Table 5-1

Table 5-1: Methods for Geochemical Characterization

Return to: 5.3.2 Description of Phases

Test Type	Test Methods and Description	Use in Geochemical Characterization and Water Quality Prediction	Advantages	Limitations
Grain Size	Sieve	Predict reactivity on basis of available surface area	Relatively rapid, less expensive	Little information on fine fraction No information on "reactive" fraction
	Hydrometer		Information on fine fraction	More time consuming, more expensive No information on "reactive" fraction
	BET method		Sophisticated technique Information on "reactive" fraction through measurement of total and specific surface area	Time consuming and expensive Requires specialized equipment and personnel
Chemical Composition	Digestion using various acids for analysis by multiple quantitative techniques (ICP-AES, ICP-MS, AAS, NAA)	Determines total potential load of constituents to environment.	Comparison against site-specific baseline values and reference geologic materials Surrogate for and confirmation of ABA parameters (e.g., Ca, S) Surrogate for and confirmation of mineralogical composition Evaluation of sample set representativeness	Instrument-specific interferences Volatilization Elevated detection limits due to dilution
	Preparation of bead/powder sample for semi-quantitative analysis by XRF
	Portable equipment (XRF)
Paste pH/Paste Conductivity	Mixture of solution and solid in desired ratio (typically 1:1 to 5:1) followed by pH/electrical conductivity measurement	Determines potential short-term effect of surficial/soluble salts on water quality	Quick, inexpensive, easy to perform in field and laboratory Can be useful monitoring test for operational mine waste management	Lack of ability to predict long-term conditions Measures stored acidity
Acid Base Accounting (ABA)	Sobek Method AP commonly from total sulphur NP by boiling, HCl to pH 0.8-2.5	All Methods: Establish overall acid generating and acid neutralizing capability of a material through independent determination Identification of the need for and samples that require kinetic testing	All Methods: Most techniques well established Generally relatively fast and inexpensive Provide operational screening criteria for mine waste classification and management	All Methods: Provide no information on relative rates of acid generation and neutralization Assume NP and AG sulfur or minerals are completely available for reaction Can over- or under-estimate AG or NP depending on method used NPR cannot be calculated in the absence of sulphur and sulphide Acid addition dependent on a subjective fizz test which can affect accuracy
	Modified Sobek (Lawrence Method) AP from sulphide sulphur NP at ambient temperature for 24 hours near boiling, HCl to pH 2.0-2.5		Prevent over-estimation of NP or AP relative to Sobek method Widely used
	Lapakko NP at ambient temperature up to 1 week, H2SO4 to pH 6.0
	BC Research Inc. (BCRI) Initial NP at ambient temperature for 16-24 hours, H2SO4 to pH 3.5
	Sobek Siderite Correction as Sobek, but with H2O2	Accounts for complete oxidation of soluble metals during titration	ASTM draft method uses sulphuric acid Requires no fizz test Uses pH to determine acid addition requirements Negative values indicate stored acid
	Net Carbonate Value (NCV),%CO2 NCV = ANP + AGP, where AGP = -1.37[(total sulphur) - (residual sulphur after pyrolysis)] ANP = 3.67[(total carbon) - (carb on after HCl digestion)] (=see TIC)	Developed by Newmont Negative ANP and positive AGP must be corrected to zero Negative NCV indicates acid generation potential Confirm NCV classification using BC Research Confirmation on zone composites	Standardized as ASTM E-1915 Waste rock composites characterized with metallurgical suite for ores Several options for sulphide confirmation depending on mineralogy Classification system limits uncertainty	Requires carbon-sulphur sophisticated combustion-infrared instrumentation similar to Sobek Results require conversion for comparison against data from other ABA tests in order to differentiate methods Metal carbonates overestimate ANP Does not account for silicate buffering or stored acidity
	Acid Buffering Characteristic Curve (ABCC) Titration of sample with acid while continuously monitoring pH	Provides an indication of the portion of the NP that is readily available for neutralization Used principally in Australia Similar in nature to the BCRI Initial test	Can be used to identify minerals responsible for neutralization by comparing against ABCCs for reference minerals Well suited for measuring actual NP vs. total NP Represents a less conservative method of measuring NP	Only feasible to do on selected samples due to long test time Limited basis for comparison against results from more "traditional" ABA tests due to limited use to date
	Total Inorganic Carbon (TIC) TIC = (total carbon) - (carbon after HCl digestion)		Measures NP associated with carbonates only	Only provides carbonate fraction of NP Can only be used in concert with total NP results Will include carbonates that do not contribute NP (e.g., siderite) Not suitable for materials with low NP
	Sulphur Analysis (total S, pyritic S, sulphide S, organic S, sulphate S, residual S) Analysis requires selective digestion of ground sample and measurement of sulphur by infrared or titration after combustion Removal of non-sulphide and/or targeted sulphide minerals to determine sulphur species	Potential of samples to generate acid Used as part of ABA testing	Distinguishes between sulphur forms and allows identification of "reactive" sulphur species	Does not confirm the identity of the sulphur-bearing mineral(s) Can overestimate or underestimate reactive sulphur content
	Chromium Reducible Sulphur Targets acid-volatile sulphur, elemental sulphur and pyrite sulphur through HCl digestion	Used principally in acid sulphate soils investigations. CRS is also useful for sulphide analysis in coal and coal reject materials	Considered a very reliable method for measuring low-level sulphur concentrations Only measures sulphide minerals	Limited basis for direct comparison against results from more "traditional" ABA tests
	Total Actual Acidity (TAA) Titration of KCl extract to pH 5.5 with NaOH		Can define actual acidity in low-pH samples that have oxidized
	Total Potential Acidity (TPA) Heating of KCl extract with H2O2 and titration to pH 5.5 with NaOH
Net Acid Generating (NAG)	Single addition NAG Reaction with H2O2, measurement of the NAG pH and titration to pH 4.5 and pH 7.0 with NaOH	All Methods: Establishes overall acid generating capability of a material through simultaneous reaction of acid generating and acid neutralizing components Identification of the need for and samples that require kinetic testing Used in conjunction with ABA or stand alone field test when calibrated	All Methods: Evaluates net acid-base balance Generally relatively fast and inexpensive Provides operational screening criteria for mine waste classification and management Greatly reduces false positive and false negative ABA results Confirmation results for unreactive materials In combination with ABA improves prediction reliability and range of uncertainty	All Methods: Does not distinguish between AP and NP Potential interferences in presence of organic carbon and copper May underestimate ARD potential in high-sulphide material due to incomplete oxidation (Sequential NAG addresses this limitation) Quality of H2O2 may vary: some H2O2 brands required pre-treatment for NAG test use
	Sequential NAG Multi-stage repeat of single-addition NAG tests until NAG pH is greater than 4.5		Overcomes incomplete oxidation in high-sulphur samples Can provide qualitative estimate of approximate lag time to acid generation
	Extended Boil and Calculated NAG As single addition NAG, but accounts for potential effect from organic matter Extended boiling and assay of the NAG solution for S, Ca, Mg, Cl, Na and K		Accounts for potential effect from organic matter
	Kinetic NAG As single addition NAG but with monitoring of temperature and pH during reaction with H2O2		Provides qualitative estimate of reaction kinetics and lag time (i.e., weeks, months, years)
Mineralogical Composition	Visual/Optical Microscopy Hand lens, binocular microscope	All Methods: Identify primary and secondary minerals that could affect acid generation potential and contact water quality With increasing sophistication of techniques, also information on texture, mineral composition and morphology to evaluate mineral reactivity and availability for weathering reactions that can affect acid generation and leaching potential	All Methods: Provide information on acid generating potential and NP, availability of minerals for weathering Corroborate lithologic information Essential for understanding of geochemical controls on contact water quality and as inputs to geochemical model simulations	Qualitative
	X-ray diffraction (XRD) Qualitative or semi-quantitative (Rietveld) analysis			Semi-quantitative at best High detection limit ~1% Capable of identifying crystalline minerals only
	Petrographic analysis Reflection or transmission petrographic microscope			Requires sophisticated instrumentation and specialized personnel for interpretation
	SEM/EDS Electron beam scan for mineral identification		Surpasses combustion-infrared methods in quantifying trace sulfide mineral concentrations
	Electron microprobe Like SEM but optimized for chemical analysis
	Portable equipment (PIMA) Infrared analyzer		Portable Particularly suited for hydrated minerals	Not capable of identifying all minerals
Short-Term Leach Tests	SPLP (Synthetic Precipitation Leaching Procedure) US EPA Method 1312 20:1 solution to solid Deionized water or dilute sulphuric/nitric acid to pH 4.2 or 5.0 < 9.5 mm 18 ± 2 hours Variant: Standard Test Method for Shake Extraction of Mining Waste by the Synthetic Precipitation Leaching Procedure ASTM D 6234	All Methods: Measures readily soluble constituents of mine and process wastes	All Methods: Provides indication of short-term leaching of soluble constituents. Identifies readily dissolvable constituents	All Methods: Provides no information on transient processes and long-term conditions. Only simulates short-term interaction High liquid to solid ratio may underestimate leachability Grain size reduction may increase reactivity
	TCLP (Toxicity Characteristic Leaching Procedure) US EPA Method 1311 20:1 solution to solid ratio acetic acid/acetate buffer < 9.5 mm 18 ± 2 hours	Used to determine if waste is hazardous under RCRA Intended to simulate municipal landfill containing organic wastes	Applicable standards available	Use of acetic acid/acetate buffers not appropriate for mining applications, Short list of metals evaluated
	Meteoric Water Mobility Procedure (MWMP) 1:1 solution to solid ratio reagent-grade water < 2 inch < 48 hours	Same as for SPLP Primarily used in Nevada	Quasi-dynamic test More realistic than SPLP due to higher solid to solution ratio, longer duration and coarser material Applicable standards available	Weaker lixiviant than acidified SPLP
	California Waste Extraction Test (WET) 10:1 solution to solid ratio dilute sodium citrate solution < 2 mm 48 hours	Intended to simulate municipal landfill containing organic wastes Primarily used in California	Lower liquid to solid ratio and longer test duration than SPLP and TCLP Applicable standards available	Use of sodium citrate not appropriate for mining applications
	Modified Test for Shake Extraction of Solid Waste with Water 4:1 solution to solid ratio reagent-grade water adjusted to pH 5.5 with carbonic acid 18 hours	Same as for SPLP	Lower liquid to solid ratio than SPLP
	British Columbia Special Waste Extraction Procedure (BC SWEP) 20:1 solution to solid ratio acetic acid < 9.5 mm 24 hours Modification for mining wastes 3:1 solution to solid ratio dilute hydrochloric acid	Similar to TCLP for normal procedure Similar to SPLP and ASTM for modified procedure	Modified: lower solution to solid ratio than SPLP and ASTM	Intended to simulate municipal landfill containing organic wastes Same as for SPLP
	NAG Test with Leachate Analysis 100:1 solution to solid ratio 15% H2O2 solution < 75 um Until boiling or effervescing ceases	Can be used to determine total potential loading or release of metals after complete oxidation of reactive sulphides	"Short-cut" to conditions representative of complete sulphide oxidation	Leachate contains all reaction products from sulphide oxidation High solution to solid ratio Significant grain size reduction
	Characterization of Waste - Leaching - Compliance Test for Leaching of Granular Materials and Sludge EN 12457 1 One stage test 2:1 solution to solid ratio < 4 mm EN 12457-2 One stage test 10:1 solution to solid ratio < 4 mm EN 12457-3 Two stage test 2:1 and 8:1 solution to solid ratios < 4 mm EN 12457-4 One stage test 10:1 solution to solid ratio < 10 mm All Methods: distilled/demineralized/deionized water 24 hours	All European Union (EU) Methods: Basic characterization: obtain information on leaching behavior and characteristics Compliance: determine whether waste complies with specific reference values	All European Union (EU) Methods: Test protocol is adjusted based on information needs and site-specific conditions Applicable standards available (expressed as loadings)	Same as for SPLP
	Characterization of Waste - Leaching Behavior Tests - Up-flow Percolation Test CEN/TS 14405 10:1 solution to solid ratio < 10 mm demineralized water duration as needed	Used to determine leachability of a waste under hydraulically dynamic conditions (EU)	Test can be used to establish the distinction between various release mechanisms (e.g., first flush vs. steady state leaching)	Same as for MWMP Test developed for landfills
	Characterization of Waste - Leaching Behavior Tests - Influence of pH on Leaching with Initial Acid/Base Addition CEN/TS 14429 10:1 solution to solid ratio at least 8 individual solutions of different pH using nitric acid or sodium hydroxide covering the range pH 4-12 95% < 1 mm 48 hours	Used to determine influence of pH on waste leachability and buffering capacity (EU)	Leachate analyzed for inorganic constituents (as opposed to prCEN/TS 15364) pH is allowed to fluctuate after initial addition of acid or base Allows evaluation of buffering capacity	Same as for SPLP Test developed for landfills
	Characterization of Waste - Leaching Behavior Tests - Influence of pH on Leaching with Continuous pH-Control EN 14997 10:1 solution to solid ratio at least 8 individual solutions of different pH using nitric acid or sodium hydroxide covering the range pH 4-12 95% < 1 mm 48 hours	Used to determine influence of pH on waste leachability (EU)	Leachate analyzed for inorganic constituents (as opposed to prCEN/TS 15364) pH is maintained at constant value after initial addition of acid or base Allows evaluation of leachability under constant pH	Same as for SPLP Test developed for landfills
	Characterization of Waste - Leaching Behavior Tests - Acid and Base Neutralization Capacity Test CEN/TS 15364 10:1 solution to solid ratio at least 8 individual solutions of different pH using nitric acid or sodium hydroxide covering the range pH 4-12 95% < 1 mm 48 hours	Used to determine final pH of a waste as well as assess consequences of external influences (carbonation, oxidation) on the final pH (EU)		Same as for SPLP Test developed for landfills Leachate only analyzed for pH
	Lixiviação de Resíduos NBR 10005 16:1 solution to solid ratio acetic acid < 9.5 mm 24 hours	Used to determine if mine waste is hazardous under solid waste regulations (Brazil) Intended to simulate municipal landfill containing organic wastes	Applicable standards available	Use of acetic acid not appropriate for mining applications
	Solubilização de Resíduos NBR 10006 4:1 solution to solid ratio deionized water grain size not specified 7 days	Used to evaluate potential for impacts to groundwater by comparison against groundwater quality standards (Brazil)	Applicable standards available Lower solution to solid ratio and longer duration than SPLP	Same as for SPLP
	Test Method Standard for Leaching Toxicity of Solid Wastes - Roll Over Leaching Procedure GB5086.1-1997 10:1 solution to solid ratio deionized/distilled water < 5 mm 18 hours	Used to determine if mine waste is hazardous under solid waste regulations by comparison against Integrated Wastewater Discharge Standards (China)	Applicable standards available	Same as for SPLP
	Test Method Standard for Leaching Toxicity of Solid Wastes - Horizontal Vibration Extraction Procedure GB5086.2-1997 10:1 solution to solid ratio deionized/distilled water < 3 mm 24 hours	Used to determine if mine waste is hazardous under solid waste regulations by comparison against Integrated Wastewater Discharge Standards (China)	Applicable standards available	Same as for SPLP
	Sequential Extraction Variety of methods using different extractants to evaluate leachability from targeted fractions of mine waste Methods may vary depending on analyte of interest and target fraction of interest	To evaluate associations between constituents of interests and different fractions of the solid Allows for determination of the labile portion of the solid phase	Understanding associations of constituents with different fractions of the solid assists in understanding geochemical conditions under which they may be released to the environment	Involved procedure Many reagents Most reagents not uniquely selective to targeted fraction Use of some reagents precludes analysis of certain constituents No applicable standards
Long-Term Leach Tests	Humidity Cell Test (HCT) ASTM D5744-96 0.5:1 or 1:1 solution to solid ratio deionized water different dimensions for < 6.3 mm and <150 μm weekly cycle of 3-day alternating dry air and wet air followed by leach generally 20-week minimum but can run longer weekly analysis of diagnostic ARD parameters (e.g., pH, SC, Fe, SO4, Eh, Ca, Mg, alkalinity) generally less-frequent analysis for comprehensive metals and major ions	To determine long-term weathering rates (sulphide oxidation, dissolution of neutralizing minerals, trace metal release) under oxygenated conditions To evaluate lag time to acid generation To provide reaction rates for geochemical modeling	Standardized test Provides kinetic and steady-state leaching information and is recommended test for determination of weathering rates of primary minerals	Not suitable for evaluation of saturated materials Grain size reduction may increase reactivity Potential for channel flow High leaching rate can affect reaction kinetics due to higher pH and undersaturation with secondary minerals
	Column Test variable solution to solid ratio generally deionized water, groundwater or natural precipitation generally < 25 mm variable dimension, but generally larger than HCT leaching cycles can vary and include maintaining water over sample, alternate flooding and draining, and recirculating leachate	As above, but can simulate leaching in variably saturated or oxygen-deficient conditions To simulate environmental performance of amended mine wastes and/or cover designs	Frequently closer to field conditions than HCT Can simulate different degrees of saturation Can simulate remedial alternatives Simulates combined weathering of primary and secondary minerals	Not standardized Potential for channeling through preferential flowpaths Grain size reduction may increase reactivity Without entire load of weathering products from primary minerals, reaction rates for primary minerals and extent of secondary precipitation cannot be measured
Field Tests	Wall Washing 1L rinse of 1 × 1 m surface area distilled water	All Methods: To estimate short and long-term potential of mine materials to generate acid and leach metals using on-site materials	Rapid Measures leachate quality from in situ material Can be repeated to obtain temporal component	May be difficult to establish accurate mass balance due to loss of solution
	US Geological Survey Field Leach Test (FLT) 20:1 solution to solid ratio deionized water < 2 mm 5 minutes http://pubs.usgs.gov/tm/2007/05D03/		Can be performed in the field Rapid and inexpensive method to characterize chemical reactivity and water-soluble fraction Field screening method that can be used as surrogate for SPLP due to similarity in approach and results	Same as for SPLP
	Field Cells/Test Pads/Mine Facilities Monitoring of increasingly larger volumes of mine wastes Ambient precipitation or irrigation Degree of grain size reduction required decreases with increasing size of test Test duration months to years		Test are conducted under actual field conditions Can collect samples after transient events Larger sample size results in enhanced test charge representativeness With increasing test size, effects from grain size reduction, sample heterogeneity and preferential pathways reduced With increasing test size, empirical results increasingly directly applicable to mine facility	Comprehensive characterization of test sample may not be feasible Complete understanding of water balance may not be feasible Complexity of tested system may limit interpretive and predictive value of observations

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Return to: 5.3.2 Description of Phases