A simple index explains annual atrazine transport from surface runoff‐prone watersheds in the north‐central USA          下载免费PDF全文

E. J. Sadler  K. A. Sudduth  R. N. Lerch  C. Baffaut  N. R. Kitchen 《水文研究》2014,28(2):210-217

Year‐to‐year dynamics in weather affect both the timing of application and the potential hydrologic transport of pesticides. Further, the most commonly used pesticides dissipate in the environment during the growing season. Interactions among these factors – hydrology, timing of application and dissipation kinetics – hinder the detection of temporal trends in transport. It is increasingly important to be able to discern such trends, to judge effectiveness of management practices or to determine whether observed changes were caused by management or weather. In previous work, a cumulative vulnerability index was developed to account for these three factors. It explained 63% of annual variation in atrazine load in the Goodwater Creek Experimental Watershed (GCEW). The objectives of the current work were (i) to generalize the cumulative vulnerability index to explicitly account for variation in watershed size, area treated with atrazine and average application rate; (ii) to test the overall performance on watersheds showing such variation; and (3) to test whether the generalized index properly accounted for the additional input parameters. The generalized index was tested using data from GCEW (73.7 km²) and seven additional watersheds in the northeast Missouri claypan region that varied in size from 212 to 1180 km² and from 4% to 23% of watershed area planted to corn or sorghum. Across 32 site‐years, the generalized index explained 84% of variation in annual atrazine load. Further, tests of residuals showed no dependence on either watershed area or fraction of area planted to corn and sorghum, indicating that these parameters were properly integrated into the index. The performance of the index supports the conclusion that data obtained from GCEW is representative of the Mark Twain Lake Basin and likely the entire Central Claypan Major Land Resource Area. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

A novel device with macrophytes and bio balls as a rehabilitation tool for small eutrophic urban ponds: a mesocosm approximation     

《Limnologica》2019

During the last century, the human-derived impact on freshwater systems has been severe all around the world. Artificial eutrophication has an outstanding relevance in urban aquatic ecosystems and it is recognized as one of the most common problems associated with water deterioration in urban lakes and ponds. Therefore, more studies regarding the trophic interactions and the potential rehabilitation methods should be encouraged. Our aim is to evaluate at a mesocosm scale, a device composed of native aquatic plants, either submerged (SPD) or floating (FPD), including an extra artificial potential refuge (bio balls rolls) for zooplankton as a rehabilitation tool for urban ponds. As regards the impact of the tested devices on water quality variables, FPD provoked a decrease in TP and pH. In turns, SPD maintained the dissolved oxygen concentrations above those registered in FPD. Transparency was significantly higher in the presence of plants at final time. Differences in phytoplankton morpho-functional group diversity and zooplankton functional feeding groups were registered by the end of the experiment. Zooplankton abundance at the artificial refuges was higher than at the water column; a study of the efficiency of the bio balls rolls as potential active/passive refugees is merited.Considering benefits on water quality variables, we suggest that a device combining floating macrophytes plus the bio ball rolls deserves to be further tested at a greater scale in order to be considered as a water rehabilitation tool, including plant harvest.  相似文献   

Experimental study of the dynamic interaction between the foundation of the NEES/UCSD Shake Table and the surrounding soil: Reaction block response     

J.E. Luco  O. Ozcelik  J.P. Conte  L.H. Mendoza 《Soil Dynamics and Earthquake Engineering》2011

An extensive experimental study of the dynamic interaction between the foundation block for the NEES/UCSD Large High Performance Outdoor Shake Table and the surrounding soil was conducted in 2003. The vibrations induced by the two NEES@UCLA large eccentric mass shakers were recorded at multiple stations within the reinforced concrete foundation block and on the surface of the surrounding soil up to distances of 270 m from the block. The present paper focuses on analysis of the data recorded within the reaction block including the average rigid body motion of the foundation and its dependence on frequency, and the deformation of the block for longitudinal (EW), transverse (NS), and torsional excitation. Comparison of the reaction block response during shaker induced vibrations with that for the much stronger actuator forces shows that linearity holds for the range of forces involved. Comparisons with analytical results for a simplified model of the foundation show good agreement between experimental and theoretical results.  相似文献   

饱和黄土液化标准的试验研究     

孙海妹  王兰民  王平  刘红玫 《地震工程学报》2011,33(Z1)

根据饱和黄土在动荷载振动作用下的试验结果提出了以黄土的3%应变为主要考虑因素的液化破坏标准。试验表明:在固结不排水的动三轴试验中,黄土结构连接强度随循环次数的增加而逐渐丧失,体积收缩,在不排水条件下转化为孔隙水压力的上升和有效应力的下降,最终可能出现初始液化和循环活动性现象。3%轴应变一定出现在初始液化前;3%轴应变后应变大幅增加,孔压有可能达到初始有效固结围压,也有可能在初始液化前破坏。3%轴变形是黄土稳定变形和大幅变形的临界点。  相似文献   

Glacial ice cores: A model system for developing extraterrestrial decontamination protocols     

Brent C. Christner 《Icarus》2005,174(2):572-584

Evidence gathered from spacecraft orbiting Mars has shown that water ice exists at both poles and may form a large subsurface reservoir at lower latitudes. The recent exploration of the martian surface by unmanned landers and surface rovers, and the planned missions to eventually return samples to Earth have raised concerns regarding both forward and back contamination. Methods to search for life in these icy environments and adequate protocols to prevent contamination can be tested with earthly analogues. Studies of ice cores on Earth have established past climate changes and geological events, both globally and regionally, but only recently have these results been correlated with the biological materials (i.e., plant fragments, seeds, pollen grains, fungal spores, and microorganisms) that are entrapped and preserved within the ice. The inclusion of biology into ice coring research brings with it a whole new approach towards decontamination. Our investigations on ice from the Vostok core (Antarctica) have shown that the outer portion of the cores have up to 3 and 2 orders of magnitude higher bacterial density and dissolved organic carbon (DOC) than the inner portion of the cores, respectively, as a result of drilling and handling. The extreme gradients that exist between the outer and inner portion of these samples make contamination a very relevant aspect of geomicrobiological investigations with ice cores, particularly when the actual numbers of ambient bacterial cells are low. To address this issue and the inherent concern it raises for the integrity of future investigations with ice core materials from terrestrial and extraterrestrial environments, we employed a procedure to monitor the decontamination process in which ice core surfaces are painted with a solution containing a tracer microorganism, plasmid DNA, and fluorescent dye before sampling. Using this approach, a simple and direct method is proposed to verify the authenticity of geomicrobiological results obtained from ice core materials. Our protocol has important implications for the design of life detection experiments on Mars and the decontamination of samples that will eventually be returned to Earth.  相似文献   

建立罗非鱼保鲜期实验方程及其应用性探讨     

杨鸣玉 《广东海洋大学学报》1996,(1)

根据实验数据和采用王怡评定罗非鱼感官的评分标准，建立０℃、８℃和１５℃三个温度水平的罗非鱼保鲜期实验方程；同时．实验表明：在温度０℃～５℃下无论采用感官检定或ＴＶＢ－Ｎ，或细菌总数和Ｋ值的指标检定其鲜度，所得的结果均相同。因此．在实际应用时，以０℃温度水平下的实验方程其可靠性较大。  相似文献   

THE CONSTRUCTION OF SIMULTANEOUS OPTIMAL EXPERIMENTAL DESIGNS FOR SEVERAL POLYNOMIALS IN THE CALIBRATION OF ANALYTICAL METHODS     

R.WOLTERS  G.KATEMAN 《地理学报(英文版)》1990,(2)

In this paper a criterion is described for the construction of experimental designs for the evaluation ofcalibration models in analytical chemistry.The proposed criterion seeks a compromise between theD-optimal designs for estimating the parameters of different polynomial models.A computer algorithmis presented for a sequential construction of experimental designs using the optimality criterion.Theperformance of the optimality criterion and the computer algorithm is elaborated for the problem ofdiscrimination between a first-to a third-degree polynomial for the calibration of analytical methods.Anexperimental design consisting of replicate measurements at five distinct levels equally spaced over thecalibration range proved a good solution.  相似文献   

Low velocity impacts into dust: results from the COLLIDE-2 microgravity experiment     

Joshua E. Colwell 《Icarus》2003,164(1):188-196

We present the results of the second flight of the Collisions Into Dust Experiment (COLLIDE-2), a space shuttle payload that performs six impact experiments into simulated planetary regolith at speeds between 1 and 100 cm/s. COLLIDE-2 flew on the STS-108 mission in December 2001 following an initial flight in April 1998. The experiment was modified since the first flight to provide higher quality data, and the impact parameters were varied. Spherical quartz projectiles of 1-cm radius were launched into quartz sand and JSC-1 lunar regolith simulant targets 2-cm deep. At impact speeds below ∼20 cm/s the projectile embedded itself in the target material and did not rebound. Some ejecta were produced at ∼10 cm/s. At speeds >25 cm/s the projectile rebounded and significant ejecta was produced. We present coefficients of restitution, ejecta velocities, and limits on ejecta masses. Ejecta velocities are typically less than 10% of the impact velocity, and the fraction of impact kinetic energy partitioned into ejecta kinetic energy is also less than 10%. Taken together with a proposed aerodynamic planetesimal growth mechanism, these results support planetesimal growth at impact speeds above the nominal observed threshold of about 20 cm/s.  相似文献   

Searching for inner-Earth objects: a possible ground-based approach     

Gianluca Masi 《Icarus》2003,163(2):389-397

The likely existence of bodies orbiting the Sun with aphelia Q < 0.983 AU has been suggested by numerical simulations of the dynamical evolution of the near-Earth objects (NEOs) population. For obvious reasons, these hypothetical minor bodies are called inner-Earth objects (IEOs). While much progresses has been made in learning more about the Amor, Apollo, and Aten population from surveys optimized for their discovery, no large, systematic, and similar observation projects devoted to the search of IEOs have been started. For their own orbital nature, IEOs can be observed only at small solar elongations (<90°), corresponding to regions of the sky currently neglected by the modern, ongoing surveys. This paper discusses a possible ground-based approach to look for IEOs, providing some useful tricks and the results of simulated surveys devoted to their discovery. It will be shown that such a search promises interesting results, the setup of a dedicated project being highly recommended.  相似文献   

GENERALIZED SIMULATED ANNEALING FOR CALIBRATION SAMPLE SELECTION FROM AN EXISTING SET AND ORTHOGONALIZATION OF UNDESIGNED EXPERIMENTS     

JOHN H.KALIVAS 《地理学报(英文版)》1991,(1)

ealibrared.The diseussion in this PaPer foeuses on near一infrared(NIR)sPeetroseoPy as the examPle instrument.However,the Proeedures Presented are aPPlieable tomost methods of instrumental analysis.Essentially,ealibration eonsists of assembling a seriesof samPles eontaining the analyte or analytes at  相似文献