The influence of dissolved and surface-bound humic acid on the toxicity of TiO₂ nanoparticles to Chlorella sp

NOM is likely to coat TiO₂ nanoparticles (nano-TiO₂) discharged into the aquatic environment and influence the nanotoxicity to aquatic organisms, which however has not been well investigated. This study explored the influence of nanoparticle surface-bound humic acid (HA, as a model NOM) as well as dissolved HA on the toxicity of nano-TiO₂ to Chlorella sp., with a specific focus on adhesion of the nanoparticles to the algae. Results showed that nano-TiO₂ and the dissolved HA could inhibit the algal growth with an IC₅₀ of 4.9 and 8.4 mg L⁻¹, respectively, while both dissolved and nanoparticle surface-bound HA could significantly alleviate the algal toxicity of nano-TiO₂. IC₅₀ of nano-TiO₂ increased to 18 mg L⁻¹ in the presence of 5 mg L⁻¹ of the dissolved HA and to 48 mg L⁻¹ as the result of surface-saturation by HA. Co-precipitation experiment and transmission electron microscopy observation revealed that both dissolved and nanoparticle surface-bound HA prevented the adhesion of nano-TiO₂ to the algal cells due to the increased electrosteric repulsion. The generation of intracellular reactive oxygen species (ROS) was significantly limited by the dissolved and nanoparticle surface-bound HA. The prevention of adhesion and inhibition of ROS generation could account for the HA-mitigated nanotoxicity.     

The influence of capsular extracellular polymeric substances on the interaction between TiO₂ nanoparticles and planktonic bacteria

The role of capsular extracellular polymeric substances (EPS) at the surface of planktonic microorganisms was investigated for possible toxicity mitigation from titanium dioxide (TiO₂) nanoparticles, using variable EPS producing wild-type and isogenic mutant strains of Pseudomonas aeruginosa. Membrane integrity assays revealed that increased capsular EPS reduced cell membrane damage. Acting as a barrier to the cell membrane, capsular EPS permitted attachment of nanoparticles to the cell, while simultaneously delaying cellular damage caused by the production of reactive oxygen species (ROS). Modulations in ROS production were monitored in situ; while changes in the chemical composition of the microorganisms before and after exposure were examined with Fourier transform infrared spectroscopy (FTIR). The addition of methanol, a known radical scavenger, was shown to vastly reduce ROS production and membrane integrity losses, while not affecting physical interactions of nanoparticles with the microorganism. The results support that EPS provides an attachment site for nanoparticles, but more importantly act as a barrier to cell membrane oxidation from ROS. These observations provide better understanding of the overall importance of ROS in TiO₂ microbial toxicity.     

An analysis of sustainable development and environmental protection in postcommunist countries: the case of croatia‐a view point

The paper analyses the origins, the definitions, and the implementation of sustainable development in the post‐communist countries of Central and Eastern Europe, using Croatia as an example. The overview of events in environmental concern world‐wide, in the last 25 years, shows that there is evidence of fast changes which have left the former communist countries behind. The major concern of the paper is the lack of an agreed upon definition and criteria on what sustainable development actually represents, and why it is still an odd subject in the Central and Eastern European region. Five recognition criteria described in the open literature are compared with the situation in the region. Using the examples of implementation of new UN Conventions, accepted at the UNCED Conference in Rio de Janeiro in 1992, the paper discusses the shortcomings and obstacles to current policies of sustainability.     

News from the field: Visual planning and urbanism in the mid‐twentieth century conference,Newcastle, UK, 11–13 September 2007

Gjirokastra, a century-old small city in southern Albania (now a UNESCO World Heritage site), provides an outstanding example of a Classical and Late Ottoman urban centre. At the same time, it is a special example of urban and architectural design based on self-defence by individual family units. Through an excursion of Gjirokastra's residential neighbourhoods, this article discusses how defence concerns guided its urban morphology and building typology until the collapse of the Ottoman Empire. The idea of war, feuds, and fear has pervaded the residents' self-identity for centuries. The military character of their houses owes much to the local ‘warrior’ mentality that prevailed in times of war and peace.     

Is there a risk associated with the insect repellent DEET (N,N-diethyl-m-toluamide) commonly found in aquatic environments?

DEET (N,N-diethyl-m-toluamide) is the active ingredient of most commercial insect repellents. This compound has commonly been detected in aquatic water samples from around the world indicating that DEET is both mobile and persistent, despite earlier assumptions that DEET was unlikely to enter aquatic ecosystems. DEET's registration category does not require an ecological risk assessment, thus information on the ecological toxicity of DEET is sparse. This paper reviews the presence of DEET in aqueous samples from around the world (e.g. drinking water, streams, open seawater, groundwater and treated effluent) with reported DEET concentrations ranging from 40-3000 ng L(-1). In addition, new DEET data collected from 36 sites in coastal waterways from eastern Australia (detections ranging from 8 to 1500 ng L(-1)) are examined. A summary of new and existing toxicity data are discussed with an emphasis on preparing a preliminary risk assessment for DEET in the aquatic environment. Collated information on DEET in the aquatic environment suggests risk to aquatic biota at observed environmental concentrations is minimal. However, the information available was not sufficient to conduct a full risk assessment due to data deficiencies in source characterisation, transport mechanisms, fate, and ecotoxicity studies. These risks warrant further investigation due to the high frequency that this organic contaminant is detected in aquatic environments around the world.     

Chromium speciation in tannery effluent—I. An assessment of techniques and the role of organic Cr(III) complexes

Three methods of chromium speciation were assessed in relation to possible interferences from Cr(III)-organic complexes. They were, namely: 1,5-diphenyl-carbazide (DPC) spectrophotometry, organic extraction with methyl isobutyl ketone (MIBK) and co-precipitation with iron and bismuth salts. Initially, a number of organic ligands, i.e. proteins, amino acids and organic acids were reacted with Cr(III) and only those complexes with solubility levels above that of ionic Cr(III) were assessed further. The spectrophotometric method was found to suffer minor interferences which were attributable to a non-specific turbidity effect. In comparison, two methods of MIBK extraction were found to suffer severe interferences with Cr(III)-protein complexes. Also, co-precipitation with iron salts resulted in high levels of contamination by Cr(III)-organic complexes in the ionic chromium fractions. Due to the poor solubility of bismuth salts, this method was discarded. The results demonstrate that chromium speciation in the presence of organic complexes can lead to erroneous results. However, with recognition of the presence of such complexes, corrections can be made. Since the co-precipitation behaviour of organic Cr(III) appears to be relatively specific, a scheme is described for the speciation of Cr(III) in tannery contaminated waterways. In addition, it is recommeded that a separate determination of Cr(VI) is conducted using a modification of the DPC method.     

Synergistic effect of nickel ions on the coupled dechlorination of trichloroethylene and 2,4-dichlorophenol by Fe/TiO₂ nanocomposites in the presence of UV light under anoxic conditions

The coupled removal of priority pollutants by nanocomposite materials has recently been receiving much attention. In this study, trichloroethylene (TCE) and 2,4-dichlorophenol (DCP) in aqueous solutions were simultaneously removed by Fe/TiO₂ nanocomposites under anoxic conditions in the presence of nickel ions and UV light at 365 nm. Both TCE and DCP were effectively dechlorinated by Fe/TiO₂ nanocomposites, and the pseudo-first-order rate constants (k_obs) for TCE and DCP dechlorination were (1.39 ± 0.05)×10⁻² and (1.08 ± 0.05)×10⁻² h⁻¹, respectively, which were higher than that by nanoscale zerovalent iron alone. In addition, the k_obs for DCP dechlorination was enhanced by a factor of 77 when Fe/TiO₂ was illuminated with UV light for 2 h. Hydrodechlorination was found to be the major reaction pathway for TCE dechlorination, while DCP could undergo reductive dechlorination or react with hydroxyl radicals to produce 1,4-benzoquinone and phenol. TCE was a stronger electron acceptor than DCP, which could inhibit the dechlorination efficiency and rate of DCP during simultaneous removal processes. The addition of nickel ions significantly enhanced the simultaneous photodechlorination efficiency of TCE and DCP under the illumination of UV light. The k_obs values for DCP and TCE photodechlorination by Fe/TiO₂ in the presence of 20-100 μM Ni(II) were 30.4-136 and 13.2-192 times greater, respectively, when compared with those in the dark. Electron spin resonance analysis showed that the photo-generated electron-hole pairs could be effectively separated through Ni ions cycling, leading to the improvement of electron transfer efficiency of TCE and DCP by Fe/TiO₂.     

Space–time clustering of seismic events and hazard assessment in the Zabrze-Bielszowice coal mine,Poland

The results of the statistical analysis of seismic activity recorded in the “Zabrze-Bielszowice” coal mine in Poland are presented in this article. The monitoring was conducted by a small network consisting of four triaxial geophones deployed in vertical holes in the roof. For over 1000 seismic events recorded during the two month's experiment, the location of sources was realized. The seismic sources were mostly located ahead of the active face of the longwall. Since the first day of the monitoring, cluster analysis was sequentially performed for increasing number of sources. At the end of the experiment, 31 clusters were identified. They consisted of different numbers of events and were separated in space. About 40% of the events were not included in the clusters. For each large cluster, hazard analysis was separately performed. The hazard function evaluated for the largest cluster was compared with hypocenters of high energy tremors (E>1000 J) recorded by the geophones in that area. For some cases, recorded tremors occurred after an abrupt decrease of hazard function, but only one of them was located in the vicinity of the appropriate cluster. We concluded that for the analyzed cluster, a correlation between evaluated hazard function and time occurrences of the high energy tremors existed. Except for one case, there is no space correlation between analyzed clusters and high energy tremors.     

Paradigm of mediocrity: poverty and risk accumulation in urban Africa – the case of Korle Gonno,Accra

This paper examines how poverty has developed in Korle Gonno, an indigenous Ga community in Accra, Ghana, as a concrete challenge. This challenge has gone unnoticed until recently, though several informal studies exist in Ghana. By problematizing vulnerability, the literature is examined within Accra’s development dynamics. Through extensive fieldwork, the results show a socially stratified and highly dependent community experiencing vulnerabilities and the residents’ diverse coping strategies. Drawing upon the empirical data, it is argued that the lack of recognition of urban poverty (i.e., the raison d’être of slum) means many continue to be exposed to health risks. The paper concedes that the problem demands a multifaceted solution that includes more subjective issues like vulnerability and social exclusion, and objective ones like good urban governance and power relations. Failure to do so can lead to a downward spiral into extreme poverty that can affect the entire society.     

Large-eddy simulation of the containment failure in isolation rooms with a sliding door—An experimental and modelling study

In hospital isolation rooms, door operation can lead to containment failures and airborne pathogen dispersal into the surrounding spaces. Sliding doors can reduce the containment failure arising from the door motion induced airflows, as compared to the hinged doors that are typically used in healthcare facilities. Such airflow leakage can be measured quantitatively using tracer gas techniques, but detailed observation of the turbulent flow features is very difficult. However, a comprehensive understanding of these flows is important when designing doors to further reduce such containment failures. Experiments and Computational Fluid Dynamics (CFD) modelling, by using Large-Eddy Simulation (LES) flow solver, were used to study airflow patterns in a full-scale mock-up, consisting of a sliding door separating two identical rooms (i.e. one isolation room attached to an antechamber). A single sliding door open/ hold-open/ closing cycle was studied. Additional variables included human passage through the doorway and imposing a temperature difference between the two rooms. The general structures of computationally-simulated flow features were validated by comparing the results to smoke visualizations of identical full-scale experimental set-ups. It was found that without passage the air volume leakage across the doorway was first dominated by vortex shedding in the wake of the door, but during a prolonged hold-open period a possible temperature difference soon became the predominant driving force. Passage generates a short and powerful pulse of leakage flow rate even if the walker stops to wait for the door to open.     

Comparative risk assessment of residential radon exposures in two radon-prone areas, ?tei (Romania) and Torrelodones (Spain)

Radon and radon progeny are present indoors, in houses and others dwellings, representing the most important contribution to dose from natural sources of radiation. Most studies have demonstrated an increased risk of lung cancer at high concentration of radon for both smokers and nonsmokers. The work presents a comparative analysis of the radon exposure data in the two radon-prone areas, ?tei, Transylvania, (Romania), in the near of old Romanian uranium mines and in the granitic area of Torrelodones town, Sierra de Guadarrama (Spain). Measurements of indoor radon were performed in 280 dwellings (Romania) and 91 dwellings (Spain) by using nuclear track detectors, CR 39. The highest value measured in ?tei area was 2650 Bq m^− 3 and 366 Bq m^− 3 in the Spanish region. The results are computed with the BEIR VI report estimates using the age-duration model at an exposure rate below 2650 Bq m^− 3. We used the EC Radon Software to calculate the lifetime lung cancer death risks for individuals groups in function of attained age, radon exposures and tobacco consumption. A total of 233 lung cancer deaths were observed in the ?tei area for a period of 13 years (1994-2006), which is 116.82% higher than expected from the national statistics. In addition, the number of deaths estimated for the year 2005 is 28, which is worth more than 2.21 times the amount expected by authorities. In comparison, for Torrelodones was rated a number of 276 deaths caused by lung cancer for a period of 13 years, which is 2.09 times higher than the number expected by authorities. For the year 2005 in the Spanish region were reported 32 deaths caused by pulmonary cancer, the number of deaths exceeding seen again with a factor of 2.10 statistical expectations. This represents a significantly evidence that elevated risk can strongly be associated with cumulated radon exposure.     

Does office space occupation matter? The role of the number of persons per enclosed office space,psychosocial work characteristics,and environmental satisfaction in the physical and mental health of employees

The study examined the effects of office space occupation, psychosocial work characteristics, and environmental satisfaction on physical and mental health of office workers in small‐sized and open‐plan offices as well as possible underlying mechanisms. Office space occupation was characterized as number of persons per one enclosed office space. A total of 207 office employees with similar jobs in offices with different space occupation were surveyed regarding their work situation (psychosocial work characteristics, satisfaction with privacy, acoustics, and control) and health (psychosomatic complaints, irritation, mental well‐being, and work ability). Binary logistic and linear regression analyses as well as bootstrapped mediation analyses were used to determine associations and underlying mechanisms. Employee health was significantly associated with all work characteristics. Psychosocial work stressors had the strongest relation to physical and mental health (OR range: 1.66–3.72). The effect of office space occupation on employee health was mediated by stressors and environmental satisfaction, but not by psychosocial work resources. As assumed by sociotechnical approaches, a higher number of persons per enclosed office space was associated with adverse health effects. However, the strongest associations were found with psychosocial work stressors. When revising office design, a holistic approach to work (re)design is needed.     

An early engagement with town planning: Māori and the Commission to inquire and report upon the necessity or advisability of establishing model villages on the sites of the present villages of Ohinemutu and Whakarewarewa in 1926

The history of state-sanctioned planning is generally urban and commences in the early twentieth century. It is a history in which Indigenous people remain relatively invisible until the 1980s. By the 1920s, New Zealand’s Indigenous people, Māori, despite having lost much of their land, remained a visible presence in society. In Rotorua, the traditional Māori villages of Ohinemutu and Whakarewarewa were central to the tourism industry, and were sites of important economic activity for Ngati Whakaue and Tūhourangi. In 1926, Ngati Whakaue and Tūhourangi took an active part in a Commission of Inquiry into the housing in their villages, in an attempt to improve their liveability. The Commission sought to apply town planning principles to their work at a time when town planning legislation had only recently been introduced. This appears to be an early involvement of Indigenous people with town planning and an important part of New Zealand’s planning history.     

Occurrence and fate of the angiotensin II receptor antagonist transformation product valsartan acid in the water cycle – A comparative study with selected β-blockers and the persistent anthropogenic wastewater indicators carbamazepine and acesulfame

The substantial transformation of the angiotensin II receptor antagonist valsartan to the transformation product 2′-(2H-tetrazol-5-yl)-[1,1′-biphenyl]-4-carboxylic acid (referred to as valsartan acid) during the activated sludge process was demonstrated in the literature and confirmed in the here presented study. However, there was a severe lack of knowledge regarding the occurrence and fate of this compound in surface water and its behavior during drinking water treatment. In this work a comparative study on the occurrence and persistency of valsartan acid, three frequently used β-blockers (metoprolol, atenolol, and sotalol), atenolol acid (one significant transformation product of atenolol and metoprolol), and the two widely distributed persistent anthropogenic wastewater indicators carbamazepine and acesulfame in raw sewage, treated wastewater, surface water, groundwater, and tap water is presented. Median concentrations of valsartan acid in the analyzed matrices were 101, 1,310, 69, <1.0, and 65 ng L⁻¹, respectively. Treated effluents from wastewater treatment plants were confirmed as significant source. Regarding concentration levels of pharmaceutical residues in surface waters valsartan acid was found just as relevant as the analyzed β-blockers and the anticonvulsant carbamazepine. Regarding its persistency in surface waters it was comparable to carbamazepine and acesulfame. Furthermore, removal of valsartan acid during bank filtration was poor, which demonstrated the relevance of this compound for drinking water suppliers. Regarding drinking water treatment (Muelheim Process) the compound was resistant to ozonation but effectively eliminated (≥90%) by subsequent activated carbon filtration. However, without applying activated carbon filtration the compound may enter the drinking water distribution system as it was demonstrated for Berlin tap water.     

Are multimodal travelers more satisfied with their lives? A study of accessibility and wellbeing in the Denver,Colorado metropolitan area

In this study, we ask how the ability to use multiple transportation options affects one's subjective wellbeing (SWB), including aspects such as physical health, financial security, standard of living, and personal relationships. A clearer understanding of these associations can inform investments in multimodal infrastructure. We draw on 232 surveys from a diverse set of residents in the Denver, Colorado metropolitan area and find that having more transportation choices can improve standard of living for low- and middle-income residents. Multimodal middle-income residents are also more satisfied with their health and what they are achieving in life. Vehicle owners report higher levels of satisfaction with their standard of living, health, and achievements, compared to non-owners, unless auto is their only travel mode. Only low-income respondents had significant differences in standard of living by where they lived, with greatest satisfaction in the urban core. These results confirm the relationship between public transit and SWB, and contribute to our understanding of how the concept of motility (social and spatial mobility) shapes one's quality of life. The findings have implications for investments in transportation modes across neighborhood types and populations, so that people have a range of travel options to meet their needs and increase their satisfaction with their goals through improved daily travel.