Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2020

Abstract

Land-sea riverine carbon transfer (LSRCT) is one of the key processes in the global carbon cycle. Although natural factors (e.g. climate, soil) influence LSRCT, human water management strategies have also been identified as a critical component. However, few systematic approaches quantifying the contribution of coupled natural and anthropogenic factors on LSRCT have been published. This study presents an integrated framework coupling hydrological modeling, field sampling and stable isotope analysis for the quantitative assessment of the impact of human water management practices (e.g. irrigation, dam construction) on LSRCT under different hydrological conditions. By applying this approach to the case study of the Nandu River, China, we find that carbon (C) concentrations originating from different land-uses (e.g. forest, cropland) are relatively stable and outlet C variations are mainly dominated by controlled runoff volumes rather than by input C concentrations. These results indicate that human water management practices are responsible for a reduction of ∼60% of riverine C at seasonal timescales, with an even greater reduction during drought conditions. Annual C discharges have been significantly reduced (e.g. 77 ± 5% in 2015 and 39 ± 11% in 2016) due to changes in human water extraction coupled with climate variation. In addition, isotope analysis also shows that C fluxes influenced by human activities (e.g. agriculture, aquaculture) could contribute the dominant particulate organic carbon under typical climatic conditions, as well as drought conditions. This research demonstrates the substantial effect that human water management practices have on the seasonal and annual fluxes of LSRCT, especially in such small basins. This work also shows the applicability of this integrated approach, using multiple tools to quantify the contribution of coupled anthropogenic and natural factors on LSRCT, and the general framework is believed to be feasible with limited modifications for larger basins in future research.

Abstract

Remediation using nanoparticles depends on proper documentation of safety aspects, one of which is their ecotoxicology. Ecotoxicology of nanoparticles has some special features: while traditional ecotoxicology aims at measuring possible negative effects of more or less soluble chemicals or dissolved elements, nanoecotoxicology aims at measuring the toxicity of particles, and its main focus is on effects that are unique to nano-sized particles, as compared to larger particles or solutes. One of the main challenges when testing the ecotoxicity of nanoparticles lies in maintaining stable and reproducible exposure conditions, and adapt these to selected test organisms and endpoints. Another challenge is to use test media that are relevant to the matrices to be treated. Testing of nanoparticles used for remediation, particularly red-ox-active Fe-based nanoparticles, should also make sure to exclude confounding effects of altered red-ox potential which are not nanoparticle-specific. Yet another unique aspect of nanoparticles used for remediation is considerations of ageing of nanoparticles in soil or water, leading to reduced toxicity over field-relevant time scales. This review discusses these and other aspects of how to design and interpret appropriate tests and use these in hazard descriptions for subsequent risk assessments.

2019

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Abstract

The notion of the Anthropocene does not fit well into the frame of scientific disciplines. The proposed onset of a new geological epoch has become closely linked with human history and with notions such as purposeful human actions. Purposefulness, however, is also subject to interpretation in the humanities and does not fit into analytical methods in Earth sciences. Scholars have taken up this challenge and engage with Earth scientists in public discourse on the Anthropocene. Due to the lack of a common frame of reference, discussions suffer from incompatible abstractions, notions, methods and results. Here, we propose an abstract model-framework facilitating communication between Earth scientists and scholars. In Earth sciences, models are often employed to provide a representation of an independent reality which imposes limits to growth. In the humanities, self-reference and reflexivity of modernity at all scales including the globe becomes a key issue. In the former view models can be decomposed and locally tested, in the latter models and concepts involving human action need to be considered in all their contextual and semantic relations. Typically, such concepts, for example in anthropology, do not come in a mathematical language. Nevertheless, we suggest that a common reference can be sought in an abstract model language, rather than in realistic models. Category theory and formal notions developed in computer science may provide such an abstract framework to accommodate the apparently incompatible views of models and concepts, which are considered as successful by their respective home disciplines. Diverse models such as examples from game theory (economics), from dynamic system theory (Earth science) and from a classification of ethnocosmologies (anthropology) can be formulated as different instances within a joint and abstract framework. Such a framework allows to investigate implications of the Anthropocene for logical similarities with past environmental events by seeking historical analogies (for example with the great oxygenation event) or formulating consistency requirements for the future (for example by defining sustainability). The prize for the common basis is a strict ‘epistemic hygiene’, avoiding most ontological assumptions and criticisms which often appear as dear to Earth scientists and scholars, but which may prevent a more fruitful exchange on an urgent interdisciplinary topic

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Abstract

Seasonal variations in wood supply are linked to the regional operating environment. This study constitutes the Norwegian contribution to Era-Net MultiStrat (Multimodal strategies for more resilient wood supply) covering oceanic, sub-arctic and continental climate zones. The oceanic zone is characterized by considerable seasonal variation in both temperature and precipitation. The goal of the study was to seek solutions for more resilient wood supply under these conditions. The study started with a general mapping of wood supply management processes including common demand and supply risks (WP1). The work continued with analysis of three years of production and transport reports (2014-2016) with tracking of roadside stocks and transport lead times (WP2). Daily temperature, precipitation, and snowpack were tracked with data from 65 surrounding weather stations. A simple multimodal transport problem with a rolling selection of planning horizons was then used to find the efficient multimodal solutions for the core, adjacent and peripheral supply regions through 12 balance periods per year (WP3). The transport analysis covers 65 supply districts feeding 6 assortment groups to 10 mills via 11 shipping terminals. The transport analysis varied both vessel cargo capacity and cargo collection practices. The results demonstrated a wide range of solutions to ensure roundwood availability with limited increases in system costs. While the transport analysis demonstrated the contribution of the multimodal solutions to structural flexibility, it also revealed a bottleneck for resilience of the wood supply system; seasonal variation in truck transport output (m3km/week). The geographical distribution of seasonality showed the main source to be one particular supply region. A subsequent wood supply planning workshop with production managers indicated that a bottleneck for improved production planning was short wood purchase and planning horizons. A simple optimization experiment was therefore set up to quantify the feasibility of more specific site-type selection according to actual soil and seasonal weather conditions for the selected region. On-line grid-based groundwater modeling was used to monitor weekly geographical variations in bearing capacity and the experiment provided a plausible re-scheduling of flows to reduce variation in delivery volumes and transport output.

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Abstract

Preferential flow may become significant in partially frozen soils because infiltration can occur through large, initially air-filled pores surrounded by a soil matrix with limited infiltration capacity. The objectives of this study were to develop and evaluate a dual-permeability approach for simulating water flow and heat transport in macroporous soils undergoing freezing and thawing. This was achieved by introducing physically based equations for soil freezing and thawing into the dual-permeability model MACRO. Richards’ equation and the heat flow equation were loosely coupled using the generalized Clapeyron equation for the soil micropore domain. Freezing and thawing of macropore water is governed by a first-order equation for energy transfer between the micropore and macropore domains. We assumed that macropore water was unaffected by capillary forces, so that water in macropores freezes at 0°C. The performance of the model was evaluated for four test cases: (i) redistribution of water in the micropore domain during freezing, (ii) a comparison between the first-order energy transfer approach and the heat conduction equation, (iii) infiltration and water flow in frozen soil with an initially air-filled macropore domain, and (iv) thawing from the soil surface during constant-rate rainfall. Results show that the model behaves in accordance with the current understanding of water flow and heat transport in frozen macroporous soil. To improve modeling of water and heat flow in frozen soils, attention should now be focused on providing experimental data suitable for evaluating models that account for macropore flow.

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Abstract

Synthetic Aperture Radar (SAR) data have gained interest for a variety of remote sensing applications, given the capability of SAR sensors to operate independent of solar radiation and day/night conditions. However, the radiometric quality of SAR images is hindered by speckle noise, which affects further image processing and interpretation. As such, speckle reduction is a crucial pre-processing step in many remote sensing studies based on SAR imagery. This study proposes a new adaptive de-speckling method based on a Gaussian Markov Random Field (GMRF) model. The proposed method integrates both pixel-wised and contextual information using a weighted summation technique. As a by-product of the proposed method, a de-speckled pseudo-span image, which is obtained from the least-squares analysis of the de-speckled multi-polarization channels, is also produced. Experimental results from the medium resolution, fully polarimetric L-band ALOS PALSAR data demonstrate the effectiveness of the proposed algorithm compared to other well-known de-speckling approaches. The de-speckled images produced by the proposed method maintainthe mean value of the original image in homogenous areas, while preserving the edges of features in heterogeneous regions. In particular, the equivalent number of look (ENL) achieved using the proposed method improves by about 15% and 47% compared to the NL-SAR and SARBM3D de-speckling approaches, respectively. Other evaluation indices, such as the mean and variance of the ratio image also reveal the superiority of the proposed method relative to other de-speckling approaches examined in this study.