The speed of an isolume: a shrimp's eye view

Using data from electroretinogram recordings, we designed a submersible light meter with a spectral luminous efficiency comparable to that of a vertically migrating shrimp. Using this light meter on the “Johnson Sea Link” submersible, we were able to ascend with the isolumes (preferred light levels) associated with the sergestid and euphausiid shrimp layers. The speed of the submersible's movement was recorded and correlated with simultaneous measurements of surface irradiance. In situ measurements of the downwelling spectral distribution were also made with a fiber optic spectrometer. The average measured speed of the sergestid isolume was 8.8 cm s⁻¹, while that of the shallower euphausiid isolume was 6.7 cm s⁻¹. These values are different from those calculated using average diffuse attenuation coefficients and surface light measurements. This difference was due to the broadening of the spectral distribution of downwelling light above 120 m and to the variability of the diffuse attenuation coefficients with depth. These results clearly demonstrate that when investigating the relationship between light and vertical migration patterns, it is important that: (1) the light measurements be made in situ and (2) such measurements take into account the spectral sensitivity of the eyes of the migrators. Received: 7 June 2000 / Accepted: 18 November 2000     

Pharmaceutical residues in the river Rhine--results of a one-decade monitoring programme

In this paper, results of an extensive monitoring programme for pharmaceutical residues in the river Rhine are presented. For one decade (1997 until 2006), the occurrence of widely used human pharmaceuticals like analgesics, lipid regulators, antiepileptics and others has been studied at four locations along the river Rhine. The results of more than 500 analyses clearly prove that compounds such as carbamazepine or diclofenac are regularly found in the river Rhine in concentrations up to several hundred ng per litre. Combining concentration levels with data on water flow enables the calculation of transports, which e.g. for carbamazepine or diclofenac were in the range of several tons per year. The evaluation of the long-term monitoring data shows that only a slight decrease in concentration levels as well as in annual transports can be observed and thus the contamination of the river Rhine by pharmaceutical residues during the last decade has to be regarded as almost constant. Seasonal variations can be detected for bezafibrate, diclofenac and ibuprofen, for which the concentrations are much lower in the summer months. A more effective removal during wastewater treatment in the warmer periods of the year seems to be the major reason for those variations. For carbamazepine, no comparable seasonal effect can be found.     

Cadmium in moose kidney and liver – age and gender dependency, and standardisation for environmental monitoring

In the northern hemisphere moose has been found to be suitable as a monitoring animal for the presence of cadmium in the environment. The metal accumulates mainly in the kidney and the liver, with the rate of accumulation dependent on age and possibly also on gender. Collection of tissue material often results in sample selections with disparate age and gender composition, which makes comparison between different regions and different studies difficult. A previous large scale investigation of metals in kidney and liver from moose in Sweden provided Cd data (n = 3,817 and 3,802, respectively) to further explore the relation between Cd accumulation and age/gender. Based on local averages, the individual deviations were analysed with respect to the factors age and gender resulting in an 'ageing function' for each gender and organ. In addition, estimates of the pure individual variations were obtained; the standard deviations correspond to a factor 1.7-1.9 for the Cd concentration, which indicates that 25-30 samples are needed to give a representative mean value (with RSD approximately 10%). In order to be able to compare results from different studies, all individual results can be transformed to represent a 'standard moose' with respect to age and gender. A comparison along these lines was undertaken between Cd levels in Alaska and Sweden. Finally, a relationship between the Cd levels in kidney and liver was derived, providing at least rough estimates for kidney from liver values (or vice versa).     

Support Vector Machine Modeling Using Particle Swarm Optimization Approach for the Retrieval of Atmospheric Ammonia Concentrations

This study was performed in order to improve the estimation accuracy of atmospheric ammonia (NH₃) concentration levels in the Greater Houston area during extended sampling periods. The approach is based on selecting the appropriate penalty coefficient C and kernel parameter σ ². These parameters directly influence the regression accuracy of the support vector machine (SVM) model. In this paper, two artificial intelligence techniques, particle swarm optimization (PSO) and a genetic algorithm (GA), were used to optimize the SVM model parameters. Data regarding meteorological variables (e.g., ambient temperature and wind direction) and the NH₃ concentration levels were employed to develop our two models. The simulation results indicate that both PSO-SVM and GA-SVM methods are effective tools to model the NH₃ concentration levels and can yield good prediction performance based on statistical evaluation criteria. PSO-SVM provides higher retrieval accuracy and faster running speed than GA-SVM. In addition, we used the PSO-SVM technique to estimate 17 drop-off NH₃ concentration values. We obtained forecasting results with good fitting characteristics to a measured curve. This proved that PSO-SVM is an effective method for estimating unavailable NH₃ concentration data at 3, 4, 5, and 6 parts per billion (ppb), respectively. A 4-ppb NH₃ concentration had the optimum prediction performance of the simulation results. These results showed that the selection of the set-point values is a significant factor in compensating for the atmospheric NH₃ dropout data with the PSO-SVM method. This modeling approach will be useful in the continuous assessment of NH₃ sensor discrete data sources.     

Temporal trends of contaminants in Arctic char (Salvelinus alpinus) from a small lake, southwest Greenland during a warming climate

Hg and legacy POPs were analysed in muscle tissue of a landlocked Arctic char (Salvelinus alpinus) population from a small lake in southwest Greenland. Hg concentrations were available for six years and OC concentrations for five years during the period 1994 to 2008. For two years, stable isotope values of nitrogen (δ(15)N) were analysed in muscle tissue in order to infer trophic effects. Hg, Σ10-PCB, ΣDDT and trans-nonachlor concentrations (OC on wet weight basis) showed an increase with increasing fish length, which had to be accounted for when assessing temporal trends. δ(15)N values had a narrow range, and there was no indication of increasing δ(15)N values with char length confirming the sampled char did not vary in trophic morphs as often seen in Arctic lakes. Length-adjusted Hg concentrations showed a significantly increasing trend during the period 1994 to 2008, while Σ10-PCB, ΣDDT, ΣHCH and trans-nonachlor showed a significantly decreasing trend when expressed on wet weight, and decreasing but not significantly when expressed on lipid weight. The reason for this was that the lipid content of muscle showed a significantly decreasing trend with time. The sum of mean monthly air temperature during May to August measured at a nearby meteorological station showed an increasing trend during the study period, and changing temperature conditions probably influenced the temporal trend of especially Hg concentrations and the lipid content.     

Rapid screening for organochlorine and organophosphorus pesticides in milk using C18 and graphitized carbon black solid phase extraction cleanup

Abstract

A rapid, multiresidue, solid phase extraction (SPE) technique for the isolation and gas chromatographic determination of organochlorine and moderately polar organophosphorus pesticide residues in milk is described. Milk is sonicated with an acetonitrile‐acetone‐methanol mixture and centrifuged. The supernatant is subjected to a cleanup using both C₁₈ and graphitized carbon black SPE columns. The pesticide residues are determined by gas chromatography with electron capture and flame photometric detection. The method required minimal volumes of solvent and resulted in the production of minimal volumes of hazardous waste.     

An Epidemiological Appraisal of the Effects of Ambient Air on Health: Particulates and Oxides of Sulfur

This review has attempted to evaluate the present state of our knowledge of the effects on health in man of environmental exposure to oxides of sulfur, sulfates, and particulate matter. There has been a great deal of activity in this field over the last 15 years, and therefore any collation of this material will represent the selected biases of the reviewer. The conclusions reached can be summarized as follows: (1) These pollutants, as they have been measured in epidemiological investigations, can only be considered as indirect indices of general air pollution and in many cases cannot be separated from each other. Therefore, we cannot incriminate a specific source of any one pollutant as the producer of the most harmful substance to reach the ambient air. Conversely, we cannot excuse any specific source of one pollutant because that specific pollutant has not been found to cause disease at a given concentration. The measurements in ambient air are the net results from all sources of pollution in combination with factors influenced by weather and meteorological considerations. (2) Direct effects from acute, high ambient air pollution disasters have been adequately demonstrated. Significant excess mortality has occurred in association with particular air pollution episodes. All of these episodes have occurred during cold weather, and the effects of temperature must also be considered along with elevated levels of smoke and sulfur oxides. (3) Specific working groups exposed to unusually high levels of these pollutants do not demonstrate dramatic effects. This is presumably related to the fact that susceptible people are self-selected out of these environments. (4) Associations between the prevalence of chronic respiratory disease in the general population and specific levels of these air pollutants have been demonstrated. The major thrusts of epidemiological investigations have been to study the effects of chronic exposure to ambient levels of smoke and sulfur dioxide. The studies to date have collected and analyzed point-prevalence data and information obtained from retrospective investigations. Although epidemiological investigations cannot prove a cause-and-effect relationship, the consistency of the results is such that one must conclude that a causal association is likely. In this reviewer’s opinion we have reached the stage at which we no longer need to demonstrate the effect of past exposure to these pollutants. What is needed now is to demonstrate the effects of current and continued exposure. This will require a better understanding of the natural history and pathophysiology of the diseases thought to be associated with chronic exposure to smoke and sulfur dioxide. Because of the nature of chronic respiratory disease, groups of subjects for whom exposure is known, must be followed over extended periods of time. The logical extension of these observations will be the follow-up of large populations for whom exposure has been reduced. Only by studies of this kind may we be able to prove the cause-and-effect relationship which most likely exists.