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   

Comment on “Elevated tungsten and cobalt in airborne particulates in Fallon,Nevada: Possible implications for the childhood leukemia cluster” by P.R. Sheppard,G. Ridenour,R.J. Speakman and M.L. Witten     

《Applied Geochemistry》2006,21(6):1083-1085

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Characteristics of spectral aerosol optical depths over India during ICARB     

S. Naseema Beegum  K. Krishna Moorthy  Vijayakumar S. Nair  S. Suresh Babu  S. K. Satheesh  V. Vinoj  R. Ramakrishna Reddy  K. Rama Gopal  K. V. S. Badarinath  K. Niranjan  Santosh Kumar Pandey  M. Behera  A. Jeyaram  P. K. Bhuyan  M. M. Gogoi  Sacchidanand Singh  P. Pant  U. C. Dumka  Yogesh Kant  J. C. Kuniyal  Darshan Singh 《Journal of Earth System Science》2008,117(1):303-313

Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Ångström parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Ångström coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from tshe adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Ångström exponent (α) remained significantly lower (～1) over the Arabian Sea compared to Bay of Bengal (BoB) (～1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of α, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in α over the BoB.  相似文献   

Implementing integrated oceans management: Australia's south east regional marine plan (SERMP) and Canada's eastern Scotian shelf integrated management (ESSIM) initiative     

《Marine Policy》2005,29(5):391-405

Integrated oceans management (IOM) is emerging in the international arena as a tool in meeting requirements for sustainable use of ocean space and marine resources. Australia and Canada are at the forefront of these developments and, being without set precedents, each state has adopted quite different strategies to implement IOM—Australia adopting a policy-driven approach delivered through Regional Marine Plans and Canada developing legislation that provided a framework for policy implementation delivered through an Integrated Management Framework. Despite these significant differences, examination of initiatives in both states indicates that there are also significant commonalities and shared experiences, providing important lessons for implementing IOM.  相似文献   

Atmospheric input of trace elements to the western Pacific Ocean and the Kuroshio ocean area     

Qian Fenlan  Yu Hongjian  Lan Youchang  Chen Zhi  Zhou Mingyu  Farn Parungo  Wu Peiming 《海洋学报(英文版)》1996,15(1):69-84

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The influence of 30~60 d oscillation on the development of the South China Sea summer monsoon     

WEN Zhiping  HE Haiyan  HUANG Ronghui 《海洋学报(英文版)》2004,23(4):569-579

Using the National Center for Enviromental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and NOAA satellite-obser ved outgoing long-wave radiation (OLR) data, the development of the South China Sea (SCS) summer monsoon and intraseasonal (30-60 d) oscillation (ISO) have been examined. The results show that there exists obvious interannual variability of intraseasonal oscillaiton. Using the 16 a time series of filtered OLR averaged over the SCS, an index is defined to define ““onset events““ over the SCS on the ISO time scales. Of the 16 a examined here, 10 shows a strong ISO signal in the onset of monsoon convection over the SCS. In these cases, the ISO initially suppresses the seasonal development of southwesterly and cyclonic circulation over the SCS before the ISO onset. As the ISO propagates northeastward, the low frequency cyclonic circulation anomaly occurs in the SCS and the low frequency southwesterly wind and convection over here dramatically intensify. The northeast progression of the ISO anomaleis plays a role in the initial suppression and then acceleration of the seasonal cycle of the SCS summer monsoon.  相似文献   

Coccolith distribution patterns in South Atlantic and Southern Ocean surface sediments in relation to environmental gradients     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(6):1073-1099

In this study, the coccolith compositions of 213 surface sediment samples from the South Atlantic and Southern Ocean were analysed with respect to the environmental parameters of the overlying surface waters. From this data set, the abundance patterns of the main species and their ecological affinities were ascertained. In general, Emiliania huxleyi is the most abundant species of the recent coccolith assemblages in the study region. However, the lower photic zone taxa, composed of Florisphaera profunda and Gladiolithus flabellatus often dominate the assemblages between 20°N and 30°S. If E. huxleyi is excluded, Calcidiscus leptoporus and F. profunda become the most abundant species, each dominating discrete oceanographic regimes. While F. profunda is very abundant in the sediments underneath warmer, stratified surface waters with a deep nutricline, Calcidiscus leptoporus is encountered in high-productivity environments. Furthermore, the results of a canonical correspondence analysis reveal affinities of Gephyrocapsa spp., Helicosphaera spp. and Coccolithus pelagicus for intermediate to higher nutrient conditions in a well-mixed upper water column. In contrast, Gladiolithus flabellatus seems to be associated with high temperatures and salinities under low-nutrient conditions. Based on the relative abundances of Calcidiscus leptoporus, F. profunda, Gladiolithus flabellatus, Helicosphaera spp., Umbilicosphaera foliosa, Umbilicosphaera sibogae and a group of subordinate subtropical species, six surface sediment assemblages have been identified, which reflect the distribution and characteristics of the overlying surface waters. Their distribution appears to be mainly a function of the relative position of the nutricline and thermocline in the overlying photic zone.  相似文献   

潮汐对瞬态气候响应模拟的影响研究     

于溢  刘海龙  林鹏飞  兰健 《海洋学报(英文版)》2020,39(1):52-62

In this study, the impact of oceanic processes on the sensitivity of transient climate change is investigated using two sets of coupled experiments with and without tidal forcing, which are termed Exp_Tide and Exp_Control,respectively. After introducing tidal forcing, the transient climate response(TCR) decreases from 2.32 K to 1.90 K,and the surface air temperature warming at high latitudes decreases by 29%. Large ocean heat uptake efficiency and heat storage can explain the low TCR in Exp_Tide. Approximately 21% more heat is stored in the ocean in Exp_Tide(1.10×10~(24) J) than in Exp_Control(0.91×10~(24) J). Most of the large ocean warming occurs in the upper 1 000 m between 60°S and 60°N, primarily in the Atlantic and Southern Oceans. This ocean warming is closely related to the Atlantic Meridional Overturning Circulation(AMOC). The initial transport at mid-and high latitudes and the decline in the AMOC observed in Exp_Tide are both larger than those observed in Exp_Control. The spatial structures of AMOC are also different with and without tidal forcing in present experiments. The AMOC in Exp_Tide has a large northward extension. We also investigated the relationship between AMOC and TCR suggested by previous studies using the present experiments.  相似文献   

Summer Arctic sea fog     

Xie Simei  Xue Zhenhe  Jiang Dezhong  Zou Bin  Qu Shaohou 《海洋学报(英文版)》2001,20(2):183-196

I~IOXSea fog is a kind of dangerous weather. Chinese sea fog experts, Wang Binhua (1983),Hu Ruijin and Zhou Faxiu (1998) and Hu Jifu et al. (1996) studied sea fog rather Systematically. FOreign Experts also Paid great attention to sea fog. Ernlnons and Montgomery(1974), chipper (1994) and Rayrnond et al. (1989) have studied sea fog thorOUghly.HOwever, studies on Arctic sea ice have rarely been carried Out becauSe of the sever environment and less htnnan activity in the region. There …  相似文献   

Seismic geomorphology of buried channel systems on the New Jersey outer shelf: assessing past environmental conditions     

《Marine Geology》2005,214(4):339-364

Quantitative geomorphologic analysis of shallowly buried, dendritic channel systems on the New Jersey shelf provides estimates of paleo-hydrologic parameters needed to link channel morphology to the former hydrodynamic setting. These channels, observed in 1–4 kHz deep-towed chirp seismic data, formed presumably as fluvial systems when the shelf was exposed during the Last Glacial Maximum (LGM). The presumed fluvial origin of these channels is supported by their incision into underlying Pleistocene strata, a chaotic seismic fill unit at their bases which may be indicative of non-marine gravel lag, and measured stream junction angles that are consistent with a riverine origin. The channels would also have been subjected to estuarine/tidal environments during ensuing sea-level rise. We employ empirically derived hydraulic equations for modern rivers and estuaries to estimate paleo-discharges, velocities and maximum shear stresses, using the preserved and interpolated paleo-channel geometries as a guide. Generally, trunk/main channels have box-like, symmetric cross-sections, with width/depth ratios of >100, whereas smaller, tributary channels have more v-shaped, asymmetric cross-sections with width/depth ratios of ∼40–70. The high width/depth ratios, along with low sinuosities (∼1.1) and slopes (<0.02°), are consistent with braided streams as specified by a modern river classification system. However, the channels show no evidence of braiding. We hypothesize instead that these channel systems are immature, having had insufficient time to develop high sinuosities that would otherwise be expected before they were drowned by the Holocene transgression. Mean paleo-flow estimates for these systems assuming a tidal environment (1.0–1.5 m/s) are consistent with modern tidal creeks comparable to the sizes of channels observed here (<2 km wide and <25 m deep). Estimated tidal shear stresses would be sufficient to initiate sediment transport of grains 2–8 mm in diameter (coarse sand and fine gravel) as bedload and finer grained material in suspension. However, paleo-flow estimates assuming a fluvial environment (1.1–2.0 m/s) are generally too high for a non-tidal creek, given the presumed low hydraulic gradients in this coastal plain setting. Retrodicted fluvial discharge and boundary shear stresses would have been sufficient to transport particles up to ∼15 mm in diameter (gravel) as bedload; these grain sizes are too coarse to be transported by sluggish coastal plain rivers. We conclude that either flows were quite high when this system was first incised fluvially, perhaps due to meltwater pulses following the LGM, or that tidal influences have modified the original fluvial geometry.  相似文献