The advent of widespread, long-term environmental issues such as atmospheric contaminants requires reassessment of monitoring techniques and procedures to improve field and laboratory quality assurance. We are studying mineral nutrient budgets in mature northern watershed and lake ecosystems which have widely varying inputs of atmospheric contaminants. These sites have been little studied, so consistency and appropriateness of sampling procedure and analysis is critical. We have developed a series of sampling and data quality objectives and procedures which allows us to estimate the accuracy of field methods and sample integrity and to determine analytical bias and precision in the laboratory. The system employs a series of internal and external audits and relies heavily on existing protocols developed by national monitoring and research organizations.