To: GS-W_NAWQA_97_PC,
GS-W_NAWQA_91_PC,
GS-W_NAWQA_94_PC
Cc: jszogors, rgilliom, stoner, cacouch,
ahwelch, pcvanmet, rdeweese, dpkrabbe, sjryker, cory, dhelsel,
tlmiller, wgwilber, bobwill, armbrust, mcyurewi, ijames, sylvest,
GS-W_OWQ_wqspecs,
WRD trace element interest gp:;,wlapham,fwilde,jdmartin,mueller,tschertz,jon,gcdelzer,bfconnor
From: Dennis R Helsel
Date: 02/09/2000 02:57:41 PM
Subject: TE News v.12 Initial blank data results
Trace Element Synthesis News v.12
Results of TE Blank Data from 1991 Study Units
Michael Koterba has completed a preliminary analysis of QC data (blanks)
collected by the 1991 study units and analyzed for trace elements. There
was little national emphasis within the Program on trace elements at that
time (1992-1995), but the procedures we currently use are in many ways
similar to those used by the 91 SUs. Therefore, your data are likely to
have these same limitations. Inadequacies in the coding and completeness
of ancillary information, which prevent the exact causes of the 91
contamination from being known, are also still occurring.
Findings are summarized below. All personnel on your study-unit team who
collect, code, manage, or interpret TE data need to read the full report.
Please see that they get the attached report ("blanks91.doc", a MS Word
document, also found at the TE Synthesis internal web page:
http://water.usgs.gov/nawqa-only/trace/qaqc/91blanks_gwsw.html
Questions should be directed to Michael Koterba (mkoterba).
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* For the 17 trace elements examined, blank contamination
(false positives) appears at similar levels for both
ground and surface water samples.
* The occurrence of contamination in blanks appears random and
inconsequential for As, Sb, Mo, Co, Se, Ni, Pb, Ag, Cd, and Cr.
* The occurrence of contamination in blanks appears to be
systematic and increasing in frequency and magnitude for the
following elements in the order listed:
Ba, Mn, Cu, Zn, and Al.
For example, for Ba, only about 10% of the blanks had
concentration values reported above method reporting or
detection levels; whereas for Al, over 90% of the blanks had
concentration values reported above method report or detection
levels. In addition, while most of these concentration values
were on the order of no more than a few micrograms per Liter for
Ba, many were on the order of tens of micrograms per Liter for Al.
* For Ba, Mn, Cu, Zn, and Al, the blank results imply that the
following data interpretations could be compromised:
(a) descriptions of reference conditions.
(b) comparisons of concentrations among sites, or at different
times at a given site, where differences do not exceed
concentration values typically found in blanks.
(c) comparisons with a standard, where differences between the sample
and the standard do not exceed the cited contamination levels.
For these elements it is crucial to look at the magnitude of blank
contamination in comparison to the objectives of your study.
* Possible sources of the contamination include:
..sample bottles not acid-soaked and pre-rinsed before use.
..filters not pre-rinsed before use with Ocala or equivalent
inorganic-grade water.
..sample-collection equipment not sufficiently cleaned and rinsed
after
previous environmental sample taken.
..use of too little inorganic-grade water, not enough passed through
equipment before taking a field blank.
..sample preservatives used other than NWQL Ultrex acid.
..use of source water other than OCALA Inorganic grade water for
blanks.
..analytical noise from laboratory methods chosen which are not
the NAWQA schedules currently being used.
..coding environmental samples as blanks in the database.
We are currently looking at the 1994 blanks, and will report those results
to you asap. In the meantime, all study-unit personnel should follow the
existing collection protocols so that current contamination sources can be
identified, and problems remedied. The next TE News will summarize those
protocols in one (easy to find) location.
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Visit the TE external page at:
http://water.usgs.gov/nawqa/trace
for up to date info on regulations, publications, etc.
All the TE News thats fit to webify: see the internal page
http://water.usgs.gov/nawqa-only/trace/
Previous TE news blurbs:
v.1 Trace Element Synthesis Staffing and plans 2/10/99
v.2 Changes to TE lab methods for bed sediments 2/19/99
v.3 Well Selection for Subunit Surveys 2/26/99
v.4 Mercury in Streambed Sediments 3/04/99
v.5 Radium in Ground Water 4/08/99
v.6 Elements in Sch 2703 6/14/99
v.7 TEs in stream seds across US 8/18/99
v.8 TE Synthesis: Live and Online 10/04/99
v.9 New Radon Standards proposed by US EPA 10/22/99
v.10 Info for '94 Study-Unit Summary Reports 11/24/99
v.11 TE Schedule change to 2710 2/07/00