Field evaluation of in situ remediation of a heavy metal contaminated soil using lime and red-mud

We evaluated the effectiveness of lime and red mud (by-product of aluminium manufacturing) to reduce metal availability to Festuca rubra and to allow re-vegetation on a highly contaminated brown-field site. Application of both lime and red mud (at 3 or 5%) increased soil pH and decreased metal availability. Festuca rubra failed to establish in the control plots, but grew to a near complete vegetative cover on the amended plots. The most effective treatment in decreasing grass metal concentrations in the first year was 5% red mud, but by year two all amendments were equally effective. In an additional pot experiment, P application in combination with red mud or lime decreased the Pb concentration, but not total uptake of Pb in Festuca rubra compared to red mud alone. The results show that both red mud and lime can be used to remediate a heavily contaminated acid soil to allow re-vegetation.     

Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions

This paper is particularly related to elemental mercury (Hg0) oxidation and divalent mercury (Hg2+) reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO2). As a powerful oxidant and chlorinating reagent, Cl2 has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO2, NO, as well as H2O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO2 and NO on Hg0 oxidation and Hg2+ reduction with the intent of unraveling unrecognized interactions among Cl species, SO2, and NO most importantly in the presence of H2O. The experimental results demonstrated that SO2 and NO had pronounced inhibitory effects on Hg0 oxidation at high temperatures when H2O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg2+ back into its elemental form. Data revealed that SO2 and NO were capable of promoting homogeneous reduction of Hg2+ to Hg0 with H2O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H2O was removed from the gas blend.     

Nitrogen-fixation by cyanobacteria associated withCodium fragile (Chlorophyta): Environmental effects and transfer of fixed nitrogen

N₂-fixation associated with the green macroalgaCodium fragile subsp.tomentosoides (van Goor) Silva from Long Island, New York, USA, was attributable to several species of endophytic cyanobacteria. Rates of N₂-fixation ranged from 0.03 to 3.2µg N g^–1 dry wt h^–1 in freshly collected plants from several sites. Growth of the cyanobacteria appeared to be light-limited, due to the transmission of only 5 to 10% of incident light through the pigmented surface-layer of the macroalga. Daily irradiance was the most important factor determining both abundance of cyanobacterial cells and rate of N₂-fixation. The rate was also affected by instantaneous irradiance, and increased twofold from dark to ambient surface irradiance. Rates were reduced at low temperature (8°C) but showed no temperature effect between 12° and 26°C. External concentrations of dissolved inorganic nitrogen (DIN) up to 20µM did not influence N₂-fixation rate, but long-term exposure to 60µmol l^–1 d^–1 of NH ₄ ⁺ caused a reduction in the rate. InC. fragile grown under high daily irradiance and low external DIN concentration, ~50% of the assimilated-N was attributable to N₂-fixation. However, chlorophyllb extracted from plants grown with¹⁵N₂ showed an atom % excess¹⁵N of less than 0.1, suggesting that only a small proportion of the bacterially fixed-N was transferred to the seaweed. The association betweenC. fragile and its endophytic cyanobacteria appears to be based primarily on microhabitat suitability, rather than mutual metabolic dependence. It is doubtful that N₂-fixation by cyanobacteria is important to the ecological success of this seaweed species.     

Chinook salmon use of spawning patches: relative roles of habitat quality, size, and connectivity.

Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the implications this shift has for how habitats may be prioritized for conservation, it has been rare to assess the relative importance of these habitat components. We used an information-theoretic approach to select the best models from sets of logistic regressions that linked habitat quality, size, and connectivity to the occurrence of chinook salmon (Oncorhynchus tshawytscha) nests. Spawning distributions were censused annually from 1995 to 2004, and data were complemented with field measurements that described habitat quality in 43 suitable spawning patches across a stream network that drained 1150 km2 in central Idaho. Results indicated that the most plausible models were dominated by measures of habitat size and connectivity, whereas habitat quality was of minor importance. Connectivity was the strongest predictor of nest occurrence, but connectivity interacted with habitat size, which became relatively more important when populations were reduced. Comparison of observed nest distributions to null model predictions confirmed that the habitat size association was driven by a biological mechanism when populations were small, but this association may have been an area-related sampling artifact at higher abundances. The implications for habitat management are that the size and connectivity of existing habitat networks should be maintained whenever possible. In situations where habitat restoration is occurring, expansion of existing areas or creation of new habitats in key areas that increase connectivity may be beneficial. Information about habitat size and connectivity also could be used to strategically prioritize areas for improvement of local habitat quality, with areas not meeting minimum thresholds being deemed inappropriate for pursuit of restoration activities.     

The Greater Yellowstone Ecosystem: Challenges for Regional Ecosystem Management

An adaptive management approach is necessary but not sufficient to address the long-term challenges of the Greater Yellowstone Ecosystem (GYE). Adaptive management, in turn, has its own particular challenges, of which we focus on two: science input, and stakeholder engagement. In order to frame our discussion and subsequent recommendations, we place the current management difficulties into their historical context, with special emphasis on the 1990 Vision document, which attempted a broad synthesis of management goals for the ecosystem. After examining these two key challenges in the context of the GYE, we make several recommendations that would allow for more effective ecosystem management in the long term. First, we recommend adoption of the GYE as a site for long-term science research and monitoring with an emphasis on integrative research, long-term federal funding, and public dissemination of data. Second, we conclude that a clearer prioritization of legislative mandates would allow for more flexible ecosystem management in the GYE, a region where conflicting mandates have historically led to litigation antithetical to effective ecosystem management. Finally, we recommend a renewed attempt at an updated Vision for the Future that engages stakeholders (including local landholders) substantively from the outset.     

World supply of non fuel minerals: The geological constraints

The feasibility of trebling production of essential non fuel minerals by AD 2000 is considered in relation to a rise in world population to 6 billion (10⁹). Adequate supplies of common bulk ‘minerals’ like sand and gravel, brick clays and saline deposits, are assured, but mining will place additional strains on local environments. Ores of the metals that can be regarded as available in sufficient quantities include iron, aluminium, chromium, titanium, copper and nickel, and possibly also lead and zinc. In spite of the geological constraints imposed by complexity of geometry and genesis, reasoned resource estimates are possible for these, but they may not be feasible for rarer necessary minerals, such as those of the precious metals, mercury, niobium and flourine. The extraction of even the commonest of the non fuel minerals is conditioned by the availability of abundant energy at economic prices – this should be regarded as the critical factor.     

Effects of Sulfur Dioxide and Nitric Oxide on Mercury Oxidation and Reduction under Homogeneous Conditions

Abstract

This paper is particularly related to elemental mercury (Hg⁰) oxidation and divalent mercury (Hg²⁺) reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO₂). As a powerful oxidant and chlorinating reagent, Cl₂ has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO₂, NO, as well as H₂O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO₂ and NO on Hg⁰ oxidation and Hg²⁺ reduction with the intent of unraveling unrecognized interactions among Cl species, SO₂, and NO most importantly in the presence of H₂O. The experimental results demonstrated that SO₂ and NO had pronounced inhibitory effects on Hg⁰ oxidation at high temperatures when H₂O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg²⁺ back into its elemental form. Data revealed that SO₂ and NO were capable of promoting homogeneous reduction of Hg²⁺ to Hg⁰ with H₂O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H₂O was removed from the gas blend.     

Focus of Attention at Work and Leader-Follower Relationships

Three different studies examine moderating effects of focus of attention at work on leader-follower relationships, using the typology developed by Howell, Dorfman, and Kerr (1986). Survey data were collected from over 1300 subjects. Results indicate that: (1) high focus on the supervisor while at work enhances leader behaviour-subordinate satisfaction and behaviour relationships, (2) high focus on off-job factors while at work enhances leader behaviour-subordinate satisfaction relationships, and (3) high focus on off-job factors while at work weakens leader behaviour-subordinate behaviour relationships. Theoretical implications for the study of organizational behaviour are discussed, as well as practical issues for enhancing leader behaviour effectiveness in work organizations.     

Field evaluation of Cd and Zn phytoextraction potential by the hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri

Field trials were undertaken to investigate the effect of the application of metal mobilizing agents, different sowing strategies and length of growing season on the extraction of Cd and Zn from soils by Thlaspi caerulescens and Arabidopsis halleri. None of the mobilizing agents used enhanced metal accumulation by T. caerulescens. Between 1998 and 2000, on average across plots where Cd or Zn exceeded allowable limits, T. caerulescens removed 1.3 and 0.3% of the total soil Cd and Zn. In one season when T. caerulescens was grown for 14 months, 21.7 and 4.4% of the total soil Cd and Zn was removed. This was larger than values found when T. caerulescens was grown for 4 months. A. halleri accumulated similar concentrations of Zn, but lower Cd concentrations than T. caerulescens. The results indicate that metal phytoextraction using T. caerulescens can be used to clean up soils moderately contaminated by Cd.