Andrew J. Feitz

Household dust metal levels in the Sydney metropolitan area.

Household dust was collected from 82 residential homes within the Sydney metropolitan area. The geometric mean concentrations of metals in the household dust were Cd, 1.9 microg/g; Cr, 64.3 microg/g; Cu, 103 microg/g; Fe, 2740 microg/g; Mn, 54 microg/g; Ni, 15.6 microg/g; Pb, 85.2 microg/g; and Zn, 437 microg/g. Differences in household income level, dwelling type, or the number of occupants were not statistically significant for the majority of metals. The exceptions were higher amounts of Zn (P=0.033) and Fe (P=0.047) found in households with only 1-2 residents compared to those with 3-4 or >4 residents, and slightly higher Mn levels (P=0.033) were found in low-income households (AUD 0-30,000 dollars/year). Region was highly significant for Pb levels in Sydney but not significant for other metals. Large variations in Pb levels were found in household dust (16-16,600 microg/g), with the inner-west region associated with significantly higher Pb levels (P<0.001). Comparisons with a study from a decade earlier have revealed that the household dust Pb levels have remained constant despite substantial improvements in air quality in the inner-west area of Sydney. New epidemiological studies are required to determine whether Pb blood levels have also remained unchanged and whether accumulated Pb in household dust represents a significant health risk to children in this region.

Solar radiation disinfection of drinking water at temperate latitudes: inactivation rates for an optimised reactor configuration.

Solar radiation-driven inactivation of bacteria, virus and protozoan pathogen models was quantified in simulated drinking water at a temperate latitude (34 degrees S). The water was seeded with Enterococcus faecalis, Clostridium sporogenes spores, and P22 bacteriophage, each at ca 1x10(5) mL(-1), and exposed to natural sunlight in 30-L reaction vessels. Water temperature ranged from 17 to 39 degrees C during the experiments lasting up to 6h. Dark controls showed little inactivation and so it was concluded that the inactivation observed was primarily driven by non-thermal processes. The optimised reactor design achieved S90 values (cumulative exposure required for 90% reduction) for the test microorganisms in the range 0.63-1.82 MJ m(-2) of Global Solar Exposure (GSX) without the need for TiO2 as a catalyst. High turbidity (840-920 NTU) only reduced the S(90) value by <40%. Further, when all S90 means were compared this decrease was not statistically significant (prob.>0.05). However, inactivation was significantly reduced for E. faecalis and P22 when the transmittance of UV wavelengths was attenuated by water with high colour (140 PtCo units) or a suboptimally transparent reactor lid (prob.<0.05). S90 values were consistent with those measured by other researchers (ca 1-10 MJ m(-2)) for a range of waters and microorganisms. Although temperatures required for SODIS type pasteurization were not produced, non-thermal inactivation alone appeared to offer a viable means for reliably disinfecting low colour source waters by greater than 4 orders of magnitude on sunny days at 34 degrees S latitude.

Atmospheric tomography: a bayesian inversion technique for determining the rate and location of fugitive emissions

A Bayesian inversion technique to determine the location and strength of trace gas emissions from a point source in open air is presented. It was tested using atmospheric measurements of N(2)O and CO(2) released at known rates from a source located within an array of eight evenly spaced sampling points on a 20-m radius circle. The analysis requires knowledge of concentration enhancement downwind of the source and the normalized, three-dimensional distribution (shape) of concentration in the dispersion plume. The influence of varying background concentrations of ∼1% for N(2)O and ∼10% for CO(2) was removed by subtracting upwind concentrations from those downwind of the source to yield only concentration enhancements. Continuous measurements of turbulent wind and temperature statistics were used to model the dispersion plume. The analysis localized the source to within 0.8 m of the true position and the emission rates were determined to better than 3% accuracy. This technique will be useful in assurance monitoring for geological storage of CO(2) and for applications requiring knowledge of the location and rate of fugitive emissions.

Soil salinisation: a local life cycle assessment impact category

Salinity is an increasing environmental problem in agricultural ecosystems and is not adequately represented in conventional life cycle assessment (LCA) impact categories. It is often not the total quantity of salts emitted or the proportion of salt accumulated in the soil profile that is the primary mechanism for deteriorating soil conditions for irrigated salinity, rather the ratio of major cations in the soil matrix and the potential for colloid dispersion and reduced permeability. A soil salinisation potential (SP) is proposed as an indicator for irrigated salinity and potential soil degradation from poor irrigation practices. The indicator uses the threshold electrolyte concentration concept that predicts the adjusted sodium adsorption ratio (SAR)/ Electrical conductivity (EC) ratio that soil will no longer flocculate, but potentially disperse. The SAR is converted to a threshold EC and compared to the measured EC in order to develop a site-specific irrigation equivalence factor (EF). This site/region/process specific EF is then used to weight the sodium load to soil and repeated for each stage throughout the entire life cycle to determine the overall Salinisation Potential (SP). The data required for calculating the SP is generally readily available either on site or from the water chemistry of the local watercourses. Preliminary calculations simply require the volume, pH, electrical conductivity (EC), alkalinity and the concentrations of Na, Ca, and Mg of the irrigation water. The site/process/region specific nature of the indicator ensures a quantitative measure to enable comparisons between different systems and is useful for identifying stages in the life cycle of a product (particularly food products), where the potential for soil salinisation and soil degradation is most severe.

Photo-Fenton degradation of dichloromethane for gas phase treatment

A continuous photo-Fenton process has been used for the degradation of gaseous dichloromethane (DCM). By absorbing gaseous DCM into a reactive Fenton mixture, the scrubbing and degradation processes could be completed in the one reactor. Operating with a Dark Fenton solution did not result in removal of DCM any better than simply using MilliQ water. This was because the Fe(II) quickly converted to Fe(III) but was unable to regenerate. After a short time, the Fenton process was no longer operating and the DCM quickly accumulated in the reaction solution, preventing further accumulation due to a decreasing concentration gradient in the reactive solution. However, by using UV light and increasing the retention time from 20 to 50 s, there was sufficient time for the reactive solution to regenerate and continuous operation could achieve at least 65% removal of DCM from the gaseous phase at ambient temperature.

COMPARISON OF THE REACTIVITY OF NANOSIZED ZERO-VALENT IRON (nZVI) PARTICLES PRODUCED BY BOROHYDRIDE AND DITHIONITE REDUCTION OF IRON SALTS

Dithionite can be used to reduce Fe(II) and produce nanoscale zero-valent iron (nZVI) under conditions of high pH and in the absence of oxygen. The nZVI is coprecipitated with a sulfite hydrate in a thin platelet. The nanoparticles formed are not pure iron but this feature does not appear to affect their degradation performance under air or N2 gas conditions. The efficiency of trichloroethylene (TCE) degradation, when one is employing nanoparticles manufactured using dithionite (nZVIS2O4), is similar to if not slightly better than that of the more conventional borohydride procedure (nZVIBH4). The other advantages of the dithionite method are that (i) it uses a less expensive and widely available reducing agent, and (ii) there is no production of potentially explosive hydrogen gas. Oxidation of benzoic acid using the nZVIS2O4 particles results in different byproducts than those produced when nZVIBH4 particles are used. The low oxidant yield based on hydroxybenzoic acid generation is offset by the production of higher concentrations of phenol. The high concentration of phenol compared to hydroxybenzoic acids suggests that OH• addition is not the primary oxidation pathway when one is using the nZVIS2O4 particles. It is proposed that sulfate radicals () are produced as a result of hydroxyl radical attack on the sulfite matrix surrounding the nZVIS2O4 particles, with these radicals oxidizing benzoic acid via electron transfer reactions rather than addition reactions.

Absence of detectable levels of the cyanobacterial toxin (microcystin-LR) carry-over into milk.

The potential for the carry-over of the cyanobacterial toxin, microcystin-LR, from feed to milk was assessed using four Holstein-Friesian cows in a 4 week feeding trial. Two cows were used as control and the other two dosed daily at increasing weekly concentrations of microcystins from zero to a maximum dosage of 13 microg toxin kg x (-1) d x (-1) (or 7.4 mg toxin day(-1)). The absence of any deviation from the control in terms of physiological response and plasma indicators (total bilirubin, gamma-glutamyl transpeptidase and alkaline phosphatase) suggests that the microcystin-LR dosage did not have a detrimental effect on cattle liver function or milk yield during the course of the study. While the milk production did decrease over the period of the trial, no difference was observed between control and dosed cattle. Protein phosphatase inhibition assays were successfully used to determine the presence of microcystin-LR in prepared milk samples with an average recovery of 88% for samples spiked with 0.6 microg x l(-1) microcystin-LR. The level of microcystin-LR in all milk samples during the trial was less than 0.2 microg x l(-1). This suggests that after digestion, microcystin--LR is either not present in milk or sufficiently modified to render it non-toxic.

Broadening the Scope of Modified Photo-Fenton Processes in Water and Wastewater Treatment through Ferric Complex Design

The modified photo-Fenton process is an interesting variant of the standard Fenton reagent that enables degradation of selected contaminants at higher rates and higher pHs than achievable by the thermal process. The effectiveness of the process is variable, however, and its application should be used with care. In some instances, it appears that addition of oxalate actually inhibits contaminant degradation as a result of the formation of non-photoactive ternary oxalato complexes. Scope appears to exist for investigation of alternative Fe(III) chromophores that may retain their photoactivity at even higher pH (and possibly with more effectiveness) than is achieved by ferrioxalate.

Solar Pilot-scale Photocatalytic Degradation of Microcystin-LR

Abstract A solar immobilized-catalyst photocatalytic reactor design and TiO2 attachment procedure is presented. The reactor is used to remove cyanobacterial toxins from drinking water samples spiked with trace levels of microcystin-LR (MLR). The reactor is randomly packed with TiO2 coated ceramic Raschig rings, which provide a large surface area without compromising aperture area. The true quantum efficiency of the reactor ranges from 2.4 - 2.8% for dichloroacetic acid mineralization. At pH 7, no removal of M L R is observed under simulated dark conditions suggesting that adsorption and air stripping have negligible effect in the removal of microcystin-LR from drinking water. Rapid removal of MLR is observed once exposed to sunlight and little difference is detected between the removal rates under cloudy or sunny conditions. The virtual independence of degradation rates for low to moderate levels of cloud cover is due to the ability of the nonconcentrating reactor to harness diffuse light (unlike concentrating reactors which require direct irradiation) and minimize reflection losses.

Update on greenhouse gas emissions quantification research activities in the Australian resources sector

This paper provides an overview of recent research undertaken in Australia to improve quantification of methane and carbon dioxide emissions in the resources sector at local and regional scales.