Incidence of plastic fragments among burrow-nesting seabird colonies on offshore islands in northern New Zealand

Marine plastic pollution is ubiquitous throughout the world’s oceans, and has been found in high concentrations in oceanic gyres of both the northern and southern hemispheres. The number of studies demonstrating plastic debris at seabird colonies and plastic ingestion by adult seabirds has increased over the past few decades. Despite the recent discovery of a large aggregation of plastic debris in the South Pacific subtropical gyre, the incidence of plastics at seabird colonies in New Zealand is unknown. Between 2011 and 2012 we surveyed six offshore islands on the northeast coast of New Zealand’s North Island for burrow-nesting seabird colonies and the presence of plastic fragments. We found non-research related plastic fragments (0.031 pieces/m²) on one island only, Ohinau, within dense flesh-footed shearwater (Puffinus carneipes) colonies. On Ohinau, we found a linear relationship between burrow density and plastic density, with 3.5 times more breeding burrows in areas with plastic fragments found. From these data we conclude that plastic ingestion is a potentially a serious issue for flesh-footed shearwaters in New Zealand. Although these results do not rule out plastic ingestion by other species, they suggest the need for further research on the relationship between New Zealand’s pelagic seabirds and marine plastic pollution.     

Modeling of the 2011 Japan Tsunami: Lessons for Near-Field Forecast

During the devastating 11 March 2011 Japanese tsunami, data from two tsunami detectors were used to determine the tsunami source within 1.5 h of earthquake origin time. For the first time, multiple near-field tsunami measurements of the 2011 Japanese tsunami were used to demonstrate the accuracy of the National Oceanic and Atmospheric Administration (NOAA) real-time flooding forecast system in the far field. To test the accuracy of the same forecast system in the near field, a total of 11 numerical models with grids telescoped to 2 arcsec (~60 m) were developed to hindcast the propagation and coastal inundation of the 2011 Japanese tsunami along the entire east coastline of Japan. Using the NOAA tsunami source computed in near real-time, the model results of tsunami propagation are validated with tsunami time series measured at different water depths offshore and near shore along Japan’s coastline. The computed tsunami runup height and spatial distribution are highly consistent with post-tsunami survey data collected along the Japanese coastline. The computed inundation penetration also agrees well with survey data, giving a modeling accuracy of 85.5 % for the inundation areas along 800 km of coastline between Ibaraki Prefecture (north of Kashima) and Aomori Prefecture (south of Rokkasho). The inundation model results highlighted the variability of tsunami impact in response to different offshore bathymetry and flooded terrain. Comparison of tsunami sources inferred from different indirect methods shows the crucial importance of deep-ocean tsunami measurements for real-time tsunami forecasts. The agreement between model results and observations along Japan’s coastline demonstrate the ability and potential of NOAA’s methodology for real-time near-field tsunami flooding forecasts. An accurate tsunami flooding forecast within 30 min may now be possible using the NOAA forecast methodology with carefully placed tsunameters and large-scale high-resolution inundation models with powerful computing capabilities.     

The role of fire on soil mounds and surface roughness in the Mojave Desert

A fundamental question in arid land management centers on understanding the long‐term effects of fire on desert ecosystems. To assess the effects of fire on surface topography, soil roughness, and vegetation, we used terrestrial (ground‐based) LiDAR to quantify the differences between burned and unburned surfaces by creating a series of high‐resolution vegetation structure and bare‐earth surface models for six sample plots in the Grand Canyon‐Parashant National Monument, Arizona. We find that 11 years following prescribed burns, mound volumes, plant heights, and soil‐surface roughness were significantly lower on burned relative to unburned plots. Results also suggest a linkage between vegetation and soil mounds, either through accretion or erosion mechanisms such as wind and/or water erosion. The biogeomorphic implications of fire‐induced changes are significant. Reduced plant cover and altered soil surfaces from fire likely influence seed residence times, inhibit seed germination and plant establishment, and affect other ecohydrological processes. Published in 2012. This article is a US Government work and is in the public domain in the USA.     

Quantifying different riverbank erosion processes during an extreme flood event

Riverbank erosion is a major contributor to catchment sediment budgets. At large spatial scales data is often restricted to planform channel change, with little information on process distributions and their sediment contribution. This study demonstrates how multi‐temporal LiDAR and high resolution aerial imagery can be used to determine processes and volumes of riverbank erosion at a catchment scale. Remotely sensed data captured before and after an extreme flood event, enabled a digital elevation model of difference (DoD) to be constructed for the channel and floodplain. This meant that: the spatial area that could be assessed was extensive; three‐dimensional forms of bank failures could be mapped at a resolution that enabled process inference; and the volume and rates of different bank erosion processes over time could be assessed. A classification of riverbank mass failures, integrating form and process, identified a total of 437 mass failure polygons throughout the study area. These were interpreted as wet flow mass failures based on the presence of a well defined scarp wall and the absence of failed blocks on the failure floor. The failures appeared to be the result of: bank exfiltration, antecedent moisture conditions preceding the event, and the historic development of the channel. Using one‐dimensional hydraulic modelling to delineate geomorphic features within the main boundary of the macrochannel, an estimated 1 466 322 m² of erosion was interpreted as fluvial entrainment, occurring across catchment areas from 30 to 1668 km². Only 8% of the whole riverbank planform area was occupied by mass failures, whilst fluvial entrainment covered 33%. A third of the volume of material eroded came from mass failures, even though they occupied 19% of the eroded bank area. The availability of repeat LiDAR surveys, combined with high‐resolution aerial photography, was very effective in erosion process determination and quantification at a large spatial scale. Copyright © 2013 John Wiley & Sons, Ltd.     

Trends in the aggregated rate of pre-eruptive volcano-tectonic seismicity at Kilauea volcano, Hawaii

Accelerating rates of volcano-tectonic (VT) earthquakes are commonly observed during volcanic unrest. Understanding the repeatability of their behaviour is essential to evaluating their potential to forecast eruptions. Quantitative eruption forecasts have focused on changes in precursors over intervals of weeks or less. Previous studies at basaltic volcanoes in frequent eruption, such as Kilauea in Hawaii and Piton de La Fournaise on Réunion, suggest that VT earthquake rates tend to follow a power-law acceleration with time about 2 weeks before eruption, but that this trend is often obscured by random fluctuations (or noise) in VT earthquake rate. These previous studies used a stacking procedure, in which precursory sequences for several eruptions are combined to enhance the signal from an underlying acceleration in VT earthquake rate. Such analyses assume a common precursory trend for all eruptions. This assumption is tested here for the 57 eruptions and intrusions recorded at Kilauea between 1959 and 1984. Applying rigorous criteria for selecting data (e.g. maximum depth; restricting magnitudes to be greater than the completeness magnitude, 2.1), we find a much less pronounced increase in the aggregate rate of earthquakes than previously reported. The stacked trend is also strongly controlled by the behaviour of one particular pre-eruptive sequence. In contrast, a robust signal emerges among stacked VT earthquake rates for a subset of the eruptions and intrusions. The results are consistent with two different precursory styles at Kilauea: (1) a small proportion of eruptions and intrusions that are preceded by accelerating rates of VT earthquakes over intervals of weeks to months and (2) a much larger number of eruptions that show no consistent increase until a few hours beforehand. The results also confirm the importance of testing precursory trends against data that have been filtered according to simple constraints on the spatial distribution and completeness magnitude of the VT earthquakes.     

An Evaluation of Temporal Changes in Sediment Accumulation and Impacts on Carbon Burial in Mobile Bay,Alabama, USA

The estuarine environment can serve as either a source or sink of carbon relative to the coastal ocean carbon budget. A variety of time-dependent processes such as sedimentation, carbon supply, and productivity dictate how estuarine systems operate, and Mobile Bay is a system that has experienced both natural and anthropogenic perturbations that influenced depositional processes and carbon cycling. Sediments from eight box cores provide a record of change in bulk sediment accumulation and carbon burial over the past 110 years. Accumulation rates in the central part of the basin (0.09 g cm^?2) were 60–80 % less than those observed at the head (0.361 g cm^?2) and mouth (0.564 g cm^?2) of the bay. Sediment accumulation in the central bay decreased during the past 90 years in response to both anthropogenic (causeway construction) and natural (tropical cyclones) perturbations. Sediment accumulation inevitably increased the residence time of organic carbon in the oxic zone, as observed in modeled remineralization rates, and reduced the overall carbon burial. Such observations highlight the critical balance among sediment accumulation, carbon remineralization, and carbon burial in dynamic coastal environments. Time-series analysis based solely on short-term observation would not capture the long-term effects of changes in sedimentation on carbon cycling. Identifying these relationships over longer timescales (multi-annual to decadal) will provide a far better evaluation of coastal ocean carbon budgets.     

Dating Micrometre‐Thin Rims Using a LA‐ICP‐MS Depth Profiling Technique on Zircon from an Archaean Metasediment: Comparison with the SIMS Depth Profiling Method

Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was examined as a tool for measuring isotopic variation as a function of ablation depth in unpolished zircon from an Archaean metasediment specimen. This technique was able to identify micrometre‐thin (> 3 μm) isotopically distinct mineral domains characterised by ca. 100 Myr younger ²⁰⁷Pb/²⁰⁶Pb ages associated with 2s age uncertainties as low ~ 0.2%, as well as elevated U content relative to grain interiors (up to an order of magnitude). Our calculated drilling rate suggests that each laser pulse excavated depths of ~ 0.06 μm. Ages resolved through the LA‐ICP‐MS methods overlap the 2s uncertainties of ²⁰⁷Pb/²⁰⁶Pb ages measured using SIMS depth profiling on the same zircon population. The rims were further evinced by the detection of relative enrichment (> 3 orders of magnitude) in REE in the outermost micrometres of the same zircon, measured using a different and independent LA‐ICP‐MS depth profiling technique. We propose a LA‐ICP‐MS U–Pb technique capable of quickly identifying and quantifying rims, which are indication of late, yet geologically significant, fluid events that are otherwise undefined.     

Hydrochemical assessment of pond and stream water near abandoned barite mine sites in parts of Oban massif and Mamfe Embayment,Southeastern Nigeria

Hydrochemical studies were carried out in parts of Oban Massif and Mamfe Embayment, Southeastern Nigeria to examine the contributions of barite mining activities on water quality. Pond and stream water samples were collected from six abandoned barite mines and adjoining streams areas during dry and wet seasons. These samples were analysed for physicochemical parameters using standard techniques. The results showed that the quality of water samples in the vicinity of barite mine sites was characterized by low pH, low mineralization, high suspended solids and deep colour. Sodium (Na⁺) and calcium (Ca²⁺) are the dominant cations and bicarbonate (HCO₃ ^?) and sulphate (SO₄ ^2?) the dominant anions. The low concentration of dissolved silica, relatively high concentrations of Na⁺, HCO₃ ^? and SO₄ ^2? suggest a combined influence of silicate, carbonate and weathering of mine spoils. The total dissolved solids, total suspended solids, electrical conductivity and major ions (except Na⁺ and K⁺) are higher for water draining barite mines from Cretaceous sediments, while Na⁺, K⁺, Ba²⁺ are higher in basement rock areas. Correlation and factor analyses suggest that the main components of the water samples are related to anthropogenic, geogenic, mineralization and environmental controls, while Gibbs diagram plots indicate weathering as the main process controlling the chemistry of water. Computed values of hardness and some irrigational parameters showed that the pond and stream water samples are generally soft and can be used for irrigation. Generally, the water quality satisfied the WHO (2008) and NIS (2007) standards for domestic, agriculture and industrial. However, there is the need to assess the impact of the pollution on the ecosystem and human health while remediation measures are being considered.     

Paragenesis of cobalt and nickel in the Black Butte shale-hosted copper deposit,Belt Basin,Montana, USA

The Black Butte copper deposits (formerly known as Sheep Creek) are a group of sediment hosted, laterally extensive Cu–(Co–Ag) deposits hosted in dolomitic shale of the mid-Proterozoic Newland Formation. Copper–cobalt mineralization occurs in zones of massive, laminated pyrite that were locally reworked and infiltrated by Cu-rich fluids during early diagenesis. Cobalt, along with substantial nickel and arsenic, mainly occurs as impurities within early, porous pyrite, or as minute grains of sulpharsenides (i.e., cobaltite, glaucodot, and/or alloclasite). Later thermal events remobilized the Co, Ni, and As to form intergrowths of siegenite (Co,Ni)₃S₄ and tennantite. The temperature of this later event is constrained by the mineralogical assemblage to have been relatively low, between 125 and 225 °C. Although many of the characteristics of SEDEX-type deposits are present at Black Butte (e.g., laterally extensive massive pyrite horizons, interbedded black shales, abundant barite and local phosphate horizons, and rifted continental margin setting), the lack of economic Pb and Zn mineralization in the main deposits, and the abundance of Cu with high Co, is more typical of sediment-hosted stratiform copper deposits. The Neihart Formation, a hematitic quartz sandstone resting below the base of the Belt Supergroup, may have been an important source bed for Cu–Co–Ni–Ag fluids. It is speculated that these fluids, ideal for forming Cu deposits, were expelled along growth faults near the margin of the Belt Basin and deposited metals on or just below the sea floor in a setting that is typical of SEDEX deposits. This unique mineral deposit model may have applications to other districts where Cu–Co-rich sulfides are deposited in an exhalative setting.     

Finite Element Analyses and Experimental Investigation of Helical Micropiles

Within the framework of a research program on the behaviour of a specific type of screw micropile with helical plates of 220 mm diameter, the response in axial and horizontal loadings by the finite element method and full scale in situ tests were investigated. For the axial compressive or tensile loads, the simulation of the helical plates was carried out under axisymmetric conditions as shell foundations. The cases of purely cohesive or cohesionless soils with linear elastic–perfectly plastic behaviour were studied. The influence of shear strength parameters and the number of helical plates on the characteristic-ultimate resistance were also analyzed. For the horizontal loads 3D F.E. programs were applied for the analyses of the micropiles either as short or long ones. The in situ tests, which are presented in this article, were performed in two areas with representative subsoil conditions. The respective predictions from the F.E. method were based on results of geotechnical investigations and compared with the results of the in situ tests. A good approximation was ascertained, especially for uplift and horizontal loads and the differences were commented.