Aqua regia digestible and labile metal concentrations of PRB media

Brief description

The data set consists of two types of assessments of permeable reactive barrier (PRB) media: aqua regia digestions and 1 M HCl acid extractions. All analytical analysis was completed using inductively couple plasma-optical emission spectroscopy (ICP-OES).

Aqua regia digestions were conducted on to assess the purity of three iron sources (Peerless, Connelly and Chem-Supply). 15 mL of aqua regia (3:1 concentrated hydrochloric acid: nitric acid) was added to 0.5 g iron samples in triplicated Teflon containers. The solution was heated at 80 degrees C for three hours and left at 40 degrees C for a further three days. The mixture was diluted to 100 mL and filtered at 0.45 microns before analysis.

The Lower PRB at the Casey Main Power House was originally constructed in the 2005/06 summer for details refer to (Mumford et al., 2013). The reactive gate consists of five modified Australian Antarctic Division cage pallets with external dimensions 1.8 x L 1.1 W x 0.75 H m. During the 2012/13 field season, media in the fifth cage was replaced with a new trial media sequence (Statham draft publication). Refilling occurred on the 16th of January. In this process mixed media sequences were homogenised by a cement mixer in 40 L batches and then placed in the PRB cage.

Material samples were cored from within the new media sequence of the PRB, three in GAC/ZeoPro, three in ZVI/sand and two in the zeolite section (Statham unpublished manuscript). All samples were collected from a depth of 45-60 cm then stored at -18 degrees C for transport to Australia. The concentration of bioavailable metals within the field and raw material samples were using a method recommended by Snape et al. (2004). All extractions used 2 g of oven dried medium and 40 mL of HCl solution and were conducted in new duplicated polypropylene containers. The mixtures were revolved on a suspension mixer for four hours, promptly filtered at 0.45 microns before analysis

Element concentrations were determined by ICP-OES using a Varian 720-ES spectrometer at the Australian Antarctic Division. The emission intensity of standards and sample solutions was measured following 1:1 in-line mixing with a solution of 0.75% (w/v) CsCl matrix modifier in 10% (v/v) HNO3 containing 5 mg L-1 yttrium as an internal standard. Aqua regia iron concentrations were determined from a 1 in 50 dilution of the filtered solution. The matrix modifier was deemed unnecessary for the HCl extractions. A blank samples for both methods indicated that the presence of the analysed elements was due to dissolution from PRB media and not other sources.

The limit of quantification (LOQ) was determined by the NATA extrapolation method (NATA, 2009) using concentrations of 20, 50 and 100 microns L-1 for phosphorus and potassium and 4, 10 and 20 microns L-1 for all other measured elements.

The data consists of four excel files of ICP analysis results:
1. The limit of quantification and certified reference material results from aqua regia digestion
2. The limit of quantification and certified reference material results from 1 M HCl extractions
3. Aqua regia digestion results and calculations
4. 1 M HCl extractions results and calculations