2007 Annual Report
Using chelator-buffered nutrient solutions which allow us to grow lettuce with highly controlled Cd and Zn levels, and normal levels of other nutrients, we grew several kg of lettuce with desired composition for test were grown and prepared for feeding. The lettuce with low Zn contains about 4 mg Cd/kg and 20 mg Zn/kg dry weight, while the high Zn lettuce contains about 4 mg Cd/kg and 480 mg Zn/kg dry weight. One more crop must be grown to have all needed lettuce ready for the feeding experiment.
Three cultivars of carrot, one cultivar of lettuce and four cultivars of Irish potatoes were grown on five orchard soils with a history of lead arsenate application. Root crops were peeled and both peel and peeled crop submitted for analysis. Harvested plants samples were freeze-dried and analyzed for arsenic and lead using microwave digestion using methods which avoided dust contamination of the tissue samples. As and Pb determined using ICP-OES and ICP-MS. Important findings were obtained in that the peeled carrot but not the peeled potato contained significantly increased Pb when grown on the high Pb orchard soils. It is now evident that Pb can be trapped within the xylem of carrots during growth; potato has only phloem connections and avoids significant internal Pb even on Pb contaminated soils. Peel of potato is contaminated when grown on such soils.
Tests were conducted to assess the effect of amendment of orchard soils with iron oxides and phosphate to immobilize soil Pb and As. The short and long term effects of iron and phosphate on the bioaccessiblity of As and Pb from orchard soils were determined. Addition of phosphate without Fe increased the mobility of soil As, but reduced bioaccessibility of soil Pb. Addition of both chemicals reduced mobility of both Pb and As. Two manuscripts were prepared.
Cooperated with durum wheat breeders in ND, MT, and AZ in analyzing genetic lines from replicated field plots to aid in selection of genetic materials for field testing in 2007. Data provided to cooperators in time to prepare seed for planting.
Began new cooperation in testing other crops grown on dryland as new crops, e.g., camelina; new crop grown in association with durum wheat to allow characterization of relative Cd accumulation compared to known crops.
In cooperation with breeders in MT, noted that irrigation with melt water substantially lowered durum grain Cd levels compared to standard dryland production methods. These results indicate that background levels of chloride in dryland is strongly increasing durum grain Cd to levels which exceed Codex wheat limits compared to levels below Codex limit when melt water irrigation occurred. Irrigation of durum wheat is not commonly conducted on northern great plains.
The role of crop nutritional properties, and of co-current crop Zn, in the bioavailability of crop Cd to humans is increasingly recognized as having been technically demonstrated. Acceptance of bioavailability variation in international Cd risk debate remains challenging.
Findings explain how carrot but not other root vegetables and most other crops attain Pb contamination when grown on historic orchard soils rich in Pb and As. These findings provide valuable information to vegetable crop growers, the Food and Drug Administration (FDA), and land developers on the use of these old orchards.
Codling, E.E., Dao, T.H. 2007. Effect of lime, phosphorus and iron on lead and arsenic solubility in lead-arsenate contaminated orchard soils. Communications in Soil Science and Plant Analysis. 38:903-919.
Khoshgoftarmanesh, A.H., Chaney, R.L. 2007. Preceding affects cadmium and zinc of wheat grown in saline soils of central Iran. Journal of Environmental Quality. 36:1132-1136.
Lucena, J.J., Chaney, R.L. 2006. Response of cucumber plants to low doses of different synthetic iron chelates in hydroponics. Journal of Plant Nutrition. 30:795-809.