Vertical distributions of 210Pb excess, 7Be and 137Cs in selected grass covered soils in Southeast Queensland, Australia

Net accumulated areal activity densities and profiles of (210)Pb(ex), (7)Be and (137)Cs in the surface 10 cm of the soil are reported for eight sites in Southeast Queensland, Australia. Areal activity densities of (210)Pb(ex) and (7)Be varied from 1,080 to 4,100 Bqm(-2) and from 176 to 778 Bqm(-2), respectively. A significant (p < 0.001) portion of the variance (R(2) > 0.99) in their vertical distributions was explained by depth in the profile using an exponential function. Around 85% of accumulated (210)Pb(ex) was present in the surface 10 cm of the soil. Beryllium-7 was mainly confined to the grass and surface 2 cm of the soil. Average penetration half-depths of 3.6 +/- 0.2 and 0.3 +/- 0.1cm were determined for (210)Pb(ex) and (7)Be, respectively. Areal activity densities of global fallout (137)Cs varied from 10 to 361 Bqm(-2). Its signal was well mixed within the surface 10 cm. Comparison of the measured (137)Cs values to the estimated input value for the region ( approximately 490 Bqm(-2)) and profiling of a 1m deep soil core suggests a vertical migration of (137)Cs over the past decades. The paleo-radon activity flux determined from the (210)Pb(ex) areal activity density (5.1 +/- 0.9 mBqm(-2) s(-1)) was not statistically different to that measured using activated charcoal cups (5.5 +/- 0.4 mBqm(-2) s(-1)), tending to suggest that Southeast Queensland is neither a net source nor a net sink of (210)Pb-bearing aerosols.     

Bioremediation of toxic metals mercury and cesium using three types of biosorbent: bacterial exopolymer,gall nut,and oak fruit particles

Cesium and mercury are two mono-valent elements which can be found in toxic industrial, medical, and nuclear wastes. Their presence in the environment has deleterious effects on the ecosystem, living organisms including humans. Due to the chemical nature of these metals, bioremediation by conventional methods is more difficult to achieve compared to other metals. In this study, we used three biosorbents (oak powder, gall nut, and bacterial exopolymer) for the bioremediation of Hg and Cs. Bio-polymer was produced in the GMS mineral broth. Synthetic wastes of Hg(NO₃)₂ and isotope Cs-133 as the single-metal solutions were used. The biorefining process was carried out in glass columns, made of Pyrex, with dimensions 20?×?7/2?cm² with a V-shaped bottom. The samples were analyzed using atomic absorption. The experimental results showed that eliminated metal percent by oak powder, gall nut, and bacterial exopolymer were, respectively, of 94.8%, 96%, and 13.8% for Hg and 7.8%, 4.4%, and 69.4% for Cs. The tests revealed that Ca⁺⁺, when used as flocculant, played a key role in both biosorption and bio-precipitation rates. Consequently, it was concluded that the investigated biosorbents could be use as an integrated biosorption system for the refinement of mixed wastes.     

Do transportation taxes promote pro-environmental behaviour? An empirical investigation

The transportation sector is a crucial driver of energy intensity and environmental degradation. Therefore, we aim to explore the nexus of transportation taxes, energy intensity, and CO₂ emissions for the BICS economies. The econometric approaches, CS-ARDL and PMG-ARDL, have been employed to compute the estimates. The long-run estimates of the green transportation tax variable are negatively significant in both energy intensity and CO₂ emissions models irrespective of the estimation technique. These findings imply that green transportation taxes help reduce energy intensity and CO₂ emissions in BICS economies. Conversely, in the short-run, the effects of transportation taxes on energy intensity and CO₂ emissions are mixed and inconclusive. Hence, transportation taxes are necessary to keep the polluters under control not only from the transport sector but also serve as a deterrent for other sectors as well.

     

Mapping radioactivity in groundwater to identify elevated exposure in remote and rural communities

A survey of radioactivity in groundwater (110 sites) was conducted as a precursor to providing a baseline of radiation exposure in rural and remote communities in Queensland, Australia, that may be impacted upon by exposure pathways associated with the supply, treatment, use and wastewater treatment of the resource. Radionuclides in groundwater, including ²³⁸U, ²²⁶Ra, ²²²Rn, ²²⁸Ra, ²²⁴Ra and ⁴⁰K were measured and found to contain activity concentration levels of up to 0.71 BqL⁻¹, 0.96 BqL⁻¹, 108 BqL⁻¹, 2.8 BqL⁻¹, 0.11 BqL⁻¹ and 0.19 BqL⁻¹ respectively. Activity concentration results were classified by aquifer lithology, showing correlation between increased radium isotope concentration and basic volcanic host rock. The groundwater survey and mapping results were further assessed using an investigation assessment tool to identify seven remote or rural communities that may require additional radiation dose assessment beyond that attributed to ingestion of potable water.     

Equilibrium sampling used to monitor malodors in a Swine waste lagoon

The concentrations of malodorous compounds in a 0.4-ha anaerobic lagoon that received waste from approximately 2000 sows were monitored during the late summer to late fall of 2006 to gain insight into the factors influencing their concentrations. Selected malodorous compounds were measured by the use of equilibrium samplers consisting of submersible stir plates and stir bar sorbtive sampling with polydimethylsiloxane-coated magnetic stir bars. During the same period, air and water temperatures, suspended solids, total organic carbon and nitrogen content, and wastewater pH were recorded. Concentrations of malodorous compounds were higher at the surface of the lagoon than at the middle or bottom of the lagoon. Skatole concentration, for instance, averaged 54, 24, and 38 microg L(-1) near the surface, in the middle, and at the lowest sampling depths, respectively. While the lagoon was being pumped down during field application of wastewater, concentrations of malodorous compounds fluctuated widely, increased 16-fold as compared with the sampling period before pumping, and continued to increase as fall progressed and temperatures cooled. Suspended solids, volatile suspended solids, and total organic carbon increased near the bottom of the lagoon during this same period. The increases in the concentrations of malodorous compounds in the wastewater during the fall could have been due to a combination of several factors. These factors include reduced degradation by lagoon bacteria, less wind stripping of volatile compounds from the lagoon surface due to lowering of the lagoon surface after crop application, and/or reduced evaporation of malodorous compounds due to falling temperatures.     

Radon-222 exhalation from open ground on and around a uranium mine in the wet-dry tropics

Radon-222 exhalation from the ground surface depends upon a number of variables such as the 226Ra activity concentration and its distribution in soil grains; soil grain size; soil porosity, temperature and moisture; atmospheric pressure, rainfall and temperature. In this study, 222Rn exhalation flux density measurements within and around the Ranger uranium mine in northern Australia were performed to investigate the effect of these variables within a tropical region. Measurements were taken at the waste rock dumps, ore stockpiles, mine pits, and at sites where effluent water with elevated 226Ra concentration has been spray irrigated over land, as well as at sites outside the mine. The sites selected represented a variety of geomorphic regions ranging from uranium-bearing rocks to ambient soils. Generally, wet season rains reduced 222Rn exhalation but at a few sites the onset of rains caused a step rise in exhalation flux densities. The results show that parameters such as 226Ra activity concentration, soil grain size and soil porosity have a marked effect on 222Rn flux densities. For similar geomorphic sites, 226Ra activity concentration is a dominant factor, but soil grain size and porosity also influence 222Rn exhalation. Surfaces with vegetation showed higher exhalation flux densities than their barren counterparts, perhaps because the associated root structure increases soil porosity and moisture retention. Repeated measurements over one year at eight sites enabled an analysis of precipitation and soil moisture effects on 222Rn exhalation. Soil moisture depth profiles varied both between seasons and at different times during the wet season, indicating that factors such as duration, intensity and time between precipitation events can influence 222Rn flux densities considerably.