Nutrient-limited biodegradation of PAH in various soil strata at a creosote contaminated site

The effects of nutrient addition on the in situ biodegradation of polycyclic aromatic hydrocarbons in creosote contaminated soil were studied in soil columns taken from various soil strata at a wood preserving plant in Norway. Three samples were used: one from the topsoil (0–0.5 m), one from an organic rich layer (2–2.5 m) and one from the sandy aquifer (4.5–5 m). The addition of inorganic nitrogen and phosphorous stimulated the degradation of polycyclic aromatic hydrocarbons (PAHs) in the top soil and the aquifer sand. These two soils, which differed strongly in contamination levels, responded similarly to nutrient addition with the corresponding degradation of 4-ring PAHs. The ratio between available nitrogen (N) and phosphorous (P) might explain the degree of degradation observed for the 4-ring PAHs. However, the degree of degradation of 3-ring PAHs did not significantly increase after nutrient addition. An increase in the respiration rate, after nutrient addition, could only be observed in the topsoil. In the aquifer sand, 4-ring PAH degradation was not accompanied by an increase in the respiration rate or the number of heterotrophic micro-organisms. PAH degradation in the organic layer did not respond to nutrient addition. This was probably due to the low availability of the contaminants for micro-organisms, as a result of sorption to the soil organic matter. Our data illustrate the need for a better understanding of the role of nutrients in the degradation of high molecular weight hydrocarbons for the successful application of bioremediation at PAH contaminated sites.     

白蚁表皮碳氢化合物组分鉴定及分类学意义

应用GC-MS分析表明,不同种类白蚁表皮碳氢化合物组成和含量均有差异。运用UPGMA聚合R分析的最小距离系数值绘制的系统树表明：圆唇凸额类白蚁——黄胸散白蚁Reticulitermes flaviceps、双色散白蚁R. dichrous和R. sp.1之间;圆唇平额类白蚁——圆唇散白蚁R. labralis、小头散白蚁R. microcephalus、R. sp.2和R. sp.3之间; 尖唇类白蚁——海南异白蚁Heterotermes hainanensis、拧黄异白蚁H. citrinus、细颚异白蚁H.leptomandibularis、尖唇异白蚁H. aculabialis和H. sp. 4之间的亲缘关系较近。3类白蚁中,圆唇凸额类白蚁和圆唇平额类白蚁亲缘关系相近,而两者与尖唇类白蚁亲缘关系较远。实验结果表明,我国存在异白蚁属,它与散白蚁属主要区别在于其表皮缺乏以下数种碳氢化合物：正十七烷烃、正二十烷烃、正二十一烷烃、正二十二烷烃、正二十三烷烃、正二十四烷烃和正二十六烷烃等;却含有一种特殊化合物异喹啉。表皮碳氢化合物分析的结果与形态分类的结果有一定差异,形态分类被鉴定为双色散白蚁的R. sp.1,被鉴定为小头散白蚁的R. sp.2,被鉴定为圆唇散白蚁的R.sp.3,被鉴定为尖唇散白蚁的H. sp.4,根据表皮碳氢化合物分析的结果,R. sp.1、R. sp.3和H. sp.4可能是其他种,而R. sp.2则可能是圆唇散白蚁的亚种或其他种。     

Variability of hydrocarbon and fatty acid components in cultures of the filamentous cyanobacterium Scytonema sp. isolated from microbial community "black cover" of limestone walls in Jerusalem

The hydrocarbon and lipid components of four strains of the filamentous cyanobacterium Scytonema sp. isolated from microbial community Black Cover of limestone walls in Jerusalem were identified by gas chromatography–mass spectrometry using serially coupled capillary columns. The dominant compounds were: 1-heptadecyne (1.5-8%), hexadecanoic acid (14-36%), (Z,Z)-9,12-octadecadienoic acid (12-30%), (Z,Z,Z)-9,12,15-octadecatrienoic acid (6-12%), n-heptadecane (4-16%), and 1-heptadecene (1.5-8%). In addition to unsaturated alkanes and fatty acids, the very long-chain (C₃₀-C₃₂) hydrocarbons, squalene (2.4-3.0%), and branched 4,8,12-trimethyl-C_13:0 acid were also isolated. Two major hydrocarbons were detected in the cyanobacteria species using GC-MS and ¹³C-NMR.     

A comparison between Theobroma cacao L. zygotic embryogenesis and somatic embryogenesis from floral explants

Summary In order to improve the late phases of Theobroma cacao L. embryogenesis from tissues of maternal origin, zygotic embryogenesis and somatic embryogenesis were compared, with respect to morphological, histological, and physiological parameters. Zygotic embryogenesis could be divided into three steps: (a) embryogenesis sensu stricto, (b) a growth period in which cotyledonary embryos reached their final dimensions, and (c) a maturation period in which embryos accumulated protein and starch reserves, dehydrated to a water content equal to 30%, and underwent a modification in soluble sugar composition. Monosaccharides and sucrose contents decreased to the benefit of the oligosaccharides raffinose and stachyose. The formation of somatic embryos by use of basic protocols was studied to define the limiting factors that could lie behind their poor development. Morphological abnormalities of somatic embryos, which represented 80% of the total population, were described. A histological study showed that somatic embryos lacked starch and protein reserves; moreover, their water content was much higher than that of their zygotic counterparts. Introducing a growth period into the culture protocol made for better embryo development. Adding sucrose and abscisic acid to the maturation medium was effective in increasing reserve synthesis and resulted in higher germination, conversion, and acclimatization rates.     

Characterization of PAH Sources in Sediments of the Thea Foss/Wheeler Osgood Waterways,Tacoma, Washington

The character of polycyclic aromatic hydrocarbons (PAH) in sediments of the Thea Foss and Wheeler-Osgood Waterways in Tacoma, Washington, were investigated with the objective of determining the general source(s) of these compounds to the waterways. In this study, 42 near-surface sediment samples from the Waterways were collected and analyzed for their (1) concentration of 43 individual or groups of PAH, (2) total extractable hydrocarbon “fingerprint” and concentration, (3) grain size and (4) total organic carbon content. Analysis of the sediment data, including comparisons to standard reference materials, indicates that all but two samples contained PAH derived from a pyrogenic source(s), i.e., a non-petroleum source(s). The high concentrations and characteristic distributions of PAH in some sediment samples were consistent with the occurrence of manufactured gas plant (MGP) derived tar(s) or tar distillate(s), particularly in some sediments proximal to a historic MGP and tar distillate storage operation near the head of the Thea Foss Waterway. Most other sediment samples throughout the Waterways contained PAH distributions and concentration indicating (at least) a greater proportion of PAH are derived from urban runoff/fallout.     

Cuticular Hydrocarbons of Reticulitermes (Isoptera: Rhinotermitidae) from Northern California Indicate Undescribed Species

Cuticular hydrocarbon mixtures of Reticulitermes samples from disparate locations in northern California were characterized and correlated with species determinations. Literature records indicate that there are two extant species of Reticulitermes in northern California: Reticulitermes hesperus Banks and R. tibialis Banks. We identified five distinct hydrocarbon phenotypes in Reticulitermes from northern California. Termites were diagnosed morphologically as R. tibialis for all five cuticular hydrocarbon phenotypes based on available keys to soldiers. Commonly accepted distributions of Reticulitermes in northern California indicate that our primary collection sites should only produce R. hesperus. On the basis of cuticular hydrocarbons alone we suggest that there are two or more undescribed taxa of Reticulitermes in northern California, or that described species of Reticulitermes occur in northern California, but have never been noticed before. Therefore, we conclude that the taxonomy of Reticulitermes in North America is in need of revision.     

The roles of natural and sexual selection during adaptation to a novel environment

The net effect of sexual selection on nonsexual fitness is controversial. On one side, elaborate display traits and preferences for them can be costly, reducing the nonsexual fitness of individuals possessing them, as well as their offspring. In contrast, sexual selection may reinforce nonsexual fitness if an individual's attractiveness and quality are genetically correlated. According to recent models, such good-genes mate choice should increase both the extent and rate of adaptation. We evolved 12 replicate populations of Drosophila serrata in a powerful two-way factorial experimental design to test the separate and combined contributions of natural and sexual selection to adaptation to a novel larval food resource. Populations evolving in the presence of natural selection had significantly higher mean nonsexual fitness when measured over three generations (13-15) during the course of experimental evolution (16-23% increase). The effect of natural selection was even more substantial when measured in a standardized, monogamous mating environment at the end of the experiment (generation 16; 52% increase). In contrast, and despite strong sexual selection on display traits, there was no evidence from any of the four replicate fitness measures that sexual selection promoted adaptation. In addition, a comparison of fitness measures conducted under different mating environments demonstrated a significant direct cost of sexual selection to females, likely arising from some form of male-induced harm. Indirect benefits of sexual selection in promoting adaptation to this novel resource environment therefore appear to be absent in this species, despite prior evidence suggesting the operation of good-genes mate choice in their ancestral environment. How novel environments affect the operation of good-genes mate choice is a fundamental question for future sexual selection research.     

Genotoxicity Assessment of Wood-Preserving Waste-Contaminated Soil Undergoing Bioremediation

Bioremediation represents one of the most cost-effective technologies for treatment of petroleum hydrocarbons in contaminated surface soils. A major concern for regulatory agencies when evaluating bioremediation is how to determine acceptable levels for residual organics in soil. Although guidelines have been developed for some organics in soil, limited information is available to define acceptable levels of the metabolites of biological degradation. The products of oxidative degradation are likely to be more water soluble and may also be more toxic. The purpose of the current study was to monitor changes in compound concentration and genotoxicity in soils undergoing bioremediation. The site selected for this study was a former wood-preserving site in the northwestern United States. Soil samples were collected over a 4-year period from two 6075-m² land treatment units. Conditions for biodegradation were enhanced by the addition of water and nutrients, as well as by frequent tilling to add oxygen. Due to the location of the facility, the temperature was conducive to a more rapid rate of biodegradation for approximately 6 months per year. Soil samples were collected using a grid system and solvent extracted. Polycyclic aromatic hydrocarbons were quantified in soil extracts using gas chromatography-mass spectrometry (GC/MS), and genotoxicity measured using the Salmonella/microsome assay. After 2 years of treatment, concentrations of total and carcinogenic polycyclic aromatic hydrocarbons (PAHs) were reduced to approximately 10% the concentration in the untreated soil. However, the mean weighted activity of the untreated soil was 293 net revertants per g soil, whereas the extracts of soil collected after 2 years induced a mean weighted activity of 325 net revertants per g soil. Thus, although biodegradation clearly reduced the concentration of total and carcinogenic PAHs in the surface soils, the results from the genotoxicity bioassay indicate that there was a lag in the reduction of mutagenicity in treated soils.     

Integrated Approach for Polycyclic Aromatic Hydrocarbon Solubilization from the Soil Matrix to Enhance Bioremediation

Polycyclic aromatic hydrocarbons (PAHs) are known to be toxic to living organisms and have been identified as carcinogenic. In this study, a pathway of surfactant flushing, chemical oxidation, and biological treatment is proposed to remediate the soils polluted with the hydrophobic PAHs. Different surfactants such as Tween 80, Brij 35, sodium dodecyl sulfate (SDS), and polyethylene glycol (PEG) 6000 were tested in order to increase the PAH solubilization from the soil matrix. The maximum desorption efficiency of naphthalene and anthracene were found to be 56.5% and 59%, respectively, when Brij and SDS were used. The soluble PAH in the aqueous phase was amended with sodium thiosulfate (3%) to oxidize the PAH into a more bioavailable form. The chemical oxidation with subsequent biodegradation by Pseudomonas aeruginosa exhibited the relatively high PAH degradation rate (1.24 times higher) when compared with chemical oxidation alone. These results display the efficiency of chemical pretreatment of PAH-contaminated soil for improved bioremediation.     

Human-induced changes in US biogenic volatile organic compound emissions: evidence from long-term forest inventory data

Volatile organic compounds (VOCs) emitted by woody vegetation influence global climate forcing and the formation of tropospheric ozone. We use data from over 250 000 re‐surveyed forest plots in the eastern US to estimate emission rates for the two most important biogenic VOCs (isoprene and monoterpenes) in the 1980s and 1990s, and then compare these estimates to give a decadal change in emission rate. Over much of the region, particularly the southeast, we estimate that there were large changes in biogenic VOC emissions: half of the grid cells (1°× 1°) had decadal changes in emission rate outside the range ?2.3% to +16.8% for isoprene, and outside the range 0.2–17.1% for monoterpenes. For an average grid cell the estimated decadal change in heatwave biogenic VOC emissions (usually an increase) was three times greater than the decadal change in heatwave anthropogenic VOC emissions (usually a decrease, caused by legislation). Leaf‐area increases in forests, caused by anthropogenic disturbance, were the most important process increasing biogenic VOC emissions. However, in the southeast, which had the largest estimated changes, there were substantial effects of ecological succession (which decreased monoterpene emissions and had location‐specific effects on isoprene emissions), harvesting (which decreased monoterpene emissions and increased isoprene emissions) and plantation management (which increased isoprene emissions, and decreased monoterpene emissions in some states but increased monoterpene emissions in others). In any given region, changes in a very few tree species caused most of the changes in emissions: the rapid changes in the southeast were caused almost entirely by increases in sweetgum (Liquidambar styraciflua) and a few pine species. Therefore, in these regions, a more detailed ecological understanding of just a few species could greatly improve our understanding of the relationship between natural ecological processes, forest management, and biogenic VOC emissions.