2008 - 2009 NRSA Mercury Fish Tissue Data Dictionary 
March 2013 
 
Field 
 Description 
 
State 
 USPS 2-letter abbreviation for the state in which the sample was collected  
 
Site ID 
 9-character ID assigned by EPA.  The first two characters are “FW,” for “flowing waters”, the next two are the site selection year (08), followed by two characters for the state abbreviation, and a three-digit identifier for sites within the state. 
 
River Name 
 The name of the river from which the sample was collected 
 
Stream Order 
 A measure of stream position within a drainage network system.  Streams that have no tributaries flowing into them are called first-order streams.   Streams in this study range from fifth-order (5) to greater than eight-order (8+). 
 
Lat 
 Latitude, in decimal format 
 
Long 
 Longitude, in decimal format 
 
Year 
 The year in which the sample was collected, in YYYY format 
 
Sampling Date 
 Actual sampling date, in MM/DD/YYYY format 
 
Site Type 
 Urban, Non-urban designation (based on Census Bureau GIS data) 
 
Sample ID 
 Unique 6-digit number assigned by EPA  
 
Sample Type 
 Only Primary samples are reported here. 
 
Composite Classification 
 Routine vs. Non-routine composite, based on the sampling design document 
 
Species Name 
 Latin name (Genus and species) based on Nelson et al. (2004) Common and Scientific Names of Fishes from the United States, Canada, and Mexico, Sixth Edition 
 
Common Name 
 Generally accepted common name based on Nelson et al. (2004) 
 
Analyte 
 Mercury 
 
CAS Number 
 Chemical Abstracts Service Registry Number assigned by CAS to the analyte. 
 
Amount 
 Concentration, if detected.  If this field is blank, the analyte was not detected in the sample.  For the purpose of this report, all amounts are reported to two decimal places.  However, the results have at most three significant figures, regardless of the number of digits displayed (e.g., 353.53 vs. 354). 
 
MDL 
 Method detection limit for the analyte, based on the procedure in 40 CFR part 136.  The MDL was determined twice over the course of this study, so one of two values will appear in this column, depending on when the sample was analyzed. 
 
Unit 1 
 The weight/weight units (e.g., ng/g) and the wet-weight designation 
 
Unit 2 
 The “parts per billion” notation ppb, which is equivalent to ng/g 
 
Lab Qualifiers 
 Qualifiers applied by the laboratory.  The five individual qualifiers applied to the mercury results were: 
B5 = Mercury was detected in the method blank above the MDL, but below the reporting limit. 
M1 = Matrix spike recovery was high; the associated lab fortified blank spike recovery was acceptable 
M2 = Matrix spike recovery was low; the associated lab fortified blank spike recovery was acceptable 
M3 = Matrix spike recovery was high. 
M5 = The spike recovery is unusable since the analyte concentration in the sample is disproportionate to the spike level. The associated lab fortified blank was acceptable. 
 
Validator Flags 
 Qualifiers applied by the Sample Control Center staff at CSC during data validation.  The four individual qualifiers applied to the mercury results were: 
B, RNAF = Blank result above the MDL, but sample result not affected 
HMSR = High matrix spike recovery 
LMSR = Low matrix spike recovery 
INSL = Insufficient spike level 
 
%  Moisture 
 The percent moisture determined on a separate aliquot of each sample 
 

 

