Solar and UV photodecomposition of 2,3,7,8-tetrachloro dibenzo-p-dioxin in the environment

Photodegradation of 2,3,7,8-tetrachloro dibenzo-p-dioxin can be achieved in field soils, and on any other material contaminated by this substance providing a layer of a substance consisting of a hydrogen donor is added followed by irradiation by sunlight or high-pressure mercury lamps. A suitable layer is obtained by spraying surfaces with a 1 : 1 xylene-ethyl oleate solution into which TCDD dissolves. Photodecomposition rate is affected by the intensity of radiation, the medium upon which 2,3,7,8-tetrachloro dibenzo-p-dioxin is dispersed and temperature. Radiations from high-pressure mercury lamps can be used to decontaminate both indoors and outdoors of buildings, while natural summer solar radiation has been found to be effective in the decontamination of floors, walls and soil. Decontamination occurs to a certain extent also beneath the soil surface.     

Radiation dose and antioxidant depletion in a HDPE geomembrane

The impact of α and β radiation on antioxidant depletion in smooth high-density polyethylene (HDPE) geomembranes (GMs) is described. Smooth HDPE GMs having different thickness (0.04-mm, 0.1-mm, 0.2-mm) were created by mechanically pulverizing sections of 2-mm-thick smooth HDPE GM and extruding the polymer at different thicknesses using a film blowing machine. The 2-mm-thick smooth HDPE GM was also used in the experiments. HDPE GM specimens were exposed to sealed sources of ²⁴¹Am and ⁹⁹Tc for 1–50?h to simulate the impact of α and β radiation from U and ⁹⁹Tc in low-level radioactive waste (LLW) leachate. Standard oxidative induction time (OIT) tests were conducted to determine antioxidant depletion. No change in OIT occurred in the 2-mm-thick HDPE GM after exposure to sealed sources of ²⁴¹Am and ⁹⁹Tc for 50?h. In much thinner GMs (e.g., 0.04?mm), however, significant antioxidant depletion occurred after exposure most likely due to penetration of α and β particles. Penetration depth of α and β particles and dose deposition in HDPE GMs were estimated with the GEometry ANd Tracking (GEANT4) program. Predictions from GEANT4 show that maximum dose deposition occurs at the surface of the HDPE GM and decreases with depth. A multilayer model is used to estimate antioxidant depletion in HDPE GMs for depth-dependent doses. These estimates suggest that radiation from LLW leachate has an insignificant effect on antioxidant depletion in HDPE GMs due to the low dose deposition (e.g., 2.42?Gy) expected over a 1000-yr service life, even if the level of activity in LLW leachate increases 10x to 100x the level typical of today.     

Secondary VOC emissions from flooring material surfaces exposed to ozone or UV irradiation

Chemical reactions on the surface of building materials can lead to secondary emissions from these materials that influence indoor air quality. Many studies have been made on the physical processes that influence material emissions. However, there are only a few studies on secondary emissions resulting from exposure of building material surfaces to ozone or ultraviolet (UV) irradiation. Therefore, this study was aimed at elaborating on the emission of chemicals resulting from chemical reactions initiated by the exposure of the surface of flooring materials to ozone or UV irradiation. The laboratory tests were conducted to estimate gas-phase emissions from the flooring materials when they were exposed to ozone or various kinds of light irradiation (infrared, sunlight, UV-A and UV-B lamps). The infrared and sunlight lamps significantly increased the temperature of the test specimens and, in turn, increased the emission rate for various organic compounds. The flooring materials used in this study had been treated with UV-cured surface coatings during their manufacturing. As a result, when exposed to UV irradiation, chemical transformations occurred resulting in the emission of a number of secondary products, including formaldehyde, acetaldehyde, cyclohexanone and benzaldehyde. Ozone reacted with chemicals present in the flooring materials to increase the emission rates of formaldehyde and acetaldehyde. Hence, the exposure of ozone and UV irradiation increased the secondary emissions of formaldehyde, even though the low formaldehyde emission type of flooring material was employed.     

基于ASHRAE晴空模型的日照作用下钢构件的温度场分析

分析钢结构温度效应和确定施工合拢温度关键在于确定温度场的分布。在日照下,由于钢构件的温度场分布非常复杂和不均匀,而难以确定。基于ASHRAE晴空模型,采用ANSYS的APDL语言对箱型钢构件在夏至日日间的温度场进行了数值模拟,模拟中考虑了太阳辐射强度、对流换热系数、构件表面太阳辐射吸收系数等对构件温度场的影响。结果表明:夏至日构件最高温度高达78.411℃,最大升温高达44.803℃;太阳辐射强度、对流换热系数和构件表面太阳辐射吸收系数对日照下的箱型钢构件温度场的影响起主导作用。     

Solar radiation influence on the decomposition process of diclofenac in surface waters

Diclofenac can be detected in surface water of many rivers with human impacts worldwide. The observed decrease of the diclofenac concentration in waters and the formation of its photochemical transformation products under the impact of natural irradiation during one to 16 days are explained in this article. In semi-natural laboratory tests and in a field experiment it could be shown, that sunlight stimulates the decomposition of diclofenac in surface waters. During one day intensive solar radiation in middle European summer diclofenac decomposes in the surface layer of the water (0 to 5 cm) up to 83%, determined in laboratory exposition experiments. After two weeks in a field experiment, the diclofenac was not detectable anymore in the water surface layer (limit of quantification: 5 ng/L). At a water depth of 50 cm, within two weeks 96% of the initial concentration was degraded, while in 100 cm depth 2/3 of the initial diclofenac concentration remained. With the decomposition, stable and meta-stable photolysis products were formed and observed by UV detection. Beyond that the chemical structure of these products were determined. Three transformation products, that were not described in the literature so far, were identified and quantified with GC-MS.     

The impact of sunlight on inactivation of indicator microorganisms both in river water and benthic biofilms

A detailed knowledge on decay or inactivation kinetics of faecal indicator microorganism in rivers is essential for control of bathing water quality. Both reliable inactivation rate coefficients for such kinetics and the knowledge on pathogen accumulation in benthic biofilms are needed for the assessment of river self purification capability and for being able to make decisions for an optimized water management. Therefore, the inactivation kinetics for main indicator microorganisms like faecal coliforms and intestinal Enterococci in water and on stones of the river Isar (Germany) were measured at artificial sunlight radiation. A flume was built, containing Isar water and sediment. By adding a pulse of pre-treated sewage water, the subsequently change of indicator bacteria levels in the bulk and biofilm phase is measured. Bacterial inactivation was mainly dependent on sunlight intensity. Mean inactivation rate coefficients in the experimental set up with river water obtained for a radiation intensity comparable to average midday sunlight in June in 50 degrees north latitude (I((290-390nm))=40.0W/m(2)) were found to be 21.4d(-1) for faecal coliforms and 20.0d(-1) for intestinal Enterococci. For a radiation intensity conform with the annual mean radiation in Germany (I((290-390nm))=8.0W/m(2)) inactivation rate coefficients were 12.7d(-1) for faecal coliforms and 9.3d(-1) for intestinal Enterococci. A measurement without direct artificial sunlight (I((290-390nm))=0.08W/m(2)) yields inactivation rate coefficients of 3.4d(-1) for faecal coliforms and 1.7d(-1) for intestinal Enterococci, which were similar to those found in wastewater treatment ponds. Due to re-growth and better environmental conditions the concentrations of faecal coliforms and intestinal Enterococci within the biofilm were 10(2) to 10(4) fold higher compared to the bulk water depending on the exposure time.     

Effect of high temperatures on antioxidant depletion from different HDPE geomembranes

The effect of elevated temperatures, typically 95–115 °C, on antioxidant depletion from a high-density polyethylene (HDPE) geomembrane (GMB) incubated in air, water and synthetic leachate is examined. It is shown that the antioxidant depletion in synthetic leachate at 95–115 °C is consistent with what would be expected from Arrhenius modeling based on data from lower temperatures (25–85 °C). A similar finding is reached for incubation in air. However, when incubated in water the antioxidant depletion is more complicated. At temperatures above 100 °C a four-parameter exponential model was needed to fit oxidative induction time data that exhibited quite different early-time and later-time depletion rates. The early-time depletion rate decreases with an increase of the temperature while the later-time depletion rates follow the more typical pattern of increasing with increasing temperature. Three additional HDPE GMBs with different antioxidant packages are examined at elevated temperatures in air. The GMB with the lowest initial standard (Std) oxidative induction time (OIT) and without hindered amine light stabilizer (HALS) has the longest antioxidant depletion stage based on Std-OIT at these elevated temperatures. GMBs stabilized with HALS showed only a slight change in their high pressure OIT during the current study. It is shown also that degradation in physical properties can start at Std-OIT values above the residual OIT values.     

Effect of solar radiation on the migration of vinyl chloride monomer from unplasticized PVC pipes

The effect of direct exposure to solar radiation on the migration of vinyl chloride monomer (VCM) from unplasticized polyvinyl chloride (uPVC) pipes was investigated using locally manufactured and imported pipes. Specimens 33 cm long were used throughout the research. The investigation was carried out, at different times of exposure, by exposing one part of the specimens to the direct sunlight, while keeping the other part in the shade. The VCM concentration in the water was evaluated using the gas chromatography (GC)/head-space technique. A VCM concentration of 2.5 microg/l was detected after 30 days of exposure in direct sunlight. The original initial VCM concentration in the uPVC was predicted, and the diffusion rate of VCM from uPVC pipes was expressed as a function of time.     

Experimental investigation on surface radiation properties’ degradation of solar collector receiver tube material

In this study, we have investigated the degradation characteristics of surface radiation heat transfer properties of stainless steel 304. The emissivity (ε) and absorptivity (α) of stainless steel has been measured for a surface unexposed to sunlight and that exposed to sunlight for various time intervals (240, 480, 720, and 960?h). The temperature dependence of these properties is also measured for the temperature range of 30–300°C at 10 equal intervals. It is observed that the emissivity of the material increased when it is exposed to sunlight and the temperature dependence is very strong beyond 180°C. The absorptivity of the material increases first and then starts to decrease with exposure time. The combined effect of decrease in absorptivity and increase in emissivity leads to reduction in aS/E ratio, which results in a higher rate of radiation loss for exposed surfaces when compared to that for the unexposed surfaces.     

Specific detection of cyclobutane pyrimidine dimers in phytoplankton DNA by a non-radioactive assay based on T4-endonuclease V digestion

The effect of artificial and natural UV irradiation on DNA in marine phytoplankton Isochrysis galbana monoculture was investigated. The presence of cyclobutane pyrimidine dimers (CPDs) in unlabelled I. galbana DNA was detected by a non-radiometric alkaline filter elution assay after T4-endonuclease V digestion. The quantity of CPDs was estimated by alkaline agarose gel electrophoresis. Precise determination of the amount of DNA in the presence of I. galbana pigments was achieved by oxazole yellow homodimer (YOYO) dye. T4-endonuclease V-sensitive sites frequency (ESS/kb), measured after exposure to 2-40 kJ m(-2) of artificial UV light, increased in a dose-dependent manner. Twelve hours after irradiation cell culture growth was disrupted, and 50% of initial DNA damage in the cells was observed. After 1 h of sunlight exposure, the incidence of CPDs increase significantly. Prolonged exposition to sunlight decrease CPDs incidence due to efficiency of I. galbana DNA repair mechanisms. The presence of water-soluble crude oil fraction (WSOF) affected DNA repair efficiency resulting in accumulation of CPDs in I. galbana DNA.     

The effect of photochemical treatment of water on algal growth

A new method for the destruction of algae in surface waters by dye-sensitized photooxidation is described. The algae (Peridinium, Pediastrum and Cosmarium) used as test organisms were inoculated in an artificial culture medium, containing a dye-sensitizer, with subsequent incubation in a controlled environment (20 ± 2°C, 14 h light, 10 h darkness). Water samples from Peridinium bloom in Lake Kinneret underwent similar treatment. The algicidal effect of various sensitizer concentrations and of different sunlight exposure times was investigated. Complete destruction of algae was obtained in about 2 weeks of incubation after exposure to solar radiation for 30–60 min in the presence of 0.25, 0.15 and 0.75 mg 1⁻¹ methylene blue or 0.5, 0.8 and 0.8 mg 1⁻¹ rose bengal in Peridinium, Pediastrum and Cosmarium cultures, respectively.     

Durability of fluorinated high density polyethylene geomembrane in the Arctic

A series of fluorinated high density polyethylene (f-HDPE) geomembrane (GM) samples of different thickness (1, 1.5 and 2.5 mm) was exhumed from the backfill immediately upstream of a barrier system constructed to contain a hydrocarbon spill in the Canadian Arctic. The samples were tested for oxidation induction time (OIT), crystallinity, melt index (MI) and tensile properties. The results of these tests are reported and it is shown that the durability of the GM was maintained well beyond the initial 3-year design life of the barrier system. Based on 7 years of field data, the std-OIT depletion time for the 1.5 mm thick GM used in the barrier system was inferred to be over 140 years while the antioxidant depletion time based on the HP-OIT is estimated to be about 200 years. No significant temporal changes in the crystallinity, MI or tensile properties of the exhumed GM samples were detected.     

Isothiazolone emissions from building products

Adding biocides to dispersion products is a well‐known practice to control microbial deterioration. Isothiazolones are among the most commonly used preservatives, in particular a mixture of 2‐methyl‐2H‐isothiazol‐3‐one (MIT) and 5‐chloro‐2‐methyl‐2H‐isothiazol‐3‐one (CIT). In recent years, for health reasons, due to its strong sensitizing effect, CIT has been replaced by 1,2‐benzisothiazol‐3‐one (BIT). Furthermore, numerous products are now available for interiors containing the fungicidal active substance 2‐octyl‐2H‐isothiazol‐3‐one (OIT). So far nearly nothing is known of the emission behavior of BIT and OIT. An analytical method was developed for these two isothiazolones and interior products containing BIT respectively OIT have been investigated in an emission chamber and in test rooms. The chamber tests revealed maximum concentrations of 6.7 μg OIT/m³, 1.9 μg BIT/m³, and 187 μg MIT/m³. Concentrations obtained in the test rooms were at levels up to 1.4 μg OIT/m³ and 29 μg MIT/m³. A noticeable finding was the very slight subsidence of OIT and BIT levels over several weeks. While MIT outgassed quickly, OIT in particular showed low concentrations, but prolonged evaporation.     

Computer simulation of sunlight concentration due to façade shape: application to the 2013 Death Ray at Fenchurch Street,London

Reflected sunlight from the Walkie-Talkie building in 20 Fenchurch Street, London, was reported to have caused the melting of plastic components of a car parked at street level in late August of 2013. The incident was explained by the concave-shaped south façade of the building, which converges solar radiation into a hotspot. In this study, we test the sunlight concentation hypothesis with a lighting simulation. A geometry model with material properties was created, and different weather situations were modelled. The results are illustrated in irradiance maps indicating time, position and peak heat fluxes. The highest simulated flux on the day of the incident was 3320?Wm^?2 (10 to 15 fold increase compared to direct solar radiation). Additionally, the specific time and day for maximum heat fluxes between June and December were determined . For the worst scenario, which was avoided becuase the sky was partially cover with clouds that day and the hotspot did not fall on street level, the simulations showed that the peak heat flux would have reached well over 4000?Wm^?2.     

Interaction of antioxidants with carbon black in polyethylene using oxidative induction time methods

Carbon black (CB) is added to the geosynthetics for ultraviolet protection. However, CB can interact with antioxidant (AO) in the geosynthetics, and their interaction has been documented to be synergistic and/or antagonistic towards the oxidation reaction. In this paper, two oxidative induction time (OIT) methods, a standard (Std) OIT test and a high pressure (HP) OIT test, were used to evaluate the interaction of CB with two types of antioxidants during the oven aging. Test samples made from high density polyethylene (HDPE) blended with different amounts of Irganox^®1010 (I-1010) and Irgafos^®168 (I-168) together with 0 or 2.5wt.% of carbon black were studied. The sample were incubated in a forced air oven at 85 °C to accelerate the oxidation reactions. After 1000 days, Std-OIT values of samples with 500 ppm and 1000 ppm I-1010 exhibited only 10% drop from their initial values from 19.42 min and 34.01 min to 17.53 and 31.0 min respectively. In comparison, a continuous decrease of Std-OIT value was observed for samples contained both I-1010 and I-168; a 40% drop was measured after 1000 days, corresponding to 16.4 and 26.8 min reduction. For samples contained 2.5% CB and I-1010, an exponentially decrease of Std-OIT and HP-OIT with aging time was obtained. However, adding I-168 to those samples did not change the OIT decreasing trends, indicating that the interaction of CB with I-168 is negligible. The test data further verify that the effectiveness of the OIT test is strongly correlated to the functional temperature range of the AO. The Std-OIT test with testing temperature of 200 °C can detect both I-1010 and I-168, while the 150 °C testing temperature of the HP-OIT test can only detect the I-1010.     

Oxidative degradation of pyrene in contaminated soils by δ-MnO2 with or without sunlight irradiation

The enhanced oxidative degradation of pyrene in quartz sand and alluvial and red soils by micro-nano size birnessite (δ-MnO₂) in the presence and absence of sunlight was investigated. The degradation of pyrene by δ-MnO₂ in quartz sand showed very little synergistic effect of sunlight irradiation on δ-MnO₂ oxidizing power. However, pyrene degradation by δ-MnO₂ in alluvial and red soils was greater under solar irradiation than the combination of photooxidation of pyrene and oxidation of pyrene by δ-MnO₂. The oxidative degradation percentages of pyrene by δ-MnO₂ under sunlight irradiation are 94.8, 97.7, and 100% for alluvial soil, red soil, and quartz sand, respectively. Oxidative degradation percentages of pyrene by δ-MnO₂ in alluvial and red soils with irradiation of sunlight almost attained a maximum at 1 h with a 5% (w/w) dose of the amended oxidant. Due to their different total organic carbon (TOC) contents, the sequence of enhanced oxidative degradation of pyrene by δ-MnO₂ in quartz sand and alluvial and red soils was quartz sand > red soil > alluvial soil. Further, this study revealed that δ-MnO₂-enhanced oxidative degradation of pyrene is very pronounced in contaminated soils in situ even at deep soil layers where irradiation by sunlight is very limited.     

Effect of sunlight irradiation on photocatalytic pyrene degradation in contaminated soils by micro-nano size TiO2

The enhanced catalytic pyrene degradation in quartz sand and alluvial and red soils by micro-nano size TiO₂ in the presence and absence of sunlight was investigated. The results showed that the synergistic effect of sunlight irradiation and TiO₂ was more efficient on pyrene degradation in quartz sand and red and alluvial soils than the corresponding reaction system without sunlight irradiation. In the presence of sunlight irradiation, the photooxidation (without TiO₂) of pyrene was very pronounced in alluvial and red soils and especially in quartz sand. However, in the absence of sunlight irradiation, the catalytic pyrene degradation by TiO₂ and the photooxidation (without TiO₂) of pyrene were almost nil. This implicates that ultra-violet (UV) wavelength range of sunlight plays an important role in TiO₂-enhanced photocatalytic pyrene degradation and in photooxidation (without TiO₂) of pyrene. The percentages of photocatalytic pyrene degradation by TiO₂ in quartz sand, alluvial and red soils under sunlight irradiation were 78.3, 23.4, and 31.8%, respectively, at 5 h reaction period with a 5% (w/w) dose of the amended catalyst. The sequence of TiO₂-enhanced catalytic pyrene degradation in quartz sand and alluvial and red soils was quartz sand > red soil > alluvial soil, due to different texture and total organic carbon (TOC) contents of the quartz sand and other two soils. The differential Fourier transform infrared (FT-IR) spectra of degraded pyrene in alluvial soil corroborate that TiO₂-enhanced photocatalytic degradation rate of degraded pyrene was much greater than photooxidation (without TiO₂) rate of degraded pyrene. Based on the data obtained, the importance for the application of TiO₂-enhanced photocatalytic pyrene degradation and associated organic contaminants in contaminated soils was elucidated.     

Modeling thermal response of steel–concrete floor systems in a furnace

A methodology was developed to predict the thermal exposure from a furnace onto a floor assembly specimen. In furnaces with low conductivity wall linings and gas fired burners with complete combustion, the gas attenuation effects were determined to be small indicating that radiation between surfaces and convection are the dominant modes of heat transfer. This was modeled by assigning the internal furnace wall temperature to the furnace time–temperature exposure and performing a three-dimensional heat transfer analysis on the specimen. The furnace exposure model predicted heat transfer to the specimen surface that was within 5–14% of measured heat fluxes. The proposed furnace exposure methodology was used to predict the temperature rise of steel in a floor assembly where the test specimen can view itself as well as the furnace, making radiation exchange an important aspect of the problem. Predictions were within 5–10% of the measured values, which was within the experimental uncertainty.     

Effect of Antarctic solar radiation on sewage bacteria viability

The majority of coastal Antarctic research stations discard untreated sewage waste into the near-shore marine environment. However, Antarctic solar conditions are unique, with ozone depletion increasing the proportion of potentially damaging ultraviolet-B (UV-B) radiation reaching the marine environment. This study assessed the influence of Antarctic solar radiation on the viability of Escherichia coli and sewage microorganisms at Rothera Research Station, Adelaide Island, Antarctic Peninsula. Cell viability decreased with increased exposure time and with exposure to shorter wavelengths of solar radiation. Cell survival also declined with decreasing cloud cover, solar zenith angle and ozone column depth. However, particulates in sewage increased the persistence of viable bacteria. Ultraviolet radiation doses over Rothera Point were highest during the austral summer. During this time, solar radiation may act to partially reduce the number of viable sewage-derived microorganisms in the surface seawater around Antarctic outfalls. Nevertheless, this effect is not reliable and every effort should be made to fully treat sewage before release into the Antarctic marine environment.     

Photocatalytic magnetic separable beads for chromium (VI) reduction

Magnetically separable photocatalyst beads containing nano-sized iron oxide in alginate polymer were prepared. This magnetic photocatalyst beads are used in slurry-type reactors. The magnetism of the catalyst arises from the nanostructured particles γ-Fe₂O₃, by which the catalyst can be easily recovered by the application of an external magnetic field. These synthesized beads are sunlight-driven photocatalyst. In the system without magnetic photocatalyst beads, no chromium reduction was observed under sunlight irradiation due to the stability of the chromium (VI). Upon the addition of magnetic photocatalyst beads, the photo-reduction of Cr(VI) was completed in just after only 50 min under sunlight irradiation due to the photocatalytic activity of the beads. However when placed away from sunlight, the reduction rate of the chromium is just about 10%. These observations were explained in terms of absorption occurrence of chromium (VI) onto the catalyst surface which took place in this reaction. In addition, photo-reduction rate of chromium (VI) was more significant at lower pH. The results suggest that the use of magnetic separable photocatalyst beads is a feasible strategy for eliminating Cr(VI).