Search

Commercial forms of beta alumina have been examined using transmission electron microscopy. Measurements of the stacking fault energy on the basal plane have been made from the separation of partial dislocations and the equilibrium separation of partials at dislocation nodes, and estimated as 0.6 to 1.65×10-3 Jm-2. The structure of two- and three-block beta-alumina has been discussed and their relationship and transformation examined. It has been shown that transformation from two- to three-block beta-alumina cannot be accomplished by a simple shear. Structures generated by the passage of partial dislocations on the glide plane are discussed, and simple twining on the basal plane is examined and shown to be possible in the three-block, but not in the two-block material.

The effects of selected environmental control strategies on human dietary and respiratory exposure to environmental cadmium (Cd) have been simulated. For each control strategy, mean Cd dietary and respiratory exposures are presented for a twenty-year simulation period.

Several species (Andropogon scopanus, Shus radicans, Rudbeckia hirta, Anemone cylindrica, Monarda fistulosa, Poa pratensis, and Liatris spicata) native to northwestern Indiana were grown from seed in the greenhouse for 6 weeks. An uncontaminated sandy soil was utilized as the substrate with four levels of soil‐added Cd. The concentrations added ranged from 0 to 100 µg Cd/g soil and were comparable to surface soil Cd concentration levels found in the urban‐industrial region of northwestern Indiana. Data on germination, survival, height, and dry weight were collected. Germination, survival, and weight were found to exhibit a negative response to increasing soil Cd concentration over all species. Height, however, was not found to be a consistently good indicator of Cd response. While overall species' differences were noted, no differences could be conclusively shown among the species for Cd tolerance, although there were indications that this was the case. All effects noted were of a low level for the soil‐added Cd concentrations utilized.

Andropogon scoparius, Monarda fistulosa, and Rudbeckia hirtawere grown from seed for 6 weeks in an uncontaminated rural site soil and a heavy metal‐contaminated urban site soil. The rural site soil was amended with cadmium chloride. Plants grown in both soils were subjected to a one‐time drought stress. Survival, shoot weight, root weight, total weight, height, and weekly growth of Andropogonand Monardawere adversely affected by cadmium (Cd) addition and drought stress. Results were similar for Rudbeckiaexcept that shoot, root, and total weight were not significantly affected by drought stress. Root weights of Monardaand Andropogonwere more severely affected by Cd addition than were shoot weights. Root/shoot ratios were not significantly affected by drought stress for any species. Drought stress and Cd addition effects were found to be additive for Monardaand Andropogon. The effect of soil Cd addition on growth was found to be primarily due to an initial delay in growth rather than a reduction in the overall rate of growth. However, on the heavy metal contamination urban site soil the growth rate was found to be reduced. This was especially true for Andropogonwhich was found to be most tolerant of Cd addition to the rural site soil for the species tested. The reduction in growth rate of plants on the urban site soil was probably not due to Cd alone.

Little bluestem (Andropogon scoparius) and black‐eyed Susan (Rudbeckia hirta) were grown in two soils with all combinations of Cd, Zn, Pb, and Cu at two levels each for 12 weeks. Germination and establishment were completely retarded by the addition of 2,000 µg/g Zn as ZnCl2, which was due to a salt effect. Neither Cd nor Cu additions affected germination. A slight decrease in germination was noted for Pb additions of 900 µg/g which may also be associated with a salt effect. Cadmium at 10‐ and 20‐µg/g addition rates did not affect top or root dry weight. Lead and Cu additions reduced shoot and root dry weight yields of Andropogon scoparius, root weights being more severely affected than shoot weights. Metal additions to the urban site soil did not reduce yields to the extent they did on the rural site soil. However, yields on the urban site soil control treatment were lower compared to those for the rural site control treatment. DTPA extraction levels of heavy metals were not well correlated to plant concentrations for comparisons between the two soils. It was concluded that DTPA soil extraction may not be acceptable for metal availability comparisons among soils of differing pH. Circumstantial evidence was found for both synergistic and antagonistic effects among the heavy metals. These were of a low level and no consistent response could be determined over species or soils.