Potential microbial bioinvasions via ships' ballast water, sediment, and biofilm

A prominent vector of aquatic invasive species to coastal regions is the discharge of water, sediments, and biofilm from ships' ballast-water tanks. During eight years of studying ships arriving to the lower Chesapeake Bay, we developed an understanding of the mechanisms by which invasive microorganisms might arrive to the region via ships. Within a given ship, habitats included ballast water, unpumpable water and sediment (collectively known as residuals), and biofilms formed on internal surfaces of ballast-water tanks. We sampled 69 vessels arriving from foreign and domestic ports, largely from Western Europe, the Mediterranean region, and the US East and Gulf coasts. All habitats contained bacteria and viruses. By extrapolating the measured concentration of a microbial metric to the estimated volume of ballast water, biofilm, or residual sediment and water within an average vessel, we calculated the potential total number of microorganisms contained by each habitat, thus creating a hierarchy of risk of delivery. The estimated concentration of microorganisms was greatest in ballast water>sediment and water residuals>biofilms. From these results, it is clear microorganisms may be transported within ships in a variety of ways. Using temperature tolerance as a measure of survivability and the temperature difference between ballast-water samples and the water into which the ballast water was discharged, we estimated 56% of microorganisms could survive in the lower Bay. Extrapolated delivery and survival of microorganisms to the Port of Hampton Roads in lower Chesapeake Bay shows on the order of 10(20) microorganisms (6.8 x 10(19) viruses and 3.9 x 10(18) bacteria cells) are discharged annually to the region.     

Drivers of interannual and intra‐annual variability of dissolved organic carbon concentration in the River Thames between 1884 and 2013

The world's longest record of river water quality (River Thames—130 years) provides a unique opportunity to understand fluvial dissolved organic carbon (DOC) concentrations dynamics. Understanding riverine DOC variability through long‐term studies is crucial to capture patterns and drivers influencing sources of DOC at scales relevant for decision making. The Thames basin (United Kingdom) has undergone massive land‐use change, as well as increased urbanisation and population during the period considered. We aimed to investigate the drivers of intra‐annual to interannual DOC variability, assess the variability due to natural and anthropogenic factors, and understand the causes for the increased DOC variability over the period. Two approaches were used to achieve these aims. The first method was singular spectrum analysis, which was used to reconstruct the major oscillatory modes of DOC, hydroclimatic variables, and atmospheric circulation patterns and to visualise the interaction between these variables. The second approach used was generalised additive modelling, which was used to investigate other non‐natural drivers of DOC variability. Our study shows that DOC variability increased by 80% over the data period, with the greatest increase occurring from the beginning of World War II onwards. The primary driver of the increase in DOC variability was the increase in the average value of fluvial DOC over the period of record, which was itself linked to the increase in basin population and diffuse DOC sources to the river due to land‐use and land‐management changes. Seasonal DOC variability was linked to streamflow and temperature. Our study allows to identify drivers of fluvial intra‐annual and interannual DOC variability and therefore empowers actions to reduce high DOC concentrations.     

Shaking table 2‐D models of a concrete gravity dam

One of the most famous and studied cases of dams subjected to earthquake loading is the Koyna Dam in India. In this study, a two‐dimensional model of Koyna Dam at 1/50 scale was used on a shake table to simulate effects and serve as data for non‐linear computer model calibration. A new concrete mix was designed for the non‐linear similitude modelling. This new mix provided the correct kinematic failure of concrete at scale. Two models were tested to failure: one with an initial shrinkage crack and one monolith. Reservoir effects were not modelled. The results of both models are discussed and compared. The ability to model non‐linear effects is discussed. Published in 2000 by John Wiley & Sons, Ltd.     

Seismic design methodology for friction damped braced frames

This paper is concerned with the design of steel frames using friction damped slotted bolted connections (SBCs) in the diagonal braces. A dynamic model is developed to describe the behaviour of a single‐degree‐of‐freedom (SDOF) steel frame that uses bilinear hysteretic behaviour for the damper. This model is generalized to MDOF systems. A novel algorithm for displacement reversal in the transition from slip to stick is presented. It uses numerical noise for its success. A design procedure that attains the stiffness of the individual braces and their elongation at the threshold of activation is then applied to a 10‐storey steel frame. This design process is a two‐phase iterative procedure that converges quite fast. Copyright © 2000 John Wiley & Sons, Ltd.     

Century-scale nitrogen and phosphorus controls of the carbon cycle

In recent decades, humans have become a very important force in the Earth system, demonstrating that emissions (gaseous, liquid, and solid) are the cause of many of our environmental issues. These emissions are responsible for major global reorganizations of the biogeochemical cycles. The oceans are now a net sink of atmospheric CO₂, whereas in their preindustrial state they were a source; the trophic state of the coastal oceans is progressively moving toward increased heterotrophy; and the terrestrial realm is now vacillating between trophic states, whereas in preindustrial times it was autotrophic. In this paper, we present model calculations that underscore the role of human-induced perturbations in changing Earth's climate, specifically the role of anthropogenic nitrogen and phosphorus in controlling processes in the global carbon cycle since the year 1850 with projections to the year 2035. Our studies show that since the late 1940's emissions of nitrogen and phosphorus have been sequestered in the terrestrial living phytomass and groundwater. This nutrient-enhanced fertilization of terrestrial biota, coupled with rising atmospheric CO₂ and global temperature, has induced a sink of anthropogenic CO₂ that roughly balances the emission of CO₂ owing to land use change. In the year 2000, for example, the model-calculated terrestrial biotic sink was 1730 Mtons C/year, while the emission of CO₂ from changes in land use was 1820 Mtons C/year, a net flux of 90 Mtons C/year emitted to the atmosphere. In the global aquatic environment, enhanced terrestrial inputs of biotically reactive phosphorus (about 8.5 Mtons P/year) and inorganic nitrogen (about 54 Mtons N/year), have induced increased new production and burial of organic carbon in marine sediments, which is a small sink of anthropogenic CO₂. It is predicted that the response of the global land reservoirs of C, N, and P to sustained anthropogenic perturbations will be maintained in the same direction of change over the range of projected scenarios of global population increase and temperature change for the next 35 years. The magnitude of change is significantly larger when the global temperature increase is maximum, especially with respect to the processes of remobilization of the biotically important nutrients nitrogen and phosphorus.     

Applications of Dual-Wall Reverse-Circulation Drilling in Ground Water Exploration and Monitoring

Dual-wall reverse-circulation drilling uses flush-threaded double-wall drill pipe and high-pressure air to provide continuous return of formation and water samples. Cuttings and formation waters are not contaminated with drilling additives or mixed with other borehole material. Up-hole velocity of about 70 ft/sec provides reliable logging of water, mineral or contaminant-bearing strata. Water samples representative of specific strata may be airlifted or bailed to the surface.
In the percussion hammer system, dual-wall drill pipe is advanced through chiefly unconsolidated material by the percussion action of an above-ground pile hammer. The borehole is drilled and temporarily cased in one pass. Wells or monitoring devices are installed as the drill pipe is hydraulically retracted during construction. A rotary head may be adapted as an option to allow dual-wall rotary drilling into consolidated or crystalline formations through a percussion hammer drill string temporarily left in place as a conductor.
The complex geology and variety of geoenvironmental problems in southern California has provided a testing ground for dual-wall drilling on hazardous material site investigations. Several case histories have demonstrated the capabilities and versatility of this method, including: (1) the installation of 4-inch and 6-inch diameter gasoline monitoring and recovery wells through gravels and cobbles at a filling station where hollow-stem auger drilling failed; (2) the confirmation of a dry borehole initially drilled by direct rotary at a landfill; and (3) multiple installations of monitoring devices through municipal refuse at a city of Los Angeles landfill.