Blind Sample Program (BSP) Data

The BSP quality-control data published on the CD-ROM include 34 dissolved chemical constituents for the water years 1985 to 1995. These data apply to the laboratory methods used to analyze WQN stream water-quality samples for dissolved chemical constituents during this period.

The purpose of the BSP is to monitor, assure, and improve the quality of laboratory analytical results through the use of blind quality-control samples. The BSP regularly submits to participating USGS laboratories reference water samples having known chemical concentrations and consisting of a stable, homogeneous chemical and physical matrix. The reference samples are subject to the identical laboratory handling, processing, and analytical procedures as those applied to environmental samples.

BSP samples have been used by the USGS as an independent source to verify the accuracy (bias and variability) of laboratory analytical methods and ambient water-quality measurements. Estimates of the bias and variability of laboratory analytical measurements provide quantitative information about the extent to which lab methods contribute to systematic and random variations in measurements of ambient stream water quality, respectively.

See the accompanying Open-File Report for a discussion of the characteristics of the BSP data and statistical methods for using these data to estimate laboratory measurement bias and variability and to assist in the interpretation of national network stream water-quality data.

Note that the following datafile extensions (i.e., ".DAT", ".FMT") are non-standard MIME types and your browser may request additional action.

• BSP_PARM.DAT lists the available constituents with their units of measure, chemical expression, and unique 5-digit parameter codes.
  See the BSP_PARM.FMT file for details of the file layout.

• BSP_METH.DAT lists the USGS laboratory analytical method codes and reporting limits that are applicable to these BSP data. The laboratory analytical methods corresponding to these codes were used for national network stream water-quality data for the years and constituents indicated.
  See the BSP_METH.FMT file for details of the file layout.

• METHODS.DAT includes definitions of the laboratory analytical method codes for the BSP data. This file also defines method codes used for other water-quality constituents appearing in the CD-ROM data bases.
  See the METHODS.FMT file for details of the file layout.

Estimates of laboratory measurement error and variability are organized in separate files by constituent group. Measurement error data from which the bias can be estimated appear in the file BIAS.ttt, and laboratory measurement variability data appear in the file VAR.ttt, where ttt is:

MJ1 for major dissolved ions,
MJ2 for major dissolved ions,
NUT for nutrients,
MT1 for dissolved trace metal parameters,
MT2 for dissolved trace metal parameters,
MT3 for dissolved trace metal parameters, and
MT4 for dissolved trace metal parameters.

• bias.mj1
  
• bias.mj2
  
• bias.mt1
  
• bias.mt2
  
• bias.mt3
  
• bias.mt4
  
• bias.nut
  

Within each laboratory measurement error file (BIAS.ttt), the records are sorted by the laboratory login date, the BSP sample mixture number, and a sequential sample number designating samples of the same mixture analyzed on identical days.

Measurement variability data are available in the following files (see the VAR.FMT file for details of the file layout):

• var.mj1
  
• var.mj2
  
• var.mt1
  
• var.mt2
  
• var.mt3
  
• var.mt4
  
• var.nut
  

Within each measurement variability file (VAR.ttt), the records are sorted by earliest and latest laboratory login date for the BSP sample mixture and the BSP unique sample mixture number.