Karin A. Block

Transmission of Flood Basalts through a Shallow Crustal Sill and the Correlation of Sill Layers with Extrusive Flows: The Palisades Intrusive System and the Basalts of the Newark Basin, New Jersey, U.S.A.

The Palisades Intrusive System consists of a 350-m-thick early Jurassic sill together with thinner comagmatic sills and dikes exposed within the Newark Basin of New Jersey and New York. The Palisades System is overlain by flood basalt that is interbedded with early Jurassic redbed formations. New and recently published data indicate that some of the basalt flows correlate with geochemically defined layers within a central well-exposed sill portion of the Palisades System at Fort Lee, New Jersey. Our interpretation views the sill as a progressively inflated conduit through which huge volumes of flood basalt flowed. The geochemical data are consistent with a Palisades sill fed by three compositionally distinct intrusion events. The first magma flowed through the sill and broke out near the northern end as three Orange Mountain basalt flows. Each of the three extrusive pulses is identified within the lower 150 m of the sill on the basis of distinct geochemical reversals. The end stage of each pulse was characterized by pyroxene phenocryst accumulation within the sill. Magma from a second source inflated the sill by an additional 170 m after approximately 260 k.yr. of minor intermittent igneous activity interbedded with sediments deposited above the Orange Mountain basalt. The second magma extruded as a highly fractionated 150-m-thick Preakness basalt flow and crystallized as a central layer of Palisades diabase of similar composition. Subsequent extrusions of relatively thin Preakness flows (magma 3) correlate with upper layers of the Palisades sill. We interpret the distinct layering of the Palisades sill as injections of magmas that were largely prefractionated at deeper levels and then modified to varying degrees by in situ processes.

Spatial and vertical distribution of metals in sediment cores from Río Espíritu Santo estuary, Puerto Rico, United States

The concentration and distribution of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were investigated in three sediment cores representing 100-150years of accumulation in upriver, midriver, and estuarine environments in Río Espíritu Santo (RES), Puerto Rico. Grain-size distribution, organic matter and carbonate content were determined to assess their influence on metal concentrations. Minimum biotoxicity levels of Ni and Cu were exceeded in the upriver and midriver sites, while the minimum biotoxicity level of Cu was exceeded in the estuarine location. Pb concentration decreased by ~35% in the upper portion of the midriver and estuarine cores compared to downcore concentrations as a consequence of leaded gasoline regulation. Enrichment Factors and Geoaccumulation Indices were calculated for each metal revealing high levels of Cu in all three cores, likely from an igneous source. Our results provide a baseline for metal contamination in an area facing further land use change.

Influence of cations on aggregation rates in Mg-montmorillonite

Critical-zone reactions involve inorganic and biogenic colloids in a cation-rich environment. The present research defines the rates and structure of purified Mg-montmorillonite aggregates formed in the presence of monovalent (K+) and divalent (Ca2+, Mg 2+) cations using light-extinction measurements. Time evolution of turbidity was employed to determine early-stage aggregation rates. Turbidity spectra were used to measure the fractal dimension at later stages. The power law dependence of the stability ratios on cation concentration was found to vary with the reciprocal of the valence rather than the predicted reciprocal of valence-squared, indicating that the platelet structure may be a factor influencing aggregation rates. The critical coagulation concentrations (CCC) (3 mM for CaCl2, 4 mM for MgCl2, and 70 mM for KCl) were obtained from the stability ratios. At a later time and above a minimal cation concentration, turbidity reached a quasi-stable state, indicating the formation of large aggregates. Under this condition, an approximate turbidity forward-scattering correction factor was applied and the fractal dimension was determined from the extinction spectra. For the divalent cations, the fractal dimensions were 1.65 ± 0.3 for Ca2+ and 1.75 ± 0.3 for Mg2+ and independent of cation concentrations above the CCC. For the monovalent cation, the fractal dimension increased with K+ concentration from 1.35 to 1.95, indicating a transition to a face-to-face geometry from either an edge-to-edge or edge-to-face orientation.

Disassembly of the cystovirus ϕ6 envelope by montmorillonite clay

Prior studies of clay–virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species φ6 used in this study is a good model for enveloped pathogens. The interaction between φ6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT–φ6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge‐attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent‐produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT‐mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments.

Bacteria-clay interactions investigated by light scattering and phase contrast microscopy

Light scattering experiments and phase contrast microscopy are used to evaluate the aggregate-forming characteristics of simple clay-bacteria mixtures. Colloidal suspensions of negatively charged Pseudomonas syringae (Ps) and Mg2+-, Li+ - or Ca2+ -exchanged smectite (and non-exchanged smectite) are flocculated in neutral (pH 7) aqueous media. Aggregate formation is monitored using changes in optical transmission. Clustering is observed in all the clay-bacteria preparations. The Li+-substituted clay aggregates average 50-300 microns in diameter, in contrast to the Ca2+- substituted clay that produces aggregates of 10-50 microns in diameter. Light scattering measurements indicate that aggregates begin forming 3 hours after mixing and that the (larger sized) aggregates exhibit less scattering than a mixture with an equivalent concentration of unattached Ps and clay particles.

Composition and spatial distribution of elements and isotopes of a giant human bladder stone and environmental implications

The composition and spatial distribution of minerals, trace elements, as well as carbon and nitrogen isotopes from the outer crust to inner nucleus of a 20-year old giant human bladder stone comprising thirteen layers were intensively investigated. Calcium oxalate monohydrate (COM) was found to concentrate in the inner and middle layers, struvite was concentrated in middle and outer layers, and fluorapatite occurred in almost all layers. The spatial distribution of minerals has the potential to provide preliminary knowledge regarding the long-term urine composition, or even the physiological condition of the patient. The stable carbon isotope ratio (δ13C) and stable nitrogen isotope ratio (δ15N) were measured in each layer and significant correlation was found between δ13C with calcium oxalate monohydrate content and between δ15N and struvite content. Nearly constant values of -23.2‰ and 7.1‰ for δ13C and δ15N, respectively, were found in the organic components of the stone. Both isotope ratios indicate a long-term fixed diet consisting mainly of C3 plants, such as rice and wheat, for the 20-year time period of the stone formation. In addition, eighteen elements (Ca, P, Mg, K, Na, Al, Fe, Zn, Pb, Cu, Sr, Ba, Ti, V, Cr, Ni, Mn and Co) were measured in all the layers. The trace elements Al, Fe, Cu, Zn, Pb, Sr, Ba and Ti showed a similar spatial distribution pattern from the outer crust to the inner core. Although there were complex correlations between elements and minerals, Factor Analysis suggests that the occurrence of these elements in stones may be mainly the result of environmental exposure to metals during the formation of the stone, indicating that urinary stones may serve as potential long-term biomonitors. In particular, Ni and Cr showed a distinct distribution pattern in the stone, which may relate to human metabolic activities.

Heteroaggregation of an enveloped bacteriophage with colloidal sediments and effect on virus viability

Abstract Four sediments in the colloidal size range: goethite, montmorillonite, illite, and kaolinite, were suspended with the bacteriophage φ6, a model enveloped virus, to determine relative rates of heteroaggregation and the effect of aggregation on virus viability. Turbidity was measured on combinations of virus and each sediment type at low concentration to determine aggregation rates. Aggregation of sediment with virus occurred regardless of mineral type, and larger fraction of virus is expected to aggregate with increasing sediment concentration leading to higher deposition rates. The negatively charged sediments, aggregated with φ6 (also negatively charged at neutral pH) at a faster rate than the positively charged sediments, yielding turbidity slopes of 4.94 × 10−3 s−1 and 7.50 × 10−4 s−1 for φ6-montmorillonite and φ6-illite aggregates, respectively, and 2.98 × 10−5 s−1 and 2.84 × 10−5 s−1, for φ6-goethite and φ6-kaolinite, respectively. This indicates that the interaction between sediments and virus is hydrophobic, rather than electrostatic. Large numbers of virions remained viable post-aggregation, despite the fragility of the viral envelope, indicating that small-sized aggregates, which may travel more readily through porous media, may pose an infection risk. The fraction of φ6 that remained viable varied with sediment type, with montmorillonite-φ6 aggregates experiencing the greatest reduction in infectivity at 35%. TEM analyses reveal that in all sediment-φ6 combinations, infectivity loss was likely due to disassembly of the viral envelope as a result of aggregation.