Combined toxicity effects of MTBE and pesticides measured with Vibrio fischeri and Daphnia magna bioassays

Methyl-tert-butyl ether (MTBE), a fuel oxygenate that is added to gasoline, commonly contaminates aquatic systems, many of which are already contaminated with pesticides. The toxic effects (EC(50) value) of several pure pesticides (Diuron, Linuron, Dichlofluanid, Sea nine, Irgarol and tributyltin (TBT)) were measured and compared with the EC(50) value of the pesticide mixed with MTBE, using the Vibrio fischeri and Daphnia magna acute toxicity assays. The interaction between chemicals was evaluated in terms of the effects of mixing on the EC(50) value (i.e. the concentration (mg/L) of a compound or mixture that is required to produce a 50% change in a toxic response parameter) and the time required to generate the toxic response. Presence of MTBE enhanced the EC(50) value of several pesticides (Diuron, Dichlofluanid, TBT and Linuron) and/or the toxic response manifested more rapidly than with pure pesticides. Toxicity enhancements were quite substantial in many cases. For example, the presence of MTBE increased the toxicity of Diuron by more than 50% when tested with the V. fischeri assay (5, 15 and 30 min exposure). Also, the toxic response manifested itself within 5 min whereas without the MTBE the same response arose in 30 min. Presence of MTBE increased the toxicity of Dichlofluanid by 30% when measured with the D. magna assay. Toxicities of only two pesticides (Sea nine and Irgarol) were not raised by the presence of MTBE.     

Effect of river water, sediment and time on the toxicity and bioavailability of molinate to the marine bacterium Vibrio fischeri (Microtox)

The toxicity and bioavailability of molinate to Vibrio fischeri (Microtox((R))) were determined in both laboratory and river water in the absence and presence of sediment after 0, 24, 48, 72 and 96-h exposure. The bioavailability of molinate, expressed as 5min EC50s (bioluminescence) and their fiducial limits calculated using initial measured concentrations, to V. fischeri in laboratory water in the absence and presence of sediment ranged from 1.8 (1.7-2.1) to 3.6 (3.5-3.7) mgL(-1) and 1.3 (1.2-1.4) to 4.2 (3.5-4.5) mgL(-1), respectively. The corresponding values in river water and river water plus sediment were 1.7 (1.6-1.8) to 3.8 (3.6-4.1) and 1.3 (1.3-1.4) to 4.6 (4.2-4.9) mgL(-1), respectively. River water did not significantly (P>0.05) reduce the bioavailability of molinate to V. fischeri compared to that of laboratory water. However, the presence of sediment significantly (P<0.05) reduced the bioavailability of molinate to V. fischeri in both waters. The exposure time also significantly (P<0.05) reduced the bioavailability of molinate to V. fischeri in both waters in the presence and absence of sediment. The type of water did not significantly (P>0.05) affect the loss of molinate during the 96-h exposure period. However, the presence of sediment significantly (P<0.01) increased the loss of molinate from the test solutions, probably by binding to the sediment particles. Exposure period and concentration levels significantly (P<0.05) affected the loss of the herbicides over the 96h.     

The performance of national housing systems a three‐nation comparison

Comparative housing analysis has so far devoted little attention to assessing the performance of national housing systems. The paper argues that more rigorous means of making such assessments are required, not least as an aid to policy making. This in turn means that more explicit statements of housing objectives need to be worked out in order to identify agreed judgemental criteria. The term ‘housing problem’ also requires a more comprehensive definition which recognises that the provision of adequate and accessible housing is a crucial infrastructural benefit to local economies. One way to compare the performance of housing arrangements is to analyse the provision response when rapid employment growth and restructuring produce especial pressures in an area. Using a three‐dimensional conceptual model, the paper presents findings on the extent to which housing provision in three areas, parts of Berkshire, Toulouse and Stockholm, has coped with the rapid employment growth and change of the 1980s. The Swedish and French systems appear to have coped better than the British. On the basis of these empirical findings, the paper finally proposes one possible set of housing objectives.     

The acute toxicity of pulse-dosed, para-substituted phenols to larval American flagfish (Jordanella floridae): a comparison with toxicity to photoluminescent bacteria and predicted toxicity using log Kow

The acute toxicity of nine para-substituted phenols was determined using a pulse-exposure testing protocol and 8-day-old larval American flagfish (Jordanella floridae). Relative tolerance was assessed by determining the 2-h pulse exposure concentration causing 20 and 50% mortality (PE LC20 and PE LC50) over the subsequent 94 h. Four bioassays were run for each phenol and yielded the following mean PE LC20 values (mg 1(-1)) in descending order of toxicity: p-aminophenol, 0.06; hydroquinone, 0.13; phenol, 0.70; p-nitrophenol, 0.81; p-cyanophenol, 3.0; p-chlorophenol, 3.3; p-hydroxyacetophenone, 4.2; p-hydroxybenzyl alcohol, 6.4; and p-hydroxybenzoic acid, 170. These toxicities did not correlate significantly with either previously reported toxicity values for the photoluminescent bacteria Photobacterium phosphoreum, or with the log octanol-water partition coefficient. For some of the compounds, however, sensitivities were quite close to previously reported rainbow trout chronic no-observed-effect concentrations based on continuous exposure. Caution is urged with respect to applying "low-level" biota techniques or simple quantitative structure-activity correlations such as Kow when attempting to predict the toxicity of specific chemicals to fish.     

Photodegradation study of three dipyrone metabolites in various water systems: identification and toxicity of their photodegradation products

The photochemical behaviour of three relevant metabolites of the analgesic and antipyretic drug dipyrone, 4-methylaminoantipyrine (4-MAA), 4-formylaminoantipyrine (4-FAA) and 4-acetylaminoantipyrine (4-AAA), was evaluated under simulated solar irradiation (Suntest system). For 4-MAA, different aqueous solutions (synthetic seawater, freshwater and Milli-Q water) as well as different operational conditions were compared. According to the experimental results, 4-MAA resulted as being an easily degraded molecule by direct photolysis, with half-life times (t1/2) ranging from 0.12 to 0.58 h, depending on the irradiation conditions. Faster degradation was observed in synthetic waters, suggesting that the photolysis was influenced by the salt composition of the waters. However, no effect on the degradation rate was observed by the presence of natural photosensitizers (dissolved organic matter, nitrate ions). 4-FAA and 4-AAA showed slower photodegradation kinetics, with t1/2 of 24 and 28 h, respectively. A study of photoproduct identification was carried out by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS) (ESI positive mode), which allowed us to propose a tentative photodegradation pathway for 4-MAA and the identification of persistent by-products in all the cases. Finally, the application of an acute toxicity test (Daphnia magna) showed an increase in toxicity during the photolytic process, a consequence of the formation of toxic photoproducts.     

Assessing productivity changes in water companies: a comparison of the Luenberger and Luenberger-Hicks-Moorsteen productivity indicators

ABSTRACT

Interest in evaluating productivity changes in water companies has increased in recent years. In this paper, for the first time, we employ the Luenberger-Hicks-Moorsteen Productivity Indicator (LHMPI) to evaluate productivity changes in a sample of Chilean water companies from 2010 to 2016. Productivity change estimations obtained by both the Luenberger Productivity Indicator (LPI) and the LHMPI are compared. Moreover, both indicators were computed assuming constant and variable returns to scale technologies. The LHMPI estimates illustrate that productivity in Chilean water companies has slightly improved over the period studied due to the positive trend of outputs, whereas the inputs negatively contributed to productivity changes. Results from the empirical analysis enabled us to verify that the LHMPI and LPI (and their drivers) are statistically different. This conclusion illustrates that water regulators need to pay attention to the indicators used when assessing productivity changes in water companies.     

Assessing contamination levels of Laguna Lake sediments (Philippines) using a contact assay with zebrafish (Danio rerio) embryos

The present study investigated the suitability of a sediment contact assay using zebrafish (Danio rerio) embryos to evaluate the degree of lake sediment contamination. As endpoints, developmental parameters (mortality, abnormality, heart rate, and hatching rate) as well as stress protein responses (hsp 70 levels) in the developing embryos were recorded during a 96-h exposure. Fertilized zebrafish eggs were exposed to both the whole as well as organic extract concentrations prepared from collected sediments from 5 sites along Laguna Lake, Philippines. Compared to whole sediment exposure, more severe embryotoxic and teratogenic responses were elicited in embryos exposed to organic extracts. However, since whole sediment-exposed embryos also revealed significant developmental defects, this exposure phase served as the more realistic exposure scenario in our study. Weak to strong upregulation of hsp 70 levels was also registered among embryos exposed to both whole sediments and organic extracts. The observed embryotoxic and proteotoxic responses by zebrafish embryos to Laguna Lake sediment exposures were discussed in relation to the analyzed contaminants in the sediments (heavy metals, PAHs (perylene), solvent). Overall, the present study points out that the sediment contact assay with zebrafish embryos offers a practicable and highly sensitive bioassay for the general assessment of sediment toxicity.     

Sublethal toxicity of commercial insecticide formulations and their active ingredients to larval fathead minnow (Pimephales promelas)

Toxic effect concentrations of insecticides are generally determined using the technical grade or pure active ingredient. Commercial insecticide formulations, however, contain a significant proportion (> 90%) of so-called inert ingredients, which may alter the toxicity of the active ingredient(s). This study compares the sublethal toxicity of two insecticides, the pyrethroid bifenthrin, and the phenylpyrazole fipronil, to their commercial formulations, Talstar® and Termidor®. Both insecticides are used for landscape treatment and structural pest control, and can be transported into surface water bodies via stormwater and irrigation runoff. We used larval fathead minnow (Pimephales promelas), to determine effects on growth and swimming performance after short-term (24 h) exposure to sublethal concentrations of pure insecticides and the respective formulations. Significantly enhanced 7 d growth was observed at 10% of the 24 h LC₁₀ (53 μg L⁻¹) fipronil. Swimming performance was significantly impaired at 20% of the 24 h LC₁₀ (0.14 μg L⁻¹) of bifenthrin and 10% of the 24 h LC₁₀ of Talstar® (0.03 μg L⁻¹). Fipronil and Termidor® led to a significant impairment of swimming performance at 142 μg L⁻¹ and 148 μg L⁻¹ respectively, with more pronounced effects for the formulation. Our data shows that based on dissolved concentrations both formulations were more toxic than the pure active ingredients, suggesting that increased toxicity due to inert ingredients should be considered in risk assessments and regulation of insecticides.     

项目管理学派：（硬）系统学派

我曾在2006年第10期的文章中介绍了项目管理的八个学派,今年我打算对这八个学派一一进行阐述。由于有些学派有两个或多个子学派,因此我预计全部刊登完需要不止八期。例如,我将首先论述系统学派,而系统学派又包括硬系统学派和软系统学派,对此我计划用两期分别阐述。这对我来说亦是一个探索性旅程,因为我认为随着写作的进行,我将会逐渐理清自己对各个学派的理解。我希望这最终能形成一本书,来指导人们从不同的视角理解项目管理。     

Removal of a synthetic organic chemical by PAC-UF systems. II: Model application

This paper describes several application potentials with a recently developed model for predicting the synthetic organic chemical (SOC) removal by powdered activated carbon (PAC) adsorption during ultrafiltration (UF) and discusses the removal mechanism. The model was successfully applied, without any modification, to dead-end mode operation as well as to cross-flow mode operation, validating the assumption of the internal diffusion control mechanism and the continuously-stirred-tank-reactor (CSTR) concept. Even when UF was operated in a cross-flow mode, PAC added was re-circulating in suspension for only a short time. Then, solute uptake took place mostly by PAC immobilized in membrane tubes not only for dead-end operation but also for cross-flow operation. Therefore, cross-flow operation did not have any advantage regarding the SOC mass transfer on PAC in UF loop over dead-end operation. The model simulation implied that pulse PAC addition at the beginning of filtration cycle resulted better SOC removal than continuous PAC addition. However, for the pulse PAC addition mode, the model predicted somewhat lower effluent SOC concentration than the observed values, and the benefit of pulse PAC application in terms of reducing SOC over its continuous dosage was not confirmed. Longer detention time of PAC dosed in a pulse than continuously dosed PAC could possibly further decrease internal diffusivity.     

关于某氧化铝厂选址方案的比较

简要介绍了中铝山西分公司扩建800kt/a氧化铝的厂址情况,分析比较两个方案的优缺点,选出最佳的厂址方案。     

暖通空调系统故障检测与诊断研究进展

介绍了暖通空调系统发生故障的原因及常见故障,比较了几种常用的故障检测与诊断方法的优缺点.介绍了国内外暖通空调故障检测与诊断的研究现状和应用情况.展望了发展方向.     

Assessing the chelating ability of Aerva Lanata: Adsorption of chromium from tannery effluent and its toxicity measurement

The chelating ability of aqueous leaf extract of Aerva lanata was assessed in vitro. The aqueous leaf extract showed a dose dependent decrease in chelating ability using FeCl₂. The highest chelating ability of aqueous leaf extract was observed at 2 × 10^?5 g/mL (100 ± 0.00). The antioxidant activity of the aqueous leaf extract ranged from 42.13% to 88.66%. At 2 × 10^?5 g/mL concentration, a strong positive significant correlation was observed between chelating ability and total phenolics concentration (R = 0.94; P = 0.001). The chelating ability of aqueous leaf extract (2 × 10^?5 g/mL) showed a high positive significant correlation with antioxidant activity (R = 0.78; P = 0.001). Aqueous leaf extract removed the chromium from tannery effluent by 43 mg/g. Allium cepa toxicity test was performed on tannery effluent treated with aqueous leaf extract that increased the root length of onion.     

Clearance rates of Sabella spallanzanii and Branchiomma luctuosum (Annelida: Polychaeta) on a pure culture of Vibrio alginolyticus

The influence exerted by filter-feeding activity on bacterial density by two sabellid species from the Mediterranean Sea (Ionian Sea, Italy), Branchiomma luctuosum Grube and Sabella spallanzanii Gmelin (Annelida: Polychaeta) was investigated. Clearance rates and retention efficiencies were estimated utilizing the species Vibrio alginolyticus selected on account of previous field studies and its importance in fish culture pathogenicity. The Cmax was 43.2+/-2.63 L h(-1) g(-1) DW for B. luctuosum and 12.4+/-2.22 L h(-1) g(-1) DW for S. spallanzanii. The Retention efficiency was 98% corresponding to a removed bacterial biomass of 44.8+7.88 microgC L(-1) g(-1) DW for B. luctuosum and 70% corresponding to a bacterial biomass of 23.8+2.95 microgC L(-1) g(-1) DW for S. spallanzanii. Maximum retention was recorded after 20 min for the first species and after 30 min for the second one. Present laboratory experiments represent a contribution to the knowledge of the filtration activity of the two polychaetes, characterizing the filtration process on bacterioplankton. Both species resulted extremely efficient in removing V. alginolyticus from seawater in experimental tanks, thus confirming the previous data from the field studies and suggesting their employment as biofilters of microbially contaminated waters in intensive aquaculture.     

Dispersion of exhaled droplet nuclei in a two-bed hospital ward with three different ventilation systems

Effective ventilation in general hospital wards is important for controlling the airborne transmission of infectious respiratory diseases. Experiments have been carried out to increase our understanding of the interaction of the breathing flows of two individuals in a full-scale experimental hospital ward with three ventilation systems, i.e. mixing, downward and displacement ventilation. Two life-size breathing thermal manikins were used to simulate a source patient and a receiving patient. The exhalation jet from a bed-lying manikin was visualized using smoke. N2O was used as tracer gas to simulate the droplet nuclei exhaled by patients; and the spatial distribution of its concentrations was measured. Our experimental results show that for both mixing and downward ventilation, the exhaled jet penetrates a short distance and is diluted quickly by ventilation air. The exhaled droplet nuclei are well mixed in the ward. Bed distance does not affect the personal exposure of the receiving patient. For displacement ventilation, the exhaled jet can penetrate a long distance. A high concentration layer of exhaled droplet nuclei because of thermal stratification locking has also been observed with displacement ventilation. This work is useful for identifying an appropriate ventilation method that can remove droplet nuclei more effectively and minimize the risk of cross-infections in a hospital ward environment. PRACTICAL IMPLICATIONS: As one of the major potential sources for infectious droplet nuclei in a hospital environment, exhalation flows of an infected patient can interact with the respiratory activities of other close individuals and with the room ventilation systems. Our latest results provide information on the penetration of exhalation jets into the ambient environment in different ventilation systems. This work is useful in identifying an appropriate and effective ventilation method for removing droplet nuclei more effectively, and thus minimizing the risk of cross-infections in hospital wards with multiple beds.     

Evaluation of emission toxicity of urban bus engines: compressed natural gas and comparison with liquid fuels

Emissions from a spark-ignition (SI) heavy-duty (HD) urban bus engine with a three-way catalyst (TWC), fuelled with compressed natural gas (CNG), were chemically analyzed and tested for genotoxicity. The results were compared with those obtained in a previous study on an equivalent diesel engine, fuelled with diesel oil (D) and a blend of the same with 20% vegetable oil (B20). Experimental procedures were identical, so that emission levels of the CNG engine were exactly comparable to the ones of the diesel engine. The experimental design was focused on carcinogenic compounds and genotoxic activity of exhausts. The results obtained show that the SI CNG engine emissions, with respect to the diesel engine fuelled with D, were nearly 50 times lower for carcinogenic polycyclic aromatic hydrocarbons (PAHs), 20 times lower for formaldehyde, and more than 30 times lower for particulate matter (PM). A 20-30 fold reduction of genotoxic activity was estimated from tests performed. A very high reduction of nitrogen oxides (NO(X)) was also measured. The impact of diesel powered transport on urban air quality, and the potential benefits deriving from the use of CNG for public transport, are discussed.     

Assessing shrink/swell properties of two argillaceous soils from the Paris Basin: a comparison of cation exchange determination methods

A comparison between three methods of determining cation exchange capacity values has been undertaken in order to evaluate the applicability of methylene blue for characterization of clayey soils. The Argiles vertes de Romainville, Marnes bleues d’Argenteuil (two very plastic, loamy soils from the Paris Basin which are known to experience shrink/swell) were tested in their natural and purified states, as well as samples of smectite, illite and interstratified illlite/smectite. The results from the methylene blue, turbidimetric and cobalt hexamine methods were similar, although the methylene blue gave slightly higher values. It is concluded that the differences seen are likely to be due simply to the degree of accuracy available with the various methods. Hence, the quicker and more convenient methylene blue method was realistic for use by geotechnical engineers. However, attention is drawn to the need to continue these tests to the “end point” which is some 24 h after the solution has stabilised.      

Mercury in the Arctic atmosphere: an analysis of eight years of measurements of GEM at Alert (Canada) and a comparison with observations at Amderma (Russia) and Kuujjuarapik (Canada)

Eight years of gaseous elemental mercury (GEM) concentration measurements from Alert, Nunavut, Canada (between 1995 and 2002) is presented. The annual time series shows a distinct repeating seasonal pattern with an overall annual median concentration for this time period of 1.58 (S.D.=0.04 ng m(-3)). Strong seasonal variation was observed throughout the years with springtime displaying strong variability in the GEM and overall lower median concentrations due to the so-called mercury depletion events (MDEs). Summer concentrations are higher than the annual average and show a decrease in variability. Fall and winter concentrations are distributed around the annual median concentrations and show little variability. The relationship between the springtime depression and the summer increase shows a change in the behaviour of mercury between 1995 and 2002. Preliminary results suggest that during this period an increasing amount of the mercury lost from the atmosphere in the spring is not returned to atmosphere in summer. A comparison of GEM concentration data from three sites--Alert (Canada), Amderma (Russia) and Kuujjuarapik (Canada)--demonstrated similar monthly distribution of GEM between Alert and Amderma, with the latter not showing as high summer concentrations. Monthly distribution of GEM at Kuujjuarapik varied considerably from the other two sites. MDEs were found to occur at each site in the spring yet displayed different characteristics. MDEs appear to start at Alert shortly after polar sunrise but in Amderma their initiation is delayed approximately 2 months following polar sunrise. MDEs occur in Kuujjuarapik in the springtime despite an incomplete development of the polar day-night cycle. In spring, as soon as air temperature attained temperatures consistently above 0 degrees C, MDEs ended immediately at all three sites. Continued studies into MDEs are warranted, but clearly an important component of future studies must focus on the origins of the variation of GEM behaviour at different sites.     

Modeling of energy performance of a house with three configurations of building-integrated photovoltaic/thermal systems

A theoretical and experimental study of energy performance of three different open loop air heating building-integrated photovoltaic/thermal (BIPV/T) systems that utilize recovered heat for home heating is presented. The configurations are: Configuration 1: base case of unglazed BIPV with airflow under it; Configuration 2: addition of 1.5 m vertical glazed solar air collector in series with Configuration 1; Configuration 3: addition of a glazing over the PV. The model developed has been verified against experimental data from a solar research house for Configuration 1. Obtained relationships for BIPV/T system exiting air temperature as function of solar irradiance and air speed in PV cavity may be used for developing fan airflow control strategies to achieve desired outlet air temperature suitable for different applications. For Configuration 1, preheated air is suitable for HVAC system and domestic hot water (DHW) preheating. Higher outlet air temperatures of the PV cavity suitable for DHW might be achieved by utilizing Configurations 2 or 3. With Configuration 2, significant outlet air temperatures are achieved in winter along with enhanced thermal efficiency making it suitable for coupling with a rockbed heat storage. Finally, Configuration 3 significantly reduces electricity production and may lead to excessively high PV panel temperatures.     

Atmospheric inputs of Ag and Tl to the Arctic: comparison of a high resolution snow pit (AD 1994-2004) with a firn (AD 1860-1996) and an ice core (previous 16,000 yr)

Applying strict clean room techniques and sector field ICP-MS, a total of 567 ice and snow samples from Devon Ice Cap, Arctic Canada, have been analysed for silver (Ag) and thallium (Tl), providing a continuous record of atmospheric deposition of both elements for the past approximately 16,000 yr. Concentrations of Ag and Tl ranged from 0.02 to 5.84 pg/g and from 0.03 to 3.40 pg/g, respectively. The natural Tl/Sc background ratio established with ice samples dating between 10,590 and 15,010 yr BP, amounted to 0.11+/-0.03 which is in good agreement with the corresponding value of 0.107 reported for the Upper Continental Crust (UCC). The Ag/Sc background ratio in ice (0.09+/-0.06), in turn, is much more variable and approximately 10-times higher than UCC values. The high temporal resolution provided by 45 samples from the 5 m snow pit representing the period AD 1994 to 2004, revealed the greatest elemental concentrations as well as accumulation rates during the winter months when air masses reach the Arctic predominantly from Eurasia. The greatest Sc concentrations, however, are also found during winter months which clearly reflect strong seasonal variations in atmospheric dust inputs. Enrichment factors calculated for both elements (Ag, Tl) using Sc show contrasting behaviours, with the maximum EF for Tl (up to 48) during summer when air masses arriving to the Arctic are predominantly from North America, probably reflecting coal burning, base metal mining and smelting. The greatest enrichments of Ag (up to 17), on the other hand, tend generally to be found in winter, although some enrichment maxima corresponding to summer months are also seen. While modern Ag EF are comparable to those corresponding to ancient (back to ca. 3 k yr) anthropogenic activities, modern Tl EF clearly exceed the impact of Medieval, Roman and Greek/Phoenician civilization. Accumulation rates during the past decade have been variable (mean 36 and 130 ng/m(2)/yr for Ag and Tl, respectively), but the trend is clearly in decline. Based on the best estimate of natural inputs, more than 80% of the Ag and 90% of the Tl supplied to the Arctic today (AD 1994-2004) are derived from anthropogenic sources.