{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:44:11Z","timestamp":1785437051174,"version":"3.56.0"},"reference-count":47,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,14]],"date-time":"2026-06-14T00:00:00Z","timestamp":1781395200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100009886","name":"Regione Puglia","doi-asserted-by":"crossref","award":["RSU\/DEL\/2016\/00009"],"award-info":[{"award-number":["RSU\/DEL\/2016\/00009"]}],"id":[{"id":"10.13039\/501100009886","id-type":"DOI","asserted-by":"crossref"}]},{"award":["RSU\/DEL\/2016\/00009"],"award-info":[{"award-number":["RSU\/DEL\/2016\/00009"]}],"id":[{"id":"https:\/\/ror.org\/039k11f95","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This study presents the development and field testing of a Pressurized Driving-Down Air Multilevel Sampler (PDA-MLS), an integrated groundwater sampling device designed for depth-discrete sampling in boreholes affected by floating non-aqueous phase liquids (NAPLs). Conventional sampling methods\u2014such as low-flow pumps, bailers, and packer-isolated systems\u2014often fail under these conditions due to limited accessibility, cross-contamination, or disturbance of the water column. The proposed system addresses these limitations through a controlled pressurized-gas actuation mechanism that transfers groundwater from multiple PTFE-membrane chambers installed at discrete depths. This configuration enables low-disturbance sampling below floating contaminant layers. The use of chemically inert materials (stainless steel and PTFE) minimizes sampling artifacts and ensures compatibility with volatile organic compound (VOC) analyses. A simplified hydraulic conceptual framework describing inflow, outflow, and pressure-driven displacement was developed to support purge-duration estimation and operational parameter definition. The device was tested in a 90 m deep fractured limestone aquifer contaminated by tetrachloroethylene (PCE), where floating hydrocarbons limited the applicability of conventional sampling techniques. Field testing showed stable discharge conditions (~145\u2013160 mL\/min), repeatable sampling cycles, and successful collection of depth-discrete groundwater samples under the investigated site conditions. No evidence of sampler-related hydrocarbon entrainment was observed in the collected samples within the analytical detection limits of the adopted laboratory methods. To the authors\u2019 knowledge, the PDA-MLS represents one of the few groundwater sampling systems specifically designed to combine low-disturbance multilevel sampling with operation in wells affected by floating NAPL. These features make it a promising tool for environmental monitoring, high-resolution characterization of fractured aquifers, and long-term assessment of contaminated sites.<\/jats:p>","DOI":"10.3390\/s26123788","type":"journal-article","created":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T05:59:47Z","timestamp":1781503187000},"page":"3788","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Design and Field Assessment of a Pressurized Driving-Down Air Multilevel Sampler for Depth-Discrete Groundwater Monitoring in NAPL Impacted Wells"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5101-9826","authenticated-orcid":false,"given":"Giuseppe","family":"Passarella","sequence":"first","affiliation":[{"name":"Water Research Institute of the National Research Council of Italy, 70132 Bari, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3891-0977","authenticated-orcid":false,"given":"Rita","family":"Masciale","sequence":"additional","affiliation":[{"name":"Water Research Institute of the National Research Council of Italy, 70132 Bari, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Antonio","family":"Di Fazio","sequence":"additional","affiliation":[{"name":"Water Resources Commission, Regional Order of Geologists of Puglia, 70125 Bari, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Costantino","family":"Masciopinto","sequence":"additional","affiliation":[{"name":"Water Research Institute of the National Research Council of Italy, 70132 Bari, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"649","DOI":"10.1111\/j.1745-6584.2010.00753.x","article-title":"Lessons Learned from 25 Years of Research at the MADE Site","volume":"49","author":"Zheng","year":"2011","journal-title":"Groundwater"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1111\/j.1745-6592.2011.01365.x","article-title":"Field Investigation of Vapor-Phase-Based Groundwater Monitoring","volume":"32","author":"Adamson","year":"2012","journal-title":"Groundw. 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