Intensive Circulation Research Articles

Co-postseismic hydrogeochemical anomalies in a volcanic environment

Abstract. For many years flow-rate, temperature, ions and gases content data have been collected from a natural spring located in the Koryakskiy volcano area (Kamchatka, Russia). We have investigated the correlations between the hydrogeochemical data and the areal seismicity represented by the ks values (ks is a function of magnitude and hypocentral distance) of the earthquakes. At first we smoothed the raw hydrogeochemical data using a semi-triangle weight function. Then we compared the trends of each smoothed hydrogeochemical parameter with the ks trend using a running cross-correlation function with a maximum lag of ± 30 days and the main result was that, sometimes, we found 0.7–0.4 cross-correlation coefficients with no lag for flow rate and with + (10 – 15) days lags for some ion and gas contents. The correlation is positive, i.e. flow rate and ion and gas contents increase when ks increases. This phenomenology could be explained by an underground water pumping produced by some earthquake. We advance the hypothesis that this pumping could be the response of the viscoelastic underground medium of the Koryakskiy volcano to seismic waves. So, sometimes, the supply of elastic energy of the earthquakes may provide the trigger to a catastrophic nucleation of bubbles of this material producing a new melt with a lower density which will tend to expand and cause a pressure increase. This pressure produces a more intensive circulation of underground water and an anomalous increase of the flow rate and subsequently anomalous increases in groundwater ions and gases content.

Application of a fluorogenic PCR assay for typing and subtyping of influenza viruses in respiratory samples.

A fluorogenic PCR-based method (TaqMan-PCR) was developed for typing and subtyping of influenza virus genomes in clinical specimens. The TaqMan-PCR employs a probe technology that exploits the endogenous 5'-3' nuclease activity of the Taq DNA polymerase to allow direct detection of the amplicon by release of a fluorescent reporter during the PCR. Therefore, post-PCR analysis is avoided since hybridization with the fluorogenic probe and quantification of the amplified product is performed simultaneously during PCR cycling. The specificity of the method was evaluated on 86 influenza A (25 H1N1 and 61 H3N2) and 49 influenza B virus reference strains and isolates. The sensitivity of the technique was found to be at the level of 0.1 50% tissue culture infective dose. This TaqMan-PCR was applied prospectively to surveillance work by community-based sampling in Germany during the last two influenza seasons. Seven hundred five throat swabs were analyzed during the winter of 1997-1998. A total of 195 of 705 samples (28%) were positive by PCR. Influenza viruses could be isolated from 125 specimens (18%). During the 1998-1999 season, 1,840 respiratory samples were received. Influenza viruses were isolated from 281 specimens (15%) out of 525 throat swabs (29%) which were positive for influenza A or B virus by TaqMan-PCR. Further differentiation of influenza A virus-positive swabs revealed an intensive circulation of the subtype H3N2 during both seasons, 1997-1998 and 1998-1999. The TaqMan-PCR was much more sensitive than culture and revealed an excellent correlation for typing and subtyping of influenza viruses when samples were positive by both methods.

Massive barite deposits in the convergent margin off Peru: Implications for fluid circulation within subduction zones

The convergent margin of Peru, characterized by an extensional tectonic regime and the lack of a well-developed accretionary prism, has been investigated by a deep-sea submersible during the Nautiperc cruise (March–April, 1991). This allowed the collection of fluid samples, soft sediments, and barite concretions in the vicinity of biological communities associated with fluid steps. Major and trace element contents as well as strontium, oxygen, hydrogen, and sulfur isotopic compositions have been measured on fluid and/or solid samples to constrain the nature and origin of fluid circulating in this extensional tectonic context. Chemical variations with respect to bottom seawater composition have been recorded in the fluid samples and suggest the presence of a nonlocal component in the fluid expelled at the seafloor. The major variations correspond to elevations of the Cl, Na, and the Ba contents as well as the 87Sr 86Sr ratios. This is interpreted as the expulsion of a radiogenic, continent-related (basinal brine and/or meteoric water) fluid. Massive barite concretions have been collected at the seafloor in two areas of major fluid venting. The radiogenic signature (strontium isotopic composition) of the barite concretions implies that they are related to the nonlocal deep fluid component identified in the fluid samples. Furthermore, it is shown that these barite deposits testify to a hot, short, and intensive fluid circulation event. Compared to subduction zones that exhibit venting fluid with a strong oceanic water signature, the nature and origin of venting fluid along the subduction zone of Peru are different. The extensional tectonic regime of the Peru continental margin, locally associated with a dense E-W trending fault network, is an agent which may help to drain continent-related fluid as deep as the subduction scarp at the trench-slope boundary.

Water quality issues associated with aquaculture: A case study in mine pit lakes

Abandoned mine pit lakes in Minnesota are being used for intensive aquaculture, and this has resulted in real and perceived water‐quality impacts. In current net pen aquaculture operations, metabolic wastes and uneaten food are dispersed into previously oligotrophic lakewater, resulting in increased levels of phosphorus and nitrogen, oxygen depletion, and increased deposition of organic matter. Conditions necessary for algal blooms have been infrequent due to light limitation from intensive artificial aeration and circulation. Highly emotional conflicts arose over the novel use of a few of these man‐made water bodies by an industry commonly perceived to be relatively “green” and heavily promoted by state and federal governments as a rapid growth industry. The combination of the industry's “newness” on the regulatory scene, coupled with the current regulatory push toward antidegradation of groundwater and regulation of agriculture, necessitated consideration of carcinogenesis, Alzheimer's disease, and antibiotic resistance transfer in addition to more conventional considerations, such as eutrophication and wildlife impacts.

Abnormal thickness and stability of nonequilibrium liquid films.

Thick and very stable aqueous films between oil phases are obtained in systems where surfactant diffuses across the interfaces, towards the film. An osmotic pressure difference exists between the film interior and the surrounding aqueous meniscus. This is due to surfactant aggregates (micelles); it pushes the film surfaces apart, giving rise to intensive liquid circulation and exchange of mass with the meniscus.

Evolution of interstitial waters along the passive margin of the Southeast Basin of France: WELCOM (Well Chemical On-line Monitoring) applied to Balazuc-1 well (Ardèche)

As part of the Géologie Profonde de la France [GPF (Deep Geology of France)] Programme investigating the passive margin of the Southeast Basin of France, studies are being made on the possibility of modelling mass transfer. In the summer of 1990, when the first hole in the area (Balazuc-1) was being drilled along a basement-rooted fault, chemical monitoring of the drilling fluids (WELCOM) enabled the composition of the interstitial fluids contained within the intersected rocks to be reconstructed. The computations were compared to on-core leaching carried out during the drilling, following which the WELCOM results were calibrated. The interstitial fluids from the drilled formations show very contrasted compositions. From the top to the bottom of the hole it has been possible to distinguish: diagenetically evolved seawater within the Hettangian limestone, modified continental fluids within the upper part of the Triassic sandstone reservoirs, and evaporated seawater within the Middle Triassic evaporites. Several zones of intensive fluid circulation are also indicated by: dolomitization of the basal Hettangian limestone, circulation of fluids expelled from the evaporites within the upper part of Triassic sandstone reservoirs, and continental-derived hydrothermal fluid flow within the Lower Triassic sandstone reservoir and Carboniferous silty shale. The results show that chemical logging of drilling fluids can provide valuable data concerning interstitial fluids where other techniques are not available.

Iguape: a newly recognized flavivirus from São Paulo State, Brazil.

A new virus, SP An 71686, was isolated from sentinel mice exposed in a forest area in Iguape county, São Paulo state, Brazil, in 1979. The results suggest [hemagglutination inhibition (HI), complement fixation, neutralization, and ELISA] that SP An 71686 virus is a new arbovirus and that it demonstrates some cross-reactivity with other members of the family Flaviviridae, but can be differentiated from them. Although there is an intensive circulation of several arboviruses in the area, the only diagnosed cases of human disease were caused by Rocio virus during and after the epidemic of encephalitis that occurred in 1975-1977, one case of febrile illness by Caraparu virus in 1983, and by subtype IF of Venezuelan equine encephalitis virus in soldiers during jungle survival training in 1990. Wild animals had a prevalence of SP An 71686 HI monotype antibodies: 46% of birds captured in 1990, 40% in 1991 and 19.5% in 1992. These results suggested that wild birds may play a role in the virus transmission cycle. Mammals (rodents and marsupials) must also be considered potential hosts. However, the virus reservoir-vector relationships need further studies which would help to clarify the ecology of this virus.

Inflow of Neutral Gas toward the Galactic Disk

Summary:I highlight the evidence for inflow of neutral gas toward the disk of the Galaxy. The Milky Way is accreting 0.2-0.5 M⊙/yr of extragalactic atomic hydrogen at very high velocities. The interaction of infalling clouds with galactic material produces large-scale disturbances in the interstellar medium. Although the injection of energy into the galactic disk by infalling neutral gas is only 1% of the energy from supernovae, the impinging of high velocity neutral gas may be a relatively important source of energy in localized regions of the outer Galaxy.In the solar neighborhood the downfall rate of HI at intermediate velocities is 2.72 x 10-8z-1(kpc) M⊙pc-2yr-1, which if representative of the whole galactic disk, is at least 10 times more massive than the estimated accretion rate of extragalactic HI at very high velocities. This implies that most of the neutral gas that is infalling in the solar vicinity has originated in the galactic disk. It is concluded that in the Milky Way galaxy there is a moderate inflow of extragalactic neutral gas on top of a more intensive disk-halo circulation.

A comparative evaluation of the effectiveness of water-base quenching media

Out of the investigated water-base quenching media, solutions of bischofite ensured the most uniform hardness, the minimum amount of deformation, were the most serviceable in a wide range of temperatures (20–80°C), did not require intensive circulation, and had easily regulated cooling capabilities. This quenching medium is readily available, nontoxic, and inexpensive (37 rubles/ton) and is recommended for quenching material by immersion in vats of the open type.

Petrology of the mafic rocks of the Xigaze ophiolite, Tibet

The Xigaze ophiolite (Yarlung-Zangbo suture zone, Southern Tibet, China) shows an unusual crustal sequence characterized by a lack of large masses of cumulate gabbros, by dolerites intrusive throughout the whole ophiolite sequence, and by the injection of dolerites in already serpentinized peridotites. The abyssal tholeiitic nature of all the mafic rocks indicates that they have been generated at an oceanic ridge. All the geological arguments and petrological and textural data on the mafic rocks point to very low heat production and large heat losses through widespread intensive sea-water circulation, for the spreading centre in which they have been formed, in good agreement with a slow-spreading ridge origin.

ON THE GROUND-WATER DISCHARGE TO THE BALTIC SEA AND METHODS FOR ESTIMATING IT

The methods for quantitatively estimating ground-water discharge to the Baltic Sea and the possibilities of applying these methods to investigations of the role of ground water in the water and salt balances of the Baltic Sea are discussed. The combined hydrological and hydrogeological method, the hydrodynamic method, and the method of the average long-term water balance of recharge areas are recommended for general quantitative estimation of ground-water discharge to the sea. Data on the ground-water discharge to the Baltic Sea from the zone of intensive circulation (relatively shallow aquifers) within the U.S.S.R. are presented. Certain conclusions are drawn, and objectives of future investigations are mentioned.