The influence of a season of extreme wet weather events on exposure of the World Heritage Area Great Barrier Reef to pesticides     

Kennedy K  Devlin M  Bentley C  Lee-Chue K  Paxman C  Carter S  Lewis SE  Brodie J  Guy E  Vardy S  Martin KC  Jones A  Packett R  Mueller JF 《Marine pollution bulletin》2012,64(7):1495-1507

The 2010-2011 wet season was one of extreme weather for the State of Queensland, Australia. Major rivers adjacent to the Great Barrier Reef (GBR) were discharging at rates 1.5 to >3 times higher than their long term median. Exposure to photosystem II herbicides has been routinely monitored over a period of up to 5 years at 12 inshore GBR sites. The influence of this wet season on exposure to photosystem II herbicides was examined in the context of this long-term monitoring record and during flood plume events in specific regions. Median exposures expressed as diuron equivalent concentration were an average factor of 2.3 times higher but mostly not significantly different (p<0.05) to the median for the long-term monitoring record. The herbicides metolachlor and tebuthiuron were frequently detected in flood plume waters at concentrations that reached or exceeded relevant water quality guidelines (by up to 4.5 times).  相似文献   

A thermochemical boundary layer at the base of Earth's outer core and independent estimate of core heat flux     

David Gubbins  Guy Masters  Francis Nimmo 《Geophysical Journal International》2008,174(3):1007-1018

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Landform classification from a digital elevation model and satellite imagery   总被引：4，自引：0，他引：4  

Hossein Saadat  Robert Bonnell  Forood Sharifi  Guy Mehuys  Mohammad Namdar  Sasan Ale-Ebrahim 《Geomorphology》2008,100(3-4):453-464

The Iranian Soil and Water Research Institute has been involved in mapping the soils of Iran and classifying landforms for the last 60 years. However, the accuracy of traditional landform maps is very low (about 55%). To date, aerial photographs and topographic maps have been used for landform classification studies. The principal objective of this research is to propose a quantitative approach for landform classification based on a 10-m resolution digital elevation model (DEM) and some use of an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image. In order to extract and identify the various landforms, slope, elevation range, and stream network pattern were used as basic identifying parameters. These are extractable from a DEM. Further, ASTER images were required to identify the general outline shape of a landform type and the presence or absence of gravel. This study encompassed a relatively large watershed of 451 183 ha with a total elevation difference of 2445 m and a variety of landforms from flat River Alluvial Plains to steep mountains. Classification accuracy ranged from 91.8 to 99.6% with an average of 96.7% based upon extensive ground-truthing. Since similar digital and ASTER image information is available for Iran, an accurate landform map can now be produced for the whole country. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world.  相似文献   

Denudation rates on cratonic landscapes: comparison between suspended and dissolved fluxes,and 10Be analysis in the Nyong and Sanaga River basins,south Cameroon          下载免费PDF全文

Vincent Regard  Sébastien Carretier  Jean‐Loup Boeglin  Jules‐Rémy Ndam Ngoupayou  Jean‐Guy Dzana  Jean‐Pierre Bedimo Bedimo  Jean Riotte  Jean‐Jacques Braun 《地球表面变化过程与地形》2016,41(12):1671-1683

South Cameroon is located in a tropical and tectonically quiescent region, with landscapes characterized by thick highly weathered regolith, indicative of the long‐term predominance of chemical weathering over erosion. Currently this region undergoes huge changes due to accelerated mutations related to a growing population and economical developments with associated needs and increasing pressures on land and natural resources. We analysed two of the main south Cameroon rivers: the Nyong River and Sanaga River. The Sanaga catchment undergoes a contrasted tropical climate from sub‐humid mountainous and humid climate and is impacted by deforestation, agriculture, damming, mining and urbanization, especially in the Mbam sub‐basin, draining the highly populated volcanic highlands. By contrast, the Nyong catchment, only under humid tropical climate, is preserved from anthropogenic disturbance with low population except in the region of Yaoundé (Méfou sub‐basin). Moreover the Nyong basin is dam‐free and less impacted by agriculture and logging. We explore both denudation temporal variability and the ratio between chemical and physical denudation through two catchment‐averaged erosion and denudation datasets. The first one consists of an 11‐year long gauging dataset, while the second one comes from cosmogenic radionuclides [CRNs, here beryllium‐10 (¹⁰Be)] from sand sampled in the river mainstreams (timescale of tens to hundreds of thousands of years). Modern fluxes estimated from gauging data range from 5 to 100 m/Ma (10 to 200 t/km²/yr); our calculations indicate that the usual relative contribution of chemical versus physical denudation is 60% and 40%, respectively, of the total denudation. Beryllium‐10 denudation rates and sediment fluxes range from 4.8 to 40.3 m/Ma or 13 to 109 t/km²/yr, respectively, after correction for quartz enrichment. These fluxes are slightly less than the modern fluxes observed in Cameroon and other stable tropical areas. The highest ¹⁰Be‐derived fluxes and the highest physical versus chemical denudation ratios are attributed to anthropogenic impact. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Dependence of radar quantitative precipitation estimation error on the rain intensity in the Cévennes region,France     

Guy Delrieu  Laurent Bonnifait  Pierre-Emmanuel Kirstetter  Brice Boudevillain 《水文科学杂志》2014,59(7):1308-1319

Abstract

Radar quantitative precipitation estimates (QPEs) were assessed using reference values established by means of a geostatistical approach. The reference values were estimated from raingauge data using the block kriging technique, and the reference meshes were selected on the basis of the kriging estimation variance. Agreement between radar QPEs and reference rain amounts was shown to increase slightly with the space–time scales. The statistical distributions of the errors were modelled conditionally with respect to several factors using the GAMLSS approach. The conditional bias of the errors presents a complex structure that depends on the space–time scales and the considered geographical sub-domains, while the standard deviation of the errors has a more homogeneous behaviour. The estimation standard deviation of the reference rainfall and the standard deviation of the errors between radar and reference rainfall were found to have the same magnitude, indicating the limitations of the available network in terms of providing accurate reference values for the spatial scales considered (5–100 km²).