Spatio-temporal distribution of organic and inorganic pollutants from Lake Geneva (Switzerland) reveals strong interacting effects of sewage treatment plant and eutrophication on microbial abundance

Variation with depth and time of organic matter (carbon, nitrogen, phosphorus), inorganic pollutant (mercury), as well as bacterial abundance and activity, were investigated for the first time in sediment profiles of different parts of Lake Geneva (Switzerland) over the last decades. The highest organic contents (about 32%), mercury concentration (27 mg kg⁻¹), bacterial abundance (in order of 9 × 10⁹ cell g⁻¹ dry sediment), and bacterial activity (1299 Relative Light Units (RLU)) were found in the highly polluted sediments contaminated by the waste water treatment plant (WWTP) discharge, which deposited during the period of cultural eutrophication. Such data, which contrast with the other sampled sites from deeper and more remote parts of the lake, prove that the organic matter and nutrients released from the municipal WWTP have considerable effects on bacterial abundance and activities in freshwater sediments. In fact, the relatively unpolluted deepwater sites and the coastal polluted site show large synchronous increases in bacterial densities linked to the anoxic conditions in the 1970s (lake eutrophication caused by external nutrient input) that subsequently increased the nutrient loading fluxes. These results show that the microbial activities response to natural or human-induced changing limnological conditions (e.g., nutrient supply, oxygen availability, redox conditions) constitutes a threat to the security of water resources, which in turn poses concerns for the world’s freshwater resources in the context of global warming and the degradation of water quality (oxygen depletion in the bottom water due to reduced deep waters mixing). Moreover, the accumulation of inorganic pollutants such as high mercury (methyl-mercury) concentration may represent a significant source of toxicity for sediment dwelling organisms.     

Bromination of 2-methoxydiphenyl ether to an average of tetrabrominated 2-methoxydiphenyl ethers

Brominated 2-phenoxyanisoles (2-methoxydiphenyl ethers, 2-MeO-BDEs) are a class of halogenated natural products, produced by algae and sponges. Especially two tetrabrominated isomers, i.e. 2′-MeO-BDE 68 (BC-2) and 6-MeO-BDE 47 (BC-3), have also been frequently determined in environmental and food samples. In addition, 2-MeO-BDEs are under discussion as metabolites of polybrominated diphenyl ethers (PBDEs). In this study, we synthesized the backbone 2-methoxydiphenyl ether and brominated it to an average degree of four bromine substituents. The reaction mixture only contained one major product (∼90%) along with three further MeO-BDEs and ∼5% hydroxylated BDEs. In all likelihood, the HO-BDEs were formed in a side reaction by cleavage of the methoxy group. The major MeO-BDE was identified as 6′-methoxy-2,3′,4,4′-tetrabromodiphenyl ether (6′-MeO-BDE-66). The HO-BDEs were separated by KOH/n-hexane partitioning, and the resulting 2-MeO-BDEs were fractionated by means of high-speed counter-current chromatography (HSCCC). Due to the excellent enrichment facilities of HSCCC, some 15 MeO-BDEs, mainly present at traces only, could be detected in 26 fractions, and eight of them could be characterized by nuclear magnetic resonance spectroscopy (NMR). Only two of the compounds - 2′-MeO-BDE 68 and 6-MeO-BDE 123 - had been characterized as natural products while the prominent halogenated natural product 6-MeO-BDE 47 was not detected at all in the reaction product. The “non-natural” 2-MeO-BDEs may be useful internal standards in trace analysis.     

Occurrence of polybrominated diphenyl ethers (PBDEs) in brown trout bile and liver from Swiss rivers

The ranges of total polybrominated diphenyl ethers (PBDEs) in fish from four Swiss rivers were 0.8-240 ng/g in the bile and 16-7400 ng/g lipid in the liver. PBDE concentrations varied within each river and among the various rivers. Female fish tended to have higher concentrations in the liver, while the male fish had higher concentrations in the bile. From the resulting PBDE concentrations in fish it could not be infered that these contaminants contribute to the causes of the observed fish catch decline in Swiss rivers.     

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.     

Multicompartmental fate of persistent substances

Background, Aim and Scope Modelling of the fate of environmental chemicals can be done by relatively simple multi-media box models or using complex atmospheric transport models. It was the aim of this work to compare the results obtained for both types of models using a small set of non-ionic and non-polar or moderately polar organic chemicals, known to be distributed over long distances. Materials and Methods Predictions of multimedia exposure models of different types, namely three multimedia mass-balance box models (MBMs), two in the steady state and one in the non-steady state mode, and one non-steady state multicompartment chemistry-atmospheric transport model (MCTM), are compared for the first time. The models used are SimpleBox, Chemrange, the MPI-MBM and the MPI-MCTM. The target parameters addressed are compartmental distributions (i.e. mass fractions in the compartments), overall environmental residence time (i.e. overall persistence and eventually including other final sinks, such as loss to the deep sea) and a measure for the long-range transport potential. These are derived for atrazine, benz-[a]-pyrene, DDT, α and γ-hexachlorocyclohexane, methyl parathion and various modes of substance entry into the model world. Results and Discussion Compartmental distributions in steady state were compared. Steady state needed 2–10 years to be established in the MCTM. The highest fraction of the substances in air is predicted by the MCTM. Accordingly, the other models predict longer substance persistence in most cases. The results suggest that temperature affects the compartmental distribution more in the box models, while it is only one among many climate factors acting in the transport model. The representation of final sinks in the models, e.g. burial in the sediment, is key for model-based compartmental distribution and persistence predictions. There is a tendency of MBMs to overestimate substance sinks in air and to underestimate atmospheric transport velocity as a consequence of the neglection of the temporal and spatial variabilities of these parameters. Therefore, the long-range transport potential in air derived from MCTM simulations exceeds the one from Chemrange in most cases and least for substances which undergo slow degradation in air. Conclusions and Perspectives MBMs should be improved such as to ascertain that the significance of the atmosphere for the multicompartmental cycling is not systematically underestimated. Both types of models should be improved such as to cover degradation in air in the particle-bound state and transport via ocean currents. A detailed understanding of the deviations observed in this work and elsewhere should be gained and multimedia fate box models could then be ‘tuned in’ to match better the results of comprehensive multicompartmental transport models. ESS-Submission Editor: Prof. Dr. Michael Matthies (matthies@uos.de)     

Einschätzung der Konzentrationsprofile polyzyklischer aromatischer Kohlenwasserstoffe (PAK) in Böden des Biosphärenreservates Spreewald

To work out background values, the information of concentration profiles of PAHs in soils of uncontaminated territories is indispensable. This investigation shows PAH concentrations of different soil samples like agricultural soils, grassland, forest and litter from the biosphere reserve in Spreewald, Germany. The mean values of the soil samples are about 460 μg Σ-PAK/kg d.m. A top value of 7.2 mg Σ-PAK/kg d.m. shows a sample of a flooded grassland area. The relation of the concentrations in the litter, forest, grassland and agricultural soil samples is about 5∶3∶2∶1. Compared to the other samples, the litter samples contain a higher amount of low molecular PAHs. Increasing distance to the former power plants Lübbenau and Vetschau (brown coal) lead to decreasing PAH contents in the soil samples of forests from 2190.9 after 4 km to 294.8 Σ-PAK/kg d.m. after 16 km. In comparison to results obtained in Nordrhein-Westfalen and Bayern, the PAH measurements indicate Spreewald to be an uncontaminated and rural area.     

Ants as Indicators of Exposure to Environmental Stressors in North American Desert Grasslands

The relative abundance of ant species was measured by pit-fall trapping at 44 sites in southern New Mexico and southeastern Arizona, U.S.A.. Sites were selected for study based on documentation of a history of disturbance or protection from disturbance, exposure to varying intensities of livestock grazing, dominance by an exotic species of plant and vegetation change resulting from disturbance or restoration efforts. Ant community composition, relative abundances of species, and species richness were the same on disturbed and undisturbed sites. None of the metrics based on hypothesized responses of ants to disturbance clearly distinguished between disturbed and undisturbed sites. Ant communities on sites where restoration efforts have resulted in distinct differences in vegetative cover and composition were similar to the ant communities on degraded unrehabilitated sites on the same soil type. Ant communities in riparian cottonwood gallery forests in Arizona and New Mexico were similar but differed from the assemblages in exotic salt cedar and native ash riparian woodlands. Ant species exhibited remarkable resistance to human-induced disturbances in these rangeland areas. In grasslands dominated by the South African grass, Eragrostis lehmanniana Nees, large seed harvesting ants, Pogonomyrmex spp., were greatly reduced in abundance compared to native grasslands. Other ant metrics were not different in E. lehmanniana grasslands and native grasslands. We conclude that ants cannot be used as indicators of exposure to stress, ecosystem health or of rehabilitation success on rangeland ecosystems. Ants are also not useful indicators of faunal biodiversity in rangeland ecosystems.     

Zur Problematik der Anwendung von Hintergrundwerten beim Vollzug des Bodenschutzrechts

The knowledge about background levels of heavy metals in soils is essential for the use of the precautionary values for heavy metals as provided by the German Soil-Protection-Act. In the northeast of Bavaria the 90th percentiles in the back-ground levels of heavy metals in the soil exceed the precautionary values in many cases. Background levels were determined separately for soils of different parent materials of rocks, soil horizons and land use (agricultural or forest soils), with the parent material of rock having the strongest influence on the content of heavy metals in different soils. Precautionary values are highly exceeded by chrome and nickel in basic and ultrabasic rocks. High variability of heavy metal contents was found even in soils of the same parent material (C-horizons), which is due to the natural geochemical variability of rocks and the mixing of different parent materials during the Pleistocene. For an effective use of the German Soil-Protection-Order, areas must be defined where the probability is high that the 90th percentiles of the background levels of heavy metals exceed the precautionary values. It has to be determined, how the risk of mobilisation of heavy metals can be estimated within these areas and what has to be done if heavy metal contents in soils exceed not only the precautionary values but also the background levels.