Water quality sampling procedures

Abstract

Sampling is the first operational stage in any water quality monitoring programme. No matter how good the analytical method is or how carefully the analysis is performed if the sampling is not carried out correctly then subsequent analytical results will not be representative of the water body sampled. Detailed water sampling requirements are specified in ISO 5667. A questionnaire found that no laboratory, which responded, is currently accredited or in the process of attaining accreditation to this standard. In general, the procedures and practices in environmental laboratories questioned fall significantly short of the requirements of ISO 5667, particularly in relation to the preservation of samples, the documentation of sampling training procedures and the maintenance of training records. Information received from the questionnaire indicated similar trends between Limerick County Council and other Local Authority (LA) laboratories. For example, LA laboratories generally do not preserve samples, very few analyse quality control field blanks or have considered obtaining accreditation specifically to ISO 5667. The trends in EPA laboratories are somewhat different from those in LA laboratories in that all of the laboratories use chain-of custody forms and most analyse quality control field blanks and preserve samples. The majority of EPA laboratories have considered obtaining accreditation specifically to ISO 5667, although none are in the process of doing so. Current water sampling procedures and practices employed at the environmental laboratory of Limerick County Council were used, as a case study, to determine the level of work required to achieve ISO 5667 accreditation. This study revealed that approximately 80% of the requirements of ISO 5667 could be implemented using existing facilities provided adequate resources are allocated e.g. the documentation and implementation of comprehensive sampling programmes and sampling procedures and the maintenance of detailed records. The implementation of the remainder of the requirements would however, require specific expertise, unlikely to be available within most laboratories For example, ISO requires that sampling locations should be assessed for stratification and degree of turbulence. This information could not be readily obtained using existing resources and therefore external consultants would have to be employed requiring a significant financial backing.