Physical-chemical Environment Research Articles

Factors contributing to cucumber odor in a northern USA reservoir

Episodic occurrences of cucumber odor caused by the alga Synura petersenii in Meander Creek Reservoir (MCR), northeastern Ohio, USA, are partly attributed to increased water transparency resulting from decreased phosphorus and suspended solids loading from the watershed. The first documented occurrence of nuisance odor levels was in 1984, 52 years after the reservoir was filled. This indicates that previous environmental factors constraining the growth of S. petersenii have been relaxed, probably from changes in the physical–chemical environment in the reservoir caused by changes in land use in the catchment. Reduction in farming since 1950, and diversion of sewage around the reservoir in 1977, reduced suspended solids and total phosphorus loading into the reservoir during the time that the cucumber odors occurred. These observations support the hypothesis that increased transparency of the reservoir, resulting from decreased sediment loading and reduced productivity, has permitted the occasional occurrence of nuisance densities of S. petersenii. Based on available data, pH, iron, and silica do not appear to be key factors regulating growth of S. petersenii in MCR. The transition to lower turbidity and total phosphorus concentrations from catchment restoration actions may increases the risk of S. petersenii blooms and cucumber odor episodes. While the overall benefits of cleaner raw water for water supply may outweigh this risk, it is desirable to understand the factors that promote nuisance growths and take actions to control them.

Inferring long-term changes in the physical chemical environment of the shallow, enriched Lake Nero from statistical and functional analyses of its phytoplankton

The qualitative and quantitative studies of the phytoplankton, concentration of inorganic nitrogen and phosphate and chlorophyll a in the water column and its seasonal and spatial variation have been studied in the open water of the large, shallow and highly eutrophic Lake Nero over periods representing more than one decade (1988-1989 and 1999-2003). The average qualitative characteristics of phytoplankton have remained stable over the period of observations; however, structural and functional characteristics have been highly unstable in the short term. This is controversial but may be due to the high robustness of the ecosystem to the environmental stresses. The frequencies of species within seasonal-abundance parameters have been used, together with additional data on the dominance of the community expressed in terms of evaluated Species of the Functional Groups (SFG). Correlation and factor analyses were used to estimate the strength of selected environmental factors on the development of SFG. In the periods covered by our analyses, the selected parameters were always strongly correlated with first principal components, which were dominated by properties relating to the underwater light field. According to our investigation, the phytoplankton of Lake Nero supports a commonly occurring combination S1 filamentous cyanobacteria with C diatoms and participation J greens, M and H1 dinitrogen-fixing types. It is typical of shallow, nutrient-rich lakes, comprising species that perform well under conditions of poor light. Individual species dominance caries but strictly among species making up the S1 association. Full accord with the two hypotheses of the PROTECH (Phytoplankton RespOnses To Environmental CHange) model has been demonstrated.

Rare earth element and yttrium analyses of sulfides from the Dachang Sn-polymetallic ore field, Guangxi Province, China: Implication for ore genesis

The Dachang Sn-polymetallic ore field (Guangxi, China) is one of the largest tin deposits in the world with a tin reserve of above 106 tons. Several types of orebody occur in this giant ore field, including mainly the Lamo Cu-Zn skarns at the contact of Devonian limestone and the Cretaceous Longxianggai granite, the Changpo-Tongkeng stratiform Sn-Pb-Zn ores in Devonian siliceous rocks, and the Gaofeng massive sulfide ore in Devonian reef limestone. Rare-earth element (REE) and yttrium concentrations in sulfides from different orebody types have been determined by ICP-MS. Sulfides from the Lamo skarn-type Cu-Zn mines display significant LREE-enriched pattern with large negative Eu anomalies. This is in agreement with the mineralizing fluid being of magmatic hydrothermal origin. However, sulfides from massive and stratiform orebodies show significantly different REE distributions. The Gaofeng massive sulfides have very low total REE concentrations and REE patterns range from (1) being strongly enriched in light REE with positive Eu anomalies, to (2) relatively flat patterns with strongly negative Ce and positive Eu anomalies. Pattern 1 resembles REE distributions in modern submarine hydrothermal fluids. Pattern 2 exhibits both seawater and hydrothermal vent-fluid characteristics. Sulfides from stratiform orebodies at Changpo-Tongkeng are LREE-enriched with small or no negative Eu anomalies. REE patterns of sulfides from different stratiform orebodies are slightly different, but they are similar to those of each host rock. It indicates that the sulfides and host rocks are synsedimentary and that their REE patterns are controlled by the local physical-chemical environments. Y/Ho atomic weight ratios of granite, skarn and sulfides at Lamo vary from 26.3 to 33.7, close to the chondritic Y/Ho ratio. But sulfides from massive and stratiform ores have more variable Y/Ho ratios (28.4-134) that are similar to those of many modern hydrothermal fluids. Hence, the ore-forming fluids responsible for mineralization of the stratiform and massive ores at Dachang were likely to be of exhalative hydrothermal origin. It is suggested that the Dachang deposits are formed through a two-stage hydrothermal process, i.e., the Devonian submarine hydrothermal ore-forming stage and the Yanshanian magmatic-hydrothermal ore-forming stage.

Growth and cellular differentiation: a physico-biochemical conundrum? The example of the hand

Currently, the predominant hypothesis explains cellular differentiation as an essentially genetic intracellular process. The goal of this paper is to suggest that cell growth and differentiation may be, simply, the result of physical and chemical constraints. Bone growth occurs at the level of cartilage conjunction (growth plate) in a zone of lesser constrain. It appears that this growth also induces muscle, tendon, nerve and skin elongation. This cartilage growth by itself seems to explain the elongation of the hand. Growth stops at puberty likely because of feed-back from an increasing muscle load. The ossification (that is differentiation of cartilage into bone) appears to result from the shear stress induced. The study of bone age, obtained by X-ray picture of the hand, shows that ossification of epiphyses is very precise both in time and space. Computer modelization suggests that this ossification occurs where shear stress is greatest. The cartilage which does not ossify (joint, nose, larynx, ear, bronchus, etc.) is not exposed to high shear. Shear stress induces the secretion of extracellular matrix and a change of the biochemical environment of the cell. Precipitation of calcium phosphate, as in ossification, seems related to the alkalosis induced by shear stress. To speak in more general terms, loss of cellular differentiation, as occurs with cancer, can result from a change in the physical–chemical environments.

Incorporation of Zwitterionic Push−Pull Chromophores into Hybrid Organic−Inorganic Matrixes

Dihydroxy-functionalized zwitterionic push−pull chromophores have been synthesized and incorporated into 3-glycidoxypropyltrimethoxysilane- and N-[(3-trimethoxysilyl)propyl]ethylenediamine-derived hybrid materials. The functionalization allowed the dye to form covalent bonds to the matrix network, reaching up to 5% molar concentration without aggregation. The host hybrid material was also specifically designed to reduce photobleaching of the dye and to avoid the protonation of the carbanionic species that occurs in acidic media. The host material exhibits very good film-forming properties, and thick highly transparent doped layers can be fabricated via dip-coating. Upon incorporation into the matrix, the dye exhibits a reduction of photobleaching due to the scavenger effect of the amine groups. The strong negative solvatochromism exhibited by this class of chromophores was used to probe the physical-chemical environment within the pores. Dye-functionalized hybrid sol−gel materials were submitted to poling...

Solvatochromism of the Excitation and Emission Spectra of 7-Aminoactinomycin D: Implications for Drug Recognition of DNA Secondary Structures

The antitumor antibiotic 7-aminoactinomycin D has been previously demonstrated to bind and stabilize transient hairpin structures formed by single-stranded DNA. Those experiments suggested that DNA secondary structures are viable targets for development of novel antitumor or antiviral compounds. Interestingly, when 7-aminoactinomycin D binds to hairpins formed by selected single-stranded DNAs having a high affinity for the drug, the fluorescence quantum yield, average fluorescence lifetime, excitation wavelengths, and emission wavelengths for the drug are significantly different from those observed when it is free in solution or bound to duplex, B-form DNA. This suggests a unique physical chemical environment within certain DNA hairpins that is specifically recognized by the drug. To understand the environmental contribution to the fluorescence properties of the bound drug, we used solvatochromism techniques, whereby 7-aminoactinomycin D fluorescence properties were determined in 20 solvents with known po...

SOIL FAUNA AND PLANT LITTER DECOMPOSITION IN TROPICAL AND SUBALPINE FORESTS

The decomposition of plant residues is influenced by their chemical composition, the physical–chemical environment, and the decomposer organisms. Most studies interested in latitudinal gradients of decomposition have focused on substrate quality and climate effects on decomposition, and have excluded explicit recognition of the soil organisms involved in the process. To test whether soil fauna exhibit different effects under diverse climates or substrates, we quantified decomposition rates and N fluxes in control and fauna-excluded treatments with litterbags containing relatively high-quality (Quercus gambelii) and low-quality (Cecropia scheberiana) litter in sites representing large differences in climate as measured by AET (actual evapotranspiration). Two subtropical sites included a wet and a dry forest, and two temperate sites included north- and south-facing subalpine forests. We found that: (1) all three factors (climate, substrate quality, and soil fauna) independently influenced the decomposition rate of plant litter in the tropical and subalpine forests; (2) faunal effects on decomposition rates and N mineralization of Q. gambelii and C. scheberiana were consistently higher in the tropical wet forest than in the tropical dry and subalpine forests; (3) there was no significant interaction of fauna and litter species on the annual decay rates; and (4) the density (numbers per gram of dry litter) of total fauna was highest in the tropical wet forest, intermediate in the subalpine forests, and lowest in the tropical dry forest. Our results indicate that soil fauna have a disproportionately larger effect on litter decomposition in a tropical wet forest than in a tropical dry or a subalpine forest. The annual decay rates of Q. gambelii and C. scheberiana are not influenced differentially by the soil fauna in the tropical and subalpine forests.

The possible role of volcanic aquifers in prebiologic genesis of organic compounds and RNA.

In a volcanic aquifer, a wide range of physical and chemical conditions are not merely possible, but to be expected: relatively oxidizing and reducing environments both are present; hot and moderate temperatures can be expected; distillation and reflux conditions are probable to allow concentration of reactants, stimulation of reaction and fractionation of isotopes; apatite, hydroxides, clays and sulfide minerals are present to act as chromatographic media for separating compounds, to serve as catalytic surfaces and to provide potential energy sources; supersaturated precipitation of optically active crystals is reasonable, allowing for chromatographic separation of racemic mixtures by the resulting fixed chiral phase; and saturated and unsaturated conditions both are present for promotion of constructive reactions and inhibiting destructive hydrolysis reactions. Because the multitude of physical-chemical environments makes the setting robust with respect to circumventing commonly identified problems in origin-of-life theories, even if objections to details proposed herein are identified, the setting is favorable for devising alternatives. This paper describes a theory for the genesis of organic compounds, including RNA, in the mixing zone of juvenile and meteoric waters above a leaky semi-confined aquifer. Starting with basic reactants for best-guess conditions on Archean Earth, parallel sequences of specific reactions are proposed that culminate with RNA oligonucleotides, key molecules in contemporary life. All proposed reactions, or close analogues, are experimentally confirmed and all are set in plausible Archean conditions. Calculations indicate that the proposed reactions would yield C isotopic compositions that are consistent with observed biologic C.

Polypeptide Chain Folding in the Hydrophobic Core of Hamster Scrapie Prion: Analysis by X-Ray Diffraction

Conversion of the noninfectious, cellular form of the scrapie prion (PrPC) to the infectious form (PrPSc) is thought to be driven by an α-helical to β-sheet conformational transition. The N-truncated polypeptide PrP27–30, which encompasses residues 90–231 of PrPScand from which the truncated peptide is derived by limited proteolysis, assembles into amyloid rods that are rich in the β-sheet conformation. The N-terminal half of PrP27–30, which includes residues 90–145 of PrP (SHa90–145) and contains the two putative α-helical domains H1 (PrP109–122) and H2 (PrP129–141), appears to be particularly crucial in the α → β conversion. To assess their role in this conformational transition, we have analyzed in detail X-ray diffraction patterns from the prion-related peptides A8A (PrP113–120), H1, and SHa90–145. We used iterative Fourier synthesis with β-silk as an initial model for assigning phases. For H1, the lyophilized and acetonitrile-solubilized/dehydrated specimens gave two different electron density maps. The former showed that the β-sheets were composed of small side chains as in A8A. The latter showed two types of β-sheets having smaller and larger side chains, suggesting a turn. Such a turn was not observed in the lyophilized H1, indicating that the internal turn in H1 depends on the physical–chemical environment. In SHa90–145, the β-chains are assembled in ≈40 Å-wide crystal domains (termed β-crystallites), and the electron density maps of these crystallites showed evidence for turns within both the H1 and H2 domains. The molecular folding of H1–H2 is compared here with the recent NMR solution structure of recombinant hamster prion, and the effect of pH on the conformational change is discussed. The most compact structure based on the X-ray diffraction analysis showed that the N-terminal, smaller residues of H2 fold back and are hydrogen-bonded with the C-terminal, smaller residues of H1. Similar folding is observed in the NMR solution structure. Comparison of the NMR structures at different pH with the X-ray diffraction results suggests that histidine and lysine residues in the N-terminal sequence of PrP may figure in the α → β structure transition of PrP.

Spatial and Temporal Changes in Subtidal Benthic Crustaceans Along a Coastal River-Estuarine Gradient in Mississippi

Benthic crustaceans were collected monthly between 24 August 1985 and 20 September 1986 from tidal freshwater (TFW), oligohaline (OH) and mesohaline (h4H) sites in Old Fort Bayou, a black-water tidal river of the Biloxi Bay estuary, Mississippi. Salinity varied seasonally and spatially and was primarily related to variations in rainfall during this study. Reduced rainfall after October 1985 resulted in the upstream movement of saline water and a concommitant shift in benthic crustaceans upstream with this change in the physical-chemical environment. This shift is supported by a significant positive concordance of ranks between salinity and relative abundance of Gammarus sp. A (Kendall's tau-c = 0.458 and Spearman's rs = 0.704, p<0.007) and G. mucromatus (Kendall's tau-c = 0.497 and Spearman's r, = 0.701, p <0.007) at TFW indicating that when salinity became high, so did the relative abundance of these two species in TFW. No specimens of either species were collected at this site during the same months in 1985. There was no relationship between salinity and relative abundance of G. bonnieroides (Kendall's tau-c = 0.201 and Spearman's rs = 0.381, p = 199) in the TFW site. At the OH site, there was a marginally significant concordance (Kendall's tau+ = 0.432 and Spearman's rp = 0.545, p = .053) between salinity and relative abundance of G. bonnieroides but not for the other two species. Riverine estuarines are by nature dynamic in their physicalchemical environment. Such variation influences macrobenthic distribution which has important trophic implications because these organisms form a large portion of the food base for higher trophic levels, such as fishes.

Alteration of uraninite from the Nopal I deposit, Pen˜a Blanca District, Chihuahua, Mexico, compared to degradation of spent nuclear fuel in the proposed U.S. high-level nuclear waste repository at Yucca Mountain, Nevada

At the Nopal I uranium deposit, primary uraninite (nominally UO 2+ x ) has altered almost completely to a suite of secondary uranyl minerals. The deposit is located in a Basin and Range horst composed of welded silicic tuff; uranium mineralization presently occurs in a chemically oxidizing and hydrologically unsaturated zone of the structural block. These characteristics are similar to those of the proposed U.S. high-level nuclear waste (HLW) repository at Yucca Mountain, Nevada. Petrographic analyses indicate that residual Nopal I uraninite is fine grained (5–10 μm) and has a low trace element content (average about 3 wt%). These characteristics compare well with spent nuclear fuel. The oxidation and formation of secondary minerals from the uraninite have occurred in an environment dominated by components common in host rocks of the Nopal I system (e.g. Si, Ca, K, Na and H 2O) and also common to Yucca Mountain. In contrast, secondary phases in most other uranium deposits form from elements largely absent from spent fuel and from the Yucca Mountain environment (e.g. Pb, P and V). The oxidation of Nopal I uraninite and the sequence of alteration products, their intergrowths and morphologies are remarkably similar to those observed in reported corrosion experiments using spent fuel and unirradiated UO 2 under conditions intended to approximate those anticipated for the proposed Yucca Mountain repository. The end products of these reported laboratory experiments and the natural alteration of Nopal I uraninite are dominated by uranophane [nominally Ca(UO 2) 2Si 2O 7·6H 2O] with lesser amounts of soddyite [nominally (UO 2) 2SiO 4·2H 2O] and other uranyl minerals. These similarities in reaction product occurrence developed despite the differences in time and physical—chemical environment between Yucca Mountain-approximate laboratory experiments and Yucca Mountain-approximate uraninite alteration at Nopal I, suggesting that the results may reasonably represent phases likely to form during long-term alteration of spent fuel in a Yucca Mountain repository. From this analogy, it may be concluded that the likely compositional ranges of dominant spent fuel alteration phases in the Yucca Mountain environment may be relatively limited and may be insensitive to small variations in system conditions.

Forest reconstruction as ecological engineering

Land restoration involves reconstruction of the native biota in a sustainable form. If reconstruction involves deliberate manipulation of biological organisms and the physical-chemical environment to achieve specific human goals, it qualifies as ecological engineering. Restoration which uses natural processes to achieve endpoints which are unpredictable but can be accepted because they are “natural” is not ecological engineering. In Japan a system of forest reconstruction has been developed which is based on knowledge of the potential vegetation of a site, knowledge of the methods of germination and growth of the species which compose the mature vegetation and a method of site preparation and planting. This ecological engineering approach has been used on 285 sites, in a variety of habitats, to form dense stands of vegetation to hide industrial complexes, control visual, noise and chemical pollution, stabilize soil and beaches and provide urban green space. The technique has also been used to restore tropical rain forest.

On the nature of vegetation boundaries, undisturbed flood plain forest communities as an example — a contribution to the continuum/discontinuum controversy

The goal of the present study resides in the attempt to falsify the discontinuum hypothesis. To this end the local variation in vegetation structure along a continuously changing environmental gradient was studied. The object under study was a 116 m long transect in the unspoiled flood plain forests of the Sava valley in Croatia, which contains stands of three widespread forest community types. The soil water conditions function as an independent variable of the physical-chemical environment, influencing the vegetation structure. It gradually changes within the transect according to relief height. By contrast ceteris paribus conditions obtain for climatic relations and nutrient supply. The investigation is based on 116 sample plots in all, each of 8 square metres in area. The type of structural change is elucidated by means of a vegetation table, presentation of the frequency distribution of plant species, a contingency table, non-metric multidimensional scaling, a discriminant function and a cluster analysis. Variation in relief height produces a continuous change in the forest vegetation. Nevertheless, there are clearly recognisable leaps between, and a clear clustering of plant species within, the stands of the various community types. The type of structural change corresponds to the ‘Non-linear and continuous’ — ‘Tendency for association’ model, and the pattern of distribution of plant species corresponds to the ‘Clustered distributions’ model of Scott (1974). In this connection, discussion is conducted about the question of the organisation of plant communities and whether it is possible to classify them.

The stable isotope geochemistry of acid sulfate alteration

The stable isotope geochemistry of acid sulfate alteration

Scanning electron microscope study of fused crust and fuse leakage veins in Jilin meteorite

On the fused crust surface of Jilin meteorite, various morphological characteristics are developed. Profile stratified layers and fused crust material percolation into tension fissures forming fuse leakage veins are noticed. This reflects the physical-chemical environment of the meteorite body in its falling passage.

Clay-Mineral Distribution in Permo-Pennsylvanian Shales of Val Verde Basin and Yates-Todd Arch, Texas

The purpose in studying the clay-mineral distribution in the Val Verde basin, Yates-Todd arch, and Midland basin of West Texas is to obtain information which will aid in working out the geologic history in this area. A knowledge of the geologic history will aid in locating oil or gas accumulations beneath the Permo-Pennsylvanian shale interval. A clay-mineral stratigraphic framework has been constructed from identifications of the clay minerals contained in these Permo-Pennsylvanian shales. Clay-mineral ratio profiles have been plotted from analyses of samples from 20 wells to make up this framework. Three clay-mineral zones can be traced consistently through the cross section represented by these wells. A lower zone (Zone I) contains illite, chlorite, kaolinite, mixed-layer clay, and small amounts of montmorillonite. A middle zone (Zone II) contains illite and minor amounts of chlorite, kaolinite and mixed-layer clay. Mixed-layer clay in this zone, however, is more abundant than in Zone I. An upper zone (Zone III) contains a richer assemblage of clays and is more variable than the two lower zones. The characteristic clays of Zone III are illite, chlorite, kaolinite, montmorillonite, vermiculite (?), and mixed-layer clay. Throughout most of the framework, the clay-mineral zone boundaries are favorably comparable with tentative electric log correlations. A major departure, however, occurs in the Magnolia's L. M. Morrison No. 1 of northwestern Val Verde County. This anomaly may reflect either large-scale thickening or the presence of additional section in this well. Zone I clay content is relatively homogeneous and correlatable variations are difficult to establish. Several wells in the Val Verde basin contain more than 5,000 feet of Zone I shale in which there is little variation in the clay content. A lower zone of relatively abundant chlorite, however, can be recognized in four wells. Chlorite is also more abundant in Zone I of the Val Verde basin than in Zone I of the Midland basin. Zone II is relatively uniform throughout the framework except in the Yates-Todd arch area. It is unidentifiable in two wells here. This absence reflects influence of the arch during Zone II deposition or is related to the geographic-oceanographic location of this area during Zone II time. Zone III is more variable both laterally and vertically. These variations could probably be correlated with more complete sampling. Abundant mixed-layer clay in this zone suggests slower deposition than that which occurred during Zone II time and (or) a different physical-chemical environment.