T erera Generaión

Sample contamination was monitored by analysing blanks created in the field, with the quality of analyses monitored using charge balances, as described in Chapter

Chapter Three – Aquifers and groundwater bodies in the Wybong Creek catchment 59

Ether’s #1

Queen St

Roach’s #1 Roach’s #2 Woodlands Grove Bore

Ether’s #2 Wicks Darts Pivot Woodlands Windmill Coffin Gully Rossgole #2 0 55 km N 40 km Rockhall GW080948Rockhall 080947 Rockhall 080945 Rockhall 080946 TSR Wybong seep Hannah’s Dry Creek Road seep

Wybong Bridge Morgan’s Yarraman Bore Yarraman Well Site Four Site Three Site Two Site One Robert’s #1 Site Six Site Five Site Eight PAHOH-08 CALM-02 BFC-TSR CGN-155 CGN-092 CGN-148 PAHOH-39 PAHOH-25 Spring’s Spring Dip Spring

Yarraman Gauge Seep

Frenchies

Whip Well

Robert’s House

Ray’s spring Googe’s Well

Figure 3.1. Groundwater sampling locations within the Wybong Creek catchment, including springs ( ), bores ( ), and piezometers ( ), where bores are screened into a number of water-yielding layers and piezometers are screened into a single layer.

Chapter Three – Aquifers and groundwater bodies in the Wybong Creek catchment

60

Two (Section 2.2.2). Sample contamination occurred on 27/01/2009 with most contamination coming from Cl and some from Ca, Mg, Na and K (Tables A3.1 – A3.2). This contamination was ignored given the large concentration of these ions in water samples and the small error thus resulting from contamination.

The quality of analyses was monitored using charge balances (Chapter Two). Six of the 78 groundwater samples analysed for ions had charge balances exceeding 15 % (Table A3.3). Ray’s Spring had a charge balance of 38.6 %, with the low ion

concentration in this sample possibly causing erroneous quantification of ions.

Yarraman Bore was uncapped and was not able to be purged due to depths over 200 m, with the charge balance of -17.6 % seen for this sample possibly indicating

contamination. Data presented from Yarraman Bore and Ray’s Spring should be

considered with these charge balances in mind. Queen St (22/07/2006), Wybong Bridge (25/04/2006), Dip Paddock Spring (22/07/2008), and Ether’s #2 also had charge

balances exceeding 15 %, and with all major anions and cations analysed, this was likely due to an error in the measurement of HCO3 by titration in the field. Only a small

decrease in the total HCO3 concentration was needed to correct charge balance

differences in these samples. Data was therefore uncorrected due to the small affect it had on the interpretation of results.

2.2.1. Cation and anion analyses

Reactive ions were analysed in the field using a Hach spectrophotometer and method 8146, 1, 10-Phenanthroline for Fe2+_{; method 10209 phosphomolybdate for}

PO42-; cadmium reduction for NO32-; and BaCl for SO42-(Hach Company 2009).

Samples collected for ion analyses during 2006 and 2009 were sent to the Centre for Coastal Biogeochemistry, Southern Cross University. Samples for ion analyses collected in 2007 – 2008 were sent to the Department of Water and Energy Water Environmental Laboratory, New South Wales, for analyses.

2.2.2. Strontium isotope analysis

Select samples were analysed for 87Sr/86Sr by Marc Norman at the Research School of Earth Sciences, The Australian National University. Samples were prepared for analysis by drying 10 mL of sample on a hotplate, with 1 mL of 2 M HNO3 taken up

for loading on Eichrom Sr-specific resin. Strontium was collected by elution with 0.05 M HNO3 after eluting matrix elements using additional 2 M HNO3 and 7 M HNO3. The

Chapter Three – Aquifers and groundwater bodies in the Wybong Creek catchment 61

steps were conducted in a clean laboratory using distilled reagents. Strontium isotopic compositions were measured on a Finnigan MAT 261 thermal ionisation multi-collector mass spectrometer. The samples were loaded individually onto single filaments that had been outgassed under a vacuum with a four amp current. Each analysis consisted of ten blocks of 12 cycles each. The masses of 84_Sr, 85_Rb, 86_Sr, 87_{Sr, and} 88_{Sr were}

measured simultaneously and corrected for mass fractionation to 86Sr/88Sr = 0.1194 (Bohlke et al. 2005). Corrections for 87Rb interferences were applied if necessary assuming 85Rb/87Rb = 0.3857 (Bohlke et al. 2005). The weighted mean 87Sr/86Sr of the NBS987 isotopic standard run on this mass spectrometer during the period 2005-2009 was 0.710221±0.000005 (2 SE, n=44; M. Norman, Pers. Comm., 2009).

2.2.3. Carbon isotope analysis

Samples were analysed for 14_{C and} 13_{C at the Research School of Earth Sciences,}

The Australian National University. Samples were made basic using ~ 1 mL NaOH(aq),

with analytical grade SrCl2(s) then added to excess prior to analysis. The SrCO3 that

precipitated out of this solution was filtered through 0.45 µm Millipore® nitrocellulose filters and collected in 5 mL vials. Concentrations of 14_{C and} 13_{C were then assessed}

using a National Electrostatic Corp. (NEC) Single Stage Accelerator Mass Spectrometer (SSAMS).

2.2.4. Sulfur isotope analysis

Select samples were analysed for δ34S at the Centre of Coastal Biogeochemistry, Southern Cross University. Tin cups containing the samples were brought to an

elemental analyser (Flash EA, Thermo Fisher) coupled to a mass spectrometer for stable isotope analyses (Delta V plus, Thermo Fisher) by means of a continuous flow interface (Conflo, Thermo Fisher). Samples were combusted at1020 °C, and the combustion gases passed through a matrix of tungsten alumina. Here samples were oxidized before passing through Cu wires where they were reduced. Water vapour was removed with magnesium perchlorate. The remaining gases were passed to a chromatography column to separate SO2, before SO2 was injected into the mass spectrometer. The ratio of

66_SO

2/64SO2 was then measured against sulfanilamide standard every ten samples. The

value of δ34SSulfanilamide had a standard deviation of 20.5 ± 0.25 (M. Carvalho de

Chapter Three – Aquifers and groundwater bodies in the Wybong Creek catchment

62