters to buffer concentrated flow paths (CFPs) originating in crop fields along first- and second-order streams in three northeast Missouri watersheds. Remnant forests breached by runoff through CFPs were narrower than those that dispersed 100% of the CFPs. Remnant forests with adjacent grass buffers were nearly twice the width as those without grass filters. We also found that CFPs, which developed within remnant forests and at the base of in-field grass waterways, were potential sources of sediments to streams. Methods to mitigate these CFPs warrant further investigation. Our study suggests that although these natural remnant forests provide substantial buffering capacity, both improved management and/or the addition of an adjacent grass filter would improve water quality by reducing sediment loss to streams. Inferences can be used to inform the design and management of similar conservation buffer systems within the region. 相似文献
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