GB/T 12999-1991 is a technical regulation for the preservation and management of samples in water quality sampling. The collected water samples need to be properly preserved and managed to ensure the accuracy of the test results. The standard specifies the preservation methods corresponding to water samples with different water quality indicators, such as refrigeration, adding protective agents, etc. Detailed description of the storage time limit to prevent sample deterioration and composition change. Also standardizes the sample transportation and handover process to ensure the stability of the sample state from collection to analysis. Provide key technical support for water quality monitoring work, ensure the mass of water samples, and improve the Reliability of water quality testing data.