In Memoriam: Sjoerd E.A.T.M. van der Zee

Sjoerd van der Zee (1955-2022) passed away at the age of 67 on 24 June 2022. He started his research career investigating reactive transport in heterogeneous soil systems. worked academic positions for 35 years, since 1998 as a Professor Soil and Groundwater Pollution, later Ecohydrology Department Environmental Sciences Wageningen University, The Netherlands. has been Associate Editor Vadose Zone Journal 2017. made invaluable contributions to over years author, reviewer, associate editor. grew up Heerlen, Netherlands, 1974, he studies Agricultural University. received BSc (1978) MSc (1981) Physics Chemistry. In 1978, did an internship Engineering Technion, Israel Institute Technology, Haifa (Israel). For research, spent 6 months USDA Sedimentation Laboratory Oxford, Mississippi (USA) 1979. From 1981 1984, Physical Chemical Mechanics Delft returned PhD where doctorate (cum laude) 1988. While earlier work focused groundwater contamination, became active broad field ecohydrology. had many sabbatical visits abroad, including Swiss Federal Technology (EPFL) Lausanne Switzerland, Norwegian University Life (NMBU) Norway, Monash Australia. Likewise, hosted scientists visiting group sabbatical. During also presided Dutch Science Association (2002–2005) Boussinesq Center Hydrology (2005–2008), was chair member scientific advisory board UFZ (Environment Research Center) Germany (2005–2013), editorial several journals such Journal, Transport Porous Media, European Science. outstanding area contamination. His early flow water solutes porous media soils. rare ability combine chemical physical concepts principles modeling subsurface solute transport. pioneer developing analytical models that combined reaction kinetics with Later career, broadened ecohydrology, applying larger-scale hydrological geochemical problems. There, studied surface runoff overland chemicals from networks. supervised more than 30 students produced 350 publications, which 220 were international journals. Besides skillfulness conceptualizing pathways into mathematical, physical, descriptions, gifted painter sang choir led by wife Gemma. known subtle humor took pleasure making funny project model acronyms. With we have lost great colleague, collaborator, fellow scientist, mentor, friend. We will forever remember be thankful all contributions.