Oysters and sediment have been collected from most major US Gulf of Mexico bays and estuaries each year since 1986. Selected samples of oyster soft tissue, shell and sediments were analyzed for Cd, Cr, Cu, Fe, Mn, Pb, and Zn for this study. Concentrations varied considerably from place to place but ratios of metals remained relatively constant. Cu and Zn are greatly enriched in oyster tissues, which is related to their physiological function. Cd is enriched in oyster shell because of the easy substitution between Cd and Ca. The concentrations of Pb and Cr in oysters are significantly lower than that in sediment, suggesting a good discrimination against these metals by oysters. Metal variations are a result of both nature and human activity.
So I ran a ton of 12 x 12 granite samples up to Boulder Colorado to a man that had an XRF gun, looks like a hand held radar gun, spits out a list of heavy metals present in what you point it at. Yikes, lead, arsenic, cadmium, chromium, lots of uranium, and dozens more heavy metals. Everything except beryllium. Finding beryllium was the Holy Grail but my budget was limited to a hundred scans so we didn't find that one.
Amounts varied of course from small trace amounts to ore quality, as much as 1% of some heavy metals, much more for common metals like lead.
n Washington state, the Port of Seattle first began using crushed oyster shells — an abundant resource, given the oyster-rich waters of nearby Puget Sound — in 2005 as an additive to storm water bioretention swales at SeaTac airport. The goal was to add hardness to the runoff to reduce toxicity before the water ended up, inevitably, in Puget Sound once again. Calcium from the shells served to increase the mineral levels, but Port environmental managers also found that the runoff from outflows so treated also had copper and zinc levels reduced by about 50%.
On the first anniversary of the spill, the 150-year-old CAS produced a short movie highlighting the work of three of its researchers, including Roopnarine, where the narrator explained that like tree-rings, heavy metals could be detected and read in oyster shells.
...A top federal government scientist, not involved in the research, responded by saying there are now “delicate steps” that need to be taken to determine if the heavy metals in oyster shells are “dangerous or harmless” to those who might ingest them.
Chris Kott wrote:Personally, I think that if feeding chickens back their own shells isn't sufficient, I would increase the quantities of plant-based calcium they're being provided.