Monitoring techniques–Grab and passive sampling

Existing and emerging pollutants pose a significant threat to the health and viability of freshwater systems. Reliable monitoring is critical. This chapter compares passive and conventional grab sampling techniques for pollutants such as pharmaceuticals, pesticides, metals, nutrients, and emerging pollutants such as glyphosate and PFASs, highlighting the techniques’ relative advantages, disadvantages, and challenges. For example, spot grab sampling is not suitable for situations where pollutant concentrations are subject to fluctuation whereas passive sampling can provide a time-weighted pollutant concentration. The application of these sampling techniques to current water quality guidelines from different countries is described. Approaches such as non-target analysis and improved techniques such as the use of novel passive sampling sorbents are suggested to address the growing list of emerging freshwater pollutants. To enable wider use of passive samplers there needs to be a better theoretical understanding of how they operate and more calibration data, especially for emerging pollutants.