Dynamics of Stream Water Quality during Snowmelt and Rainfall – Runoff Events in a Small Agricultural Catchment     

Petr Fučík  Markéta Kaplická  Tomáš Kvítek  Jana Peterková 《洁净——土壤、空气、水》2012,40(2):154-163

Surface water quality can vary a lot with fluctuating discharge during a Rainfall – runoff event. This paper uses a set of hydrological and hydrochemical variables to explain concentration–discharge loops and hysteresis of ${\rm NO}_{3}^{- } $ , ${\rm NH}_{4}^{ + } $ and total suspended solids in a brook dewatering a small upland agricultural catchment in the Czech Republic. Our study is based on data collected by a continuous monitoring approach provided by an automatic ISCO sampler both from snow thawing and rainfall – runoff events. Methods of correlation, regression and principal component analysis (PCA) were employed to reveal possible relationships among the variables. For ${\rm NO}_{3}^{- } $ and ${\rm NH}_{4}^{ + } $ , we found several types of concentration–discharge loops due to the loop rotation direction and also the loop curvature shape, in mutual combinations, no matter which type of a hydrological event it was related to. PCA indicated that ${\rm NO}_{3}^{- } $ loops correlated mostly with the length of a rising hydrograph limb and with the slope of the initial phase of a falling hydrograph limb, 5‐day amount of precipitation and runoff coefficient. In case of ${\rm NH}_{4}^{ + } $ , the concentrations usually increased with elevated discharge, whereas PCA did not detect any closer linkages. For suspended solids, an unambiguous positive monotonic relationship was discovered. Although no definite pattern was found, this study showed the necessity of a continuous water quality monitoring system as an approach for capturing and understanding relationships between solute concentrations and runoff formation for tracing and modelling catchment pollution sources and describing transport processes.  相似文献   

Politics and independent scientific advice in RFMO processes: A case study of crossing boundaries   总被引：1，自引：0，他引：1  

Tom Polacheck 《Marine Policy》2012,36(1):132-141

Provision of independent scientific advice is central to the operation of regional fisheries management organizations (RFMOs) even though RFMOs are largely policy (and political) instruments. Political pressures and intervention in science and crossing of the boundaries between scientific and political processes, however, appear to be relatively common. A case study is presented to illustrate some ways in which this occurs. It involves a paper that was withdrawn from scientific meetings of two RFMOs as a result of largely political (rather than scientific) concerns. The details involved in this incident are important for understanding the ways in which political intervention in independent scientific process can and does occur. Moreover, unless one is directly involved in actions of this kind, it is impossible from the reports of RFMOs' scientific bodies to assess whether, and the extent to which, there has been political intervention in the scientific process. It is argued that the nature of the working arrangements in these scientific committees can engender deliberate or inadvertent crossing of the boundaries between scientific independence and the political processes of RFMOs, both of which are important components of RFMO operation. Further, there is very little documentation or assessment of the generic extent of such problems. No simple solutions or reforms exist for isolating scientific advice from political agenda in the processes of RFMOs but it is suggested that increased discussion of the problem along with better understanding and clarity of the role of science in the management process may lead to improved recognition of the importance of independent scientific analyses and advice.  相似文献   

Assessment of IUU fishing for Southern Bluefin Tuna   总被引：1，自引：0，他引：1  

Tom Polacheck 《Marine Policy》2012

Illegal, unreported and unregulated (IUU) fishing is recognized as one of the largest threats to the sustainability of the world's fisheries. This paper focuses on IUU fishing in the context of unreported catches by members or co-operating non-members of regional fisheries management organizations (RFMOs) and their implications for scientific assessments of stock status and management advice. A review of Japanese market statistics was undertaken in 2006 by an independent panel in relation to catches of southern bluefin tuna (SBT). Based on this review, the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) concluded that very substantial and continuous unreported catches of SBT had been taken by longline vessels since at least the early 1990s. While uncertainty exists about the fleets contributing to these IUU catches, the assumption used within the CCSBT Scientific Committee is that a significant proportion of these were taken by Japanese longliners. Implications of these unreported catches for the stock assessments by RFMOs are discussed in light of the central role that Japanese vessel reported data have in the assessment of the world's tuna and billfish stocks. Results indicate that it is plausible that the unreported catches of SBT stem from the misreporting of catches as other tuna species and/or the location of fishing effort. The magnitude and extended period of the unreported SBT catches highlight the wide-spread risks of relying on fishery dependent logbook data in the absence of verification. An urgent need exists for minimum standards of verification of catch, effort and landing statistics for use in scientific assessments. The fisheries science community needs to be more pro-active in the development of such standards and the implementation of independent monitoring and verification. In addition, there is a need to reform the operation of the scientific bodies of RFMOs in terms of transparency, the treatment of uncertainty and the burden of proof if they are to be effective in providing objective scientific advice consistent with the intent of international agreements.  相似文献   

Modelling soil erosion with a downscaled landscape evolution model   总被引：1，自引：0，他引：1  

Tom J. Coulthard  Greg R. Hancock  John B. C. Lowry 《地球表面变化过程与地形》2012,37(10):1046-1055

The measurement and prediction of soil erosion is important for understanding both natural and disturbed landscape systems. In particular numerical models of soil erosion are important tools for managing landscapes as well as understanding how they have evolved over time. Over the last 40 years a variety of methods have been used to determine rates of soil loss from a landscape and these can be loosely categorized into empirical and physically based models. Alternatively, physically based landscape evolution models (LEMs) have been developed that provide information on soil erosion rates at much longer decadal or centennial scales, over large spatial scales and examine how they may respond to environmental and climatic changes. Both soil erosion LEMs are interested in similar outcomes (landscape development and sediment delivery) yet have quite different methodologies and parameterizations. This paper applies a LEM (the CAESAR model) for the first time at time and space scales where soil erosion models have largely been used. It tests the ability of the LEM to predict soil erosion on a 30 m experimental plot on a trial rehabilitated landform in the Northern Territory, Australia. It then continues to discuss the synergies and differences between soil erosion and LEMs. The results demonstrate that once calibrated for the site hydrology, predicted suspended sediment and bedload yields from CAESAR show a close correspondence in both volume and timing of field measured data. The model also predicts, at decadal scales, sediment loads close to that of field measured data. Findings indicate that the small‐scale drainage network that forms within these erosion plots is an important control on the timing and magnitude of sediment delivery. Therefore, it is important to use models that can alter the DEM to reflect changing topography and drainage network as well as having a greater emphasis on channel processes. Copyright © 2012 John Wiley & Sons, Ltd. and Commonwealth of Australia  相似文献   

Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups     

Holmes AL  Wise SS  Goertz CE  Dunn JL  Gulland FM  Gelatt T  Beckmen KB  Burek K  Atkinson S  Bozza M  Taylor R  Zheng T  Zhang Y  Aboueissa AM  Wise JP 《Marine pollution bulletin》2008,56(8):1416-1421

The endangered Western population of the Steller sea lion declined for three decades for uncertain reasons. We present baseline data of metal concentrations in pups as a first step towards investigating the potential threat of developmental exposures to contaminants. Seven metals were investigated: arsenic, cadmium, silver, aluminum, mercury, lead and vanadium. Vanadium was detected in only a single blubber sample. Mercury appears to be the most toxicologically significant metal with concentrations in the liver well above the current action level for mercury in fish. The concentrations of aluminum, arsenic, silver, cadmium and lead were present in one-fourth to two-thirds of all samples and were at either comparable or below concentrations previously reported. Neither gender nor region had a significant effect on metal burdens. Future work should consider metal concentrations in juveniles and adults and toxicological studies need to be performed to begin to assess the toxicity of these metals.  相似文献   

Timescales of geological processes: Preface     

Andrew Putnis  Christopher J. Spencer  Tom Raimondo 《地学前缘(英文版)》2019,10(1):1-3

正1. Introduction One of the major challenges in Geoscience is to understand how the formation and evolution of the Earth System are governed by timescales e that is, how the various geological processes that continue to contribute to its present-day structure and composition operated in the deep past. The traditional view of such processes refers to events that occur at immense spatial scales and over hundreds of millions of years, constrained in most cases by the ages of rocks determined using isotopic dating methods or the fossil record. However, the modern view of geological processes has increasingly acknowledged that their durations can be significantly shorter than previously thought possible, or indeed detectable  相似文献   

Iron-stimulated growth and microcystin production of Microcystis novacekii UAM 250     

Hongli Li  Tom Murphy  Jay Guo  Tanya Parr  Czesia Nalewajko 《Limnologica》2009,39(3):255-259

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Assessment of oxygen plasma ashing as a pre-treatment for radiocarbon dating     

Michael I. Bird  Peter D.J. Charville-Mort  Philippa L. Ascough  Rachel Wood  Tom Higham  David Apperley 《Quaternary Geochronology》2010,5(4):435-442

This study investigates the potential of low-temperature oxygen plasma ashing as a technique for decontaminating charcoal and wood samples prior to radiocarbon dating. Plasma ashing is demonstrated to be rapid, controllable and surface-specific. Different organic materials clearly ash at different rates, however, the ability of plasma ashing to selectively ash different organic components is limited in heterogeneous sample matrices. This is because oxidation is confined to the immediate sample surface. Comparison of radiocarbon dates obtained from identical aliquots of contaminated ancient charcoal pre-treated by acid–base–acid (ABA), acid–base-oxidation-stepped combustion (ABOx-SC) and plasma ashing suggests that the technique performs as well as the ABA pre-treatment but does not remove as much contamination as the ABOx-SC technique. Plasma ashing may be particularly useful in cases where sample size is limiting.  相似文献   

Coupled Aquifer-Borehole Simulation     

by Tom Clemo 《Ground water》2010,48(1):68-78

A model coupling fluid hydraulics in a borehole with fluid flow in an aquifer is developed in this paper. Conservation of momentum is used to create a one-dimensional steady-state model of vertical flow in an open borehole combined with radially symmetric flow in an aquifer and with inflow to the well through the wellbore screen. Both laminar and turbulent wellbore conditions are treated. The influence of inflow through the wellbore screen on vertical flow in the wellbore is included, using a relation developed by Siwoń (1987) . The influence of inflow reduces the predicted vertical variation in head up to 15% compared to a calculation of head losses due to fluid acceleration and the conventional Colebrook-White formulation of friction losses in a circular pipe. The wellbore flow model is embedded into the MODFLOW-2000 ground water flow code. The nonlinear conservation of momentum equations are iteratively linearized to calculate the conductance terms for vertical flow in the wellbore. The resulting simulations agree favorably with previously published results when the model is adjusted to meet the assumptions of the previous coupled models.  相似文献   

Siliceous Cementation of Chlorite-Coated Grains in the Permian Sandstone Gas Reservoirs, Ordos Basin     

FAN Aiping  YANG Renchao  LI Jinbu  ZHAO Zhongjun  A.J. 《《地质学报》英文版》2017,91(3):1147-1148

<正>Objective It has long been controversial that whether authigenic chlorite coatings in sandstone reservoirs can prevent precipitation of siliceous cements.It is commonly believed that chlorite coatings(also called chlorite films,chlorite linings,or chlorite rims)may prevent quartz overgrowth,and thus help the preservation of original pores in sandstone reservoirs.Recently,however,this assumption has been challenged by reservoir geologists.This dispute cannot be solved by mere analysis of thin sections,nor by chemical equations and diagenesis analysis.The main objective of the present contribution is to shed light on this  相似文献