Sustainable construction--the role of environmental assessment tools

Construction has been accused of causing environmental problems ranging from excessive consumption of global resources both in terms of construction and building operation to the pollution of the surrounding environment, and research on green building design and using building materials to minimise environmental impact is already underway. However, relying on the design of a project to achieve the goal of sustainable development, or to minimise impacts through appropriate management on site, is not sufficient to handle the current problem. The aim for sustainability assessment goes even further than at the design stage of a project to consider its importance at an early stage, before any detailed design or even before a commitment is made to go ahead with a development. However, little or no concern has been given to the importance of selecting more environmentally friendly designs during the project appraisal stage; the stage when environmental matters are best incorporated. The main objectives of this paper are to examine the development, role and limitations of current environmental building assessment methods in ascertaining building sustainability used in different countries which leads to discuss the concept of developing a. sustainability model for project appraisal based on a multi-dimensional approach, that will allow alternatives to be ranked is discussed in detail in the paper.     

Particle fluxes above forests: observations, methodological considerations and method comparisons

This paper reports a study designed to test, evaluate and compare micro-meteorological methods for determining the particle number flux above forest canopies. Half-hour average particle number fluxes above a representative broad-leaved forest in Denmark derived using eddy covariance range from -7x10(7) m(-2) s(-1) (1st percentile) to 5x10(7) m(-2) s(-1) (99th percentile), and have a median value of -1.6x10(6) m(-2) s(-1). The statistical uncertainties associated with the particle number flux estimates are larger than those for momentum fluxes and imply that in this data set approximately half of the particle number fluxes are not statistically different to zero. Particle number fluxes from relaxed eddy accumulation (REA) and eddy covariance are highly correlated and of almost identical magnitude. Flux estimates from the co-spectral and dissipation methods are also correlated with those from eddy covariance but exhibit higher absolute magnitude of fluxes.     

Plant and Soil System Responses to Ozone After 3 Years in a Lysimeter Study with Juvenile Beech (Fagus sylvatica L.)

A lysimeter study was performed to monitor effects of elevated ozone on juvenile trees of Fagus sylvatica L. as well as on the plant–soil system. During a fumigation period over almost three growing seasons, parameters related to plant growth, phenological development and physiology as well as soil functions were studied. The data analyses identified elevated ozone to delay leaf phenology at early and to accelerate it at late developmental stages, to reduce growth, some leaf nutrients (Ca, K) as well as some soluble phenolics (hydroxycinnamic acid derivatives, total flavonol glycosides). No or very weak ozone effects were found in mobile carbon pools of leaves (starch, sucrose), and other phenolic compounds (flavans). Altered gene expression related to stress and carbon cycling corresponded well with findings from leaf phenology and chemical composition analyses indicating earlier senescence and oxidative stress in leaves under elevated ozone. Conversely in the soil system, no effects of ozone were detected on soil enzyme activities, rates of litter degradation and lysimeter water balances. Despite the fact that the three reported years 2003–2005 were climatically very contrasting including a hot and dry as well as an extremely wet summer, and also mild as well as cold winters, the influence of ozone on a number of plant parameters is remarkably consistent, further underlining the phytotoxic potential of elevated tropospheric ozone levels.     

Comparison of Microscopic and Macroscopic Modeling Approaches for Subsurface Contaminant Transport

The practice of contaminant transport and remediation has shown significant progress in recent years. However, despite the significant progress made, remediation efforts are often delayed by extremely long breakthrough curve tails that render efforts to bring the level of contaminants below the regulatory standards inefficient. One hypothesis is that these long tails are due to the reservoir-like slow diffusive processes in soil micropore zones. This study compares the effects of micropores at macroscopic and microscopic levels and establishes a link between these approaches for validation and calibration purposes. The link between macroscopic and microscopic levels is established through comparisons and testing of the two models while incorporating appropriate scale and boundary effects. Despite the differences in conceptual approaches and simulation time, the two approaches rendered meaningful results. The link helps forecast the effects of micropore zone transport processes in the subsurface efficiently and thus allows development of numerical tools that could contribute towards more efficient remediation design.     

An evaluation of global QSAR models for the prediction of the toxicity of phenols to Tetrahymena pyriformis

This study presents an analysis of the ability of a two-parameter response surface, a multiple linear regression and a neural network model to produce global quantitative structure-activity relationships (QSARs) to predict the toxic potency of phenols to Tetrahymena pyriformis. The phenolic toxicity data set analysed is characterised by multiple mechanisms of toxic action. The study aimed to evaluate the confidence that can be applied to the modelling of the differing mechanisms of action. Assessment of confidence was decided in terms of whether the statistics for the global models reflect the ability of the QSARs to model the individual mechanisms of toxic action present in the data set. The results showed that the global statistics only reflected the ability of models to predict the two non-covalent mechanisms (polar narcosis and respiratory uncoupling), with the metabolically transformed and electrophilic mechanism (pre-electrophiles and soft electrophiles) being modelled poorly by all three model building methods. The results confirm the difficulty in modelling electrophilic mechanisms of toxic action. The results also highlight the fact that this poor predictivity is often 'hidden' in good statistical fit of some global models. In particular these results emphasise that for practical predictive purposes the mechanistic applicability domain is required to give confidence to estimated toxicity values.     

Identifying the largest individual sample value from a two-way composite sampling design

Composite sampling techniques for identifying the largest individual sample value seem to be cost effective when the composite samples are internally homogeneous. However, since it is not always possible to form homogeneous composite samples, these methods can lead to higher costs than expected. In this paper we propose a two-way composite sampling design as a way to improve on the cost effectiveness of the methods available to identify the largest individual sample value.     

Unprecedented bleaching-induced mortality in Porites spp. at Rangiroa Atoll, French Polynesia

In April-May 1998, mass coral bleaching was observed in the lagoon of Rangiroa Atoll, Tuamotu Archipelago, French Polynesia. Six months later, the extent of bleaching-induced coral mortality was assessed at three sites. Corals in the fast-growing genus Pocillopora had experienced >99% mortality. Many large colonies of the slow-growing genus Porites (mean horizontal cross-sectional area 5.8 m²) had also died - a phenomenon not previously observed in French Polynesia and virtually unprecedented world-wide. At one site, 25% of colonies, or 44% of the pre-bleaching cover of living Porites, experienced whole-colony mortality. At the two other sites, recently dead Porites accounted for 41% and 82% of the pre-bleaching live cover. Mortality in Porites was negatively correlated with depth between 1.5 and 5 m. Using a 50-year dataset of mean monthly sea surface temperature (SST), derived from ship- and satellite-borne instruments, we show that bleaching occurred during a period of exceptionally high summer SST. 1998 was the first year in which mean monthly SSTs exceeded the 1961-1990 upper 95% confidence limit (29.4°C) for a period of three consecutive months. We suggest that the sustained 3-month anomaly in local summer SST was a major cause of coral mortality, but do not discount the synergistic effect of solar radiation. Recovery of the size-frequency distribution of Porites colonies to pre-bleaching levels may take at least 100 years.     

Atmospheric dinitrogen fixation by benthic communities of Tikehau Lagoon (Tuamotu Archipelago, French Polynesia) and its contribution to benthic primary production

Acetylene reduction rates were measured in lagoonal sediments, cyanobacterial mats and limestone surfaces between 1991 and 1995 at many sites, depths and seasons; all the studied substrata contained cyanobacteria. The acetylene reduction/¹⁵N₂ fixation ratio was measured for the different communities and varied between 1.8 and 4.8, depending on substratum. Fixation rates were 1.7 to 7 times higher during daylight compared to night-time rates. N₂ fixation rates ranged from 0.4 to 3.9 mg N m^-2 day^-1 for the lagoonal sediment/mat communities, and the rate was about 2 mg N m^-2 day^-1 for the lagoonal limestone substrata. Total lagoonal benthic N₂ fixation contributed 24.4% of the total nitrogen requirement for the benthic primary production of benthic communities of the lagoon. The input of N₂ fixation by the microbial planktonic communities (including cyanobacteria) of the lagoon, which are highly productive, is unquantified but is likely to be large.