Uptake and depuration of PAHs and chlorinated pesticides by semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis)

Semi-batch seawater experiments were conducted to follow the uptake and release of selected PAHs (anthracene, fluorathene, pyrene and B[a]P) and organochlorine pesticides (α-HCH, aldrin, dieldrin, p,p′-DDT) in semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis). Mathematical models were applied to describe the uptake and elimination curves of the contaminants for SPMDs, and kinetic parameters, such as uptake rate constants, and equilibrium triolein/water partitioning coefficients were calculated. SPMD data showed a good fit to estimate rate constant and partition coefficient equations, but only those contaminants which partitioned mainly in the dissolved phase (α-HCH and dieldrin) were well explained for mussels. Poor conformity of the other contaminants indicated mussels uptake by routes other than diffusion, such as ingestion of algae. An apparent equilibrium state was only noted for α-HCH in mussels. Aldrin was not detected in mussels in the first few days of exposure, indicating potential metabolism of this compound. B[a]P was not detected in the triolein of SPMDs, which suggests that the membrane may act as a reservoir. Loss of spiked B[a]P from the triolein was evident in a depuration experiment, which may indicate transfer to the membrane. Rate constants for mussels were higher than those for SPMDs, but the reverse was true for partition coefficients. Overall, mussels and SPMDs had similar uptake rates for all compounds in this study, excluding p,p′-DDT and dieldrin. Contaminant elimination took place more rapidly in mussels, implying that SPMDs are better candidates for detecting episodic discharge of organic contaminants.     

A Model-Based Evaluation of Horizontal Wells for Improving the Functionality of an Urban Reservoir System

A method is proposed for utilizing the storage capacity of unconfined aquifers to increase the efficiency of existing water-supply reservoirs presently losing water to seasonal spillages. The approach proposed uses horizontal wells to control the watertable elevation in the reservoir catchments, permitting a degree of control over the discharge of the streams flowing to the reservoirs. This may provide an alternative to reservoir construction, thus avoiding loss of ecosystems or productive land. The use of horizontal wells provides a range of control options, including increasing stream discharge during summer and reducing and delaying peak discharge from rainfall events during winter. A numerical groundwater model is utilized to simulate the operation of hypothetical horizontal wells within a water supply catchment of Auckland City, New Zealand. Results suggest potential for a significant increase in summer stream flow, coupled with a reduction in winter peak discharges associated with present reservoir spillage.     

Dealing with earthquakes: the practice of seismic engineering ‘as if people mattered’

This paper sets out to explore the different ways in which communities deal with earthquakes. As is well known, the ability to recover from a damaging earthquake varies greatly across the world. The events of 2010 were of course a striking reminder of this, when the death toll from the Haïti earthquake was at least 100,000; in the very different conditions of Chile, a much larger event the same year killed just 525 people. In a narrow sense, much of the difference can be explained in terms of the engineering properties of the physical infrastructure affected; the better it has been designed and constructed to withstand strong ground shaking, the greater the chance that the community affected has of recovering quickly. However, the central thesis of this paper is that the ability of a community to deal with earthquakes involves much more than just technical factors. Seismically resilient buildings and other infrastructure will only be in place when an earthquake strikes if there has been a willingness and ability to devote the necessary resources to building them. Moreover, taking prior steps to limit physical damage is only one part of the process for dealing with earthquakes; providing for immediate post-earthquake needs and for the longer term rebuilding of communities is also important. To pursue these issues further, and how they might affect engineers, I visited four widely differing regions of high seismicity. During this study tour, I examined the societal context in which seismic engineers operate and talked to many people involved in earthquake protection and response. The intention was to identify the ways in which the ability of communities to deal with earthquakes depend on societal factors such as economics, politics and more general cultural dimensions. Based on these investigations, I believe that seismic engineers can contribute more effectively to ensuring successful outcomes after an earthquake strikes if fully aware of these societal factors. We need to look beyond our narrow technical field of providing earthquake resistant facilities and widen our vision to consider the complex systems, both ‘hard’ and ‘soft’, in which those facilities will operate. E. F. Schumacher’s famous book (Schumacher 1973) ‘Small is beautiful’ has the subtitle ‘the study of economics as if people mattered’. I believe that seismic engineering should be practised ‘as if people mattered’.