The effect of membrane filtration on dissolved trace element concentrations
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 As such, simple filtration through a 0.45-μm membrane filter may no longer represent an acceptable operational definition for dissolved chemical constituents.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.
Keywordsmembrane filters filtration filtration artifacts dissolved major elements trace elements
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- APHA-AW WA-WPCF: 1989,Standard Methods for the Examination of Water and Wastewater, 17th Ed., 1193p.Google Scholar
- ASTM: 1995,Annual Book of ASTM Standards, Vol 11.01, Water (I), 814p.Google Scholar
- Brewer, P.G. and Spencer, D.W.: 1970,Trace Metal Intercalibration Study. , Woods Hole Oceanographic Institute, Report No. 70-62.Google Scholar
- Bruland K.: 1983, Trace Elements in Sea-Water, InChemical Oceanography,5, (Edited by Riley, J., Chester, R.), 157–220.Google Scholar
- Horowitz, A.J., Demas, C.R., Fitzgerald, K.K.,et al.,: 1994,U.S. Geological Survey Open-File Report No. 94-539, 56p.Google Scholar
- Jones, P.G.W.: 1978,International Council for the Exploration of the Seas. Copenhagen, ICES, CM 19787/E:16.Google Scholar
- Ledin, A.: 1993,Colloidal Carrier Substances — Properties and Impact on Trace Metal Distribution in Natural Waters., Linkoping Studies in Arts and Science No. 91.Google Scholar
- Office of Water Data Coordination: 1984,National Handbook of Recommended Methods for Water-Data Acquisition., Chapter 5, 5-14-5-15.Google Scholar
- U.S. Environmental Protection Agency: 1983,Methods for Chemical Analysis of Water and Wastes EPA-600/479-020, 375 p.Google Scholar