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This study aims to illustrate the effect of hydraulic retention time (HRT) on reactor performance and biofilm characteristics in the gravity-driven membrane (GDM) reactor pretreating seawater. Three GDM reactors were operated in parallel for ~62 days under HRTs of 22 h, 54 h, and 102 h, respectively. The results indicated that the GDM reactors at HRTs of 22 h and 102 h had relatively higher permeate flux and superior permeate quality (especially assimilable organic carbon, AOC) compared to that at HRT of 54 h. Extending HRT benefited to reduce irreversible fouling, but cake layer fouling was maximized at HRT of 54 h. As different HRTs led to significantly dissimilar microbial community structure and cake layer composition, such higher cake layer resistance at HRT of 54 h was attributed to homogenous nature of the biofilm, which contained greater amount of organics and less abundance of Nematoda (dominant predator). Lastly, as increasing ~5-time of HRT (from 22 h to 102 h) improved ~1.5 of permeate flux, a shorter HRT of 22 h was preferable for the GDM reactor in pretreating seawater with regard to treatment productivity and footprint. National Research Foundation (NRF) Public Utilities Board (PUB) This research is supported by the National Research Foundation, Singapore, and PUB, Singapore's National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) Programme, awarded to Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University, Singapore (NTU).

Point-of-use ceramic filters are one of the strategies to address problems associated with waterborne diseases to remove harmful microorganisms in water sources prior to its consumption. In this study, development of adsorption-based ceramic depth filters composed of alumina platelets was achieved using spray granulation (calcined at 800 °C). Their virus retention performance was assessed using cartridges containing granular material (4 g) with two virus surrogates: MS2 and fr bacteriophages. Both materials showed complete removal, with a 7 log

Gravity-driven membrane (GDM) filtration has been investigated for almost 10 years. The technology is characterized not only by relatively lower transmembrane pressures which can be achieved by gravity (extremely low energy consumption), but also by the phenomenon of flux stabilization: A biofilm is allowed to form on the membrane and a stabilization of flux occurs which is related to biological processes within the biofilm layer on the membrane. This enables stable operation during a year or longer without any cleaning or flushing. Initially, the technology was developed mainly for household drinking water treatment, but in the meantime, the research and application has expanded to the treatment of greywater, rainwater, and wastewater as well as the pretreatment of seawater for desalination. This review covers the field from the rather fundamental research on biofilm morphology and microbial community analysis to the impact of feedwater composition, process parameters and organic removal performance. Not only household applications, but also for community-scale treatment and full-scale applications are discussed. In addition, the application potential is highlighted in comparison to conventional ultrafiltration. Finally, an overall assessment is illustrated and the research and development needs are identified.

Context: Dynamic balance exercises are commonly utilized during ankle sprain and chronic ankle instability (CAI) rehabilitation. Blood flow restriction (BFR) has been used to enhance muscle activity during exercise and improve outcomes of traditional rehabilitation exercises in clinical populations. Objective: Examine the effects of BFR on lower-extremity muscle activation during dynamic balance exercises in individuals with CAI. Design: Crossover study design. Setting: Laboratory. Patients or Other Participants: Twenty-five (N = 25) young adults with a history of CAI. Interventions: Participants performed dynamic balance reaching exercises during 2 randomized order conditions, BFR, and control. For each condition, participants performed 2 trials of balance exercises. Each trial included 4 sets (30 × 15 × 15 × 15) of reaches in anterior, posteromedial, and posterolateral directions. For the BFR condition, the authors placed a cuff around the proximal thigh at 80% of arterial occlusion pressure. For the control condition, no cuff was worn. Main Outcome Measure(s): The authors recorded normalized electromyography muscle activation of the vastus lateralis, soleus, tibialis anterior, and fibularis longus during balance exercise trials and recorded participants’ ratings of perceived postural instability and exertion after each trial of balance exercises. Results: The authors observed greater vastus lateralis (P d = 0.86 [0.28 to 1.44]) and soleus (P = .03, d = 0.32 [−0.24 to 0.87]) muscle activation during balance exercises with BFR than control. The authors observed no differences in tibialis anterior (P = .33, d = 0.09 [−0.46 to 0.65]) or fibularis longus (P = .13, d = 0.06 [−0.50 to 0.61]) muscle activation between the conditions. The authors observed greater ratings of perceived postural instability (P = .004) and exertion (P Conclusions: Individuals with CAI demonstrated large increases in vastus lateralis and small increases in soleus muscle activation during dynamic balance exercises with BFR. The BFR had no effect on fibularis longus and tibialis anterior muscle activation. Individuals with CAI perceived greater postural instability and exertion during dynamic balance exercises with BFR.

A large variety of substances are used in building materials to improve their properties. In recent years, attention to organic additives used, for example, in renders, façade paints or roof sealing sheets has increased as these compounds have been detected in urban stormwater runoff and surface waters. In this paper, we show the extent of emissions induced by rain events in two study sites in Berlin. For this purpose, stormwater runoff from roofs, façades, and in storm sewers was sampled and analysed over a period of 1.5 years in two residential catchments. Results show that, in particular, the biocides diuron and terbutryn from façades, the root protection agents mecoprop and MCPA in bituminous sheeting, and zinc from roofs and façades reach concentrations in the stormwater sewer that exceed limit values for surface waters. Additionally, transformation products of the biocides were also detected. However, many other analysed substances were below the quantification limit or inconspicuous in their concentration levels. The emissions, modelled with the software COMLEAM, demonstrate that in urban areas the limit values in smaller surface waters are exceeded during wet weather. Furthermore, the orientation of the buildings to wind-driven rain is essential for the emitted load from façades. The calculated mass balances of both catchments show that a major portion of all substances remains on-site and infiltrates diffusely or in swales, while the remaining portion is discharged to stormwater sewers. For example, in one of the two study sites

Water 14(2), 228 (2022). doi:10.3390/w14020228 special issue: "Special Issue "Stormwater Management and the Environmental Impact of Building Materials" / Special Issue Editor: Prof. Dr. Michael Burkhardt, Guest Editor", Published by MDPI, Basel

To protect house facades from fouling by microorganisms, biocides can be added to a render or paint before it is applied. During driving rain events, these biocides gradually leach out and have the potential to pollute soil or aquatic ecosystems. We studied the leaching behavior of biocides and toxicity of leachates from renders with either free or encapsulated biocides. Both render types contained equal amounts of terbutryn, 2-octyl-3(2H)-isothiazolinone (OIT), and 4,5-dichloro-2-n-octyl-4-isothiazolino-3-one (DCOIT). Nine leachate samples were generated over 9 immersion cycles according to a European standard, and biocides were quantified. The first and ninth leachate samples were tested using bioassays with algae, bacteria, and water fleas, the first sample was also tested with earthworms and springtails. Encapsulation reduced leaching of terbutryn, OIT, and DCOIT by 4-, 17-, and 27-fold. For aquatic organisms, the toxicity of water from render containing encapsulated biocides was always lower than that of render with free biocides. Furthermore, toxicity decreased by 4- to 5-fold over the 9 immersion cycles. Inhibition of photosynthesis was the most sensitive endpoint, followed by algal growth rate, bacterial bioluminescence, and water flea reproduction. Toxicity to algae was due to terbutryn and toxicity to bacteria was due to OIT. None of the samples affected soil organisms. Results demonstrate that combining standardized leaching tests with standardized bioassays is a promising approach to evaluate the ecotoxicity of biocides that leach from facade renders. Environ Toxicol Chem 2018;37:2246-2256. © 2018 SETAC.

Steel components are typically treated with anti-corrosion coatings like epoxy or polyurethane resins to protect the integrity and functioning of steel. Such resins may contain substances, such as bisphenol A (BPA), that have caused concern in a human and environmental toxicological context. We investigated the release of toxicity from four anti-corrosion coatings used in hydraulic and civil engineering. Resins were applied onto glass plates and leachate samples produced by horizontally shaking the plates in water for 7 days. Two experiments were conducted, one with a 1 day and one with a 7 day curing period. Using a suite of bioassays, we tested samples for: agonistic and antagonistic effects on various mammalian nuclear receptors; inhibition of photosynthesis and growth in algae; inhibition of bacterial bioluminescence; and inhibition of water flea reproduction. Concentrations of BPA, bisphenol F and various BPA transformation products were determined by chemical analysis (LC-MS/MS). Bioassay results were evaluated using a scheme developed by DIBt (Centre of Competence for Construction, Berlin, Germany). Three products induced responses in one or more of the measured endpoints and toxicity profiles varied markedly in intensity across products. One product released high amounts of BPA which was associated with effects on nuclear receptor transactivation, requiring a more than 700-fold dilution for effect induction to fall below 20%. The same product was also the most toxic to water flea reproduction, requiring ca. 70-fold dilution for effects to fall below 20%. Another product was highly toxic in terms of bacterial bioluminescence, particularly after a shorter curing time, requiring a ca. 1'300-fold dilution for effects to fall below 20%. The third product required a 22-fold dilution for inhibition of water flea reproduction to drop below 20%. Results show that anti-corrosion coatings based on epoxy resins can be a source of toxicity to the aquatic environment. The fact that some products are more toxic than others highlights opportunities for the development of low risk formulations and products with better environmental performance. Finally, the DIBt scheme provides a useful starting point to develop further ecotoxicity guidelines for testing and data evaluation of leachates from construction materials. (C) 2017 Elsevier Ltd. All rights reserved.

A large fraction of engineered nanomaterials (ENM) will be deposited in landfills and it is assumed that ENM are securely locked in landfill sites and cannot leach into the environment (e.g. surface waters). However, experimental evidence supporting this assumption is lacking, as current production volumes of ENM are still too small and/or analytical techniques not sensitive enough to allow for the detection and quantification of ENM in landfill leachates. TiO 2 particles are currently used in large quantities, for example in construction materials such as paints and renders as white pigments and their sizes extend into the nano-size range. We, therefore, selected TiO 2 particles as a surrogate to assess the potential release of ENM from construction and demolition (C&D) landfill sites. We collected leachate samples from a landfill over one year and used complementary analytical techniques, including inductively coupled plasma (ICP) – optical emission spectroscopy (OES), automated scanning electron microscopy (auto SEM), transmission electron microscopy (TEM) and single particle ICP - mass spectrometry (spICPMS) to quantify TiO 2 particles in landfill leachates. Total elemental Ti contents were mostly around a few tens of μg L − 1 and were strongly correlated with total suspended solids. Based on the volumetric discharge of the landfill leachate water from the landfill, we estimate a total amount of ~ 0.5 kg of TiO 2 particles that are released annually from the landfill. Ti concentrations derived from ICP-OES measurements were in good agreement with quantifications based on TiO 2 particles detected by auto SEM analyses. spICPMS measurements indicated a number concentration of Ti-containing particles in the order of 10 5 mL − 1 and TEM analyses dominantly revealed nanoscale TiO 2 particles with a spherical shape typically observed for TiO 2 particles used as white pigments. In addition, angular TiO 2 particles with a well-defined crystal habitus were detected, suggesting that also natural TiO 2 particles of comparable sizes are present in the landfill leachates. The results from this study indicate that (nanoscale) TiO 2 particles are released from C&D landfill sites (~ 5 g/year). Although the amount of TiO 2 particles released from C&D landfill sites may still be rather low, these particles may serve as proxy for assessing the future release of ENM from C&D landfill sites, which may become relevant as an increasing use of ENM is predicted for construction materials in general.

A pilot gravity-driven microfiltration (GDM) reactor was operated on-site for over 250 days to pretreat seawater for reverse osmosis (RO) desalination. The microbial community analysis indicated that the dominant species in the pilot GDM system (~ 18.6 L/m2 h) were completely different from those in the other tested GDM systems (~ 2.7–17.2 L/m2 h), operating on the same feed. This was possibly due to the differences in available space for eukaryotic movement, hydraulic retention time (i.e., different organic loadings) or operation time (250 days vs. 25–45 days). Stichotrichia, Copepoda, and Pterygota were predominant eukaryotes at genus level in the pilot GDM. Furthermore, the GDM pretreatment led to a significantly lower RO fouling potential in comparison to the ultrafiltration (UF) system. This was attributed to the fact that GDM filtration produced a permeate with less amount of assimilable organic carbon (AOC) and biopolymers. Accordingly, lower amount of organic foulants (biopolymers and low molecular weight neutrals) and less biofilm formation on the GDM-RO membrane were observed. Although α-proteobacteria were dominant in both RO fouling layers, their bacterial community compositions at genus level were significantly different. Thalassobius had higher abundance in the GDM-RO fouling layers, while Erythrobacter and Hyphomonas were more predominant in the UF-RO fouling layers. EDB (Economic Devt. Board, S’pore) Accepted version

Hintergrund Die Endometriose ist eine haufige Erkrankung der geschlechtsreifen Frau, die Schmerzen und Unfruchtbarkeit verursacht. Zudem kann sie zur Zerstorung von Organen fuhren. Zum Spektrum der Behandlung gehort die operative Sanierung.

This study compared the membrane performances and water quality of gravity-driven membrane (GDM) systems in treating algae-polluted lake water under different operation conditions (microfiltration (MF) vs. ultrafiltration (UF); Chlorella vulgaris (green algae) vs. Phaeodactylum tricornutum (diatom); different algal amounts in the lake water). The results showed the cake layer fouling was predominant in the UF-GDM systems, while irreversible fouling contributed majorly to the MF-GDM fouling. As a result, the UF-GDM systems achieved >1.5 time higher permeate flux compared to the MF-GDM systems in treating algae-polluted lake water. Compared to the green algae, the presence of the diatom cells in the feed water had more negative impacts on the UF permeate flux (increasing the cake layer resistance) and water quality (containing more low molecule weight neutrals). The analysis of cake layer foulants revealed that more aromatic protein-based biopolymers were accumulated on the membranes during filtration of algae-polluted lake water and the biopolymer amounts were almost linearly associated with membrane fouling potential of the GDM systems.

As a low energy and chemical free process, gravity-driven membrane (GDM) filtration has shown a potential for seawater pretreatment in our previous studies. In this study, a pilot submerged GDM reactor (effective volume of 720 L) was operated over 250 days and the permeate flux stabilized at 18.6 ± 1.4 L/m2h at a hydrostatic pressure of 40 mbar. This flux was higher than those in the lab-scale GDM reactor (16.3 ± 0.2 L/m2h; effective volume of 8.4 L) and in the filtration cell system (2.7 ± 0.6 L/m2h; feed side volume of 0.0046 L) when the same flat sheet membrane was used. Interestingly, when the filtration cell was submerged into the GDM reactor, the flux (17.2 L/m2h) was comparable to the submerged membrane module. Analysis of cake layer morphology and foulant properties indicated that a thicker but more porous cake layer with less accumulation of organic substances (biopolymers and humics) contributed to the improved permeate flux. This phenomenon was possibly associated with longer residence time of organic substances and sufficient space for the growth, predation, and movement of the eukaryotes in the GDM reactor. In addition, the permeate flux of the submerged hollow fibre membrane increased with decreasing packing density. It is thought that the movement of large-sized eukaryotes could be limited when the space between hollow fibres was reduced. In terms of pretreatment, the GDM systems effectively removed turbidity, viable cells, and transparent exopolymer particles from the feed seawater. Importantly, extending the reactor operation time produced a permeate with less assimilable organic carbon and biopolymers. Thus, the superior quality of the GDM permeate has the potential to alleviate subsequent reverse osmosis membrane fouling for seawater treatment. EDB (Economic Devt. Board, S’pore) Accepted version

The European Construction Products Regulation allows Member States to adopt rules for evaluating the environmental impact of their buildings. The aim of the project was to develop recommendations for a test battery for the ecotoxicological assessment of the environmental impact of construction products for outdoor use and contribute to the European harmonization of test methods. From a shortlist of 39 products 20 products were included in the ecotoxicological testing program. Monolithic and plate-like construction products were eluted in the Dynamic Surface Leaching test (DSLT) in accordance with CEN/TS 16637-2, granular products were eluted in a one stage batch test in accordance with DIN EN 12457-1. The eluates were examined in four aquatic toxicity tests (algae, daphnia, luminescent bacteria, fish eggs), a genotoxicity test (umu test) and in the respirometer test (OECD 301 F). Here, low to very high ecotoxicity was observed (up to a dilution factor of 1536). Six out of 8 eluates, whose TOC exceeded 10 mg L −1 showed a good biodegradability above 75%. The intra-laboratory repeatability of the Lowest Ineffective Dilution (LID) usually was within ±1 dilution steps (ecotoxicity tests) and ±2 dilution steps (leaching and ecotoxicity tests). This is acceptable, when considering that the overall variability of sample preparation, leaching test, and bioassays add up. The conclusions lead to practical recommendations for a suitable combination of leaching and ecotoxicity tests.

Polyether trisiloxane surfactants are widespread used as agricultural adjuvants because they increase the activity and the rainfastness of pesticides. On the contrary to pesticides, the environmental fate of agricultural adjuvants has not been much investigated, yet. Especially for trisiloxane surfactants, the knowledge on their environmental fate is scarce. To fill this gap, the mobility of a polyether trisiloxane surfactant on soil was studied. With a sorption batch equilibrium method, distribution coefficients between water and soil (K d, K oc, and K clay) were estimated for two standard soils (loam and sandy loam) and for every homologue of the trisiloxane surfactant. The obtained values for K d were between 15 and 135 cm3 g−1, indicating that the trisiloxane surfactant is only slightly mobile in soil. The leaching in soil column was studied in a worst case scenario where the application of the trisiloxane surfactant was done on quartz sand and was immediately followed by a heavy rainfall. Less than 0.01 % of the initially applied trisiloxane surfactant had leached through 20 cm of quartz sand. Based on the K d values and the leaching in a soil column, the studied trisiloxane surfactant seems to be unlikely to leach through soil after application as agricultural adjuvant.

Biocides are included in organic building façade coatings as protection against biological attack by algae and fungi but have the potential to enter the environment via leaching into runoff from wind driven rain. The following field study correlates wind driven rain to runoff and measured the release of several commonly used organic biocides (terbutryn, Irgarol 1051, diuron, isoproturon, OIT, DCOIT) in organic façade coatings from four coating systems. During one year of exposure of a west oriented model house façade in the Zurich, Switzerland area, an average of 62.7 L/m(2), or 6.3% of annual precipitation came off the four façade panels installed as runoff. The ISO method for calculating wind driven rain loads is adapted to predict runoff and can be used in the calculation of emissions in the field. Biocide concentrations tend to be higher in the early lifetime of the coatings and then reach fairly consistent levels later, generally ranging on the order of mg/L or hundreds of μg/L. On the basis of the amount remaining in the film after exposure, the occurrence of transformation products, and the calculated amounts in the leachate, degradation plays a significant role in the overall mass balance.

Seawater pretreatment by gravity-driven membrane (GDM) filtration at 40 mbar has been investigated. In this system, a beneficial biofilm develops on the membrane that helps to stabilize flux. The effects of membrane type, prefiltration and system configuration on stable flux, biofilm layer properties and dissolved carbon removal were studied. The results show that the use of flat sheet PVDF membranes with pore sizes of 0.22 and 0.45 μm in GDM filtration achieved higher stabilized permeate fluxes (7.3-8.4 L/m(2)h) than that of flat sheet PES 100 kD membranes and hollow fibre PVDF 0.1 μm membranes. Pore constriction and cake filtration were identified as major membrane fouling mechanisms, but their relative contributions varied with filtration time for the various membranes. Compared to raw seawater, prefiltering of seawater with meshes at sizes of 10, 100 and 1000 μm decreased the permeate flux, which was attributed to removal of beneficial eukaryotic populations. Optical coherence tomography (OCT) showed that the porosity of the biofouling layer was more significantly related with permeate flux development rather than its thickness and roughness. To increase the contact time between the biofilm and the dissolved organics, a hybrid biofilm-submerged GDM reactor was evaluated, which displayed significantly higher permeate fluxes than the submerged GDM reactor. Although integrating the biofilm reactor with the membrane system displayed better permeate quality than the GDM filtration cells, it could not effectively reduce dissolved organic substances in the seawater. This may be attributed to the decomposition/degradation of solid organic substances in the feed and carbon fixation by the biofilm. Further studies of the dynamic carbon balance are required.

This paper gives a solution to the question on how much secondary control reserve (SCR) should be offered from a hydro power storage from the perspective of a generator. We compare revenue and costs and derive the economically reasonable amount of SCR. The cost side is calculated using a hydro power storage scheduling optimization program. The income side is determined by a model that optimizes the income of the SCR capacity as well as the SCR energy auction. The underlying goal is to maximize the profit for the participating generator. We use historical prices to generate optimal results for a 100 MW pumped hydro power storage.

We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present as Ag(2)S. Results from batch experiments suggested that Ag-NP transformation to Ag(2)S occured in the nonaerated tank within less than 2 h. Physical and chemical transformations of Ag-NP in WWTPs control the fate, the transport and also the toxicity and the bioavailability of Ag-NP and therefore must be considered in future risk assessments.

Hintergrund, Ziel und Zweck Die Anwendung von Nanosilber nimmt zwar stetig zu, doch die Kenntnisse zum Vorkommen nanoskaligen Silbers in Abwassern und zum Verhalten in Klaranlagen sind gering. Untersuchungen unter realen Betriebsbedingungen fehlen sogar vollstandig. In der vorliegenden Studie wurde Nanosilber mit folgenden Zielen untersucht: 1) Hemmung der Nitrifikationsleistung im Belebtschlamm einer Klaranlage, 2) Erstellung einer Massenbilanz fur Nanosilber in einer Pilotklaranlage und 3) Verifizierung der Bilanz durch eine Untersuchung in einer realen kommunalen Klaranlage, in die durch einen Indirekteinleiter partikulares Silber eingetragen wird. Methoden Der Einfluss von vier marktublichen Nanosilberadditiven auf die Ammoniumoxidation im Belebtschlamm wurde in Batchreaktoren bei zwei Konzentrationen (1, 100 mg/L Ag) und zwei Expositionszeiten (2 h, 6 Tage) untersucht. In einer Pilotklaranlage in der Grose von 70 Einwohnerwerten wurde partikulares Silberchlorid und metallisches Nanosilber jeweils fur die Dauer zweier Schlammalter (25 Tage) dosiert und weitere zwei Schlammalter bilanziert. Als Grundlage wurden die Abwassermengen und die Silberkonzentrationen erfasst. Zudem wurde die Anlagerung von Nanosilber an Feststoffen durch elektronenmikroskopische Untersuchungen erfasst. Auf einer Klaranlage (60 000 Einwohnerwerte) wurden der Zu- und Ablauf sowie der Faulschlamm im Rahmen von vier Messkampagnen beprobt und wiederum auf Silber chemisch und Nanosilber mikroskopisch analysiert. ErgebnisseDie Zugabe von 1 mg/L Ag in Form von Silbernitrat, metallischem Nanosilber, partikularem Silberchlorid und Mikrokomposit-Silber bleibt ohne Wirkung auf die Nitrifikationsleistung. Dagegen resultieren 100 mg/L Ag fur alle Silberformen in einer Hemmung, welche zwischen 100 % fur Silbernitrat und 20–30 % fur kolloidales Nanosilber liegt. In der Massenbilanzstudie wird deutlich, dass nach Zugabe von partikularem Silberchlorid 96 % des Silbers mit dem Schlamm und 4 % uber das Nachklarbecken – also das gereinigte Abwasser – ausgetragen werden. Die Massenbilanz fur metallisches Nanosilber fallt ahnlich aus. Diese Bilanzen aus der Pilotklaranlage decken sich mit derjenigen von einer realen Klaranlage. Der Silberaustrag korreliert mit dem Feststoffaustrag im Schlammabzug und Nachklarbeckenablauf. Die Jahresfracht zum Vorfluter durfte bei 4–40 mg/a Ag pro Einwohnerwert liegen. Mit Elektronenmikroskopie lasst sich zeigen, dass das Nanosilber in und an die Belebtschlammflocken gebunden vorliegt. Diskussion Chlorid ist im Abwasser in groseren Mengen verfugbar, sodass Silberionen praktisch vollstandig zu Silberchlorid ausfallen. Silberionen binden auch an organischen Komplexbildnern und reduzierten Schwefelgruppen. Deshalb ist eine hemmende Wirkung auf Nitrifikanten selbst fur Silbernitrat bei 1 mg/L Ag (250 mg Ag/kg TS) nicht zu beobachten. Bei der sehr hohen Dosierung von 100 mg/L Ag stellt sich nicht genugend schnell ein Losungsgleichgewicht zwischen freien Silberionen und Bindungsstellen ein. Die Massenbilanz uber die Klaranlage unterstreicht, dass Nanosilber sehr gut an Partikeln bindet und effizient aus dem Abwasser eliminiert wird. Verglichen mit problematischen organischen und anorganischen Mikroverunreinigungen ist die Eliminationsrate mit uber 95 % hoch. Mit der Reduktion der ungelosten Stoffe (GUS) lasst sich auch die Silberfracht im Ablauf vermindern. SchlussfolgerungenNanosilber liegt in der Regel gebunden vor, wird dadurch effizient eliminiert und kann allenfalls mit einer Abwassernachbehandlung in Form einer Raum- oder Flachenfiltration weiter reduziert werden. Der Schlamm stellt die wichtigste Senke fur Nanosilber dar. Silberpartikel >100 nm Grose binden tendenziell weniger gut als Nanosilber im engeren Sinne. Alle analysierten Silberpartikel im Zulauf, Ablauf und Schlamm deuten darauf hin, dass das Silber vor allem sulfidisch (als Ag2S) die Klaranlage verlasst. Aufgrund der vernachlassigbaren Wasserloslichkeit dieser Silberform werden keine Silberionen freigesetzt. Empfehlungen und Ausblick Die Forschung ist auf Prozessmechanismen und die Oberflachenmodifikation von Nanosilber zu konzentrieren, die die Speziierung und das Bindungsvermogen unter Umweltbedingungen beeinflussen. Verglichen mit anderen organischen Spurenstoffen zeigt sich kein dringender Handlungsbedarf bezuglich Nanosilber im Bereich von Klaranlagen. Masnahmen zur Emissionsminderung sollten dennoch dem Vorsorgeprinzip folgend entwickelt werden.

In this study we investigate the release of metallic silver nanoparticles (Ag-NP) from paints used for outdoor applications. A facade panel mounted on a model house was exposed to ambient weather conditions over a period of one year. The runoff volume of individual rain events was determined and the silver and titanium concentrations of 36 out of 65 runoff events were measured. Selected samples were prepared for electron microscopic analysis. A strong leaching of the Ag-NP was observed during the initial runoff events with a maximum concentration of 145 micro Ag/l. After a period of one year, more than 30% of the Ag-NP were released to the environment. Particles were mostly15 nm and are released as composite colloids attached to the organic binders of the paint. Microscopic results indicate that the Ag-NP are likely transformed to considerably less toxic forms such as Ag2S.

Hintergrund, Ziel und Zweck Die Belastung von Flieβgewassern durch organische Mikroverunreinigungen wirft haufig die Frage der Quellenzuordnung auf. Baumaterialien als Quellen problematischer Spurenstoffe finden in der Gewasserbeurteilung bisher wenig Beachtung, obwohl bereits heute biozide Wirkstoffe aus Materialschutzanwendungen zu einer Belastung des Regenwasserabflusses fuhren. In der vorliegenden Untersuchung wurden (1) die okotoxikologischen Kenngrosen fur typische Biozide in Fassadenbeschichtungen ermittelt, (2) die Auswaschung von besonders problematischen Bioziden aus Fassaden quantifiziert und (3) das Belastungsrisiko fur Gewasser mittels Stofftransportmodellierung abgeschatzt. Methoden Acht Biozide wurden untersucht, die in kunstharzgebundenen Fassadenbeschichtungen verwendet werden. Dazu gehoren auch Wirkstoffe, deren Umwelteintrag bisher eher der Landwirtschaft zugerechnet wurde, z. B. Diuron, Carbendazim und Terbutryn. Fur jedes Biozid wurden okotoxikologische Qualitatskriterien fur aquatische Organismen bestimmt. Die Auswaschung von vier Bioziden aus einer verputzten Fassade wurde im Laborversuch unter Berucksichtigung von UV-Bestrahlung untersucht, wobei die Temperatur variiert wurde. Uber 80 Beregnungsintervalle in 28 Tagen wurden Proben des Fassadenabflusses entnommen, die Wirkstoffkonzentrationen gemessen und die ausgewaschenen Wirkstoffmengen berechnet. Basierend auf einem Austragsszenario wurde das mogliche Belastungsrisiko im Gewasser durch das Biozid Cybutryn mit einer Stofftransportmodellierung abgeschatzt. Die ermittelten wirkstoffspezifischen Qualitatskriterien und die Auswaschcharakteristik wurden darin berucksichtigt. Ergebnisse Die akuten und chronischen Kriterien sowie vorhergesagten Konzentrationen ohne Effekt weisen auf eine hohe Okotoxizitat der betrachteten Biozide hin. Die Ergebnisse zum Auswaschungsverhalten von vier Bioziden (Diuron, Terbutryn, Cybutryn und Carbendazim) zeigen, dass die Wirkstoffe im Fassadenabfluss vorkommen und die Belastung unter den gewahlten experimentellen Bedingungen exponentiell abnimmt. Dabei fuhrt eine Temperaturerhohung wieder zu einem Konzentrationsanstieg. Die ausgewaschenen Stoffmengen liegen zwischen 7 % und 29 %. Bereits innerhalb der ersten 15 min wurde mehr als die Halfte der gesamten Stoffmenge wahrend der 60 min Beregnungsdauer ausgewaschen. Die Stofftransportmodellierung zum Eintrag des Biozids Cybutryn aus Fassaden ins Gewasser deutet auf ein hohes Belastungspotential fur kleinere Gewasser hin. Diskussion Die Ergebnisse zur Auswaschung von Bioziden, deren potentielle okotoxische Effekte und Stabilitat in der Umwelt zeigen, dass von einigen Wirkstoffen fur Gewasser ein hohes potentielles Belastungsrisiko, von anderen aber nur ein geringes Risiko ausgehen durfte. Belastetes Fassadenwasser muss fur einige Biozide sehr deutlich durch unbelastetes Regenwasser verdunnt werden, damit die Qualitatskriterien im Gewasser eingehalten werden. Diuron und Carbendazim werden auch in anderen Materialschutzanwendungen verwendet oder in der Landwirtschaft ausgebracht. Cybutryn wird oft als Antifouling-Wirkstoff in Bootsanstrichen eingesetzt, so dass eine Belastung im Gewasser erst unter Berucksichtigung aller Eintragswege beurteilt werden kann. Schlussfolgerungen Kritische Konzentrationsbereiche im Fassadenabfluss sind an neuen Gebaudefassaden zu erwarten, in der Regel vor allem an warmegedammten Fassaden. Angesichts der niedrigen vorhergesagten Konzentrationen ohne Effekt im Bereich von wenigen ng/L und den hohen Anwendungsmengen in Fassaden sollte die Auswaschung und das Umweltverhalten wirkstoffspezifisch abgeschatzt werden. Masnahmen an der Quelle und die jeweils nachhaltigste Regenwasserentsorgung sollten evaluiert werden. Empfehlungen und Ausblick Bei der Beurteilung der Qualitat von Regenwasserabflussen, der Entsorgungswege und Boden- und Gewasserbelastung sollte dem zunehmenden Einsatz von Bioziden und anderen Additiven in Baumaterialien als mogliche Belastungsquelle verstarkt Beachtung geschenkt werden. Ein ganzheitliches Management von Baumaterialien und der Regenwasserbewirtschaftung ist gefordert. Die noch laufenden Labor- und Feldstudien werden weitere Ergebnisse zur Auswaschung von Bioziden und Additiven aus Fassadenfarben und -putzen sowie Dachmaterialien liefern.

There is increasing concern about environmental pollution by diffuse emissions of various environmental hazards emitted by transportation activities. For the first time substances released by railways to the environment were investigated. We considered the significant sources and the amounts emitted by regular operation within the Swiss Federal Railways (SBB) network (7200 km tracks). The main substances are about 2270 t y−1 metals, 1357 t y−1 hydrocarbons and 3.9 t y−1 herbicides. Most of the released metals are particles emitted by friction processes with iron, followed by copper, zinc, manganese, chromium, nickel, vanadium and lead. Only a small amount of metals is expected to be leached in dissolved phase. The emission of hydrocarbons may be diffusive (e.g. operational losses) or at point-sources (e.g. track-switch). The wooden sleepers seem to be the most important sources of hydrocarbons, followed by lubricants from track-switches and wheel flanges. The emissions reflect a spatial and temporal exposure pattern. The assessment is valuable for regulatory authorities working on soil and water protection as well as for railway companies determining their necessity of water and soil protection measures. Based on the results, selected studies may establish an understanding on relevant processes and environmental risk of railway imissions to soil, drainage water and groundwater.

In this study gravity-driven membrane (GDM) ultrafiltration is investigated for the pretreatment of seawater before reverse osmosis (RO). The impacts of temperature (21 ± 1 and 29 ± 1 °C) and hydrostatic pressure (40 and 100 mbar) on dynamic flux development and biofouling layer structure were studied. The data suggested pore constriction fouling was predominant at the early stage of filtration, during which the hydrostatic pressure and temperature had negligible effects on permeate flux. With extended filtration time, cake layer fouling played a major role, during which higher hydrostatic pressure and temperature improved permeate flux. The permeate flux stabilized in a range of 3.6 L/m2 h (21 ± 1 °C, 40 mbar) to 7.3 L/m2 h (29 ± 1 °C, 100 mbar) after slight fluctuations and remained constant for the duration of the experiments (almost 3 months). An increase in biofouling layer thickness and a variable biofouling layer structure were observed over time by optical coherence tomography and confocal laser scanning microscopy. The presence of eukaryotic organisms in the biofouling layer was observed by light microscopy and the microbial community structure of the biofouling layer was analyzed by sequences of 16S rRNA genes. The magnitude of permeate flux was associated with the combined effect of the biofouling layer thickness and structure. Changes in the biofouling layer structure were attributed to (1) the movement and predation behaviour of the eukaryotic organisms which increased the heterogeneous nature of the biofouling layer; (2) the bacterial debris generated by eukaryotic predation activity which reduced porosity; (3) significant shifts of the dominant bacterial species over time that may have influenced the biofouling layer structure. As expected, most of the particles and colloids in the feed seawater were removed by the GDM process, which led to a lower RO fouling potential. However, the dissolved organic carbon in the permeate was not be reduced, possibly because some microbial species (e.g. algae) could convert CO2 into organic substances. To further improve the removal efficiency of the organic carbon, combining carrier biofilm processes with a submerged GDM filtration system is proposed. EDB (Economic Devt. Board, S’pore) Accepted version

Despite their common use in animal production the environmental fate of the veterinary sulfonamide antibiotics after excretion is only poorly understood. We performed irrigation experiments to investigate the transport of these substances with surface runoff on grassland. Liquid manure from pigs treated with sulfadimidine was spiked with sulfadiazine, sulfathiazole, the herbicide atrazine (2-chloro-4-ethyl-amino-6-isopropylamino-1,3,5-triazine), and the conservative tracer bromide and spread onto eight plots. Four plots received the same amounts of the spiked substances in aqueous solution (controls). Apart from the application matrix we varied the time between application and irrigation. Manure increased the runoff volume up to six times compared with the controls. It seemed that manure enhanced the runoff by sealing the soil surface. On manured plots the relative antibiotic concentrations in runoff were higher than on the controls, reaching an average of 0.3% (sulfadiazine), 0.8% (sulfathiazole), and 1.4% (sulfadimidine) of the input concentrations after a 1-d contact time. The corresponding values on the controls were 0.16% for sulfadiazine and 0.08% for sulfathiazole. After 3 d, the maximum values on the manured plots were even higher, whereas they had fallen below the limit of quantification on the controls. As a consequence, the sulfonamide losses were 10 to 40 times larger on the manured plots. The relative mobility of the sulfonamides on the control plots followed the trend expected from their chromatographic separation but the opposite was found on the manured plots. Hence it is important to consider explicitly the physical and chemical effects of manure when assessing the environmental fate of sulfonamides.

Silver nanoparticles (Ag-NP) are increasingly used in consumer products and their release during the use phase may negatively affect aquatic ecosystems. Research efforts, so far, have mainly addressed the application and use of metallic Ag(0)-NP. However, as shown by recent studies on the release of Ag from textiles, other forms of Ag, especially silver chloride (AgCl), are released in much larger quantities than metallic Ag(0). In this field study, we report the release of AgCl-NP from a point source (industrial laundry that applied AgCl-NP during a piloting phase over a period of several months to protect textiles from bacterial regrowth) to the public sewer system and investigate the transformation of Ag during its transport in the sewer system and in the municipal wastewater treatment plant (WWTP). During the study period, the laundry discharged ~85 g of Ag per day, which dominated the Ag loads in the sewer system from the respective catchment (72-95%) and the Ag in the digested WWTP sludge (67%). Combined results from electron microscopy and X-ray absorption spectroscopy revealed that the Ag discharged from the laundry to the sewer consisted of about one third AgCl and two thirds Ag2S, both forms primarily occurring as nanoparticles with diameters100 nm. During the 800 m transport in the sewer channel to the nearby WWTP, corresponding to a travel time of ~30 min, the remaining AgCl was transformed into nanoparticulate Ag2S. Ag2S-NP also dominated the Ag speciation in the digested sludge. In line with results from earlier studies, the very low Ag concentrations measured in the effluent of the WWTP (0.5 μg L(-1)) confirmed the very high removal efficiency of Ag from the wastewater stream (95%).

The main objective of this paper is to carefully study the fields induced in flasks exposed to RF electromagnetic fields. The study focuses on the widely used 60 mm Petri dishes and rectangular T-75 flasks for the two following cases: 1) cells in homogeneous suspension and 2) cell monolayers. The dependence of the coupling and the homogeneity of the SAR distribution on frequency (0.7 GHz to 2.5 GHz), polarization (E, H and k polarizations) and the amount of medium (1.9 mm to 4.7 mm medium height) is studied. In addition, the effects of the environment, meniscus and field impedance as well as the distortion of the incident field are discussed. Based on these results, advantages and disadvantages of different fundamental designs of apparatus used in the past are compared. These are TEM cells, HF chambers, radial transmission lines (RTL), waveguides and wire patch cells. Furthermore, the major optimization parameters are identified for the development of highly optimized exposure systems, enabling the conduct of high quality experiments.

This paper was motivated by a recent article in which the levels of electromagnetic energy absorbed in the heads of mobile phone users were compared for children and adults at the frequencies of 835 MHz and 1,900 MHz. Significant differences were found, in particular substantially greater absorption in children's heads at 835 MHz. These findings contradict other studies in which no significant changes had been postulated. The clarification of this issue is crucial to the mobile communications industry since current SAR evaluations as required by the FCC are only performed with phantoms based on the heads of adults. In order to investigate the differences in absorption between adults and children due to their differing anatomies, simulations have been performed using head phantoms based on MRI scans of an adult (voxel size 2 x 2 x 1 mm3) and two children (voxel size 2 x 2 x 1.1 mm3) of the ages of 3 and 7 y. Ten different tissue types were distinguished. The differences in absorption were investigated for the frequencies of 900 MHz and 1,800 MHz using 0.45 lambda dipoles instead of actual mobile phones. These well-defined sources simplified the investigation and facilitated the comparison to previously published data obtained from several numerical and experimental studies on phantoms based on adults. All simulations were performed using a commercial code based on the finite integration technique. The results revealed no significant differences in the absorption of electromagnetic radiation in the near field of sources between adults and children. The same conclusion holds when children are approximated as scaled adults.

This paper presents an exposure setup designed for in vivo studies of possible effects on the central nervous system due to the electromagnetic exposure from handheld mobile communications equipment. The setup consists of a carousel on which 10 rats, each restrained in a radially positioned tube, are exposed to the electromagnetic field emanating from a dipole antenna at the center. The rats are positioned with their snouts at a distance of 35 mm from the dipole antenna. The tubes restrain the movement of the animals to such an extent as to allow for well defined exposure conditions, yet without totally immobilizing them. Numerical and experimental dosimetric analysis of the setup was conducted using rats weighing 250-300 g at a frequency of 900 MHz. A detailed rat phantom derived from MRI scans was developed for the numerical assessment with a commercially available code based on the finite integration technique. The results were validated by measurements of the temperature rise in selected points of a rat cadaver. The dosimetric analysis shows that the setup is eminently suitable for central nervous system studies. It enables well defined field strengths to be induced in the brain tissue, whereby the variations in the specific absorption rate averaged over the brain tissue caused by movement and varying animal sizes was shown to be less than +/-16%. The specific absorption rate distribution in the brain is nonhomogeneous but comparable to that induced in the brain of a human using a handheld wireless phone. The efficiency of the exposure is about 0.20+/-0.05 mW g(-1) for the brain average value per 100 mA feedpoint current. The whole-body average specific absorption rate is considerably lower, i.e., about half of that of the brain averaged value. In addition, the setup has been proven to be practical in use, and the stress levels caused by restraining the animals in this setup are deemed by neurologists and veterinary scientists to be very low.

The community of agent researchers and engineers has produced a number of interesting and mature results. However, agent technology is still not widely adopted by industrial software developers or software companies--possibly because existing frameworks are infused with academic premises that rarely apply to industrial settings. In this paper, we analyse the requirements of current industry-driven software projects and show how we are able to cope with these requirements in the Java Intelligent Agent Componentware agent framework, JIACi¾źV. We argue that the lack of industry-grade requirements and features in other agent frameworks is one of the reasons for the slow acceptance of agent technology in the software industry. The JIACi¾źV framework tries to bridge that gap--not as a final solution, but as a stepping stone towards industrial acceptance.

The dependence of electromagnetic energy absorption at 900 MHz in the human head on its anatomy and its modeling are investigated for RF-sources operating in the very close proximity of the head. Different numerical head phantoms based on MRI scans of 3 different adults were used with voxel sizes down to 1 mm/sup 3/. Simulations of the absorption were performed by distinguishing the electrical properties of up to 13 tissue types. In addition simulations with modified electric parameters and reduced degrees of complexity were performed. Thus, the phantoms greatly differ from each other in terms of shape, size, and internal anatomy. The numerical results are compared with those of measurements in a multitissue phantom and 2 homogeneous phantoms of different shapes and sizes. The results demonstrate that size and shape are of minor importance, Although local SAR values depend significantly on local inhomogeneities and electric properties, the volume-averaged spatial peak SAR obtained with the homogeneous phantoms only slightly overestimates that of the worst-case exposure in the inhomogeneous phantoms.

A broadband calibration procedure for E-field probes that minimizes the overall uncertainties inherent in E-field measurements in lossy dielectric liquids has been developed. The analysis of the calibration requirements shows that probes that are symmetrical with respect to their axis greatly facilitate accurate calibration, since the calibration procedure can be divided into several discrete steps. Such a procedure is presented and analyzed with respect to its uncertainties. Absolute calibration is performed at three frequency bands utilized in Europe for mobile communications (450 MHz, 900 MHz, and 1.8 GHz) and in different tissue-simulating liquids. The parameters obtained are verified by numerical simulations of the probe in the surrounding media. Such simulations allow the assessment of some of the calibration parameters with sufficient accuracy in cases where the experimental determination would be too tedious and time consuming.

The SeMa2 software module is a hybrid semantic service matchmaker based on OWL-S service descriptions and SWRL rules that participated in the S3 Contests 2008–2010. It provides syntactical as well as semantical matching techniques. Besides classifying input and output parameters it offers an approach to precondition and effect rule matching and reasoning. In this chapter we describe the architecture and the workflow of our approach and the results that have been evaluated during the last S3 Contest and with experimental test runs. Finally, we discuss the benefits and drawbacks of our implementation and propose future steps on our work.

The European Biocidal Products Directive 98/8/EC requires a risk assessment concerning possible effects of active ingredients on the environment. Biocides can be leached from treated materials exposed to outdoor use. These emissions have to be estimated and evaluated during the authorization procedure. Different immersion and irrigation tests were performed to investigate leaching of biocides from facade coatings. Several marketed formulations of textured coatings and paints spiked with a mixture of commonly used active ingredients (OIT, DCOIT, IPBC, carbendazim, isoproturon, diuron, terbutryn, and Irgarol 1051) were investigated. The emission process can be described by time-dependent functions that depend on the test conditions. The results of all test procedures confirm that leachability is related to water solubility and n-octanol-water partition coefficient of the active ingredients and that leaching of biocides from facade coatings is mainly a diffusion controlled process. Other factors like the composition of the product, availability and transport of water, concentration of active ingredients in the coatings, as well as UV-exposure of the coatings influence biocide emissions.

We present direct evidence of the release of synthetic nanoparticles from urban applications into the aquatic environment. We investigated TiO(2) particles as these particles are used in large quantities in exterior paints as whitening pigments and are to some extent also present in the nano-size range. TiO(2) particles were traced from exterior facade paints to the discharge into surface waters. We used a centrifugation based sample preparation which recovers TiO(2) particles between roughly 20 and 300nm. Analytical electron microscopy revealed that TiO(2) particles are detached from new and aged facade paints by natural weather conditions and are then transported by facade runoff and are discharged into natural, receiving waters. Microscopic investigations are confirmed by bulk chemical analysis. By combining results from microscopic investigations with bulk chemical analysis we calculated the number densities of synthetic TiO(2) particles in the runoff.

To prevent residues of veterinary medicinal products (VMPs) from contaminating surface waters and ground water, an environmental impact assessment is required before a new product is allowed on the market. Physically based simulation models are advocated for the calculation of predicted environmental concentrations at higher tiers of the assessment process. However, the validation status of potentially useful models is poor for VMP transport. The objective of this study was to evaluate the dual-permeability model MACRO for simulation of transport of sulfonamide antibiotics in surface runoff and soil. Special focus was on effects of solute application in liquid manure, which may alter the hydraulic properties at the soil surface. To this end we used data from a microplot runoff experiment and a field experiment, both conducted on the same clay loam soil prone to preferential flow. Results showed that the model could accurately simulate concentrations of sulfadimidine and the nonreactive tracer bromide in runoff and in soil from the microplot experiments. The use of posterior parameter distributions from calibrations using the microplot data resulted in poor simulations for the field data of total sulfadimidine losses. The poor results may be due to surface runoff being instantly transferred off the field in the model, whereas in reality re-infiltration may occur. The effects of the manure application were reflected in smaller total and micropore hydraulic conductives compared with the and micropore hydraulic conductivities compared with the application in aqueous solution. These effects could easily be accounted for in regulatory modeling.

There is increasing concern about diffuse pollution of aquatic systems by biocides used in urban areas. We investigated sources and pathways of biocides significant for the pollution of storm water runoff. Main sources seem to be building envelopes, i.e. facades (paints, plasters) and roof sealing membranes. First results from a defined urban catchment drained by a separated sewer system without any agricultural activities reveal a substantial occurrence. Even after the first flush, concentrations of terbutryn, carbendazim, mecoprop as well as Irgarol 1051® and its metabolite exceeded the Swiss water quality standard of 0.1 μg/L. In laboratory experiments, leaching of mecoprop used as a root protection agent in bitumen sheets for roof waterproofing was determined. The concentrations differed in 16 different sheets two orders of magnitude, depending on the product composition. Using optimized products, it is expected to be the most efficient and sustainable way to reduce the environmental impact. To understand transport dynamics and environmental risk, further storm water events will be analyzed. Based on the ongoing project URBIC, first measures will be proposed to limit the release to surface and ground water.

Despite the concern raised by the detections of veterinary antibiotics like sulfonamides (SA) in the environment, their fate in soils is still not sufficiently understood. In a previous article, we demonstrated that manure may substantially influence losses of SA via runoff from soils. Here, we report on the effect of manure on SA availability in soil pore water. Three sulfonamides (sulfadimidine, sulfadiazine, sulfathiazole) and two tracers (bromide and Brilliant Blue) were either applied in manure or as aqueous solution on grassland plots. After 1 and 3 d contact time, the plots were irrigated with deionized water. One day after irrigation, soil cores were taken and profiles of pore water concentrations were determined. The median SA concentrations of the top layer on manured plots varied between 40 and 60 microg L(-1) and between 10 and 30 microg L(-1) on the controls. For the conservative tracer Br the mass recovery was about 60 to 75% and much lower for the SA (2 to 14%). Apparent distribution coefficients K(d,app) of the SA in the topsoil ranged between 3 and 15 L kg(-1) on the manured plots and between 30 to 35 kg L(-1) on the controls. Below the top layer, the concentration distribution showed a pattern typical for preferential flow. Locally, SA concentrations down to 30- to 50-cm depth were as high as in the top 5 cm with little effect of the two application matrices. In the topmost layer, the data indicate that 10 to 25% of sulfadimidine were transformed to its acetyl-metabolite.

Precise evaluation of the near-field generated by transmitters operating in the radio frequency (RF) range (30 MHz to 6 GHz) is still an engineering challenge not only requiring sophisticated tools but also involving different procedures with a multitude of parameters to be considered. This paper reviews the state-of-the-art of near-field evaluation with emphasis on compliance testing of handheld RF transmitters with safety limits Similar tools and techniques can be utilized for the analysis and optimization of antennas operating in complex environments as well as for evaluation of special electromagnetic compatibility and interference problems occurring in the near-field of transmitters. Another area of applications is the analysis, evaluation and optimization of exposure setups used in RF safety research to investigate possible basic, therapeutic or adverse health effects from non-ionizing radiation.

Crawford TEM cells are often used to expose cell cultures or small animals in order to study the effects caused by high-frequency fields. They are self-contained, easy-to-use setups that provide a rather homogeneous field distribution in a large area around its center, corresponding approximately to far-field conditions. However, a number of conditions must be met if such TEM cells are intended to be used for in vitro experiments. For instance, poor interaction with the incident field must be maintained to avoid significant field disturbances in the TEM cell. This is best achieved with E-polarization, i.e., when the E-field vector is normal to the investigated cell layer lining the bottom of a synthetic Petri dish. In addition, E-polarization provides the most homogeneous field distribution of all polarizations within the entire layer of cells. In this paper, we present a detailed dosimetric assessment for 60 and 100 mm Petri dishes as well as for a 48-well titer plate at 835 MHz. The dosimetry was performed by using numerical computations. The modeling and the simplifications are validated by a second numerical technique and by experimental measurements. For thin liquid layers, an approximation formula is provided with which the induced field strength for many other experiments conducted in Petri dishes can be assessed reliably.