Surface water and sediment samples were collected following applicable criteria denoted in the Australian and New Zealand Environment and Conservation Council (ANZECC) Water Quality Guidelines (2000). Samples were collected from surface water either directly in method-specified containers or from a decontaminated syringe and then transferred directly into method-specified containers. Sample bottles were either provided by RJ Hill Laboratories Limited, an International Accreditation New Zealand (IANZ) certified lab, or were HDPE containers from the University of Canterbury Environmental Engineering Laboratory. Sample bottles, syringes and associated tubing, digital pipette tips and components of filtering apparatuses (with exception of disposable filters) sourced at the University of Canterbury were decontaminated with an initial washing in an Alconox® solution followed by a tap water rinse, deionised water rinse, a 24-72 hour immersion in a five-percent nitric acid (HNO3) solution followed by a tap water rinse and a final deionised water rinse. All samples were collected head-space free, with exception of those for TSS, and were chilled at 2-6oC immediately upon collection until the time of analysis following appropriate criteria specified in APHA (1998) and/or APHA (2005). Water quality parameters measured using portable probes (e.g. temperature, pH, conductivity, DO and Eh) were measured directly in-situ with data recordedwhen readings stabilised. Turbidity samples were collected directly into instrument specific cuvettes and
analysed immediately upon collection. Samples collected for Fe2+ analysis were collected initially with a digital pipette and diluted with deionised water to the appropriate volume in instrument specific glass cylinders. Sediment samples from the Manchester Pond were collected into method specified HDPE containers provided by RJ Hill Laboratories Limited using decontaminated gloves.
2.2.2 Calibration and Operation of Portable Water Quality Instruments
Water quality parameters including temperature, pH, conductivity, DO, Eh, turbidity and Fe2+ were measured using pre-calibrated portable water quality instruments. Instruments were calibrated just prior to sample collection using fresh standards and validated to ensure they maintained calibration following measurements. Sample pH was measured using a YSI Model 60 pH meter field calibrated with pH 4.01 and 7.00 standards (and pH 10.00 standard when applicable) and checked with a pH 1.68 standard. Conductivity was measured with a Hach sension 156 multiparameter meter field calibrated to a 0.01 M (1413 µS/cm at 25oC) potassium chloride (KCl) solution and checked with a 0.1 M (12,890 µS/cm at 25oC) KCl solution. Specific conductance and TDS were calculated from conductivity and temperature measurements using Equations 2.1 and 2.2 (from Tchobanoglous and Schroeder (1985)), respectively.
Specific Conductance (25oC) = Conductivity / (1+TC * (T-25)) (2.1) where:
TC represents a constant ≈ 0.0191; and T represents temperature in oC.
TDS (mg/L) ≈ Specific Conductance (µS/cm) * (a constant between 0.55 and 0.70) (2.2) The constant commonly used for Equation 2.2 is 0.6563, which is representative of a pure KCl solution (APHA, 1998). Salinity was also estimated from conductivity (Standard Methods 2520B, 1998). The value is comparable to that of TDS but standardised at a temperature of 15oC in a similar manner to specific conductance being a standardised value of conductivity at 25oC. Dissolved oxygen was measured utilising a YSI 550A DO instrument. Percent DO saturation was adjusted to account for temperature, salinity and barometric pressure as specified in YSI Inc. (1999). The DO meter was calibrated with oxygen-saturated water in the laboratory prior to transport to the research site and checked with oxygen-saturated water on arrival back from the field. Dissolved oxygen was recalibrated on site in the instrument’s calibration chamber maintained at 100% water-saturated air. Barometric pressure was measured using a Silva Alba Windwatch equipped with a barometer. Oxidation-reduction potential was measured with a YSI pH 100 portable instrument equipped with an ORP probe and values standardised to a hydrogen electrode (Eh). Calibration was validated with
solutions of quinhydrone saturated pH 4 and pH 7 solutions. Turbidity measurements were performed using a Hach Model 2100P portable turbidimeter. Calibration was performed with either Hach StablCal® calibration standards or freshly prepared formazin standards (<0.1, 20, 100 and 800 NTU). Calibration was performed when validation exceeded five percent of a standard. Calibration validation was either determined using Hach StablCal® calibration standards or three Gelex® standards whose values were determined during instrument calibration. Ferrous iron was measured following HACH Method 8146 using 1,10 phenanthroline powder pillows and a Hach Spectrophotometer at 510 nm (Hach Company, 2003). Samples were collected with pre-calibrated digital titrators and diluted to 25 mL in instrument specific glass cuvettes.
2.2.3 Analytical Methods
Most samples collected for analytical analysis were analysed by RJ Hill Laboratories Limited following accredited procedures. Exceptions included TSS and acidity (and alkalinity), which were typically analysed at the University of Canterbury Environmental Engineering Laboratory.
Water samples were analysed for metals using inductively coupled plasma–mass spectrometry (ICP- MS). Dissolved metals were analysed by APHA Method 3125B (APHA, 1998). Total metals were analysed by APHA Method 3125B with nitric acid digestion (APHA, 1998). Metal samples were preserved with 1:1 nitric-acid to reduce pH to <2.0. Dissolved metal samples were filtered during sample collection with 0.45 µm nitrocellulose filters encapsulated in a Pall 47 mm polycarbonate in- line filter holder. All components of the Pall filters were decontaminated by washing in an Alconox solution followed by a tap water rinse, deionised water rinse, a 24-72 hour immersion in a five-percent nitric acid solution followed by a tap water rinse and a final deionised water rinse. Ferric iron was calculated as the difference between total Fe and Fe2+ (analysed in-situ via HACH Method 8146). Sediment samples for total metals were digested with nitric and hydrochloric acid and analysed via ICP-MS following method US EPA 200.2.
Total sulphur was determined using inductively coupled plasma optical emission spectrometry (ICP- OES). Total sulphur concentrations were calculated as mg/L of sulphate assuming 100% of the sulphur was present in the oxidised state based on high DO concentrations and Eh readings. Calcium, Mg, Na and K samples were collected in unpreserved HDPE containers, filtered by RJ Hill Laboratories Limited and analysed following APHA Method 3125B (APHA, 1998). Hardness was calculated using Equation 2.3 where CCa and CMg represent Ca and Mg concentrations, respectively. Total suspended solids were measured following American Public Health Association APHA Method 2540D (APHA, 1998).
Acidity (pH 3.7), total acidity (pH 8.3) and alkalinity (pH 4.5) were either analysed by RJ Hill Laboratories Limited or at the University of Canterbury Environmental Engineering Laboratory. Alkalinity (pH 4.5) was analysed using a modified version of APHA Method 2320B (APHA, 2005). Acidity (pH 3.7) and total acidity (pH 8.3) were analysed using a modified version of APHA Method 2310B (APHA, 2005). Sample pH endpoints for titrations performed by RJ Hill Laboratories Limited were determined using a radiometer autotitrator and method specified indicators. Alkalinity (pH 4.5), acidity (pH 3.7) and total acidity (pH 8.3) were determined from titration curves for samples analysed at the University of Canterbury Environmental Engineering Laboratory. Titrants used were either ~0.02 N or ~0.10 N NaOH. Hot peroxide treatment was performed on all AMD samples to oxidise Fe by adding five drops of 30% hydrogen peroxide (H2O2) and boiling the solution in a covered Erlenmeyer flask for two to three minutes. Samples were allowed to cool to room temperature prior to titration. An EDT Instruments RE357 TX pH meter calibrated with pH 4, 7 and 10 standards was used to measure pH when determining titration curves. Calculated acidity was determined using Equation 2.4 where CFe2+, CFe3+, CAl, CCu, CNi, CZn and CMn represent their respective metal concentrations in mg/L (modified from Watzlaf et al., 2003).
Total Calculated Acidity (mg/L as CaCO3) = 50.045(2 CFe2+/55.85 + 3 CFe3+/55.85 (2.4) + 3 CAl/26.98 + 2 CCu/63.55 + 2 CNi/58.71 + 2 CZn/65.38 + 2 CMn/54.94 + 1000(10-pH)) These metals typically contributed over 99.6% of metal acidity present in samples. The metal acidity represents the equivalent contribution of metals to acidity (Equation 2.4 excluding the 1000(10-pH) term), whereas proton acidity represents the contribution of protons (H+ cations) to acidity.
2.2.4 Flow Measurements
A limited number of samples were analysed from AMD sources deemed unfeasible to construct pilot- scale BGCRs. Consequently, infrastructure was not implemented at these locations to accurately measure flow. Flow was monitored monthly using the bucket and stopwatch method to ascertain flow rates emanating from the Manchester and Collis Seeps. A minimum of five replicates were taken and averaged to determine mean flow during each flow measurement sampling event. Flow was measured from the outlet culvert of Manchester Pond (Figures B.14-B.15). Flow from the Collis Seeps (Figures B.11-B.12) were either measured from the drainage ditch immediately downstream of Seep 3 or from the PVC collection pipes collating Seeps 1 and 3. When flow was measured from the PVC collection pipes the flow from Seeps 1 and 3 were combined to determine total flow.