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In accelerated weathering tests, specimens are exposed to higher radiation intensity, temperature and humidity than is likely under natural weathering in order to achieve rapid degradation of the polymer in a convenient short time. In the current work, a correlation between the two environments is attempted so that a prediction of lifetimes in the natural environment can be achieved. During aging, surface flaws are created due to the chain scission process. This is initiated by the absorption of ultra-violet light and directly affects visual appearance and impact strength. After natural weathering, the material shows only plastic deformation in an impact test. However, after artificial weathering to 5000 h of UV exposure, there is a decrease of 85% in impact strength. Colour change occurs at a high rate in the early stages of UV exposure. Beyond 2000 h of exposure, the colour change approaches a steady state and a correlation between the changes under natural and artificial weathering becomes apparent for a potential prediction of lifetimes. From the analysis including the specular component (SCI), taking surface roughening into account, 1 year under natural weathering was found to be equivalent to 25 days under accelerated weathering.  相似文献   
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Over the last 10 years, there has been a plethora of experimental studies estimating the potential of microplastic particles (MPs) to exert toxic effects in the environment, many specifically focusing on their postulated capacity to enhance the transfer of environmental pollutants into organisms after ingestion. Obviously, there is little to no consensus on appropriate experimental design, which is mainly owing to the novelty, the interdisciplinarity of the subject, and the complexity of parameters involved. This results in fundamental discrepancies regarding the materials applied, the approach for spiking MPs with pollutants, and the exact exposure scenario. Aiming for a non-chemist audience and providing illustrative, representative, and comparative examples, this review first outlines the theoretical essentials of processes involved in sorption. Also, it discusses the implications for designing experimental approaches using MPs and interpreting the results obtained under consideration of their relevance for environmental conditions. It may help to improve the interpretation of studies on MP toxicity already published, while also calling experimenters’ attention to various aspects important to consider when designing and performing environmentally relevant experiments with MPs.

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In recent years, the science of foresight has been entered into planning activities by urban and regional planners and this science has impacted on planning activities. This study discusses spatial development in the south of Bushehr province using the foresight approach. The general aim of this research is to compile scenarios for the development of the mentioned study area which comprises the southern part of Bushehr province including four counties of Dayyer, Jam, Kangan and Asaluyeh. The main reason for selecting this region is their direct impressibility by major changes in the country’s oil and gas industry. This research has extremely made use of the Delphi and cross-impact analysis methods to develop foresight scenarios. Using the Delphi method, 30 initial factors were identified in the economic, political-security, linkages, science and technology, manufacturing, natural, social, infrastructural and residential issues and then the cross-impact matrix was used to investigate the impact of factors on each other. In the next step, the ranking of direct and indirect factors was determined by Micmac software and on this basis, the final refining in the selection of drivers was done. In the final stage, axes of future scenarios were presented and then the future scenarios were drawn. Results of this research indicate that two main drivers namely Iran’s international relations and energy resources are the main axes of scenarios. These two drivers have more uncertainty and higher importance than other factors and the results in four scenarios showing the possibility of each situation’s occurrence.  相似文献   
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Introduction  

High concentrations of hexabromocyclododecane (HBCD) sometimes recorded in free-range hens' eggs are thought to be due to soil ingestion. Of the three stereoisomers of HBCD (α-, β-, and γ-HBCD), γ-HBCD is the main component in the commercial mixture, as well as in environmental matrices, whereas the isomer profile is α-dominated in biota. In fish and in mammals, this shift is thought to be due to a rapid elimination of γ-HBCD and to its bioisomerization to the more persistent α-HBCD. The aim of the current controlled study was to better understand the fate of ingested HBCD in laying hens. The isomer profile in soil being γ-dominated, excretion kinetics of γ-HBCD into egg yolk, and accumulation in liver and in abdominal fat were investigated.  相似文献   
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Al Nasir F  Batarseh MI 《Chemosphere》2008,72(8):1203-1214
The residues of polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated benzenes (CBs) and phenols were investigated for soil, wastewater, groundwater and plants. The uptake concentration of these compounds was comparatively determined using various plant types: Zea mays L., Helianthus annus L., Capsicum annum L., Abelmoschus esculentus L., Solanum melongena L. and Lycopersicon esculentum L. which were grown in a pilot site established at Mutah University wastewater treatment plant, Jordan. Soil, wastewater, groundwater and various plant parts (roots, leaves and fruits) samples were extracted in duplicate, cleaned up by open-column chromatography and analyzed by a multi-residue analytical methods using gas chromatography equipped with either mass selective detector (GC/MS), electron capture detector (GC/ECD), or flame ionization detector (FID). Environmentally relevant concentrations of targeted compounds were detected for wastewater much higher than for groundwater. The overall distribution profiles of PAHs and PCBs appeared similar for groundwater and wastewater indicating common potential pollution sources. The concentrations of PAHs, PCBs and phenols for different soils ranged from 169.34 to 673.20 microg kg(-1), 0.04 to 73.86 microg kg(-1) and 73.83 to 8724.42 microg kg(-1), respectively. However, much lower concentrations were detected for reference soil. CBs were detected in very low concentrations. Furthermore, it was found that different plants have different uptake and translocation behavior. As a consequence, there are some difficulties in evaluating the translocation of PAHs, CBs, PCBs and phenols from soil-roots-plant system. The uptake concentrations of various compounds from soil, in which plants grown, were dependent on plant variety and plant part, and they showed different uptake concentrations. Among the different plant parts, roots were found to be the most contaminated and fruits the least contaminated.  相似文献   
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Aquatic stability and impact of titanium dioxide nanoparticles (TiO2 NPs, 10–30 nm) were investigated using Artemia salina. Acute exposure was conducted on nauplii (larvae) and adults in seawater in a concentration range from 10 to 100 mg/L TiO2 NPs for 24 and 96 h. Rapid aggregation occurred in all suspensions of TiO2 NPs to form micrometer size particles. Yet, both nauplii and adults accumulated the aggregates significantly. Average TiO2 content in nauplii ranged from 0.47 to 3.19 and from 1.29 to 4.43 mg/g in 24 and 96 h, respectively. Accumulation in adults was higher ranging from 2.30 to 4.19 and from 4.38 to 6.20 mg/g in 24 and 96 h, respectively. Phase contrast microscopy images revealed that Artemia were unable to excrete the particles. Thus, the TiO2 aggregates filled inside the guts. No significant mortality or toxicity occurred within 24 h at any dose. Lipid peroxidation levels characterized with malondialdehyde concentrations were not statistically different from those of the controls (p?>?0.05). These results suggested that suspensions of the TiO2 NPs were nontoxic to Artemia, most likely due to the formation of benign TiO2 aggregates in water. In contrast, both mortality and lipid peroxidation increased in extended exposure to 96 h. Highest mortality occurred in 100 mg/L TiO2 NP suspensions; 18 % for nauplii and 14 % for adults (LC50?>?100 mg/L). These effects were attributed to the particle loading inside the guts leading to oxidative stress as a result of impaired food uptake for a long period of time.  相似文献   
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