The U.S. Geological Survey (USGS) has sponsored a number of studies to evaluate its sampling, processing, and analytical procedures for filtered water samples. The major findings of these studies were that surface-water sampling and processing procedures and equipment used in USGS programs were inadequate to produce contaminant-free trace-element data on a consistent basis. This led to development of a new protocol for collecting, processing, and analyzing filtered water samples for the analysis of trace elements at the 1 microgram-per-liter (ug/L) level using “clean” procedures. The protocol specifies (1) supplies, (2) office and between-site cleaning procedures, (3) samplers, (4) sample splitters, (5) use of disposable capsule filters, (6) quality-assurance measures including use of disposable gloves and shelters for sample processing, and (7) quality-control requirements including blanks, replicates, and split samples.

The USGS is now implementing this protocol for all USGS efforts to produce trace-inorganic data at the microgram-per-liter level on filtered water samples. The protocol will also be used for collecting and processing samples for major ions and nutrients when trace-elements are also being determined.