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A benzene-degrading nitrate-reducing microbial consortium displays aerobic and anaerobic benzene degradation pathways
In this study, we report transcription of genes involved in aerobic and anaerobic benzene degradation pathways in a benzene-degrading denitrifying continuous culture. Transcripts associated with the family Peptococcaceae dominated all samples (21–36% relative abundance) indicating their key role in the community. We found a highly transcribed gene cluster encoding a presumed anaerobic benzene carboxylase (AbcA and AbcD) and a benzoate-coenzyme A ligase (BzlA). Predicted gene products showed >96% amino acid identity and similar gene order to the corresponding benzene degradation gene cluster described previously, providing further evidence for anaerobic benzene activation via carboxylation. For subsequent benzoyl-CoA dearomatization, bam-like genes analogous to the ones found in other strict anaerobes were transcribed, whereas gene transcripts involved in downstream benzoyl-CoA degradation were mostly analogous to the ones described in facultative anaerobes. The concurrent transcription of genes encoding enzymes involved in oxygenase-mediated aerobic benzene degradation suggested oxygen presence in the culture, possibly formed via a recently identified nitric oxide dismutase (Nod). Although we were unable to detect transcription of Nod-encoding genes, addition of nitrite and formate to the continuous culture showed indication for oxygen production. Such an oxygen production would enable aerobic microbes to thrive in oxygen-depleted and nitrate-containing subsurface environments contaminated with hydrocarbons.
Disaster risk, climate change, and poverty : assessing the global exposure of poor people to floods and droughts
People living in poverty are particularly vulnerable to shocks, including those caused by natural disasters such as floods and droughts. Previous studies in local contexts have shown that poor people are also often overrepresented in hazardprone areas. However, systematic evidence across countries demonstrating this finding is lacking. This paper analyzes at the country level whether poor people are disproportionally exposed to floods and droughts, and how this exposure may change in a future climate. To this end, household survey data with spatial identifiers from 52 countries are combined with present-day and future flood and drought hazard maps. The paper defines and calculates a “poverty exposure bias” and finds support that poor people are often overexposed to droughts and urban floods. For floods, no such signal is found for rural households, suggesting that different mechanisms -such as land scarcity- are more important drivers in urban areas. The poverty exposure bias does not change significantly under future climate scenarios, although the absolute number of people potentially exposed to floods or droughts can increase or decrease significantly, depending on the scenario and the region. The study finds some evidence of regional patterns: in particular, many countries in Africa exhibit a positive poverty exposure bias for floods and droughts. For these hot spots, implementing risk-sensitive land-use and development policies that protect poor people should be a priority.
Towards impact-based flood forecasting and warning in Bangladesh : a case study at the local level in Sirajganj district
Impact-based forecasting and warning services aim to bridge the gap between producers and users of warning information by connecting and increasing synergies between the components of effective early warning systems. We tested qualitatively whether a warning message based on colour codes is understandable and useful to trigger risk mitigation actions at the local level in the flood-exposed communities of Rajapur and Ghorjan unions in Sirajganj district, Bangladesh. With a community-based approach for different groups of users (i.e. sectors), flood-impact scenarios were determined from past events and related to colour codes. These were developed into impact-based forecasting and warnings that can connect water levels, through the colour code, to localised guidance information tailored to sectors’ needs on how to respond to the expected flood. This approach was tested through a limited number of focus group discussions and interviews at the community level. Overall, the colour coded impact-based warnings were found to be an easy and understandable way to link water level forecasts to the necessary risk mitigation actions, however, further investigation is needed to validate these findings under real-time conditions. IBFW has huge potential in Bangladesh but its integration requires significant institutional changes, such as an inter-facing agency (long term) or team (short term), adjusted policy frameworks (standing orders on disasters), and new resource allocations for skills development and technological innovation from national to local levels. Overall, this paper aims to offer a first insight into impact-based forecasting and warning services in Bangladesh to trigger further research and project developments.
Advancing the use of passive sampling in risk assessment and management of sediments contaminated with hydrophobic organic chemicals : results of an international ex situ passive sampling interlaboratory comparison
This work presents the results of an international interlaboratory comparison on ex situ passive sampling in sediments. The main objectives were to map the state of the science in passively sampling sediments, identify sources of variability, provide recommendations and practical guidance for standardized passive sampling, and advance the use of passive sampling in regulatory decision making by increasing confidence in the use of the technique. The study was performed by a consortium of 11 laboratories and included experiments with 14 passive sampling formats on 3 sediments for 25 target chemicals (PAHs and PCBs). The resulting overall interlaboratory variability was large (a factor of ~10), but standardization of methods halved this variability. The remaining variability was primarily due to factors not related to passive sampling itself, i.e., sediment heterogeneity and analytical chemistry. Excluding the latter source of variability, by performing all analyses in one laboratory, showed that passive sampling results can have a high precision and a very low intermethod variability (
Disaster risk, climate change, and poverty : assessing the global exposure of poor people to floods and droughts
People living in poverty are particularly vulnerable to shocks, including those caused by natural disasters such as floods and droughts. This paper analyses household survey data and hydrological riverine flood and drought data for 52 countries to find out whether poor people are disproportionally exposed to floods and droughts, and how this exposure may change in a future climate.Wefind that poor people are often disproportionally exposed to droughts and floods, particularly in urban areas. This pattern does not change significantly under future climate scenarios, although the absolute number of people potentially exposed to floods or droughts can increase or decrease significantly, depending on the scenario and region. In particular, many countries in Africa show a disproportionally high exposure of poor people to floods and droughts. For these hotspots, implementing risk-sensitive land-use and development policies that protect poor people should be a priority.
Modeling the effect of wave-vegetation interaction on wave setup
Aquatic vegetation in the coastal zone attenuates wave energy and reduces the risk of coastalhazards, e.g. flooding. Besides the attenuation of sea-swell waves, vegetation may also affectinfragravity-band (IG) waves and wave setup. To date, knowledge on the effect of vegetationon IG waves and wave setup is lacking, while they are potentially important parameters forcoastal risk assessment. In this study, the storm impact model XBeach is extended withformulations for attenuation of sea-swell and IG waves, and wave setup effects in two modes:the sea-swell wave phase-resolving (non-hydrostatic) and the phase-averaged (surfbeat) mode.In surfbeat mode a wave shape model is implemented to capture the effect of nonlinear wavevegetationinteraction processes on wave setup. Both modeling modes are verified using datafrom two flume experiments with mimic vegetation and show good skill in computing thesea-swell and IG wave transformation, and wave setup. In surfbeat mode, the wave setupprediction greatly improves when using the wave shape model, while in non-hydrostaticmode (nonlinear) intra-wave effects are directly accounted for. Subsequently, the model isused for a range of coastal geomorphological configurations by varying bed slope andvegetation extent. The results indicate that the effect of wave-vegetation interaction on wavesetup may be relevant for a range of typical coastal geomorphological configurations (e.g.relatively steep to gentle slope coasts fronted by vegetation).
Simulation of levee breach using Delft models : a case study of the Drava River flood event
This paper focuses on the modelling of a real-world flood event and levee breach by using Delft3D model and a newly developed Delft-Flexible Mesh (Delft3D-FM) model coupled with feedback control module. The study area is located at the bordering section of the River Drava between Slovenia and Croatia around the Hydro Power Plant Formin. The major flood event on the River Drava in November 2012 caused significant damages in Slovenia and Croatia.
Impact of water resources development on water availability for hydropower production and irrigated agriculture of the Eastern Nile Basin
The Eastern Nile riparian countries are currently developing several reservoir projects to contribute to the needs for energy and food production in the region. In the absence of formal mechanisms for collaboration, the transboundary nature of the Eastern Nile basin makes water resources development challenging. The large seasonal and interannual variability of the river flow increases those challenges. This paper assesses the implications of water resources development in the Eastern Nile basin on water availability for hydropower generation and irrigation demands at country and regional levels, using simulation and scenario analysis methods.
Flow slides : understanding their geo-mechanical mechanisms, the threats they pose and how these threats can be managed
Distinct patterns of interaction between vegetation and morphodynamics
Dynamic interaction between river morphodynamics and vegetation affects river channel patterns and populations of riparian species. A range of numerical models exists to investigate the interaction between vegetation and morphodynamics. However, many of these models oversimplify either the morphodynamics or the vegetation dynamics, which hampers the development of predictive models for river management. We have developed a model coupling advanced morphodynamics and dynamic vegetation, which is innovative because it includes dynamic ecological processes and progressing vegetation characteristics as opposed to commonly used static vegetation without growth and mortality. Our objective is to understand and quantify the effects of vegetation-type dependent settling, growth and mortality on the river pattern and morphodynamics of a meandering river. We compared several dynamic vegetation scenarios with different functional trait sets to reference scenarios without vegetation and with static vegetation without growth and mortality. We find distinct differences in morphodynamics and river morphology. The default dynamic vegetation scenario, based on two Salicaceae species, shows an active meandering behaviour, while the static vegetation scenario develops into a static, vegetation-dominated state. The diverse vegetation patterns in the dynamic scenario reduce lateral migration, increase meander migration rate and create a smoother floodplain compared to the static scenario. Dynamic vegetation results in typical vegetation patterns, vegetation age distribution and river patterns as observed in the field.