2016 International Land Model Benchmarking (ILAMB) Workshop Report

As earth system models (ESMs) become increasingly complex, there is a growing need for comprehensive and multi-faceted evaluation of model projections. To advance understanding of terrestrial biogeochemical processes and their interactions with hydrology and climate under conditions of increasing atmospheric carbon dioxide, new analysis methods are required that use observations to constrain model predictions, inform model development, and identify needed measurements and field experiments. Better representations of biogeochemistryclimate feedbacks and ecosystem processes in these models are essential for reducing the acknowledged substantial uncertainties in 21st century climate change projections

Characteristics of Flow Movement in Complex Canal System and Its Influence on Sudden Pollution Accidents

This study aimed to determine the split ratio, flow-field structure, and effect of different shaped channels to sudden pollution accidents in a generalized complex canal system of a wetland park, both experimentally and numerically. The three-dimensional instantaneous velocities at a typical section of each channel in the generalized model were measured experimentally using an acoustic Doppler velocimeter. The results showed that the split ratio calculation formula of three parallel channels could be derived under the condition of considering the frictional head and the local head losses. The water depth, velocities, and pollutant diffusion were widely influenced by changes in the cross-sectional shape and channel plane shape. The pollutants were trapped by stable vortices and transverse circulation due to shear force and secondary flow, thus delaying the diffusion of pollutants. The research results reported herein can help provide technical support for the normal operation of complex canal systems

Validation of Noah-Simulated Soil Temperature in the North American Land Data Assimilation System Phase 2

Soil temperature can exhibit considerable memory from weather and climate signals and is among the most important initial conditions in numerical weather and climate models. Consequently, a more accurate long term land surface soil temperature dataset is needed to improve weather and climate simulation and prediction, and is also important for the simulation of agricultural crop yield and ecological processes. The North American Land Data Assimilation phase 2 (NLDAS-2) has generated 31 years (1979–2009) of simulated hourly soil temperature data with a spatial resolution of 1/8°. This dataset has not been comprehensively evaluated to date. Thus, the purpose of this paper is to assess Noah-simulated soil temperature for different soil depths and time scales. The authors used long-term (1979–2001) observed monthly mean soil temperatures from 137 cooperative stations over the United States to evaluate simulated soil temperature for three soil layers (0–10, 10–40, and 40–100 cm) for annual and monthly time scales. Short-term (1997–99) observed soil temperatures from 72 Oklahoma Mesonet stations were used to validate simulated soil temperatures for three soil layers and for daily and hourly time scales. The results showed that the Noah land surface model generally matches observed soil temperature well for different soil layers and time scales. At greater depths, the simulation skill (anomaly correlation) decreased for all time scales. The monthly mean diurnal cycle difference between simulated and observed soil temperature revealed large midnight biases in the cold season that are due to small downward long wave radiation and issues related to model parameters

Accurate Determination of Plutonium in Soil by Tandem Quadrupole ICP-MS with Different Sample Preparation Methods

In this work, three commonly used digestion techniques, such as acid leaching with 8 M HNO3, aqua regia and lithium metaborate fusion, were employed to extract Pu from different types of soil samples widely found across China, and to establish the influence of the major interference elements (U, Hg, Pb, Tl, and Bi) on the accurate measurement of Pu by tandem quadrupole ICP-MS. The three sample digestion techniques yielded good results for the analysis of Pu isotopes originating from global atmospheric fallout. The U and Pb contributions to m/z=239 (2.38 and 0.3 cps) in samples digested by the fusion method using AGMP-1M resin were higher than those digested by the acid leaching methods (0.55 cps for U and < 0.03 cps for Pb), which implies that additional purification with TEVA resin would be required for low-level Pu determination in soil samples. By taking advantage of tandem quadrupole ICP-MS in the NH3/He mode, the count rates of Hg, Tl and Bi at m/z=239 (<0.01 cps) in the samples purified by using AGMP-1M resin and/or TEVA resin were found to be negligible for the different sample digestion methods

Concrete Elastic Modulus Experimental Research Based on Theory of Capillary Tension

The risk of cracking in the early stage is a critical indicator of the performance of concrete structures. Concrete cracked when the tensile stresses caused by deformation under restraint conditions exceeded its tensile strength. This research aims at an accurate prediction of shrinkage cracking of concrete under constraints. Based on the theory of capillary tension under the concrete shrinkage mechanism, the method to test and compute the elastic modulus of a micro-matrix around the capillary, Et, was derived. Shrinkage and porosity determination tests were conducted to obtain the shrinkage values and confining stresses of concrete at different strength grades, different ages and under different restraint conditions, accordingly. Meanwhile, the proposed method of this research was used to obtain Et. The restraint stress given by Et was compared with the experimental result under the corresponding time. The results suggested a positive correlation between the elastic modulus of a micro-matrix around the capillary, Et, precomputed by the theory, and the static elastic modulus, Ec, and that the ratio between the two gradually decreased with the passage of time, which ranged from 2.8 to 3.1

Speciation Analysis of ¹²⁹I in Seawater by Carrier-Free AgI–AgCl Coprecipitation and Accelerator Mass Spectrometric Measurement

A rapid and simple method was developed for speciation analysis of ¹²⁹I in seawater by selective coprecipitation of carrier-free iodide and accelerator mass spectrometry (AMS) measurement of ¹²⁹I. Iodide was separated from seawater and other species of iodine by coprecipitation of AgI with Ag₂SO₃, AgCl, and AgBr by addition of only 100 mg/L Ag⁺ and 0.3 mmol/L NaHSO₃ at pH 4.2–5.5. The separation efficiency of iodide was more than 95%, and crossover between ¹²⁹IO₃^– and ¹²⁹I^– fractions is less than 3%. Iodate and total inorganic iodine were converted to iodide by use of NaHSO₃ at pH 1–2 and then separated by the same method as for iodide. Ag₂SO₃ in the coprecipitate was removed by washing with 3 mol/L HNO₃ and the excess AgCl and AgBr was removed by use of diluted NH₃, and finally a 1–3 mg precipitate was obtained for AMS measurement of ¹²⁹I. The recovery of iodine species in the entire procedure is higher than 70%. Six seawater samples collected from the Norwegian Sea were analyzed by this method as well as a conventional anion-exchange chromatographic method; the results from the two methods show no significant difference (<i>p</i> = 0.05). Because only one separation step and fewer chemicals are involved in the procedure, this method is suitable for operation on board sampling vessels, as it avoids the transport of samples to the laboratory and storage for a longer time before analysis, therefore significantly improving the analytical capacity and reliability of speciation analysis of ¹²⁹I. This improvement can stimulate oceanographic tracer studies of ¹²⁹I

Air entrainment and free-surface fluctuations in A-type hydraulic jumps with an abrupt drop

In high dam construction projects in China, stilling basin design with an abrupt bottom drop is sometimes introduced to reduce the bottom velocity and pressure loads by generating A-type hydraulic jumps. Although the stilling basin design is not new, A-type hydraulic jumps have not been studied taking into account the air entrainment and evolution of internal air–water flow structures. This paper presents an experimental study of self-aerated A-type jumps in terms of bubble transport and free-surface fluctuations over the bottom drop. Four Froude numbers from 4.1 to 10.3 are tested for three drop heights, in addition to the flat-bottom case. Compared to the classic hydraulic jumps, A-jumps are observed with longer jump lengths and weaker free-surface fluctuations. The downward deflection of the jet-shear flow and formation of a bottom roller in the step cavity require a modification to the analytical expression of velocity and void fraction distributions. The relationship between the bubble diffusivity and jump spreading rate differs from that in classic hydraulic jumps, suggesting a faster expansion of the bubble diffusion layer than the turbulent shear flow downstream of the drop, especially for large drop heights. At large approach velocities, the reattachment of the deflected jet-shear flow to the lowered bed may cause a local rise in bubble counts downstream the bottom roller. Further increase in drop height results in a W-jump with overwhelming bottom roller over the surface roller and an arced surface jet, which is beyond the scope of this study.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Hydraulic Structures and Flood Ris

Method of Polonium Source Preparation Using Tellurium Microprecipitation for Alpha Spectrometry

A thin-layer source for the counting of polonium isotopes by alpha spectrometry can be rapidly prepared using microprecipitation with tellurium. Polonium was first coprecipitated with the reduction of tellurium by stannous chloride, followed by microfiltration onto a membrane filter for counting. This microprecipitation method is faster, cheaper, and more convenient than the traditional spontaneous deposition method, with an excellent Po recovery (>90%) under optimal conditions. The influences of several experimental parameters, including Te­(IV) quantity, reaction time, and HCl molarity, were examined to determine the optimal conditions for Te microprecipitation. The decontamination factors of potential interferences from various radionuclides (Ra, Th, U, Pu, Am) for the counting of long-lived polonium isotopes (²⁰⁸Po, ²⁰⁹Po, and ²¹⁰Po) were also evaluated, and the results confirmed a good selectivity on polonium by this microprecipitation method. Due to its strong resistance to high acidity up to 12 M HCl, the method would be particularly suitable for rapid determination of ²¹⁰Po in acid leaching solution of solid samples