README_BST.TXT - Readme file for Bed sediment and Tissue Study - NAWQA NECB

WHAT IS AN RDB FILE?

An RDB file is an ASCII file that has been exported from a relational database 
(RDB) and maintains the tabular structure so it can be imported to any common 
spreadsheet or database program.  The data are provided in tab-delimited columns 
with the first row being the Column Header Names and the second row indicating 
the field length and data type of each ('S' for a character field; 'D' for a 
date field; 'N' for a number field; for example '12S' indicates a character field
of length 12). The data are preceded by lines of documentation or explanatory 
text. Any row containing such comments starts with a '#' sign. 

Since the RDB files are text-based, they are easily viewable in a web browser or
any word-processing program like MS Word or Notepad. However, those programs will
not format the data into correctly-aligned columns, because the files are 
tab-delimited (the columns do not have fixed widths). These tables are provided 
with the intention that they will be easily imported into a spreadsheet or 
database program (such as Quattro Pro, SAS, Access, Paradox, etc.).


WHAT IS A DETECTION?

Until recently (2000), results of laboratory analyses by the USGS were reported
either as quantified above or below (using the less than, <, symbol) a 
Laboratory Reporting Level (LRL). Recent improvements in laboratory analytical
techniques, however, enable a chemist to report an estimated concentration when
a compound meets all identification criteria, but the concentration value is 
less than the LRL (Connor and others, 1998; Childress and others, 1999). In rare
instances, a compound is reported at estimated concentrations above the standard
LRL because of laboratory uncertainty about the actual concentration measured.
These problems are usually related to the performance of the laboratory
instruments, interference created by other compounds in the water sample (such 
as hydrogen sulfide), or inherent instability of the compound being measured. 
Some of the water-quality results are further censored with the 'M' value 
because the concentrations detected were so low that they were effectively 
rounded off to zero.


QUALITY ASSURANCE/QUALITY CONTROL SAMPLES

The water-quality data tables provided on this website are only for 
environmental samples (actual streambed sediment and fish tissue samples). In 
addition to the environmental samples, the NECB study collected quality 
assurance/quality control (qa/qc) samples that were appropriate for the type of 
environmental samples being collected. For fish tissue samples, no qa/qc samples 
were collected.  For streambed sediment samples, one site had duplicate samples 
collected to test for consistency in sample collection and analysis. This one 
duplicate sample did not indicate inconsistencies in sample collection or analysis.

Anyone wishing to obtain the qa/qc data, please contact Ann Chalmers of the 
NECB study unit at chalmers@usgs.gov.


REFERENCES

Childress, C.J.O., Foreman, W.T., Connor, B.F., and Maloney, T.J., 1999, 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: U.S. Geological Survey 
Open-File Report 99-193, available ON-LINE at 
http://water.usgs.gov/owq/OFR_99-193/index.html

Connor, B.F., Rose, D.L., Noriega, M.C., Murtagh, L.K., and Abney, S.R., 
1998, Methods of analysis by the U.S. Geological Survey National Water 
Quality Laboratory--Determination of 86 volatile organic compounds in water
by gas chromatography/mass spectrometry, including detections less than 
reporting limits: U.S. Geological Survey Open-File Report 97-829, 78 p.,
available ON-LINE at http://nwql.usgs.gov/Public/pubs/OFR97-829.html