Water quality of runoff from revegetated mine spoil

Permanent vegetation plots were established on mixed overburden and topsoiled overburden on a lignite test pit in eastern Texas in 1982. Vegetative treatments included two grass-legume treatments [switchgrass (panicum virgattun) — sideoats grama (Bouteloua curtipendula) — subterrancan elover (Trifolitun subterranean) and litte bluestem (Schizachyriun scoparium) — sideoats grama (Bouteloua curtipendula) — Illinois hundleflower (Dessmanthus illinoiensis)] and three monocultures [Coastal bermudagrass (Cynodon dactylon), bahia grass (paspalum notatum) and yellow Indiangrass (Sorghastrum nutans)]. Water was applied to the 0.5m² plots using a sprinklertype rainfall simulator and quality of runoff was determined for each plot. Parameters analyzed included: settleable solids, total filterable solids, sediment production, infiltration rate, nitrites, nitrates, total iron and total manganese. Topsoiling significantly increased inliltration and significantly decreased filterable sediments, sediment production and settleable solids. The hydrologie qualities of the switchgrass-sideoats grama-subterranean elover mixture coincided closely with those of the Coastal bermudagrass monoculture.Authors are presently graduate research assistant and assistant professor. Range Science Department. Texas A&M University. College Station, Texas 77843. Acknowledgement is given to Northwestern Resources Co. for providing the funding for this project.     

How regulations impact innovative environmental technologies: A recent case study

The White House Conference on Environmental Technology, held December 12–14, 1994, is the most recent of many events building toward a national environmental technology strategy, which President Clinton will announce on April 22, 1995, the 25th anniversary of Earth Day. Promoting innovation and eliminating barriers to new environmental technologies are important issues in developing this strategy. Anticipating these developments, EPA launched its own Technology Innovation Strategy in early 1994. EPA's strategy explicitly calls for strengthening incentives for technology innovation within regulatory, policy, and enforcement programs. In this light, it is worthwhile to look at a recent case study showing how regulations impact innovative environmental technologies, particularly because there appears to be a gathering political sentiment for deeper regulatory reform.     

Effects of kelthane on the estuarine shrimp Crangon tranciscorum

The chlorinated hydrocarbon pesticide Kelthane was assayed for effects on food consumption, molting rate, cannibalism, respiration, mortality and behavior of the estuarine shrimp Crangon franciscorum Stimpson. The test system was a single-pass pulse-flow apparatus employing a modified Mount-Brungs style diluter. Treatment levels were 0, 14, 33 and 81 g l^-1 Kelthane at 16.6°C and 19 S over an exposure period of 317 h. Exposure to Kelthane reduced food consumption, molting rate, cannibalism, and respiration. Behavior also was abnormal in exposed shrimp. They spent more time swimming, were less coordinated and had feeble escape reactions. Kelthane was very toxic to C. franciscorum with LT₅₀ values of 163, 196 and 264 h for shrimp exposed to 81, 33 and 14 g l^-1 respectively. The incipient lethal level of Kelthane is probably below 14 g l^-1.     

Population-level effects of augmented herbivory on Lespedeza cuneata: implications for biological control.

Invasive species pose significant ecological costs, and therefore successful management techniques are important. One commonly employed method is biological control. The success of biological control depends largely on whether additional inflicted damage can successfully reduce the fitness and population growth rate of a target species. Here, we simulate herbivory on the invasive Lespedeza cuneata and create stage-structured projection models to determine if augmented herbivory by a leaf-chewing biological control agent would regulate the population growth rate of this species. We found that augmented herbivory influenced stage transitions of plants in the smallest stage class, causing higher mortality and reduced growth. No other effect was found on stage transitions or fecundities, despite manipulation of herbivory at exceptionally high levels (up to 80% leaf loss). None of the clipping treatments significantly reduced the population growth rate of L. cuneata. We conclude that biological control by a leaf chewing herbivore would not likely be successful, even if an exceptionally large amount of each plant were consumed. We suggest that this approach, a combination of simulated herbivory and demographic modeling, will provide essential information for understanding the utility of biological control to curb the population growth of invasive plant species.     

Anaerobic decomposition of halogenated aromatic compounds

Halogenated compounds constitute one of the largest groups of environmental pollutants, partly as a result of their widespread use as biocides, solvents and other industrial chemicals. A critical step in degradation of organohalides is the cleavage of the carbon?halogen bond. Reductive dehalogenation is generally the initial step in metabolism under methanogenic conditions, which requires a source of reducing equivalents, with the halogenated compound serving as an electron acceptor. Dehalogenation is greatly influenced by alternate electron acceptors; e.g. sulfate frequently inhibits reductive dehalogenation. On the other hand, a number of halogenated aromatic compounds can be degraded under different electron-accepting conditions and their complete oxidation to CO(2) can be coupled to processes such as denitrification, iron(III)-reduction, sulfate reduction and methanogenesis. Reductive dehalogenation was the initial step in degradation not only under methanogenic, but also under sulfate- and iron(III)-reducing conditions. Dehalogenation rates were in general slower under sulfidogenic and iron-reducing conditions, suggesting that dehalogenation was affected by the electron acceptor. The capacity for dehalogenation appears to be widely distributed in anoxic environments; however, the different substrate specificities and activities observed for the halogenated aromatic compounds suggest that distinct dehalogenating microbial populations are enriched under the different reducing conditions. Characterization of the microbial community structure using a combination of biomolecular techniques, such as cellular fatty acid profiling, and 16 S rRNA fingerprinting/sequence analysis, was used to discern the distinct populations enriched with each substrate and under each electron-accepting condition. These combined techniques will aid in identifying the organisms responsible for dehalogenation and degradation of halogenated aromatic compounds.     

Determination of chemical availability of cadmium and zinc in soils using inert soil moisture samplers

A rapid method for extracting soil solutions using porous plastic soil-moisture samplers was combined with a cation resin equilibration based speciation technique to look at the chemical availability of metals in soil. Industrially polluted, metal sulphate amended and sewage sludge treated soils were used in our study. Cadmium sulphate amended and industrially contaminated soils all had > 65% of the total soil solution Cd present as free Cd2+. However, increasing total soil Cd concentrations by adding CdSO4 resulted in smaller total soil solution Cd. Consequently, the free Cd2+ concentrations in soil solutions extracted from these soils were smaller than in the same soil contaminated by sewage sludge addition. Amendment with ZnSO4 gave much greater concentrations of free Zn2+ in soil solutions compared with the same soil after long-term Zn contamination via sewage sludge additions. Our results demonstrate the difficulty in comparing total soil solution and free metal ion concentrations for soils from different areas with different physiochemical properties and sources of contamination. However, when comparing the same Woburn soil, Cd was much less available as Cd2+ in soil solution from the CdSO4 amended soils compared with soil contaminated by about 36 years of sewage sludge additions. In contrast, much more Zn was available in soil solution as free Zn2+ in the ZnSO4 amended soils compared with the sewage sludge treated soils.     

The extraction and utilization of local and scientific geospatial knowledge within the Bluff oyster fishery, New Zealand

This paper assesses the Bluff oyster fishery in New Zealand as a case study in common pool resource management. It discusses ways in which modern information technology, augmented by low-tech data gathering strategies and community ethnography, can be used to produce an integrated scientific and local knowledge-inspired fishery database that lends itself to fostering collaboration in resource management and planning. The specific context and state of the oyster fishery in Bluff are described. Issues regarding undocumented and ephemeral intergenerational knowledge, much of which is geospatial in nature, on the fishery, the current crisis that many see in the future of the fishery, and a lack of cohesion or common sense of purpose between the stakeholder groups are discussed. It is argued that the digital resource that results from the integration of local and scientific knowledge and the potential community building processes that can ensue from collaboration and dialogue around this centrepiece are of central importance in developing an oyster fishery management plan that is holistic in concept and sustainable in purpose.     

Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland

Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m × 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m × 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides.