Wayne brings up a good point. The bioavailability of toxic compounds, including metals is affected by many things among which pH can be one. In fact, the issue of TMDLs in the clean water act is based on problem that each stream has its own water chemistry and organic load. This causes us to require specific total maximum daily loads (TMDLs) of each compound for each stream (or portions thereof). TMDLs were supposed to be completed for surface waters in most states a long time ago, unfortunately the process is not done everywhere!
Malcolm On Fri, Apr 15, 2011 at 9:03 PM, Wayne Tyson <[email protected]> wrote: > Ecolog: > > This rings a vague bell for me too. There was some work done in the British > Isles (Scotland) on very crisp ecotones across pH differences using one > grass species. Also, I seem to recall that the Dutch were using willows that > were supposed to be hyperaccumulators and they were burning them for fuel, > then disposing of (or "mining") the heavy-metal "laden" ash. There is, of > course, considerable literature on "phytoprospecting." I, too, would like to > be brought up to date in this area, and educated on the particulars. For > example, I would like to know just how accumulation or "rejection" > functions, and what processes are involved. For example, how does pH affect > the rate and amount of absorption? What other chemical and physiological > processes are involved? Why are some heavy metals (chromium, selenium, > arsenic, etc.) apparently readily absorbed (by the Chenopodiaceae, for > example--and the mustard family), and lead apparently not? Is it as simple > as semipermeable membranes, whether or not they are soluble and under what > conditions? Is something going on in the rhizosphere that evades some > analytical procedures? > > WT > > > ----- Original Message ----- From: "Martin Meiss" <[email protected]> > To: <[email protected]> > Sent: Friday, April 15, 2011 9:04 AM > Subject: Re: [ECOLOG-L] where do edible plants retain lead and other > contaminants? > > > A long time ago, when I was learning about plant ecotypes, I heard of > research on the adaptation of plants to high lead levels found in piles of > mine tailings. If I remember correctly, local races of plants were forming > that were able to adapt to toxic soils. This raises these questions: if > plants ARE NOT taking up the heavy metals, what is the mode of toxicity? > (Are ions in the soil blocking the uptake of needed substances?) What is > the mechanism of resistance that was evolving? If it involved the blocking > of uptake of lead and other metals, that implies that other, non-adapted > plants DO take them up. > Can any one comment on this aspect of the issue? > > Martin M. Meiss > > 2011/4/15 Judy Che-Castaldo <[email protected]> > >> Hi Ben, >> In general you are unlikely to find lead in the shoots of plants, because >> it >> is not very soluble and most plants exclude heavy metals. The edible >> plants >> that may have Pb would likely be leafy vegetables (grown close to the >> ground) and root vegetables (as mentioned earlier) because of the >> associated >> soil particles containing Pb. >> >> There are some plants that uptake heavy metals into their shoots but few >> for >> Pb, and even those may only do so under rare circumstances (such as >> phosphorous deficiency - Chaney 2007 J. Environ. Qual. 36:1429–1443). If >> you are interested in other contaminants you can look into the metal >> hyperaccumulation literature. Many of these plants are in the mustard >> family but probably are not normally eaten. >> >> best, >> Judy >> >> >> Judy Che-Castaldo >> BEES program, Biology Dept. >> University of Maryland >> (301)351-8290 >> http://www.life.umd.edu/grad/BEES/students/che.html >> > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1204 / Virus Database: 1435/3511 - Release Date: 03/16/11 > Internal Virus Database is out of date. > -- Malcolm L. McCallum Managing Editor, Herpetological Conservation and Biology "Peer pressure is designed to contain anyone with a sense of drive" - Allan Nation 1880's: "There's lots of good fish in the sea" W.S. Gilbert 1990's: Many fish stocks depleted due to overfishing, habitat loss, and pollution. 2000: Marine reserves, ecosystem restoration, and pollution reduction MAY help restore populations. 2022: Soylent Green is People! Confidentiality Notice: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
