Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 2003"
TL;DR: The second-order rate constants for oxidation by ozone vary over 10 orders of magnitude, between o 0.1 M 1 s 1 s -1 and about 7 − 10 9 M 1 S -1 s - 1 s − 1 as discussed by the authors.
2,078 citations
TL;DR: It could be shown that the second-order rate constants determined in pure aqueous solution could be applied to predict the behavior of pharmaceuticals dissolved in natural waters.
Abstract: This study investigates the oxidation of pharmaceuticals during conventional ozonation and advanced oxidation processes (AOPs) applied in drinking water treatment. In a first step, second-order rate constants for the reactions of selected pharmaceuticals with ozone (k(O3)) and OH radicals (k(OH)) were determined in bench-scale experiments (in brackets apparent k(O3) at pH 7 and T = 20 degrees C): bezafibrate (590 +/- 50 M(-1) s(-1)), carbamazepine (approximately 3 x 10(5) M(-1) s(-1)), diazepam (0.75 +/- 0.15 M(-1) s(-1)), diclofenac (approximately 1 x 10(6) M(-1) s(-1)), 17alpha-ethinylestradiol (approximately 3 x 10(6) M(-1) s(-1)), ibuprofen (9.6 +/- 1.0 M(-1) s(-1)), iopromide ( 5 x 10(4) M(-1) s(-1), indicating that these compounds are completely transformed during ozonation processes. Values for k(OH) ranged from 3.3 to 9.8 x 10(9) M(-1) s(-1). Compared to other important micropollutants such as MTBE and atrazine, the selected pharmaceuticals reacted about two to three times faster with OH radicals. In the second part of the study, oxidation kinetics of the selected pharmaceuticals were investigated in ozonation experiments performed in different natural waters. It could be shown that the second-order rate constants determined in pure aqueous solution could be applied to predict the behavior of pharmaceuticals dissolved in natural waters. Overall it can be concluded that ozonation and AOPs are promising processes for an efficient removal of pharmaceuticals in drinking waters.
1,483 citations
TL;DR: In this paper, it was shown that ozone is an excellent disinfectant and can even be used to inactivate microorganisms such as protozoa which are very resistant to conventional disinfectants.
1,161 citations
TL;DR: The relative importance in terms of loads was carbamazepine, followed by diclofenac, naproxen, ibuprofen, clofibric acid, and ketoprofen; an overall removal rate was estimated in surface waters, under real-world conditions (in a lake), using field measurements and modeling.
Abstract: Although various single-concentration measurements of pharmaceuticals are available in the literature, detailed information on the variation over time of the concentration and the load in wastewater effluents and rivers and on the fate of these compounds in the aquatic environment are lacking. We measured the concentrations of six pharmaceuticals, carbamazepine, clofibric acid, diclofenac, ibuprofen, ketoprofen, and naproxen, in the effluents of three wastewater treatment plants (WWTPs), in two rivers and in the water column of Lake Greifensee (Switzerland) over a time period of three months. In WWTP effluents, the concentrations reached 0.95 μg/L for carbamazepine, 0.06 μg/L for clofibric acid, 0.99 μg/L for diclofenac, 1.3 μg/L for ibuprofen, 0.18 μg/L for ketoprofen, and 2.6 μg/L for naproxen. The relative importance in terms of loads was carbamazepine, followed by diclofenac, naproxen, ibuprofen, clofibric acid, and ketoprofen. An overall removal rate of all these pharmaceuticals was estimated in surf...
923 citations
TL;DR: The observation that As( III) is oxidized in parallel to the oxidation of Fe(II) by O2 and by H2O2 and that the As(III) oxidation is not inhibited by *OH-radical scavengers at neutral pH is significant for the understanding of arsenic redox reactions in the environment and in arsenic removal processes as well as for theUnderstanding of Fenton reactions in general.
Abstract: The oxidation kinetics of As(III) with natural and technical oxidants is still not well understood, despite its importance in understanding the behavior of arsenic in the environment and in arsenic removal procedures. We have studied the oxidation of 6.6 μM As(III) by dissolved oxygen and hydrogen peroxide in the presence of Fe(II,III) at pH 3.5−7.5, on a time scale of hours. As(III) was not measurably oxidized by O2, 20−100 μM H2O2, dissolved Fe(III), or iron(III) (hydr)oxides as single oxidants, respectively. In contrast, As(III) was partially or completely oxidized in parallel to the oxidation of 20−90 μM Fe(II) by oxygen and by 20 μM H2O2 in aerated solutions. Addition of 2-propanol as an •OH-radical scavenger quenched the As(III) oxidation at low pH but had little effect at neutral pH. High bicarbonate concentrations (100 mM) lead to increased oxidation of As(III). On the basis of these results, a reaction scheme is proposed in which H2O2 and Fe(II) form •OH radicals at low pH but a different oxidant...
736 citations
TL;DR: Sewage sludge is suggested as the main reservoir of FQ residues and the importance of sludge management strategies to determine whether most of the human-excreted FQs enter the environment is outlined.
Abstract: The behavior of fluoroquinolone antibacterial agents (FQs) during mechanical−biological wastewater treatment was studied by mass flow analysis. In addition, the fate of FQs in agricultural soils after sludge application was investigated. Concentrations of FQs in filtered wastewater (raw sewage, primary, secondary, and tertiary effluents) were determined using solid-phase extraction with mixed phase cation exchange disk cartridges and reversed-phase liquid chromatography with fluorescence detection. FQs in suspended solids, sewage sludge (raw, excess, and anaerobically digested sludge), and sludge-treated soils were determined as described for the aqueous samples but preceded by accelerated solvent extraction. Wastewater treatment resulted in a reduction of the FQ mass flow of 88−92%, mainly due to sorption on sewage sludge. A sludge-wastewater partition coefficient (log Kd ∼ 4) was calculated in the activated sludge reactors with a hydraulic residence time of about 8 h. No significant removal of FQs occur...
680 citations
TL;DR: The main outcome of the study was that a common municipal STP with an activated sludge system for nitrification and denitrification including sludge recirculation can appreciably eliminate natural and synthetic estrogens.
Abstract: The fate of the highly potent endocrine disrupters estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) was investigated in mechanical and biological sewage treatment as well as in sewage-sludge treatment at a municipal German sewage treatment plant (STP). The main outcome of the study was that a common municipal STP with an activated sludge system for nitrification and denitrification including sludge recirculation can appreciably eliminate natural and synthetic estrogens. As a consequence, the endocrine effects of biota in the receiving waters should be significantly reduced. All estrogen concentrations decreased gradually along the treatment train. In the STP effluent, the steroid estrogen concentrations were always below the quantification limit of 1 ng/L. The elimination efficiency of the natural estrogens (E1 and E2) exceeded 98%, and EE2 was reduced by more than 90%. The natural estrogens were largely degraded biologically in the denitrifying and aerated nitrifying tanks of the activate...
557 citations
TL;DR: In this article, stable-isotopic, geochemical, pollen and charcoal analyses were performed to find evidence of past regional climatic changes and human impact in the semi-arid region of eastern Anatolia, Turkey.
Abstract: Annually laminated sediments from Lake Van, spanning about 13000 varve years, were sampled for stable-isotopic, geochemical, pollen and charcoal analyses in order to find evidence of past regional climatic changes and human impact in the semi-arid region of eastern Anatolia, Turkey. The Lateglacial period was cold and dry, with steppe vegetation and saline lake water. During the Younger Dryas the lake level dropped dramatically, and the vegetation turned to a semi-desert. Geochemical and isotopic records indicate a strong increase in moisture at the onset of the Holocene, and Artemisia-chenopod steppes were partly replaced by grass steppe and pistachio scrub. A delay of about 3000 years in the expansion of deciduous oak woodlands and high steppe-fire frequencies suggest dry spring and summer weather during the early Holocene. At 8200 yr BP, a shift in the regional climate regime facilitated the transport of more moisture into the interior areas of the Taurus mountains and caused a change in the seasonal distribution of precipitation. The steppe-forests dominated by Quercus advanced and reached their maximum extention at about 6200 yr BP. All the proxy data indicate optimum climatic conditions, low water salinity and high lake level between 6200 and 4000 yr BP. After 4000 yr BP, aridity increased again and the modern climatic situation was established. Human impact in the catchment of Lake Van started at 3800 yr BP and was intensified during the last 600 years.
503 citations
TL;DR: Mass flux determinations in treated effluents and in river water in the Glatt Valley watershed showed that elimination of clarithromycin along the river stretch of 36 km is insignificant (<20%).
Abstract: An analytical method was developed for determining macrolide antibiotics in treated wastewater effluents and in ambient water based on solid-phase extraction and LC/MS analysis as well as on LC/MS/MS for structural confirmation. In wastewater treatment plants (WWTPs) macrolides are only partly eliminated and can therefore reach the aquatic environment. In treated effluents from three WWTPs in Switzerland, clarithromycin, roxithromycin, and erythromycin-H2O, the main degradation product of erythromycin, were found. The most abundant, clarithromycin, reflects the consumption pattern of macrolide antibiotics. Summer concentrations of clarithromycin varied between 57 and 330 ng/L in treated WWTP effluents. In the WWTP Kloten-Opfikon seasonal differences revealed a load two times higher in winter than in summer. The higher abundance of erythromycin-H2O in the effluent of WWTP Kloten-Opfikon can be explained by distinct consumption patterns due to the main international airport of Switzerland in the catchment area. In the Glatt River clarithromycin reached concentrations of up to 75 ng/L. Mass flux determinations in treated effluents and in river water in the Glatt Valley watershed showed that elimination of clarithromycin along the river stretch of 36 km is insignificant (<20%). Investigations in the Glatt River before and after the diversion of the largest WWTP revealed an observable decrease in clarithromycin loads.
451 citations
TL;DR: In this paper, a 52-year series of monthly temperature profiles from Lake Zurich, a large, deep (136 m), temperate lake on the Swiss Plateau, is presented.
Abstract: Strong climate-related secular trends are apparent in a 52-yr long (1947–1998) uninterrupted series of monthly temperature profiles fromLake Zurich, a large, deep (136 m), temperate lake on the Swiss Plateau. Decadal mean water temperatures have undergone a secular increase at all depths, reflecting the high degree of regional warming that occurred in the European Alpine area during the 20th century. From the 1950s to the 1990s, high warming rates (∼ 0.24 K per decade) in the uppermost 20 m of the lake (i.e., the epi/metalimnion) combined with lower warming rates (∼ 0.13 K per decade) below 20 m (i.e., in the hypolimnion), have resulted in a20% increase in thermal stability and a consequent extension of 2–3 weeksin the stratification period. In common with many other parts of the world, 20th-century climate change on the Swiss Plateau has involved a steep secular increase in daily minimum (nighttime) air temperatures, but not in daily maximum (daytime) air temperatures. With respect to both secular change and decadal-scale variability, the temporal structure of the temperature of the surface mixed layer of Lake Zurich faithfully reflects that of the regional daily minimum air temperature, but not that of the daily maximum. The processes responsible for longer-term changes in the temperature structure of the lake therefore act during the night, presumably by suppressing nighttime convective cooling of the surface mixed layer. Application of a one-box heat exchange model suggests that the observed secular changes in thermal structure are due to shifts in the nighttime rate of emission of infrared radiation from the atmosphere and in the nighttime rates of latent and sensible heat exchange at the air-water interface. The increase in hypolimnetic temperatures is mainly a result of the increased prevalence of warm winters in Europe.
401 citations
TL;DR: It is found that urease-active bacteria mainly grow in the pipes and are flushed into the collection tank and two experiments with precipitated solids from the pipes showed that precipitation sets in soon after ureolysis has started.
TL;DR: The analysis of different removal and recovery techniques for nutrients in urine shows that in many cases recovery is energetically more efficient than removal and new-production from natural resources.
TL;DR: In this paper, a reevaluation of the well-accepted management strategy of decreasing the lake internal P cycling by maintaining an aerobic hypolimnion and sediment surface is presented, and it is shown that oxygenation only results in an increased permanent benthic P burial if, because of depressed sulfide production, more ferrous phosphate and less FeS is deposited in the anoxic sediment.
Abstract: In order to improve the trophic state of Lake Sempach, a eutrophied lake in central Switzerland, its external phosphorus (P) load has been decreased and its hypolimnion has been artificially oxygenated to lower the lake-internal P recycling. Based on more than 15 yr of experience, we conclude that the reduction of the external P load resulted in a corresponding decrease of the lake's P concentration. However, contrary to initial expectations, increased hypolimnetic dissolved oxygen concentrations neither (1) reduced the P release from sediments during summer nor (2) resulted in an increased permanent P retention. These observations warrant a reevaluation of the well-accepted management strategy of decreasing the lake internal P cycling by maintaining an aerobic hypolimnion and sediment surface. We hypothesize that oxygenation only results in an increased permanent benthic P burial if, because of the depressed sulfide production, more ferrous phosphate (e.g., vivianite) and less FeS is deposited in the anoxic sediment. Hence, it is not the oxic sediment surface that directly affects the permanent redox-dependent sediment P retention but the molar ratio of the available reactive Fe(II): S 2- : PO 4 in the anoxic sediment. This ratio is driven by the settling rate and the nature of organic matter and particulate iron, as well as the supply of oxygen, nitrate, and sulfate to the sediment.
TL;DR: In this paper, the stable isotope composition (15 N and 18 O) of nitrate was measured during Summer 1999 in the anaerobic hypolimnion of eutrophic Lake Lugano (Switzerland).
TL;DR: Using selected irrigation districts in northern China as a case study, this article investigated the effectiveness of pricing-based water policies in addressing challenges facing irrigated agriculture under China's current water management institutions.
TL;DR: A water resources threshold with respect to cereal import is estimated on the basis of data for countries in Asia and Africa to see if many poor and populous countries dropping below the threshold in association with their rapid population growth and the depletion of fossil groundwater.
Abstract: Cereal import has played a crucial role in compensating local water deficit. A quantitative account of water deficit and cereal import relations therefore is of significance for predicting future food import demand and formulating corresponding national and international policies. On the basis of data for countries in Asia and Africa, we estimated a water resources threshold with respect to cereal import. Below the threshold, the demand for cereal import increases exponentially with decreasing water resources. There appeared to be a declining trend in the threshold, from 2000 m3/(capita year) in the early 1980s to 1500 m3/(capita year) by the end of the 1990s. Until recently, most countries below the threshold were oil-rich and thus were able to afford cereal import. However, the next 30 yr may see many poor and populous countries dropping below the threshold in association with their rapid population growth and the depletion of fossil groundwater. Water deficit-induced food insecurity and starvation coul...
TL;DR: The Tagliamento River as discussed by the authors has a number of attributes that have not been given due consideration in river ecology: (i) an immense corridor of more than 150 km2 that connects the land and the sea and two biomes, the Alps and the Mediterranean; (ii) unconstrained floodplain segments characterised by a dynamic mosaic of aquatic/terrestrial habitats; and (iii) a large number of vegetated islands (ca. 700).
Abstract: In NE Italy is a remarkable floodplain river that retains the dynamic nature and morphological complexity that must have characterized most Alpine rivers in the pristine stage. This river system, the Fiume Tagliamento, constitutes an invaluable resource not only as a reference site for the Alps, but as a model ecosystem for large European rivers. The Tagliamento has a number of attributes that have not been given due consideration in river ecology: (i) an immense corridor of more than 150 km2 that connects the land and the sea and two biomes, the Alps and the Mediterranean; (ii) unconstrained floodplain segments characterised by a dynamic mosaic of aquatic/terrestrial habitats; and (iii) a large number of vegetated islands (ca. 700). We believe it is critical to understand the functional roles of these endangered attributes in order to effectively engage in river conservation and management programmes. The Tagliamento River in Italy offers the rare opportunity to investigate natural processes at a scale that can be studied almost nowhere else in Europe.
TL;DR: In this paper, the authors performed in situ measurements of bottom boundary-layer turbulence and of diffusive oxygen fluxes at the sediment-water interface in a medium-sized mesotrophic lake.
Abstract: We performed combined in situ measurements of bottom boundary-layer turbulence and of diffusive oxygen fluxes at the sediment‐water interface in a medium-sized mesotrophic lake. The turbulence was driven by internal seiching with a period of 18 h. This periodic forcing, a prominent feature of enclosed water bodies, led to distinct deviations of the structure and the dynamics of the bottom boundary layer from the classical law-of-the-wall theory. A major feature was a phase lag between the current velocity and the turbulent energy dissipation of approximately 10% of the seiching period (1.5‐2 h). The oxygen flux into the sediment was controlled by the diffusive boundary layer, the thickness of which varied between 0.16 and 0.84 mm during the course of a seiching period, and was strongly affected by the periodic bottom boundary-layer turbulence. The rate of dissipation of turbulent energy in the bottom boundary layer allowed us to define the Batchelor length for dissolved oxygen, which quantifies the smallest scales of oxygen fluctuations and provides an appropriate scaling for the diffusive boundary-layer thickness and the corresponding oxygen fluxes. An analysis of the governing time scales revealed the importance of turbulence in controlling the small-scale spatial heterogeneity of the diffusive fluxes. Higher turbulence causes the diffusive boundary layer (DBL) to follow the sediment topography more smoothly, resulting in an increased area-averaged flux due to the greater effective surface area. After surface zones, the bottom boundary layer (BBL) is the second prime site for animals, plants, and microorganisms in natural waters. From a physical and geochemical point of view, the importance of the BBL is twofold. First, the BBL is a major energy sink for basin-scale currents due to bottom friction and also due to the breaking of propagating internal waves on sloping bottoms (Imberger 1998). Consequently, the level of turbulence is enhanced in the BBL compared with the interior water body. Second, the BBL controls the exchange of solutes and particles between water and sediment. The sediment surface is usually an enormous sink of oxygen due to the processes caused by the decomposition of organic matter. Furthermore, the redissolution and subsequent vertical transport of ions and other solutes supply primary producers with nutrients and affect the stability of the water column by chemical (salinity) strat
TL;DR: A computer model for estimating the precipitation potential (PP) in urine-collecting systems determined that only a small fraction of urea has to be hydrolysed for reaching 95% of the maximum PP, and that urine dilution diminishes the risk of blockages, since the mass concentration of precipitates decreases with the volume of flushing water.
TL;DR: The results together with the fact that reduced HA could play a significant role as reductants in the reductive transformation of subsurface contaminants and that such a process could potentially be enhanced at contaminated sites by addition of reducible natural organic matter are suggested.
Abstract: Humic acids (HA) are ubiquitous redox-active compounds of natural aquatic and soil systems. Here we studied the potential of HA as reductants for chlorinated aliphatic pollutants. To avoid artifacts potentially involved when studying chemically reduced HA, we prepared electrochemi cally reduced soil, aquatic and synthetic HA, and anthrahydroquinone-2,6-disulfonic acid (AHQDS), a model compound for hydroquinone moieties in HA. Both reduced HA and AHQDS reduced hexachloroethane (HCE) at appreciable rates. Some reduction of HCE by HA, however, occurred even before electrochemical reduction of the humic acids. This indicates that a small fraction of reduced moieties in HA persists at oxic conditions for some time. The initial reaction followed pseudo-first-order reaction kinetics, and tetrachloroethylene was the only halogenated product. The relatively small variations in carbon-normalized rate constants, kDOC, found indicate that despite inherent variations in concentration, accessibility, and reactivity of redox-active groups in HA of various origins their overall dechlorination activity is fairly constant. However, HCE transformation rate constants and reducing capacities of different HA did not correlate. Rate constants normalized to both carbon content and reducing capacity of HA clearly indicate that reduced functional groups in different HA exhibit different reactivities. Our results together with the fact that reduced HA can be formed by a variety of microbiological and chemical processes suggest that HA could play a significant role as reductants in the reductive transformation of subsurface contaminants and that such a process could potentially be enhanced at contaminated sites by addition of reducible natural organic matter.
TL;DR: The results indicate that the catalyzed oxidation of As(III) by H2O2 on the surface of iron (hydr)oxides might be a relevant reaction pathway in environmental systems such as surface waters, as well as in engineered systems for As removal from water.
Abstract: Knowledge of arsenic redox kinetics is crucial for understanding the impact and fate of As in the environment and for optimizing As removal from drinking water. Rapid oxidation of As(III) adsorbed to ferrihydrite (FH) in the presence of hydrogen peroxide (H2O2) might be expected for two reasons. First, the adsorbed As(III) is assumed to be oxidized more readily than the undissociated species in solution. Second, catalyzed decomposition of H2O2 on the FH surface might also lead to As(III) oxidation. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to monitor the oxidation of adsorbed As(III) on the FH surface in situ. No As(III) oxidation within minutes to hours was observed prior to H2O2 addition. Initial pseudo-first-order oxidation rate coefficients for adsorbed As(III), determined at H2O2 concentrations between 8.4 μM and 8.4 mM and pH values from 4 to 8, increased with the H2O2 concentration according to the equation log kox (min-1) = 0.17 + 0.50 log [H2O2] (mol/...
TL;DR: It is proposed that CsgD stimulates biofilm formation in E. coli by contemporary activation of adhesion positive determinants (the curli-encoding csg operons and the product of the yaiC gene) and repression of negative effectors such as yagS and pepD.
Abstract: Production of curli, extracellular structures important for biofilm formation, is positively regulated by OmpR, which constitutes with the EnvZ protein an osmolarity-sensing two-component regulatory system. The expression of curli is cryptic in most Escherichia coli laboratory strains such as MG1655, due to the lack of csgD expression. The csgD gene encodes a transcription activator of the curli-subunit-encoding csgBA operon. The ompR234 up-mutation can restore csgD expression, resulting in curli production and increased biofilm formation. In this report, it is shown that ompR234-dependent csgD expression, in addition to csgBA activation during stationary phase of growth, stimulates expression of the yaiC gene and negatively regulates at least two other genes, pepD and yagS. The promoter regions of these four genes share a conserved 11 bp sequence (CGGGKGAKNKA), necessary for csgBA and yaiC regulation by CsgD. While at both the csgBA and yaiC promoters the sequence is located upstream of the promoter elements, in both yagS and pepD it overlaps either the putative −10 sequence or the transcription start point, suggesting that CsgD can function as both an activator and a repressor. Adhesion experiments show that csgD-independent expression of both yagS and pepD from a multicopy plasmid negatively affects biofilm formation, which, in contrast, is stimulated by yaiC expression. Thus it is proposed that CsgD stimulates biofilm formation in E. coli by contemporary activation of adhesion positive determinants (the curli-encoding csg operons and the product of the yaiC gene) and repression of negative effectors such as yagS and pepD.
TL;DR: The membrane-bound tetrachloroethene reductive dehalogenase (PCE-RDase) (PceA), the terminal component of the respiratory chain of Dehalobacter restrictus, was purified 25-fold to apparent electrophoretic homogeneity and formed a coherent group of reductiveDehalogenases with almost 100% sequence identity.
Abstract: The membrane-bound tetrachloroethene reductive dehalogenase (PCE-RDase) (PceA; EC 1.97.1.8), the terminal component of the respiratory chain of Dehalobacter restrictus, was purified 25-fold to apparent electrophoretic homogeneity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a single band with an apparent molecular mass of 60 +/- 1 kDa, whereas the native molecular mass was 71 +/- 8 kDa according to size exclusion chromatography in the presence of the detergent octyl-beta-D-glucopyranoside. The monomeric enzyme contained (per mol of the 60-kDa subunit) 1.0 +/- 0.1 mol of cobalamin, 0.6 +/- 0.02 mol of cobalt, 7.1 +/- 0.6 mol of iron, and 5.8 +/- 0.5 mol of acid-labile sulfur. Purified PceA catalyzed the reductive dechlorination of tetrachloroethene and trichloroethene to cis-1,2-dichloroethene with a specific activity of 250 +/- 12 nkat/mg of protein. In addition, several chloroethanes and tetrachloromethane caused methyl viologen oxidation in the presence of PceA. The K-m values for tetrachloro.ethene, trichloroethene, and methyl viologen were 20.4 +/- 3.2, 23.7 +/- 5.2, and 47 +/- 10 muM, respectively. The PceA exhibited the highest activity at pH 8.1 and was oxygen sensitive, with a half-life of activity of 280 min upon exposure to air. Based on the almost identical N-terminal amino acid sequences of PceA of Dehalobacter restrictus, Desulfitobacterium hafniense strain TCE1 (formerly Desulfitobacterium frappieri strain TCE1), and Desulfitobacterium hafniense strain PCE-S (formerly Desulfitobacterium frappieri strain PCE-S), the pceA genes of the first two organisms were cloned and sequenced. Together with the pceA genes of Desulfitobacterium hafniense strains PCE-S and Y51, the pceA genes of Desulfitobacterium hafniense strain TCE1 and Dehalobacter restrictus form a coherent group of reductive dehalogenases with almost 100% sequence identity. Also, the pceB genes, which may code for a membrane anchor protein of PceA, and the intergenic regions of Dehalobacter restrictus and the three desultitobacteria had identical sequences. Whereas the cprB (chlorophenol reductive dehalogenase) genes of chlorophenol-dehalorespiring bacteria are always located upstream of cprA, all pceB genes known so far are located downstream of pceA. The possible consequences of this feature for the annotation of putative reductive dehalogenase genes are discussed, as are the sequence around the iron-sulfur cluster binding motifs and the type of iron-sulfur clusters of the reductive dehalogenases of Dehalobacter restrictus and Desulfitobacterium dehalogenans identified by electron paramagnetic resonance spectroscopy.
TL;DR: Genome comparisons and genetic data on integrase functioning reveal that the clc element and several other unclassified ICElands belong to a group of elements with conserved features, unique among them in carrying the genetic information for several degradation pathways, whereas the others give evidence for pathogenicity functions.
TL;DR: An overview of four natural resource management projects carried out using participatory modelling methods involving stakeholders in the co-design and social learning of management solutions using different types of participatory process structures adopted is presented.
Abstract: The need to understand what might constitute best practice in participatory methods for resource management is becoming ever more important as the requirement for a high level of participation becomes prescribed in the environmental directives of the EU and elsewhere Since there are numerous potential stakeholders who may participate, various different goals of participation and many potential participatory methods designed to achieve them, there is a need for better understanding of how the methods can be practicably applied to particular stakeholders and for what purpose As input into this process, this paper presents an overview of four natural resource management projects carried out using participatory modelling methods involving stakeholders in the co-design and social learning of management solutions From these case studies, a description is elicited of the different types of participatory process structures adopted, as well as an analysis of the influences behind the selection of stakeholders a
TL;DR: Investigation of the conditions which promote establishment of a suitable microbial community for performing nitritation when starting from regular sewage sludge found that similar reactor performance with respect to chemical parameters, the underlying community structures were different, which may have an influence on stability during perturbations.
Abstract: Partial nitrification of ammonium to nitrite under oxic conditions (nitritation) is a critical process for the effective use of alternative nitrogen removal technologies from wastewater. Here we investigated the conditions which promote establishment of a suitable microbial community for performing nitritation when starting from regular sewage sludge. Reactors were operated in duplicate under different conditions (pH, temperature, and dilution rate) and were fed with 50 mM ammonium either as synthetic medium or as sludge digester supernatant. In all cases, stable nitritation could be achieved within 10 to 20 days after inoculation. Quantitative in situ hybridization analysis with group-specific fluorescent rRNA-targeted oligonucleotides (FISH) in the different reactors showed that nitrite-oxidizing bacteria of the genus Nitrospira were only active directly after inoculation with sewage sludge (up to 4 days and detectable up to 10 days). As demonstrated by quantitative FISH and restriction fragment length polymorphism (RFLP) analyses of the amoA gene (encoding the active-site subunit of the ammonium monooxygenase), the community of ammonia-oxidizing bacteria changed within the first 15 to 20 days from a more diverse set of populations consisting of members of the Nitrosomonas communis and Nitrosomonas oligotropha sublineages and the Nitrosomonas europaea-Nitrosomonas eutropha subgroup in the inoculated sludge to a smaller subset in the reactors. Reactors operated at 30 degrees C and pH 7.5 contained reproducibly homogeneous communities dominated by one amoA RFLP type from the N. europaea-N. eutropha group. Duplicate reactors at pH 7.0 developed into diverse communities and showed transient population changes even within the ammonia oxidizer community. Reactors at pH 7.5 and 25 degrees C formed communities that were indistinguishable by the applied FISH probes but differing in amoA RFLP types. Communities in reactors fed with sludge digester supernatant exhibited a higher diversity and were constantly reinoculated with ammonium oxidizers from the supernatant. Therefore, such systems could be maintained at a higher dilution rate (0.75 day(-1) compared to 0.2 day(-1) for the synthetic wastewater reactors). Despite similar reactor performance with respect to chemical parameters, the underlying community structures were different, which may have an influence on stability during perturbations.
TL;DR: In this article, the effects of an experimental flood regime on periphyton and stream metabolism downstream of a large reservoir were investigated and the results indicated that the new flow regime increased ecosystem dynamics, but it may take several years until the autotrophic energy base becomes adapted to the new and more dynamic flow regime.
Abstract: We investigated the effects of an experimental flood regime on periphyton and stream metabolism downstream of a large reservoir Three floods took place in summer of 2000 and 2001 and two floods in summer of 2002 Residual flow in the River Spol was <25 m3s–1 The experimental floods lasted 9 to 11 hours with peak flows ranging from 12 to 55 m3s–1 Periphyton was collected in the River Spol (impact site) and in a reference stream in 1999 (pre-flood) and before and after each flood from 2000 to 2002 We measured ecosystem metabolism with the single station diel oxygen method a few days before and after floods in the River Spol Floods temporarily reduced periphyton biomass, but the disturbance impact and recovery patterns were not uniform among floods, thus resulting in high inter-annual variation in seasonal biomass patterns The average periphyton biomass in the River Spol even increased after a transient reduction in 2000 A principal component analysis indicated a persistent shift in the structure of the diatom community at the impact site The floods reduced gross primary production and to minor extent ecosystem respiration, resulting in a transient decline in the P/R ratio However, ecosystem metabolism recovered relatively fast The new flow regime increased ecosystem dynamics, but it may take several years until the autotrophic energy base becomes adapted to the new and more dynamic flow regime
TL;DR: In this paper, the authors examined the response of stream macroinvertebrates to a multiple-year experimental flood regime downstream of a large reservoir and found that the response to experimental floods occurs over a period of years rather than months, as species composition adjusts to the new and more variable habitat template.
Abstract: We examined the response of stream macroinvertebrates to a multiple-year experimental flood regime downstream of a large reservoir. Benthic samples were collected from the River Spol prior to the initial flood (1999) and at periodic intervals before and after eight floods from 2000 through 2002. Three artificial floods occurred each in 2000 and 2001, and two floods were implemented in 2002. We also sampled macroinvertebrates in an adjacent tributary (Val da l'Aqua) on the same dates as in the Spol to assess the natural temporal variability in assemblage structure. The regulated baseflow discharge in the Spol was 40 m3/s for a short period. Repeated measures ANOVA indicated that the floods significantly reduced macroinvertebrate densities in the Spol, although recovery to pre-flood densities occurred within a matter of weeks to densities found in 1999. A principal components analysis revealed that assemblage composition shifted in response to the recurring floods, first from 1999 to 2000 and then from 2000 to 2001/2. Taxa that decreased in abundance due to the floods included the Gammaridae (Gammarus fossarum) and Turbellaria (Crenobia alpina). Taxa that increased in abundance included Baetidae, Chironomidae, and Simuliidae. Some Plecoptera, Trichoptera, and Heptageniidae that were negatively impacted by the floods in 2000, subsequently increased in abundance. Our data suggest that the response of macroinvertebrates to experimental floods occurs over a period of years rather than months, as species composition adjusts to the new and more variable habitat template. Future changes are expected as additional species begin to colonize the river from adjacent sources. The results clearly show that the experimental flood regime should be maintained if resource managers wish to sustain the development of a more natural macroinvertebrate assemblage.
TL;DR: In this article, the authors investigated relative changes and age distribution of habitats in the active channel of a bar-braided and an islandbraided reach of the Tagliamento River (NE-Italy).
Abstract: Summary
1. Relative changes and age distribution of habitats were investigated in the active channel of a bar-braided and an island-braided reach of the Tagliamento River (NE-Italy). Between September 1999 and January 2002, six habitat types were delineated with a differential Global Positioning System on five dates following floods of different magnitude. Overlay maps were employed to calculate age and relative change of habitats. We established exponential decay rates (k-values) for islands and major aquatic habitats.
2. Relative changes of all aquatic habitats combined were up to 82% between survey dates in the bar-braided flood plain, with a cumulative rate of 85% over the 2.5-year period. Relative habitat changes in the island-braided flood plain were lower with a cumulative change of almost 60% during the study period. In the bar-braided flood plain significant exponential decay relationships were established for channels, alluvial channels, backwaters, and ponds.
3. Half-lives were particularly short for backwaters and ponds. In the island-braided reach, significant relationships existed for channels and alluvial channels. The half-lives of channels and alluvial channels increased with the presence of vegetated islands. Relative habitat composition within the active corridor remained almost constant, supporting the applicability of the shifting mosaic steady state model to braided floodplain ecosystems.
4. Our results indicate that under natural conditions aquatic floodplain habitats can be highly dynamic over short time-scales. Even small water level fluctuations (‘flow pulses’) can lead to major habitat changes with important consequences for the fauna and flora.
TL;DR: Methods to determine delta13C values of commonly reported groundwater contaminants in low-microgram per liter concentrations of methyl tert-butyl ether, chloroform, tetrachloromethane, chlorinated ethylenes, benzene, and toluene are developed.
Abstract: Compound-specific carbon isotope analysis (CSIA) has become an important tool in biological, archeological, and geological studies as well as in forensics, food sciences, and organic chemistry. If sensitivity could be enhanced, CSIA would further have an improved potential for environmental applications such as, for example, in situ remediation studies to assess contaminated environments, identification of pollutant degradation pathways and kinetics, distinction between degradation/formation mechanisms, or, verification of contaminant sources. With this goal in mind, we have developed methods to determine ∂13C values of commonly reported groundwater contaminants in low-microgram per liter concentrations. Several injection and preconcentration techniques were evaluated for this purpose, i.e., on-column injection, split/splitless injection, solid-phase microextraction (SPME), and purge and trap (P&T) in combination with gas chromatography−isotope ratio mass spectrometry. The ∂13C values of the target compou...