As human populations grow worldwide, there is an increasing need to address the problems associated with the creation and disposal of wastes. Although a variety of recent technologies have been shown to be somewhat effective in the remediation of metal contaminated soils, e.g., chemical extraction and stabilization, they are often expensive and labor-intensive. Additionally, these technologies can impart detrimental effects on the chemical and physical properties of the soil under treatment. As an alternative, the less expensive, more environmentally benign use of green plants as tools for the remediation of contaminated soils (phytoremediation) has been studied in recent years.The reported research activities studied the ability of a variety of green plants to extract lead (Pb), cadmium (Ca) and barium (Ba) from metal contaminated soil. Additionally, the researcher studied the degree to which the addition of the synthetic chelate diethylenetriaminepentaacetate (DTPA) and dilute HNO3 affected: the phytoextraction of metals from contaminated soil; the translocation of these metals within study plants; and the effects that the treatments had on biomolecule production in Zea mays, Glycine max, Brassica juncea and Helianthus annuus. A growth chamber study was also conducted to determine if several species of green plants (Ipomoea leptophylla, Lycopersicon esculentum, Capsicum annuum and Tagetes minuta) were capable of hyperaccumulating any of the metals present in the contaminated soil. Additionally, a leachate study was performed to determine the effects that DTPA and HNO3 had on soil Pb mobility rates.Samples were analyzed for Pb, Ca and Ba using FAAS and the data were further analyzed to determine universal measures of variance. While no plants showed overall significant (p=0.05) differences with regard to both treatment and plant part, all species were capable of both accumulating and distributing Pb from the contaminated soil; no plants were able to extract Ba from the soil; some plants extracted trace amounts of Cd in various plant parts. Significant (p=0.05) differences were measured in chlorophyll a, chlorophyll b and carotenoid concentrations with regard to both plant and treatment. Results from the Pb mobility study showed significant (p=0.01) differences in Pb mobility with regard to both treatment and time. / Department of Natural Resources and Environmental Management

The Canadian Council of Ministers of the Environment (CCME) developed guidelines for petroleum hydrocarbon (PHC) impacted field soils based on the “worst case” scenario of a fresh petroleum spill (CCME, 2001b; CCME, 2008b). Therefore, when these guidelines are applied as remedial benchmarks, they may be too conservative to be used as realistic targets as they do not account for weathering, which has been shown to decrease the toxicity of PHCs in soil. Chronic toxicity tests were performed using weathered PHC-impacted field soil from three different field sites (ON1, AB1 and BC1) and Folsomia candida. The highest PHC concentration of soil obtained from ON1 (635 mg/kg F2 and 12,000 mg/kg F3) and AB1 (610 mg/kg F2 and 2,900 mg/kg F3) did not affect F. candida survival and reproduction. However, when F. candida were exposed to PHC-impacted soil obtained from the BC1 site, a LC25 of 2,809 mg F2 + F3/kg was calculated for adult survival while an IC25 of 1,030 mg F2 + F3/kg was calculated for juvenile production. The toxicity at BC1 was postulated to be caused by the F2 concentration (it was the only site with high F2). Heat extraction and floatation methods were compared using the soil obtained from the ON1 field site. The number of adults obtained using the floatation method was always higher than the total number of adults obtained from the heat extraction method; however, only two of these results were statistically significant. This suggests that the floatation method is the best method to use to extract Folsomia candida and also indicates either method can be used with no significant effect on the conclusions. Chronic toxicity tests usually focus on measuring sub-lethal endpoints; however, only juvenile production was included in the Environment Canada protocol (Environment Canada, 2005; Environment Canada, 2007a). The endpoints of weight, length and width were added to chronic toxicity tests on AB1 and BC1 soils to determine if they were suitable endpoints. The highest concentration tested for AB1 (610 mg F2/kg and 2,900 mg F3/kg) had no effect on the weight, length or width of the adults. However, the toxicity data obtained for the BC1soils provided an EC25 of 421 mg F2 + F3/kg, 13,750 mg F2 + F3/kg and 17,425 mg F2 + F3/kg for weight, length and width, respectively. The EC25 of 421 mg F2 + F3/kg obtained for the weight of adults is lower than the IC25 of 1,030 mg F2 + F3/kg obtained for juvenile production which indicating that weight is a more sensitive endpoint than juvenile production. Avoidance-response tests involved placing a control and test soil on either side of a cylindrical container and adding 20 Folsomia candida to the midline (Environment Canada, 2007a; Liu et al., 2010). The results using soil obtained from AB1 showed no trend between soil avoidance and increasing PHC concentration. However, the avoidance-response test, using soil obtained from BC1, indicated that F. candida avoidance increased with increasing petroleum concentration. These results show that avoidance-response tests were able to predict the outcome of the chronic toxicity tests. Overall, the above results indicate that the CCME guidelines are too conservative to apply to weathered PHC-impacted field soil when the impacts are primarily F3. Results also indicate that F2 and F3 concentrations of 250 mg/kg and 2,900 mg/kg, respectively would not adversely affect F. candida adult survival, juvenile production or adult weight.

Knowledge of nutrient accumulation and partitioning in plants is important to determine the optimum timing of harvesting during phytoremediation of biosolids. This research showed that a greater proportion of nitrogen (N) and phosphorus (P) absorbed by cattail and switchgrass was partitioned to the aboveground biomass (AGB), but this partition decreased after the onset of nutrient retranslocation to roots. Therefore, AGB should be harvested prior to retranslocation in order to optimize nutrient phytoextraction. Trace elements partitioned preferentially to the root biomass, indicating that AGB harvesting will have little impact on their phytoextraction. Net mineralized N concentration (Nmin) in biosolids from the primary lagoon cell was optimized near field capacity [60% water filled pore space (WFPS) but changed little under drier conditions (30% WFPS). Under near-saturation conditions (90% WFPS), net Nmin decreased with incubation time, likely due to reduced mineralization and denitrification. Available (Olsen) P concentration was not affected by moisture content.

Salinity is one of the most severe environmental factors that limits global crop yield. Enhanced phytoremediation using plant growth promoting rhizobacteria (PGPR) has proven to be an effective and environmentally responsible approach to remove salt from the surface soil and reclaim salt-impacted soil for crop production. PGPR enhanced phytoremediation systems (PEPS) were applied to two research sites, Cannington Manor North (CMN) and Cannington Manor South (CMS) in southern Saskatchewan. The sites were impacted by brine leakage during upstream oil and gas production. A salt mass balance study was performed based on data collected from these two sites. Both sites were planted in June. Soil samples were taken in June 2009 (beginning of the season), August (midseason) and October (end of the season). Soil salinity changes throughout the season were monitored by measuring soil electrical conductivity (EC). The average surface soil ECe decreased from 3.7 dS/m to 3.1 dS/m at CMN, and from 10.2 dS/m to 9.2 dS/m at CMS in 2009 season. Plant samples that were collected in August and October were analyzed for sodium and chloride concentrations. These values were then converted into predicted ECe changes for the soil to compare with the actual changes in soil ECe. Plant uptake of NaCl was calculated to account for 25.2% and 28.1% of the decrease in surface soil ECe at CMN and CMS, respectively. However, plant samples were washed prior to salt content analysis. A considerable amount of salt could have been lost during the washing process. Several plant samples from other salt-impacted sites in Saskatchewan and Alberta were selected to examine salt loss due to tissue washing. The salt ions lost by washing were determined to be 44.4% for Na+ and 63.8% for Cl-. After the adjustment of plant NaCl uptake data by the loss due to washing, plant accumulation of NaCl accounted for 59.9% of the decrease in surface soil ECe at CMN and 56.1% at CMS. When plant uptake of K+ and Ca2+ were also taken into consideration by a simulation study, the decrease in surface soil ECe that was caused by plant uptake of salt ions accounted for 107.5% at CMN and 117.5% at CMS. This indicated that plants can have a significant role in the remediation of salt-impacted soil. The effects of PGPR (Pseudomonas spp. UW4 and Pseudomonas corrugata CMH3) treatment on selected physiological indicators, such as proline, superoxide dismutase (SOD), membrane leakage and photosynthesis, were examined on annual ryegrass (Lolium multiflorum). Plants were grown under three saline conditions: non-saline topsoil, non-saline topsoil spiked with NaCl to 10 dS/m, and high saline soil collected from a salt-impacted site diluted with non-saline topsoil to reach 10 dS/m. The shoot fresh weight of plants grown in spiked salt soil decreased by 74% and in diluted salt soil by 44%, respectively, compared to control soil. Both types of salt soil increased SOD activities by approximately 50%, proline concentrations by 20 to 25 fold, and membrane leakage levels by 1.6 to 2.8 fold. Significant impairment of photosynthetic performances, as indicated by the decreases in the chlorophyll fluorescence parameters Fv/Fm, yield and qP, and a parallel increase in qN, was also observed using Pulse Amplitude Modulation (PAM) fluorometry for plants in diluted impacted soil. PGPR moderately increased fresh weight and SOD activity. Both UW4 and CMH3 significantly increased proline concentration and lowered membrane leakage relative to untreated plants. Therefore, PGPR improve plant performance under salt stress by elevating proline levels, which can act as a quencher of destructive reactive oxygen species. PGPR treatment also restored all the chlorophyll fluorescence parameters nearly to the non-stressed level, indicating protection of photosynthetic tissues of PGPR treated plants under salt stress. Overall, PEPS was successfully applied to the salt-impacted sites. Plant uptake of salt played a major role in the decrease of surface soil ECe. PGPR’s role in enhancing plant performance under salt stress was suggested by the elevated proline concentrations, the decreased membrane leakage levels and the restored photosynthetic activity.

Soil salinity affects an estimated one billion hectares worldwide. Excess salinity inhibits plant growth, limiting crop production. This is caused by osmotic stress in saline soil, nutrient imbalance and specific ion toxicity. There have been many methods of remediation investigated, including excavation, soil washing and phytoremediation. Phytoremediation involves the growth of plants on impacted soils to degrade or sequester contaminants. The remediation of salts relies on the uptake of ions into plant biomass where the salt is sequestered and the biomass can then be harvested. This method removes the salt from the site and leaves the top soil in place, which aids in revegetation after site remediation is completed. Plant-growth promoting rhizobacteria (PGPR) improves plant growth by lowering the levels of stress ethylene within the plant, thereby increasing the biomass available to sequester ions. The objectives of this research were to investigate the efficiency of phytoremediation of salt impacted soils in field remediation sites. Previously isolated strains of PGPR (UW3, Pseudomonas putida; UW4, Pseudomonas putida; and CMH3, Pseudomonas corrugata) were used in field trials involving the planting of oats (Avena sativa), annual ryegrass (Lolium multiflorum), tall wheatgrass (Agropyron elongatum) and tall fescue (Festuca arundinacea C.V. Inferno). The salt tolerance of various switchgrass (Panicum virgatum L.) cultivars (Cave-In-Rock, Southlow, Forestburg, and common) was compared to tall wheatgrass and Inferno tall fescue to investigate the potential of switchgrass for phytoremediation. Improvement of seed germination under salt stress by H2O2 pre-treatment was investigated both as an individual treatment and in combination with CMH3 treatment. The ion uptake into plant biomass was iii compared to the change in salinity, to determine how much of the decrease in site salinity is accounted for by uptake of salt by plants. H2O2 pretreatment resulted in a 50% increase in root and shoot emergence of tall wheatgrass under 75 mM NaCl stress compared to control treatments, which matched the germination improvement observed with PGPR treatment. The combination of H2O2 and CMH3 showed a similar improvement to root emergence under stress, but had no observable effect on shoot emergence when compared to the no-H2O2-no-PGPR control. Switchgrass cultivars showed a lower germination rate than tall wheatgrass at salt levels from 0 mM to 150 mM NaCl. The measured uptake of Na+, K+, Ca2+, Mg2+ and Cl- into plant biomass during a phytoremediation field trial was able to account for approximately 70% of the observed change in salinity in 2008. In 2009 the uptake of Na+ and Cl- into Kochia scoparia, a weed species that invaded the field site after a hard frost, was able to account for 36% of the observed change in salinity.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 16, 2007) Includes bibliographical references (p. 85-89).

Zugl.: Hohenheim, Univ., Diss., 2005

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page, viewed on March 30, 2009. Major professor: Yarrow Nelson, Ph.D. "Presented to the Electrical Engineering Department Faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree of Master of Science in Civil and Environmental Engineering." "March 2009." Includes bibliographical references (p. 133-140). Will also be available on microfiche.

Thesis (Ph. D.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 16, 2009). Includes bibliographical references (p. 63-66).