Provision,transport and deposition of debris in urban waterways

The transport of woody debris from urban surfaces,through local urban waterways,to constriction and blockage risk locations is not well understood.Flume trials have identified debris and watercourse dimensions as influential factors on debris movement,and large woody debris movement has been traced in the natural rural environment using time series photography,active transponders,and field surveys.Using novel passive transponder technology,small woody debris has been traced through an urban case study watercourse to establish key influential factors on urban debris transport.Through incorporating urban debris transport detail into the source and deposition process,a complete picture of urban debris transport can be created,supporting effective culvert and trash screen design,watercourse maintenance and blockage risk assessment.This case study highlights that factors beyond watercourse depth and velocity are influential in debris movement within an urban watercourse.Debris dimension and source location upstream are shown to significantly affect the potential for debris to reach a downstream constriction,illustrating a possible distance limitation in nuisance flow debris blockage risk.     

Intramolecular carbon isotopic analysis of acetic acid by direct injection of aqueous solution

We report an improved method for determining the intramolecular carbon isotopic composition of acetate using direct injection of aqueous samples. The system builds upon prior work that established pyrolytic conditions for online analysis and represents a significant advance in that it requires minimal preparation for samples containing as little as 1 mM sodium acetate in aqueous solution. The technique is applicable for analysis of oilfield brines, culture samples, biological samples and natural porewaters. We demonstrate its accuracy by use of a stable isotope dilution series. We also show that addition of a base and cryogenic preconcentration may induce an isotopic effect on the carboxyl carbon. This isotopic fractionation does not appear to extend to the measured methyl carbon isotope value although it can significantly alter the measured isotopic composition of the whole molecule. Our preconcentration experiments demonstrate that the method is suitable for carbon isotopic measurements of acetate methyl carbon in natural samples at concentrations as low as 90 μM, considerably broadening potential applications.     

A comparative overview of weathering intensity and HCO3 flux in the world's major rivers with emphasis on the Changjiang,Huanghe, Zhujiang (Pearl) and Mississippi Rivers

In this paper, general relationships of riverine bicarbonate concentrations and fluxes as a function of drainage basin mineral content and runoff are examined using a database of the 25 largest rivers in the world. Specific HCO₃⁻ flux normalized to unit basin area, which peaks in the mid latitudes, was found to be strongly correlated with the carbonate mineral content of river basins, while river HCO₃⁻ concentration was related to the balance of precipitation and evaporation. Within this global context, the weathering patterns of CO₂ in a few large rivers (Changjiang, Huanghe, Pearl, and Mississippi rivers) were examined in further detail. The Zhujiang (Pearl River), especially its largest branch (Xijiang), was characterized by the highest specific weathering rate among all the world's large rivers due to an exceptionally high carbonate mineral content (over 80%) in its drainage basin and its warm and wet environment. It has a moderate level of HCO₃⁻ concentration, however, due to dilution by relatively high precipitation in the watershed. In stark contrast, the Huanghe (Yellow River) has one of the lowest specific weathering rates because of low carbonate mineral content and a dry climate. However, it has a high HCO₃⁻ concentration due largely to the concentrating effects of high evaporative water loss, as a result of arid weather and the agricultural use of water through irrigation systems, as well as carbonate-containing surficial deposits (i.e., loess). The strong correlation between specific HCO₃⁻ fluxes and discharge in all four rivers with different discharge seasonality suggests that higher precipitation in drainage basins promotes higher weathering rates.     

Long-term Observations for Monitoring Extremes in the Americas

In this paper we discuss data available from Argentina, Mexico, the United States and Canada that are suitable for the analysis of extreme temperature and precipitation events. We also discuss some of the problems of homogeneity and quality control that can potentially affect the observation of extreme values. It is clear that even in countries like the United States and Canada that have a potentially rich source of climate data there are still problems in obtaining homogeneous data necessary to perform thorough studies of time varying changes in extreme events. These types of problems may be compounded if data are needed from countries that do not have a tradition of maintaining large climate archives or observing networks.We also provide two examples of analyses that can be performed with these types of data: (1) the development of climate extremes indices for Canada, and (2) analyses of freezing events for Florida and the effect on the citrus industry. The Canadian example provides a good basis for countries to take indices developed for one country or region and through minor modifications make the index relevant to their own needs. The analysis of freezing events in Florida is a timely example of how extreme events have both ecological and societal impact.     

Chaos in three-body dynamics: Kolmogorov–Sinai entropy

An ensemble of Newtonian three-body models with close initial separations is investigated by following the evolution of a 'drop' in the homology map. The onset of chaos is revealed by the motion and the complex temporal deformation of the drop. In the state of advanced chaos, the drop spreads over almost the whole homology map, quite independently of its initial position on the map. A general quantitative measure of this process is the mean exponential rate of spreading, which bears resemblance to Kolmogorov–Sinai entropy; this is introduced and estimated in terms of the homology mapping. In a similar manner we also estimate the mean exponential rate of divergence of initially close-by trajectories. This is a close analogue to the Lyapunov exponent. These parameters measure two complementary aspects of dynamical instability, which is the basic mechanism of the onset of chaos.     

Short contribution: A practical alternative to Kubiena boxes for the collection of samples for micromorphological analysis

This note proposes a practical and economical alternative to using Kubiena boxes for the collection of undisturbed soil or sediment samples for micromorphological analysis. The authors promote the use of plastic electrical outlet boxes (gang boxes) that can be purchased at any hardware store for around 20 cents apiece. In addition to availability and low cost, plastic gang boxes are preferred by thin‐section laboratories over that of the aluminum Kubiena boxes because they cause less wear on the thin‐sectioning equipment. As with Kubiena boxes, the samples are impregnated directly in the gang boxes, yet they are more easily and efficiently retrieved, thus facilitating overall sample preparation and insuring a final product of equal or better quality. © 2003 Wiley Periodicals, Inc.     

Assessment of terrestrial factors controlling the submarine groundwater discharge in water shortage and highly deformed Island of Taiwan,Western Pacific Ocean

Submarine groundwater discharge (SGD) from seventeen sites was investigated on the coasts around Taiwan in order to verify its occurrences and to understand its characteristics. The fresh water fraction (FWF) in most pore water samples, except the Fangsan sampling site, range from 0 to 59% based on the salinity evidence. The relative low FWF evidence implies that the recirculated saline groundwater discharge (RSGD) is more important than the submarine fresh groundwater discharge (SFGD) in most sampling sites. Fangsan, which is located at the southwestern coast of Taiwan, has nearly 100% FWF in SGD. Evaluation of the relationship between the magnitude of SGD flux and geological type of the Taiwanese coast proves to be difficult because complex hydrological factors affect the SGD, rather than the coastal topography. According to the hydrological evidence, the modeled-SGD discharge is enhanced by high precipitation but is generally reduced by severe groundwater pumping. In addition, modeled-SGD has an inverse relationship with river base flow, indicating the river effect. The almost fresh SGD with flow rates ranged from 34 to 42 m/year at Fangsan deserves attention because a seven-year-long groundwater budget calculation implies that the aquifer could not supply so much fresh SGD over a large area. This suggests that a significant amount of fresh water SGD at Fangsan is derived from a point source via a fault passage, considering its geological background. Although the rudimentary salinity and stable isotope results indicate that RSGD plays an important role in SGD, the type of submarine spring discharge via fault zones may very well be the most prominent in highly deformed areas elsewhere in the world, too.     

The skill of atmospheric linear inverse models in hindcasting the Madden–Julian Oscillation

A suite of statistical atmosphere-only linear inverse models of varying complexity are used to hindcast recent MJO events from the Year of Tropical Convection and the Cooperative Indian Ocean Experiment on Intraseasonal Variability/Dynamics of the Madden–Julian Oscillation mission periods, as well as over the 2000–2009 time period. Skill exists for over two weeks, competitive with the skill of some numerical models in both bivariate correlation and root-mean-squared-error scores during both observational mission periods. Skill is higher during mature Madden–Julian Oscillation conditions, as opposed to during growth phases, suggesting that growth dynamics may be more complex or non-linear since they are not as well captured by a linear model. There is little prediction skill gained by including non-leading modes of variability.     

北半球白垩纪-古近纪之交生物灭绝期孢粉地层学

长期以来,科学家们对白垩纪-古近纪(K-Pg)之交陆地上生物大灭绝事件的趋势与灭绝速率争论不断。这些争论主要集中在脊椎动物上,尤其是非鸟恐龙。尽管如此,在理解K-Pg之交的生物响应以及相关的生态系统扰动时,植被的演化也是一个重要的组成部分。本文综述北半球内白垩纪晚期至古近纪Aquilapollenites古孢粉地理大区的孢粉地层学:在美国,晚白垩世生物组合以一系列关键门类的出现为标志,其中三冬期—坎潘期过渡期以Aquilapollenites以及相关的三突起型属的出现为标志,而马斯特里赫特阶的底界以睛形型的Wodehouseia属与Kurtzipitessp.的出现为标志;Wodehouseia spinata生物组合带以较大的个体与复杂的壁构造为特征,其中一系列的被子植物孢粉单元在K-Pg之交的记录中消失了,这使得K-Pg灭绝事件容易识别;具孔类花粉和Momipites与Caryapollenites两个属的关键种的出现,标志着古近纪孢粉植物群的复苏。近期的资料涵盖了北美大陆的大部分记录,而中国、欧洲和南半球的更多研究将更有助于理解全球陆地生物圈对K-Pg之交撞击事件的响应。