大同市某医院放疗装置环境辐射调查

大同市环境监察支队对大同市某医院医用电子直线加速器及近距离遥控后装机工作场所及其周围环境辐射水平进行了调查。表明，加速器及近距离遥控后装机室内X、γ辐射剂量率，在关机或开机状态下监测结果变化不明显，基本在本底范围内。加速器及近距离遥控后装机室外X、γ辐射剂量率范围接近1987年“全国放射性水平调查”的天然贯穿辐射剂量平均值；屋顶X、γ辐射剂量率监测结果也居正常本底水平。     

Development of a novel myconanomining approach for the recovery of agriculturally important elements from jarosite waste

In this study, an ecofriendly and economically viable waste management approach have been attempted towards the biosynthesis of agriculturally important nanoparticles from jarosite waste. Aspergillus terreus strain J4 isolated from jarosite(waste from Debari Zinc Smelter,Udaipur, India), showed good leaching efficiency along with nanoparticles(NPs) formation under ambient conditions. Fourier-transform infrared spectroscopy(FT-IR) and transmission electron microscopy(TEM) confirmed the formation of NPs. Energy dispersive X-ray spectroscopy(EDX analysis) showed strong signals for zinc, iron, calcium and magnesium,with these materials being leached out. TEM analysis and high resolution transmission electron microscopy(HRTEM) showed semi-quasi spherical particles having average size of 10‐50 nm. Thus, a novel biomethodology was developed using fungal cell-free extract for bioleaching and subsequently nanoconversion of the waste materials into nanostructured form. These biosynthesized nanoparticles were tested for their efficacy on seed emergence activity of wheat(Triticum aestivum) seeds and showed enhanced growth at concentration of 20 ppm. These nanomaterials are expected to enhance plant growth properties and being targeted as additives in soil fertility and crop productivity enhancement.     

电子供体刺激下厌氧微生物对1, 2-二氯乙烷的降解效果

通过添加电子供体进行原位生物刺激可有效降解地下水中的氯代烃,目前国内外常采用接种高效微生物的方法强化这一降解过程,鲜见仅利用实际污染场地含水层土著菌开展的生物降解试验.从北京市某氯代烃污染场地采集地下水样品,仅接种场地含水层沉积物,利用微宇宙实验体系,初步探讨了添加不同种类和质量浓度的电子供体对地下水中1,2-二氯乙烷的去除效果影响.结果表明:①同时添加初级生长基质和电子供体对反应体系进行生物刺激可显著降解地下水中的1,2-二氯乙烷.60 d后,添加1 g/L醋酸钠的反应体系中1,2-二氯乙烷的去除率最高,可达93.9%;添加1 g/L的乳酸钠反应体系次之,去除率为82.2%;添加1 g/L的乳酸的反应体系去除率最低,为61.8%.并且添加醋酸钠的试验体系可长时间维持中性pH及较低的氧化还原电位.②相同条件下,对同种电子供体来说,添加量为1 g/L的试验组中1,2-二氯乙烷的降解效果优于添加量为2 g/L的试验组,推测较高质量浓度的电子供体可对微生物的生命活动产生抑制.③对反应体系中间产物进行监测,仅监测到了乙烯的产生,表明在试验周期内无明显毒副产物积累,1,2-二氯乙烷的降解较为彻底.研究显示,醋酸钠为该试验体系中最适电子供体,添加适宜质量浓度醋酸钠对土著菌进行生物刺激可实现对1,2-二氯乙烷的绿色降解.      

某石油污染含水层降解能力地球化学评估

含水层降解能力是石油类污染场地监控自然衰减需获取的重要参数.通过测定某石油污染场地地下水电子供体（苯系物、化学耗氧量）和电子受体/产物（DO、NO₃^-、Mn²⁺、Fe²⁺、SO₄^2-和HCO₃^-）等地球化学指标,分析了电子供受体分布规律,确定了电子受体背景值,采用传统地球化学评估法,计算了所有单井降解能力;在此基础上,引入累积概率曲线法,更科学的评估了场地含水层降解能力,结合地下水更新能力,估算了污染物降解速率;同时,划分了含水层降解能力强弱区.结果显示：该场地单井降解能力为36.49~70.05mg/L,其累积概率拟合曲线符合F（x）=0.008e^0.07x指数模型,以此评估含水层降解能力为57.83mg/L.以径流量132m³/d估算地下水更新能力,估算污染物降解速率为2790kg/a;强降解能力区位于下游源区,面积约为5100m²,占场地总面积的5.3%;地下水中硫酸盐、硝酸盐消耗严重,强化硫酸盐还原和反硝化作用可能是该场地管理修复的一个有效方法.     

The colorful chemistry of nanoscale zero-valent iron (nZVI)

正Nanoscale zero-valent iron(nZVI)possesses unique chemistry and capability for the separation and transformation of a growing number of environmental contaminants.A n ZVI particle consists of two nanoscale components,an iron(oxyhydr)oxides shell and a metallic iron core.This classical"core-shell"structure offers n ZVI with unique and multifaceted     

Study of Aging Characteristics of Ternary Blends of Polyethylenes—II

Six film samples of low-density polypropylene (LDPE)/linear LDPE (LLDPE)/high-density polypropylene (HDPE) with varying ratios of LDPE (20–45 ... wt%) and LLDPE (25–50 wt%) having a fixed amount of HDPE at 30 wt% were prepared by blown film extrusion technique. The samples were aged at four different temperatures, 55°, 70°, 85°, and 100°C, for four different time periods in the interval of between 150 hours and up to 600 hours. The change in the structure of various constituents and the formation of various oxygenated (peroxy and hydroperoxy) and unsaturated groups during thermo-oxidative degradation was discussed by infrared spectroscopy. The visiosity-average molecular weight was found to have decreased slowly in the initial aging hours and temperatures, whereas it decreased by 10% with its previous value tensile strength that is, 100°C when aged for 600 hours. The tensile strength of the sample first increased by 67% at 55°C and 89% at 70°C up to 450 hours, whereas the values increased by 52.5% at 85°C and 33.9% at 100°C when aged for 150 hours and then decreased. The percentage elongation at break increased by 2.7% at 55°C and 10.7% at 70°C for 150 and 300 hours of aging, respectively, whereas the percentage decreased when aged at 85°C and 100°C for up to 600 hours of aging. The values of gel content (percent) increased and initial degradation temperature decreased with aging time and temperature.     

Feature of Dust Particles in the Spring Free Troposphere over Dunhuang in Northwestern China: Electron Microscopic Experiments on Individual Particles Collected with a Balloon-borne Impactor

Free tropospheric aerosol particles were collected using a balloon-borne particle impactor in August of 2002 and March of 2003 at Dunhuang in northwestern China (40°00′N, 94°30′E), and the morphology and elemental composition of the aerosol particles were analyzed in order to understand the mixing state of coarse dust particles (diameter >1 μm) over the desert areas in the Asian continent in spring. Electron microscopic experiments on the particles revealed that dust particles were major constituents of coarse mode particles in the free troposphere over the Taklamakan Desert in spring and summer. Si-rich or Ca-rich particles are major components of dust particles collected in the free troposphere over dunhuang and the values of [number of Ca-rich particles]/[number of Si-rich particles] differs markedly between spring and summer, being about 0.3 in the spring of 2003 and about 1.0 in the summer of 2002 at heights 3–5 km above sea level. It is likely that the condition of the ground surface and the strength of vertical mixing in source areas of Asian dust are potential factors causing the difference in the chemical types of dust particles. Comparison of the elemental compositions of these particles with those of particles collected over Japan strongly suggests that these particles were chemically modified during their long-range transport in the free troposphere. Analysis of wind systems shows that both the predominating westerly wind in the free troposphere and the surface wind strongly controlled by the geographical structure of the Tarim Basin are important in the long-range transport of KOSA particles originating in the Taklamakan Desert.     

SUSPENSOIDS IN NEW YORK CITY'S DRINKING WATER RESERVOIRS: TURBIDITY APPORTIONMENT1

ABSTRACT: The technique of i ndividual p article a nalysis conducted by s canning electron microscopy interfaced with a utomated X ‐ray microanalysis (IPA/SAX) was used to characterize suspended particulate matter in New York City's drinking water reservoirs and their tributaries. The study covered a two year period and involved analyses of more than 300 samples. The particle cross sectional area per unit volume (PAV), or area concentration, was measured to account for the observed turbidity, a representation of light scattering property of the studied medium. A simple linear model with a nearly zero intercept was able to explain more than 85 percent of the variation in the measured turbidity. Moreover, the particle assemblage was categorized into generic particle types with distinctive geochemical or geological origins. Thus, PAV compositions in terms of particle types could be apportioned into turbidity components based on the model. Inorganic tripton, dominated by aluminosilicate (clay) and silicate of nonbiological nature, was found to be the major turbidity causing constituent in most cases. With the exception of one reservoir where organic detritus was significant, the predicted inorganic particle turbidity agreed with the measured turbidity within experimental error.     

Heavy Metals in Moss and Bark From Urban Area of Florence: A New Cleaness Procedure for Removing Superficial Particulate Matter

Hypnum cupressiforme epiphytic moss and tree bark (elm and holm oak) samples have been collected in three sites of the city of Florence in the period 1995-1998. Lead, zinc, copper, and cadmium were determined by differential pulse anodic stripping voltammetry (DPASV) in about 200 samples collected at different heights above ground. A new clean-up procedure by nitrogen jet has been followed and its efficiency has been also verified by electron microscopy (SEM and ESEM techniques). Lead median contents in moss and bark samples fall within the ranges of 0.052-0.86 and 0.20-1.30 μmoles g^-1 (dry weight), resulting values for moss and bark are proportional to the vehicular traffic density. the increasing use of lead-free gasoline has not been followed by a decrease of lead moss concentration.     

Topographical imaging as a means of monitoring biodegradation of poly(hydroxyalkanoate) films

Poly(hydroxyalkanoates) (PHAs) are a class of bacterially-derived polymers that are naturally biodegradable through the action of extracellular depolymerase enzymes secreted by a number of different bacteria and fungi. In this paper we describe the development of topographical imaging protocols (by both scanning electron microscopy; SEM, and confocal microscopy; CM) as a means of monitoring the biodegradation of solution cast films of poly(3-hydroxybutanoate-co-3-hydroxyhexanoate) (P3HB/3HHx) and medium-chain-length (mcl-) PHA. Pseudomonas lemoignei and Comamonas P37C were used as sources for PHA depolymerase enzymes as these bacteria are known to degrade at least one of the polymers in question. SEM revealed the bacterial colonization of the film surfaces while CM permitted the comparative assessment of the roughness of the film surfaces upon exposure to the two bacterial strains. By dividing the total surface area of the film (A′) by the total area of the scan (A) it was possible to monitor biodegradation by observing differences in the topography of the film surface. Prior to inoculation, P3HB/3HHx films had an A′/A ratio of 1.06. A 24-h incubation with P. lemoignei increased the A′/A ratio to 1.47 while a 48- and 120-h incubation with Comamonas resulted in A′/A ratios of 1.16 and 1.33, respectively. These increases in the A′/A ratios over time demonstrated an increase in the irregularity of the film surface, indicative of PHA polymer breakdown. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.