Zhao L.,CAS Research Center for Eco Environmental Sciences |
Zhao L.,Institute for Environmental science |
Zhang X.,Peking University |
Liu Y.,Peking University |
And 4 more authors.
Journal of Environmental Sciences (China) | Year: 2012
Lake Fuxian is the largest deep freshwater lake in China. Although its average water quality meets Class I of the China National Water Quality Standard (CNWQS), i.e., GB3838-2002, monitoring data indicate that the water quality approaches the Class II threshold in some areas. Thus it is urgent to reduce the watershed load through the total maximum daily load (TMDL) program. A three-dimensional hydrodynamic and water quality model was developed for Lake Fuxian, simulating flow circulation and pollutant fate and transport. The model development process consists of several steps, including grid generation, initial and boundary condition configurations, and model calibration processes. The model accurately reproduced the observed water surface elevation, spatiotemporal variations in temperature, and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) concentrations, suggesting a reasonable numerical representation of the prototype system for further TMDL analyses. The TMDL was calculated using two interpretations of the water quality standards for Class I of the CNWQS based on the maximum instantaneous surface and annual average surface water concentrations. Analysis of the first scenario indicated that the TN, TP and COD loads should be reduced by 66%, 68% and 57%, respectively. Water quality was the highest priority; however, local economic development and cost feasibility for load reduction can pose significant issues. In the second interpretation, the model results showed that, under the existing conditions, the average water quality meets the Class I standard and therefore load reduction is unnecessary. Future studies are needed to conduct risk and cost assessments for realistic decision-making. © 2012 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.
Lacroix P.,University of Geneva |
De Roulet P.,Geneva International Center for Humanitarian Demining |
Ray N.,Institute for Environmental science
International Journal of Applied Geospatial Research | Year: 2014
This paper presents START (Simplified Toolbar to Accelerate Repeated Tasks), a new, freely downloadable ArcGIS extension designed for non-expert GIS users. START was developed jointly by the Geneva International Centre for Humanitarian Demining (GICHD) and the University of Geneva to support frequent workflows relating to mine action. START brings together a series of basic ArcGIS tools in one toolbar and provides new geoprocessing, geometry and database management functions. The toolbar operates as a bridge between non-spatial repositories (e.g. MySQL and Excel) and GIS. It also connects mine action professionals recording data in the field to GIS experts and improves data interoperability between GIS professionals working in different disciplines. Originally created to help humanitarian demining actors optimize GIS workflows and be more efficient in their everyday work, the toolbar might also benefit scientists operating in other fields. Copyright © 2014, IGI Global.
Yamamoto Y.,Tohoku University |
Usuda N.,Fujita Health University |
Oghiso Y.,Institute for Environmental science |
Kuwahara Y.,Tohoku University |
Fukumoto M.,Tohoku University
Health Physics | Year: 2010
Irradiation from internally deposited radionuclides induces malignant tumors. Ingested radionuclides accumulate in specific organs, which are irradiated over a lifelong period. Our aim is to elucidate why the development of malignant tumors requires long-term internal exposure, on the order of decades, despite the fact that irradiation is continuous over this period. Three major factors are considered to be responsible for the long incubation time in carcinogenesis caused by internally deposited alpha-emitters: uneven distribution of radionuclides, limited range of irradiation, and dynamic movement of tumor precursor cells. We hypothesized that target cells susceptible to malignant transformation may undergo one event by alpha particles and may then migrate outside of the range of alpha particles, thereby avoiding immediate induction of successive additional events that would lead to cell death or neoplastic changes. Based on this hypothesis, we further proposed a mathematical model to predict the relationship between dose rate and incubation period of tumors induced by internally deposited alpha-emitters. The function was non-linear and included terms of both direct and indirect radiation effects. It well fitted both human Th-ICC cases and rat Pu-induced lung cancer, suggesting that indirect radiation effects are independent from dose rate. The significance of parameters of the model is discussed. Copyright © 2010 Health Physics Society.
van den Heuvel F.,University of Geneva |
Goyette S.,Institute for Environmental science |
Rahman K.,University of Geneva |
Stoffel M.,Institute for Environmental science |
And 2 more authors.
Geomorphology | Year: 2016
The principal objective of this study was to investigate the types of large-scale meteorological situations that are conducive to the precipitation and temperature conditions most likely to trigger debris flows in the Zermatt valley, Switzerland, under current and future climates. A two-dimensional Bayesian probability calculation was applied to take account of uncertainties in debris-flow triggering. Precipitation quantities exceeding the 95th percentile of daily precipitation amounts were found to have a significantly higher probability to coincide with observed debris flows. A different relationship exists for extreme temperatures, however. Southerly air flows, weak horizontal pressure gradients over Europe, and westerly flows are mostly associated with observed debris flows and 95th precipitation percentile exceedances. These principal flow directions are well represented in the regional climate model (RCM) HIRHAM control simulations for events exceeding the 95th precipitation percentile and the 30th temperature percentile. Under the IPCC A2 emission scenario, westerly and southerly flows are mostly responsible for these precipitation and temperature conditions under the hypothesis of slow adaptation to climate change (HS1/HC1). Under the hypothesis of rapid adaptation to climate change (HS1/HS1), southerly flows and weak horizontal pressure gradients are likely to gain in importance. In both scenarios for the future, southeasterly flows are among the principal flow directions responsible for the joint exceedance of the 95th precipitation percentile and the 30th temperature percentile, while these were absent in observations and the control simulation. © 2015 Elsevier B.V.
Noss C.,Institute for Environmental science |
Lorke A.,Institute for Environmental science
Water Resources Research | Year: 2016
Although relationships between roughness, flow, and transport processes in rivers and streams have been investigated for several decades, the prediction of flow resistance and longitudinal dispersion in small streams is still challenging. Major uncertainties in existing approaches for quantifying flow resistance and longitudinal dispersion at the reach scale arise from limitations in the characterization of riverbed roughness. In this study, we characterized the riverbed roughness in small moderate-gradient streams (0.1-0.5% bed slope) and investigated its effects on flow resistance and dispersion. We analyzed high-resolution transect-based measurements of stream depth and width, which resolved the complete roughness spectrum with scales ranging from the micro to the reach scale. Independently measured flow resistance and dispersion coefficients were mainly affected by roughness at spatial scales between the median grain size and the stream width, i.e., by roughness between the micro- and the mesoscale. We also compared our flow resistance measurements with calculations using various flow resistance equations. Flow resistance in our study streams was well approximated by the equations that were developed for high gradient streams (>1%) and it was overestimated by approaches developed for sand-bed streams with a smooth riverbed or ripple bed. © 2016. American Geophysical Union.
Jager A.,University of Leipzig |
Bertmer M.,University of Leipzig |
Schaumann G.E.,Institute for Environmental science
Geoderma | Year: 2016
The impact of low water contents on the molecular mobility of soil organic matter (SOM) and its most frequent components was investigated. Combined 1H, 2H, and 13C solid-state nuclear magnetic resonance (NMR) techniques allow for an advanced insight into mechanisms of water uptake under defined atmospheres and its effect on SOM segment mobility. The major individual organic components of two peats, a gleyic podsol and a number of model substances (cutin, suberin, wood and cellulose) were distinguished with respect to their contribution to the 1H and 13C NMR spectra. Water molecules and mobile polymer constituents of SOM contribute to the mobile fraction in 1H NMR wide line spectra. Poly(methylene), being most probably part of amphiphilic molecules, have been identified as SOM components that are mobilized in the presence of water. Even though being of hydrophobic nature, water acts as a plasticizer on such long chain aliphatic soil components. Differential scanning calorimetry measurements of SOM samples support this insight in terms of a thermal step transition. Based on our findings, comparison of experimental results from different soils with varying water contents and soil composition should consider mobility effects of both, aliphatic moieties as well as polar moieties of SOM. © 2016 Elsevier B.V.
Edvardsson J.,University of Bern |
Simanauskiene R.,Vilnius University |
Taminskas J.,Nature Research Center |
Bauziene I.,Nature Research Center |
And 2 more authors.
Science of the Total Environment | Year: 2015
Over the past century an ongoing establishment of Scots pine (Pinus sylvestris L.), sometimes at accelerating rates, is noted at three studied Lithuanian peat bogs, namely Kere˙plis, Re˙kyva and Aukštumala, all representing different degrees of tree coverage and geographic settings. Present establishment rates seem to depend on tree density on the bog surface and are most significant at sparsely covered sites where about three-fourth of the trees have established since the mid-1990s, whereas the initial establishment in general was during the early to mid-19th century. Three methods were used to detect, compare and describe tree establishment: (1) tree counts in small plots, (2) dendrochronological dating of bog pine trees, and (3) interpretation of aerial photographs and historical maps of the study areas. In combination, the different approaches provide complimentary information but also weigh up each other's drawbacks. Tree counts in plots provided a reasonable overview of age class distributions and enabled capturing of the most recently established trees with ages less than 50. years. The dendrochronological analysis yielded accurate tree ages and a good temporal resolution of long-term changes. Tree establishment and spread interpreted from aerial photographs and historical maps provided a good overview of tree spread and total affected area. It also helped to verify the results obtained with the other methods and an upscaling of findings to the entire peat bogs. The ongoing spread of trees in predominantly undisturbed peat bogs is related to warmer and/or drier climatic conditions, and to a minor degree to land-use changes. Our results therefore provide valuable insights into vegetation changes in peat bogs, also with respect to bog response to ongoing and future climatic changes. © 2014 Elsevier B.V..
PubMed | Institute for Environmental science
Type: Journal Article | Journal: Analytical sciences : the international journal of the Japan Society for Analytical Chemistry | Year: 2016
We developed a rapid, simple method for the iodine speciation analysis of water and applied it to natural water samples. Simultaneous determinations of I(-) and IO3(-) were achieved with an HPLC system with amperometric detection for I(-) and spectrophotometric detection after a postcolumn reaction for IO3(-). We determined the I(-) and IO3(-) concentrations in 20-L water samples within 10 min. Total I concentrations in water samples were determined after the decomposition of organics by off-line UV irradiation for 30 min, followed by reduction to I(-). The analytical conditions were optimized by using test solutions rich in organic matter extracted from soils. We tested the new method with samples of groundwater, spring water, precipitation, soil percolate, stream water, and seawater as well as solutions extracted from soil. The method worked well, although the concentrations of some I species were below detection. This method is suitable for routine speciation analysis, which is important for studies of I behavior in the environment.