Hi Zeke and All,
This may be a moot point since most people will not be growing oil seeds or grazing animals on heavy metal contaminated land. Heavy metals tend to be respiratory poisons. By this I mean cellular respiration. At high enough concentrations, lead, mercury, zinc and cadmium interfere with a cell's ability to make energy. Of course their effect is much broader than that but this alone is enough to kill a cell, a tissue, an organ etc. These heavy metals take the place of or interfere with sodium, potassium, iron or magnesium within the cell. When they do so things like proteins bend or distort and become non-functional. Think of a heavy metal like lead interfering with iron in a hemoglobin molecule or magnesium in a chlorophyll molecule. In one case oxygen doesn't transfer in the other sunlight is no longer useful to make plant energy.
Bioaccumlation can occur but since we're talking about plants it is limited. Lands that are severely contaminated with heavy metals tend to be bare and lifeless. Lower levels of contamination are tolerated depending on the amount of organic material in the soil. The humic acids, due to their complex stuctures, bind metals and sequester them. That's why swamps with lots of organic matter tend to have high concentrations of metals as metal sulfides. In plants I would think that heavy metals would attach to proteins first, then vitamines, then conplex benzene ring compounds, then triple and double bonded fats, greases and oils. So something like linseed oil with lots of double bonds might have some contamination with heavy metals while single bonded materials would have less. I don't think this is a big issue unless you are reclaiming a Superfund site with oilseeds and then use the oilseeds for biodiesel. It's a good question though. I don't currently have an AA analyzer but I know someone with an ion chromatograph. Perhaps I can pursuade them to run some of my canola but it may gunk up their system
Tom Irwin
From: Zeke Yewdall [mailto:[EMAIL PROTECTED]To: Biofuel@sustainablelists.orgSent: Mon, 13 Feb 2006 13:10:09 -0300Subject: [Biofuel] Heavy metals in biodiesel via bioremediation?Reading a bit about the leaded gasoline and lead and mercurycontamination from various sources in other threads this morning leadto me thinking about heavy metal emissions from biodiesel. Theoretically, we know exactly what's in there (just veggie oil,transformed with methanol and lye, right?). But having read a bitabout bioremediation as well, I wondered if anyone has ever tested howmuch heavy metals could be accumulated in the oil of rapeseed andmustardseed crops grown for biodiesel on contaminated soil, andre-emitted into the air? I can't remember the source now, but Iremember a site in china where they grew mustard plants oncontaminated ground, burned the plants, and found that the ashescounted as high grade silver ore... In bioremediation, exactly whatparts of the plants accumulate the most heavy metals -- if they'relike animals, the fats (oil feedstock for biodiesel) would hold alotof them right?Just some musings on my part now, but I'd be interested if anyone hasstudies which address this.Zeke___Biofuel mailing listBiofuel@sustainablelists.orghttp://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.orgBiofuel at Journey to Forever:http://journeytoforever.org/biofuel.htmlSearch the combined Biofuel and Biofuels-biz list archives (50,000 messages):http://www.mail-archive.com/biofuel@sustainablelists.org/
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