A conspicuous H<Subscript>2</Subscript>S-oxidizing microbial mat from a high-latitude Arctic fjord (Young Sound,NE Greenland)

A several centimeter thick, H₂S-oxidizing microbial mat was encountered in a high-latitude Arctic fjord. Microscopic investigations revealed that the mat contained numerous filamentous bacteria, and fluorescence in situ hybridization showed that the vast majority of these belonged to -Proteobacteria and that Thiothrix spp. was present. The mat grew on a layer of accumulated decaying macroalgae and was characterized by a complex three-dimensional structure consisting of numerous holes, voids and chimney-like structures. Microsensor measurements performed in situ and in a laboratory-established mesocosm showed a highly dynamic O₂, pH and H₂S distribution, especially around protruding structures of the mat. Detailed microsensor investigations documented that anoxic sulfidic water emerged trough the chimneys and indicated a microcirculation, replenishing the emerging water with oxygenated water in areas were the mat was absent. This governed an efficient advective exchange of solutes and presumably allowed the mat to grow to the extensive thickness of several centimeters.Communicated by M. Kühl, Helsingør     

Transformation products of 2-benzoxazolinone (BOA) in soil

Three degradation experiments were performed to examine the formation of transformation products from 2-benzoxazolinone (BOA) in different soil types and concentrations. In two experiments using BOA in low concentration (400 microgkg(-1)) only one unidentified transformation product was found, whereas in the degradation experiment in high concentration (400 mgkg(-1)) several metabolites occurred. Two of these metabolites, 2-amino-(3H)-phenoxazin-3-one (APO); and 2-acetylamino-(3H)-phenoxazin-3-one (AAPO) were synthesized to prove their identity. This is the first time that the successive formation of these types of compounds from BOA is shown in soil. A number of other APO related transformation products were detected and provisionally characterized. The formation of APO, which is a much more biologically active compound than BOA, and the concurrent formation of a number of other APO-related metabolites in soil underline the importance of performing transformation studies as part of the evaluation of the effect of allelochemicals on weeds and soil-borne diseases.     

Packaging waste measurement—A key element in digital's total quality program

Measurement of packaging waste is a key element of the Total Quality Management program at Digital Equipment Corporation. This case study shows how the company uses measurement techniques to set priorities for which areas of packaging waste should be addressed first and to track improvements over time. To date, an 1,800-ton annual reduction in packaging waste has been achieved, with associated annual savings of $2.7 million.     

The misleading of public participation in environmental assessment – exploring four infrastructure cases in Denmark

The article analyses the recent development of public participation in environmental assessment and indicates some unfortunate and unintended results. A number of Danish cases show how the tools involved are employed for a kind of ‘acceptance planning’, instead of actual environmental protection, and that the legitimacy which public inclusion was supposed to bring to environmental assessment has instead been replaced by considerations of legality, which frees entrepreneurs and authorities from including real environmental considerations in their planning. Thus, the undesirable handling of public participation that the article analyses is not only due to the actual difficulties of practising inclusion and the indisputable complexity of the environmental issues but also to a very large extent due to considerations of economic efficiency and an unwillingness among investors – public as well as private – to take account of environmental consequences as a long-term issue. The article ends with a range of recommendations for securing public inclusion in matters of environmental assessment through independent public initiatives or institutions that do not answer to authorities and entrepreneurs.     

Effects of chlorination on the adhesion strength and deflocculation of activated sludge flocs.

A side effect of the application of chlorine for controlling filamentous bulking is deflocculation of floc-forming bacteria, which may cause unacceptable effluent deterioration depending on dosing. It was assumed that chlorine may adversely affect the adhesion ability of floc bacteria, promoting their erosion in shear flow. The effect of chlorination on the strength of activated sludge flocs was investigated. The adhesion-erosion (AE) model developed by Mikkelsen and Keiding was used to interpret results from deflocculation tests with varying shear and solids concentration. The AE model yields the adhesion enthalpy (deltaHG/R) of cells in sludge flocs and parameters from the model were used to quantify the sludge in terms of floc strength. Two activated sludges with different initial characteristics were studied. The resulting model parameters showed that the AE model was suitable for quantifying the bond energy of particles to the activated sludge exposed to chlorine. For one activated sludge, adhesion of cells was largely unaffected by the applied chlorine doses. A second sludge showed reduced adhesion strength with chlorine, leading to increasing deflocculation. The simple batch test and AE model proved valuable for assessing the effect of chlorination on the flocs in activated sludge. By use of these procedures, it is possible to determine acceptable chlorine dosing to avoid excessive deflocculation and effluent deterioration.     

Removal of cyanide by woody plants

Hydrogen cyanide is a high volume production chemical that causes severe environmental problems. The toxicity of potassium cyanide (KCN) to basket willow trees (Salix viminalis) was tested. In aqueous solution, 2 mg CN l(-1) as KCN depressed the transpiration after 72 h about 50%. Trees exposed to 0.4 mg CN l(-1) in aqueous solution showed initially a depression of transpiration, but recovered. Doses of 8 and 20 mg CN l(-1) in aqueous solution were quickly mortal to the trees. At the end of the test, almost all cyanide had disappeared from the solutions. Levels of cyanide in plants were related to the toxicity, with no elevated levels of cyanide in plants exposed to 0.4 mg CN l(-1). Willows grown in sand survived 423.5 h irrigation with 20 mg CN l(-1). Willows grown in sand irrigated with 50 mg CN l(-1) died within a few days. The roots of the surviving willows were able to consume about 10 mg CN kg fresh weight(-1)h(-1). Vascular plants possess the enzymes beta-cyanoalanine synthase and beta-cyanoalanine hydrolase, which convert free cyanide to the amino acid asparagine. The in vivo capacity of woody plants (willow, poplar, elder, rose, birch) to remove cyanide was evaluated. Tests were performed with detached leaves and roots in KCN solutions of different concentrations. The highest removal capacity was obtained for basket willow hybrids (Salix viminalis x schwerinii). The Michaelis-Menten kinetics was determined. Realistic values of the half-saturation constant, K(M), were between 0.6 and 1.7 mg CN l(-1); the maximum metabolic capacity, v(max), was around 9.3 mg CN kg fresh weight(-1)h(-1). The removal of cyanide by plants might be useful in phytoremediation and treatment of wastewater from gold mining.     

Mantle buffering of the early oceans

Archean calcites and dolomites, if compared to their Phanerozoic counterparts, are enriched in Sr²⁺, Ba²⁺, Mn²⁺, Fe²⁺, depleted in ¹⁸O, (Na⁺), and contain mantle-like ⁸⁷Sr/⁸⁶Sr and, in associated S phases, mantle-like ³⁴S/³²S. This may be a consequence of massive seawater pumping through, and equilibration with, the coeval basaltic oceanic crust. The exponential decline of oceanic geothermal gradient in the course of terrestrial evolution led to a waning of this “mantle” flux and to the enhancement of the continental river discharge as the controlling factor of seawater composition; the major transition occurring probably during the late Archean — early Proterozoic time interval. Such evolution is consistent with the observed tectonic, sedimentological, geochemical and metallogenic secular patterns and may also provide an alternative, or complementary, inorganic explanation for the development of the post-Archean oxygenic atmosphere.