Suspended sediment transport and deposition over a dune: Río Paraná, Argentina     

Ray Kostaschuk  Dan Shugar  Jim Best  Dan Parsons  Stuart Lane  Rich Hardy  Oscar Orfeo 《地球表面变化过程与地形》2009,34(12):1605-1611

Field data from the Rio Paraná, Argentina, are used to examine patterns of suspended sediment transport over a sand dune. Measurements of three‐dimensional velocity are made with an acoustic Doppler current profiler whilst suspended sediment concentration and particle size have been quantified using a laser in situ sediment scattering transmissometer. Suspended sediment concentration and streamwise and vertical sediment flux are highest close to the bed, with an upward vertical flux over the stoss side of the dune and downward flux over the lee side. Suspended sediment concentrations are higher over the crest compared with the trough and suspended sediment is coarsest near the bed. About 17% of the suspended‐load transported over the crest is deposited in the lee side before it reaches the trough. Most of this deposited sand is coarser sediment that originates close to the bed over the crest, a result consistent with simulations based on the model of Mohrig and Smith (Water Resources Research 1996; 32: 3207–3217) for the excursion lengths of sediment dispersed in the lee side of a dune. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Does quantifying antecedent flow conditions improve stream phosphorus export estimation?     

Stuart Warner  Gerard Kiely  Gerard Morgan  John O&#x;Halloran 《Journal of Hydrology》2009,378(1-2):97-104

A reliable and economical method for the estimation of nutrient export (e.g. phosphorus) in stream flow from catchments is necessary to quantify the impact of land use or land use change upon aquatic systems. The transport of phosphorus (P) from soil to water is known to impact negatively on water quality. A key observation from studies is that most P export occurs during high stream flow. However, it is not yet clear how flood-antecedent conditions affect the P export during flood events. In this study, the P loss from soil to water as represented by soluble reactive phosphorus (SRP) in stream waters from three different catchments, varying in land use, scale and location in Ireland was monitored over 1 year. This study examined the role of antecedent stream flow conditions on SRP export and identifies a catchment-specific relationship between SRP flood event load (EL) and a flow ratio (FR). The FR is defined as the ratio of the flood event volume (EV) to the pre-event volume (PEV). The latter is the cumulative flow volume for a number of days preceding the event. This PEV period was found to be longer (average 81 days) in the grassland catchments which were known to be saturated with soil P than in the forested catchments (average 21 days) with minimal soil P. This FR ratio is a measure of the antecedent hydrological state (wet or dry) of the catchment. For SRP for each catchment, a specific relationship between SRP EL and FR was identified. The annual SRP export was estimated, using this ratio and compared with the concentration/discharge (C/Q) method. The new flow ratio method was used with data from 12 flood events during the year to estimate an annual export of SRP. For the two grassland catchments in the study, using the FR method, we estimated an SRP export of 1.77 and 0.41 kg ha⁻¹ yr⁻¹. Using the C/Q method, for the same sites, our estimate of SRP export was 1.70 and 0.50 kg ha⁻¹ yr⁻¹ respectively. The C/Q method used SRP concentrations covering 40% of the year while the FR method used only 12 flood events covering less than 2% of the year. This new method which takes account of the antecedent flow state of the river is an alternative to and may be more promising than the traditional C/Q method, particularly when short duration or flood sampling of water quality is carried out.  相似文献   

Development of guidelines for ammonia in estuarine and marine water systems   总被引：1，自引：0，他引：1  

Graeme E. Batley  Stuart L. Simpson 《Marine pollution bulletin》2009,58(10):1472-1476

The water quality guideline trigger value for ammonia in estuarine and marine waters has been revised with the addition of 38 new results to the data set of 21 used in earlier guideline derivations. Using species sensitivity distributions, a new trigger value of 460 μg total NH₃-N/L was derived for slightly to moderately disturbed systems (95% protection concentration, PC95), with a value of 160 μg total NH₃-N/L applying to waters of high conservation value (PC99). For sediment pore waters, a guideline trigger value of 3.9 mg total NH₃-N/L, derived from the 80th percentile of background data from Sydney Harbour, is recommended. This value is likely to be exceeded in degraded sediments subject to dredging; however, ocean disposal of such sediments results in rapid decreases in porewater ammonia and a guideline trigger value for dissolved ammonia during disposal of dredged sediments of 1550 μg total NH₃-N/L is proposed.  相似文献   

Reply to comment by W.U. Reimold, R.L. Gibson, and H. Henkel on Muundjua et al. (2007), “Magnetic imaging of the Vredefort impact crater, South Africa”, EPSL 261, pp 456–468     

Manfriedt Muundjua  Armand Galdeano  Laurent Carporzen  Stuart A. Gilder  Rodger J. Hart  Marco A.G. Andreoli  Marian Tredoux 《Earth and Planetary Science Letters》2008,273(3-4):397-399

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Long periods of boredom interspersed by brief moments of terror?     

Stuart Lane 《地球表面变化过程与地形》2008,33(1):1-3

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Target strength of southern blue whiting (Micromesistius australis) using swimbladder modelling, split beam and deconvolution     

McClatchie  Sam; Macaulay  Gavin; Hanchet  Stuart; Coombs  Roger F. 《ICES Journal of Marine Science》1998,55(3):482-493

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