Accumulation of petroleum hydrocarbons and heavy metals in clams (Ruditapes philippinarum) in Jiaozhou Bay, China

Accumulation and distributions of aliphatic and polyaromatic hydrocarbons (PAHs) and heavy metals were measured in tissues of the clam Ruditapes philippinarum collected from 5 sites in Jiaozhou Bay, Qingdao, China. The concentrations of total aliphatic hydrocarbon and PAHs ranged from 570 to 2 574 ng/gdw (gram dry weight) and from 276 to 939 ng/gdw, in the most and least polluted sites, respectively. The bio-accumulation of hydrocarbons and PAHs in the clams appeared to be selective. Aliphatic hydrocarbons were predominantly represented by short chain (< nC(23)) n-alkanes, suggesting that petroleum hydrocarbons were likely the major contamination source. The selective uptake of 3 and 4 ring PAHs, such as naphthalene, fluorene, phenanthrene, fluoranthene and pyrene, by the clams was probably related to the physiological and bio-kinetic processes that were energetically favorable for uptake of compounds with fewer rings. Accumulation of the metals Cd, Cu, Zn, Pb, Cr, Hg, and As in the clam tissues also showed high variability, ranging from 0.043 to 87 A mu g/gdw. Among the 7 detected metals, Zn, Cd, Cu, and As had a particularly high potential of accumulation in R. philippinarum. In general, a positive correlation was found between the tissue concentrations and sediment concentrations of hydrocarbons and of some metals. Our study suggests that moderate contamination with polyaromatic hydrocarbons, and low to moderate contamination with metals, currently exists for clam R. philippinarum in Jiaozhou Bay, in comparison with other regional studies. A long-term monitoring program is certainly needed for assessment of the potential ecological influence and toxicity of these contaminants of R. philippinarum in Jiaozhou Bay.

One century record of contamination by polycyclic aromatic hydrocarbons and polychlorinated biphenyls in core sediments from the southern Yellow Sea

Sixteen polycyclic aromatic hydrocarbons (PAHs) and 28 polychlorinated biphenyls (PCBs) were measured at a 2-cm interval in a core sample from the middle of the southern Yellow Sea for elucidating their historical variations in inflow and sources. The chronology was obtained using the Pb-210 method. PAHs concentrations decreased generally with depth and two climax values occurred in 14-16 cm and 20-22 cm layers, demonstrating that the production and usage of PAHs might reach peaks in the periods of 1956-1962 and 1938-1944. The booming economy and the navy battles of the Second World War might explain why the higher levels were detected in the two layers. The result of principal component analysis (PCA) revealed that PAHs were primarily owing to the combustion product. Down-cored variation of PCB concentrations was complex. Higher concentrations besides the two peaks being the same as PAHs were detected from 4 to 8 cm, depositing from 1980 to 1992, which probably resulted from the disposal of the out-dated PCB-containing equipment. The average Cl percentage of PCBs detected was similar to that of the mixture of Aroclor 1254 and 1242, suggesting they might origin from the dielectrical and heat-transfer fluid. The total organic carbon (TOC) content played a prevalent role in the adsorption of high molecular weight PAHs (>= 4-ring), while no obvious relationship among total PCBs, the concentration of congeners, and TOC was found.

Persistent organic pollutant residues in the sediments and mollusks from the Bohai Sea coastal areas, North China: An overview

The Bohai Sea costal area is one of the most developed zones of China and the sewage water from populous and developed cities, including Beijing, Tianjin. Qinhuangdao and Dalian is discharged into the Bohai Sea. Additionally, its semi-enclosed characteristic restricts water exchange, which leads to high accumulation of pollutants in the environment. This overview presents the residues of 6 classes of Persistent Organic Pollutants (POPs). including PAHs, DDTs. HCHs, PCBs and PCDD/Fs. in the sediments and mollusks of the Bohai Sea through analyzing previous literatures. In the sediments. the highest PAH concentrations were detected in the vicinities of Qinhuangdao, while the northeast corner of the Bohai Bay possessed the highest levels of DDTs and PCBs. The investigations on HCHs and PCDD/Fs distributions on the whole sea scale have not been reported. In mollusks, PAH concentrations were in the same order of magnitude in the whole Bohai Sea, so were DDTs. HCHs and PCBs, while the outlier maximum values of PCDDs and PCDFs occurred in Yingkou. In general, the POPs residues in mollusks collected from Shandong Province were higher than the other areas. The compositions of DDTs, HCHs and PCBs in sediments indicated their recent usage. By comparing POP concentrations in sediments with the recommended criterions, it was shown that some individual PAH compounds occasionally associated with adverse biological effects in the vicinities of the Liaodong Bay and Qinhuangdao, and the Liaohe River Estuary were heavily contaminated with DDTs, but PCBs were all below the thresholds. In order to reveal the transference and transformation of POPs in the environment, further studies concerning with their behavior, fate and bioaccumulation in the different trophic levels should be programmed. Moreover, laws and regulations should be enforced to ban the illegal usage of POPs-containing pesticides to guarantee health of the environment and human. (C) 2008 Elsevier Ltd. All rights reserved.

Sources and distribution of aliphatic and polyaromatic hydrocarbons in sediments of Jiaozhou Bay, Qingdao, China

The composition and distribution of aliphatic (n-alkanes) and polyaromatic hydrocarbons (PAHs) were measured for the surface sediments collected at 25 sites from Jiaozhou Bay, Qingdao, China. Total n-alkanes and PAH concentrations ranged from 0.5 to 8.2 mu g/gdw and 0.02 to 2.2 mu g/gdw, respectively, and the distribution of both n-alkanes and PAHs showed large spatial variations in the bay. The distribution of PAHs in the sediments was predominated by the three or more ring compounds. High hydrocarbon levels were generally found in the areas associated with high anthropogenic impact and port activities in the bay. The calculated hydrocarbon indexes suggest that petroleum contamination was the main source of n-alkanes, while both pyrolytic and petrogenic sources contributed PAHs to the surface sediments of Jiaozhou Bay. In comparison to other polluted coastal sediments, the level of contamination from both aliphatic hydrocarbons and PAHs in Jiaozhou Bay sediments is relatively low at the present time. (c) 2005 Elsevier Ltd. All rights reserved.

污染土壤的菌根修复

菌根是植物根系与菌根真菌形成的共生体,能有效促进污染物的降解和转化,使污染环境得以修复。阐述了多环芳烃（PAHs）、农药、重金属等污染土壤中菌根的作用,分析了菌根修复可能的机理,旨在说明利用菌根修复是生物修复的一个重要方面,具有广阔的发展前景,为进一步研究菌根的作用以及更好地运用菌根技术奠定基础。

贵阳市环境中多环芳烃的研究

多环芳烃(PAHs)是两个或两个以上苯环连接在一起的烃类化合物;环境中它主要来源于煤、石油、木材、有机高分子化合物、烟草和其他碳氢化合物的不完全燃烧.PAHs在环境中无处不在,且具有致癌性、致畸性、致突变性,生物累积性使它能长期滞留在环境中.因此PAHs的研究受到了环境工作者的极大关注.准确把握环境中多环芳烃的行为、主要来源及归宿,对有效控制污染、保护人类健康有非常重要的意义.

中国煤矿废弃物环境效应研究进展

简述煤矿废弃物的环境地球化学效应和治理方法。分别论述了煤矸石山的自燃、淋滤和煤矿矿井水的环境效应。研究发现，煤矸石自燃会释放出SO2、CO、H2S、CO2、NOx、CH4、多环芳烃(PAHs)等多种有毒有害物质；煤矸石中的有害元素As、Cd、F、Hg、Mo、Pb等含量多与硫化物、硫酸盐等正相关，连续化学浸取能将很大部分毒害元素溶出；矿井水直接排放会引起地下水位下降和环境污染。目前我国对煤矿废弃物的环境效应研究已经很重视，但煤矸石和矿井水资源化治理还存在一些问题。

天然有机质与多环芳烃相互作用的荧光光谱学研究—以苝、菲和蒽为例

自然界水体（如地下水、湖泊、河流及海洋）中的天然有机质（NOM）因具有显著的生态及环境功能而受到人们的广泛关注。NOM作为全球碳循环的主要组成部分，是水体中异养型微生物生长所需碳及能量的重要来源。此外，NOM对湖泊生态系统中的多种物理、化学过程具有不同程度的影响：NOM中的有机酸对淡水体系的酸度具有控制作用而且对酸沉降有一定的缓冲作用；NOM通过减弱可见光及紫外线照射从而影响淡水系统的光化学环境，这一方面降低了水体中自养生物的繁衍速度，同时保护水生生物免受有害的紫外线辐射。更为重要的是，NOM能够影响环境中污染物的命运，比如重金属离子和疏水性有机污染物与天然有机质结合后，其迁移途径、溶解度、生物可利用性及毒性受到明显的控制，这样其对环境中生物的危害性减弱。多环芳烃（PAHs）是一类对环境危害极大的疏水性有机污染物，多数PAHs对有机体具有毒性和致癌性而被美国环保署（EPA）列为优先处理的污染物。因此，确定NOM-PAHs反应的强弱，即PAHs在NOM中的分配系数（Kdoc）以及NOM的物化特性对Kdoc的影响对于预测PAHs毒性和生物可利用性大小、了解NOM-PAHs相互作用的机理及确立污染预测模型具有十分重大的意义。前人的研究结果表明，多环芳烃与天然有机质相互作用的分配系数Kdoc的与PAHs的疏水度（即Kow大小）、NOM的物化特性（如芳香度、脂肪碳含量、分子量及极性等）和水化学参数（pH、离子强度等）有很大的相关性。然而，许多学者在NOM的物化特性对分配系数的影响方面存有较大分歧。前人在研究天然有机质与多环芳烃之间的相互作用时所用的NOM多为腐殖质，即水体NOM中的疏水性组分，而其中的亲水性组分与PAHs的结合作用文献中却鲜见提及，因此人们对其结合作用的特性如反应机理和结合作用强弱等的了解十分有限。 本论文利用XAD树脂分离技术把红枫湖水体中天然有机质分成了疏水性酸、碱、中性物质和亲水性酸、碱、中性物质等六种有机组分。同时运用元素分析、有机碳分析仪、紫外－可见分光光度，高效液相体积排阻色谱、三维荧光光谱和荧光偏振技术等现代分析方法，对各有机组分的物理、化学特性进行了表征。荧光光谱技术被用于研究水化学参数对腐殖质荧光特性和分子构型的影响以及测定Amherst腐殖酸（Amherst HA）、垃圾渗滤液富里酸（LF FA）和红枫湖NOM有机组分与多环芳烃苝、菲和蒽的结合系数（分配系数、条件稳定常数）并探讨了影响分配系数的各种因素和NOM与多环芳烃相互作用的机理。本论文的获得的主要结果如下： 1. 在水化学参数对腐殖质荧光特性及分子构型的影响方面： 在NOM与PAHs相互作用过程中，腐殖质的分子构型起着关键性的作用，而其分子构型又受到其本身的浓度、溶液的pH和离子强度等水化学参数的影响。本论文运用三维荧光光谱和荧光偏振技术研究了水化学参数对腐殖质荧光特性的影响，并由此推断其分子构型变化情况。实验结果表明随着腐殖质浓度、溶液的pH和离子强度的改变，腐殖质荧光特性（如荧光强度、荧光峰位和荧光偏振值等）出现不同程度的变化，揭示了腐殖质分子构型的改变。因此，本实验结果有利于深入了解腐殖质的分子构型及其对吸附PAHs的重要影响，对理解NOM的环境行为具有一定的理论价值。 2. 运用荧光猝灭滴定法研究Amherst HA和红枫湖NOM有机组分对多环芳烃苝、菲和蒽的吸附作用，结果表明NOM对多环芳烃的吸附能力与其中芳香结构单元有很强的相关性，logKdoc值与NOM在280 nm处的摩尔吸收（ε280）和分子量有线性度较高的正比关系，而C/H原子比值对不饱和碳含量（芳香度）并没有很好的指示作用。同时，脂肪碳（0－50 ppm）中的聚亚甲基碳对吸附PAHs也有很大的贡献，而有机组分的极性与分配系数有明显的负相关性。不同种类的多环芳烃与NOM有机组分的结合能力有很大的差异，这取决于不同PAHs的疏水度大小。本研究结果有利于弥合前人在NOM物化特性对PAHs吸附能力的影响方面的分歧，揭示了NOM的组成和结构在与PAHs等疏水性有机污染物相互作用方面的重要影响。 3. 在结合机理方面，苝与NOM有机组分结合的Stern－Volmer图具有较高的线性度，这表明其结合机理以疏水反应（或分配）为主，而菲和蒽与有机组分相互作用的吸附等温线显示较多的非线性特征表明极性反应为主要反应机理，结合过程以吸附为主。在红枫湖NOM有机组分中，疏水性组分显示对PAHs较高的结合能力，同时疏水性组分与PAHs相互作用的吸附等温线具有较高的线性度。这一结果揭示了不同种类的PAHs和各NOM有机组分之间结合机理的差异，加深了人们对NOM与PAHs相互作用机理的认识。 4. 前人在研究pH、离子强度等水化学参数对分配系数的影响方面得到的结果多有矛盾之处，同时，对实验结果的解释也不尽相同。本实验结果表明分配系数随pH增加而下降；离子强度对分配系数的影响比较复杂，就总体趋势而言，增加离子强度有利于对PAHs吸附能力的提高，这一结果初步揭示了水化学参数对PAHs分配系数的影响，丰富了人们对其影响机理的认识。 5. 运用荧光偏振技术测定了蒽与Amherst HA、LF FA和红枫湖NOM有机组分的条件稳定常数，结果如下：随着NOM浓度增加，蒽的荧光偏振值不断下降，这表明蒽的分子构型由平面线性向圆柱状转变。在所有NOM样品中，土壤源的Amherst HA与蒽结合的条件稳定常数最大（pH 4时logK=5.6，pH 6时 logK=5.4）；就NOM有机组分而言，疏水性组分的logK变化范围在pH 6时为（4.4－5.2），而亲水性组分为（4.3－4.8），这表明疏水性组分具有相对较高的蒽吸附能力。实验结果有利于了解PAHs与NOM相互作用前后的分子构型变化情况，揭示了不同的NOM有机组分在吸附PAHs过程中的差异。

Urinary naphthalene and phenanthrene as biomarkers of occupational exposure to polycyclic aromatic hydrocarbons.

OBJECTIVES: The study investigated the utility of unmetabolised naphthalene (Nap) and phenanthrene (Phe) in urine as surrogates for exposures to mixtures of polycyclic aromatic hydrocarbons (PAHs). METHODS: The report included workers exposed to diesel exhausts (low PAH exposure level, n = 39) as well as those exposed to emissions from asphalt (medium PAH exposure level, n = 26) and coke ovens (high PAH exposure level, n = 28). Levels of Nap and Phe were measured in urine from each subject using head space-solid phase microextraction and gas chromatography-mass spectrometry. Published levels of airborne Nap, Phe and other PAHs in the coke-producing and aluminium industries were also investigated. RESULTS: In post-shift urine, the highest estimated geometric mean concentrations of Nap and Phe were observed in coke-oven workers (Nap: 2490 ng/l; Phe: 975 ng/l), followed by asphalt workers (Nap: 71.5 ng/l; Phe: 54.3 ng/l), and by diesel-exposed workers (Nap: 17.7 ng/l; Phe: 3.60 ng/l). After subtracting logged background levels of Nap and Phe from the logged post-shift levels of these PAHs in urine, the resulting values (referred to as ln(adjNap) and ln(adjPhe), respectively) were significantly correlated in each group of workers (0.71 < or = Pearson r < or = 0.89), suggesting a common exposure source in each case. Surprisingly, multiple linear regression analysis of ln(adjNap) on ln(adjPhe) showed no significant effect of the source of exposure (coke ovens, asphalt and diesel exhaust) and further suggested that the ratio of urinary Nap/Phe (in natural scale) decreased with increasing exposure levels. These results were corroborated with published data for airborne Nap and Phe in the coke-producing and aluminium industries. The published air measurements also indicated that Nap and Phe levels were proportional to the levels of all combined PAHs in those industries. CONCLUSION: Levels of Nap and Phe in urine reflect airborne exposures to these compounds and are promising surrogates for occupational exposures to PAH mixtures.

Later Life Consequences of Subteratogenic Exposure to a Complex PAH Mixture in the Atlantic Killifish (Fundulus heteroclitus)

Subteratogenic and other low-level chronic exposures to toxicant mixtures are an understudied threat to environmental and human health. It is especially important to understand the effects of these exposures for contaminants, such as polycyclic aromatic hydrocarbons (PAHs) a large group of more than 100 individual compounds, which are important environmental (including aquatic) contaminants. Aquatic sediments constitute a major sink for hydrophobic pollutants, and studies show PAHs can persist in sediments over time. Furthermore, estuarine systems (namely breeding grounds) are of particular concern, as they are highly impacted by a wide variety of pollutants, and estuarine fishes are often exposed to some of the highest levels of contaminants of any vertebrate taxon. Acute embryonic exposure to PAHs results in cardiac teratogenesis in fish, and early life exposure to certain individual PAHs and PAH mixtures cause heart alterations with decreased swimming capacity in adult fish. Consequently, the heart and cardiorespiratory system are thought to be targets of PAH mixture exposure. While many studies have investigated acute, teratogenic PAH exposures, few studies have longitudinally examined the impacts of subtle, subteratogenic PAH mixture exposures, which are arguably more broadly applicable to environmental contamination scenarios. The goal of this dissertation was to highlight the later-life consequences of early-life exposure to subteratogenic concentrations of a complex, environmentally relevant PAH mixture.

A unique population of Fundulus heteroclitus (the Atlantic killifish or mummichog, hereafter referred to as killifish), has adapted to creosote-based polycyclic aromatic hydrocarbons (PAHs) found at the Atlantic Wood Industries (AW) Superfund site in the southern branch of the Elizabeth River, VA, USA. This killifish population survives in a site heavily contaminated with a mixture of PAHs from former creosote operations. They have developed resistance to the acute toxicity and teratogenic effects caused by the mixture of PAHs in sediment from the site. The primary goal of this dissertation was to compare and contrast later-life outcomes of early-life, subteratogenic PAH mixture exposure in both the Atlantic Wood killifish (AW) and a naïve reference population of killifish from King’s Creek (KC; a relatively uncontaminated tributary of the Severn River, VA). Killifish from both populations were exposed to subteratogenic concentrations of a complex PAH-sediment extract, Elizabeth River Sediment Extract (ERSE), made by collecting sediment from the AW site. Fish were reared over a 5-month period in the laboratory, during which they were examined for a variety of molecular, physiological and behavioral responses.

The central aims of my dissertation were to determine alterations to embryonic gene expression, larval swimming activity, adult behavior, heart structure, enzyme activity, and swimming/cardiorespiratory performance following subteratogenic exposure to ERSE. I hypothesized that subteratogenic exposure to ERSE would impair cardiac ontogenic processes in a way that would be detectable via gene expression in embryos, and that the misregulation of cardiac genes would help to explain activity changes, behavioral deficits, and later-life swimming deficiencies. I also hypothesized that fish heart structure would be altered. In addition, I hypothesized that the AW killifish population would be resistant to developmental exposures and perform normally in later life challenges. To investigate these hypotheses, a series of experiments were carried out in PAH-adapted killifish from Elizabeth River and in reference killifish. As an ancillary project to the primary aims of the dissertation, I examined the toxicity of weaker aryl hydrocarbon receptor (AHR) agonists in combination with fluoranthene (FL), an inhibitor of cytochrome P4501A1 (CYP1A1). This side project was conducted in both Danio rerio (zebrafish) and the KC and AW killifish.

Embryonic gene expression was measured in both killifish populations over an ERSE dose response with multiple time points (12, 24, 48, and 144 hours post exposure). Genes known to play critical roles in cardiac structure/development, cardiac function, and angiogenesis were elevated, indicating cardiac damage and activation of cardiovascular repair mechanisms. These data helped to inform later-life swimming performance and cardiac histology studies. Behavior was assessed during light and dark cycles in larvae of both populations following developmental exposure to ERSE. While KC killifish showed activity differences following exposure, AW killifish showed no significant changes even at concentrations that would cause overt cardiac toxicity in KC killifish. Juvenile behavior experiments demonstrated hyperactivity following ERSE exposure in KC killifish, but no significant behavioral changes in AW killifish. Adult swimming performance via prolonged critical swimming capacity (Ucrit) demonstrated performance costs in the AW killifish. Furthermore, swimming performance decline was observed in KC killifish following exposure to increasing dilutions of ERSE. Lastly, cardiac histology suggested that early-life exposure to ERSE could result in cardiac structural alteration and extravasation of blood into the pericardial cavity.

Responses to AHR agonists resulted in a ranking of relative potency for agonists, and determined which agonists, when combined with FL, caused cardiac teratogenesis. These experiments showed interesting species differences for zebrafish and killifish. To probe mechanisms responsible for cardiotoxicity, a CYP1A-morpholino and a AHR2-morpholino were used to mimic FL effects or attempt to rescue cardiac deformities respectively. Findings suggested that the cardiac toxicity elicited by weak agonist + FL exposure was likely driven by AHR-independent mechanisms. These studies stand in contrast to previous research from our lab showing that moderate AHR agonist + FL caused cardiac toxicity that can be partially rescued by AHR-morpholino knockdown.

My findings will form better characterization of mechanisms of PAH toxicity, and advance our understanding of how subteratogenic mixtures of PAHs exert their toxic action in naïve killifish. Furthermore, these studies will provide a framework for investigating how subteratogenic exposures to PAH mixtures can impact aquatic organismal health and performance. Most importantly, these experiments have the potential to help inform risk assessment in fish, mammals, and potentially humans. Ultimately, this research will help protect populations exposed to subtle PAH-contamination.

Immunofluorescence detection and localization of B[a]P and TCDD in earthworm tissues

An immunohistochemical method using antibodies against polycyclic aromatic hydrocarbons (PAHs) and dioxins was developed on frozen tissue sections of the earthworm Eisenia andrei exposed to environmentally relevant concentrations of benzo[a]pyrene (B[a]P) (0.1, 10, 50 ppm) and 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) (0.01, 0.1, 2 ppb) in spiked standard soils. The concentrations of B[a]P and TCDD in E. andrei exposed to the same conditions were also measured using analytical chemical procedures. The results demonstrated that tissues of worms exposed to even minimal amount of B[a]P and TCDD reacted positively and specifically to anti-PAHs and -dioxins antibody. Immunofluorescence revealed a much more intense staining for the gut compared to the body wall; moreover, positively immunoreactive amoeboid coelomocytes were also observed, i.e. cells in which we have previously demonstrated the occurrence of genotoxic damage. The double immunolabelling with antibodies against B[a]P/TCDD and the lysosomal enzyme cathepsin D demonstrated the lysosomal accumulation of the organic xenobiotic compounds, in particular in the cells of the chloragogenous tissue as well as in coelomocytes, involved into detoxification and protection of animals against toxic chemicals. The method described is timesaving, not expensive and easily applicable.

Sediment contaminant surveillance in Milford Haven Waterway

Sediment contaminants were monitored in Milford Haven Waterway (MHW) since 1978 (hydrocarbons) and 1982 (metals), with the aim of providing surveillance of environmental quality in one of the UK’s busiest oil and gas ports. This aim is particularly important during and after large-scale investment in liquefied natural gas (LNG) facilities. However, methods inevitably have changed over the years, compounding the difficulties of coordinating sampling and analytical programmes. After a review by the MHW Environmental Surveillance Group (MHWESG), sediment hydrocarbon chemistry was investigated in detail in 2010. Natural Resources Wales (NRW) contributed their MHW data for 2007 and 2012, collected to assess the condition of the Special Area of Conservation (SAC) designated under the European Union Habitats Directive. Datasets during 2007-2012 have thus been more comparable. The results showed conclusively that a MHW-wide peak in concentrations of sediment polycyclic aromatic hydrocarbons (PAHs), metals and other contaminants occurred in late 2007. This was corroborated by independent annual monitoring at one centrally-located station with peaks in early 2008 and 2011. The spatial and temporal patterns of recovery from the 2007 peak, shown by MHW-wide surveys in 2010 and 2012, indicate several probable causes of contaminant trends, as follows: atmospheric deposition, catchment runoff, sediment resuspension from dredging, and construction of two LNG terminals and a power station. Adverse biological effects predictable in 2007 using international sediment quality guidelines, were independently tested by data from monitoring schemes of more than a decade duration in MHW (starfish, limpets), and in the wider SAC (grey seals). Although not proving cause and effect, many of these potential biological receptors showed a simultaneous negative response to the elevated 2007 contamination following intense dredging activity in 2006. Wetland bird counts were typically at a peak in the winter of 2005-2006 previous to peak dredging. In the following winter 2006-2007, shelduck in Pembroke River showed their lowest winter count, and spring 2007 was the largest ever drop in numbers of broods across MHW between successive breeding seasons. Wigeon counts in Pembroke River were again low in late 2012 after further dredging nearby. These results are strongly supported by PAH data reported previously from invertebrate bioaccumulation studies in MHW 2007-2010, themselves closely reflecting sediment

Performance of a Sequential Reactive Barrier for Bioremediation of Coal Tar Contaminated Groundwater

Following a thorough site investigation, a biological Sequential Reactive Barrier (SEREBAR), designed to remove Polycyclic Aromatic Hydrocarbons (PAHs) and BTEX compounds, was installed at a Former Manufactured Gas Plant (FMGP) site. The novel design of the barrier comprises, in series, an interceptor and six reactive chambers. The first four chambers (2 nonaerated-2 aerated) were filled with sand to encourage microbial colonization. Sorbant Granular Activated Carbon (GAC) was present in the final two chambers in order to remove any recalcitrant compounds. The SEREBAR has been in continuous operation for 2 years at different operational flow rates (ranging from 320 L/d to 4000 L/d, with corresponding residence times in each chamber of 19 days and 1.5 days, respectively). Under low flow rate conditions (320-520 L/d) the majority of contaminant removal (>93%) occurred biotically within the interceptor and the aerated chambers. Under high flow rates (1000-4000 L/d) and following the installation of a new interceptor to prevent passive aeration, the majority of contaminant removal (>80%) again occurred biotically within the aerated chambers. The sorption zone (GAC) proved to be an effective polishing step, removing any remaining contaminants to acceptable concentrations before discharge down-gradient of the SEREBAR (overall removals >95%).

Carbon chemistry in Galactic bulge planetary nebulae

Galactic bulge planetary nebulae show evidence of mixed chemistry with emission from both silicate dust and polycyclic aromatic hydrocarbons (PAHs). This mixed chemistry is unlikely to be related to carbon dredge-up, as third dredge-up is not expected to occur in the low-mass bulge stars. We show that the phenomenon is widespread and is seen in 30 nebulae out of 40 of our sample, selected on the basis of their infrared flux. Hubble Space Telescope (HST) images and Ultraviolet and Visual Echelle Spectrograph (UVES) spectra show that the mixed chemistry is not related to the presence of emission-line stars, as it is in the Galactic disc population. We also rule out interaction with the interstellar medium (ISM) as origin of the PAHs. Instead, a strong correlation is found with morphology and the presence of a dense torus. A chemical model is presented which shows that hydrocarbon chains can form within oxygen-rich gas through gas-phase chemical reactions. The model predicts two layers, one at A_V~ 1.5, where small hydrocarbons form from reactions with C+, and one at A_V~ 4, where larger chains (and by implication, PAHs) form from reactions with neutral, atomic carbon. These reactions take place in a mini-photon-dominated region (PDR). We conclude that the mixed-chemistry phenomenon occurring in the Galactic bulge planetary nebulae is best explained through hydrocarbon chemistry in an ultraviolet (UV)-irradiated, dense torus.

THE CHEMISTRY OF COMPLEX-MOLECULES IN INTERSTELLAR CLOUDS

This paper is concerned with the chemical evolution of large molecules in interstellar clouds. We consider the chemistry and ionisation balance of large polycyclic aromatic hydrocarbon (PAH) type molecules in diffuse clouds and show that certain PAH molecules can be doubly ionised by the interstellar ultraviolet radiation field. If recombination of the dications so produced with electrons is dissociative rather than radiative, then PAHs are rapidly destroyed. PAHs which can only be singly ionised have much smaller recombination energies and can be long lasting in these regions. This type of property may be very important in selecting the PAH species which can populate the general interstellar medium and account for certain of the diffuse bands observed in optical spectra. Destruction of PAH molecules via formation of dications may be responsible for the weakening of the diffuse bands observed in regions of high UV flux.