Abstracts

THURSDAY PLENARY SESSION
40 Years of Contaminant Hydrogeology
John A. Cherry
Distinguished Emeritus Professor, University of Waterloo,
Waterloo, Ontario, Canada
Forty years have passed since the earth-science sub-discipline
of ‘contaminant hydrogeology’ began to use this designation.
The term “Contaminant hydrogeology” was introduced into the
literature in an overview article published in Geoscience Canada 1 .
Part 2 of this article on the relevant chemical processes was not
completed until much later 2 .
This presentation examines what was known and not known when
this term was introduced and how our thinking has evolved with
some confusion and muddled thinking along the way, the path to
understanding of dispersion being a good example. It also examines the
current state of understanding; some aspects of hydrogeologic science
have matured while others are still in early stages. The initial article
focused on the physical processes in contaminant transport and fate was
based on the sparse groundwater contamination literature up to that time,
which concerned field studies of radionuclides from experimental reactor
accidents in the 1950’s, leachate from municipal landfills, sewage from
septic systems, petroleum hydrocarbons and the early problems caused by
the mobile versions of detergents.
Groundwater contamination by chlorinated solvents and the importance
of DNAPLS for groundwater contamination was unknown until the early
1980’s. The concept of contaminant plumes in groundwater was established
by the mid-1960’s but the belief was widely held until the early 1980’s that
the substantial groundwater contamination would remain minimal due to
the robust assimilation capacity of the subsurface environment. This would
have been correct if it were not for the widespread releases of many types of
halogenated organic chemicals such as chlorinated solvents. These began
entering groundwater in the 1950’s only to be discovered decades later. The
warning signs of the potential for mobile recalcitrant organic chemicals
of common use to cause substantial groundwater contamination occurred
in the early 1960’s when detergents from septic systems were commonly
found in shallow domestic wells in suburbs but this problem subsided with
a change in the detergent formulation in 1963. The larger significance of
this evidence concerning anthropogenic organic chemical in groundwater
went unrecognized.
IAH-CNC 2015 WATERLOO CONFERENCE
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