The Groundwaters of Springwater and Tiny Townships
Chemical and Isotopic Analyses of Groundwaters in Springwater and Tiny Townships, Simcoe County, Ontario, Canada
- To understand the behaviour and fate of Pb and Sb in these groundwaters, as part of our broader goal to better understand the exogenic geochemical cycle of these two elements.
- To improve all of the necessary experimental procedures and analytical methods for sampling these waters and reliably measuring the concentrations of Pb and Sb at concentrations of ng/l and below.
- To establish the ‘baseline’, or ‘natural background’ concentrations of Pb, Sb, and other trace metals in these waters, and to document the extent of their natural variation.
- To use the data obtained from these groundwaters to provide a ‘reference level’ against which the corresponding data for bottled waters may be compared and critically evaluated.
- Using the isotopic composition of Pb, expressed by the ratios 206Pb/207Pb and 208Pb/206Pb, to understand the predominant natural sources of Pb to these waters today.
Status of water quality studies
- samples have been collected on numerous occasions since 2004
- sampling sites include not only the Parnell flow which is adjacent to Site 41, but also at eight additional artesian flows between Site 41 and extending south of Anten Mills, a distance of ca. 20 km
- between August of 2004 and September of 2006, for example, 73 samples were collected from eight artesian flows, and measured for 23 major and trace elements using ICP-MS in our clean labs
- at all sites, extremely low concentrations of trace elements were found
- reliable measurements of trace metals in these waters required extreme precautions to avoid contamination as the clean lab methods developed for polar snow and ice
- filtration was not employed, to minimize the risk of contamination
- the analytical methods employed were identical to those which we have used successfully for the determination of trace elements in polar snow and ice, and have been published in relevant journals
- to help make the data understandable, and to put the measured values into perspective for the general public, our groundwater data has been compared with the values which we have obtained from measurements of the same elements in ice cores from the Canadian Arctic (past 15,000 years of snow accumulation), in collaboration with the Geological Survey of Canada in Ottawa
Results obtained to date
- concentrations of most trace metals in these waters are within a factor of five of the corresponding values for the cleanest layers of ancient arctic ice (dating from ca. 4000 to 6000 years ago) ie. silver, Ag; bismuth, Bi; cadmium, Cd; copper, Cu; antimony, Sb; thallium, Tl
- the average concentrations of some metals (cobalt, Co; chromium, Cr; lead, Pb; vanadium, V) are effectively identical to the average concentrations in the cleanest layers of ancient arctic ice
- rather remarkably, two samples from 2005 and three from 2006 yielded lead (Pb) concentrations below one part per trillion which is well below the lowest levels of Pb in cleanest layers of arctic ice (ice from 4000 to 6000 years ago averages five parts per trillion Pb)
- in fact, the concentrations of trace metals in many of the groundwater samples, are comparable to published values for deionised water
- for the majority of these parameters, this is the first time their concentrations have been reliably determined in these waters
Note that more recent layers of arctic ice contain elevated concentrations of trace metals due to global atmospheric contamination. Also, older layers of ice contain elevated concentrations of trace metals due to the dusty conditions which were characteristic of the post-glacial climate. For these reasons, we have compared our groundwater data to the cleanest layers of ancient arctic ice. In contrast, the average Pb concentration in the groundwaters of Springwater and Tiny Townships is approximately fifteen times less than the average Pb concentration in the ice samples from ca. 4,000 to 16,000 years ago.
A summary of our data for selected major and trace elements (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Ge, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Sc, Si, Sr, Te, Th, Ti, Tl, U, V, Zn) in the groundwaters from two of these artesian flows (including the Parnell flow adjacent to Site 41), will be published in the Journal of Environmental Monitoring, published by the Royal Society of Chemistry 12: 208-217. View online.
Comparison with snow
The study published in JEM in January of 2010 shows that potentially toxic, chalcophile elements are highly enriched in snow, relative to their natural abundance in crustal rocks, with EF values (calculated using Sc) in the range 107 to 1081 for Ag, As, Bi, Cd, Cu, Mo, Pb, Sb, Te, and Zn. Relative to M/Sc ratios in snow, however, water samples collected from the two artesian flows in the same area are significantly depleted in Ag, Al, Be, Bi, Cd, Cr, Cu, Ni, Pb, Sb, Tl, V, and Zn at both sites, a testimony to the remarkable filtration ability of soils.
Comparison with bottled waters
Our studies of these pristine groundwaters enabled us to show that bottled waters are contaminated with antimony (Sb) leaching from polyethylene terephthalate (PET) containers. Our most recent findings are that the published values for lead (Pb) in bottled waters from Canada are too high by two to three orders of magnitude. Moreover, we have also found that bottled waters in glass are contaminated with Pb leaching from the containers. Again, the pristine groundwaters have been most helpful with our efforts to put trace element data for bottled waters into a geochemical perspective.
Dating of the groundwaters
Measurements of natural radioactivity (tritium) in samples from the Parnell flow (which is adjacent to Site 41) are not significantly different from rainwater values. According to Prof. Aeschbach-Hertig (Institute of Environmental Physics, University of Heidelberg) who kindly made these measurements, these findings mean that the waters emanating from the Parnell flow are very young (ie probably < 30 years). These results indicate that the residence time of the water between recharge and discharge is very low, and suggests that the groundwaters are migrating rapidly through the aquifer.
Considering the tremendous inputs of atmospheric, anthropogenic Pb to the soils of southern Ontario during the 20th century (cumulative inputs of 1 to 2 g/m2 according to our measurements of peat cores from three bogs), the extremely low Pb concentrations in the groundwaters combined with their young age suggests that there must exist efficient, natural Pb removal processes, either in the soils of the Simcoe Uplands, or at the interface with the Elmvale Clay Plain. Detailed studies of these removal processes are warranted and are now in the planning stages.
Isotopic composition of Pb
Although we can reliably measure Pb isotope ratios even in the cleanest layers of ancient arctic ice, the Pb concentrations in these pristine groundwaters are so low that they present a number of new analytical challenges. We are now in the process of planning new studies intended to overcome these problems. One of the first steps taken thus far has been the construction and installation of two dedicated groundwater research wells, one using surgical stainless steel (PIC), and one using acid-cleaned high density polyethylene (HDPE) tubes (PIC).