Reference-Quality Water Sample Data: Notes on Acquisition, Record Keeping, and Evaluation.

Abstract

Generating reference-quality water sample data involves procedures learned over years of experience. Some simple-to-implement aspects of practice do, however, lead to improved reliability and documentation of water sample data. These include: • For water sample data verification of the collection depth and unambiguous association of that depth with a unique sample identifier, understanding the degree to which the water which issued from the sampling spigot matched the characteristics of the ambient water from the collection level, verification that all data values associated with a water sample are correctly matched to the water sample identifier, and determination if the values for each parameter are correct. • Data evaluation must begin at sea. This is usually the only time all involved personnel and all records are together. Also, it is possible then to correct repetitive problems before they can further degrade the data. • The care of the data analyst and access to complete records are in general more important than the specific scheme of data evaluation. • The analyst must determine if the appropriate standards were met by the bulk of the data. Emphasis should be placed on adherence to proven, documented methodology over agreement with historical data. Quality standards should be applied consistently. • The analyst determines which data values are suspect, partly by identifying outliers and assessing their severity and cause, or finding that the anomalies are likely genuine. Suspicion of a data problem based on a data value alone, without probable cause for an erroneous value, should normally not of itself be cause to demote the quality of a value. • Apparent problems should be corrected if possible. 1 • The analyst's report and a report of subsequent actions must be archived. These should be added to a data report which also contains ancillary information about the cruise, a summary of data acquisition and processing methodology, data quality information, and a complete list of contacts for further information regarding the cruise, methodology, and the data.