Niel Plummer, since the award of his PhD degree at Northwestern in 1972, has been a geochemical innovator and new-trail blazer par excellence. His doctoral dissertation, the several publications resulting from it, and subsequent work have defined a new standard for studying mineral-water reactions in the laboratory. Plummer's study of the reaction rates and dissolution products of the ubiquitously present mineral calcite in water was a seminal study, the results of which are cited to this day. After joining the US Geological Survey in 1974, Plummer's activities became focused on the important sets of geochemical processes that control the composition of ground waters flowing through the Earth's subsurface. Here, he developed a novel computational model of mineral-water geochemical interactions, based on chemical thermodynamic and hydrological data. The purpose of this very successful model was to estimate how ground water composition may change in the course of its flow through aquifers where the rock mineralogy changes. Numerous applications of this basic model and its later variants were made in the studies of ground waters by Niel Plummer and collaborators in many parts of North America, including such geologically diverse setting as the ground waters in New Mexico, Virginia, California, Wisconsin, Idaho, Florida, and Pennsylvania. These studies opened a new page in our understanding of evolution of ground-water systems and their contamination by human activities.
Since the mid-1990s, Niel Plummer's work took a different term. A number of human-made gaseous compounds have been identified in the atmosphere and shown to act as greenhouse gases, potentially affecting the climate. These are mostly several chlorofluorocarbon compounds (CFCs) and sulfur hexafluoride. Additionally, a wide range of Volatile Organic Compounds (VOCs), released to the atmosphere by various industrial activities, are known to affect the ozone cycle in the lower atmosphere. Plummer's and his collaborators' work has been focused in the last 10 to 15 years on the identification of these rare gaseous compounds in ground waters in order to measure their ages and flow rates. The work is a combination of field sampling of ground waters, laboratory analyses using cutting-edge ultra-sensitive techniques, and theoretical modeling and interpretation. These are completely novel techniques making a new chapter in the study of ground waters that is being written to a great extent by Niel Plummer and his collaborators.
During his work at the US Geological Survey, Niel Plummer's contributions have been recognized by three awards of the US Department of Interior and two awards by external organizations: the O. E. Meinzer Award of the Geological Society of America, Hydrogeology Division, and Special Recognition Award of the Association of Ground Water Scientists and Engineers, listed below.
- June 19, 2001: Citation for Distinguished Contributions to Employee Development. US Geological Survey Water-Science Program Award "for sustained, outstanding leadership and support for continuous learning activities in the Water Resources Division". Distinguished Service Award, US Department of Interior, Washington D.C.
- December 9, 1996: "In recognition of exceptional contributions to the US Geological Survey in the field of ground-water chemistry". O.E. Meinzer Award, Hydrogeology Division, Geological Society of America.
- October 26, 1993: Awarded GSA Annual Meeting, Boston, MA, for work on the Madison aquifer and chlorofluorocarbon dating of ground water, Special Recognition Award.
- 1990: Association of Ground Water Scientists and Engineers, NWWA, for contributions to the field of chemical hydrogeology and fundamental understanding of the chemical evolution of natural waters.
- February 6, 1987: Meritorious Service Award, US Department of Interior, Washington D.C., "in recognition of outstanding contributions to the Geological Survey in the field of chemical hydrogeology and fundamental understanding of the chemical evolution of natural waters".