The filamentous bacteria "<em>Microthrix parvicella</em>" cause serious bulking and scumming in wastewater treatment plants (WWTP) all over the world. Decades of research did identify Microthrix as specialized lipid consumer but could not clarify the processes that allow this organism to successfully compete in activated sludge systems. In this study we developed a model based on ASM3 that describes the pronounced seasonal variations of Microthrix abundance observed in a full-scale WWTP. We hypothesize that low temperatures reduce the solubility of lipophilic substances and inhibit its uptake by non-specialized bacteria. The presented model structure and parameters successfully approximate the measured data, but it does not necessarily reflect the only and true selection mechanism for Microthrix. However, as innovation often happens through regular alternation between experimenting and mathematical modeling, the proposed model is a tool to coordinate the discussion and future research activities in order to clarify the relevant selection mechanisms favoring Microthrix in activated sludge systems.

Two innovative tracer methods for the quantification of parasitic discharge in sewers have been proposed as routine applications within the scope of the European research project APUSS (Assessing Infiltration and Exfiltration on the Performance of Urban Sewer Systems). In order to improve the accuracy of wastewater hydrograph separation compared to conventional practice, the novel approaches are using intrinsic physicochemical characteristics (stable isotopes, pollutographs) of the wastewater as a natural tracer for the differentiation of its constituting components. The article analyses the achieved state of development and demonstrates the application of the protocols with a comparative experimental study.

Reductive dechlorination of tetrachloroethene (perchloroethylene; PCE) was observed at 20°C in a fixed-bed column, filled with a mixture (3:1) of anaerobic sediment from the Rhine river and anaerobic granular sludge. In the presence of lactate (1 mM) as an electron donor, 9 υM PCE was dechlorinated to ethene. Ethene was further reduced to ethane. Mass balances demonstrated an almost complete conversion (95 to 98%), with no chlorinated compounds remaining (&lt;0.5 μg/liter). When the temperature was lowered to 10°C, an adaptation of 2 weeks was necessary to obtain the same performance as at 20°C. Dechlorination by column material to ethene, followed by a slow ethane production, could also be achieved in batch cultures. Ethane was not formed in the presence of bromoethanesulfonic acid, an inhibitor of methanogenesis. The high dechlorination rate (3.7 μmol · l^-1 · h^-1), even at low temperatures and considerable PCE concentrations, together with the absence of chlorinated end products, makes reductive dechlorination an attractive method for removal of PCE in bioremediation processes.

At present, the ergosterol and acetate-to-ergosterol techniques are generally considered to be the methods of choice to quantify fungal biomass, growth rate, and productivity under natural conditions. Both methods rely on the accurate isolation and quantification of ergosterol, a major membrane component of eumycotic fungi. Taking advantage of the solid-phase extraction (SPE) technique, we present a novel method to determine the ergosterol concentration in lipid extracts derived from plant tissues and dead organic matter colonized by fungi. In this method, a primary alkaline extract is acidified and passed through a reversed-phase (C₁₈) SPE column. The column is then washed with an alkaline methanol-water solution to eliminate interfering substances and increase pH and is thoroughly dried in air. Ergosterol is eluted with alkaline isopropanol. This eluting solvent was chosen to produce a strongly basic pH of the final extract and thus confer stability on the ergosterol molecule before high-performance liquid chromatography analysis. The recovery of ergosterol from plant tissues and the O_hf horizon of a woodland soil ranged from 85 to 98%, and the overall extraction efficiency was similar to that obtained by a conventional procedure involving liquid-liquid extraction. Potential pitfalls of ergosterol analysis by SPE include (i) insufficient acidification before sample loading on the extraction column, resulting in a poor affinity of ergosterol for the sorbent; (ii) incomplete drying of the sorbent bed before the elution step; and (iii) chemical breakdown of ergosterol after elution, which was found to be related to a low pH of the final extract and a high concentration of matrix compounds. When these pitfalls are avoided, SPE is an attractive alternative to existing methods of ergosterol analysis of environmental samples.

Members of the genus <I>Sphingomonas</I> are important catalysts for removal of polycyclic aromatic hydrocarbons (PAHs) in soil, but their activity can be affected by various stress factors. This study examines the physiological and genome-wide transcription response of the phenanthrene-degrading <I>Sphingomonas</I> sp. strain LH128 in biofilms to solute stress (invoked by 450 mM NaCl solution), either as an acute (4-h) or a chronic (3-day) exposure. The degree of membrane fatty acid saturation was increased as a response to chronic stress. Oxygen consumption in the biofilms and phenanthrene mineralization activities of biofilm cells were, however, not significantly affected after imposing either acute or chronic stress. This finding was in agreement with the transcriptomic data, since genes involved in PAH degradation were not differentially expressed in stressed conditions compared to nonstressed conditions. The transcriptomic data suggest that LH128 adapts to NaCl stress by (i) increasing the expression of genes coping with osmolytic and ionic stress such as biosynthesis of compatible solutes and regulation of ion homeostasis, (ii) increasing the expression of genes involved in general stress response, (iii) changing the expression of general and specific regulatory functions, and (iv) decreasing the expression of protein synthesis such as proteins involved in motility. Differences in gene expression between cells under acute and chronic stress suggest that LH128 goes through changes in genome-wide expression to fully adapt to NaCl stress, without significantly changing phenanthrene degrading activity.

This research investigated effects of narcissism and emotional intelligence (EI) on popularity in social networks. In a longitudinal field study we examined the dynamics of popularity in 15 peer groups in two waves (<I>N</I> = 273). We measured narcissism, ability EI, explicit and implicit self-esteem. In addition, we measured popularity at zero acquaintance and three months later. We analyzed the data using inferential network analysis (temporal exponential random graph modeling, TERGM) accounting for self-organizing network forces. People high in narcissism were popular, but increased less in popularity over time than people lower in narcissism. In contrast, emotionally intelligent people increased more in popularity over time than less emotionally intelligent people. The effects held when we controlled for explicit and implicit self-esteem. These results suggest that narcissism is rather disadvantageous and that EI is rather advantageous for long-term popularity.

Low-cost wastewater treatment systems exist, but few systems are actually implemented in Southeast Asia. Which factors hinder a wide-scale application of such systems, and how can these barriers be overcome?

This study investigated the die-off rates of E. coli and Salmonella in water and soil, and determined the reduction rates of those pathogens on vegetables resulting from typical washing practices. Results revealed that exposure to sunlight and washing with tap water can signifi cantly reduce the pathogen concentrations on lettuce.

Vorwort zur Sondernummer "Wasser" der Ciba Hauszeitschrift.

Drains can be installed to reduce saturated soil condi-tions and improve crop growth. This article evaluates the extent to which these systems may cause losses of plant protection products (PPP). To that end, we esti-mated the drained fraction of Swiss arable land using both existing drainage maps and machine learning. Our drainage map suggests that 25% of Swiss agricultural land has a moderate to high potential of being drained. We further evaluated the risk for PPP losses via drainage and the potential of selected mitigation measures based on a conceptual model summarising the relevant scientific literature. Although drainage losses are highly variable, they are strongly influenced by the extent of preferential flow (PF) in soils and are an important transport pathway to surface waters. Most agricultural soils in Switzerland are prone to PF, given their loamy texture, suggesting that PPP losses via tile drains are an important phenomenon in Swit-zerland’s drained arable fields. The most common mitigation measures for drainage are those recommend-ed for runoff, erosion and leaching. However, given the uncertainty of the local PPP losses and driving factors, no site-or PPP-specific measures can currently be proposed to reduce PPP drainage losses. This study also examines the effectiveness of the regulatory model EXPOSIT in predicting total PPP losses and peak concentrations in watercourses. When compared with experimental data from Agroscope at Zurich-Affoltern, our findings suggest that EXPOSIT does not yield the worst-case estimates for Swiss conditions.

Der "International Bodenseetag" vom 2.Dezember 1967, an dem praktisch die ganze Bevölkerung um den Bodensee zur See-Putzete antrat, gestaltete sich zu einer eindrücklichen Willenskundgebung der gesamten Seeanwohner, das Ihre zu tun, um den bedrohten See, von dem in mancher Hinsicht ihre Existenz abhängt, einer Sanierung entgegenzuführen.

Special Issue: Abstracts of the XXIX International Congress of Psychology

A kinetic model of the contact stabilization process has been developed and experimentally verified with the aid of bench-scale activated sludge units treating domestic sewage. The model provides information on the relationship between the design parameters (process loading, temperature, residence time distribution) and process performance (sludge, production, oxygen uptake, COD-removal, organic nitrogen conversion, nitrification and effluent suspended solids). An oxygen equivalence mass balance equation, which is applicable to all activated sludge process modifications is proposed and may be used in the design and operation of these processes.

Under laboratory conditions, the availability of cadmium, lead and copper in an Orthic Luvisol was investigated when applied to the soil at various initial concentrations. The metals were applied separately or concurrently with the other two heavy metal ions in order to bring about competition for the adsorption sites.<br/> The presence of competing metals increased the general availability especially of cadmium in the soil. Lead and copper were to a lesser extent also affected by the competition of other ions.<br/> On the basis of our ion-competition results we developped two models, namely a chemical equilibrium model and a convective—dispersive model. The models, suitable to predict the consequences of regular heavy metal loading (e.g., in the form of sewage sludge), take into consideration the annual precipitation and the relevant physical parameters of the soil. The conclusions reached by both models are essentially the same and imply that the threshold values for heavy metals in the sewage sludge regulation (Switzerland) are too high.

The partition of Cu and Zn between the particulate and dissolved phases has been investigated in the Carnon River and Restronguet Creek, England; a system contaminated by acid mine drainage. It is shown that binding to the surfaces of amorphous Fe oxyhydroxides regulates Cu and Zn concentrations in solution, in both fresh and saline waters. The sorptive process is pH dependent and is in general agreement with laboratory studies of trace metal adsorption on amorphous Fe oxyhydroxides.

Fluvio-glacial gravel deposits make up most of the groundwater reservoir in Switzerland. At the outcrop scale these deposits display a complex pattern of sedimentary structures. A minor part of these deposits is made up of stringer gravels without any fine fraction. The degree of interconnection of these layers and their extent determine the easiest flow path. Deterministic numerical models help visualize the influence of sedimentary structures on groundwater circulation at different scales.

The derailment of a petrol cistern train at Zürich-Affoltern followed by several explosions caused, a damage of about 10 million Swiss Francs to the sewer system. In the following, the paper describes the measures taken after the desaster and it tries to reconstruct the events in the sewer system that took place after the petrol had entered the system. And finally it looks into potential hazards to sewer systems and plants in general and outlines the measures which must be taken.

This paper investigates whether siphon weight limits the elongation of the siphon of deposit-feeding benthic bivalves under natural conditions. Were this to be so, it would imply that foraging and predator avoidance place conflicting demands on these animals, since an increase in the feeding radius on the surface would be associated with a decrease in the burying depth, and vice versa. The paper presents methods with which to measure siphon length and equations to transform siphon weight to siphon length in two benthic bivalves, <I>Scrobicularia plana</I> and <I>Macoma balthica</I>. Relatively heavy siphons are longer, but also thicker, than lightweight ones. We conclude that most individual bivalves stretch their siphons fully while feeding. However, bivalves with heavy siphons keep part of the siphon in reserve within the shell. Siphon cropping therefore results in an immediate reduction in siphon length, unless the siphon is heavy and a reserve is available. The feeding radius of <I>M. balthica</I> and <I>S. plana</I> is a linear function of shell size. <I>S. plana</I> use half of their siphon length to feed on the surface and the other half to bury themselves, but if the siphon weight is below average, the proportion extended over the surface decreases with siphon size. However, among the animals with a short siphon, those with a good body condition take no risks and live as deeply as possible. A comparison between species reveals that the weight of the extended inhalant siphon per cm amounts, on average, to 0.6% of the total body weight.

A simple, one reactor vessel system, called a fill-and-draw system, was developed for the study of enhanced biological phosphate removal under defined conditions. Sludge was grown in a medium with acetate and glucose as sole energy and carbon sources. The sludge was exposed to cycles with three distinct, consecutive periods; first an anaerobic period, then an aerobic period and finally a settlement period. In the period of settlement one third of the liquid was replaced with fresh medium. Sludge grown under this regime became considerably enriched with polyphosphate-accumulating bacteria. The polyphosphate content reached up to 110 mg P/g dry weight. The amount of polyphosphate in the cells during steady state depended on the acetate:glucose ratio, the nitrate and phosphate concentration in the medium. Highest phosphate accumulation was obtained with an acetate:glucose ratio of 9:1. Intracellular polyphosphate was formed during the aerobic period and was anaerobically hydrolysed and released as phosphate into the medium. In the absence of oxygen and in the presence of 2g acetate-COD/l, 80-90% of phosphate was released by sludge containing 100 mg P/g dry weight. In the absence of acetate only 2-19% of the accumulated phosphate was excreted.

The nickel(II) ion in factor F₄₃₀ pentacarboxylic acid, both in the native form and in the 12,13-di-epimer, in solution can be reversibily in a one-electron to the monovalent state by the action of titanium-(III) citrate. The 3d⁹ Ni(I) is quantitatively detected by EPR spectroscopy as a tetragonally distorted octahedral system with the in the d(<I>x</I>²-<I>y</I>²) orbital resulting in an <I>S</I> = ¹/₂ spin with <I>g</I>_∥ = 2.244, <I>g</I>_⊥ = 2.061, (<I>g</I>_∥ = 2.238, <I>g</I>_⊥ = 2.057 for the di-epimer), subject to isotropic superhyperfine interaction from the four in-plane nitrogen ligand with <I>A</I> = 1.0 mT. The UV-visible spectrum of the reduced native F₄₃₀ has peaks (extinction coefficients in mM^-1 cm^-1) at 268 (24.0), 378 (34.7), and 715 nm (2.3), In the reduced di-epimer these values are 265 (23.7), 376 (27.6), and 710 nm (1.6). Complete reduction is achieved only at alkaline pH; the process an apparent p<I>K</I> of 8.9 (native) or 9.4 (di-epimer). The Ni(II)/Ni(I) in <I>F</I>₄₃₀ has a reduction <I>E</I>_m,10.4 = -0.65 (native) or -0.62 V(diepimer). Three-pulse stimulated ESEEM spectroscopy on the reduced complexes reveals a single, near isotropic proton at ≈13 MHz. In ²H₂O solution this line is replaced by a quadrupole-split deuterium resonance around ≈2 MHz, indicating that the Ni(I) in and 12,13-di-epimeric F₄₃₀ is weakly coordinated by water. The absence of a strong axial bond with water would leave the ability of the d(<I>z</I>²) pair for nucleophilic attack on substrate carbon largely intact.

Although the proclamation of “water as an economic good” has been generally accepted among water resources managers, there are still some debates on the explanation of this topic. In this paper it is argued that different water forms or uses have different kinds of economic value. Even for the same form or use, water economic value can be transferred from one kind to another by interventions.<br/> If water is an economic good, water pricing should be recognized as one of the important incentive measures for water demand management. Although the increased block tariffs (IBTs) have become the tariff structure of choice in many developing countries, it still deserves more careful examination. The traditional IBT-con cannot achieve the initial objectives of IBTs for its incorrect designed structure.<br/> This paper is intent to critically examine the use of IBT-con and to strongly promote a new tariff structure, IRT-cap. The case study of Weinan City shows that IRT-cap is an effective tariff to achieve the objectives of equity, simplicity, transparency and implement as well. Also IRT-cap seems easier to achieve cost recovery than the traditional IBT-con taking the ability to pay of water consumers into account. Pilot projects are necessary to be formulated for verification of this new tariff.

The identification of unknown compounds is essential in a wide variety of research areas and especially so in environmental analysis. Combining liquid chromatography with tandem mass spectrometry today allows the identification of substances that were not amenable to classical techniques.Environmental toxicologists and chemists increasingly focus on chemicals that can potentially cause adverse effects in organisms and humans. Since effect concentrations are often very low, but also because the matrix can affect the sensitivity, selective enrichment has become a popular tool for sample clean-up and lowering the limit of detection. Advances in environmental analysis, including techniques based on molecular recognition for selective enrichment or effect-oriented research were presented in this session.

The clonal population structure of <em>Daphnia</em> spp. in Lake Maarsseveen, a small mesotrophic lake with a maximum depth of 32 m, was studied from April 1989 to July 1991. During this period three distinct periods of diel vertical migration (DVM) occurred. <em>Daphnia galeata</em> and the hybrid <em>D. galeata x D. hyalina</em> were found, the former for a restricted period from June 1989 to December 1990. Both 'species' showed genetic variation at the <em>Pgm</em> locus and high temporal fluctuations in genotype frequencies. These fluctuations and DVM were not related. During 1991 a single hybrid genotype reached frequencies of more than 95%. The relation between clonal composition and DVM of <em>Daphnia</em> in Lake Maarsseveen is discussed.

The problem of organizing collective action campaigns is tackled with a multiagent simulation, in which the actor’s decision to participate is modeled on the basis of an expansion of the social psychological Theory of Planned Behavior. The variables entering into the model of the individual’s decision to participate in a collective action are attitude, return, subjective social norm, and perceived behavioral control. With these four variables, various social scientific theories become integrated (Elaboration Likelihood Model, Theory of Planned Behavior, Rational Choice Theory). The theories allow conceptualization of interactions among individuals, and the effect of activators, who seek to recruit others to participate in a collective action, can be studied. The Simulations of a population of 10,000 different agents presented in this paper reveal the influence of the following factors on the effectiveness of collective action campaigns: The dynamics of creating the collective good, forms of recruitment by activators (allor- none contracts), the size of the collective good, and the resources available to activators (training in persuasion methods, possibility to reward participants).

Sediment cores around Antarctica provide a unique opportunity to cross check and supplement the climatic information recorded in ice cores. Suitable high-resolution data, however, have not been available until now from East Antarctica. We present results from the longest continuous postglacial marine sediment succession (1290 cm) ever obtained from an East Antarctic basin. Twenty-one radiocarbon dates show a consistent age to depth correlation over the last 9400 calibrated years BP (cal. yr BP). For this time interval distinct changes in the silicified ice-related biotic species assemblages, accumulation rates of organic carbon, δ¹³C values, and C/N ratios were detected. We demonstrate that these sediment signatures can be used as climate proxies. Our results indicate significant Holocene climatic variability with a climatic optimum between 3500 and 2500 cal. yr BP. This was followed by an abrupt and dramatic cooling that took place within less than 200 yr. Corroborating the results of other researchers we hypothesize that this climatic optimum and its termination was a circumantarctic event which would appear to be out of phase with a proposed global temperature trend (maximum) during the Holocene.

Resting eggs of planktonic organisms from datable sediment cores are increasingly used to reconstruct historical information on the abundance, size, genetic composition, and microevolution of planktonic organisms. All of these studies have relied on the (up to now) mostly untested assumption that the resting egg bank in sediment will indeed allow an accurate reconstruction of past populations. Here we test the performance of the egg bank to reconstruct historical data of the <I>Daphnia</I> population of Lake Constance, which was thoroughly investigated throughout the past century. We show that it is possible to reproduce the variability in the abundance, size, and genetic composition of <I>Daphnia galeata</I> within a period of ∼2 decades. Furthermore, resting egg data allowed us to reconstruct the timing of the invasion of <I>D. galeata</I> into Lake Constance. However, the egg bank did not reconstruct (1) the dynamics of the native <I>Daphnia</I> species of Lake Constance, <I>D. hyalina</I>, and (2) the relative importance of the two <I>Daphnia</I> species. We present evidence that the latter is caused by differences in the sexually reproductive activity between the two species. The failure to reconstruct the long-term dynamics of <I>D. hyalina</I> in the lake is most probably due to a change in the frequency and timing of sexual activity during the course of eutrophication.

Detecting small amounts of genetic subdivision across geographic space remains a persistent challenge. Often a failure to detect genetic structure is mistaken for evidence of panmixia, when more powerful statistical tests may uncover evidence for subtle geographic differentiation. Such slight subdivision can be demographically and evolutionarily important as well as being critical for management decisions. We introduce here a method, called spatial analysis of shared alleles (SAShA), that detects geographically restricted alleles by comparing the spatial arrangement of allelic co-occurrences with the expectation under panmixia. The approach is allele-based and spatially explicit, eliminating the loss of statistical power that can occur with user-defined populations and statistical averaging within populations. Using simulated data sets generated under a stepping-stone model of gene flow, we show that this method outperforms spatial autocorrelation (SA) and Φ_ST under common real-world conditions: at relatively high migration rates when diversity is moderate or high, especially when sampling is poor. We then use this method to show clear differences in the genetic patterns of 2 nearshore Pacific mollusks, <em>Tegula funebralis</em> (= <em>Chlorostoma funebralis</em>) and <em>Katharina tunicata</em>, whose overall patterns of within-species differentiation are similar according to traditional population genetics analyses. SAShA meaningfully complements Φ_ST/<em>F</em>_ST, SA, and other existing geographic genetic analyses and is especially appropriate for evaluating species with high gene flow and subtle genetic differentiation.

Im vorliegenden Feldexperiment zum sparsamen Umgang mit Elektrizität wurde in einer mittelgroßen Gemeinde untersucht, ob die Wirksamkeit von Information mit verschiedenen Kombinationen bewährter umweltpsychologischer Interventionsinstrumente gesteigert werden kann. Gleichzeitig wurde eine neue Methode getestet, Interventionsinstrumente weiterzuverbreiten und bei den angestrebten Zielgruppen zur Wirkung zu bringen. Die Stromsparaktion gliederte sich in zwei Phasen: eine Diffusionsphase und eine Interventionsphase mit vier experimentellen Bedingungen. In der Diffusionsphase wurden Diffusionsinstrumente in Form von Abreißblöcken mit Rücksendekarten an fünfzig zufällig ausgewählte Personen verteilt, die sie gemäß einer Instruktion an Bekannte und Nachbarn weitergeben sollten. Mit Hilfe der Rücksendekarten wurden eine Baseline-Messung des Stromzählerstands sowie Adressen potentieller Teilnehmer gewonnen. In der nachfolgenden, einen Monat dauernden Interventionsphase wurden die Teilnahmewilligen zufällig vier Interventionsgruppen zugeteilt: nur Information; Information und Selbstfeedback; Information und private, schriftliche Selbstverpflichtung sowie eine Kombination von Information, Selbstverpflichtung und Selbstfeedback. Außerdem wurde eine Kontrollgruppe gebildet, bei der lediglich der Stromverbrauch gemessen wurde. Einerseits zeigte sich, dass die instruierte Selbstverbreitung als neuartiges Diffusionsinstrument gut funktionierte, anderseits konnten sowohl die Verbrauchsreduktionen in der Größenordnung von 10%, die sich auch anlässlich einer unangekündigten Nachmessung vier Wochen nach Abschluss des Experiments als stabil erwiesen hatten, als auch die Unterschiede zwischen den Interventionsbedingungen statistisch leider nicht gesichert werden.

<b>Aim</b> Current estimates of species richness within rapidly evolving species flocks are often highly dependent on the species status of allopatric populations that differ in phenotypic traits. These traits may be unreliable indicators of biological species status and systematists may have inconsistently assigned species among lineages or locations on the basis of these traits, thus hampering comparative studies of regional species richness and speciation rates. Our aim was to develop a method of generating standardized estimates of regional species richness suitable for comparative analysis, and to use these estimates to examine the extent and consistency of species assignment of allopatric populations within rapidly evolving cichlid fish flocks present in three east African lakes.<br/> <b>Location</b> Lakes Malawi, Victoria and Tanganyika.<br/> <B>Methods</B> Using published taxon co-occurrence data, a novel approach was employed to calculate standardized 'minimum' estimates of regional species richness for hard substrate associated complexes of cichlids within each of the lakes. Minimum estimates were based on an explicit assumption that if taxa present on equivalent habitats have disjunct distributions, then they are allopatric forms of the same species. These estimates were compared with current observed 'high-end' regional species richness estimates for those complexes to determine the consistency of species assignment of allopatric populations between lineages within a lake. A 'sympatry' index was developed to enable comparisons of levels of species assignment of allopatric populations between-lakes to be made.<br/> <B>Results</B> Within each lake, the minimum and high-end estimates for species richness were significantly correlated across complexes, indicating that the complexes that contain more recognized species contain the most genuine biological species. However, comparisons of complexes among lakes revealed considerable differences. For equivalent geographical areas, substantially higher proportions of recognized species were totally allopatric within the studied Lake Malawi and Lake Victoria complexes, than those of Lake Tanganyika.<br/> <B>Main</B> Conclusions Among African lakes, levels of assignment to species status of allopatric populations were found to be distinctly different. It is unclear whether the discrepancies are a consequence of differences between the lake faunas in degrees of phenotypic divergence among allopatric populations, or are simply the result of inconsistent taxonomic practices. In either case, these results have considerable wider relevance for they emphasize that quantitative measures of regional and beta diversity are critically dependent on the species status of allopatric populations, an issue usually neglected in comparative studies of species richness. The technique introduced here can be used to standardize measures of regional diversity of lineages for comparative analyses, potentially enabling more accurate identification of processes influencing rates of speciation.

Evaluating uncertainty in solute transport under nonstationary flow conditions is a computationally demanding task. This is particularly true for cases with a two-point covariance function of log conductivity depending on the actual positions of the points rather than their distance vector. These may occur when the geological formation exhibits a trend. Nonstationarity can also be the result of uncertainty in the trend parameters of the mean log conductivity value, or it may originate from conditioning of the log conductivity field to measurements of, for example, head or conductivity. We present an efficient numerical method for evaluating the variance of travel time in such formations. We cover cases in which the nonstationary covariance functions are constructed from stationary counterparts, either by scaling functions or by summation with nonstationary functions resulting from marginalization or conditioning. We apply a matrix-based first- order second-moment (FOSM) method for uncertainty propagation, using the continuous adjoint-state method for coupled systems to evaluate the sensitivity matrix. The resulting matrix-matrix multiplications are accelerated by fast Fourier transformation (FFT) techniques after periodic embedding of the covariance matrices referring to the stationary counterparts. The combination of these methods makes it possible to compute the travel time uncertainty in domains discretized by several hundred thousand log conductivity values on standard personal computers within a reasonable time-frame. For demonstration, we apply the method to a binary medium and a medium exhibiting a continuous trend in the covariance function. In the latter application we also demonstrate the effects of marginalization and conditioning.

The Quasi-Linear Geostatistical Approach is a method of inverse modeling to identify parameter fields, such as the hydraulic conductivity in heterogeneous aquifers, given observations of related quantities like hydraulic heads or arrival times of tracers. Derived in the Bayesian framework, it allows to rigorously quantify the uncertainty of the identified parameter field. Since inverse modeling in subsurface flow is in general a non-linear problem, the Quasi-Linear Geostatistical Approach employs an algorithm for non-linear optimization. Up to presence, this algorithm has been similar to the Gauss-Newton algorithm for least-squares fitting and fails in cases of strong non-linearity. In this study, we present and discuss a new modified Levenberg-Marquardt algorithm for the Quasi-Linear Geostatistical Approach. Compared to the original method, the new algorithm offers increased stability and is more robust, allowing for stronger on-linearity and higher variability of the parameter field to be identified. We demonstrate its efficiency and improved convergence compared to the original version in several test cases. The new algorithm is designed for the general case of an uncertain mean of the parameter field, which includes the cases of completely known and entirely unknown mean as special cases.

Numerical and theoretical studies have indicated that pore- scale mixing can be the limiting process for reactions among dissolved compounds in porous media. It has been claimed that multicomponent reactions in porous media could be accurately estimated using mixing coefficients obtained from point-like measurements of conservative tracer concentrations. In this study, we verify these concepts experimentally by tracer tests in a homogeneously packed saturated sand column. Fiber-optic fluorometry was applied to detect point-related concentrations of fluorescein, which was used as both the conservative and the reactive tracer. In the reactive tracer experiment, an acidic solution containing the tracer was displaced by an alkaline solution without tracer. Since the fluorescence of fluorescein is quenched at low pH, the fluorescence intensity measured in the reactive breakthrough curve indicated the mixing of the two solutions. The measured reactive breakthrough curves were compared to predictions based on the conservative breakthrough curves. Predictions and measurements agreed well. Our results imply that incomplete mixing on the pore scale is of minor significance for field-scale applications. On this scale, however, even weak sorption might influence mixing significantly.