Allium cepa root tip assay in assessment of toxicity of magnesium oxide nanoparticles and microparticles

Allium cepa bioassay had been used from decades for the assessment of toxicants and their harmful effects on environment as well as human health. Magnesium oxide(MgO) particles are being utilized in different fields. However, reports on the adverse effects of MgO nanoparticles on the environment and mankind are scarce. Hence, the toxicity of MgO particles is of concern because of their increased utilization. In the current study, A. cepa was used as an indicator to assess the toxicological efficiency of MgO nano-and microparticles(NPs and MPs) at a range of exposure concentrations(12.5, 25, 50, and100 μg/m L). The toxicity was evaluated by using various bioassays on A. cepa root tip cells such as comet assay, oxidative stress and their uptake/internalization profile. Results indicated a dose dependent increase in chromosomal aberrations and decrease in mitotic index(MI) when compared to control cells and the effect was more significant for NPs than MPs(at p 0.05). Comet analysis revealed that the Deoxyribonucleic acid(DNA) damage in terms of percent tail DNA ranged from 6.8–30.1 over 12.5–100 μg/m L concentrations of MgO NPs and was found to be significant at the exposed concentrations. A significant increase in generation of hydrogen peroxide and superoxide radicals was observed in accordance with the lipid peroxidation profile in both MgO NPs and MPs treated plants when compared with control. In conclusion, this investigation revealed that MgO NPs exposure exhibited greater toxicity on A. cepa than MPs.     

Trace metal pollution in aquatic sediments and some fish species from the Kwilu-Ngongo River,Democratic Republic of Congo (Bas-Congo)

In this study, the concentrations of some metals in sediments and consumable fish from the Kwilu Ngongo River, province of Bas-Congo, Democratic Republic of Congo, are investigated. The digested muscle tissue, whole fish, and river sediment samples were subjected to trace element analysis by inductively coupled plasma mass spectroscopy and by using an automatic mercury analyzer. The highest values of trace metals in fish muscle tissue were found for Cr, Cu, Pb and Hg, with maximum values of 8.6 (Cr), 15.7 (Cu), 6.0 (Pb) and 3.3 (Hg) mg kg^?1. These values are higher than maximum tolerable limits recommended by the European Commission Regulation for Food. The highest metal concentrations in sediments were 81 (Cr), 86 (Cu), 21 (Sb), 41 (Pb), and 0.8 (Hg) mg kg^?1. Sediment toxicity tests using benthic crustaceans (ostracods) revealed mortality rates of up to 30% after six days of exposure to the sediments near the sugarcane industry outlet pipe discharge. The contamination of the sediments and fishes by the elements and the bio-accumulation of mercury in fish most likely arise from the adjacent agricultural fields where intensive sugarcane cultivation since 1925 has probably contaminated the soils through the long-term use of fertilizers and pesticides.     

Synthesis and characterization of an ion exchanger based on tamarind kernel powder and its application for removal of some metal ions from industrial effluents

A resin synthesized from tamarind kernel powder possesses high selectivity for metal ions. Distribution coefficients for some metal ions has been determined by the batch method. The influence of pH on ion exchange capacity and K _d value of metal ions were studied. The resin has been characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, chemical composition and ion exchange capacity (IEC). The selectivity order is Pb²⁺?>?Cu²⁺?>?Fe²⁺?>?Zn²⁺?>?Ni²⁺. Removal of metal ions from the aqueous solution and from effluents of a steel mill has been studied.     

PM2.5 mass and light extinction reconstruction in IMPROVE

Compliance under the Regional Haze Rule of 1999 is based on Interagency Monitoring of Protected Visual Environments (IMPROVE) protocols for reconstructing aerosol mass and light extinction from aerosol chemical concentrations measured in the IMPROVE network. The accuracy, consistency, and potential biases in these formulations were examined using IMPROVE aerosol chemistry and light extinction data from 1988-1999. Underestimation of particulate matter with an aerodynamic diameter < 2.5 microm (PM2.5) by the IMPROVE mass reconstruction formula by 12%, on average, appears to be related to the exclusion of sodium, chlorine, and other elements and to artifacts associated with the measurement of organic carbon, but not to absorption of water by sulfates and nitrates on IMPROVE Teflon filters during weighing. Light scattering measured by transmissometry is not consistent with nephelometer scattering or single-scatter albedos expected for remote locations. Light scattering was systematically overestimated by 34%, on average, with the IMPROVE particle scattering (Bsp) reconstruction formula. The use of climatologically based hygroscopic growth factors f(RH) suggested for compliance with the Haze Rule contributes significantly to this overestimation and increases the amount of light extinction attributable to sulfates for IMPROVE samples between 1993 and 1999 by 5 percentage points.     

Evaluation of wind fields used in Grand Canyon Visibility Transport Commission analyses

The Grand Canyon Visibility Transport Commission (GCVTC) was established by the U.S. Congress to assess the potential impacts of projected growth on atmospheric visibility at Grand Canyon National Park and to make recommendations to the U.S. Environmental Protection Agency on what measures could be taken to avoid such adverse impacts. A critical input to the assessment tool used by the commission was three-dimensional model-derived wind fields used to transport the emissions. This paper describes the evaluation of the wind fields used at various stages in the assessment. Wind fields evaluated included those obtained from the Colorado State University Regional Atmospheric Modeling System (RAMS), the National Meteorological Center's Nested Grid Model (NGM), and the National Oceanic and Atmospheric Administration's Atmospheric Transport and Dispersion (ATAD) trajectory model. The model-derived wind fields were evaluated at multiple vertical levels at several locations in the southwestern United States by determining differences between model predicted winds and winds that were measured using radiosonde and radar wind profiler data. Model-derived winds were also evaluated by determining the percent of time that they were within acceptable differences from measured winds. All models had difficulties, generally meeting the acceptable criteria for less than 50% of the predictions. The RAMS model had a persistent bias toward southwesterly winds at the expense of other directions, especially failing to represent channeling by north-south mountain ranges in the lower levels. The NGM model exhibited a substantial bias in the summer months by extending northwesterly winds in the eastern Pacific Ocean well inland, in contrast to the observed southwesterlies at inland locations. The simpler ATAD trajectory model performed somewhat better than the other models, probably because of its use of more upper air sites. The results of the evaluation indicated that these wind fields could not be used to reliably predict source-receptor impacts on a particular day; thus, seasonally averaged impacts were used in the GCVTC assessment.     

Vulnerability of Indian mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) Czernj. Cosson) to climate variability and future adaptation strategies

A simulation study has been carried out using the InfoCrop mustard model to assess the impact of climate change and adaptation gains and to delineate the vulnerable regions for mustard (Brassica juncea (L.) Czernj. Cosson) production in India. On an all India basis, climate change is projected to reduce mustard grain yield by ～2 % in 2020 (2010–2039), ～7.9 % in 2050 (2040–2069) and ～15 % in 2080 (2070–2099) climate scenarios of MIROC3.2.HI (a global climate model) and Providing Regional Climates for Impact Studies (PRECIS, a regional climate model) models, if no adaptation is followed. However, spatiotemporal variations exist for the magnitude of impacts. Yield is projected to reduce in regions with current mean seasonal temperature regimes above 25/10 °C during crop growth. Adapting to climate change through a combination of improved input efficiency, additional fertilizers and adjusting the sowing time of current varieties can increase yield by ～17 %. With improved varieties, yield can be enhanced by ～25 % in 2020 climate scenario. But, projected benefits may reduce thereafter. Development of short-duration varieties and improved crop husbandry becomes essential for sustaining mustard yield in future climates. As climatically suitable period for mustard cultivation may reduce in future, short-duration (<130 days) cultivars with 63 % pod filling period will become more adaptable. There is a need to look beyond the suggested adaptation strategy to minimize the yield reduction in net vulnerable regions.     

Environmentally Benign Blue Emissive Films from Host-Dopant Interaction of PLA–Bischalcone Combination with High UV Endurance

Journal of Polymers and the Environment - This work reports the fabrication of blue luminescent bioplastic PLA films on doping with 4-chloro and 4-fluoro substituted bisarylidene cyclohexanone...     

长期立贮固体发动机药柱变形预估方法研究

目的 研究老化与颠振影响下长期立式贮存固体发动机药柱的蠕变特性,基于广义Kelvin模型,构建一种考虑老化和损伤因素的蠕变本构模型。方法 通过开展温度与应力加速蠕变试验、高温加速老化试验以及往复拉伸损伤试验,获得老化与损伤对蠕变的影响规律,建立蠕变预测模型,获取模型参数,并将其嵌入有限元软件。结果 利用所得蠕变本构模型计算了某型发动机立式贮存15 a后药柱蠕变的应力应变,结果表明,考虑老化因素后,发动机药柱的最大等效应力增大了96.84%,最大等效应变减小了4.07%,在同时考虑老化与损伤因素后,最大等效应力增加了82.77%,最大等效应变减小了3.62%。结论 对比不同条件下的仿真结果,老化和损伤对发动机蠕变状态的影响较大。使用该模型能够较好地体现出固体发动机药柱的老化硬化和损伤软化。     

The relationship between typhoons' peripheral circulation and ground-level ozone concentrations in central Taiwan

Surface data of meteorological parameters (wind speed, wind direction, and mixing height) and air pollutant concentrations (O₃, NO, and NO₂) were collected for a 92-day period associated with typhoon formation in 2005. The influence of typhoons on O₃ concentration were defined by azimuth and distance from Taiwan, and Types A, B, and C correspond to typhoons less than 1,500 km from Taiwan and located between azimuths 45° and 135°, 135° and 225°, and 225° and 45°, respectively. Type D corresponds to typhoons more than 1,500 km from Taiwan. Titration reactions were conducted at three temporal phases: 2000–0700, 0800–1100, and 1200–1400 LST (Local Standard Time). The air pollution model (TAPM) was used to simulate wind fields and trajectories of air masses. It was determined that typhoon position affected O₃ concentration, temporal and spatial patterns of O₃ titration and vertical meteorological characteristics, which were not all at the statistically significant level.     

Assessment of pathogenic bacteria in water and sediment from a water reservoir under tropical conditions (Lake Ma Vallée), Kinshasa Democratic Republic of Congo

This study was conducted to assess potential human health risks presented by pathogenic bacteria in a protected multi-use lake-reservoir (Lake Ma Vallée) located in west of Kinshasa, Democratic Republic of Congo (DRC). Water and surface sediments from several points of the Lake were collected during summer. Microbial analysis was performed for Escherichia coli, Enterococcus (ENT), Pseudomonas species and heterotrophic plate counts. PCR amplification was performed for the confirmation of E. coli, ENT, Pseudomonas spp. and Pseudomonas aeruginosa isolated from samples. The results reveal low concentration of bacteria in water column of the lake, the bacterial quantification results observed in this study for the water column were below the recommended limits, according to WHO and the European Directive 2006/7/CE, for bathing water. However, high concentration of bacteria was observed in the sediment samples; the values of 2.65?×?10³, 6.35?×?10³, 3.27?×?10³ and 3.60?×?10⁸ CFU g^?1 of dry sediment for E. coli, ENT, Pseudomonas spp. and heterotrophic plate counts, respectively. The results of this study indicate that sediments of the Lake Ma Vallée can constitute a reservoir of pathogenic microorganisms which can persist in the lake. Possible resuspension of faecal indicator bacteria and pathogens would affect water quality and may increase health risks to the population during recreational activities. Our results indicate that the microbial sediment analysis provides complementary and important information for assessing sanitary quality of surface water under tropical conditions.