Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Methods - water

302 pH

pH is measured by determination of the activity of the hydrogen ions by potentiometric measurement using a combined electrode as described in APHA (2005).

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 4500-H+ B. pH Value / Electrometric Method.

304 Electrical Conductivity

Electrical conductivity is measured directly on a sample with a temperature-compensated meter calibrated using 0.01 M KCl as described in APHA (2005). An estimate of total dissolved solids may be derived from the conductivity using the empirical relationship: Total dissolved solids (mg/L) = Conductivity (µS/cm) × 0.64

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 2510 Conductivity.

306 Total Suspended Solids

Total suspended solids are measured gravimetrically by weighing the fraction remaining on a Whatman 934AH glass fibre filter, dried at 105 °C, after vacuum filtration of a measured volume of sample. The method is described in APHA (2005).

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 2540 D. Total Suspended Solids Dried at 103 - 105 °C.

308 Total Dissolved Solids

Total dissolved solids are measured gravimetrically by weighing that fraction passing through a Whatman 934AH glass fibre filter, dried at 105 °C, after vacuum filtration of a measured volume of sample. The method is described in APHA (2005).

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC.

310 Total Organic Carbon

Total carbon is measured using an Analytik Jena Multi-NC TOC analyser. Water is combusted at high temperature in the presence of a platinum catalyst to produce CO2, which is then measured in an infrared cell. Inorganic carbon is measured separately by decomposition to CO2 in an acidified reactor vessel. Total organic carbon is determined by difference from the measured TC and IC readings. The method is described in APHA (2005).

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 5310 B. Total Organic Carbon/ High Temperature Combustion Method.

314 Ammonia, Nitrate, Nitrite and Phosphate by Flow Injection Analysis

NH4-N is determined colorimetrically using the indophenol reaction with sodium salicylate and hypochlorite (Lachat 1998c), NO3-N by Cd reduction and NEDD colorimetry (Lachat 1998d), while orthophosphate, PO4-P, reacts with ammonium molybdate and antimony potassium tartrate under acidic conditions then a molybdenum blue complex is formed after ascorbic acid reduction (Lachat 1998f). All are performed with a QuikChem 8500 flow injection analyser.

  • Lachat Instruments, Milwaukee, WI, USA. 1998c Quik Chem Method 12-107-06-3-A.
  • Lachat Instruments, Milwaukee, WI, USA. 1998d Quik Chem Method 12-107-04-1-B.
  • Lachat Instruments, Milwaukee, WI, USA. 1998f Quik Chem Method 12-115-01-1-A.
  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 4500-NH3 H. Flow Injection Analysis. Method 4500-NO3 I. Flow Injection Analysis. Method 4500-P G. Flow Injection Analysis.

316 Total Nitrogen and Phosphorus

Inorganic and organically bound nitrogen is converted to free nitrate by digestion at elevated temperature in an autoclave using an alkaline solution of potassium persulphate. The procedure also provides simultaneous digestion of unreactive phosphorus to orthophosphate. The digestion is described by Hosomi & Sudo (1986).

NO3-N is determined colorimetrically by Cd reduction and NEDD colorimetry (Lachat 1998d), while orthophosphate, PO4-P, reacts with ammonium molybdate and antimony potassium tartrate under acidic conditions then a molybdenum blue complex is formed after ascorbic acid reduction (Lachat 1998f), both using a QuikChem 8500 flow injection analyser.

  • Hosomi, M. and Sudo, R. 1986. Simultaneous determination of total nitrogen and total phosphorus in freshwater samples using persulphate digestion. International Journal of Environmental Studies 27: 267 - 275.
  • Lachat Instruments, Milwaukee, WI, USA. 1998d Quik Chem Method 12-107-04-1-B.
  • Lachat Instruments, Milwaukee, WI, USA. 1998f Quik Chem Method 12-115-01-1-A.
  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 4500-NO3 I. Flow Injection Analysis. Method 4500-P G. Flow Injection Analysis.

318 Calcium, Magnesium, Potassium and Sodium

These metals are determined by optical emission spectroscopy with inductively coupled plasma excitation (ICP-OES) using a Spectro Genesis ICP-OES.

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 2340 B. Hardness by Calculation. Method 3120 B Inductively Coupled Plasma (ICP) Method.

320 Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, & Zn

These metals are determined by optical emission spectroscopy with inductively coupled plasma excitation (ICP-OES) using a Spectro Genesis ICP-OES.

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 313120 B Inductively Coupled Plasma (ICP) Method.

322 Aluminium (formerly 326)

Aluminium is determined by optical emission spectroscopy with inductively coupled plasma excitation (ICP-OES) using a Spectro Genesis ICP-OES.

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 313120 B Inductively Coupled Plasma (ICP) Method.

324 Silicon (formerly 336)

Silicon is determined by optical emission spectroscopy with inductively coupled plasma excitation (ICP-OES) using a Spectro Genesis ICP-OES.

  • Standard Methods for the Examination of Water and Wastewater. 21st Edition. (2005) American Public Health Association, Washington DC. Method 313120 B Inductively Coupled Plasma (ICP) Method.

342 Chloride

Chloride is normally determined as part of the suite of anions measured by ion chromatography. However, if chloride is the only anion required then the colorimetric method of Skougstad et al (1979) is simpler and faster. Chloride ions react with mercuric thiocyanate to produce mercuric chloride and liberate thiocyanate ions. In the presence of ferric salts, these thiocyanate ions produce a characteristic orange colour, the intensity of which is proportional to the chloride ion concentration.

  • Skougstad, M.W., Fishman, M.J., Friedman, L.C., Erdmann, D.E. and Duncan, S.S. 1979. Methods for determination of inorganic substances in water and fluvial sediments. Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1, 331-332.