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To study the base flow recession at the watershed scale, the log-scale plot of − dQ/dt ∼ Q proposed by Brutsaert and Nieber [10] has been used to estimate the recession parameters, i.e., the slope and interception of the theoretical recession slope curve. The lower envelope or the best fit in some studies is usually used to determine the recession slope curve for natural watersheds. However, human interferences exist in most watersheds around the world. This paper discusses the impact of human interferences, which include groundwater pumping, water diversion and return flow, on the determination of the recession slope curve and the cloud shape of the data points of − dQ/dt ∼ Q. First, values of − dQ/dt generated for hypothetical watersheds are analyzed. Then real data for three watersheds in Illinois is analyzed to verify the hypothetical analysis. The placement of the recession slope curve depends on the coexistence and relative amount of the evapotranspiration, groundwater pumping or even water diversion if it exists, and the return flow. When the water consumption rate is small, the recession slope curve can even be located at the upper envelope of the cloud of points representing historical data. These results suggest that the use of the lower envelope as a guideline for estimating recession parameters for watersheds subject to human interferences can result in biased estimates. 相似文献
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中子活化分析铂族元素的干扰反应问题 总被引:7,自引:0,他引:7
探讨了中子活化分析铂族元素的一些干扰反应,如Au对Pt的干扰,U对Ru和Pd的干扰,并就Au对Pt的干扰程度进行了详细的计算。在照射时间为1d,中子注量率为1×1013n·cm-2·s-1的条件下进行计算,对于mPt/mAu=1的样品,Au对Pt的干扰达75%;mPt/mAu=10时,干扰达23%;mPt/mAu=20,干扰为13%,mPt/mAu=30,干扰降低为9%。这表明对于多数岩石样品Au干扰Pt相当严重,在采用中子活化法测定地质试样中Pt时必须对Au进行预分离。此外还就U对Ru和Pd的干扰情况进行了讨论,指出对于大多数超镁铁岩和硫化物矿石其干扰可以忽略或只需进行较小的校正,但对于基性岩和酸性岩就必须进行校正 相似文献
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Jérôme C. J. Petit Aurélien Taillez Nadine Mattielli 《Geostandards and Geoanalytical Research》2013,37(3):319-335
Mathematical modelling was combined with experimental Cu isotope measurements to demonstrate the effect of the sample matrix in changing the absolute and relative abundances of spectral interferences from Ti and Cr species. This unforeseen non‐spectral effect, evidenced by variable inaccuracies of the different Zn‐normalised Cu isotope ratios, was investigated by comparing real sedimentary samples and artificial solutions intended to match the Cu:Ti:Cr ratios of the real samples after (one or two step) chromatographic processing. Artificial solutions showed positive bias in δ65CuX/Y with the magnitude depending on (a) the 6XZn/6YZn ratio used for normalisation, (b) the Ti/Cu ratio and (c) the transmission coefficient of the TiO species. In contrast, real samples showed different δ65CuX/Y patterns and displayed a more complex population of Ti and Cr oxides and hydroxides, giving rise to positive and negative inaccuracies that were two to six times higher compared with the artificial samples. The results evidence contrasting behaviour of Ti and Cr when forming polyatomic species in the plasma and stress that artificial solutions may fail to predict how residual elements interact with the analyte/dopant pair during MC‐ICP‐MS analyses. More importantly, the study shows that all Zn isotope ratios do not have the same merit in correcting for mass bias in the presence of matrix elements and should all be monitored to verify the absence of spectral interferences for Cu isotope measurements. In this respect, accurate Cu data could be generally obtained by a two‐step chromatographic purification providing a minimum reduction of ~ 21000 and ~ 3000 times the initial amounts of Ti and Cr, respectively. 相似文献
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Vladimir N. Epov Dominic Lariviere Ekaterina N. Epova R. Douglas Evans 《Geostandards and Geoanalytical Research》2004,28(2):213-224
An experimental study of the interferences produced by macroelements (Na, K, Ca, Mg, Sr, S, Cl, Si, N and C) contained in natural waters during inductively coupled plasma-mass spectrometry (ICP-MS) is presented. The most significant interferences created by these elements were found to be SO, CO, CAr, SiH, SiO, NaH, NaAr, MgAr, CaO, KO and KAr, the magnitude of which was dependant on the concentration of each macroelement. To reduce these interferences, different approaches, for example, desolvating nebulisation, high resolution and dynamic reaction cell ICP-MS were applied and compared. All three approaches were found to be useful tools for significantly reducing various polyatomic interferences. Advantages and disadvantages for each approach are discussed. 相似文献
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Development of Cu and Zn Isotope MC-ICP-MS Measurements: Application to Suspended Particulate Matter and Sediments from the Scheldt Estuary 总被引:1,自引:0,他引:1
Jérôme C.J. Petit Jeroen de Jong Lei Chou Nadine Mattielli 《Geostandards and Geoanalytical Research》2008,32(2):149-166
The present study evaluates several critical issues related to precision and accuracy of Cu and Zn isotopic measurements with application to estuarine particulate materials. Calibration of reference materials (such as the IRMM 3702 Zn) against the JMC Zn and NIST Cu reference materials were performed in wet and/or dry plasma modes (Aridus I and DSN‐100) on a Nu Plasma MC‐ICP‐MS. Different mass bias correction methods were compared. More than 100 analyses of certified reference materials suggested that the sample‐calibrator bracketing correction and the empirical external normalisation methods provide the most reliable corrections, with long term external precisions of 0.06 and 0.07‰ (2SD), respectively. Investigation of the effect of variable analyte to spike concentration ratios on Zn and Cu isotopic determinations indicated that the accuracy of Cu measurements in dry plasma is very sensitive to the relative Cu and Zn concentrations, with deviations of δ65Cu from ?0.4‰ (Cu/Zn = 4) to +0.4‰ (Cu/Zn = 0.2). A quantitative assessment (with instrumental mass bias corrections) of spectral and non‐spectral interferences (Ti, Cr, Co, Fe, Ca, Mg, Na) was performed. Titanium and Cr were the most severe interfering constituents, contributing to inaccuracies of ?5.1‰ and +0.60‰ on δ68/64Zn, respectively (for 500 μg l?1 Cu and Zn standard solutions spiked with 1000 μg l?1 of Ti or Cr). Preliminary isotopic results were obtained on contrasting sediment matrices from the Scheldt estuary. Significant isotopic fractionation of zinc (from 0.21‰ to 1.13‰ for δ66Zn) and copper (from ?0.38‰ to 0.23‰ for δ65Cu), suggest a control by physical mixing of continental and marine water masses, characterized by distinct Cu and Zn isotopic signatures. These results provide a stepping‐stone to further evaluate the use of Cu and Zn isotopes as biogeochemical tracers in estuarine environments. 相似文献