Tim Grundl's Research

I am currently involved in multiple lines of inquiry. The first is a comprehensive look into the overall geochemistry of the deep sandstone aquifer in eastern Wisconsin and the upper Midwest in general. This aquifer is the pre-eminent source of groundwater within Wisconsin and Illinois. The resource is being over utilized and is coming under increasingly severe stress. Various geochemical conditions are limiting the usage of this aquifer including high radium. Many communities are over the EPA mandated limit on the amount radioactivity that can be supplied to their customers and the interest in this topic is high. The last of the Pleistocene ice advances injected a large pulse of fresh Pleistocene water into this aquifer and through the use of noble gas and stable isotope data we are in the process of unraveling the dynamics of this one-time event. Glacial-groundwater interplay is of great interest to glaciologists and hydrologists alike and has water supply implications as this water is “mined” for our drinking water supply.

Another aspect of this work is a study of the shallow aquifer in southeastern Wisconsin to ascertain what effects would occur if treated effluent, complete with a high chloride load and a variety of emerging contaminants is used to recharge the aquifer either directly in an effort to reduce the effects of overpumping or indirectly by the use of riverbank filtration. We are currently exploring several geochemical indicators to discriminate between recharge that contains treated effluent and recharge impacted by road salt. Varying halogen ratios, lithium, boron and boron isotopes are all promising candidates. This work will serve to constrain numerical groundwater models that be used to understand the hydrology of the shallow aquifer system.

A third line of inquiry is the development, in collaboration with other colleagues, of a suite of in-situ probes for the rapid, screening level detection of contamination in harbor sediments. Sediment borne contamination is the major source of contaminants to the surface waters of the United States and part of the reason that sediment remediation has not occurred very rapidly is the expense and large-scale disruption associated with remediation. Remediation efforts would be much more focused and inexpensive if a better means to initially characterize the extent of contamination was employed. Current techniques depend on expensive networks of discrete sampling sites that can be 100s to 1000s of meters apart. Our probes allow real-time identification of PAH and heavy metal contamination in harbor sediments for a fraction of the effort involved in the typical coring and subsequent lab analysis that is in use today. These probes are mounted on a cone penetrometer rod and induce contaminant fluorescence using laser or x-ray excitation (for PAHs and metals respectively).

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