| Environmental Geochemistry and
Sediment Quality in Lake Pontchartrain |
Data quality notes
One or two-letter uppercase codes at beginning of the quality-control field, (e.g.
AG_Q) are explained below. Other text is self-explanatory. Ratios with zinc provide the
main discriminant function for metals and inorganic constituents. Other appropriate
normalizing constituents are utilized for organic compounds. Values exceeding the
indicated ratios are regarded as anomalous. Where no quality-control corroboration or
causal relationships for anomalous data are available, the sample in question is given a
"W" or warning designation. No quality-control column in the Consolidated data
sheet (Appendix C) means the field had no annotations. Alert
level calls attention to unusual concentration levels. It does not necessarily imply data
quality problems. High alert levels are normally due to presence of contaminants. Low
alert levels may signify sediment mineralogy that is naturally low in trace metals, or a
leachate procedure designed to recover contaminants but not more refractory trace elements
in unpolluted sediments.
Also note: "0" in a concentration field means that the constituent was
below detection limit for the method utilized.
Table 8. Codes used in Quality Control Field of Sediment
Database
Code |
Explanation |
| DV |
Discriminant value (For discussion of
discriminant functions see section D, "Analytical Methods and
Quality Control") |
| DVS |
25% of samples for this component and source show
unresolved anomalies in discriminant values. |
| HA |
High Alert (see Appendix B
for Alert Levels) |
| LA |
Low Alert (see Appendix B
for Alert Levels) |
| LL |
Leachate method may yield low or variable
recovery of metals in natural sediment matrix |
| LW |
Source reports data on a wet-weight basis = lower
apparent values than dry-weight basis. |
| N |
Insufficient data to check quality |
| W |
Warning: unresolved questions |
EMAP-specific quality codes:
| CH-A |
Analyte was not detected (Method Detection Limit reported as the variable
DETLIMIT). |
| CH-B |
Analyte detected, but below Method Detection Limit - Use w/ discretion. |
| CH-C |
Lab experienced minor deficiencies meeting the QC requirements; Reliable
for EMAP assessments. |
| CH-I |
Co-elution; Matrix Interference. |
| CH-N |
No sediment sample taken in the field. |
| CH-X |
Analyte not required by EMAP protocol -- not reported here; may be
included in other data sets. |
| CH-Z |
Missing concentration value because all constituent analytes were
non-detects. |
see also, Table 9: Other interpretive notes and
Table 10: EPA station class codes
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