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2009年12月,来自中国、美国以及世界各国的代表将在丹麦哥本哈根聚首,争取达成一项应对气候变化的国际协议,为2012年<京都议定书>第一承诺期结束后的发展指明方向.今年虽然是全球在气候变化领域取得巨大进展的一年,但仍有许多观察人士开始担心各国将无法在哥本哈根会议上充分弥合分歧. 相似文献
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Thorsten Junge Nicola Claßen Andreas Schäffer Burkhard Schmidt 《Journal of environmental science and health. Part. B》2013,48(9):858-868
The fate of 14C-labeled difloxacin (14C-DIF) was studied in time course experiments after application on soil (Ap horizon of silt loam) and amendment of authentic DIF containing pig manure (146 mL kg?1; 4.17 MBq kg?1; 0.85 mg kg?1) or water (124 mL kg?1; 0.42 MBq kg?1; 0.09 mg kg?1) for 56 and 120 days of incubation, respectively. Mineralization of 14C-DIF was below 0.2% in both experiments after 56 days or 120 days. In the course of the experiments, portions of extractable radioactivity (Accelerated Solvent Extraction (ASE); acetonitrile-water) decreased to 19–21% depending only little on manure amendment. Non-extractable residues of 14C-DIF increased to 70–74% after 56 days and 120 days, respectively, and therefore were the main route of 14C-DIF in soil. According to radioanalytical HPLC and LC-MS/MS, only the parent compound was found in all extracts over the whole time of the experiment. According to fractionation of the non-extractable residues (NER) into particle size fractions, 14C portions were associated to the water used for fractionation, the silt and clay fractions, whereas no radioactivity was detected in the sand fraction. The majority of 14C was found within the clay fractions. Fractionation of humic components showed that radioactivity derived from 14C-DIF was associated with humic acids, fulvic acids, humins and minerals and very little with soluble, non-humic HCl fraction. The highest portions of radioactivity were found in the fulvic acid fraction. Results obtained by size exclusion chromatography (SEC) of the purified fulvic acids were similar for every sample analyzed. One large portion of 14C co-eluted with fulvic acids of a molecular weight below 910 g mol?1. Both fractionation methods demonstrated that the parent compound DIF or initial metabolites were rapidly integrated into humic materials and, thus, were major components of NER. 相似文献
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Comparison of efficacy of three extractants to solubilize glomalin on hyphae and in soil 总被引:1,自引:0,他引:1
Glomalin, a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, is a major component of the humus fraction of soil organic matter. Glomalin is extracted from soil and hyphae of AM fungi by using sodium citrate at 121 degrees C in multiple 1-h cycles, but extensive extraction does not solubilize all glomalin in all soils. Efficacies of 100 mM sodium salts of citrate, borate or pyrophosphate (pH 9.0, 121 degrees C) were tested for two 1-h cycles for hyphae from four AM fungal isolates and four 1-h cycles for seven soils from four US geographic regions. Residual soil glomalin was examined by pyrophosphate extraction of soils previously extracted with citrate or borate followed by extraction of all soils after treatment with NaOH. Hyphal extracts were compared using Bradford-reactive total protein (BRTP) values, and extracts from soils were compared using BRTP, percentage C and C weight. No difference among extractants was detected for AM fungal isolates or across soils. The residual glomalin across soils for extractants contained the following percentages of the total BRTP: pyrophosphate, 14%; borate, 17%; and citrate, 22%. Comparisons among individual soils indicated that pyrophosphate extracted significantly more BRTP (10-53%) than borate or citrate in six soils and borate was equal to pyrophosphate in one soil. Extraction with borate should be compared with pyrophosphate before initiating an experiment. For routine extractions of ca. 85% of the glomalin across a variety of soils, sodium pyrophosphate appears to be equal to or better than borate and better than citrate. 相似文献
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Abstract: Wilderness areas are protected and valued in part for recreation; recreational use, however, can negatively impact these areas. In particular, recreational use can facilitate transport of non-native propagules and create open sites for establishment of non-native species. We examined the role of recreational portage trails in the introduction and establishment of non-native plants into the Boundary Waters Canoe Area Wilderness of northern Minnesota (U.S.A.). On 20 portages, we sampled non-native plant richness and cover at four distances (0, 10, 25, and 50 m) from trails. Non-native richness and cover were not related to distance from wilderness entry point. Non-native richness and cover were, however, negatively related to distance from trails. All six non-native species we observed were either directly on or within 1 m of trails. These results suggest that recreational trails act as corridors facilitating invasions of non-native plants into wilderness areas. It remains unclear, however, whether these effects are caused by dispersal of propagules, creation of bare ground, or changes in the native plant community. 相似文献
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