5.1. Data Quality Objectives. The data quality objectives (DQOs) reflect the goals and scope of the project outlined above. Precision will be judged by standard deviations from the arithmetic mean of replicate (n = 3 - 5) determinations. Precision will be assessed at three levels corresponding to (i) replicate analyses of a single sample, (ii) analysis of replicate sample preparations, and (iii) preparations of replicate experiments. Adequate relative standard deviations at these three levels will be -+1%, -+5%, and -+10%, respectively. Accuracy of individual analytical measurements will be determined by calibration to standards. The accuracy of overall experimental results will be assessed on their scientific reasonableness and their consistency with other results from this and other laboratories.
5.2. Representativeness. Representativeness is an important data quality issue for this scope of work. Field sampling locations will be selected on the basis of a careful review of the design and performance characteristics of the slough reaches so that samples will optimally reflect the true behavior of the system. Intercomparison of the results of sampling at several points within the system will assist in assuring that results are representative.
5.3. Performance and Procedures. All experimental and analytical work in the laboratory will be performed by either a graduate research assistant, the principal investigator, or an experienced technician in a laboratory explicitly designed for advanced water quality studies. In all cases standard operating procedures (SOPs) have been or will be developed and documented in written records. Deviations from SOPs will be minimized and recorded when they occur. Limits of detection and quantitation will be determined for all analytes. Instrumentation will be carefully calibrated and rechecked routinely as part of SOPs. Field and laboratory blanks and controls will be prepared and analyzed in all stages.
5.4. Record Keeping. Laboratory notebooks will be maintained by the graduate research assistant and the technician and updated each working day. All entries will be made according to accepted standards for laboratory record keeping (e.g., full, permanent documentation and dating of all procedures). Weekly, the principal investigator will inspect and sign the notebooks. Notebooks will be retained in the laboratory and will be subject to the confidentiality restrictions outlined below.
5.5. Data Analysis. Data analysis will be performed using the most reliable techniques. For example regression analysis will be performed with attention to the many common pitfalls. In general, weighted least squares regression will be performed on untransformed data whenever possible. Error propagation will be calculated by rigorous formulations to obtain unbiased estimates of overall experimental uncertainty.