Assessment of alternative adsorption models and global sensitivity analysis to characterize hexavalent chromium loss from soil to surface runoff          下载免费PDF全文

Chuan‐An Xia  Juxiu Tong  Bill X. Hu  Xiujie Wu  Alberto Guadagnini 《水文研究》2018,32(20):3140-3157

We investigate our ability to assess transfer of hexavalent chromium, Cr(VI), from the soil to surface runoff by considering the effect of coupling diverse adsorption models with a two‐layer solute transfer model. Our analyses are grounded on a set of two experiments associated with soils characterized by diverse particle size distributions. Our study is motivated by the observation that Cr(VI) is receiving much attention for the assessment of environmental risks due to its high solubility, mobility, and toxicological significance. Adsorption of Cr(VI) is considered to be at equilibrium in the mixing layer under our experimental conditions. Four adsorption models, that is, the Langmuir, Freundlich, Temkin, and linear models, constitute our set of alternative (competing) mathematical formulations. Experimental results reveal that the soil samples characterized by the finest grain sizes are associated with the highest release of Cr(VI) to runoff. We compare the relative abilities of the four models to interpret experimental results through maximum likelihood model calibration and four model identification criteria (i.e., the Akaike information criteria [AIC and AIC_C] and the Bayesian and Kashyap information criteria). Our study results enable us to rank the tested models on the basis of a set of posterior weights assigned to each of them. A classical variance‐based global sensitivity analysis is then performed to assess the relative importance of the uncertain parameters associated with each of the models considered, within subregions of the parameter space. In this context, the modelling strategy resulting from coupling the Langmuir isotherm with a two‐layer solute transfer model is then evaluated as the most skilful for the overall interpretation of both sets of experiments. Our results document that (a) the depth of the mixing layer is the most influential factor for all models tested, with the exception of the Freundlich isotherm, and (b) the total sensitivity of the adsorption parameters varies in time, with a trend to increase as time progresses for all of the models. These results suggest that adsorption has a significant effect on the uncertainty associated with the release of Cr(VI) from the soil to the surface runoff component.  相似文献   

A machine learning approach for predicting computational intensity and domain decomposition in parallel geoprocessing     

Peng Yue  Fan Gao  Boyi Shangguan  Zheren Yan 《International journal of geographical information science》2020,34(11):2243-2274

ABSTRACT

High performance computing is required for fast geoprocessing of geospatial big data. Using spatial domains to represent computational intensity (CIT) and domain decomposition for parallelism are prominent strategies when designing parallel geoprocessing applications. Traditional domain decomposition is limited in evaluating the computational intensity, which often results in load imbalance and poor parallel performance. From the data science perspective, machine learning from Artificial Intelligence (AI) shows promise for better CIT evaluation. This paper proposes a machine learning approach for predicting computational intensity, followed by an optimized domain decomposition, which divides the spatial domain into balanced subdivisions based on the predicted CIT to achieve better parallel performance. The approach provides a reference framework on how various machine learning methods including feature selection and model training can be used in predicting computational intensity and optimizing parallel geoprocessing against different cases. Some comparative experiments between the approach and traditional methods were performed using the two cases, DEM generation from point clouds and spatial intersection on vector data. The results not only demonstrate the advantage of the approach, but also provide hints on how traditional GIS computation can be improved by the AI machine learning.  相似文献   

Characteristics of Spatial and Temporal Variations of Monthly Mean Surface Air Temperature over Qinghai-Tibet Plateau   总被引：1，自引：0，他引：1  

ZHANG Qianggong KANG Shichang YAN Yuping 《中国地理科学(英文版)》2006,16(4):351-358

1 Introduction The Qinghai-Tibet Plateau, known as the highest plateau with the most complex topography in the world, covers an area of more than 200km2, with a mean elevation of more than 4000m a.s.l. (Ye and Gao, 1979). Surrounded by the Earth’s highest mountains, such as the Himalayas, Pamir, Kunlun Mountains, the plateau plays a significant role in climate change in China even in the world, thus attracted great attention of researchers. Up to now, many achievements have been gained by…  相似文献   

Observational evidence for solar coronal decimetric radio pulsations with very short periods     

Xie Rui-xiang  Wang Min  Shi Shuo-biao  Xu Chun  Li Wei-hua  Yan Yi-hua 《Chinese Astronomy and Astrophysics》2003,27(4):426-434

Using the decimetric (700–1500 MHz) radio spectrometer and the synchronous observational system with high temporal resolution at four frequencies (1420, 2130, 2840 and 4260 MHz) of Yunnan Observatory, two rare events were observed on 2001 June 24 and 1990 July 30. The former was a small radio burst exhibiting pulsations with short periods (about 29, 40 and 100 ms) in the impulsive phase. The latter was a large radio burst, which at 2840 MHz produced radio pulsations with period of about 30 ms. This paper focuses on pulsations with very short periods in the range of 29–40 ms. The mechanism of generation of such pulsations may be modulation of radio radiation by the periodic trains of whistler packets originating in unstable regions of the corona. Alternatively, these pulsations can be attributed to wave-wave non-linear interactions of electrostatic upper hybrid waves driven by beams of precipitating electrons in flaring loops.  相似文献   

AR（P）参数估计协方差方法与其改进型方法的对比研究     

楚岩  祝轩 《地球科学与环境学报》1997,(Z1)

定性分析协方差方法及其改进型在ＡＲ（Ｐ）参数估计中的应用，提供了一种估计参数的计算机上机流程图，比较了协方差方法及其改进型谱估计结果。  相似文献   

对地方电视台转播CCTV时延的测定     

任燕  梁双有 《时间频率学报》1997,(1)

讲述了同步广播卫星电视时间信号的测量方法和测量结果，获得了CCTV1、CCTV2通过同一颗卫星（亚太－1A）转播的时延差值为16333μs，测量精度在10ns以内；CCTV2、CCTV4分别经两颗卫星（亚太－1A、亚洲－Ⅱ）转播，在陕西天文台卫星地面接收站时延差值为1644．20μs，精度为50μs，并分析了影响时延差值和精度的原因。同时测量了地方电视台转播亚太－1A的CCTV信号与直接接收亚太－1A的CCTV信号的时延差值，其测量精度为0．1μs。这些结果为利用同步广播卫星的电视信号进行高精度的时间服务提供了参考依据。  相似文献   

海岩小说的几种叙述模式及弊端     

姚国军  李霞 《广东海洋大学学报》2006,26(5):87-90

海岩的长篇小说《河流如血》再创出版高记录，但作家仍局限于特有的小说叙述模式，这部作品设能做到相应的创新。概言之，模式第一面是“刑侦＋恋爱”；模式第二面是“财子＋佳人”；模式第三面是“道德＋法制”。文学创作需要不断创新，创新的过程也是对创作模式的不断突破过程。作家应该警惕的是，不要让模式成为创作的桎梏。  相似文献   

CARBON DYNAMICS OF WETLAND IN THE SANJIANG PLAIN   总被引：2，自引：0，他引：2  

SONG Chang-chun    WANG Yi-yong  WANG Yue-si  YAN Bai-xing WANG De-xuan  ZHAO Zhi-chun  LOU Yan-jing 《中国地理科学(英文版)》2003,13(3):228-231

1INTRODUCTIONWetlandsplayanimportant roleintheprocessofcar-bonstorage.Thetotalcarbonstoredindifferentkindsofwetlandsisabout15%-35%ofthetotalcarboninthegloballandsoils(POSTetal.,1982;GORHAM,1991).Inaddition,wetlandsaresignificantnaturalsources fortheatmospheric CH4 (MOORE,1994).It isestimatedthatabout110×1012gCH4 originates fromanaerobicdecompositioninthenaturalwetlands,CH4 emission fromthenaturalwetlandsis15%-30%oftheglobalCH4 emission andtheCH4 emission from thepeat land at hi…  相似文献   

A Type IV Radio Burst Associated with Type III Burst,Pulsation and Spike Emissions     

Wang  M.  Xie  R.X.  Duan  C.C.  Yan  Y.H.  Sych  R.A.  Altyntsev  A.T. 《Solar physics》2003,212(2):407-424

A type IV radio burst accompanied by several normal- and reverse-drifting type III bursts, multiple long-term quasi-periodic pulsations and spikes was observed with the radio spectrometers (1.0–2.0 and 2.6–3.8 GHz) at National Astronomical Observatories of China (NAOC) on 23 September 1998. In combination with the images of Siberian Solar Radio Telescope (SSRT) of Russia, the complex and multiple magnetic structures inferred from the radio bursts reveal the existence of both large-scale and small-scale magnetic structures. This event suggests that the geometries of coronal magnetic fields contain multiple discrete electron acceleration/injection sites at different heights, and extended open and closed magnetic field lines. It can be shown that the energetic electrons gain access to open, diverging and closed field lines thus producing different types of radio bursts. From the characteristics of position, polarization, dispersion and displacement of the sources, the model of the type IV event is supported, which involves synchrotron emission from the electrons confined by the rapid scattering through the interaction of hydromagnetic wave with particles.  相似文献   

Tidal effects on temperature front in the Yellow Sea   总被引：5，自引：0，他引：5  

Ma Jian  Qiao Fangli  Xia Changshui  Yang Yongzeng 《中国海洋湖沼学报》2004,22(3):314-321

Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades in autumn as thermocline declines. TF intensity ⋎S _T ⋎ is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the TF. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).  相似文献