Calculation of carbon balances for evaluation of the biodegradability of polymers

Establishing carbon balances has been proven to be an applicable and powerful tool in testing biodegradability of polymers. In controlled degradation tests at a 4-L scale with the model polymer poly(-hydroxybutyrate) (PHB), it was shown that the degree of degradation could not be determined with satisfactory accuracy from CO₂ release alone. Instead, the course of degradation was characterized by means of establishing carbon balances for the degradation of PHB withAcidovorax facilis and a mixed culture derived from compost. Different analytical methods for determining the different carbon fractions were adapted to the particular test conditions and compared. Quantitative determination of biomass and residual polymer were the main problems in establishing carbon balances. Amounts of biomass derived from protein measurements depend strongly on assumptions of the protein content of the biomass. Selective oxidation of biomass with hypochlorite was used as alternative, but here problems arose from insoluble metabolic products. Determination of soluble components with the method of chemical oxygen demand (COD) also includes empirical assumptions but seems acceptable if the dissolved carbon fraction is in the range of some 10% total carbon. Results confirm both analytical assays and theoretical approaches, in ending up at values very close to 100%, within an acceptable standard deviation range under test conditions comparable to standard test practice.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts.     

Geochronology and geochemistry of eclogites from the Mariánské Lázne Complex, Czech Republic: Implications for Variscan orogenesis

The Mariánské Lázn complex (MLC) is located in the Bohemian Massif along the north-western margin of the Teplá-Barrandian microplate and consists of metagabbro, amphibolite and eclogite, with subordinate amounts of serpentinite, felsic gneiss and calcsilicate rocks. The MLC is interpreted as a metaophiolite complex that marks the suture zone between the Saxothuringian rocks to the north-west and the Teplá-Barrandian microplate to the south-east. Sm-Nd geochronology of garnet-omphacite pairs from two eclogite samples yields ages of 377±7, and 367±4 Ma. Samples of eclogite and amphibolite do not define a whole rock Sm-Nd isochron, even though there is a large range in Sm/Nd ratio, implying that the suite of samples may not be cogenetic. Eclogites do not have correlated _Nd values and initial ⁸⁷Sr/⁸⁶Sr ratios. Five of the eight eclogite samples have high _Nd values (+10.2 to +7.1) consistent with derivation from a MORB-like source, but variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7059) which probably reflect hydrothermal seawater alteration. Three other eclogite samples have lower _Nd values (+ 5.4 to –0.8) and widely variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7096). Such low _Nd values are inconsistent with derivation from a MORB, source and may reflect a subduction or oceanic island basalt component in their source. The MLC is an important petrotectonic element in the Bohemian Massif, providing evidence for Cambro-Ordovician formation of oceanic crust and interaction with seawater, Late Devonian (Frasnian-Famennian) high- and medium-pressure metamorphism related to closure of a Saxothuringian ocean basin, Early Carboniferous (Viséan) thrusting of the Teplá terrane over Saxothuringian rocks and Late Viséan extension.     

单质硫自养短程反硝化耦合厌氧氨氧化强化脱氮

通过在厌氧氨氧化(ANAMMOX)连续流反应器中添加单质硫,试图引入单质硫自养短程反硝化(short-cut S~0-SADN)来强化ANAMMOX过程中NO~-_3-N的去除.在温度为(33±2)℃,pH为7.8～8.2条件下,探讨不同的进水NH~+_4-N/NO~-_2-N比对耦合系统中氮素转化以及NO~-_2-N竞争特性的影响.结果表明,在不同的进水NH~+_4-N/NO~-_2-N比(1∶1.3、 1∶1.5、 1∶1和1∶1.1)下,耦合系统的TN平均去除率分别达到了96.78%、 97.21%、 94.68%和97.72%,均远远大于ANAMMOX理论TN最高去除率89%.其中,在进水NH~+_4-N/NO~-_2-N比为1∶1或1∶1.1条件下,耦合系统能够实现单质硫自养短程反硝化耦合ANAMMOX深度脱氮的稳定运行.在最佳进水NH~+_4-N/NO~-_2-N比1∶1.1、NH~+_4-N和NO~-_2-N浓度分别为240mg·L~(-1)和265mg·L~(-1)条件下,TN去除速率达到1.50kg·(m~3·d)~(-1),ANAMMOX和S~0-SADN途径的TN去除率分别稳定在(95.68±1.22)%和(2.04±0.77)%.在整个运行过程中,ANAMMOX在底物NO~-_2-N的竞争过程中一直占据着绝对的优势,ANAMMOX菌的活性(以NH~+_4-N/VSS计)稳定在(0.166±0.008)kg·(kg·d)~(-1).     

超声协同Fe0@Fe3O4降解四氯化碳

采用附着在Fe_3O_4纳米颗粒上的纳米零价铁(n ZVI)对四氯化碳(CCl4)还原脱氯.同时,利用SEM和BET等技术对Fe~0@Fe_3O_4的表面形貌和粒径进行表征,探究了不同反应条件如Fe~0@Fe_3O_4投加量、超声功率、初始pH值、温度和CCl4初始浓度对CCl4去除率的影响.最后,比较了Fe~0@Fe_3O_4、n ZVI和Fe_3O_4颗粒对CCl4的去除效果.结果表明,Fe~0@Fe_3O_4比n ZVI比表面积更大、分散性更好.超声功率和温度的提高对CCl4的降解有明显的促进作用.在最佳条件(催化剂投加量0.5 g·L-1,超声功率300 W,初始pH=7.0,温度30℃,CCl4初始浓度2 mg·L-1)下,Fe~0@Fe_3O_4复合材料在60 min内对CCl4的去除效率为88.5%,明显高于n ZVI(60.9%)和Fe_3O_4颗粒(13.2%).Fe~0@Fe_3O_4对CCl4去除过程符合伪一级动力学模型.     

Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag

Basic oxygen furnace slag(BOFS) has the potential to remove hexavalent chromium(Cr(VI))from wastewater by a redox process due to the presence of minerals containing Fe2+. The effects of the solution p H, initial Cr(VI) concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr(VI) was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope(SEM) equipped with an energy dispersive spectrometer(EDS)system and X-ray diffractometer(XRD). The results show that Cr(VI) in wastewater can be efficiently removed by Fe2+released from BOFS under appropriate acidic conditions. The removal of Cr(VI) by BOFS significantly depended on the parameters mentioned above. The reaction of Cr(VI) with BOFS followed the pseudo-second-order kinetic model. Fe2+responsible for Cr(VI) removal was primarily derived from the dissolution of Fe O and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum(Ca SO4·2H2O)could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe2+and the removal of Cr(VI). Finally, the main mechanism of Cr(VI) removal by BOFS was described using several consecutive reaction steps.     

Assessment of risks posed by chemical industries—application of a new computer automated tool -III

The paper describes the application of a new computer automated tool, developed by us, in the risk analysis of a typical chemical industry engaged in the manufacture of linear alkyl benzene. Using the tool—a comprehensive software package -III (MAXimum CREDible accident analysis)—nine different scenarios, one for each storage unit, have been studied. It is observed that the accident scenario for chlorine (instantaneous release followed by dispersion) leads to the largest area-under-lethal-impact, while the accident scenario for propylene (CVCE followed by fireball) forecasts the most intense damage per unit area. The accidents involving propylene, benzene, and fuel oil have a high possibility of causing domino/secondary accidents as their destructive impacts (shock waves, heat load) would envelope other storage and process units.Besides demonstrating the utilizability of -III, this study also focuses attention on the need to bestow greater effort towards risk assessment/crisis management. The authors hope that the study will highlight the severity of the risk posed by the industry and thus generate safety consciousness among plant managers. The study may also help in developing accident-prevention strategies and the installation of damage control devices.     

纳米Fe、Si体系对3,3′,4,4′-四氯联苯的脱氯降解

研究了纳米Fe、Si体系降解3,3′,4,4′-四氯联苯(PCB77)的动力学差异.结果表明,纳米Fe0、纳米Fe3O4和纳米Si0对PCB77均有降解作用,该降解为还原脱氯反应.降解过程符合准一级反应动力学,反应速率常数Kobs分别为0.0177,0.0038,0.0045h-1.PCB77初始浓度为5mg/L,纳米材料投加量为5g/L,溶液pH4.5条件下,纳米Fe0体系对PCB77降解效果最为显著,64h时PCB77残留率仅为19.83%,氯离子浓度为50.3μmol/L,反应体系pH值从4.5升至5.26.纳米双元体系Fe0和Si0、Fe3O4和Si0对PCB77降解过程也符合准一级反应动力学,反应速率常数Kobs分别为0.0114,0.004h-1,其中纳米Fe0和Si0体系降解效果优于纳米Fe3O4和Si0体系.PCB77残留率分别为34.91%和66.62%,氯离子浓度分别为40.07,20.47μmol/L,反应体系pH值变化不明显.随着溶液初始pH值增加,纳米Fe0、纳米Fe3O4降解PCB77效果明显降低,但溶液pH值升高有利于纳米Si0对PCB77的降解.两组纳米双元体系对PCB77的降解效果受pH值影响小.     

V2O5/AC在含SO2气氛中对气态Hg0的吸附脱除研究

利用固定床反应器研究了模拟烟气(N_2、SO_2、O_2)气氛下,气态Hg~0在V_2O_5/AC催化剂上的吸附脱除行为.考察了V_2O_5担载量、SO_2浓度和吸附温度等对V_2O_5/AC吸附脱除Hg~0的影响,并对V_2O_5/AC上吸附汞的形态进行了XPS分析表征.研究发现,V_2O_5/AC对Hg~0的吸附能力远大于载体AC.汞的吸附量与V_2O_5/AC中V_2O_5的质量分数有关,随着V_2O_5质量分数从0.5%增加到1.0%,汞的吸附量从75.9 μg·g~(-1)增加到89.6 μg·g~(-1) (无氧) 和115.9 μg·g~(-1)增加到185.5 μg·g~(-1) (有氧),远高于相同吸附条件下的AC上的汞吸附量 (9.6 μg·g~(-1)和23.3 μg·g~(-1)).SO_2对Hg~0的吸附有促进作用,主要是由于SO_2和Hg~0在V_2O_5/AC上发生了化学反应.但是当SO_2体积分数从500×10~(-6)增加到2 000×10~(-6)时,V_2O_5/AC对汞的吸附量只增加了5%.不同温度下的实验结果表明,V_2O_5/AC催化剂在150℃左右的吸附脱除Hg~0的能力最高,汞的吸附量达到98.5 μg·g~(-1) (无氧) 和187.7 μg·g~(-1) (有氧).XPS 分析结果表明,在V_2O_5/AC催化剂表面有HgO和HgSO_4生成,证实了V_2O_5和SO_2的作用.     

MnOx/α-Al2O3催化氧化燃煤烟气中Hg0的试验研究

在模拟烟气中研究了MnOx/α-Al2O3催化剂对烟气零价汞(Hg0)的催化氧化效果,以及反应条件对Hg0氧化率的影响.结果表明,300℃时催化剂的活性最大,模拟烟气含有20mL/m2 HCI时Hg0的氧化率达到91%.在8000～32000h-1空速范围内,Hg0氧化率保持在90%以上;空速提高到96000h-1时,氧化率开始下降,并与空速成反比.烟气中的SO2与HCI竞争催化剂上的活性位,对催化氧化反应有一定抑制,500mL/m3 SO2使零价汞的氧化率下降约20%.此外,还对MnOx催化氧化零价汞的反应机制进行了探讨.     

Revealing life‐history traits by contrasting genetic estimations with predictions of effective population size

Effective population size, a central concept in conservation biology, is now routinely estimated from genetic surveys and can also be theoretically predicted from demographic, life‐history, and mating‐system data. By evaluating the consistency of theoretical predictions with empirically estimated effective size, insights can be gained regarding life‐history characteristics and the relative impact of different life‐history traits on genetic drift. These insights can be used to design and inform management strategies aimed at increasing effective population size. We demonstrated this approach by addressing the conservation of a reintroduced population of Asiatic wild ass (Equus hemionus). We estimated the variance effective size (N_ev) from genetic data () and formulated predictions for the impacts on N_ev of demography, polygyny, female variance in lifetime reproductive success (RS), and heritability of female RS. By contrasting the genetic estimation with theoretical predictions, we found that polygyny was the strongest factor affecting genetic drift because only when accounting for polygyny were predictions consistent with the genetically measured N_ev. The comparison of effective‐size estimation and predictions indicated that 10.6% of the males mated per generation when heritability of female RS was unaccounted for (polygyny responsible for 81% decrease in N_ev) and 19.5% mated when female RS was accounted for (polygyny responsible for 67% decrease in N_ev). Heritability of female RS also affected N_ev; (heritability responsible for 41% decrease in N_ev). The low effective size is of concern, and we suggest that management actions focus on factors identified as strongly affecting , namely, increasing the availability of artificial water sources to increase number of dominant males contributing to the gene pool. This approach, evaluating life‐history hypotheses in light of their impact on effective population size, and contrasting predictions with genetic measurements, is a general, applicable strategy that can be used to inform conservation practice.