TiO2纤维光催化降解X-3B影响因素研究

采用溶胶-凝胶法及水蒸汽活化热处理工艺制备了15%(质量分数)SiO2掺杂的TiO2纤维,并利用SEM、XRD和HRTEM对其结构进行了表征.同时,以活性艳红X-3B染料水溶液为降解对象,研究了热处理温度、溶液pH值、紫外光源、溶液浓度等因素对TiO2纤维光催化活性的影响.结果表明,所制得的TiO2纤维为锐钛矿相,直径约为5～10μm;其最佳热处理温度为700℃,且在强酸(pH=2)或强碱(pH=14)条件下均表现出良好的光催化活性,并对不同浓度的X-3B溶液都有良好的降解效果,同时TiO2纤维也具有良好的可重复使用性.     

海泡石酸改性及其对直接桃红12B的吸附研究

通过试验利用硝酸、盐酸和醋酸分别对海泡石进行改性,并利用改性后的海泡石处理直接桃红12B模拟染料废水,研究了海泡石的最佳改性条件和改性海泡石对模拟染料废水色度、COD的去除效果。结果表明:采用15%的硝酸改性12h后的海泡石处理直接桃红12B模拟染料废水的效果最理想,色度去除率达83.45%,COD去除率达73.99%。     

A systems-theoretic approach for two-stage emergency risk analysis

Coronavirus disease (COVID-19) is an infectious disease that has dramatically spread worldwide. Regarding the safety issues of industries, there is a requirement of dealing with the emergency risk in the period of urgent situations. In this work, we proposed a systems-theoretic approach of the two-stage emergency risk analysis (ERA) based on the systems theory, that is the System-Theoretic Accident Model and Processes (STAMP). The two-stage ERA includes the normal to emergency risk analysis (N2E-RA) and emergency to normal risk analysis (E2N-RA). Besides N2E-RA, we advocate that E2N-RA is also an important and indispensable part of ERA. We elaborated the characteristics of N2E-RA and E2N-RA, separately. Eventually, based on our analysis, we provided recommendations for decision makers in preventing and controlling industrial accidents in the period of COVID-19.     

Coltan from Central Africa,international trade and implications for any certification

The exploitation of coltan in Central Africa can be considered a case of conflict minerals due to its nature. Many international organizations and bodies, national governments and private sector organizations seek to address this conflict, in particular via transparency, certification and accountability along the material supply chain. This paper analyses the international trade dimension of coltan and gives evidence on the dimension of illicit trade of coltan. The authors start from the hypothesis that illicit trade of coltan sooner or later will enter the market and will be reflected in the statistics. The paper is structured in the following manner: first, a short section gives a profile of coltan production and markets; second, an overview of the mining situation in the Democratic Republic of Congo (DRC) and related actors. The third section addresses mechanisms, actors and measurement issues involved in the international trade of coltan. The final part draws lessons for certification and conflict analysis and offers some guidance for future research.     

Distribution of benzo[a]pyrene in discrete regions of rat brain tissue using light microscopic autoradiography and gamma counting

In order to study the distribution of benzo[a]pyrene (B[a]P) in rat brain, Sprague-Dawley male rats, 21-day-old, weighted 40–50 g were given a single intravenous (iv) injection of 3.7 × 10⁵ Bq kg^?1 of ¹⁴C-B[a]P. Rats were sacrificed at 1, 6, 12, 24, or 48 h after the administration of radiolabeled B[a]P. Light microscopic autoradiography and gamma counting were used. Gamma counting and light microscopic autoradiography showed that ¹⁴C-B[a]P localized in hippocampus at 1 h, in cerebral cortex at 6 h, and corpus striatum at 24 h after treatment. After B[a]P administration, silver grains rose with time reaching a peak at 24 h and sharp decrease at 48 h. The silver grains distribution was higher in neurons than in gliocytes. Thus, B[a]P penetrated the blood-brain barrier and distributed in various regions of rat brain.     

疫情背景下的福建省高速公路机动车污染物排放清单

机动车排放污染物已经成为大气污染的重要来源.基于福建省高速公路交通流量数据,采用自下而上的计算方法建立了2020年1—7月福建省高速公路机动车高分辨率污染物排放清单.结果表明,受疫情影响,福建省高速公路月均车流量和污染物排放量呈先下降后上升的变化趋势,4月污染物排放量达到最低,5月污染物排放量又迅速恢复到疫情前的排放水平,其中,疫情中期污染物CO、HC、NO_x、PM_2.5和PM₁₀排放较疫情后期分别减少了90.68%、89.06%、92.58%、89.58%和89.63%.在整个研究期内,不同城市高速公路机动车污染物排放的分担率有所不同,泉州、福州和漳州的高速公路机动车排放分担率较高;从车型来看,小型客车和轻型货车是CO和HC的主要贡献车型,NO_x和PM主要来自重型货车和轻型货车;从燃料类型来看,汽油车是CO和HC的主要贡献源,柴油车则对NO_x和PM贡献突出;从排放标准来看,国三和国四车对各项污染物的贡献率最大.各项污染物空间分布一致,排放高值区位于东部沿海地区路段,西部内陆的...     

Heavy haze pollution during the COVID-19 lockdown in the Beijing-Tianjin-Hebei region, China

To investigate the characteristics of particulate matter with an aerodynamic diameter less than 2.5 μm (PM_2.5) and its chemical compositions in the Beijing-Tianjin-Hebei (BTH) region of China during the novel coronavirus disease (COVID-19) lockdown, the ground-based data of PM_2.5, trace gases, water-soluble inorganic ions, and organic and elemental carbon were analyzed in three typical cities (Beijing, Tianjin, and Baoding) in the BTH region of China from 5-15 February 2020. The PM_2.5 source apportionment was established by combining the weather research and forecasting model and comprehensive air quality model with extensions (WRF-CAMx). The results showed that the maximum daily PM_2.5 concentration reached the heavy pollution level (>150 μg/m³) in the above three cities. The sum concentration of SO₄²⁻, NO₃⁻ and NH₄⁺ played a dominant position in PM_2.5 chemical compositions of Beijing, Tianjin, and Baoding; secondary transformation of gaseous pollutants contributed significantly to PM_2.5 generation, and the secondary transformation was enhanced as the increased PM_2.5 concentrations. The results of WRF-CAMx showed obviously inter-transport of PM_2.5 in the BTH region; the contribution of transportation source decreased significantly than previous reports in Beijing, Tianjin, and Baoding during the COVID-19 lockdown; but the contribution of industrial and residential emission sources increased significantly with the increase of PM_2.5 concentration, and industry emission sources contributed the most to PM_2.5 concentrations. Therefore, control policies should be devoted to reducing industrial emissions and regional joint control strategies to mitigate haze pollution.     

Degradation of benzo[a]pyrene in an experimentally contaminated paddy soil by vetiver grass (Vetiveria zizanioides)

A pot experiment was conducted to study the effect of growing vetiver grass on the biodegradation of benzo[a]pyrene (B[a]P) under glasshouse conditions. Plant biomass, microbial biomass C and degradation of B[a]P were determined. B[a]P disappeared faster in the plant treatments than in unplanted controls. Disappearance of B[a]P was accompanied by an increase in soil microbial biomass C. Vetiver grass may promote the biodegradation of B[a]P under flooded conditions by plant roots by stimulating the microbial biomass. Microbial biomass was the main factor affecting dissipation of B[a]P under flooded conditions.     

Dissolution kinetics of high explosives particles in a saturated sandy soil

Solid phase high explosive (HE) residues from munitions detonation may be a persistent source of soil and groundwater contamination at military training ranges. Saturated soil column tests were conducted to observe the dissolution behavior of individual components (RDX, HMX, and TNT) from two HE formulations (Comp B and C4). HE particles dissolved readily, with higher velocities yielding higher dissolution rates, higher mass transfer coefficients, and lower effluent concentrations. Effluent concentrations were below solubility limits for all components at superficial velocities of 10-50 cm day(-1). Under continuous flow at 50 cm day(-1), RDX dissolution rates from Comp B and C4 were 34.6 and 97.6 microg h(-1) cm(-2) (based on initial RDX surface area), respectively, significantly lower than previously reported dissolution rates. Cycling between flow and no-flow conditions had a small effect on the dissolution rates and effluent concentrations; however, TNT dissolution from Comp B was enhanced under intermittent-flow conditions. A model that includes advection, dispersion, and film transfer resistance was developed to estimate the steady-state effluent concentrations.     

Sonographic findings in Beckwith–Wiedemann syndrome related to H19 hypermethylation

Beckwith–Wiedemann syndrome (BWS) is an overgrowth syndrome associated with congenital malformations and tumour predisposition. BWS results from variable mutations or epigenetic modifications of imprinted genes in the 11p15 chromosomal region. We present a fetus with mild general overgrowth and bilateral enlarged echogenic kidneys with loss of the corticomedullary differentiation in which prenatal diagnosis of BWS was suspected. The rest of the fetal anatomy and the amniotic fluid volume appeared normal. After termination of the pregnancy, molecular analysis confirmed the diagnosis of BWS by showing an isolated hypermethylation of the H19 gene. Copyright © 2004 John Wiley & Sons, Ltd.