Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

"Sub Tiberio quies"? Judaea’s Political Situation under the Prefects (6-41 c.e.), between Reality and Ideology

Deeply conflicting views on the political situation of Judaea under the Roman prefects (6-41 c.e.) have been offered. According to some scholars, this was a period of persistent political unrest and agitation, whilst according to a widespread view it was a quiescent period of political calm (reflected in Tacitus’ phrase sub Tiberio quies). The present article critically examines again the main available sources –particularly Josephus, the canonical Gospels and Tacitus– in order to offer a more reliable historical reconstruction. The conclusions drawn by this survey calls into question some widespread and insufficiently nuanced views on the period. This, in turn, allows a reflection on the non-epistemic factors which might contribute to explain the origin of such views.

Evolution of Transformation Texture in a Metastable B - Titanium Alloy

Texture evolution in h. c. p. (alpha) phase derived from aging of a differently processed metastable b.c.c. (beta) titanium alloy was investigated. The study was aimed at examining (i) the effect of different b. c. c. cold rolling textures and (ii) the effect of different defect structures on the h. c. p transformation texture. The alloy metastable beta alloy Ti-10V-4.5Fe-1.5Al was rolled at room temperature by unidirectional (UDR) and multi-step cross rolling (MSCR). A piece of the as-rolled materials were subjected to aging in order to derive the h. c. p. (alpha) phase. In the other route, the as-rolled materials were recrystallized and then aged. Textures were measured using X-ray as well as Electron Back Scatter Diffraction. Rolling texture of beta phase, as characterized by the presence of a strong gamma fibre, was found stronger in M S C R compared to UDR, although they were qualitatively similar. The stronger texture of MSCR sample could be attributed to the inhomogeneous deformation taking place in the sample that might contribute to weakening of texture. Upon recrystallization in beta phase field close to beta-transus. the textures qualitatively resembled the corresponding beta deformation textures; however, they got strengthed. The aging of differently beta rolled samples resulted in the product alpha-phase with different textures. The (UDR + Aged) sample had a stronger texture than (MSCR + Aged) sample, which could be due to continuation of defect accumulation in UDR sample, thus providing more potential sites for the nucleation of alpha phase. The trend was reversed in samples recrystallized prior to aging. The (MSCR + Recrystallized + Aged) sample showed stronger texture of alpha phase than the (UDR + Recrystallized + Aged) sample. This could be attributed to extensive defect annihilation in the UDR sample on recrystallization prior to aging. The (MSCR + Aged) sample exhibited more alpha variants when compared to (MSCR + Recrystallized + Aged) sample. This has been attributed to the availability of more potential sites for nucleation of alpha phase in the former. It could be concluded that alpha transformation texture depends mainly on the defect structure of the parent phase.

Efecto de exposición a deshidratación del coyolillo (Cyperus rotundus L.) sobre su densidad y el crecimiento y rendimiento del cultivo de Ajonjolí (Sesamun indicum L.) c.v. Cuyumaqui

En 1991 se estableció un ensayo en época seca (20-30 Abril) en el Centro Experimental del Algodón, Posoltega, Chinandega, con los objetivos de determinar si el efecto de diferentes tiempos de exposición a deshidratación del coyolillo (Cyperus rotundus L.) al arar el suelo en seco con arado de discos para reducir su densidad, se mantiene hasta la época de postrera y asimismo si tiene efecto sobre el crecimiento y rendimiento del cultivo de ajonjolí (Sesamun indicum L.). Para tales efectos se usó un diseño de Bloques Completos al Azar (B.C.A.) con seis tratamientos y seis repeticiones, evaluándose el factor tiempo de exposición a deshidratación del coyolillo. Los tratamientos consistieron en realizar la práctica de arar el suelo en seco en las diferentes parcelas a intervalos de dos días, empezando el 20 de abril con el tratamiento diez días y terminando el 30 de abril con el tratamiento cero días de exposición, aplic��ndose ese mismo día el riego en todo el área. Los tub��rculos quedaron expuestos a la deshidratación durante 1O, 8, 6, 4, 2 y O días. Después de establecer lo tratamientos, se sembró el 2 de mayo el cultivo de soya (Glycine max (L.) Merr.) (Época de primera) y el cultivo de ajonjolí del presente ensayo el 5 de septiembre (época de postrera). Las variables evaluadas consistieron para coyolillo: densidad y para ajonjolí: altura de plantas, número de hojas, diámetro del tallo y rendimiento. El análisis de varianza mostró significancia estadística (P < 0.05) en densidad a los 14, 28 y 42• dds, altura de plantas 42 y 89 dds, número de hojas 28 dds y diámetro del tallo 42 dds. El contraste olinomial planificado presentó significancia estadística para la tendencia lineal (P <0.05) para densidad a los 14, 28.y 42.dds, altura de plantas 14, 42y 89 dds, número de hojas 28 y 42 dds, diámetro del tallo 28 y 42 dds y rendimiento. Los mayores valores de medias para densidad de coyolillo se presentan en el tratamiento cero días y los menores valores en el tratamiento ocho días de exposición a deshidratación del coyolillo para las tres fechas de muestreo. Todas las variables evaluadas en el cultivo de ajonjolí presentan los mayores valores en el tratamiento ocho días y los menores valores en el tratamiento cero días de exposición, excepto altura 14 dds, donde el mayor valor se presenta en el tratamiento cero días y el 'menor valor en el tratamiento seis días de exposición a deshidratación del coyolillo. Los análisis de regresión realizados entre la variable independiente tiempo de exposición y las variables dependientes del coyolillo y el cultivo del ajonjolí, mostraron una respuesta de tendencia lineal negativa en densidad de coyolillo y tendencia lineal positiva en todas las variables del cultivo de ajonjolí, excepto altura 14 dds que presentó una tendencia lineal negativa.

A estrutura de atitudes e referências do imperialismo Romano em Sagunto (II a.C I d.C)

O eixo temático se desenvolveu a partir do questionamento sobre como foi o processo de reconstrução de Sagunto, que foi promovido por Roma. A região de Sagunto configura como o motivo central para o embate entre romanos e cartagineses. Todavia, com o término da Segunda Guerra Púnica (218-202 a.C.), a cidade estava destruída e uma embaixada saguntina foi enviada para Roma, a fim de solicitar ao Senado sua reorganização. O pedido aparece como sendo bem aceito pelos senadores romanos. Contudo, a partir desse momento, começa o silenciamento. A escassez de informações sobre a temática foi o primeiro problema encontrado ao longo da pesquisa. Sendo assim, foi necessário recorrer à documentação arqueológica da cidade, à numismática e à epigrafia para conseguir preencher as lacunas referentes ao tema de pesquisa. Os indícios possibilitaram não somente compreender a cidade de Sagunto e seus vários estatutos jurídicos perante Roma, como tamb��m lançar outro olhar sobre as práticas imperialistas. Ao evocar Edward Said como teórico deste trabalho, elemento de inovação da pesquisa, é possível construir a estrutura de atitudes e referências que os romanos, entre os séculos II a.C. e I d.C., aplicaram na região saguntina para consolidar o seu poder. Assim, por meio do estudo das entidades geográficas, compreende-se o espaço físico da cidade e, pelo conceito de entidades culturais, analisam-se o sistema administrativo e os colégios sacerdotais atuantes em Sagunto, no século I d.C. Logo, o imperialismo romano pode ser visto como um mecanismo que se vale de diversos elementos, os quais não se limitam à força no processo de ocupação. Em suma, política e cultura são peças centrais no processo de preservação do poder romano no espaço provincial.

Discurso e representação sobre as práticas rituais dos esparciatas e dos seus basileus na Lacedemônia, do século V a.C.

A história da pólis de Esparta como, por vezes, nos foi apresentada tomou uma perspectiva historiográfica dotada de pressupostos Atenoc��ntricos, os quais acabaram apresentando-a como rústica, dotada de uma economia e uma cultura estática e demasiadamente inclinada às atividades militares. No entanto, através de nossa pesquisa verificamos que as práticas político-culturais dos cidadãos de Esparta eram dinâmicas, para sua época. Seguindo por esse viés, verificamos que as representações de Esparta, sobretudo dos esparciatas e dos seus basileus, variaram de acordo com o grupo social e o contexto histórico em que foram empregadas. Com isso, observamos que embora os cidadãos de Esparta tenham sido, em algumas circunstâncias, criticados pelos pensadores antigos, esta não foi uma tendência hegemônica. Sendo assim, mediante os indícios da documentação literária do período Clássico, notamos que os esparciatas e os seus basileus teriam sido homens dotados de um habitus tradicional, o qual valorizava o aprimoramento físico e mental, assim como a responsabilidade com os deveres sagrados. Através da interação entre os vestígios documentais e dos estudos historiográficos mapeamos parte das representações de Esparta que figuraram os diversos discursos no decorrer da história do Ocidente, no intuito de materializarmos as possíveis motivações político-culturais nas apropriações do habitus espartano. Por conseguinte, recorremos à documentação literária para entendermos como parte dos pensadores clássicos concebeu, por meio de uma memória ancestral, a formação da região da Lacedemônia e da pólis de Esparta, a qual teria se dado concomitantemente com a legitimação político-cultural da identidade étnica dos basileus e dos esparciatas. Por fim, analisamos as práticas rituais em honra ao deus Apolo como um mecanismo empregado pelos segmentos sociais hegemônicos da Lacedemônia para ratificar o seu poder político frente a grupos sociais submetidos.

Toxicity of some organic biocides to exotic carp fingerlings Hypophthalmichthys molitrix (C and V)

A bioassay study was conducted using three organic pesticides to determine their comparative toxicity to fingerlings of Hypophthalmichthys molitrix. There was wide variation in the toxicity of different pesticides with 24 hr LC sub(50) values ranging from 0.000403 to 0.294 mg/l. Endosulfan appeared to be the most toxic, whereas BHC was the least.

云南高黎贡山白颌大角蟾的核型、C-带及Ag-NORs的研究

比较了云南高黎贡山地区的贡山独龙江和腾冲大蒿坪白颌大角蟾（Megophryslateralis）两个地理种群的核型、C-带和Ag-NORs结果表明，两个地理种群在核型和带型上都有差异两个地理种群的核型均为2n＝26，NF＝52染色体形态差异不明显，而次缢痕的位置完全不同，贡山独龙江标本的次缢痕位于No．2的长臂上近着丝点处，腾冲标本的次缢痕位于No．5的短臂上近着丝点的部位在腾冲标本中发现一雄性个体中有一条额外的染色体，可能是B���色体两地标本的C-带差异不太显著，贡山独龙江标本的C-带相对较为显著．贡山独龙江标本的Ag-NORs位于No．2长臂近着丝点处，与次缢痕的部位对应，两条同源染色体上大小有显著差异．腾冲标本的Ag-NORs位于No．5短臂上近着丝点处，与次缢痕的部位对应依据核型和带型的比较，对白颌大角蟾的分类和进化问题进行了讨论。

银额果蝇的B���色体研究 1: 昆明群体的Bs数目和频率

银额果蝇昆明群体有丝分裂中期核型中存在B���色体, 出现频率为69.1%在已 研究过的来自各个地区的银额果蝇中, 昆明群体的B���色体频率最高。B���色体 数目为1—6条。该群体内单雌系间的B���色体数目不同, 个体间和细胞间的B���色 体数目也不同。在核型中, B���色体最小, 形态稳定, 点状, C-带和G-带呈阳性 。 图版1图2表1参12

基于细胞色素b���因序列的鲤科鱼类系统发育研究(鱼纲:鲤形目)

鲤科是鱼类最大的科,在中国淡水鱼类组成中鲤科鱼类的成分占一半以上.鲤科鱼类的演化过程代表了东亚淡水鱼类的整体演化过程.为探讨东亚鲤科鱼类系统发育关系,共分析了包括18种新测序列在内的54种鲤科鱼类细胞色素b���因的全序列.分析的物种涵盖了鲤科鱼类的12个亚科并对问题较多的(鱼丹)亚科(Danioninae)和雅罗鱼亚科(Leuciscinae)进行了广泛的采样.系统发育树的建立使用了多种方法,包括邻接法、最大简约法和最大似然法.亚口鱼科(Catostomidae)的胭脂鱼(Myxocyprinus asia