Porphyrin and chlorin distributions in a Late Pliocene lacustrine sediment

The tetrapyrroles in a highly immature Late Pliocene lacustrine sediment (Willershausen, Germany) show a simple distribution of both chlorin and porphyrin components as the free bases. The major components are C32 desoxophylloerythroaetioporphyrin (DPEP), a C33 bicycloalkano porphyrin, the chlorin analogue of the latter, and desoxophylloerythrin and its chlorin counterpart. The structure of the novel bicycloalkano chlorin was determined using a combination of two-dimensional phase-sensitive COSY NMR and nOe studies. Measurements of delta 13C and other data indicate that DPEP and the bicycloalkano porphyrin were derived from the chlorophyll(s) of photosynthetic organisms utilising a common source of CO2, probably diatoms. The occurrence of DPEP and other minor alkyl porphyrins indicates that the chlorophyll defunctionalisation pathway leading to these components can occur at low temperature and was probably biologically mediated, as was the condensation leading to the fused ring components.     

Development of a biocidal treatment regime to inhibit biological growths on cultural heritage: BIODAM

Existing chemical treatments to prevent biological damage to monuments often involve considerable amounts of potentially dangerous and even poisonous biocides. The scientific approach described in this paper aims at a drastic reduction in the concentration of biocide applications by a polyphasic approach of biocides combined with cell permeabilisers, polysaccharide and pigment inhibitors and a photodynamic treatment. A variety of potential agents were screened to determine the most effective combination. Promising compounds were tested under laboratory conditions with cultures of rock deteriorating bacteria, algae, cyanobacteria and fungi. A subsequent field trial involved two sandstone types with natural biofilms. These were treated with multiple combinations of chemicals and exposed to three different climatic conditions. Although treatments proved successful in the laboratory, field trials were inconclusive and further testing will be required to determine the most effective treatment regime. While the most effective combination of chemicals and their application methodology is still being optimised, results to date indicate that this is a promising and effective treatment for the control of a wide variety of potentially damaging organisms colonising stone substrates.     

Stereochemical studies of acyclic isoprenoid compounds—V. Oxidation products of Green River Formation oil shale kerogen

Gas chromatographic analysis of the major isoprenoid carboxylic acids and the major ketone (6,10,14-trimethylpentadecan-2-one), derived from successive chromic acid oxidations of the kerogen of Green River Formation oil shale, indicates that their stereochemistry is compatible with the hypothesis that phytol or a derivative with the same carbon skeleton and stereochemistry was incorporated into the kerogen matrix.     

Molecular parameters of maturation in the Toarcian shales,Paris Basin,France—III. Changes in aromatic steroid hydrocarbons

Three series of monoaromatic steroid hydrocarbons (basepeak = m/z 239, 253 and 267) and four series of triaromatic steroid hydrocarbons (basepeak = m/z 217, 231, 245 and 259) have been recognised by computerised gas chromatography-mass spectrometry in a variety of samples of Lower Toarcian shales from the Paris Basin. An increase in the extent of aromatisation of the monoaromatic steroid hydrocarbons in the m/z 253 series (measured by the abundance of monoaromatic components relative to triaromatic components in the m/z 231 series) is observed with increasing maturity. Variations between reported maximum burial depth and extent of aromatisation are explicable partly in terms of new maximum burial depth information for some of the shales. The extent of carbon-carbon bond cracking in the side chains of the aromatic steroid hydrocarbons has only begun to be significant in certain of the deepest samples.     

Mining-induced microseismicity: Monitoring and applications of imaging and source mechanism techniques

The study of microseismicity in mines provides an ideal method for remote volumetric sampling of rock masses. The nature and uniqueness of microseismic monitoring is outlined in the context of acquisition hardware and software requirements. Several topics are used to highlight the potential for novel applications of microseismicity and to outline areas where further study is required. These topics reflect some of the current interest areas in seismology, namelyb values and source parameters, fault-plane solutions, modes of failure and moment tensor inversion, imaging and seismicityvelocity correlations. These studies suggest potential correlations between zones of high seismic velocity, high microseismic activity and maximal stress drops, which can be interpreted spatially to be the locations of highly stressed ground with a potential for rock bursting. Fault-plane solutions are shown to be useful in determining the slip potential of various joint sets in a rock mass. Source parameter studies and moment tensor analysis clearly show the importance of non-shear components of failure, andb values for microseismicity appear to be magnitude-limited and related to spatial rather than temporal variations in effective stress levels.     

Occurrence and significance of pyrochlorins in a lake sediment

The occurrence of pyrochlorophyll a and pyrophaeophytins a and b in the bottom sediments of a small eutrophic lake (Priest Pot, Cumbria, U.K.) is reported on the basis of HPLC coinjection with standards. Assignment of pyrophaeophytins a and b was confirmed by FAB mass spectrometric and nuclear magnetic resonance studies of the isolated components and comparison with standards. The co-occurrence of pyrochlorins with their non-pyro counterparts, even in a surface sediment, shows that decarbomethoxylation can occur at the very earliest stages of the Treibs diagenetic pathway linking the chlorophylls and sedimentary porphyrins.     

Urban irrigation in the modeling of a semi-arid urban environment: Ballona Creek watershed,Los Angeles,California

ABSTRACT

Ballona Creek watershed in Los Angeles, California provides a unique combination of heterogeneous urban land cover, a semi-arid environment, and a large outdoor water-use flux that presents a challenge for physically-based models. We ran simulations using the Noah Land Surface Model and Parflow-Community Land Model and compared to observations of evapotranspiration (ET), runoff, and land surface temperature (LST) for the entire 11-year study period. Both models were systematically adjusted to test the impact of land cover and urban irrigation on simulation results. Monthly total runoff and ET results are greatly improved when compared to an in-situ stream gauge and meteorological tower data: from 0.64 to 0.81 for the Nash–Sutcliffe efficiency (NSE) for runoff and from a negative NSE to 0.82 for ET. The inclusion of urban irrigation in semi-arid urban environments is found to be vital, but not sufficient, for the accurate simulation of variables in the studied models.     

Stereochemical studies of acyclic isoprenoid compounds—II The role of chlorophyll in the derivation of isoprenoid-type acids in a lacustrine sediment

The stereochemistries of a series (I)–(IX) of isprenoid-type acids in the lacustrine Green River Shale (Eocene) have been examined. The absolute configurations of five of the acids present in the free-fatty acid fraction have been determined by high resolution gas Chromatographic analysis of the methyl and (?)-menthyl esters and are compatible with an origin from the phytyl moiety of chlorophyll. The results for two other isoprenoid-type acids, 5,9,13-trimethyltetradecanoic acid (IV) and 6,10,14-trimethylpentadecanoic acid (VI), do not at present preclude a chlorophyll derivation. The 4,8,12,16-tetramethylheptadecanoic (VIII) and 5,9,13,17-tetramethyloctadecanoic (IX) acids each comprise two or more stereoisomers. The stereoisomeric composition of the 2,6,10,14-tetramethylpentadecanoic acid (VI) indicates that it is unlikely that 2,6,10,14-tetramethylpentadecane, pristane, is an intermediate in the geochemical pathways presumed to lead from phytol to this acid.     

A model for assessing and managing the risks of environmental lead emissions

In response to recent activity and legislation concerning lead and its role in electric vehicle development, a model has been developed to assess the health risks to residents from environmental lead emissions. This model may be used to predict the risks to residents in the vicinity of facilities discharging lead into the air. This model is also important for risk management, allowing for risk-based regulations regarding limits on lead emissions. The model is comprehensive, linking together a source term, air dispersion model, household exposure model, physiologically-based pharmakokinetic blood-lead model, and a determination of reference dose. Parameters are treated as distributions, and are considered either uncertain or variable. A range of physiological and behavioral parameters are used to distinguish between various age and gender groups, to reflect the variability in risk of adverse effect to these subsets of the exposed population. A sensitivity study is performed, including a case considering the uncertainty in reference dose which is compared to the case of a deterministic reference dose. Different types of variability are investigated, the variability across sensitive sub-populations of age and gender, and the individual variability within these populations. We found that the differentiation between uncertainty and variability in predicting non-cancer risk human health risk was important, and that methods that combined uncertainty and variability were not expected to be protective to sensitive individuals within a sub-population.