Robert J. Fellows

Comparative metabolic behavior and interrelationships of Tc and S in soybean plants

The comparative behavior of sulfur (S) and technetium (Tc) in soybean seedlings shows gross subcellular distributions to be similar for these oxyanions. More than 75% of the tissue-deposited Tc remains soluble and extractable. Differences in Tc fixation/incorporation were noted for the nuclear and chloroplast fractions of leaf and root cells. Pulse studies showed that soluble protein and nitrate reductase levels rose in response to Tc accumulation by sink leaves but not source leaves. In vitro assay of chloroplast-based S reduction and incorporation systems showed Tc to be reduced and incorporated into amino nitrogen-containing products. A hypothesis related to the metabolic behavior of Tc in plants is presented.

100-N Area Strontium-90 Treatability Demonstration Project: Food Chain Transfer Studies for Phytoremediation Along the 100-N Columbia River Riparian Zone

Strontium-90 (90Sr) exceeds the U.S. Environmental Protection Agency’s drinking water standards for groundwater (8 picocuries/L) by as much as a factor of 1000 at several locations within the Hanford 100-N Area and along the 100-N Area Columbia River shoreline). Phytoextraction, a managed remediation technology in which plants or integrated plant/rhizosphere systems are employed to phytoextract and/or sequester 90Sr, is being considered as a potential remediation system along the riparian zone of the Columbia River as part of a treatment train that includes an apatite barrier to immobilize groundwater transport of 90Sr. Phytoextraction would employ coyote willow (Salix exigua) to extract 90Sr from the vadose zone soil and aquifer sediments (phytoextraction) and filter 90Sr (rhizofiltration) from the shallow groundwater along the riparian zone of the Columbia River. The stem and foliage of coyote willows accumulating 90Sr may present not only a mechanism to remove the contaminant but also can be viewed as a source of nutrition for natural herbivores, therefore becoming a potential pathway for the isotope to enter the riparian food chain. Engineered barriers such as large and small animal fencing constructed around the field plot will control the intrusion of deer, rodents, birds, and humans. These efforts, however, willmorexa0» have limited effect on mobile phytophagous insects. Therefore, this study was undertaken to determine the potential for food chain transfer by insects prior to placement of the remediation technology at 100-N. Insect types include direct consumers of the sap or liquid content of the plants vascular system (xylem and phloem) by aphids as well as those that would directly consume the plant foliage such as the larvae (caterpillars) of Lepidoptera species. Heavy infestations of aphids feeding on the stems and leaves of willows growing in 90Sr-contaminated soil can accumulate a small amount (~0.15 ± 0.06%) of the total label removed from the soil by the plant over a 17-day exposure period. The 90Sr in the exuded honeydew during this period amounted to 1.17 ± 0.28% of this total label. The honeydew would eventually be deposited into the soil at the base of the plant, but the activity would be so dispersed as to be undetectable. Moth larvae will consume 90Sr contaminated leaves but retain very little of the label (~0.02%) and only that contained in their digestive tracts. As the moths pupated and became adults, they contained no detectable amounts of 90Sr. Over the 10-day exposure period, ~4% of the phytoextracted 90Sr was lost from the plant as moth feces. However, like the honeydew, feces dispersed into the soil were undetectable. As the plant diminishes the content of 90Sr in the soil, the activity of the label in the leaves and new stems would also diminish. The results of these studies indicate that the risk for detectable transfer of 90Sr from willow trees growing in the contaminated soil along the 100-N shoreline through the food chain of herbivorous insects would be very slight to non-existent«xa0less

The Impact of Humidity, Temperature and Ultraviolet Light on the Near-Field Environmental Fate of Pinacolyl Alcohol, Methyl Iodide, Methylphosphonic Dichloride (DCMP) and Thionyl Chloride Using an Environmental Wind Tunnel

Understanding the near-field fate of parent chemicals and their decay products in the atmosphere provides essential information for the development of remote chemical sensors. To elucidate the near-field fate of candidate chemical signatures, selected gas phase compounds were introduced into atmospheres of varying humidity, temperature and incident light flux. These atmospheres were maintained in an environmental wind tunnel for periods typical of near-field transport scenarios. The range of humidity and temperature into which the compounds were emitted encompassed arid, temperate, and tropical values. Simulated sunlight exposure was used to evaluate the impact of time of release on signature composition. The rates of compound decay and evolution of transformation products under the various environmental conditions were monitored in real time. A Fourier transform infrared spectrometer and a gas chromatograph/mass spectrometer were used to determine chemical concentration, evaluate detectability, and identify potential interferences to the detection capability. Specifically, this report describes the initial system function tests with pinacolyl alcohol and methyl iodide and subsequent atmospheric fate experiments with methylphosphonic dichloride and thionyl chloride. Test system function was evaluated using pinacolyl alcohol because as a relatively non-reactive compound, it served as a negative control for the system. Methyl iodide is a compound knownmorexa0» to photodissociate in the atmosphere and therefore was used to evaluate the effectiveness of the test system to detect a known positive effect under specific conditions. Results from the function tests showed that sufficient vapor generation into the large volume of the wind tunnel could be accomplished within a reasonable time period and that the operating conditions of the wind tunnel did not appear to affect the decay rate of the two initial test chemicals. As expected, no near-field decay of pinacolyl alcohol was observed under a wide range of temperature and humidity conditions. Further, both analytical techniques could detect pinacolyl alcohol at and below field-relevant concentrations. No significant difference in the disappearance of pinacolyl alcohol from the wind tunnel atmosphere was observed when the contaminated atmosphere was illuminated with simulated sunlight. We also observed that plants exposed to pinacolyl alcohol absorbed it and then continued to outgas the absorbed compound for a period of hours after being removed from the contaminated atmosphere. Methyl iodide similarly proved unreactive as a function of humidity and temperature. It is known to photodissociate when exposed to ultraviolet light. Relative humidity was found to play an important role in the environmental fate of both compounds. DCMP exhibited an exponential decay rate whose lifetime was a function of the relative humidity. Compound dissociation was so rapid at high relative humidity that sufficient concentrations of the parent chemical could not be attained to permit reliable determination of the decay rate. These indicate an atmospheric lifetime of less than 10 minutes for typical conditions. This study looked at environmental conditions typical of midlatitude environmental conditions, particularly humidity. The results indicate that the near field fate of parent compounds must be considered when choosing chemical signatures for detection. Failure to do so may cause one to incorrectly identify pollution sources or inaccurately estimate their production.«xa0less

100-N Area Strontium-90 Treatability Demonstration Project: Phytoextraction Along the 100-N Columbia River Riparian Zone – Field Treatability Study

Strontium-90 (90Sr) is present both in the aquifer near the river and in the vadose and riparian zones of the river’s shore at 100-NR-2. Phytoextraction of 90Sr is being considered as a potential remediation system along the riparian zone of the Columbia River. Phytoextraction would employ coyote willow (Salix exigua). Past studies have shown that willow roots share uptake mechanisms for Sr with Ca, a plant macronutrient as well as no discrimination between Sr and 90Sr. Willow 90Sr concentration ratios [CR’s; (pCi 90Sr/g dry wt. of new growth tissue)/(pCi 90Sr/g soil porewater)] were consistently greater than 65 with three-quarters of the assimilated label partitioned into the above ground shoot. Insect herbivore experiments also demonstrated no significant potential for bioaccumulation or food chain transfer from their natural activities. The objectives of this field study were three-fold: (1) to demonstrate that a viable, “managed” plot of coyote willows can be established on the shoreline of the Columbia River that would survive the same microenvironment to be encountered at the 100-NR-2 shoreline; (2) to show through engineered barriers that large and small animal herbivores can be prevented from feeding on these plants; and (3) to show that once established, the plants will providemorexa0» sufficient biomass annually to support the phytoextraction technology. A field treatability demonstration plot was established on the Columbia River shoreline alongside the 100-K West water intake at the end of January 2007. The plot was delimited by a 3.05 m high chain-link fence and was approximately 10 x 25 m in size. A layer of fine mesh metal small animal screening was placed around the plot at the base of the fencing to a depth of 45 cm. A total of sixty plants were placed in six slightly staggered rows with 1-m spacing between plants. The actual plot size was 0.00461 hectare (ha). At the time of planting (March 12, 2007), the plot was located about 10 m from the river’s edge. Less than two weeks later (March 21), the river began the spring rise. Periodic (daily) or continuous flooding occurred at the site over the next 3 to 4 months. River levels at times were over the top of the enclosure’s fence. This same pattern was repeated for the next 2 years. It was however evident that even submerged for part, or all of the day, that the plants continued to flourish. There were no indications of herbivory or animal tracks observed within the plot although animals were present in the area. Biomass production over the three years followed a typical growth curve with a yield of about 1 kg for the first year when the trees were establishing themselves, 4 kg for the second, and over 20 kg for the third when the trees were entering the exponential phase of growth. On a metric Ton per hectare (mT/ha) basis this would be 0.2 mT/ha in 2007, 0.87 mT/ha in 2008, and 4.3 mT/ha in 2009. Growth curve extrapolation predicts 13.2 mT/ha during a fourth year and potentially 29.5 mT/ha following a fifth year. Using the observed Ca and Sr concentrations found in the plant tissues, and Sr CR’s calculated from groundwater analysis, projected biomass yields suggest the trees could prove effective in removing the contaminant from the 100-NR-2 riparian zone.«xa0less