Aquifer transport of Th, U, Ra, and Rn in solution and colloids. 1997 annual progress report

'Preparations have been made to collect groundwater samples from the unconfined Pleistocene aquifer on Long Island, N.Y. from wells at Brookhaven National Lab.. Dr. Jan Naidu of the Brookhaven Safety and Environmental Protection Division has been intimately involved with the groundwater monitoring program at the site for many years, and has provided us with detailed information regarding site hydrogeology, groundwater chemistry, and monitor well locations and construction. In consultation with Dr. Naidu, a series of wells have been chosen for sampling that extend over a distance of {approximately}5000 feet along a single flow path, with estimated water ages of up to {approximately}20 years. Since the recharge area for these waters has been the source of low levels of tritium (and possibly {sup 90}Sr) contamination, there has been considerable interest in the hydrogeology and chemistry of the area, and all information gathered at the site will be provided to BNL staff. Groundwater sampling is planned for the autumn of 1997. At this time, aquifer materials will also be obtained from the drill core repository of the USGS office in Long Island, where Mr. Henry Ku has indicated that material will be available for the use. As a complement to the studies of U and Th series nuclides, the sampling plan is being extended to include analysis of He isotopes. Concentrations of {sup 4}He are expected to largely reflect the time-integrated recoil production by decay of the U and Th series nuclides, without losses due to adsorption or decay, and will be compared to {sup 222}Rn concentrations, which provide recoil rates over short time periods. The concentrations of {sup 3}He due to decay of contaminant {sup 3}H in these waters will also be measured, and a comparison between the measured concentrations and that produced in the waters since the time of recharge will provide an indication of whether gas losses have occurred. Arrangements have been made to collaborate in this phase of the research with Dr. David Hilton of Scripps Institute of Oceanography, who has extensive experience in measuring He isotopes in hydrological systems. Dr. Hilton has agreed to provide the necessary field equipment for sampling and will conduct the laboratory analyses of He isotope concentrations.