Epiphytic diatoms as flood indicators   总被引：1，自引：0，他引：1  

Johan A. Wiklund  Natalie Bozinovski  Roland I. Hall  Brent B. Wolfe 《Journal of Paleolimnology》2010,44(1):25-42

The hydroecology of floodplain lakes is strongly regulated by flood events. The threat of climate warming and increasing human activities requires development of scientific methods to quantify changes in the frequency of short-lived flood events, because they remain difficult to identify using conventional paleolimnological and monitoring approaches. We developed an approach to detect floods in sediment records by comparing the abundance and composition of epiphytic diatom communities in flooded and non-flooded ponds of the Peace-Athabasca Delta (PAD), Canada, that grew on submerged macrophytes (Potamogeton zosteriformis, P. perfoliatus) and an artificial substrate (polypropylene sheets) during the open-water season of 2005. Analysis of similarity tests showed that epiphytic diatom community composition differs significantly between flooded and non-flooded ponds. After accounting for the “pond effect,” paired comparisons of the three substrates determined that variation in community composition between the artificial substrate and macrophytes was similar to that between the macrophyte taxa. Similarity percentage analysis identified diatom taxa that discriminate between flooded and non-flooded ponds. The relative abundance of ‘strong flood indicator taxa’ was used to construct an event-scale flood record spanning the past 180 years using analyses of sedimentary diatom assemblages from a closed-drainage pond (PAD 5). Results were verified by close agreement with an independent paleoflood record from a nearby flood-prone oxbow pond (PAD 54) and historical records. Comparison of epiphytic diatoms in flooded and non-flooded lakes in this study provides a promising approach to detect changes in flood frequency, and may have applications for reconstructing other pulse-type disturbances such as hurricanes and pollutant spills.  相似文献   

Industrial Land Development and Manufacturing Deconcentration in Greater Jakarta     

Delik Hudalah  Dimitra Viantari  Tommy Firman  Johan Woltjer 《Urban geography》2013,34(7):950-971

Abstract

Industrial land development has become a key feature of urbanization in Greater Jakarta, one of the largest metropolitan areas in Southeast Asia. Following Suharto's market-oriented policy measures in the late 1980s, private developers have dominated the land development projects in Greater Jakarta. The article investigates the extent to which these private industrial centers have effectively reduced the domination of Jakarta in shaping the entire metropolitan structure. The analysis indicates that major suburban industrial centers have captured most of the manufacturing employment that has dispersed from Jakarta. The industrial centers have now increasingly specialized and diversified. It is likely that a polycentric metropolitan structure will emerge in the future.  相似文献   

Erodibility of soft freshwater sediments in Markermeer: the role of bioturbation by meiobenthic fauna     

Miguel Angel de Lucas Pardo  Marieke Bakker  Thijs van Kessel  Francesco Cozzoli  Johan Christian Winterwerp 《Ocean Dynamics》2013,63(9-10):1137-1150

The Markermeer is a large and shallow man-made freshwater lake in the Netherlands, characterized by its high turbidity. As part of a study aiming to mitigate this high turbidity, we studied the water–bed exchange processes of the lake’s muddy bed. The upper centimeter’s–decimeter’s of the lake bed sediments mainly consists of soft anoxic mud. Recent measurements have proved the existence of a thin oxic layer on top of this soft anoxic mud. This oxic layer, which is much easier to be eroded than the anoxic mud, is believed to be related with Markermeer’s high-turbidity levels. Our hypothesis is that the thin oxic layer develops from the anoxic mud, enhanced by bioturbation. Actually, we will demonstrate that it is the bioturbated state of the bed that increases its erodability, and not the oxidation state of the sediments. In particular, we will refer to bioturbation caused by meiobenthic fauna. The objective of this study is therefore to determine the influence of the development of the thin oxic layer on the water–bed exchange processes, as well as to establish the role of bioturbation on those processes. This is done by quantifying the erosion rate as a function of bed shear stresses, and at different stages of the development of the oxic layer. Our experiments show that bioturbation increases the rate at which Markermeer sediments are eroded by almost an order of magnitude. The short-term fine sediment dynamics in Markermeer are found to be driven by the complex and highly dynamic interactions between physics, chemistry, and biology. Finally, the long-term fine sediment dynamics are driven by the erosion of the historical deposits in the lake’s bed, which is only possible after bioturbation, and which leads to an increase of the stock of sediments in the lake’s muddy bed.  相似文献   

Coastal flood risks and seasonal tourism: analysing the effects of tourism dynamics on casualty calculations   总被引：1，自引：1，他引：0  

Wim Kellens  Tijs Neutens  Pieter Deckers  Johan Reyns  Philippe De Maeyer 《Natural Hazards》2012,60(3):1211-1229

Since coastal tourism is one of the fastest growing sectors of tourism industry, coastal areas have become increasingly vulnerable in the case of flooding. While in recent years a number of different methods have been put forward to map coastal flood risks, the implications of tourism dynamics for the assessment of human casualties has remained largely overlooked in these models. This chapter examines to what extent the ignorance of (residential) coastal tourism may bias the calculations of human casualties. To this end, a case study has been conducted on the Belgian coast. Both the dynamic nature of coastal tourism and the behaviour of residential tourists in storm surge scenarios are considered. The results of this study show that including tourism dynamics in flood risk management is justified and appropriate, depending on the tourist attractiveness of the flood-prone area and its temporal fluctuations.  相似文献   

It starts at home? Climate policies targeting household consumption and behavioral decisions are key to low-carbon futures     

Ghislain Dubois  Benjamin Sovacool  Carlo Aall  Maria Nilsson  Carine Barbier  Alina Herrmann  Sébastien Bruyère  Camilla Andersson  Bore Skold  Franck Nadaud  Florian Dorner  Karen Richardsen Moberg  Jean Paul Ceron  Helen Fischer  Dorothee Amelung  Marta Baltruszewicz  Jeremy Fischer  Françoise Benevise  Valérie R. Louis  Rainer Sauerborn 《Chemie der Erde / Geochemistry》2012

Through their consumption behavior, households are responsible for 72% of global greenhouse gas emissions. Thus, they are key actors in reaching the 1.5 °C goal under the Paris Agreement. However, the possible contribution and position of households in climate policies is neither well understood, nor do households receive sufficiently high priority in current climate policy strategies. This paper investigates how behavioral change can achieve a substantial reduction in greenhouse gas emissions in European high-income countries. It uses theoretical thinking and some core results from the HOPE research project, which investigated household preferences for reducing emissions in four European cities in France, Germany, Norway and Sweden. The paper makes five major points: First, car and plane mobility, meat and dairy consumption, as well as heating are the most dominant components of household footprints. Second, household living situations (demographics, size of home) greatly influence the household potential to reduce their footprint, even more than country or city location. Third, household decisions can be sequential and temporally dynamic, shifting through different phases such as childhood, adulthood, and illness. Fourth, short term voluntary efforts will not be sufficient by themselves to reach the drastic reductions needed to achieve the 1.5 °C goal; instead, households need a regulatory framework supporting their behavioral changes. Fifth, there is a mismatch between the roles and responsibilities conveyed by current climate policies and household perceptions of responsibility. We then conclude with further recommendations for research and policy.  相似文献   

Trace metal assessment in soils in a small city and its rural surroundings,Pensacola, FL,USA     

Johan Liebens  Carl J. Mohrherr  K. Ranga Rao 《Environmental Earth Sciences》2012,65(6):1781-1793

This study assesses the origin and pollution of trace metals in surface soils in a region with contrasting land uses (urban vs. rural). Principal component analysis (PCA) reveals that Cr and Ni are predominantly of geogenic origin. These two trace metals are also the only ones with statistically significant correlations with soil particle size and organic matter content. Copper, Pb and Zn, and possibly Hg, are of anthropogenic origin, but their concentrations rarely reach levels described as strongly polluted by pollution indexes. The concentrations of these anthropogenic trace metals are statistically not different in urban and rural areas, except for Pb that is higher in the urban area. This general lack of a difference between the two land uses indicates that the influence of this small urban area on trace metal concentrations in soils is minor. Lead and Zn have the most, but still a modest number, of strongly polluted sites, mainly in an industrial part of the city. GIS analysis shows that, based on the pollution load index (PLI), overall concentrations of trace metals also reach their highest levels in that industrial area. These observations indicate that the influence of industry on trace metal pollution in soil exceeds that of other urban activities in the region. Local background concentrations were found to be very different from general crustal background concentrations. This demonstrates the importance of the careful selection of a background type in studies like this.  相似文献   

Universal time from VLBI single-baseline observations during CONT08   总被引：2，自引：2，他引：0  

Tobias Nilsson  Johannes Böhm  Harald Schuh 《Journal of Geodesy》2011,85(7):415-423

The IVS Intensive sessions are single-baseline, 1-h VLBI sessions carried out everyday in order to determine Universal Time (UT1). We investigate different possibilities to improve the results of such sessions. We do this investigation by extracting 2-h single-baseline sessions from the CONT08 data set. These are analysed like normal Intensives, and the results are compared to the results of the analysis of the full CONT08 data set. We find that tropospheric asymmetry is the major error source for the single-baseline sessions. It is possible to improve the accuracy of the estimated UT1 either by using accurate a priori tropospheric gradients or by estimating gradients in the data analysis.  相似文献   

Rapid macrofaunal colonization of water-based drill cuttings on different sediments     

Trannum HC  Setvik S  Norling K  Nilsson HC 《Marine pollution bulletin》2011,62(10):2145-2156

A field experiment was conducted to investigate how water-based drill cuttings and sediment type influence colonization of soft bottom communities. Bottom frames with trays containing defaunated sediments were placed at the seabed for 6 months to study colonization of macrofauna. Two different sediments (coarse and fine) were used, and 6 or 24 mm layer of water-based drill cuttings were added on top of these sediments. Some of the sediments were controls with no additions. In the end of the experiment, the oxygen availability in sediment porewater and macrofaunal abundance were reduced in treatments with 24 mm drill cuttings compared to controls. Tube-building annelids were particularly sensitive to drill cuttings. However, these responses were only minor, and notably, the drill cuttings initiated a weaker faunal response than sediment type and site of the bottom frame. Sediments capped with water-based drill cuttings thus showed a rapid colonization of macrofaunal communities.  相似文献   

Rhizofiltration of a Heavy Metal (Lead) Containing Wastewater Using the Wetland Plant Carex pendula     

Brijesh K. Yadav  Maarten A. Siebel  Johan J. A. van Bruggen 《洁净——土壤、空气、水》2011,39(5):467-474

Rhizofiltration is a subset technique of phytoremediation which refers to the approach of using plant biomass for removing contaminants, primarily toxic metals, from polluted water. The effective implementation of this in situ remediation technology requires experimental as well as conceptual insight of plant–water interactions that control the extraction of targeted metal from polluted water resources. Therefore, pot and simulation experiments are used in this study to investigate the rhizofiltration of a lead containing wastewater using plants of Carex pendula, a common wetland plant found in Europe. The metal contaminant extraction along with plant growth and water uptake rates from a wastewater having varying Pb concentration is studied experimentally for 2 wk. The temporal distribution of the metal concentration in the wastewater and the accumulated metal in different compartments of C. pendula at the end are analyzed using atomic absorption spectrometry. Parameters of the metal uptake kinetics are deduced experimentally for predicting the metal removal by root biomass. Further, mass balance equations coupled with the characterized metal uptake kinetics are used for simulating the metal partitioning from the wastewater to its accumulation in the plant biomass. The simulated metal content in wastewater and plant biomass is compared with the observed data showing a good agreement with the later. Results show that C. pendula accumulates considerable amounts of lead, particularly in root biomass, and can be considered for the cleanup of lead contaminated wastewaters in combination with proper biomass disposal alternatives. Also, the findings can be used for performing further non‐hydroponics experiment to mimic the real wetland conditions more closely.  相似文献   

On the assessment of Argo float trajectory assimilation in the Mediterranean Forecasting System     

Jenny A. U. Nilsson  Srdjan Dobricic  Nadia Pinardi  Vincent Taillandier  Pierre-Marie Poulain 《Ocean Dynamics》2011,61(10):1475-1490

The Mediterranean Forecasting System (MFS) has been operational for a decade, and is continuously providing forecasts and analyses for the region. These forecasts comprise local- and basin-scale information of the environmental state of the sea and can be useful for tracking oil spills and supporting search-and-rescue missions. Data assimilation is a widely used method to improve the forecast skill of operational models and, in this study, the three-dimensional variational (OceanVar) scheme has been extended to include Argo float trajectories, with the objective of constraining and ameliorating the numerical output primarily in terms of the intermediate velocity fields at 350 m depth. When adding new datasets, it is furthermore crucial to ensure that the extended OceanVar scheme does not decrease the performance of the assimilation of other observations, e.g., sea-level anomalies, temperature, and salinity. Numerical experiments were undertaken for a 3-year period (2005–2007), and it was concluded that the Argo float trajectory assimilation improves the quality of the forecasted trajectories with ~15%, thus, increasing the realism of the model. Furthermore, the MFS proved to maintain the forecast quality of the sea-surface height and mass fields after the extended assimilation scheme had been introduced. A comparison between the modeled velocity fields and independent surface drifter observations suggested that assimilating trajectories at intermediate depth could yield improved forecasts of the upper ocean currents.  相似文献