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101.
Sources of nitrous and nitric oxides in paddy soils:Nitrification and denitrification 总被引:1,自引:0,他引:1
Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were carded out to investigate the processes responsible for N2O and NO production in two paddy soils with substantially different soil properties. Laboratory incubation experiments were carried out under aerobic conditions at moisture contents corresponding to 60% of water holding capacity. The relative importance of nitrification and denitrification to the flux of NaO was quantified by periodically measuring and comparing the enrichments of the N2O, NH~-N and NO3-N pools. The results showed that both N2O and NO emission rates in an alkaline paddy soil with clayey texture were substantially higher than those in a neutral paddy soil with silty loamy texture. In accordance with most published results, the ammonium N pool was the main source of N2O emission across the soil profiles of the two paddy soils, being responsible for 59.7% to 97.7% of total N2O emissions. The NO3-N pool of N2O emission was relatively less important under the given aerobic conditions. The rates of N2O emission from nitrification (N2On) among different soil layers were significantly different, which could be attributed to both the differences in gross N nitrification rates and to the ratios of nitrified N emitted as NzO among soil layers. Furthermore, NO fluxes were positively correlated with the changes in gross nitrification rates and the ratios of NO/N2O in the two paddy soils were always greater than one (from 1.26 to 6.47). We therefore deduce that, similar to N2O, nitrification was also the dominant source of NO in the tested paddy soils at water contents below 60% water holding capacity. 相似文献
102.
Rolf D. Vinebrooke Mark D. Graham David L. Findlay Michael A. Turner 《Ambio-人类环境杂志》2003,32(3):196-202
藻类群落对恢复中酸化湖泊的环境变化具有高度响应性.本文比较了北方湖泊的石生藻类群落从大气酸化(安大略省基拉尼公园)和实验酸化(南302湖,安大略省实验湖泊区)的化学恢复,以评价严重酸化的时空尺度对分类学复原能力(即恢复速率)的影响.复原能力以经过典型对应分析(CCA)湖泊在pH恢复过程中的排序空间上的位移来表示.基拉尼湖泊的复原能力相对而言几乎可以忽略,说明南303号湖8年时间酸化实验对生物恢复的影响要弱于几十年来的大气酸化作用.溶解性有机碳、溶解性无机碳以及钙的增长很好地解释了恢复过程中的酸化湖泊的石生物种丰度的时间变化.南302湖中观察到了相反的分类学复原能力和抗性的轨迹(抗性指扰动后自原来状态的偏离),显示在恢复和酸化过程中影响石生物种的生态因子随相应的pH值不同而不同.本文的发现揭示了在对严重酸化湖泊的生态系统恢复建立模型时,一定要考虑扰动的时空尺度以及引起恢复和酸化轨迹差异的生物滞后响应. 相似文献
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Numerous evaluation tools for the built environment have been developed in recent decades only some however integrate the outdoor environment. In EcoEffect, a Swedish assessment system, the outdoor environment is one of five areas covered. The purpose of this article is to describe and discuss various issues that evolved during the testing and developing phase of the EcoEffect Outdoor tool. The tool is designed to cover all important health risks to people in an outdoor environment, to show the relationship between circumstances in the outdoor environment and the levels specified in Swedish legislation and to enable a speedy and accurate assessment of the outdoor environment on a property. The work has been carried out in cooperation with experts, residents and representatives of the construction and property sectors. The tool has been tested on existing properties, discussed in focus groups, and has been subject to theoretical development. The results have provided a basis for changing both the EcoEffect Outdoors tool and the framework of the EcoEffect system. Important conclusions here include the notion that a clear account should be given of the fundamental values of the tool, that environmental impact should be reported in the same way throughout the whole assessment process and that the tool has to adhere to both scientific and practical validity to be useful for the building sector. 相似文献
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Werner Brack Rolf Altenburger Falk Dorusch Andreas Hubert Monika Möder Peter Morgenstern Susanne Moschütz Sibylle Mothes Kristin Schirmer Rainer Wennrich Klaus -Dieter Wenzel Gerrit Schüürmann 《Environmental Sciences Europe》2002,14(4):213-220
In August 2002, highly contaminated areas in the region of Bitterfeld, e.g. the floodplain of the creek Spittelwasser, as well as the adjacent regions of Jeßnitz and Raguhn, were submerged by the river Mulde. An input of mobilized contaminated sediments in residential areas was the matter of concern. The objective of the present study was to estimate the pollutants load on the basis of chemical and biological data and identify the sources of pollutants. Deposited sludge and flood water samples were assessed on the basis of biological and chemical analyses and in comparison with administrative reference values. The pollution of the investigated sites was rather heterogeneous. At several sites, tolerance limits of the German Klärschlammverordnung or the Bundesbodenschutzverordnung were clearly exceeded, e.g. for Pb, As and HCH. Organic extracts exhibited significant effects in several biotests. This may be relevant with respect to direct particle uptake via ingestion or respiration. Pollution patterns for heavy metals as well as for organic pollutants differed significantly from the pattern found in the Spittelwasser flood plain before the inundation, which is in contrast to the initial hypothesis of a possible transport of contaminated Spittelwasser sediments into residential areas. Interestingly, a correlation of chemical load and the overall biological effect could be shown. From the viewpoint of the precautionary principle, the identification of the compounds exerting toxic effects and of the respective pollutant sources would be desirable. 相似文献
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