Graham Lancaster

A microwave digestion method for the extraction of phytoliths from herbarium specimens

Abstract The extraction of phytoliths from herbarium and/or fresh plant material to obtain a suite of comparative reference samples is an essential component of palaeobotanical studies for the accurate interpretation of fossil phytolith assemblages. A number of established methods have been employed to extract phytoliths from plant material including dry ashing and acid digestion. However, while these methods produce good results, they can be time consuming and have the potential to produce results with some cross-contamination if not monitored closely. In this study, we trial an alternative method using microwave digestion, and compare the results to those produced using a conventional dry ashing method. The results of this study indicate that the microwave digestion technique is quick, eliminates concerns of cross-contamination and produces comparable phytolith assemblages to those of the conventional dry ashing method.

Acid neutralising capacity of two different bauxite residues (red mud) and their potential applications for treating acid sulfate water and soils

The acid neutralising capacity (ANC) and potential beneficial uses of 2 different bauxite residues (red mud) were investigated. The results show that the ANC is much higher in the red mud disposed of using a dry stacking method at the Pingguo Alumina Refinery (China) than in the red mud disposed of by a wet method using seawater at the Queensland Alumina Ltd Refinery (Australia). The higher ANC in the Pingguo red mud is attributable to its high CaO and low SiO2. An incubation experiment showed that leaching of alkaline materials from the lime-treated sample was much greater than that from the red mud-treated sample. This suggests that red mud may be superior to lime for treating potential acid sulfate soils, which contain sulfide minerals that could take a long time to oxidise and release soluble acid. The effects of 2 acid-filtering systems were tested, both of which used red mud as the main material for removal of acid from passing acidic water. The results showed that the red mud–CaCO3 filter performed better than the red mud–Mg(OH)2 filter. Results from pot trials in Australia further demonstrated that the application of combined red mud and sewage sludge significantly improved the soil conditions for the growth of 5 Australian native tree species, in addition to Eucalyptus paniculata, which successfully grew in the same mine soil amended with the red mud and sewage sludge in previous work of G. Maddocks et al. The results from the pot experiment in China showed that the application of combined neutralising agents (red mud/lime blends) and sewage sludge to the extremely acidic mine soil was insufficient for creating appropriate ecological conditions for the growth of vetiver grass. In this experiment, additional application of zeolitic rock powder significantly improved the growth performance of the plant.

An improved analytical procedure for determination of total actual acidity (TAA) in acid sulfate soils

An improved analytical procedure is proposed for the determination of total actual acidity (TAA) in acid sulfate soils. The proposed method involves the use of a superior extracting solution, 0.5 M BaCl2, instead of the 1 M NaCl used by Konsten et al. (Konsten CJM, Brinkman R, Andriesse W. A field laboratory method to determine total potential and actual acidity in acid sulfate soils. In: Dost H, editor. Selected papers of the Dakar Symposium on Acid Sulfate Soils. Wageningen: ILRI Publication 44, 1988:106-134.) and improved experimental design to obtain correction factors for calculating TAA. The introduction of a multi-choice procedure also enables increased accuracy of analytical results to be obtained if more accurate TAA estimation is required.

Effects of Bauxsol on the immobilisation of soluble acid and environmentally significant metals in acid sulfate soils

The effects of Bauxsol, an abundant industrial by-product, on the immobilisation of soluble acid and a range of potentially environmentally toxic metals in artificial and natural acid sulfate soils were investigated. The acid neutralising capacity of Bauxsol increased with decreasing pH, which is probably provided not only by basic metal hydroxides, carbonates, and hydroxycarbonates but also by protonation of variably charged particles (e.g. gibbsite and hematite) present in Bauxsol. Simulation experiment results show that the removal of 9 tested environmentally significant heavy metals can be enhanced by addition of BauxsolTM; an exception was Co. The removal of the added soluble heavy metals by the BauxsolTM-soil mixtures shows a preferential order of Pb > Fe > Cr > Cu > Zn > Ni > Cd > Co > Mn. For the natural acid sulfate soil without added synthesised metal solution, the retention of the investigated environmentally significant metals is in the following decreasing order : Al > Zn > Fe > Co > Mn.

Total sulphide acidity for the definition and quantitative assessment of the acid sulphate hazard: Simple solution or a new suite of problems

Abstract Recent investigations show that the TSA (Total Sulphide Acidity) method for the definition and quantitative assessment of acid sulphate soils is unreliable. Although potential acid sulphate soils do produce high TSA values, high TSAs may also be recorded from non-acid sulphate soils; this problem may arise when organic matter oxidises during the hydrogen peroxide treatment to form short-chained organic acids, or when reduced iron in the soil undergoes ferrolysis. Because significant overestimations of acid production from non-acid sulphate soils are common, we recommend that the TSA procedure be abandoned as a method for assessing acid sulphate soils. We propose that assessment of both actual and potential acid sulphate soils must be based on a sulphur species specific method [1].