Using hydro-geochemistry and isotopes to trace groundwater flow from Little Forest Burial Ground and surrounding landfills
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Date
2012-10-16
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Nuclear Science and Technology Organisation
Abstract
Multiple tracer-element and isotope approaches were used to study groundwater
near a legacy low-level radioactive waste burial site surrounded by municipal and
industrial waste sites. The interaction of rainfall, with its marine-derived major ion
ratios, and waste from the sites is apparent, however, clay-rich soils and shale at the
site tend to retain many contaminants via ion exchange and other processes. High
permeability of the disposal trenches provides a pathway for groundwater recharge,
with discontinuous perched groundwater lenses found in their vicinity.
Within the trenches, the degradation of organic matter results in localised
methanogenesis, as suggested by enriched δ2H and δ13CDIC in adjacent subsurface
water. Movement of contaminants from the waste sites is indicated by Na+, Brˉ
and Iˉ concentrations, variations in 87Sr/86Sr, enriched δ13CDIC and evolution of
δ34S of dissolved sulfate in perched water bodies above the shale. There is clear
evidence of a tritium plume from the LFBG trenches, although the adjacent landfills
provide an additional tritium source. Waste burial records show that over 1000
kg of Be (mostly BeO) were disposed in the LFBG trenches. However, beryllium
concentrations in groundwaters near the trenches are quite low, and appear more
likely to be controlled by the host lithologies and the other sources of contamination
in the vicinity, rather than by leaching of Be from the LFBG waste. Past removal
of the shale layer in an adjacent site, Harrington’s Quarry, has led to the mixing of
municipal waste leachates into the underlying groundwater system as suggested
by high TDS, Cl−/Br− ratios, Be, and 3H found in deeper wells. The multiple tracer
approach addresses the complexities of transport at the site and differentiates
various municipal, industrial, and radioactive waste sources
Description
Keywords
Geochemistry, Ground water, Ground disposal, Radioactive wastes, Soils, Groundwater recharge, Tritium, Water, Radionuclide migration
Citation
Cendón, D. I., Hughes, C. E., Harrison, J. J., Hankin, S. I., Johansen, M. P., Payne, T. E., Wong, H., Rowling, B., Vine, M., Wilsher, K., Guinea, A., & Thiruvoth, S. 2012. Using hydro-geochemistry and isotopes to trace groundwater flow from Little Forest Burial Ground and surrounding landfills. Paper presented to the 12th South Pacific Environmental Radioactivity Association Conference (SPERA 2012), Tuesday 16 October – Friday 19 October 2012 Sydney, Australia. Lucas Heights, NSW: Australian Nuclear Science and Technology Organisation, (pp. 56).