The marine polychaete Arenicola marina: its unusual arsenic compound pattern and its uptake of arsenate from seawater.

Arsenic compounds in the marine polychaete Arenicola marina collected from Odense Fjord, Denmark were determined by HPLC-ICPMS. In contrast to most other marine animals, A. marina contained most of its water soluble arsenic as inorganic forms, arsenite (58%) and arsenate (16%), and arsenobetaine was present as a minor constituent (6%) only. Other arsenic compounds detected in A. marina were dimethylarsinate (4%), two arsenosugars (1 and 3%), tetramethylarsonium ion (1.5%), and arsenocholine (<1%). A new arsenobetaine -trimethylarsoniopropionate-previously only reported in fish, was also present at trace levels (<1%), and an unknown anionic arsenical (approximately 10%) remains unidentified. When A. marina was exposed in laboratory experiments to different concentrations of arsenate in seawater (10, 50. 100, 500 and 1000 microg As 1(-1)) the polychaetes accumulated arsenic in a dose dependent. non-linear manner. Most of the accumulated arsenic was biotransformed to arsenite and dimethylarsinate. with the remainder being accumulated as unchanged arsenate. None of the other arsenic compounds naturally present in A. marina increased in concentration following arsenate exposure.     

中亚造山带中斑岩铜钼矿的Re，Pt，Pd和Au含量

Precious metal(Pt,Pd and Au)and Re contents in rocks,ores and flotation concentrates of Siberian(Russia)andMongolian porphyry Cu-Mo and Mo-Cu deposits were studied.The following deposits are discussed:Early Devonian porphyry Mo-CuSora deposit(Kuznetsk Alatau Mountains,Russia)and porphyry Cu-Mo Aksug deposit,(northeastern Tuva,Russia);Triassicporphyry Cu-Mo Erdenetiin Ovoo deposit(northern Mongolia).The samples analyzed include unaltered host rocks of plutons,porphyryrocks of ore-bearing series,different types of altered rocks,mineral separate analyses of molybdenite,chalcopyrite and magnetite,aswell as flotation concentrates.Pt,Pd,Au and Re contents were determined using ICP/MS,AAS and inversion voltammetric analysis.PGE abundances in rocks and poorly mineralized samples span a large range from below detection limit to 65 ppb Pt and 74 ppbPd.Re concentrations in whole rock samples range from below detection limit to 89 ppb.Molybdenite has been shown to be the majorhost phase for Re.The results presented show that Aksug deposit reveals elevated PGE and Au contents in ore minerals and flotationconcentrates.High Pd contents in ores of the Aksug deposit are in accordance with the presence of palladium mineralization in the formof palladium telluride merenskyite(Pd,Pt)Te_2.The variety of precious metals and Re contents in the studied deposits could be caused by a complex interplay of several factors,including importance of primary metal concentrations derived from the source,transport of metals to the deposition area,physicochemical properties of the fluid(fo_2,pH,fs,T,P),and depositional conditions.Higher Re contents in molybdenite andchalcopyrite separates are typical for copper-rich Aksug and Erdenetiin Ovoo deposits.Rhenium concentration in sulfides frommolybdenum-rich Sora deposit is significantly lower.Highly oxidized,Cl-rich fluid style at Aksug and Erdenetiin Ovoo was favorable forhigh rhenium solubility and transport to depositional area.The occurrence of significant precious metals contents at Aksug were likelydue to:1)PGE and Au enriched source,2)favorable fluid style(high fo_2,high Cl-activity),promoting high solubility andtransportation of precious metals in ore-forming fluid as chloride complexes;3)moderately reducing depositional conditions from PGE-bearing solutions containing As and Te,facilitating PGM deposition.As for the porphyry systems at the Sora and Erdenetiin Ovoodeposits,they were probably devoid of precursors favorable for the enrichment in PGE and Au or the role of such precursors wasinsignificant.     

Dispersion and cycling of organic matter from the Sepik River outflow to the Papua New Guinea coast as determined from biomarkers

The Sepik River is a major contributor of water, sediment and associated organic loads to the coastal waters of northern New Guinea. With a narrow continental shelf and strong coastal currents, much of this exported material is available for long distance transport into the Bismarck Sea and beyond. CTD casts and associated instrument data showed that the river signature was visible in optical measurements of deep profiles from the Sepik Canyon. Discrete water samples were collected in clean Niskin bottles for organic analysis. Additional high volume samples for lipid classes were collected with Infiltrex samplers deployed on a floating mooring, along with two sediment trap arrays set at 100 and 260 m depth. The Infiltrex samplers were set at 55, 180, 200 and 220 m depth in an effort to target the surface layers and those of westward flowing water in the New Guinea Coastal Undercurrent (NGCUC). The samplers allowed analysis of lipid classes in both dissolved and particulate phases.Analyses of lignin phenols, hydrocarbons, fatty acids, sterols, and n-alcohols in the samples were used to estimate the cycling of the organic input from the river system to the coastal waters and possible entrainment in the NGCUC. The molecular biomarkers confirmed the Sepik River as a significant source of reduced carbon in the near coastal zone influenced by the plume. They indicated that ca. 90% of the organic carbon delivered to the coastal zone is dispersed or degraded, with only about 10% of terrestrial carbon being deposited on to the narrow shelf of coastal sediments. The dissolved lignin phenols provided evidence for desorption of organics from particles with increasing depth. However, this desorption process did not change the C/N ratio of the dissolved organic carbon (DOC) in the deep water of the Sepik Canyon. The hydrocarbons, sterols and fatty acids showed the change from lipid content dominated by phytoplankton in surface layers to zooplankton and bacterial biomarkers in deeper waters. The organic biomarkers provided evidence that some of the dissolved organic input from the Sepik River was injected into fast moving undercurrents. However, concentrations of terrestrial biomarkers were diluted and/or degraded to non-detectable levels within 100 km of the source.     

Atomic oxygen in the comae of comets

We report on the detection of atomic oxygen lines in the spectra of 8 comets. These forbidden lines are a result of the photodissociation of the parent oxygen-bearing species directly into an excited state. We used high resolution spectra obtained at the McDonald Observatory 2.7 m telescope to resolve the cometary oxygen lines from the telluric oxygen lines and from other cometary emissions. We find that the relative intensities of the two red lines (6300.304 and 6363.776 Å) are consistent with theory. The green line (5577.339 Å) has an intensity which is about 10% of the sum of the intensities of the two red lines. We show that collisional quenching may be important in the inner coma. If we assume the relative excitation rates of potential parents which have appeared in the literature, then H₂O would be the parent of the cometary green oxygen line. However, those rates have been questioned. We measured the width of the three oxygen lines and find that the green line is wider than either of the two red lines. The finding of a wider line could imply a different parent for the green and red lines. However, the constancy of the green to red line flux ratio suggests the parent is the same for these lines but that the exciting photons have different energies.     

Chemical Composition of Dew Resulting from Radiative Cooling at a Semi-arid Site in Agra, India

Dew samples were collected between October 2007 and February 2008 from a suburban site in Agra. pH, conductivity, major inorganic ions (F^?, Cl^?, NO ₃ ^? , SO ₄ ^2? , Na⁺, K⁺, Ca²⁺, Mg²⁺, and NH ₄ ⁺ ), and some trace metals (Cr, Sn, Zn, Pb, Cd, Ni, Mn, Fe, Si, Al, V, and Cu) were determined to study the chemistry of dew water. The mean pH was 7.3, and the samples exhibited high ionic concentrations. Dew chemistry suggested both natural and anthropogenic influences, with acidity being neutralized by atmospheric ammonia and soil constituents. Ion deposition flux varied from 0.25 to 3.0?neq?m^?2?s^?1, with maximum values for Ca²⁺ followed by NH ₄ ⁺ , Mg²⁺, SO ₄ ^2? , Cl^?, NO ₃ ^? , Na⁺, K⁺, and F^?. Concentrations of trace metals varied from 0.13 to 48?μg?l^?1 with maximum concentrations of Si and minimum concentration of Cd. Correlation analysis suggested their contributions from both crustal and anthropogenic sources.     

Volcanic evolution of Volcán Aucanquilcha: a long-lived dacite volcano in the Central Andes of northern Chile

Volcán Aucanquilcha, northern Chile, has produced ∼37 km³ of dacite (63–66 wt% silica), mainly as lavas with ubiquitous magmatic inclusions (59–62 wt% silica) over the last ∼1 million years. A pyroclastic flow deposit related to dome collapse occurs on the western side of the edifice and a debris avalanche deposit occurs on the eastern side. The >6,000-m high edifice defines a 9-km E–W ridge and lies at the center of a cluster of more than 15 volcanoes, the Aucanquilcha Volcanic Cluster, that has been active for at least the past 11 million years. The E–W alignment of vents is nearly orthogonal to the arc axis. A majority of Volcán Aucanquilcha was constructed during the first 200,000 years of eruption, whereas the last 800,000 years have added little additional volume. The peak eruptive rate during the edifice-building phases was ∼0.16 km³/ka and the later eruptive rate was ∼0.02 km³/ka. Comparable dacite volcanoes elsewhere show a similar pattern of high volcanic productivity during the early stages and punctuated rather than continuous activity. Volcán Aucanquilcha lavas are dominated by phenocrysts of plagioclase, accompanied by two populations of amphibole, biotite, clinopyroxene, Fe–Ti oxides and (or) orthopyroxene. Accessory phases include zircon, apatite and rare quartz and sanidine. One amphibole population is pargasite and the other is hornblende. The homogeneity of dacite lava from Volcán Aucanquilcha contrasts with the heterogeneity (52–66 wt% silica) at nearby Volcán Ollagüe, which has been active over roughly the same period of time. We attribute this homogeneity at Aucanquilcha to the thermal development of the crust underneath the volcano resulting from protracted magmatism there, whereas Volcán Ollagüe lacks this magmatic legacy.     

Event monitoring of herbicides with naked and membrane-covered Empore disk integrative passive sampling devices

Subsequent to an initial wet season flood event in the Brisbane River, Australia, both fast (naked disk) and slow (membrane-covered) variants of SDB-RPS Empore disk passive sampling devices were deployed with an automated grab sampling program. A trend increase in the aquatic dissolved concentrations of diuron and simazine was observed over a 10-day period. Kinetic and equilibrium parameters for each sampler were calculated based on the dynamic concentration. Absolute percent difference for duplicate passive samples was <10% in the fast and <25% in the slow samplers. For kinetic sampling, significantly shortened integrative periods are available with the fast compared with the slow variant, with higher sampling rates offering improved detection limits. The study demonstrates a method for determining kinetic parameters of passive samplers in a variable concentration field deployment, and illustrates the differences in quality between active and passive data, in terms of capturing changes in concentration associated with rainfall events.     

What is the Parent of CH in the Coma of Comet C/1995 O1 (Hale-Bopp)?

The ratio of CH₄/CO in comets is an important indicator of the region of their formation. However, it is difficult to measure the quantity of CH⁺. The Giotto Ion Mass Spectrometer experiment observed a quantity of CH⁺ which seemed inconsistent with the amount of CH⁺. Thus, it was proposed that a source of the CH⁺ was a distributed source in the dust. We tested this hypothesis by observing the CH emission strength in comet Hale-Bopp as a function of dustiness. We see no strong correlation between the dust and the gas. Thus, for Hale-Bopp,dust is unlikely to be a dominant source of CH. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of flushing rates, terrestrial input and low salmon escapement densities on paleolimnological reconstructions of sockeye salmon (Oncorhynchus nerka) nutrient dynamics in Alaska and British Columbia

Recent advances in paleolimnology have enabled reconstructions of past sockeye salmon (Oncorhynchus nerka) dynamics using a number of proxy-indicators, including diatoms and stable isotopes. Thus far, studies have focused on nursery lakes with high escapement densities and low flushing rates, ensuring that levels of salmon-derived nutrients (SDN) are high and are incorporated into the food chain. This study examines three oligotrophic sockeye salmon nursery lakes in Alaska (Afognak and Saltery lakes) and British Columbia (Hobiton Lake) to determine if sockeye salmon populations can be tracked in nursery systems with lower salmon escapement densities, higher flushing rates and/or higher terrestrial input. We adopted a multi-proxy approach using diatoms, stable isotopes (¹⁵N), organic carbon to nitrogen (C/N) ratios and pollen to draw inferences from ²¹⁰Pb-dated sediment cores. ¹⁵N showed little response to historic variation in sockeye salmon populations, even in Saltery Lake, which has a very high escapement density, and in Afognak Lake, in which average escapement is known to have increased. Dilution effects due to high flushing rates were likely partly responsible for the low ¹⁵N and minimal variation throughout the cores, although very high terrestrial input in Hobiton Lake also dampened the salmon signal. Small changes in diatom species assemblages, however, were evident in all three lakes and may be in response to fluctuating loads of salmon-derived nutrients. Most notably, increases of mesotrophic diatom taxa, such as Asterionella formosa and Aulacoseira subarctica, corresponded to increased salmon production in Alaskan lakes as a result of enhancement (fertilization) activities and climatic changes. Changes in the relative abundance of Cyclotella pseudostelligera in Hobiton Lake may also be in response to a significant decline in sockeye salmon populations off the west coast of Vancouver Island in the 1970s. Other factors, however, such as logging and lake fertilization may also have influenced diatom species composition. These results confirm that, while salmon-derived nutrients may be of key importance in juvenile salmonid development in some lakes, this may not be the case in all systems, especially those in which flushing rates are high. Further, in these systems, diatom communities appear to respond more sensitively to fluctuations in salmon populations (and therefore nutrients) than stable isotope methods, provided that other changes in trophic status are minor.     

Longitudinal variability of methane and ammonia bands on jupiter: II. Temporal variations

A set of spectra was obtained of the Jovian Equatorial Zone central meridian 6190 Å CH₄ and 6450 Å NH₃ bands in February 1980, a year after the data reported by W.D. Cochran and A.L. Cochran ((1980) Icarus42, 102–110). These new data confirm the results of the previous study, and also permit a search for temporal, as well as longitudinal, variability of these molecular absorption bands. The new data set shows a correlation of NH₃ and CH₄ equivalent widths, as well as a lack of any strong correlation of red continuum reflectivity with equivalent width. These trends were also exhibited by the 1979 data. Longitude regions of larger or smaller than average equivalent width seem still to be evident a year later, with some slight drift in longitude. An increase in the average CH₄ and NH₃ equivalent width over the entire planet was detected during the one year interval. This is easily understood as the result of a global decrease in the mean altitude of the NH₃ cloud.