| Lake Pontchartrain
Basin: Bottom Sediments and Related Environmental Resources |
Data quality notes
| Annotations based on quality screening techniques are provided in
the qualifier field to the right of each chemical attribute column as illustrated
here. Abbreviations and codes at the beginning of a qualifier field
(for example, AG_Q) are explained below. |
| AG_UG_G |
AG_Q |
| 1.36 |
W |
| 0.009 |
Leach |
| 0 |
<DL |
|
Ratios with zinc provide the
main discriminant function for metals and inorganic constituents. Other appropriate
normalizing constituents can be used for organic compounds (see Manheim and others, 1998).
Values exceeding the indicated ratios are regarded as anomalous. 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.
Table B1. Codes used in qualifier field of
sediment database
[in consolidated table as well as full database, appendixes C and
D]
| Code |
Explanation |
| <DL |
Less than detection limit.
(Concentration reads "0" because the measurement fell below
the detection limit). |
| DV |
Discriminant value (For discussion of
discriminant functions see Analytical Methods and
Quality Control). |
| DVS |
25% of samples for this component and source show
unresolved anomalies in discriminant values. |
| HA |
High Alert (see table
8 for alert levels). |
| LA |
Low Alert (see table
8 for alert levels). |
| Leach |
Leachate method was used for
metal analysis. Values resulting
from this type of analysis have valid uses but are not comparable to those resulting from
total dissolution methods. See Discussion
and Inorganic Chemistry sections for more
explanation. |
| LW |
Source reports data on a wet-weight basis,
which gives lower
apparent values than dry-weight basis. |
| mean (n = *) |
Multiple samples were collected
from the same location and analyzed; the value reported is the mean (n
= number of replicates). |
| ND |
Not detected. |
| Repl. DL |
A replicate value is below detection limit
(the value reported is the mean of the others). |
| W |
Warning: unresolved questions (no quality-control
corroboration or causal relationships for anomalous data are available). |
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 with 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. |
|
Back to Appendix B