Application of snowmelt runoff model for water resource management

Snow‐covered areas (SCAs) are the fundamental source of water for the hydrological cycle for some region. Accurate measurements of river discharge from snowmelt can help manage much needed water required for hydropower generation and irrigation purposes. This study aims to apply the snowmelt runoff model (SRM) in the Upper Indus basin by the Astore River in northern Pakistan for the years 2000 to 2006. The Shuttle Radar Topographic Mission (SRTM) data are used to generate the Digital Elevation Model (DEM) of the region. Various variables (snow cover depletion curves (SCDCs), temperature and precipitation) and parameters (degree‐day factor, recession coefficient, runoff coefficients, time lag, critical temperature and temperature lapse rate) are used as input in the SRM. However, snow cover data are direct and an important input to the SRM. Satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to estimate the SCA. Normalized difference snow index (NDSI) algorithm is applied for snow cover mapping and to differentiate snow from other land features. Nash–Sutcliffe coefficient of determination (R²) and volume difference (D_V) are used for quality assessment of the SRM. The results of the current research show that for the study years (2000–2006), the average value of R² is 0·87 and average volume difference D_V is 1·18%. The correlation coefficient between measured and computed runoff is 0·95. The results of the study further show that a high level of accuracy can be achieved during the snowmelt season. The simulation results endorse that the SRM in conjunction with MODIS snow cover product is very useful for water resource management in the Astore River and can be used for runoff forecasts in the Indus River basin in northern Pakistan. Copyright © 2011 John Wiley & Sons, Ltd.     

A Common Reference Material for Cadmium Isotope Studies – NIST SRM 3108

Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio ¹¹⁴Cd/¹¹⁰Cd for NIST SRM 3108 lies within ～ 10 ppm Da^?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use.     

Results for Rarely Determined Elements in MPI-DING, USGS and NIST SRM Glasses Using Laser Ablation ICP-MS

New analytical results are reported for rarely determined elements Be, B, Ge, As, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, W, Re, Ir, Pt, Au, Tl and Bi in MPI‐DING and USGS (BCR‐2G, BHVO‐2G, BIR‐1G) silicate glasses and the NIST SRM 610‐614 synthetic soda‐lime glasses using 193 nm ArF excimer laser ablation and quadrupole ICP‐MS. The method used involved external calibration against GOR132‐G for Ir and NIST SRM 610 for other elements, internal standardisation using Ca, and ablation with a crater diameter of 160 μm and a pulsed laser repetition rate of 10 Hz. Small amounts of nitrogen (5 ml min^?1) were added to the central channel gas of the plasma to improve the limits of detection for most of these elements by a factor of 1.2–2.5 and to reduce the oxide interference level to 0.02% (ThO⁺/Th⁺). Under these conditions, the LODs for most of these rarely determined elements were within the range 0.1 to 10 ng g^?1. The operating conditions that were required to minimise ICP‐induced fractionation (U⁺/Th⁺≈ 1) in the mode without nitrogen were accompanied by a 50–60% reduction in sensitivity for elements such as Ca, Au and Pt. In contrast, ICP‐induced fractionation could be minimised (U⁺/Th⁺≈ 1) with no loss of analyte sensitivity in the nitrogen mode. Interferences of CuAr⁺, ZnAr⁺, Cd⁺, Pb²⁺ and Sn⁺ on Pd⁺, Rh⁺, Cd⁺ and In⁺ were corrected. Oxide interferences were not considered due to their lower production rate. Analytical precision, as given by one relative standard deviation (% RSD) was less than 15% for most of the elements present at concentrations greater than 0.1 μg g^?1. A significant negative correlation was found between logarithmic concentration and logarithmic RSD, with a correlation coefficient of ?0.76. This trend indicates that possible chemical heterogeneities for most of these elements are smaller than the analytical uncertainty. Our results for Be, B, Ge, Sb and W are generally in good agreement with their reference values. In contrast, other elements in many of the reference glasses have only information values, upper limits or even no values, which restrict any detailed evaluation of the accuracy of the determined values. However, concentrations from multiple isotopes of one element analysed in this study showed excellent agreement, which guarantee the quality of our data to a certain extent.     

LA‐ICP‐MS Analysis of Small Samples: Carbonate Reference Materials and Larval Fish Otoliths

This article proposes a methodology to analyse the composition of very small carbonate samples such as larval fish otoliths. The chemical composition of otoliths, which are carbonate structures in the inner ear, is often used to explore population dynamics in fishes. Recent advances in laser ablation‐inductively coupled plasma‐mass spectrometry have suggested its potential application to this field. In this study, analyses were performed using a 193 nm ArF Resonetics LA system, coupled to an Agilent 7700X‐ICP‐MS, with the following ablation parameters: a beam diameter of 5 μm, energy of 3 mJ, 2.7 J cm^?2, laser repetition rate of 10 Hz and translation speed of 2.5 μm s^?1. NIST SRM 610 glass was used as the primary calibration material. Performing this protocol, characterisation of a USGS GP‐4 reference material was achieved with suitable precision and accuracy, but the USGS MACS‐3 reference material appeared more heterogeneous under the ablation conditions tested. Calibration was performed using two different beam diameters (5 and 11 μm). Capelin (Mallotus villosus) otoliths measuring between 10 and 20 μm in diameter were tested. Even though a smaller beam diameter and lower energy were used compared with those normally employed to analyse larger otoliths, the method was successful.     

Precise and Accurate Doping of Nanoporous Silica Gel for the Synthesis of Trace Element Microanalytical Reference Materials

This study presents an experimental procedure to fabricate high‐purity silica glass containing a selected element at a specified mass fraction. The procedure was used to prepare glasses doped with trace‐level mass fractions of Ti with the goal of improving analytical confidence when measuring trace elements in quartz. Systematic tests were performed to determine the ideal conditions and procedures for doping nanoporous silica gel with the highest efficiency of dopant recovery. Silica gel was cleaned in concentrated HCl, immersed in a non‐polar doping medium at a controlled pH and doped with precise quantities of ICP‐MS standard solution. Using liquids composed of longer chain molecules as the doping medium diminishes recovery, suggesting that large molecules could obstruct nanopores to inhibit capillary uptake of the dopant. A control experiment using crystalline quartz reinforced the effectiveness of nanoporous silica gel for doping with trace‐level precision. Layered aggregates of silica gel doped with different Ti mass fractions were hot‐pressed to create multi‐layered reference materials that were analysed with multiple techniques at a variety of spatial scales. Analyses at the intra‐grain scale (cathodoluminescence scanning electron microscopy, electron probe microanalysis), at the single grain scale (SIMS), at the sample layer scale (EPMA, laser ablation‐ICP‐MS) and at the bulk scale (ICP‐OES) demonstrated acceptable homogeneity at sample volumes characteristic of most microanalysis techniques and show that nanoporous silica gel holds promise as a highly retentive doping substrate for preparing reference materials for laser‐, electron‐ and ion‐beam microanalysis.     

Boron and Oxygen Isotope Composition of Certified Reference Materials NIST SRM 610/612 and Reference Materials JB-2 and JR-2

We present data on the concentration, the isotope composition and the homogeneity of boron in NIST silicate glass reference materials SRM 610 and SRM 612, and in powders and glasses of geological reference materials JB-2 (basalt) and JR-2 (rhyolite). Our data are intended to serve as references for both microanalytical and wet-chemical techniques. The δ¹¹ B compositions determined by N-TIMS and P-TIMS agree within 0.5% and compare with SIMS data within 2.5%. SIMS profiles demonstrate boron isotope homogeneity to better than δ¹¹ B = 2% for both NIST glasses, however a slight boron depletion was detected towards the outermost 200 μm of the rim of each sample wafer. The boron isotope compositions of SRM 610 and SRM 612 were indistinguishable. Glasses produced in this study by fusing JB-2 and JR-2 powder also showed good boron isotope homogeneity, both within and between different glass fragments. Their major element abundance as well as boron isotope compositions and concentrations were identical to those of the starting composition. Hence, reference materials (glasses) for the in situ measurement of boron isotopes can be produced from already well-studied volcanic samples without significant isotope fractionation. Oxygen isotope ratios, both within and between wafers, of NIST reference glasses SRM 610 and SRM 612 are uniform. In contrast to boron, significant differences in oxygen isotope compositions were found between the two glasses, which may be due to the different amounts of trace element oxides added at ten-fold different concentration levels to the silicate matrix.     

Isotope Dilution MC-ICP-MS Rare Earth Element Analysis of Geochemical Reference Materials NIST SRM 610, NIST SRM 612, NIST SRM 614, BHVO-2G, BHVO-2, BCR-2G, JB-2, WS-E, W-2, AGV-1 and AGV-2

We present data for the concentrations of eleven rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu) in eleven international geochemical reference materials obtained by isotope dilution multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We have analysed both rock powders and synthetic silicate glasses, and the latter provide precise data to support the use of these as reference materials for in situ trace element determination techniques. Our data also provide precise measurements of the abundance of mono-isotopic Pr in both glasses and powders, which allows more accurate constraints on the anomalous redox-related behaviour of Ce during geochemical processes. All materials were analysed in replicate providing data that typically reproduce to better than one percent. Sm/Nd ratios in all these materials also reproduce to better than 0.2% and are accurate to < 0.2% and can thus be used as calibrants for Sm-Nd geochronology. Our analyses agree well with existing data on these reference materials. In particular, for NIST SRM 610, USGS BHVO-2, AGV-1 and AGV-2, our measured REE abundances are typically within < 2% (and mostly 1%) of REE concentrations previously determined by isotope dilution analysis and thermal ionisation mass spectrometry, consistent with the higher degree of precision and accuracy obtained from isotope dilution techniques. Close agreement of results between basaltic glass reference materials USGS BHVO-2G and BCR-2G and the BHVO-2 and BCR-2 powders from which they were created suggests that little fractionation, concentration or dilution of REE contents occurred during glass manufacture.     

Effect of climatic change on snowmelt runoffs in mountainous regions of inland rivers in Northwestern China

Snow is one of the most active natural elements of snow cover through its high albedo, variation of the the cryosphere on the earth surface. Its unique proper- snow cover distribution and frozen soils in regional ties, such as areal extent, surface albedo, and snow scales not only affect local climate and environments, depth are important parameters in global energy bal- but also feedback to large-scale, or even global cli- ance models. On global and terrestrial scales, a large matic change th…     

Compositional Heterogeneity in NIST SRM 610-617 Glasses

Extensive compositional heterogeneity is shown to affect at least twenty four of the doped trace elements in the NIST SRM 610-617 glasses.
Compositional profiling and mapping using laser ablation ICP-MS reveals that all NIST SRM 610-617 wafers examined here contain domains that are significantly depleted in Ag, As, Au, B, Bi, Cd, Cr, Cs, Mo, Pb, Re, (Rh), Sb, Se, Te, Tl and W, and antithetically enriched in Cu (and Pt), with large enrichments in Cd, Fe and Mn also being encountered in some cases. These domains are visible in doubly polished wafers by unaided visual inspection and by transmitted light and schlieren microscopy. They occur in close proximity to the wafer perimeters and also as stretched and complexly folded forms within wafer interiors. The chemical and optical properties of these heterogeneous domains are consistent with those of compositional cords, a phenomenon of glass manufacture where glass bulk composition and physical properties are modified by loss of volatile components from the molten glass surface. The NIST SRM 610-617 glasses may be considered reliable reference materials for microanalysis of only between one half and two thirds of the trace elements with which they were doped, including Be, Mg, Sr, Ba, Sc, Y, REE, V, Zr, Hf, Nb, Ta, Th, U, Ga, In, Sn, Co, Ni and Zn. These elements show no evidence of significant heterogeneity, indicating that the original glass constituents and possible residues remaining in the furnace from preceding glass batch fusions were well homogenised during manufacture.     

Determination of Trace Elements in BCS CRM 313/1 (BAS) and NIST SRM 1830 by Inductively Coupled Plasma-Mass Spectrometry and Instrumental Neutron Activation Analysis

In the past, there has been little interest in the trace element characteristics of quartz, and in consequence little activity in the trace element characteristics of reference materials with high silicon content. The main purpose of this paper is to contribute to the characterisation of two international certified reference materials, BCS 313/1 from the Bureau of Analysed Samples, (BAS), UK and SRM 1830 from the National Institute of Standards and Technology (NIST), USA. BCS 313/1 was analysed by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), solution ICP-MS and instrumental neutron activation analysis (INAA). NIST SRM 1830 was analysed by LA-ICP-MS and INAA. Analytical results are reported for more than forty elements, most of them for the first time. For most elements, the results obtained by the different methods agree within 15 % relative. The recent, heightened interest in quartz and in particular the precise determination of trace0element contents in natural quartz samples requires the use of well characterised reference materials such as BCS 313/1 and SRM 1830, to which this study is designed to contribute.