This document is also available in pdf format:
Open-File
Report 99-193.pdf.
(Note an erratum for page 15.)
New Reporting Procedures Based on Long-Term Method Detection Levels and Some
Considerations for Interpretations of Water-Quality Data Provided by the U.S.
Geological Survey National Water Quality Laboratory
By Carolyn J. Oblinger Childress,
William T. Foreman, Brooke F. Connor,
and Thomas J. Maloney
Table of Contents
Erratum for Open-File Report 99-193
Cover2 (gif file 6K)
Front page (gif file 4K)
Front2 Page (gif file 6K)
Abstract
Introduction
The minimum reporting level
Historical use
of the minimum reporting level at the National Water Quality Laboratory
Limitations of the
minimum reporting level
The method detection limit procedure of the
U.S. Environmental Protection Agency
Limitations
of the procedure
Use by the National
Water Quality Laboratory
The U.S. Geological Survey’s new reporting
procedure based on long-term method detection levels
Setting the reporting level
New reporting conventions
Information-rich
methods
Use of the “E”
remark code by the National Water Quality Laboratory
Planned implementation at the National Water
Quality Laboratory
Considerations for data interpretation
Effect of censoring
on data distribution
Data analysis
Storing data in the National Water Information
System
Enhancements to
remark code in the National Water Information System
Impact on historical
data
Explanation of the reporting convention
for long-term method detection levels for the State annual data reports
Summary
References
Abbreviations and definitions
Figures
- Diagram showing the spike concentration
in relation to the expected method detection limit (MDL)
- Graph showing the frequency distribution
of measured concentrations of chlorobenzene spiked at 0.05 microgram per liter
- Frequency distibution of measured concentrations
of method detection limit (MDL) test samples spiked at 1 to 5 times the expected
MDL concentration and showing one standard deviation (s)
- Standard deviation in relation to concentration
of analyte showing a region of constant standard deviation at low concentrations
- The frequency distribution of the low-concentration
spike measurements is centered on zero concentration to simulate the distribution
expected for replicate blank measurements (analyte not present).
- The U.S. Environmental Protection Agency’s
method detection limit (MDL) is set at a concentration to provide a false
positive rate of no more than 1 percent.
- The long-term method detection level (LT–MDL)
compared to the method detection limit (MDL) determined by the U.S. Environmental
Protection Agency procedure
- False negative probability when a sample
contains the analyte at the method detection limit (MDL) concentration
- The risk of a false negative (not detecting
an analyte when it is present) at the laboratory reporting level (LRL) is
no more than 1 percent.
- New low-concentration reporting conventions showing the reported value and associated
qualifying remark code in relation to the long-term method detection level (LT–MDL), the laboratory reporting level (LRL),
and the lowest calibration standard (LS).
- One-dimensional distribution plots of (A) uncensored data and the same data set censored
by using (B) the MRL procedure, (C) the new reporting procedure, and (D) the new reporting procedure for information-rich methods.
Table
- Examples of different uses for data and their effect on the required level of
certainty and use of qualified data
| Return to
|
Abstract |
