673 research outputs found

    Estimating total horizontal aeolian flux within shrub-invaded groundwater-dependent meadows using empirical and mechanistic models

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    Wind erosion is a significant environmental problem that removes soil resources from sensitive ecosystems and contributes to air pollution. In regions of shallow groundwater, friable (puffy) soils are maintained through capillary action, surface evaporation of solute-rich soil moisture, and protection from mobilization by groundwater-dependent grasses and shrubs. When a reduction in vegetation cover occurs through any disturbance process, there is potential for aeolian transport and dust emission. We find that as mean gap size between vegetation elements scaled by vegetation height increases, total horizontal aeolian sediment flux increases and explains 58% of the variation in total horizontal aeolian sediment flux. We also test a probabilistic model of wind erosion based on gap size between vegetation elements scaled by vegetation height (the Okin model), which predicts measured total horizontal aeolian sediment flux more closely than another commonly used model based on the average plant area observed in profile (Raupach model). The threshold shear velocity of bare soil appears to increase as gap size between vegetation elements scaled by vegetation height increases, reflecting either surface armoring or reduced interaction between the groundwater capillary zone and surface sediments. This work advances understanding of the importance of measuring gap size between vegetation elements scaled by vegetation height for empirically estimating Q and for structuring process-based models of desert wind erosion in groundwater-dependent vegetation

    Assessing gender mainstreaming in the education sector: depoliticised technique or a step towards women's rights and gender equality?

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    In 1995 the Beijing Conference on Women identified gender mainstreaming as a key area for action. Policies to effect gender mainstreaming have since been widely adopted. This special issue of Compare looks at research on how gender mainstreaming has been used in government education departments, schools, higher education institutions, international agencies and NGOs .1 In this introduction we first provide a brief history of the emergence of gender mainstreaming and review changing definitions of the term. In the process we outline some policy initiatives that have attempted to mainstream gender and consider some difficulties with putting ideas into practice, particularly the tensions between a technical and transformative interpretations . Much of the literature about experiences with gender mainstreaming tends to look at organizational processes and not any specificities of a particular social sector. However, in our second section, we are concerned to explore whether institutional forms and particular actions associated with education give gender mainstreaming in education sites some distinctive features. In our last section we consider some of the debates about global and local negotiations in discussions of gender policy and education and the light this throws on gender mainstreaming. In so doing, we place the articles that follow in relation to contestations over ownership, political economy, the form and content of education practice and the social complexity of gender equality

    Mothers of Soldiers in Wartime: A National News Narrative

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    National news media represent mothers of US combat soldiers in the Iraq War as archetypal good mothers, that is, mothers who continue their maternal work even after their children are deployed. However, not all mothers are depicted as the archetypal patriotic mother, i.e., a good mother who is also stoic and silent about the war and her child\u27s role in it. Mothers of soldiers are portrayed as good mothers who sometimes also voice their attitudes about the war effort. The maternal attitudes ranged from complete support for the war to opposition to the war but support for the soldiers. The findings suggest a picture of wartime motherhood that is more nuanced than the historical image of the patriotic mother suggests

    Empowering minority women: Autonomy versus participation

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    Feminist attempts to empower women within their own cultural traditions have employed two broad strategies: authentic choice and participation. This paper argues that the methodological problems that beset the authentic choice strategy tell in favour of the participation approach. However, proponents of the participation strategy have failed to pay sufficient attention to the background conditions that need to be met if women are to make effective use of the institutional mechanisms their models advocate. If women are to be effective political agents at least some of the most serious structural inequalities that women face must be addressed. A nuanced statement of the participation strategy must therefore take account of long-standing feminist concerns regarding economic equality and access to resources. While this approach falls short of the demanding conditions for democratic citizenship implicit in the authentic choice strategy, it none the less places significant limits on the scope of participatory strategies and links the goal of empowering women within their own cultural traditions to wider feminist struggles to secure greater economic equality for women in general

    Observation- and Model-Based Estimates of Particulate Dry Nitrogen Deposition to the Oceans

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    © Author(s) 2017. This is an Open Access article distributed under the Creative Commons Attribution License CC BY 3.0 ( https://creativecommons.org/licenses/by/3.0/ ). Published by Copernicus Publications on behalf of the European Geosciences Union.Anthropogenic nitrogen (N) emissions to the atmosphere have increased significantly the deposition of nitrate (NO3−) and ammonium (NH4+) to the surface waters of the open ocean, with potential impacts on marine productivity and the global carbon cycle. Global-scale understanding of the impacts of N deposition to the oceans is reliant on our ability to produce and validate models of nitrogen emission, atmospheric chemistry, transport and deposition. In this work,  ∼  2900 observations of aerosol NO3− and NH4+ concentrations, acquired from sampling aboard ships in the period 1995–2012, are used to assess the performance of modelled N concentration and deposition fields over the remote ocean. Three ocean regions (the eastern tropical North Atlantic, the northern Indian Ocean and northwest Pacific) were selected, in which the density and distribution of observational data were considered sufficient to provide effective comparison to model products. All of these study regions are affected by transport and deposition of mineral dust, which alters the deposition of N, due to uptake of nitrogen oxides (NOx) on mineral surfaces. Assessment of the impacts of atmospheric N deposition on the ocean requires atmospheric chemical transport models to report deposition fluxes; however, these fluxes cannot be measured over the ocean. Modelling studies such as the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), which only report deposition flux, are therefore very difficult to validate for dry deposition. Here, the available observational data were averaged over a 5° × 5° grid and compared to ACCMIP dry deposition fluxes (ModDep) of oxidised N (NOy) and reduced N (NHx) and to the following parameters from the Tracer Model 4 of the Environmental Chemical Processes Laboratory (TM4): ModDep for NOy, NHx and particulate NO3− and NH4+, and surface-level particulate NO3− and NH4+ concentrations. As a model ensemble, ACCMIP can be expected to be more robust than TM4, while TM4 gives access to speciated parameters (NO3− and NH4+) that are more relevant to the observed parameters and which are not available in ACCMIP. Dry deposition fluxes (CalDep) were calculated from the observed concentrations using estimates of dry deposition velocities. Model–observation ratios (RA, n), weighted by grid-cell area and number of observations, were used to assess the performance of the models. Comparison in the three study regions suggests that TM4 overestimates NO3− concentrations (RA, n =  1.4–2.9) and underestimates NH4+ concentrations (RA, n =  0.5–0.7), with spatial distributions in the tropical Atlantic and northern Indian Ocean not being reproduced by the model. In the case of NH4+ in the Indian Ocean, this discrepancy was probably due to seasonal biases in the sampling. Similar patterns were observed in the various comparisons of CalDep to ModDep (RA, n =  0.6–2.6 for NO3−, 0.6–3.1 for NH4+). Values of RA, n for NHx CalDep–ModDep comparisons were approximately double the corresponding values for NH4+ CalDep–ModDep comparisons due to the significant fraction of gas-phase NH3 deposition incorporated in the TM4 and ACCMIP NHx model products. All of the comparisons suffered due to the scarcity of observational data and the large uncertainty in dry deposition velocities used to derive deposition fluxes from concentrations. These uncertainties have been a major limitation on estimates of the flux of material to the oceans for several decades. Recommendations are made for improvements in N deposition estimation through changes in observations, modelling and model–observation comparison procedures. Validation of modelled dry deposition requires effective comparisons to observable aerosol-phase species' concentrations, and this cannot be achieved if model products only report dry deposition flux over the ocean.Peer reviewedFinal Published versio
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