Expertise,safety, reliability,and decision making: practical industrial experience

This paper presents our practical experience of expert opinion deduced from concrete field applications, concerning mainly safety and reliability modeling. First, expertise is defined and the approach used for eliciting expertise is shortly described. Quality and value of information from experts are important challenges for decision making from risk analysis. Expertise is very useful for supplying data when not enough field observations are available for estimating parameter uncertainties and quantifying risk analysis models, which are inputs to a decision-making process. Applications presented herein concern mainly the role of expert judgment in reliability.     

Foraging habitats of the seabird community of Europa Island (Mozambique Channel)

We investigated the foraging habitats of the winter breeding community of tropical seabirds from Europa Island (Mozambique Channel) in September 2003. We focused our study on the dominant species of this austral community, the sooty tern (Sterna fuscata), the red-footed booby (Sula sula), and the frigatebirds, including the great (Fregata minor) and the lesser frigatebirds (F. ariel). We considered the at-sea distribution and abundance of these species in relation to chlorophyll concentration, sea-surface temperatures, sea-surface height anomalies, depth of the thermocline, distance to the colony, and presence of surface marine predators, flying fishes and other seabirds. Although the marine environment where seabirds foraged was oligotrophic, it presents the best feeding opportunities for seabirds for the area in winter. Our study demonstrates that the winter-breeding seabird species of Europa Island tend to forage in productive waters in association with other marine predators when possible. Sooty terns and frigatebirds were widely distributed in the whole study area, whereas red-footed boobies were not found farther than 160 km from their colonies and were associated with relatively productive waters. Sooty terns and red-footed boobies were aggregated where flying fishes were abundant. The presence of other marine predators was associated with larger multispecies feeding flocks than when no association occurred. Sooty terns, which are numerically dominant at Europa and adopted network foraging, seem to be catalysts of feeding events, and represented a good target for the other foraging species, especially frigatebirds. However, when possible, frigatebirds favour association with flocks of red-footed boobies.Communicated by S.A. Poulet, Roscoff     

Development of an SPME-GC-MS/MS method for the determination of pesticides in rainwater: laboratory and field experiments

A solid-phase microextraction -- coupled to a gas chromatography -- ion trap tandem mass spectrometry (SPME-GC-MS/MS) method was developed for the quantitative determination in rainwater of 8 pesticides amongst the most used in France and 3 triazines metabolites. The main factors affecting the SPME process were studied. Using a 3 mL sample, the method developed showed good linearity for concentrations ranging from 0.05 to 50 microgL(-1) with correlation coefficients between 0.997 and 0.9999 and relative standard deviations (% RSD) below 14%. The study of matrix effects showed that rainwater was too diluted to have any significant influence on the extraction efficiency. To validate the method, a field campaign was carried out on the rain events, which occurred in Strasbourg during a one-year period. The rain concentrations showed patterns of high pesticide concentrations during spring months, which were correlated to the spraying periods of most of these substances.     

Toward harmonizing prospective effectiveness assessment for road safety: Comparing tools in standard test case simulations

Abstract

Objective: With the overall goal to harmonize prospective effectiveness assessment of active safety systems, the specific objective of this study is to identify and evaluate sources of variation in virtual precrash simulations and to suggest topics for harmonization resulting in increased comparability and thus trustworthiness of virtual simulation-based prospective effectiveness assessment.

Methods: A round-robin assessment of the effectiveness of advanced driver assistance systems was performed using an array of state-of-the-art virtual simulation tools on a set of standard test cases. The results were analyzed to examine reasons for deviations in order to identify and assess aspects that need to be harmonized and standardized. Deviations between results calculated by independent engineering teams using their own tools should be minimized if the research question is precisely formulated regarding input data, models, and postprocessing steps.

Results: Two groups of sources of variations were identified; one group (mostly related to the implementation of the system under test) can be eliminated by using a more accurately formulated research question, whereas the other group highlights further harmonization needs because it addresses specific differences in simulation tool setups. Time-to-collision calculations, vehicle dynamics, especially braking behavior, and hit-point position specification were found to be the main sources of variation.

Conclusions: The study identified variations that can arise from the use of different simulation setups in assessment of the effectiveness of active safety systems. The research presented is a first of its kind and provides significant input to the overall goal of harmonization by identifying specific items for standardization. Future activities aim at further specification of methods for prospective assessments of the effectiveness of active safety, which will enhance comparability and trustworthiness in this kind of studies and thus contribute to increased traffic safety.     

Assessing the impact of biological control of Plutella xylostella through the application of Lotka–Volterra model

The Lotka–Volterra model was applied to the population densities of diamondback moth (DBM), Plutella xylostella (L.) and its exotic larval parasitoid Diadegma semiclausum (Hellen) data that was collected earlier by icipe's DBM biological control team. The collections were done for 15 months before the release and 36 months after release of the parasitoid in two areas; in Werugha, Coast Province of Kenya and Tharuni, Central Province of Kenya, respectively. For each area in pre- and post-release periods, we estimated Lotka–Volterra model parameters from the minimization of the loss function between the theoretical and experimental time-series datasets following the Nelder-Mead multidimensional method. The model estimated a reduction in the value of the steady state of DBM population from 4.86 to 2.17 in Werugha and from 6.11 to 3.76 and 3.45 (with and without exclusion of the time before D. semiclausum recovery) in Tharuni when transiting from the pre- and post-release periods, respectively. This change was a consequence of the newly introduced parasitoid, in the areas. The study presented a successful and detailed technique for non-linear model parameters restoration which was demonstrated by the correct mimicking of empirical datasets from the classical biological control with D. semiclausum, in different areas of Kenya. The applied model has measured the parasitoids impact on the DBM biological control through a quantitative estimate of the effectiveness of the newly introduced species D. semiclausum. These equations may therefore be used as tool for decision making in the implementation for such pests’ management system strategy.     

Evaluation of discrete host–parasitoid models for diamondback moth and Diadegma semiclausum field time population density series

The performance of discrete mathematical models to describe the population dynamics of diamondback moth (DBM) (Plutella xylostella L.) and its parasitoid Diadegma semiclausum was investigated. The parameter values for several well-known models (Nicholson–Bailey, Hassell and Varley, Beddington, Free and Lawton, May, Holling type 2, 3 and Getz and Mills functional responses) were estimated. The models were tested on 20 consecutive sets of time series data collected at 14 days interval for pest and parasitoid populations obtained from a highland cabbage growing area in eastern Kenya. Model parameters were estimated from minimized squared difference between the numerical solution of the model equations and the empirical data using Powell's method. Maximum calculated DBM growth rates varied between 0.02 and 0.07. The carrying capacity determined at 16.5 DBM/plant by the Beddington et al. model was within the range of field data. However, all the estimated parameter values relating to the parasitoid, including the instantaneous searching rate (0.07–0.28), per capita searching efficiency (0.20–0.27), search time (5.20–5.33), handling time (0.77–0.90), and parasitism aggregation index (0.33), were well outside the range encountered empirically. All models evaluated for DBM under Durbin–Watson criteria, except the May model, were not autocorrelated with respect to residuals. In contrast, the criteria applied to the parasitoid residuals showed strong autocorrelations. Thus, these models failed to estimate parasitoid dynamics. We conclude that the interactions of the DBM with its parasitoid cannot be explained by any of the models tested. Two factors may be associated with this failure. First, the parasitoid in this integrated biological control system may not be playing a major role in regulating DBM population. Second, and perhaps more likely, poor correlations reflect gross inadequacies in the theoretical assumptions that underlie the existing models.     

Biotransformation of phenylurea herbicides by a soil bacterial strain, Arthrobacter sp. N2: structure, ecotoxicity and fate of diuron metabolite with soil fungi

In order to assess the influence of the aromatic substitution on the ability of a soil bacterial strain, Arthrobacter sp. N2, to degrade phenylurea herbicides, biotransformation assays were performed in mineral medium with resting cells of this soil bacterial strain on three phenylurea herbicides (diuron, chlorotoluron and isoproturon). Each herbicide considered, led to the formation of only one metabolite detected by HPLC analysis. After isolation, the metabolites were identified by NMR and MS, as the corresponding substituted anilines. According to the Microtox test (realized on the bacterium Vibrio fischeri), these metabolites presented non-target toxicity far more important (up to 600 times higher for 4-isopropylaniline) than the parent molecule. For isoproturon and chlorotoluron, the amount of substituted anilines obtained at the end of the biotransformation was very low, whereas the biotransformation of diuron into 3,4-dichloroaniline was almost quantitative. In this last case, the degradation product accumulated in the medium. In soil, other microorganisms are present that might degrade it. So the biotransformation of 3,4-dichloroaniline was then tested with four fungal strains: Aspergillus niger, Beauveria bassiana, Cunninghamella echinulata var. elegans and Mortierella isabellina. The aniline was further transformed with all the microorganisms tested. Only one metabolite was detected by HPLC analysis and after isolation, it was identified to be 3,4-dichloroacetanilide. This acetylated compound led to biological effects less important on V. fischeri than 3,4-dichloroaniline. These results stress the importance of identifying the degradation products to assess the impact of a polluting agent. Indeed, the pollutant may undergo transformation yielding compounds more toxic than the parent molecule.     

Co-composting of paper mill sludge and hardwood sawdust under two types of in-vessel processes

Recycling of organic residues by composting is becoming an acceptable practice in our society. Co-composting dewatered paper mill sludge (PMS) and hardwood sawdust, two readily available materials in Canada, was investigated using uncontrolled and controlled in-vessel processes. The composted materials were characterized for total C and N, water-soluble, acid-hydrolyzable, and non-hydrolyzable N, extractable lipids, and by Fourier Transform Infrared (FT-IR) spectrophotometry. In the controlled scale process, the loss of organic matter was approximately 65% higher than in the uncontrolled process. After undergoing initial fluctuations in N fractions during the first two days of composting, by the end of the process, concentrations of water-soluble N decreased while those of acid-hydrolyzable and nonhydrolyzable N increased in the controlled process, whereas in the uncontrolled process, water-soluble N increased, but N in the other two fractions decreased continuously, indicating that the biochemical transformations of organic matter were not completed. Data on extractable lipids and FT-IR spectra suggest that the compost produced from the controlled process was bio-stable after 14 days, while the uncontrolled process was not stabilized after 18 days. In addition, FT-IR data suggest the biological activity during composting centered mainly on the degradation of aliphatic structures while aromatic structures were preserved. The co-composting of the PMS and hardwood sawdust can be successfully achieved if aeration, moisture, and bio available C/N ratios are optimized to reduce losses of N.     

Confronting environmental pressure,environmental quality and human health impact indicators of priority air emissions

This paper evaluates the ranking of 21 priority air pollutants with three indicator schemes: environmental pressure indicator (EPI), environmental quality indicator (EQI), and human health effect indicator (HEI). The EPI and EQI compare the emissions and concentrations with the target emissions and target concentrations, respectively. The HEI comprehends the steps from cause (i.e. national emissions) to effect (i.e. human health effects), and is the total human health burden, expressed in Disability Adjusted Life Years per year of exposure (DALYs year^?1). We estimated a health burden in the Netherlands of 41 × 10³ DALYs year^?1 caused by Dutch air emissions of PM10 and its precursors in the year 2003. The burden due to 17 carcinogenic substances emitted to air, was much lower (140 DALYs year^?1). In contrast, when the same substances were evaluated regarding environmental pressure and environmental quality, carbon tetrachloride (pressure) and benzo[a]pyrene (quality) were of highest importance, whereas the importance of PM10 was substantially lower. This result is remarkable, because for the majority of substances evaluated, the target concentrations and target emissions are based on preventing human health damage. The differences in relevance are explained by the different weighting of interests in the indicators. The HEI is based on concentration–response relations, whereas the EPI and EQI also depend on other, policy-based, principles and on technical feasibility. Therefore, to effectively prioritize emission reduction measures in policy-making, substances should not only be evaluated as to whether emission targets and environmental quality targets are reached, but they should be evaluated regarding their human health impact as well. In this context, the HEI is a suitable indicator to evaluate the human health impact.