During the collection and testing of water quality samples, scientists continually check for errors through the use of internal quality control samples such as standards, blanks, duplicates and spikes. The Chesapeake Bay Program also requires the analysis of split samples, blind audit samples and USGS reference samples to permit an independent evaluation of laboratory proficiency.
The Chesapeake Bay Coordinated Split Sample Program (CSSP) is an interlaboratory testing program that involves the distribution of identical surface water samples to participating state, federal and academic monitoring agencies. The samples are processed according to standard protocols and the results evaluated quarterly to ensure that the monitoring programs are producing comparable data. Comparable data are important to Chesapeake Bay scientists because data are often combined from a variety of sources and time periods to conduct Bay-wide assessments and modeling applications.
The CSSP is comprised of a mainstem component and a tributary component to represent saline and fresh water matrices. Agencies and their laboratories participate in one or both components according to their routine sample type. The results of each split sample study are reviewed by Bay Program quality assurance staff and discussed at Data Integrity Workgroup meetings. When results are inconsistent among agencies, the workgroup investigates possible causes and recommends corrective actions.
The Chesapeake Bay Program Blind Audit Program provides laboratory proficiency testing samples for dissolved and particulate nutrients and chlorophyll at the relatively low concentrations commonly found in estuarine systems. Prepared concentrates of dissolved and particulate substances, whose concentrations are unknown to the analysts, are distributed twice a year to approximately 14 regional laboratories. The results provide a measure of laboratory accuracy as the samples are fully prepared prior to distribution and the errors associated with field filtering and subsampling are minimized. The Nutrient Analytical Services Laboratory at the Chesapeake Biological Laboratory is the sole provider of the Blind Audit samples. Blind audit results can be donloaded on the University of Maryland Center for Environmental Science's website.
Chesapeake Bay Program laboratories also participate in the USGS Standard Reference Sample (SRS) Program to establish their accuracy and comparability to other laboratories at a national level. The low-level and/or regular-level nutrient SRS samples are analyzed twice a year. Results are submitted online through the SRS project website. USGS performs statistical analysis and releases them on the website by lab number. Bay Program staff downloads the data and graphs results from Chesapeake Bay laboratories for review at Data Integrity Workgoup meetings. Graphs from 2002-2003 are also available.