On‐Site Vapor‐Phase Analysis as a Novel Approach for Monitoring Groundwater Wells

The results of comprehensive field testing of on‐site vapor‐phase‐based groundwater monitoring methods are presented to demonstrate their utility as a robust and cost‐effective approach for rapidly obtaining volatile organic compounds (VOCs) concentration data from a monitoring well. These methods—which rely on sensitive, commercially available field equipment to analyze vapor in equilibrium with groundwater—proved easy to implement and can be tailored to site‐specific needs, including multilevel sampling. During field testing, low‐flow groundwater concentrations could be reasonably estimated using submerged passive vapor diffusion samplers or field equilibration of collected groundwater (R² = 0.85 to 0.96). These two methods are not as reliant on in‐well mixing to overcome vertical stratification within wells as simpler headspace methods. The importance of well and aquifer‐specific factors on concentration data (and therefore method selection) is highlighted, including the effect of changing in‐well patterns due to seasonal temperature gradients. Results indicated that vertical stratification was relatively limited within the set of wells included in these studies, resulting in similar performance for short depth‐discrete passive vapor diffusion samplers (constructed from 40‐mL vials) and longer samplers (2.5 to 5 feet in length) designed to cover a larger portion of the screened interval. A year‐long, multi‐event evaluation demonstrated that vapor‐phase‐based monitoring methods are no more variable than conventional groundwater monitoring methods, with both types subject to similar spatial and temporal variability that can be difficult to reduce. Vapor sampling methods represent a promising approach for estimation of groundwater concentrations by reducing the cost liabilities associated with monitoring while providing a more sustainable approach.     

大型洞穴崩塌大厅

中国和马来西亚Sarawak的Mulu喀斯特区发育的大型洞穴厅堂和天坑都与小洞道有关.它们主要沿破碎带发育,有些沿潜流带发育,其岩块崩塌并非仅与渗流排水有关.     

Tertiary Tsondab Sandstone Formation: preliminary bedform reconstruction and comparison to modern Namib Sand Sea dunes

The Tertiary Tsondab Sandstone Formation, which underlies much of the present Namib Sand Sea, is a key element in understanding the Cenozoic evolution of the Namib Desert. Outcrops of the aeolian facies of the Tsondab Sandstone at Elim and Diep Rivier consist of two sequences of bioturbated cross-strata separated by likely formation-scale surfaces of stabilisation. Cross-strata consist of scalloped sets about 200 m in width and separated by southeast dipping bounding surfaces. Internally, sets contain reactivation surfaces of probable seasonal origin. The north to south-southeast dipping foresets define crescent shapes with a trough axis trending northeast. Although additional data are needed to define the Tsondab bedform, the outcrop data is best satisfied in computer simulations by north trending, east migrating main bedforms, which had relatively large and slow-moving dunes superimposed upon their eastern flanks and migrated to the north. Foresets dipping to the south to south-southwest at Elim suggest that superimposed dunes also occurred on the western flanks of the main bedform and migrated to the south, but that their record was largely lost with net eastward migration of the main bedform. This preliminary Tsondab model shares attributes such as trend, scale of cross-strata, and presence of scalloped sets with reactivation surfaces with computer models of the modern linear dunes in which large-scale sinuosity migrates alongcrest to the north. Differences emerge in the overall set architecture and the orientation of cross-strata and bounding surfaces, as well as the degree of vegetation that must have characterised Tsondab dunes.     

A geomorphological mapping approach for the assessment of seabed geohazards and risk

Exploration and development of offshore hydrocarbon resources has advanced into remote deepwater regions over the last decade and poses significant technical challenges for the design and installation of wells and facilities at extreme water depths. Seafloor and shallow subsurface processes and conditions in these areas are complex and generally poorly understood, and the geohazards to development are larger scale and fundamentally different to those encountered onshore; consequently the geohazard risk to deepwater development projects is potentially significant and requires careful evaluation and mitigation during the front-end planning and engineering design stages of projects. There are no established industry standards or methods for the assessment of geohazards and engineering-quality geophysical data at the scale of development. The paper describes an integrated and systematic map-based approach for the assessment and mitigation of seabed geohazards and risk to proposed deepwater development. The approach employs a multi-disciplinary team working with engineering-quality field calibrated data to accurately map and assess seafloor ground conditions and ensure that development proposals are not exposed to intolerable geohazard risk. The approach taken is very similar to the practice of establishing geological models for land-based engineering projects, in which the complete geological history of the site is used to characterise and predict the performance of the ground. Such an approach is routine for major projects on land but so far does not seem to be common practice in the offshore industry. The paper illustrates the seafloor geomophological mapping approach developed. The products are being used to optimise development layouts to avoid geohazards where possible and to support site-specific engineering design of facilities based on a detailed understanding of the potential geohazard loadings and associated risk.     

The genus Pseudo-nitzschia (Bacillariophyceae) in New Zealand: analysis of the last decade's monitoring data

The diatom genus Pseudo-nitzschia blooms throughout New Zealand's coastal waters. More than a decade of monitoring data were analysed in this study and seasonality was a significant factor in the appearance of Pseudo-nitzschia blooms. Austral spring and summer were the main bloom periods, although there were regional differences. Between January 2000 and August 2011, 8.4% of 29,000 seawater samples analysed for Pseudo-nitzschia exceeded the voluntary trigger level for biotoxin testing (10×10⁴ cells l^?1), and these were analysed by fluorescent in situ hybridisation (FISH) assays. Pseudo-nitzschia fraudulenta and P. pseudodelicatissima (low domoic acid [DA] producers) were the dominant bloom formers throughout New Zealand (each contributing 25%) followed by the highly toxic P. australis (10%). Shellfish flesh testing for DA was triggered on 8477 occasions between 2000 and 2011, but no samples exceeded the regulatory limit (20 mg/kg); the maximum concentration was 13 mg/kg (Marlborough Sounds, mid-winter 2010).     

Use of a shared tuned mass damper (STMD) to reduce vibration and pounding in adjacent structures

The dynamic response of tall civil structures due to earthquakes is very important to civil engineers. Structures exposed to earthquakes experience vibrations that are detrimental to their structural components. Structural pounding is an additional problem that occurs when buildings experience earthquake excitation. This phenomena occurs when adjacent structures collide from their out‐of‐phase vibrations. Many energy dissipation devices are presently being used to reduce the system response. Tuned mass dampers (TMD) are commonly used to improve the response of structures. The stiffness and damping properties of the TMD are designed to be a function of the natural frequency of the building to which it is connected. This research involves attaching adjacent structures with a shared tuned mass damper (STMD) to reduce both the structures vibration and probability of pounding. Because the STMD is connected to both buildings, the problem of tuning the STMD stiffness and damping parameters becomes an issue. A design procedure utilizing a performance function is used to obtain the STMD parameters to result in the best overall system response. Copyright © 2001 John Wiley & Sons, Ltd.     

Reconstructing the IRAS Point Source Catalog Redshift Survey with a generalized PIZA

We study the influence of different magnetic boundary conditions on the generation of magnetic fields by turbulent convection. It is found that the structure and strength of the generated field in the vicinity of the boundary is strongly dependent on the choice of boundary conditions. In the convective interior, however, the solutions remain largely insensitive to the boundary conditions. In all cases the overall efficiency of the dynamo process remains high with a steady state magnetic energy density between 12 and 25 per cent of the turbulent kinetic energy, and peak field values exceeding the equipartition level. These results support the idea that the solar granulation may constitute a dynamo source for magnetic fields in the quiet photosphere.     

Setting new thermal standards for transitional and coastal (TraC) waters

The construction of a new generation of coastal power stations in the UK and other western European countries has highlighted the absence of robust standards for thermal discharges to transitional and coastal waters. The proposed discharge volumes are greater than hitherto, yet there has been little independent critical examination of their potential impact, whilst much of the existing guidance has been adapted from freshwater practice. This review considers the available knowledge on the tolerance and behaviour of fish and other marine biota to heated effluents. Appropriate ways are suggested of grouping fish species to reflect their sensitivity to thermal effects. The plethora of existing standards are considered and their validity assessed in a framework of predicted seawater temperature rise. Those species or groups of organisms most likely to be affected are identified and finally specific recommendations for thermal standards consistent with long term sustainability are proposed.