Salt Marsh and Fringing Oyster Reef Transgression in a Shallow Temperate Estuary: Implications for Restoration,Conservation and Blue Carbon

The importance of intertidal estuarine habitats, like salt marsh and oyster reef, has been well established, as has their ubiquitous loss along our coasts with resultant forfeiture of the ecosystem services they provide. Furthering our understanding of how these habitats are evolving in the face of anthropogenic and climate driven changes will help improve management strategies. Previous work has shown that the growth and productivity of both oyster reefs and salt marshes are strongly linked to elevation in the intertidal zone (duration of aerial exposure). We build on that research by examining the growth of marsh-fringing oyster reefs at yearly to decadal time scales and examine movement of the boundary between oyster reef and salt marsh at decadal to centennial time scales. We show that the growth of marsh-fringing reefs is strongly associated to the duration of aerial exposure, with little growth occurring below mean low water and above mean sea level. Marsh-shoreline movement, in the presence or absence of fringing oyster reefs, was reconstructed using transects of sediment cores. Carbonaceous marsh sediments sampled below the modern fringing oyster reefs indicate that marsh shorelines within Back Sound, North Carolina are predominantly in a state of transgression (landward retreat), and modern oyster-reef locations were previously occupied by salt marsh within the past two centuries. Cores fronting transgressive marsh shorelines absent fringing reefs sampled thinner and less extensive carbonaceous marsh sediment than at sites with fringing reefs. This indicates that fringing reefs are preserving carbonaceous marsh sediment from total erosion as they transgress and colonize the exposed marsh shoreline making marsh sediments more resistant to erosion. The amount of marsh sediment preservation underneath the reef scales with the reef’s relief, as reefs with the greatest relief were level with the marsh platform, preserving a maximum amount of carbonaceous sediments during transgression by buffering the marsh from erosional processes. Thus, fringing oyster reefs not only have the capacity to shelter shorelines but, if located at the ideal tidal elevation, they also keep up with accelerating sea-level rise and cap carbonaceous sediments, protecting them from erosion, as reefs develop along the marsh.     

Uptake of hazardous elements by spring onion (<Emphasis Type="Italic">Allium fistulosum</Emphasis> L.) from soil irrigated with different types of water and possible health risk

Bio-concentration of elements such as Mo, As, Se, Fe, Cu, Zn, Ni and Pb was analyzed in spring onion (Allium fistulosum L.) in three different locations of central Punjab, Pakistan. At location GW, relatively low level of hazardous elements was found in spring onion, suggesting that groundwater is a safe source of water for irrigating food crops. The pH of soil at wastewater irrigation was found less acidic (pH 7.4) than the other sites. The range of concentration in the different samples of spring onion was as follows: 6.15–8.16 mg kg^?1 for Mo, 2.77–4.28 mg kg^?1 for As, 0.395–0.705 mg kg^?1 for Se, 36.73–48.17 mg kg^?1 for Fe, 10.58–16.26 mg kg^?1 for Cu, 28.87–39.79 mg kg^?1 for Zn, 6.66–8.75 mg kg^?1 for Ni and 4.33–6.09 mg kg^?1 for Pb, respectively. High bio-concentration of Zn (15.37) from soil to spring onion was found at canal water irrigated location. The estimated daily intake of metal for spring onion was less, but the health risk index was higher than 1 for Mo, As, Cu, Pb and Ni, respectively. This was due to higher proportion of spring onion in diet, which consequently increased the health risk index for metals. Therefore, it is recommended to avoid growing vegetables in untreated urban and rural wastewater containing elevated amounts of metals.     

Polarization models of young stellar objects – II. Linear and circular polarimetry of R Coronae Australis

Near-infrared linear imaging polarimetry of the young stellar objects R CrA and T CrA in the J , H and K n bands, and circular imaging polarimetry in the H band, is presented. The data are modelled with the Clark and McCall scattering model. The R CrA and T CrA system is shown to be a particularly complex scattering environment. In the case of R CrA there is evidence that the wavelength dependence of polarization changes across the nebula. MRN dust grain models do not explain this behaviour. Depolarization by line emission is considered as an alternative explanation. The dust grain properties could also be changing across the nebula.
Although surrounded by reflection nebulosity, there is a region of particularly low polarization surrounding R CrA that is best modelled by the canonical bipolar outflow being truncated by an evacuated spherical cavity surrounding the star. The symmetry axis of the nebula appears inclined by 50° to the plane of the sky.
The H -band circular polarimetry of R CrA clearly shows a quadrupolar structure of positive and negative degrees of circular polarization that reach peak magnitudes of ∼5 per cent within our limited map. It is shown that spherical MRN grains are incapable of producing this circular polarization given the observed linear polarization of the R CrA system. Instead, scattering from aligned non-spherical grains is proposed as the operating mechanism.
T CrA is a more archetypical bipolar reflection nebula, and this object is modelled as a canonical parabolic reflection nebula that lies in the plane of the sky. The wavelength independence of linear polarization in the T CrA reflection nebula suggests that the scattering particles are Rayleigh sized. This is modelled with the MRN interstellar grain size distribution.     

Non-invasive Geophysical Surveys in Search of the Roman Temple of Augustus Under the Cathedral of Tarragona (Catalonia,Spain): A Case Study

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious veneration. Finally, both ERT and GPR have been conducted during a week of intensive overnight surveys that provided detailed information on subsurface existing structures. The ERT method has been applied using different techniques and arrays, ranging from standard Wenner–Schlumberger 2D sections to full 3D electrical imaging with the advanced Maximum Yield Grid array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity data to obtain a complete 3D image after a full inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists. GPR results provided additional information about shallowest structures. The geophysical results were clear enough to persuade religious authorities and archaeologists to conduct selected excavations in the most promising areas that confirmed the interpretation of geophysical data. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province.     

Flood hazard mapping in Southern Brazil: a combination of flow frequency analysis and the HAND model

The Itajaí River basin is one of the areas most affected by flood-related disasters in Brazil. Flood hazard maps based on digital elevation models (DEM) are an important alternative in the absence of detailed hydrological data and for application in large areas. We developed a flood hazard mapping methodology by combining flow frequency analysis with the Height Above the Nearest Drainage (HAND) model – f2HAND – and applied it in three municipalities in the Itajaí River basin. The f2HAND performance was evaluated through comparison with observed 2011 flood extent maps. Model performance and sensitivity were tested for different DEM resolutions, return periods and streamflow data from stations located upstream and downstream on the main river. The flood hazard mapping with our combined approach matched 92% of the 2011 flood event. We found that the f2HAND model has low sensitivity to DEM resolution and high sensitivity to area threshold of channel initiation.     

Characterisation of ground motion recording stations in the Groningen gas field

The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity (V_S). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ V_S values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging. The offset SCPT, cross-hole tomography and common midpoint cross-correlation (CMPcc) processing of MASW data all revealed lateral variations on length scales of several to tens of metres in this geological setting. SCPTs resulted in very detailed V_S profiles with depth, but represent point measurements in a heterogeneous environment. The MASW results represent V_S information on a larger spatial scale and smooth some of the heterogeneity encountered at the sites. The combination of MASW and SCPT proved to be a powerful and cost-effective approach in determining representative V_S profiles at the accelerograph station sites. The measured V_S profiles correspond well with the modelled profiles and they significantly enhance the ground motion model derivation. The similarity between the theoretical transfer function from the V_S profile and the observed amplification from vertical array stations is also excellent.     

Time lapse structure‐from‐motion photogrammetry for continuous geomorphic monitoring

Recent advances are made in earth surface reconstruction with high spatial resolution due to SfM photogrammetry. High flexibility of data acquisition and high potential of process automation allows for a significant increase of the temporal resolution, as well, which is especially interesting to assess geomorphic changes. Two case studies are presented where 4D reconstruction is performed to study soil surface changes at 15 seconds intervals: (a) a thunderstorm event is captured at field scale and (b) a rainfall simulation is observed at plot scale. A workflow is introduced for automatic data acquisition and processing including the following approach: data collection, camera calibration and subsequent image correction, template matching to automatically identify ground control points in each image to account for camera movements, 3D reconstruction of each acquisition interval, and finally applying temporal filtering to the resulting surface change models to correct random noise and to increase the reliability of the measurement of signals of change with low intensity. Results reveal surface change detection with cm‐ to mm‐accuracy. Significant soil changes are measured during the events. Ripple and pool sequences become obvious in both case studies. Additionally, roughness changes and hydrostatic effects are apparent along the temporal domain at the plot scale. 4D monitoring with time‐lapse SfM photogrammetry enables new insights into geomorphic processes due to a significant increase of temporal resolution. Copyright © 2017 John Wiley & Sons, Ltd.     

Comparison between the indirect approach and kriging with samples of different support for estimation using samples of different length

In this paper we compare two estimation methods to deal with samples of different support: (1) the indirect approach using accumulation and (2) kriging with samples of different support. These two methods were tested in a simple example. The estimates of the two methods were compared against a benchmark scenario. The benchmark consisted of kriging using a complete set of samples on the same support. The effects of the nugget effect, variogram range and type on the weight of long samples, the estimate, and the error variance were assessed. Kriging with samples of different support led to lower error variance and to estimates closer to the estimates of the benchmark scenario. Furthermore, in the case of spatially continuous attributes (low nugget effect), the indirect approach assigns greater weight to long samples than kriging with samples of different support. A cross validation study comparing the two methods with a database from a bauxite deposit was performed. The results of the cross validation study showed that kriging with samples of different support resulted in more precise estimates.