Determination of trace aqueous dimethylsulfoxide concentrations by isotope dilution gas chromatography/mass spectrometry: Application to rain and sea water

A method has been developed for determining trace quantities of dimethyl sulfoxide (DMSO) in aqueous solutions using isotope dilution gas chromatography/mass spectrometry. The method consisted of first reducing DMSO to dimethyl sulfide (DMS), followed by purge and trap preconcentration of DMS. The concentration of DMSO was determined from the signal ratio obtained for the parent ions of DMS and d₆-DMS, and the known aqueous concentration of d₆-DMSO. The precision of this method was determined to be ± 2.9 %, based on replicate DMSO determinations of a test solution prepared by adding isotopically unenriched (h₆-DMSO) to distilled water. The detection limit was 0.010 nmoles/L for the sampling conditions used in this study. This method was applied to the determination of DMSO concentrations in both rain and sea water. The concentration of DMSO in rain was found to be in the range of 2–4 nmoles/L for samples collected at an inland location (Phila, PA) and 8–11 nmoles/L for samples collected at a coastal location (Lewes, DE). Determination of DMSO in sea water required special sample preparation steps to eliminate positive interferences. A depth profile of DMS, DMSO, and dimethyl sulfoniopropionate (DMSP) concentrations is reported for sea water collected off the coast of Ocean City, Md, in August, 1990     

A simple non-linear model for the investigation of the effects of the gap closure at the abutment joints of short bridges

Closure of the gap at the abutment joints of bridges has been the source of extensive damage during the 1971 San Fernando and more recent earthquakes. In this paper a model for the investigation of the effects of this gap closure is presented and analysed. The focus of the model is the representation of the non-linear response of the bridge abutments, the foundation and the columns. The model is used for the investigation of the response of a short bridge located in California.     

Enchytraeid oligochaetes as marine pollution indicators

Fifteen species of enchytraeid oligochaetes have been collected from a pulp mill waste receiving area. Of these, one species Lumbricillus lineatus which is a known stressresistant intertidal form is predominant within 1.5 km of the mill outfall. Beyond that distance the species is replaced by a variable association of 14 other species from the genera Lumbricillus, Marionina and Enchytraeus. L. lineatus is common in Europe and eastern North America in upper intertidal drift habitats, but on the Pacific Coast is not indigenous. In British Columbia it has only been collected adjacent to three pulp mills, not at five other such mills, nor at ten undisturbed intertidal stations at each of which a diverse association of Enchytraeid species occurs. L. lineatus can serve as an index of the impact of pulp mill effluent at the site investigated. The most practical index is percentage of total adult enchytraeids represented by L. lineatus.     

Colonization of the Krakatau islands by vertebrates

80 species of non-marine, non-migrant vertebrates, excluding also shore birds, have been recorded from the Krakatau archipelago since the explosive eruption of 1883.73 of these are believed to have established breeding populations and successfully colonized the islands (47 resident land birds species, 13 bats, 11 reptiles and 2 rats). A large proportion of these colonizers consists of species with wide distributions, broad ecological tolerances and/or association with urban or rural situations. 11 of the 73 colonizing species (8 resident land birds, 2 reptiles and a bat) have become extinct on the islands. No amphibian species has yet been recorded and successful non-volant mammal colonists consist only of rats.Species turnover is considered to be largely associated with successional change of habitat. Progressive loss of coastal habitat through marine erosion and of open inland habitats through forest formation and canopy closure has been important and volcanic activity is indicated in the case of one or two extinctions.Active flight has been the predominant dispersal method (63 of the recored species, 79%, are birds or bats). Of the 17 recorded non-volant vertebrates, 6 species are assessed as having dispersed by swimming, 4 by means of natural rafts and 7 most likely through human agency (on boats). Human-assisted dispersal is seen to be of increasing importance with the increasing number of tourist visits and this may prove to be significant in determining the nature and rate of future colonization by vertebrates.     

Photographic evidence of rate of development of plant cover on the emergent island Anak Krakatau from 1971 to 1991 and implications for the effect of volcanism

Photographs of the vegetated North and East Forelands of Anak Krakatau, which emerged from the sea in 1930 and was totally devastated by volcanic activity in 1952/53 provide some evidence of rate of change of plant cover from grassland to woodland between 1971 and 1991. The series of photographs demostrate that vegetational stages of the two forelands have not been synchronous and suggest that the North Foreland is lagging the East Foreland by about 12 years.A recent hypothesis that Anak Krakatau's vegetation was destroyed, totally or almost so, by eruptions in 1972/73 and the island's vegetation has regenerated since that time is not easily accommodated by the photographic evidence, nor by the relative rates of change on Rakata (Krakatau's post-1883 remnant) and Anak Krakatau. The photographic evidence accords more closely with a hypothesis that the 1972/73 eruptions affected the North Foreland's vegetation only, or affected it to a much greater degree than that of the East Foreland, allowing the latter's post-1952/53 succession to proceed relatively unhampered.     

Reconstructing the migration patterns of late Pleistocene mammals from northern Florida, USA

We used analyses of the strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low ⁸⁷Sr/⁸⁶Sr ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of ⁸⁷Sr/⁸⁶Sr ratios. Some individuals in each taxon displayed low ⁸⁷Sr/⁸⁶Sr ratios that suggest they ranged locally, while other animals had high ⁸⁷Sr/⁸⁶Sr ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower ⁸⁷Sr/⁸⁶Sr ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns.     

Effects of coal contamination on early life history processes of a reef-building coral,Acropora tenuis

Successful reproduction and larval dispersal are important for the persistence of marine invertebrate populations, and these early life history processes can be sensitive to marine pollution. Coal is emerging as a contaminant of interest due to the proximity of ports and shipping lanes to coral reefs. To assess the potential hazard of this contaminant, gametes, newly developed embryos, larvae and juveniles of the coral Acropora tenuis were exposed to a range of coal leachate, suspended coal, and coal smothering treatments. Fertilisation was the most sensitive reproductive process tested. Embryo survivorship decreased with increasing suspended coal concentrations and exposure duration, effects on larval settlement varied between treatments, while effects on juvenile survivorship were minimal. Leachate exposures had negligible effects on fertilisation and larval settlement. These results indicate that coral recruitment could be affected by spills that produce plumes of suspended coal particles which interact with gametes and embryos soon after spawning.     

Crustal-scale prestack depth imaging of the 1994 and 1999 LARSE surveys

While seismic imaging for crustal and mantle structures has traditionally relied on surface wave and refraction data, the use of reflection data for crustal-scale targets has been largely limited to the common midpoint (CMP) stack techniques. The rapid increase in the number of seismograph array deployments in recent years in crustal and mantle seismology has reached a level such that a re-examination of the imaging techniques is becoming necessary. In this paper we show the advantage of prestack depth imaging for crustal reflection studies, based on data from two reflection surveys of the Los Angeles Regional Seismic Experiment (LARSE) to map faults and crustal-scale structures. Our analysis indicates that the quality of the previous images of these surveys is limited by the CMP stack technique. For comparison, we present here depth images of the same LARSE data using wave equation prestack depth imaging and a tomographic velocity model based on first arrivals of the LARSE surveys and local earthquakes. Our new images are considerably improved over previous images in terms of resolution and reflector continuity. The new images show reflectors throughout the crust and suggest truncations in the Moho associated with the San Andreas Fault. A series of bright reflector segments, which are associated with the San Gabriel and San Andreas faults have been identified and might represent reflections from the fault zones. Our results suggest that the presence of high noise level, strong lateral velocity heterogeneity and wide angle geometry argue for, rather than against, the use of prestack depth imaging over the simple CMP stack techniques. As demonstrated in this study, it is now viable to conduct prestack depth imaging of crustal reflection data using a velocity model based on earthquake first arrivals thanks to the dense acquisition deployment.