Article

Water, Air, and Soil Pollution

, Volume 90, Issue 1, pp 281-294

The effect of membrane filtration on dissolved trace element concentrations

  • Arthur J. HorowitzAffiliated withU.S. Geological Survey, Peachtree Business Center
  • , Ken R. LumAffiliated withCentre Saint-Laurent, Environment Canada
  • , John R. GarbarinoAffiliated withU.S. Geological Survey, Branch of Analytical Services
  • , Gwendy E. M. HallAffiliated withGeological Survey of Canada
  • , Claire LemieuxAffiliated withCentre Saint-Laurent, Environment Canada
  • , Charles R. DemasAffiliated withU.S. Geological Survey

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Abstract

The almost universally accepted operational definition for dissolved constituents is based on processing

The almost universally accepted operational definition for dissolved constituents is based on processing whole-water samples through a 0.45-μm membrane filter. Results from field and laboratory experiments indicate that a number of factors associated with filtration, other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample), can produce substantial variations in the ‘disolved’ concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. These variations result from the inclusion/exclusion of colloidally-associated trace elements. Thus, 'dissolved' concentrations quantitated by analyzing filtrates generated by processing whole-water through similar pore-sized membrane filters may not be equal/comparable. As such, simple filtration through a 0.45-μm membrane filter may no longer represent an acceptable operational definition for dissolved chemical constituents. This conclusion may have important implications for environmental studies and regulatory agencies.

Keywords

membrane filters filtration filtration artifacts dissolved major elements trace elements