Effects of vegetation cover on runoff and erosion under simulated rain and overland flow on a rehabilitated site on the Meandu Mine, Tarong, Queensland

This research was carried out to quantify the role of vegetative cover in reducing runoff and erosion from rehabilitated mined land. Duplicate plots 1.5 m wide and 12 m long were prepared on a rehabilitated area of the Meandu Mine, Tarong, with vegetative cover of 0, 23%, 37%, 47%, and 100%. The area had a uniform 15% slope, and there were no rill or gully lines present. Simulated rain equivalent to a 1 : 100 year storm was applied to the plots, and runoff and erosion were measured. Infiltration totals and rates increased strongly with increasing vegetative cover. There was visibly greater infiltration under vegetation. Erosion from the simulated storm was greatly reduced by vegetative cover, declining from 30–35 t/ha at 0% vegetative cover to 0.5 t/ha at 47% cover. Reductions in erosion at lower levels of vegetative cover were greater than predicted by the cover/erosion relationship used in the USLE. The dominantly stoloniferous growth habit of the grass at this site may have increased the effectiveness of vegetative cover in this study. To allow the data to be extrapolated to slopes longer than 12 m, a series of overland flows were applied to the upslope boundaries of the plots, simulating flows on slopes up to 70 m long. Detachment and transport of sediment by applied overland flow was similarly reduced by vegetative cover, and results from the overland flow study also indicate that for slopes up to 70 m long with grass cover of 47% or greater, erosion rates will be minimal, even under extreme rainfall/runoff events

Measurement of aggregate breakdown under rain: Comparison with tests of water stability and relationships with field measurements of infiltration

This paper reports comparisons between aggregate breakdown on wetting by rainfall with breakdown measured by a range of alternative methods. It also reports correlations between measured breakdown and steady infiltration rates of simulated rain of high and low energy, and hydraulic conductivities of surface seal layers formed under high energy rain. A wide range of soils in eastern Australia were studied. Highly significant correlations were found between measurements of aggregate breakdown to < 125 µm caused by rainfall wetting and both steady infiltration rates and hydraulic conductivities. Significant, but poorer correlations were found between steady infiltration rates and breakdown resulting from immersion wetting. Deletion of swelling soils from the data set greatly improved correlations between steady infiltration rates of high energy rain and breakdown measured by both immersion and tension wetting, showing that these methods of wetting ace particularly inappropriate for swelling soils. No correlation was found between infiltration rates and measured clay dispersion. Different relationships between the proportion of particles (%) < 125 µm at the soil surface (P125) and steady infiltration rates of low and high energy rain indicated that compaction of the soil surface layer, rather than increased aggregate breakdown, is a major cause of surface sealing by raindrop impacts. Measurements of fall cone penetration confirmed that drop impacts had compacted the surface layer. Suctions across the surface seal were related to P125 in that layer, and the relationship obtained was used in calculating hydraulic conductivities. The results confirm that measurement of aggregate breakdown under rainfall wetting produces results of much greater relevance to soil behaviour under field conditions than do tests based on immersion and tension wetting

Differences in mineral concentration among diploid and tetraploid cultivars of rhodesgrass (Chloris gayana)

Mineral composition of a range of rhodesgrass cultivars was measured to assess if levels were suitable for cattle growth. Leafy regrowth of 11 rhodesgrass cultivars and lines was analysed for a range of elements in 2 replicated field experiments near Gympie in southern Queensland. Experiment 1 comprised 2 diploid and 2 tetraploid cultivars, while 7 diploids and 3 tetraploids were compared in experiment 2.Overall, the tetraploids had higher nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) concentrations but lower sodium (Na) and boron (B) concentrations than the diploids. Concentrations of potassium (P), copper (Cu) and aluminium (Al) for the 2 groups were similar and showed no significant cultivar differences. Results for sulfur (S), zinc (Zn) and iron (Fe) varied between experiments, either with no significant ploidy and cultivar differences or with higher concentrations in the tetraploids (S in experiment 2, Zn in experiment 1). The tetraploids had significantly higher concentrations of Mn in experiment 2. The Na concentration found in cultivar Boma was lower (0.02%) than the other cultivars in experiment 2. Similarly, cultivar Samford in experiment 1 had a lower Na concentration than the other 3 cultivars. Both Boma and Samford, however, had the highest Mg concentrations in their respective experiments. K/(Ca+ Mg) equivalent ratios in the 2 experiments were in the range 0.40-1.50. This is well below the accepted critical value of 2.2 above which grass tetany in ruminants could become a problem

Evaluation of the potential to dispose of sewage-sludge. 2. Potential for off-site movements of solids and solutes

This paper reports a study of the potential for off-site movements of pollutants from sewage sludge broadcast onto the soil surface in Pinus plantations established on the coastal lowlands of south-east Queensland. Laboratory studies of size and settling velocity distributions of rainfall-wetted sludge showed that it is relatively coarse and non-erodible. Field rainfall simulation studies at three sites in pine forests near Beerburrum found no significant increase in interrill erosion due to broadcasting of sludge. (Most or all of the sediment was observed to come from mineral soil exposed when a gutter to collect runoff was installed at the downslope ends of the plots.) However, there was considerable movement of solutes in runoff from rainfall simulator plots that had received sludge-either freshly applied or 'consolidated' sludge (that had been broadcast on the plots 6 months prior to the rainfall simulation study and exposed to rain and weathering). Electrical conductivity (EC) of runoff from freshly applied sludge was initially high but decreased steadily during the 30 min rainfall event. Runoff from consolidated sludge had lower ECs, though significantly (P < 0.05) higher than those of runoff from control plots. Concentrations of nitrate-N and ammonium-N were initially high in runoff from freshly applied sludge, but decreased rapidly during the rainfall event. In contrast, concentrations of mineral N in runoff from consolidated sludge were low throughout the rainfall event. These results indicate a significant risk of off-site N pollution if runoff occurs during the first rains following broadcasting of sludge. By contrast, concentrations of total phosphorus, copper, and zinc in runoff from both fresh and consolidated sludge were relatively high, and showed only small decreases during the rainfall event applied. This suggests that sludge will contribute significant quantities of these elements to runoff for extended periods after broadcasting. The implications of these findings become important in terms of the timing and method of sludge application to the soil

Estimation of erosion model erodibility parameters from media properties

The aim of this research was to enable erodibility values for hillslope-scale erosion prediction models to be determined from easily measured media properties. Simulated rainfall and overland flow experiments were carried out on 34 soils and overburdens from 15 Queensland open-cut coal mines at The University of Queensland Erosion Processes Laboratory. Properties of the 34 media determined included aggregate stability, Atterberg limits, bulk density, cation exchange capacity, dispersion ratios, electrical conductivity, exchangeable sodium percentage, organic carbon content, pH, texture, and water content at field capacity and wilting point. Correlation and stepwise multiple regression procedures were used to determine those media properties that could best be used to predict rill and interill erodibility. Correlations between media properties and sediment delivery at each of 5, 10, 15, 20, and 30% slope revealed that different media properties were correlated with erosion rates at different slopes. A media property could show a strong correlation with erodibility at 30% slope, and a low correlation at 5% slope. Splitting the data set into soils only, and overburdens only, showed that properties that were positively correlated with erosion rates for one group could be negatively correlated for the other group. Therefore, in this study, erodibility could not be explicitly linked to one set of media properties for all medium types and erosive conditions. It was concluded that a single regression equation could not be used to predict erodibility under all conditions. Instead, 4 equations were developed to predict rill and interill erodibility, for soils and overburdens separately. The need for separate regression equations was attributed to the presence of different erosive sub-processes for specific combinations of medium type and slope gradient

Evaluation of the potential to dispose of sewage-sludge. 1. Soil hydraulic and overland-flow properties of Pinus plantations in Queensland

The studies reported in this paper were designed to evaluate the potential for disposal of sewage sludge in commercial Pinus plantations at Beerburrum, 50 km north of Brisbane. Soil descriptions and measurements of hydraulic properties were made in three soils, covering the range of perceived site suitability for sludge application. Disc permeameters and a rainfall simulator were used to characterize surface infiltration properties both with and without sludge, and ponded rings were used to assess permeability of the upper B horizon. Although surface hydraulic conductivities were potentially high, infiltration into dry soil was reduced by water repellence associated with fungal matting at the soil surface and mycelia extending through the Al horizon. Surface runoff could be generated from dry soils by relatively low intensity rainfall events, and the rate and volume of runoff was not increased by broadcast sludge application. Hydraulic conductivities of the upper Bt horizons in the lateritic and yellow podzolic soils were high, suggesting that persistent perched watertable development was unlikely. However, the presence of bleached A2 horizons and gleyed Bt horizons with prominent mottling in these soils were interpreted as evidence of periodic regional ground-water intrusion. By contrast, hydraulic conductivity in the Bt horizon of the soloth was low, suggesting that locally restricted drainage occurs. Likely pathways of water movement were inferred for three representative soil types in the proposed sludge application project. There is potential for both Hortonian runoff when antecedent conditions are dry, and saturated runoff during prolonged wet periods. Potential off-site pollution could therefore occur if either solids or solutes from the sludge are susceptible to transport. In addition, preferential how paths of water infiltration were demonstrated, and the potential for accelerated water and solute movement to ground watertables was inferred. The studies reported in this, and the second, paper in the series were used to appraise the potential for either surface water or ground water pollution from land-based sludge disposal

Use of laboratory-scale rill and interill erodibility measurements for the prediction of hillslope-scale erosion on rehabilitated coal mine soils and overburdens

Prediction of hillslope-scale soil erosion traditionally involves extensive data collection from field plots under natural rainfall, or from field rainfall simulation programs. Recognising the high costs and inconvenience associated with field-based studies, a method was developed and tested for predicting hillslope-scale soil erosion from laboratory-scale measurements of erodibility. A laboratory tilting flume and rainfall simulator were used to determine rill and interill erodibility coefficients for 32 soils and overburdens from Queensland open-cut coal mines. Predicted sediment delivery rates based on laboratory determinations of erodibility were tested against field measurements of erosion from 12-m-long plots under simulated rainfall at 100 mm/h on slopes ranging from 5% to 30%. Regression analysis demonstrated a strong relationship between predicted and measured sediment delivery rates, giving an r2 value of up to 0.74, depending on the particular modeling approach used. These results demonstrate that soil losses due to the combined processes of rill and interill erosion at the hillslope scale can successfully be predicted from laboratory-scale measurements of erodibility, provided a suitable methodology and modelling approach is adopted. The success of this approach will greatly reduce the cost and effort required for prediction of hillslope scale soil erosion

Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA

An investigation of the hadronic final state in diffractive and non--diffractive deep--inelastic electron--proton scattering at HERA is presented, where diffractive data are selected experimentally by demanding a large gap in pseudo --rapidity around the proton remnant direction. The transverse energy flow in the hadronic final state is evaluated using a set of estimators which quantify topological properties. Using available Monte Carlo QCD calculations, it is demonstrated that the final state in diffractive DIS exhibits the features expected if the interaction is interpreted as the scattering of an electron off a current quark with associated effects of perturbative QCD. A model in which deep--inelastic diffraction is taken to be the exchange of a pomeron with partonic structure is found to reproduce the measurements well. Models for deep--inelastic $ep$ scattering, in which a sizeable diffractive contribution is present because of non--perturbative effects in the production of the hadronic final state, reproduce the general tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter