Towards field‑deployable sediment porewater extraction: A comparative study for environmental trace metal monitoring

Sediment porewater is a key medium for controlling contaminant mobility and bioavailability in aquatic systems. Yet, methodologies to extract porewater from sediment samples differ substantially in their efficiency, reliability, and suitability for field deployment. The present study compared four porewater extraction techniques: Laboratory centrifugation, portable centrifugation, Rhizon samplers, and a novel AeroPress-based extraction device, utilizing silty and sandy sediments from two boreal lakes. Extraction efficiency, sample contamination risks, and operational feasibility for field use were evaluated. Laboratory and portable centrifugation produced the highest porewater recoveries, generally exceeding 25-50% extraction efficiency, whereas AeroPress and Rhizon samplers yielded lower recoveries. The metal concentrations in the extracted pore water samples varied between the extraction methods and sediment types, with Rhizon samplers and AeroPress yielding higher concentrations of specific trace metals in some cases due to leaching of the metals from the components of the extraction devices, causing sample contamination. No consistent relationship was observed between extraction efficiency and metal concentrations in the extracted water samples. However, Pb showed a strong positive correlation with extraction efficiency, suggesting preferential recovery with higher-volume methods. Portable centrifugation provided the most practical balance between efficiency and field applicability based on both the volume of porewater that can be extracted and ease of use, while AeroPress offers a promising low-energy alternative in power-limited settings. These findings highlight that the porewater extraction method, the filter material, and sediment type affect the metal concentrations in the extracted porewater samples and should be carefully considered when applied for environmental monitoring.