Microbial degradation pathways of the herbicide dichlobenil in soils with different history of dichlobenil-exposure

This is the first detailed study of metabolite production during degradation of the herbicide 2,6-dichlorobenzonitrile (dichlobenil). Degradation of dichlobenil and three potential metabolites: 2,6-dichlorobenzamide (BAM), 2,6-dichlorobenzoic acid (2,6-DCBA) and ortho-chlorobenzamide (OBAM) was studied in soils either previously exposed or not exposed to dichlobenil using a newly developed HPLC method. Dichlobenil was degraded in all four soils; BAM and 2,6-DCBA were only degraded in soils previously exposed to dichlobenil (100% within 35-56 days and 85-100% in 56 days, respectively), and OBAM in all four soils (25-33% removal in 48 days). BAM produced from dichlobenil was either hydrolyzed to 2,6-DCBA or dechlorinated to OBAM, which was further hydrolyzed to ortho-chlorobenzoic acid. BAM was rapidly mineralized in previously exposed soils only. All potential metabolites and the finding that BAM was a dead-end metabolite of dichlobenil in soils not previously exposed to dichlobenil needs to be included in risk assessments of the use of dichlobenil.     

Remediation of heavy metal polluted sediment by suspension and solid-bed leaching: estimate of metal removal efficiency

Remediation of heavy metal polluted sediment by extracting the metals with sulfuric acid can be performed as follows: abiotic suspension leaching, microbial suspension leaching, abiotic solid-bed leaching, and microbial solid-bed leaching. Abiotic leaching means that the acid is directly added, while microbial leaching means that the acid is generated from sulfur by microbes (bioleaching). These four principles were compared to each other with special emphasis on the effectiveness of metal solubilization and metal removal by subsequent washing. Abiotic suspension leaching was fastest, but suspending the solids exhibits some disadvantages (low solid content, costly reactors, permanent input of energy, high water consumption, special equipment required for solid separation, large amounts of waste water, sediment properties hinder reuse), which prevent suspension leaching in practice. Abiotic solid-bed leaching implies the supply of acid by percolating water which proceeds slowly due to a limited bed permeability. Microbial solid-bed leaching means the generation of acid within the bed and has been proven to be the only principle applicable to practice. Metal removal from leached sediment requires washing with water. Washing of solid beds was much more effective than washing of suspended sediment. The kinetics of metal removal from solid beds 0.3, 0.6 or 1.2m in height were similar; when using a percolation flow of 20lm(-2)h(-1), the removal of 98% of the mobile metals lasted 57-61h and required 8.5, 4.2 or 2.3lkg(-1) water. This means, the higher the solid bed, the lower the sediment-mass-specific demand for time and water.     

Concentrations and specific loads of glyphosate, diuron, atrazine, nonylphenol and metabolites thereof in French urban sewage sludge

Indirect soil pollution by heavy metals and organics may occur when sewage sludge is used as fertilizer. It is essential to define the nature and amounts of pollutants contained in sewage sludge in order to assess environmental risk. Here, we present results from a one-year monitoring of herbicides (glyphosate, diuron and atrazine) and their major degradates in sewage sludge sampled from three wastewater treatment plants and one composting unit in the vicinity of Versailles, France. The concentrations of these compounds were determined, as well as these of the surfactant nonylphenol. We demonstrated the presence of glyphosate and aminomethylphosphonic acid at the mg kg(-1) (dry matter) level in all samples. Diuron was detected at the microg kg(-1) (d.m.) level, whereas its degradate and triazine compounds were below the limits of quantification. Nonylphenol amounts were higher than the future European limit value of 50 mg kg(-1) (d.m.).     

Natural Organic Matter Differently Modulates Growth of Two Closely Related Coccal Green Algal Species (6 pp)

Background

and Aim. Humic substances (HS) comprise the majority of dead and living organic carbon, including organisms. In the environment, they are considered to be chemically inert or at least refractory. Recent papers, however, show that HS (including natural organic matter – NOM, isolated by reverse osmosis) are natural chemicals which interact with aquatic organisms. They are taken up and cause a variety of stress defense reactions which are well known from man-made chemicals. These reactions include chaperon activation, induction and modulation of biotransformation enzymes, or induction of antioxidant defense enzymes. One specific reaction with freshwater plants is the reduction of photosynthetic oxygen release. In this contribution, we compare the susceptibilities (cell yield) of two closely related coccal green algae, Monoraphidium convolutum and M. minutum, towards various NOM isolates.

Methods

Cultures of M. convolutum and M. minutum were obtained from the algal collection of the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, and from the Culture Collection of Algae, Göttingen, and maintained in a common medium. The cultures were non-axenic. The algae were exposed to 5 mg L-1 DOC of each humic material, an environmentally realistic concentration. Cell numbers were counted microscopically in Neugebauer cuvettes in 5 replicates on days 1, 4, 7, 10, 14, and 21.

Results and Discussion

Almost all NOM isolates modulated the growth of the algae. Only the NOM of a Norwegian raised peat bog lake did not reveal any significant effect with M. convolutum. In general, the results with two algal species are by no means uniform. For instance, Suwannee River NOM causes a decrease in cell density with M. minutum, but temporarily stimulates the growth of M. convolutum. The opposite applies to Aurevann NOM: Growth increase in M. minutum, but a bi-phasic response in M. convolutum. Different responses of both Monoraphidium species must be attributed to intrinsic factors of the algae rather than only to chemical features of the exposed materials, because the exposures were identical with both algal species. The reduction in growth yields can be explained as a herbicide-like mode of action that affects the photosystem II most prevalently. The growth promoting effect remains somewhat obscure. It may be due to (1) an increase in bioavailability of some trace nutrients in the presence of HS, (2) the release of some growth promoting substances by microbial or photochemical processing of the humic materials, and (3) a hormetic effect upon the exposure of HS. Hormesis means stimulation of organisms or metabolic activities when exposed to noxes in low concentrations. However, it is still open to discussion why the growth promotion only applies to one or the other, but not simultaneously to both Monoraphidium species.

Conclusion

and Perspectives. Exposure of the closely related coccal green algal species to humic material changes their growth characteristics. Since the reactions are not consistent within the two species and the various humic materials, it seems that the less sensitive species is favored by HS exposure. The environmental relevance, however, is subject to future studies.     

ESPR´s Total Environment

Environmental Science and Pollution Research -     

Shoot growth of mature Fagus sylvatica and Picea abies in relation to ozone

Epidemiological analysis of sequential growth data may be a tool in assessing ozone sensitivity of mature trees. Annual shoot growth of mature Fagus sylvatica in 83 Swiss permanent forest observation plots and of Picea abies in 61 plots was evaluated for 11 and 8 consecutive years, respectively, using branches harvested every 4 years. The data were assessed as annual deviation from average growth and related to fructification, ozone, meteorological parameters, and modelled soil water content using a mixed linear model. In beech, a significant association between ozone and shoot growth was observed which corresponded to a 7.4% growth reduction between 0 and 10 ppm h AOT40 (accumulated ozone over threshold 40). This is in the same order of magnitude as the response observed in experiments with seedlings. No interaction was found between ozone and drought parameters. In Norway spruce, shoot growth was neither associated with ozone nor with drought.     

Absorption cross-sections of atmospheric constituents: NO2, O2, and H2O

Absorption spectroscopy, which is widely used for concentration measurements of tropospheric and stratospheric compounds, requires precise values of the absorption cross-sections of the measured species. NO₂, O₂ and its collision-induced absorption spectrum, and H₂O absorption cross-sections have been measured at temperature and pressure conditions prevailing in the Earth’s atmosphere. Corrections to the generally accepted analysis procedures used to resolve the convolution problem are also proposed.     

A Decision Support Framework for Environmental Planning in Developing Countries

This paper presents a decision support framework for environmental planning in developing countries. The interest in protecting the natural environment from pollution gained increased importance in the 1990s with a push by world communities for sustainable development. Developing countries as well as the industrialized nations are expected to cut down on pollution and control the use of non-renewable natural resources. Although the concept of sustainable development sounds plausible, it is difficult to implement in many countries due to their conflicting goals. The world-wide targets on emissions, use of fossil fuels, reduction in water and atmospheric pollution require the participation of every nation. These goals are not easily achievable by some of the poorer developing countries partly because of their economic dependence on natural resources and partly because of their inability to afford more modern and efficient technologies. Thus, environmental planning goals are often in conflict with the development,social and economic needs of a country. In this paper, we develop a decision support framework that utilizes multicriteria and optimization models to address environmental planning problems. This framework is based on identifying the priorities of conflicting goals by working through and reducing the conflicts. A strategic planning framework is introduced into the decision support system since national planning is a strategic issue and these goals can only be achieved by adopting a systemic view.     

Mating expenditures reduced via female sex pheromone modulation in the primitively eusocial halictine bee, Lasioglossum (Evylaeus) malachurum (Hymenoptera: Halictidae)

The present paper reports on behavioral experiments and gas chromatographic analysis of chemical communication in the mating biology of the primitively eusocial sweat bee Lasioglossum (Evylaeus) malachurum. In a dual-choice experiment, a female made odorless was significantly less attractive than an untreated one. Attraction in L. (Evylaeus) malachurum is therefore mediated by a female-produced sex pheromone. Further bioassays showed that unmated gynes are more attractive to males than mated ones. Males are able to differentiate between the two groups of females as little as 3 h after mating. Biotests with different samples obtained from attractive gynes showed surface extracts to be most attractive. Behavioral tests with synthetic copies of the compounds identified as cuticular constituents of virgin gynes were highly attractive to males; the volatile bouquets consisting of n-alkanes, n-alkenes and iso- pentenyl esters of unsaturated fatty acids were the most attractive samples. Isopentenyl esters of unsaturated fatty acids were the key compounds in inducing male inspections as well as stimulating pounces and copulatory attempts. Virgin and nesting gynes differed clearly in the relative and absolute amounts of the volatiles on the cuticle. The total amount of volatiles was significantly higher in virgin gynes and decreased in breeding queens. Hydrocarbons were the dominant group of compounds in both groups of females. The relative amounts of the wax-type ester, hexadecyl oleate, iso- pentenyl esters, and a hitherto unidentified steroid were higher in attractive virgin gynes, while the relative proportions of hydrocarbons and lactones dominated in nesting queens. The site of sex pheromone production in attractive young L. (Evylaeus) malachurum gynes remains unknown. Head glands or Dufour's gland secretions may be involved. Another possible source of the `active principle' found among the cuticular lipids could be glandular cells of the epidermis. The significance of modulation of female sex pheromone composition is discussed in terms of a reduction in mating expenditures. Received: 30 April 1998 / Accepted after revision: 24 July 1998     

Verteilungskoeffizienten chlorierter Kohlenwasserstoffe zwischen Muskulatur und Leber bei Fischen

Measured partition coefficients (KL_M/L) related to lipid-concentrations between the muscle (C_ML) and liver (C_LL) tissue of two fish species (Abramis brama, Zoarces viviparus) exhibit nominal values of unity according the relationship KL_M/L=C_ML/C_LL=1 for persistent compounds such as highly chlorinated PCB and values above one for degradable compounds for example chlorinated cyclohexanes or DDT. The corresponding theory is presented. The relationship holds for samples for single fish as well as for pooled samples.