N. Turoczy

Mobility of the constituents of chromated copper arsenate in a shallow sandy soil

Abstract Small volumes of a commercial timber preservative containing approximately 60% w/w chromated copper arsenic (CCA) were applied to 15‐cm‐deep, undisturbed soil monolith lysimeters containing the surface horizon of a mildly acidic, sandy loam soil extracted from within the forestry plantation region of south‐west Victoria. The collected leachate and samples of the core profiles were analysed by inductively coupled plasma emission spectroscopy (ICP‐ES) for a total of 28 elements, including the active ingredients of the preservative, copper, chromium, and arsenic. After application of CCA, of the metals studied, only the concentrations of arsenic, calcium, chromium, sodium, and potassium in the leachate differed from background concentrations during the irrigation of the cores. Copper concentrations in all leachate remained at background levels throughout the experiment. Up to 36% of the applied dose of chromium was detected in the leachate, with breakthrough at 15 cm soil depth occurring within 20 days of preservative application. Up to 13% of the applied dose of arsenic was detected in the leachate collected at 15 cm depth, although in this case breakthrough was not observed until 25 days after preservative application. The applied copper was immobilised in the top 4 cm of the soil. Elevated concentrations of arsenic and chromium were found in the top 6 cm of the soil profile.

Competitive sorption of metals in water repellent soils: Implications for irrigation recycled water

Australia is a water-stressed nation and demand on potable water supply is increasing. Consequently water conservation and reuse are increasingly becoming important. Irrigation of recycled wastewater on water repellent soils is a technology that is being trialled as a means of improving crop production and conserving potable supply. However, recycled water contains potentially harmful heavy metals. This paper reports the competitive sorption and desorption of several common heavy metals found in soils collected from a farm located in the south-east of South Australia. The soil from this location is severely water repellent, but some sites were amended with kaolinite clay (Si4Al4O10(OH)8) about 7 and 15 years ago. The metals studied were Cu, Pb, Cd, Cr, Ni, and Zn. Competitive sorption of the metals was distinctly observed. For all heavy metals, the quantity of metal sorbed was higher in amended soil, and there was a strong correlation between the specific sorption to total sorption ratio and the amount of clay in the soil. The sorption intensities varied with metal, Cr, Pb, and Cu having a high sorption tendencies and Zn, Cd, and Ni having comparatively low sorption tendencies. The total sorption capacity for all metals increased in clay-treated soils compared with non-treated soils. On average, clay-amended water repellent soils had a 20–40% increased capacity to adsorb total metals; however, this increase was largely caused by the increased capacities to adsorb Zn, Cd, and Ni. The effect of clay treatment largely enhanced the sorption capacity of relatively weakly adsorbing heavy metals. The implications for using recycled wastewater on the long-term sustainable agro-environmental management of these soils are discussed.

PREFERENTIAL LEACHING OF NITRATE, CHLORIDE AND PHOSPHATE IN AN AUSTRALIAN CLAY SOIL

This paper investigates leaching of water and nutrients (NO/, Cl, PO/) from the unsaturated layer in an Australian soil using a multisegment percolation system (MPS). Large undisturbed soil cores were collected from a clay-based, basaltic plain, agricultural soil at Grassmere, 300 km west of Melbourne, Australia. Significant heterogeneity (or preferential flow) of effluent moisture and solutes was detected (one-way ANOVA, p < 0.001). Fifty percent of the applied nitrate and chloride leached from the soil core within three days after initial application. Hundred percent of the applied nitrate and chloride leached from the soil core within 8 days after application. These results indicate little incorporation into the soil matrix, and possible denitrification or mineralisation. In contrast, after 18 days, less than 1% of the total applied phosphates leached from the soil, indicating strong adsorption. Our experiments indicate considerable heterogeneity in water flow patterns and solute leaching on a small spatial scale. Very rapid transport of nitrate and chloride through the soil was evident, in comparison phosphate leaching was negligible. These results have important implications for the management of nutrient schedules in agricultural soils, particularly those located in the Western District of Victoria, Australia.

Leaching of copper, chromium and arsenic in a soil of south west Victoria, Australia

The movement of copper, chromium and arsenic originating from samples of the wood preservative Tanalith® through mildly acidic, sandy loam soil was investigated. Small, undisturbed soil cores (of dimensions 15 × 15 × 15 cm) were removed from the topsoil of a paddock adjacent to the Glenelg River in the Western District of Victoria, Australia. The paddock soils were thin (<30cm) greyish brown, mildly acidic, sandy loams with a moderate organic carbon content (2–5%) overlying a limestone cap. Tanalith® was applied to the surface of the cores which were then irrigated with deionised water at approximately 30 mm day‐1. Copper concentrations in all leachate remained at background levels throughout the experiment, and this element was found to be immobilised in the top 4 cm of the soil. Up to 29% of the applied dose of chromium was detected in the leachate, with breakthrough occurring within 20 days of Tanalith® application. Up to 13% ofthe applied dose ofarsenic was detected in the leachate, although in this c...

Observations on metal concentrations in commercial landings of two species of tilapia (Oreochromis mossambicus and Oreochromis niloticus) from reservoirs in six river basins in Sri Lanka

Samples of the muscle of two species of tilapia (Oreochromis mossambicus and O. niloticus; 17–20 cm length) were obtained from at least one reservoir in each of the six river basins (Aruvi Aru, Kala Oya, Kirindi Oya, Ma Oya, Mahaweli, and Walawe Ganga catchments) in Sri Lanka. The metals Ca, Cu, Fe, K, Mg, Mn, Na, and Zn were consistently detected in the muscle tissue. Overall, there were few differences in the concentration of metals between the two species of fish, although there were also some statistically significant differences (p < 0.05) in the concentrations of some metals in fish obtained from some of the reservoirs. Aruvi Aru stands out as a river basin in which the two fish species have significantly lower concentration of metals when compared to other river basins. The concentration of the metals studied were below WHO and FSANZ guideline values for fish, suggesting that the consumption of the metals found in tilapia from these reservoirs poses little risk to human health.

The influence of weather and solar elevation on perceived colour of Blue Lake, Mount Gambier, South Australia

Summary Previous studies of the remarkable seasonal colour changes of Blue Lake, Mount Gambier, South Australia have speculated on the roles of weather and solar elevation in this phenomenon. In this study the influence of weather and solar elevation on apparent colour is examined. Solar elevation and some weather variables were found to have a statistically significant influence, particularly when Blue Lake is undergoing transition from its blue to grey stage. However, the proportion of the overall variation in colour explained by solar elevation and weather was only 16%, so it is concluded that in-lake properties are probably the main determinants of colour.