Petrology of the Permian Yellow Sands of northeastern England and their North Sea Basin equivalents

The Permian Yellow Sands of northeastern England and the Permian Weissliegendes of the English North Sea Basin are petrologically defined as multicycle, moderately sorted, subrounded graywackes, subgraywackes and subarkoses with post-depositionally etched and overgrown grains. These sandstones were derived by the marine reworking of the Permian Rotliegendes and transported from the east to the southwest. Petrologic data show that these Upper Permian sandstones were deposited in a shallow marine environment and that the commonly held aeolian dune interpretation for them should be rejected. Their formation during the transgression of the Zechstein Sea places them within the Zechstein sequence and therefore they are Thuringian in age rather than Saxonian.     

Cyprus umbers: Chemical precipitates on a Tethyan ocean ridge

Iron-rich mudstones (umbers), directly overlying pillow lavas of the Troodos Massif, Cyprus, are interpreted as precipitates connected with late stages of volcanism on a Cretaceous ocean ridge. Chemical composition of the basal sediments allies them with the basal iron-rich sediments of the East Pacific Rise. Overlying radiolarites and chalks are more comparable to normal pelagic sediments. Sedimentary features and stratigraphic relations suggest rapid deposition of umbers, relative to the overlying sediments.     

Laboratory Kinetic Studies of the Reactions of Cl Atoms with Species of Biogenic Origin: δ3-Carene, Isoprene, Methacrolein and Methyl Vinyl Ketone

The rate coefficients for the reaction between atomic chlorine and a number of naturally occurring species have been measured at ambient temperature and atmospheric pressure using the relative rate technique. The values obtained were (4.0 ± 0.8) × 10^-10, (2.1 ± 0.5) × 10^-10, (3.2 ± 0.5) × 10^-10, and (4.9 ± 0.5) × 10^-10 cm³ molecule^-1 s^-1, for reactions with isoprene, methyl vinyl ketone, methacrolein and ³-carene, respectively. The value obtained for isoprene compares favourably with previously reported values. No values have been reported to date for the rate constants of the other reactions.     

Attenuation of nitrate in aquitard sediments of southern Ontario

To examine nitrate persistence, detailed geochemical profiling, using core-squeezed water and piezometer samples, was carried out at five sites in southern Ontario where groundwater is moving downward in silt-rich aquitard sediments at rates of 16 to more than 20 cm year⁻¹. Elevated levels of NO₃⁻-N (5–50 mg 1⁻¹) that occur in the shallow groundwater as a result of agricultural activity, were found to be consistently attenuated, generally to very low levels (< 0.05 mg 1⁻¹-N), at the ‘redoxcline’, the horizon marking the boundary between the surficial weathered (brown) sediments and the underlying unweathered (grey) sediments. Tritium dating suggests that groundwater at the redoxcline depths (3–5 m) was recharged between 1970 and 1980, thus the N03 depletion appears to result from biodegradation reactions since no major landuse changes have occurred during this period. The close association of the nitrate depletion zones with the redoxcline, where, in particular, sediment sulphur contents increase abruptly, and where also porewater SO₄²⁻ levels increase, suggests that the dominant attenuation reaction is autotrophic denitrification using reduced sulphur compounds present in the unweathered sediment as the electron donor. Mass balance calculations suggest that the increase in the downward rate of migration of the redoxcline, owing to added sulphur consumption from NO₃⁻ contamination, is only about 1 mm year⁻¹ at these sites. Review of the literature indicates that most silt- and clay-rich sediments have S contents in the same range, or higher, than those investigated here, thus, in most cases where aquifers are overlain by several metres or more of unweathered confining sediments, it is likely that a high degree of protection is afforded from surficial NO₃⁻ contamination.     

Sulfide oxidation and distribution of metals near abandoned copper mines in coastal environments,Prince William Sound,Alaska, USA

The oxidation of sulfide-rich rocks, mostly leftover debris from Cu mining in the early 20th century, is contributing to metal contamination of local coastal environments in Prince William Sound, Alaska. Analyses of sulfide, water, sediment, precipitate and biological samples from the Beatson, Ellamar, and Threeman mine sites show that acidic surface waters generated from sulfide weathering are pathways for redistribution of environmentally important elements into and beyond the intertidal zone at each site. Volcanogenic massive sulfide deposits composed of pyrrhotite and (or) pyrite + chalcopyrite + sphalerite with subordinate galena, arsenopyrite, and cobaltite represent potent sources of Cu, Zn, Pb, As, Co, Cd, and Hg. The resistance to oxidation among the major sulfides increases in the order pyrrhotite ? sphalerite < chalcopyrite ? pyrite; thus, pyrrhotite-rich rocks are typically more oxidized than those dominated by pyrite. The pervasive alteration of pyrrhotite begins with rim replacement by marcasite followed by replacement of the core by sulfur, Fe sulfate, and Fe–Al sulfate. The oxi dation of chalcopyrite and pyrite involves an encroachment by colloform Fe oxyhydroxides at grain margins and along crosscutting cracks that gradually consumes the entire grain. The complete oxidation of sulfide-rich samples results in a porous aggregate of goethite, lepidocrocite and amorphous Fe-oxyhydroxide enclosing hydrothermal and sedimentary silicates. An inverse correlation between pH and metal concentrations is evident in water data from all three sites. Among all waters sampled, pore waters from Ellamar beach gravels have the lowest pH (∼3) and highest concentrations of base metals (to ∼25,000 μg/L), which result from oxidation of abundant sulfide-rich debris in the sediment. High levels of dissolved Hg (to 4100 ng/L) in the pore waters probably result from oxidation of sphalerite-rich rocks. The low-pH and high concentrations of dissolved Fe, Al, and SO₄ are conducive to precipitation of interstitial jarosite in the intertidal gravels. Although pore waters from the intertidal zone at the Threeman mine site have circumneutral pH values, small amounts of dissolved Fe²⁺ in the pore waters are oxidized during mixing with seawater, resulting in precipitation of Fe-oxyhydroxide flocs along the beach–seawater interface. At the Beatson site, surface waters funneled through the underground mine workings and discharged across the waste dumps have near-neutral pH (6.7–7.3) and a relatively small base-metal load; however, these streams probably play a role in the physical transport of metalliferous particulates into intertidal and offshore areas during storm events. Somewhat more acidic fluids, to pH 5.3, occur in stagnant seeps and small streams emerging from the Beatson waste dumps. Amorphous Fe precipitates in stagnant waters at Beatson have high Cu (5.2 wt%) and Zn (2.3 wt%) concentrations that probably reflect adsorption onto the extremely high surface area of colloidal particles. Conversely, crystalline precipitates composed of ferrihydrite and schwertmannite that formed in the active flow of small streams have lower metal contents, which are attributed to their smaller surface area and, therefore, fewer reactive sorption sites. Seeps containing precipitates with high metal contents may contribute contaminants to the marine environment during storm-induced periods of high runoff. Preliminary chemical data for mussels (Mytilus edulis) collected from Beatson, Ellamar, and Threeman indicate that bioaccumulation of base metals is occurring in the marine environment at all three sites.     

Development of a biocidal treatment regime to inhibit biological growths on cultural heritage: BIODAM

Existing chemical treatments to prevent biological damage to monuments often involve considerable amounts of potentially dangerous and even poisonous biocides. The scientific approach described in this paper aims at a drastic reduction in the concentration of biocide applications by a polyphasic approach of biocides combined with cell permeabilisers, polysaccharide and pigment inhibitors and a photodynamic treatment. A variety of potential agents were screened to determine the most effective combination. Promising compounds were tested under laboratory conditions with cultures of rock deteriorating bacteria, algae, cyanobacteria and fungi. A subsequent field trial involved two sandstone types with natural biofilms. These were treated with multiple combinations of chemicals and exposed to three different climatic conditions. Although treatments proved successful in the laboratory, field trials were inconclusive and further testing will be required to determine the most effective treatment regime. While the most effective combination of chemicals and their application methodology is still being optimised, results to date indicate that this is a promising and effective treatment for the control of a wide variety of potentially damaging organisms colonising stone substrates.     

Erosion and Flooding—Threats to Coastal Infrastructure in the Arctic: A Case Study from Herschel Island,Yukon Territory,Canada

Arctic coastal infrastructure and cultural and archeological sites are increasingly vulnerable to erosion and flooding due to amplified warming of the Arctic, sea level rise, lengthening of open water periods, and a predicted increase in frequency of major storms. Mitigating these hazards necessitates decision-making tools at an appropriate scale. The objectives of this paper are to provide such a tool by assessing potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site. This study focused on Simpson Point and the adjacent coastal sections because of their archeological, historical, and cultural significance. Shoreline movement was analyzed using the Digital Shoreline Analysis System (DSAS) after digitizing shorelines from 1952, 1970, 2000, and 2011. For purposes of this analysis, the coast was divided in seven coastal reaches (CRs) reflecting different morphologies and/or exposures. Using linear regression rates obtained from these data, projections of shoreline position were made for 20 and 50 years into the future. Flood hazard was assessed using a least cost path analysis based on a high-resolution light detection and ranging (LiDAR) dataset and current Intergovernmental Panel on Climate Change sea level estimates. Widespread erosion characterizes the study area. The rate of shoreline movement in different periods of the study ranges from ?5.5 to 2.7 m·a^?1 (mean ?0.6 m·a^?1). Mean coastal retreat decreased from ?0.6 m·a^?1 to ?0.5 m·a^?1, for 1952–1970 and 1970–2000, respectively, and increased to ?1.3 m·a^?1 in the period 2000–2011. Ice-rich coastal sections most exposed to wave attack exhibited the highest rates of coastal retreat. The geohazard map combines shoreline projections and flood hazard analyses to show that most of the spit area has extreme or very high flood hazard potential, and some buildings are vulnerable to coastal erosion. This study demonstrates that transgressive forcing may provide ample sediment for the expansion of depositional landforms, while growing more susceptible to overwash and flooding.     

Sediment Nitrogen Fixation: a Call for Re-evaluating Coastal N Budgets

Coastal ocean primary productivity is often limited by nitrogen (N) availability, which is determined by the balance between N sources (e.g., N-fixation, groundwater, river inputs, etc.) and sinks (e.g., denitrification, sediment burial, etc.). Historically, heterotrophic N-fixation in sediments was excluded as a significant source of N in estuarine budgets, based on low, indirectly measured rates (e.g., acetylene reduction assay) and because it was unnecessary to achieve mass balance. Many recent studies using net N₂ flux measurements have shown that sediment N-fixation can equal or exceed N₂ loss. In an effort to quantify N₂ production and consumption simultaneously, we measured N-fixation and denitrification directly in sediment cores from a temperate estuary (Waquoit Bay, MA). N-fixation, dissimilatory nitrate reduction to ammonium, and denitrification occurred simultaneously, and the net N₂ flux shifted from uptake (N-fixation) to efflux (denitrification) over the 120-h incubation. Evidence for N-fixation included net ²⁸N₂ and ³⁰N₂ uptake, ¹⁵NH₄ ⁺ production from ³⁰N₂ additions, ¹⁵N_{organic matter} production, and nifH expression. N-fixation from ³⁰N₂ was up to eight times higher than potential denitrification. However, N-fixation calculated from ¹⁵NO₃ ^? was one half of the measured fixation from ³⁰N₂, indicating that ¹⁵NO₃-isotope labeling calculations may underestimate N-fixation. These results highlight the dynamic nature of sediment N cycling and suggest that quantifying individual processes allows a greater understanding of what net N₂ fluxes signify and how that balance varies over time.