Enhancing RUSLE to include runoff‐driven phenomena

RUSLE2 (Revised Universal Soil Loss Equation) is the most recent in the family of Universal Soil Loss Equation (USLE)/RUSLE/RUSLE2 models proven to provide robust estimates of average annual sheet and rill erosion from a wide range of land use, soil, and climatic conditions. RUSLE2's capabilities have been expanded over earlier versions using methods of estimating time‐varying runoff and process‐based sediment transport routines so that it can estimate sediment transport/deposition/delivery on complex hillslopes. In this report we propose and evaluate a method of predicting a series of representative runoff events whose sizes, durations, and timings are estimated from information already in the RUSLE2 database. The methods were derived from analysis of 30‐year simulations using a widely accepted climate generator and runoff model and were validated against additional independent simulations not used in developing the index events, as well as against long‐term measured monthly rainfall/runoff sets. Comparison of measured and RUSLE2‐predicted monthly runoff suggested that the procedures outlined may underestimate plot‐scale runoff during periods of the year with greater than average rainfall intensity, and a modification to improve predictions was developed. In order to illustrate the potential of coupling RUSLE2 with a process‐based channel erosion model, the resulting set of representative storms was used as an input to the channel routines used in Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) to calculate ephemeral gully erosion. The method was applied to a hypothetical 5‐ha field cropped to cotton in Marshall County, MS, bisected by a potential ephemeral gully having channel slopes ranging from 0·5 to 5% and with hillslopes on both sides of the channel with 5% steepness and 22·1 m length. Results showed the representative storm sequence produced reasonable results in CREAMS indicating that ephemeral gully erosion may be of the same order of magnitude as sheet and rill erosion. Copyright © 2010 John Wiley & Sons, Ltd.     

Irregular Satellites of Jupiter: a study of the capture direction

The irregular satellites of Jupiter are believed to be captured asteroids or planetesimals. In the present work is studied the direction of capture of these objects as a function of their orbital inclination. We performed numerical simulations of the restricted three-body problem, Sun-Jupiter-particle, taking into account the growth of Jupiter. The integration was made backward in time. Initially, the particles have orbits as satellites of Jupiter, which has its present mass. Then, the system evolved with Jupiter losing mass and the satellites escaping from the planet. The reverse of the escape direction corresponds to the capture direction. The results show that the Lagrangian points L1 and L2 mainly guide the direction of capture. Prograde satellites are captured through these two gates with very narrow amplitude angles. In the case of retrograde satellites, these two gates are wider. The capture region increases as the orbital inclination increases. In the case of planar retrograde satellites the directions of capture cover the whole 360° around Jupiter. We also verified that prograde satellites are captured earlier in actual time than retrograde ones. This paper was presented at the Asteriods, Comets and Meteors meeting held at Búzios, Rio de Janeiro, Brazil in August 2005 and could not be included in the special issue related to that conference.     

Direct dating of the Sete Lagoas cap carbonate (Bambuí Group,Brazil) and implications for the Neoproterozoic glacial events

The end of the Neoproterozoic is punctuated by glacial deposition, but the chronology of these deposits is hindered presently by the paucity of geochronological data. Here, we present new radiometric dating for the basal Sete Lagoas cap carbonate deposits that overlie glacial units in the São Francisco craton. Six samples from aragonite‐pseudomorph crystal‐rich facies, showing pristine textures and constant ⁸⁷Sr/⁸⁶Sr ratios around 0.7075, yielded a Pb–Pb isochron age of 740 ± 22 Ma, which is interpreted as the depositional age for these remarkably preserved rocks. This age can be used to infer a low‐to‐moderate palaeolatitude of 20–30° for carbonate (and glacial) deposition. In addition, as it overlaps the ages obtained for the oldest Neoproterozoic glacial successions, our result reinforces the idea of a long‐standing ‘Sturtian’ interval, suggesting that this event represents either different discrete glaciations or a protracted event encompassing almost 80 Ma.     

Impact of the past mining activity in Roşia Montană (Romania) on soil and vegetation

The paper presents the results of a combined soil and vegetation survey in Ro?ia Montan? mining area (western Romania), famous for its gold and silver deposits, extensively exploited over the last 2,000 years. As the ore extraction has ceased in 2006 and new operations could be initiated in the future, the study contributes to the definition of the environmental baseline. Samples of topsoil and leaves of the tree species Betula pendula and Carpinus betulus have been collected from the inside and outside of the mining area, on a total surface of more than 60 km². The pH and heavy metal concentrations (Cd, Cr, Cu, Ni, Pb, and Zn) have been measured on 262 soils/sediments samples, revealing the predominantly acidic character of soils and the generally low contents of heavy metals. Stronger acidity and higher contents of heavy metals have been noticed in the proximity of the mining site, on the tailings and waste rock dumps, and along the streams with acid water. More than 100 leaf samples have been analysed for the same heavy metals as soils and also for chlorophyll fluorescence and pigment concentrations. B. pendula has shown a particular ability to concentrate Zn in leaves, at levels that may greatly exceed the Zn content in the corresponding soil samples. The correlation between the heavy metal contents in leaves and in soils, in most of the cases, is not very strong, presumably in relation to the low concentrations in soils. The chlorophyll concentration in leaves of B. pendula slightly diminishes on soils with low pH.     

Water reservoirs and the risk of accidental flood occurrence. Case study: Stanca–Costesti reservoir and the historical floods of the Prut river in the period July–August 2008, Romania

In the summer of 2008 the Prut river recorded a historical flow of 7140 m³/s at its entrance into Romania. This flow was the highest ever recorded of any Romanian river. The high value was generated by high amounts of rainfall recorded first on the territory of Ukraine and then in Romania. Unfortunately, there were some discrepancies between the data transmitted and intercepted from the Meteorology National Agency and Hydrology and Water Management National Agency. This is why the amount of precipitation which fell over the territory of Ukraine could not be monitored in time and punctually. Nor could the high flood wave moving rapidly from the upper basin to the lower basin. The high flow of the upper Prut caused the accumulation of an immense quantity of water in the Stanca–Costesti reservoir. Under the conditions of precipitation occurring in the lower river basin as well, the levels reached the flood quota and the reservoir reached the maximum accepted capacity, with 0·1% insurance. The release of supplementary water quantities from the reservoir would have produced catastrophic floods downstream. Keeping the water in the reservoir could have broken it and the flooding, through backwater eddies, or the riverbank settlements. In such a case, it would have produced the greatest tragedy in the hydrological history of Europe. The most significant damage was produced upstream of the barrage, next to the localities of Radauti Prut and Baranca–Hudesti, as well as in the area of the reservoir, as a result of the phenomenon known as ‘remuu’, or backwater eddies. The floods of the Prut river occurred between the end of July and the end of August. Copyright © 2011 John Wiley & Sons, Ltd.     

Study of a neutral hydrogen feature previously observed by Cugnon

An anomalous velocity cloud nearl=349°,b=+3°, was investigated by Cugnon (1968). The authors made a new set of observations in order to obtain a more complete picture of the feature, including the region originally out of Cugnon's limit of observation. A comparison with optical and radio observations was made and several possibilities of interpretation as to the nature of the object were analyzed.     

Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico

The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident.