Interest in selenium pollution and remediation technology has escalated during the past two decades. Although not known to be essential for plants, selenium is essential but could be toxic for humans and animals, depending on its concentration. A major selenium controversy in the 1980's emerged in California when the general public and scientific community became aware of selenium's potential as an environmental contaminant. After extensive research on several strategies to reduce loads of mobile Se for entering the agricultural ecosystem a plant-based technology, defined as 'phytoremediation' received increasing recognition, as a low-cost environmentally friendly approach for managing soluble Se in the soil and water environment. Successful long-term field remediation of Se by plants is, however, dependent upon acceptance and widespread use by growers, who are also concerned about potential commercial value from using the plant-based technology. Obtaining products with economic value from plants used in the cleanup of soil would certainly be an additional benefit to phytoremediation, which could help sustain its long-term use.

The removal of phenanthrene, anthracene and benzo(a)pyrene added at three different concentrations was investigated with or without earthworms (Eisenia fetida) within 11 weeks. Average anthracene removal by the autochthonous micro-organisms was 23%, 77% for phenanthrene and 13% for benzo(a)pyrene, while it was 51% for anthracene, 47% for benzo(a)pyrene and 100% for phenanthrene in soil with earthworms. At 50 and 100 mg phenanthrene kg−1E. fetida survival was 91% and 83%, but at 150 mg kg−1 all died within 15 days. Survival of E. fetida in soil amended with anthracene ≤1000 mg kg−1 and benzo(a)pyrene ≤150 mg kg−1 was higher than 80% and without weight loss compared to the untreated soil. Only small amounts of PAHs were detected in the earthworms. It was concluded that E. fetida has the potential to remove large amounts of PAHs from soil, but more work is necessary to elucidate the mechanisms involved.

In Hypericumspecies some specimens have been found to display higher levels of the toxic heavy metal Cd than the proposed guide value of 0.5mgkg. Plant and soil samples from various regions in Eastern Austria were collected to study the variability in the Cd content of the herbs and relate it to selected soil properties and soil micronutrient contents. The soils contained between 0.01 and 0.44mgkg-¹Cd in the dry soil. Altogether about 7% of the collected plant samples exceeded 0.5mgkg-¹Cd of dry shoots, the proposed guide value for the drug Herba Hyperici. Plants low in Cd were found on sites in the Alpenvorland, the Hainburger Berge, the Eastern Viennese Basin and the Northern Limestone Alps where the levels did not exceed 0.3mgkg-¹Cd of dry shoots. Higher Cd levels in the plants were present in material from the Waldviertel, the Southern Wienerwald and the Semmering region where often bioaccumulation factors for Cd above 1 could be calculated. In these regions the soil pH and carbonate content was somewhat lower than in other regions whereas the soil organic carbon varied greatly. In the Waldviertel some plants from a field were somewhat higher in Cd than nearby plants from the natural vegetation. In a regression analysis, the soil pH, soil organic carbon and soil Cd content were the main factors influencing Cd accumulation in the plant shoots.

Zinc toxicity thresholds for reclamation plants are largely unknown. As a result, ecological risk assessments often rely on toxicity thresholds for agronomic species, which may differ from those of restoration species. Our objective was to provide Zn toxicity thresholds for forb species that are commonly used in reclamation activities. We used a greenhouse screening study where seedlings of yarrow (Achillea millefolium L.), Bigelow's tansyaster (Machaeranthera bigelovii (Gray) Greene var. bigelovii), blue flax (Linum perenne L. var. Appar), alfalfa (Medicago sativa L. var. Ladak), Palmer's penstemon (Penstemon palmeri Gray), and Rocky Mountain penstemon (Penstemon strictus Benth. var. Bandera) were grown in sand culture and exposed to increasing concentrations of Zn. Lethal concentrations (LC50 - substrate Zn concentration resulting in 50% mortality), effective concentrations (EC50 - substrate Zn concentration resulting in 50% biomass reduction), and phytotoxicity thresholds (PT50 - tissue Zn concentration resulting in 50% biomass reduction) were then determined. Phytotoxicity thresholds and effective concentrations for these reclamation species were relatively consistent between species. Our estimates of PT50-shoot for these species range from 1258 to 3214 mg Zn kg-¹ . Measures of EC50-plant for these restoration forbs ranged from 82 to 214 mg Zn L-¹ . These thresholds might be more useful for risk assessors working on reclamation sites than those based on non-reclamation species that are widely used.

The objectives of this study were to simplify sample preparation and validate mercury detection in soil and plant samples using inductively coupled plasma atomic emission spectroscopy (ICP-AES). A set of mercury contaminated and mercury free soil and plant samples were digested and analyzed by ICP-AES, inductively coupled plasma mass spectrometry (ICP-MS), and cold vapor atomic absorption spectroscopy (CVAAS). Results show that mercury measurements in soil and plant samples using ICP-AES were in agreement with those analyzed using ICP-MS and CVAAS. The concentrations of mercury in soils and plant tissues determined by ICP-AES were 92.2% and 90.5% of those determined by CVAAS and ICP-MS, respectively. Digestion of soil samples with 4 M HNO₃ and direct measurement by ICP-AES without reduction of Hg²⁺ to Hg⁰ gave a reasonable and acceptable recovery (92%) for determining Hg in soils. We conclude that ICP-AES with optimized conditions (addition of gold chloride, extension of washing time, linear working range, and selection of wavelength - 194 nm) resulted in reliable detection of mercury in environmental samples.

The effects of two different biological treatments on hydrocarbon degradation and on soil biological activities were determined during a 100-d incubation period. An evaluation of soil biological activities as a monitoring instrument for the decontamination process of diesel-oil contaminated soil was made using measurements of organic carbon content, soil microbial respiration, soil ATP and dehydrogenase, β-glucosidase, lipase enzyme activities. Five samples were used: S (control, uncontaminated soil), CS (contaminated soil), SCS (sterilized contaminated soil), CFS (contaminated soil plus N and P), CCS (contaminated soil plus compost). The relationships between soil parameters and the levels of total petroleum hydrocarbons (TPH) residues were investigated. Results showed that inorganic nutrients NP and compost stimulated hydrocarbon biodegradation but not all biological activities to a significant extent. The residual hydrocarbon trend was positively related with that of the organic C content, microbial respiration and with β-glucosydase activity, while both soil lipase and dehydrogenase activities were negatively related with the hydrocarbon trend. Lipase activity was found to be the most useful parameter for testing hydrocarbon degradation in soil.

The feasibility of degrading 16 USEPA priority polycyclic aromatic (PAH) hydrocarbons (PAHs) with heat and Fe(II)-EDTA catalyzed persulfate oxidation was investigated in the laboratory. The experiments were conducted to determine the effects of temperature (i.e. 20 [composite function (small circle)]C, 30 [composite function (small circle)]C and 40 [composite function (small circle)] C) and iron-chelate levels (i.e., 250 mg/L-, 375 mg/L- and 500 mg/L-Fe(II)) on the degradation of dissolved PAHs in aqueous systems, using a series of amber glass jars as the reactors that were placed on a shaker inside an incubator for temperature control. Each experiment was run in duplicate and had two controls (i.e., no persulfate in systems). Samples were collected after a reaction period of 144 hrs and measured for PAHs, pH and sodium persulfate levels. The extent of degradation of PAHs was determined by comparing the data for samples with the controls. The experimental results showed that persulfate oxidation under each of the tested conditions effectively degraded the 16 target PAHs. All of the targeted PAHs were degraded to below the instrument detection limits (~4 μ/L) from a range of initial concentration (i.e., 5 μ/L for benzo(a)pyrene to 57 μ/L for Phenanthrene) within 144 hrs with 5 g/L of sodium persulfate at 20 [composite function (small circle)] C, 30 [composite function (small circle)]C and 40 [composite function (small circle)]C. The data indicated that the persulfate oxidation was effective in degrading the PAHs and that external heat and iron catalysts might not be needed for the degradation of PAHs. The Fe(II)-EDTA catalyzed persulfate also effectively degraded PAHs in the study. In addition, the data on the variation of persulfate concentrations during the experiments indicated that Fe(II)-EDTA accelerated the consumption of persulfate ions. The obtained degradation data cannot be used to evaluate the influence of temperature and Fe(II) levels on the PAH degradation because the PAHs under each of the tested conditions were degraded to below the instrument detection limit within the first sampling point. However, these experiments have demonstrated the feasibility of degrading PAHs in aqueous systems with persulfate oxidation. Additional tests are being conducted to evaluate the effectiveness of treating PAHs in soils and obtaining the rate of degradation of PAHs with persulfate oxidation. Two sets of laboratory experiments were conducted to evaluate the ability of sodium persulfate in oxidizing real world PAH-contaminated soils collected from a Superfund site in Connecticut. The first set of soil sample were treated only with persulfate and to the second batch, mixture of persulfate and Fe(II)-EDTA solutions were added. The results of the second test showed that within 24 hours, 75% to 100% of the initial concentrations of seven PAH compounds detected in the soil samples were degraded by sodium persulfate mixed with FE(II)-EDTA.