Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements

Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated V_s and borehole measured V_s in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived V_s values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis.     

Thermal, seismic and infrasonic evidences of variable degassing rates at Stromboli volcano

During June 1999, we measured the amplitude and rate (number of events per second) at which gas exited the vent at Stromboli volcano as discrete gas bursts or puffs. This allowed us to identify two styles of gas burst (puffing) activity. The first is characterized by frequent, rapidly rising puffs, the second by less frequent, slowly rising puffs. Each style persisted over 5–40-min-long durations and was associated with a high and low number of strombolian explosions per hour, respectively. Each period was also associated with characteristic delay times between the arrival of the infrasonic and thermal signals during strombolian explosions; the delays were longer during vigorous puffing periods. To explain our observations, we propose a model in which the degassing process cycles between vigorous and weak degassing phases. During vigorous degassing phases, bubble layers ascend the conduit at a frequency of 0.5–1.0 s⁻¹. This high degassing level reflects a gas-rich magma column and leads to an increased rate in the formation of shallow foams and, hence, an increase in puffing and explosive activity, as well as a higher free surface level and/or gas jet velocity. During weak phases, bubble layers ascend the conduit at a reduced frequency of 0.2–0.3 s⁻¹. During such times the magma column is poor in gas. This leads to a decreased rate of foam layer formation and hence a reduction in puffing and explosive activity, as well as a lower free surface level and/or gas jet velocity. Variations in puffing activity can thus be used to track changes in the rate at which the shallow system is supplied by fresh, gas-rich magma. Our observations indicate that the two degassing styles last from 5 to 40 min and that the switch from one to the other occurs over a matter of minutes.     

Multiphase models of flotation machine behaviour

Models in which the cell contents are partitioned into distinct pulp and froth phases are reviewed critically. The nature of the mixing within the phases is discussed. Multiphase models describing froth column concentration gradients and pulp residence time effects are mentioned. It is shown that at steady state multiphase models can be reduced to the two-phase case. Deficiencies in the models and topics requiring further development are outlined.     

The effect of petroleum hydrocarbons on reproduction of an estuarine planktonic copepod in laboratory cultures

The effect of short-term exposure to high concentration (mg l.^?1) of water soluble fraction of aromatic heating oil on subsequent egg production by the estuarine copepod Eurytemora affinis has been studied in laboratory cultures to investigate possibly sublethal biological effects following exposure to hydrocarbon under an oil spill. Significant reduction in subsequent length of life, total number of eggs produced, mean brood size, and rate of egg production was observed. Exposure to naphthalene alone at 1 mg l.^?1 for 24 h produced a significant effect on total fecundity of the females. Ingestion rates were significantly lower when measured in the presence of the water soluble fraction, and also naphthalene alone at mg l.^?1 concentrations. Exposure to low-levels (10 and 50 μg l.^?1) of ¹⁴C-naphthalene alone over a period of ten days produced no significant effect on feeding or reproduction despite the high concentrations of hydrocarbon accumulated during this period. The results are discussed in relation to previous work on the fate of hydrocarbons in planktonic copepods, using ¹⁴C-1-naphthalene as a model compound.     

The air flow number in flotation machine scale-up

The flotation cell is quantified as a mixing device for one, two, and three phase systems using combinations of water, air, and solids. To do this, power consumption was measured as a function of impeller speed, rate of aeration, and solids concentration. Initial suspension of solids and dispersion of suspended solids throughout the water or water/air system were also studied as influenced by impeller speed, particle size and solids concentration. The power number and air flow number were used to correlate the data.Flotation studies with a zinc ore using three sizes of cells of the same design, showed that aeration had to be controlled in the smaller cells to duplicate the results in the cell of commercial size. For optimum results the flow number range in the smallest cell was less than the critical value for suspension of coarse particles. Operating flow numbers for the three cell sizes under optimum conditions were close; commercial cells of the same size operating elsewhere appear to have two to three times higher flow numbers.The general relationships among air flow, impeller speed, particle suspension and flotation are discussed with particular reference to scale-up problems and coarse particle flotation. Both impeller speed and aeration should be considered as variables requiring systematic study and independent adjustment.     

Interactions between sulphide minerals and xanthates,I. The formation of monothiocarbonate at galena and pyrite surfaces

The rate of decomposition of potassium ethyl monothiocarbonate has been determined at pH values between 5 and 10, and its molar absorptivity at 221 nm determined to be 1.24 · 10⁴mol/cm.A novel apparatus for use in the study of reactions between sulphide minerals, oxygen and thiol reagents has been developed, and applied to the reactions of potassium ethyl xanthate with galena and pyrite. It has been shown that both minerals react with ethyl xanthate in the presence of oxygen or oxidation products to form soluble as well as adsorbed xanthate derivatives. The soluble derivative has been identified to be ethyl monothiocarbonate. The adsorbed xanthate at a galena surface, unlike that at a pyrite surface, is gradually converted to a soluble monothiocarbonate under the action of dissolved oxygen. The effect of variables such as pH, the initial xanthate and oxygen concentrations, and the initial state of oxidation of the mineral on the formation of monothiocarbonate has been studied. It is tentatively proposed that an intermediate adsorbed mixed xanthate-hydroxide species is involved in the formation of monothiocarbonate at both galena and pyrite surfaces.The significance of the formation of monothiocarbonate to flotation practice is discussed briefly. The formation of monothiocarbonate represents a wastage of reagent, and could lead to a decrease in flotability of xanthated galena with time of exposure to aerated solutions.     

Heavy metals in organic phases of river and estuarine sediment

Analysis of sediments taken from various levels in the lightly polluted River Blyth in Northumberland shows that quite high concentrations of metals can be accumulated in sediments.     

Water quality impacts from on-site waste disposal systems to coastal areas through groundwater discharge

This report summarizes research studies linking on-site waste disposal systems (OSDS) to pathogen and nutrient concentrations in groundwater with the potential to impact coastal embayments. Few studies connect OSDS to coastal water quality. Most studies examined pathogen and nutrient impacts to groundwater and omitted estimations of contaminants discharged to surface water. The majority of studies focused on nitrogen, with little information on pathogens and even less on phosphorus. Nitrogen discharged from OSDS poses the greatest threat to water quality. Vertical distance of septic tank infiltration system from the water table, septic system design, and siting remain the key components in minimizing potential impacts from OSDS for control of both pathogens and nutrients. The most comprehensive information connecting nutrient contributions from OSDS to surface water quality was the study conducted on Buttermilk Bay in Massachusetts where 74% of nitrogen to the bay was attributed to onsite disposal systems. In conclusion, further studies on the viability and transport of pathogens and nutrients through the groundwater aquifer and across the groundwater/surface-water interface are needed. Additional research on the importance of septic system design on the availability of contaminants to groundwater as well as the minimum distance between the septic system and water table necessary to protect groundwater are also indicated.