Chemcatcher and DGT passive sampling devices for regulatory monitoring of trace metals in surface water

This work aimed to evaluate whether the performance of passive sampling devices in measuring time-weighted average (TWA) concentrations supports their application in regulatory monitoring of trace metals in surface waters, such as for the European Union's Water Framework Directive (WFD). The ability of the Chemcatcher and the diffusive gradient in thin film (DGT) device sampler to provide comparable TWA concentrations of Cd, Cu, Ni, Pb and Zn was tested through consecutive and overlapping deployments (7-28 days) in the River Meuse (The Netherlands). In order to evaluate the consistency of these TWA labile metal concentrations, these were assessed against total and filtered concentrations measured at relatively high frequencies by two teams using standard monitoring procedures, and metal species predicted by equilibrium speciation modeling using Visual MINTEQ. For Cd and Zn, the concentrations obtained with filtered water samples and the passive sampling devices were generally similar. The samplers consistently underestimated filtered concentrations of Cu and Ni, in agreement with their respective predicted speciation. For Pb, a small labile fraction was mainly responsible for low sampler accumulation and hence high measurement uncertainty. While only the high frequency of spot sampling procedures enabled the observation of higher Cd concentrations during the first 14 days, consecutive DGT deployments were able to detect it and provide a reasonable estimate of ambient concentrations. The range of concentrations measured by spot and passive sampling, for exposures up to 28 days, demonstrated that both modes of monitoring were equally reliable. Passive sampling provides information that cannot be obtained by a realistic spot sampling frequency and this may impact on the ability to detect trends and assess monitoring data against environmental quality standards when concentrations fluctuate.     

Relative kinetic measurements of rate coefficients for the gas-phase reactions of Cl atoms and OH radicals with a series of methyl alkyl esters

Relative kinetic studies have been performed on the reactions of Cl atoms with a series of methyl alkyl esters in a 405-liter borosilicate glass chamber at (298 ± 3) K and one atmosphere of synthetic air using in situ FTIR spectroscopy to monitor the reactants. Rate coefficients (in units of cm³ molecule^?1 s^?1) were determined for the following compounds: methyl acetate (2.48 ± 0.58) × 10^?12; methyl propanoate (1.68 ± 0.36) × 10^?11; methyl butanoate (4.77 ± 0.87) × 10^?11; methyl pentanoate (7.84 ± 1.15) × 10^?11; methyl hexanoate (1.09 ± 0.31) × 10^?10; methyl heptanoate (1.56 ± 0.37) × 10^?10; methyl cyclohexane carboxylate (3.32 ± 0.76) × 10^?10; methyl-2-methyl butanoate (9.41 ± 1.39) × 10^?11.In addition rate coefficients (in units of 10^?11 cm³ molecule^?1 s^?1) have been obtained for the reactions of OH radicals with the following compounds: methyl butanoate (3.55 ± 0.71), methyl pentanoate (5.41 ± 1.08), and methyl-2-methyl butanoate (4.08 ± 0.82).Using the kinetic rate data tropospheric lifetimes for the methyl alkyl esters with respect to their reactions with OH, and Cl have been estimated for typical ambient air concentrations of these oxidants.     

Efficient thinning regimes for Eucalyptus fastigata: Multi-objective stand-level optimisation using the island model genetic algorithm

A stand-level optimisation problem formulated to determine a set of efficient thinning regimes satisfying two objectives, i.e. value production for sawlog harvesting and volume production for a pulpwood market, was demonstrated for a Eucalyptus fastigata trial in Kaingaroa Forest, New Zealand. Genetic algorithms were used to estimate the set of efficient thinning regimes (i.e. regimes that occur when it is not possible to increase the achievement of one objective without reducing another) known as a Pareto frontier. Each thinning regime specified a unique combination of initial planting density; frequency, timing and intensity of thinning; final crop number; and rotation length. Specifications for the “best” regime in the Pareto set (i.e. the one that satisfied a balanced trade-off between value and volume production) were similar to those recommended through professional judgment based on pooled long-term field observations from different eucalypt species grown throughout New Zealand. The advantage of Pareto optimality was the ability of not only identifying a unique thinning regime, but equally efficient regimes each providing a different combination of value and volume production. Research on this approach has the potential of being applied to other forest sites, providing there is sufficient re-measurement data to reflect stand growth dynamics.     

Comparison of Streambed Sediment and Aquatic Biota as Media for Characterizing Trace Elements and Organochlorine Compounds in the Willamette Basin, Oregon

During 1992–93, 27 organochlorine compounds (pesticides plus total PCB) and 17 trace elements were analyzed in bed sediment and aquatic biota from 20 stream sites in the Willamette Basin as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Data from each medium were compared to evaluate their relative effectiveness for assessing occurrence (broadly defined as documentation of important concentrations) of these constituents. Except for Cd, Hg, Se, and Ag, trace element concentrations generally were higher in bed sediment than in biota. Conversely, although frequencies of detection for organochlorine compounds in biota were only slightly greater than in bed sediment, actual concentrations in biota (normalized to lipid) were as much as 19 times those in sediment (normalized to organic carbon). Sculpin (Cottus spp.) and Asiatic clams (Corbicula fluminea), found at 14 and 7 sites, respectively, were the most widespread taxa collected during the study. Concentrations of trace elements, particularly As and Cu, were typically greater in Asiatic clams than in sculpin. In contrast, almost half of the organochlorine compounds analyzed were found in sculpin, but only DDT and its degradation products were detected in Asiatic clams; this may be related to the lipid content of sculpin, which was about three times higher than for clams. Thus, the medium of choice for assessing occurrence depends largely on the constituent(s) of interest.     

Sorption of Zn(II) in aqueous solutions by scoria

We conducted kinetic and equilibrium sorption experiments on removal of Zn(II) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The batch-type kinetic sorption tests under variable conditions indicated that the percentage of Zn(II) removal by scoria increases with decreasing initial Zn(II) concentration, particle size, and sorbate/sorbent ratio. However, the sorption capacity decreases with the decrease of the initial Zn(II) concentration and sorbate/sorbent ratio. Equilibrium sorption tests show that Jeju scoria has a larger capacity and affinity for Zn(II) sorption than commercial powdered activated carbon (PAC); at initial Zn(II) concentrations of more than 10mM, the sorption capacity of Jeju scoria is about 1.5 times higher than that of PAC. The acquired sorption data are better fitted to the Langmuir isotherm than the Freundlich isotherm. Careful examination of ionic concentrations in sorption batches suggests that the sorption behavior is mainly controlled by cation exchange and typically displays characteristics of 'cation sorption'. The Zn(II) removal capacity decreases when solution pH decreases because of the competition with hydrogen ions for sorption sites, while the Zn(II) removal capacity increases under higher pH conditions, likely due to hydroxide precipitation. At an initial Zn(II) concentration of 5.0mM, the removal increases from 70% to 96% with the increase of initial pH from 3.0 to 7.0. We recommend Jeju scoria as an economic and efficient sorbent for Zn(II) in contaminated water.     

ECOSYSTEM MODELING OF A FORESTED RIVER BASIN1

ABSTRACT: A present concern in decision making processes for forest land use is the environmental effects of land use activities on water, air, and the land itself. Criteria for evaluating the magnitude and detriment of environmental impacts are not definite since it is often difficult to isolate a particular activity as the cause of a particular impact. Instead, interactions between various forest practices must be considered along with their integrated impacts. In order to provide an effective decision tool, the College of Forest Resources, University of Washington, is modeling the forest ecosystem of the Snohomish River Basin located in the Cascade Mountains of western Washington. The project consists of a general system model comprised of subsystem models dealing with product conversion processes, forest production processes, recreation supply processes, wildlife and fisheries supply processes, and the interactions of these processes with water and the atmosphere. The system model is interfaced with a computerized multiple player management game which enables land managers, manufacturing managers, and regulation agency personnel to make management decisions and respond to indications of lack of environmental control. Responses of the hydrologic system to various management decisions are simulated by the water subsystem model. The responses being considered include surface flow quantity and water quality. The model emphasizes the monitoring of non-point as well as point source impacts rather than predicting short-term hydrographs. The significance of impacts vary with land use patterns and the goals of the game player. Therefore, the model has flexible resolution and is able to predict hydrologic conditions for both large and small scale. The water subsystem model responds to management decisions by interpreting the effects of management options selected by game players for 40-acre cells within the Basin. The model then determines which streams are immediately affected, defines the watersheds contributing to these streams, and extracts from a resource data bank the information needed to define model parameters. Using these parameters and precipitation inputs, mean flow discharge on a montly and annual basis is calculated for the impactcd sub watersheds as well as 21 major watersheds of the Basin. Water quality responses predicted for these watersheds include suspended sediment concentration, temperature increases due to stream exposure, dissolved oxygen concentrations, the effects of fertilization on nitrogen content, biocide and herbicide effects, and residues from product conversion processes.     

The Capacity to Detect Change Stream Fish Communities Characteristics at the Site-Level in the Lake Ontario Basin

We investigate natural inter-annual variability of fish community measures within streams of the Lake Ontario basin. Given this variability, we examined coefficients of variation (CV) among the community measures and three scenarios pertaining to the capacity of biologists to detect changes in the fish community at the stream site level. Results indicate that Ontario's stream fish communities are highly variable in time. Young-of-the-year rainbow trout growth was the least variable whereas biomass density scored the highest CV of 0.50 among streams (range 0.22-0.99). Given the CVs and relatively equal sample sizes, our measures of the fish community can be ranked from least to most powerful: biomass, density, richness, diversity, and growth of young-of-the-year rainbow trout. Only large changes in measures can typically be detected. For instance, it would take 4-6 years of monitoring before and after a pulse perturbation to detect a 50 % change in species richness or diversity. We suggest that monitoring abundance is unlikely to result in the detection of small impacts within a short period of time and that large effects can be masked by low statistical power. This evidence voices the need for more research into better sampling methods, experimental designs, and choice of indicators to support monitoring programs for flowing waters.     

Temperature-dependent rate coefficients for the reactions of Cl atoms with methyl methacrylate,methyl acrylate and butyl methacrylate at atmospheric pressure

Rate coefficients for the gas-phase reactions of Cl atoms with a series of unsaturated esters CH₂C(CH₃)C(O)OCH₃ (MMA), CH₂CHC(O)OCH₃ (MAC) and CH₂C(CH₃)C(O)O(CH₂)₃CH₃ (BMA) have been measured as a function of temperature by the relative technique in an environmental chamber with in situ FTIR detection of reactants. The rate coefficients obtained at 298 K in one atmosphere of nitrogen or synthetic air using propene, isobutene and 1,3-butadiene as reference hydrocarbons were (in units of 10^?10 cm³ molecule^?1 s^?1) as follows: k_(Cl+MMA) = 2.82 ± 0.93, k_(Cl+MAC) = 2.04 ± 0.54 and k_(Cl+BMA) = 3.60 ± 0.87. The kinetic data obtained over the temperature range 287–313 K were used to derive the following Arrhenius expressions (in units of cm³ molecule^?1 s^?1): k_(Cl+MMA) = (13.9 ± 7.8) × 10^?15 exp[(2904 ± 420)/T], k_(Cl+MAC) = (0.4 ± 0.2) × 10^?15 exp[(3884 ± 879)/T], k_(Cl+BMA) = (0.98 ± 0.42) × 10^?15 exp[(3779 ± 850)/T]. All the rate coefficients display a slight negative temperature dependence which points to the importance of the reversibility of the addition mechanism for these reactions. This work constitutes the first kinetic and temperature dependence study of the reactions cited above.An analysis of the available rates of addition of Cl atoms and OH radicals to the double bond of alkenes and unsaturated and oxygenated volatile organic compounds (VOCs) at 298 K has shown that they can be related by the expression: log k_OH = 1.09 log k_Cl ? 0.10. In addition, a correlation between the reactivity of unsaturated VOCs toward OH radicals and Cl atoms and the HOMO of the unsaturated VOC is presented. Tropospheric implications of the results are also discussed.     

Model and input uncertainty in multi-media fate modeling: benzo[a]pyrene concentrations in Europe

This paper evaluates the contribution of (i) uncertainty in substance properties, (ii) lack of spatial variability, (iii) intermodel differences and (iv) neglecting sorption to black carbon (BC) to the uncertainty of Benzo[a]pyrene (BaP) concentrations in European air, soil and fresh water predicted by the multi-media fate model Simplebox. Uncertainty in substance properties was quantified using probabilistic modeling. The influence of spatial variability was quantified by estimating variation in predicted concentrations with three spatially explicit fate models (Impact 2002, EVn BETR and BETR Global). Intermodel differences were quantified by comparing concentration estimates of Simplebox, Impact 2002, EVn BETR and the European part of BETR Global. Finally, predictions of a BC-inclusive version of Simplebox were compared with predictions of a BC-exclusive version. For air concentrations of BaP, the lack of spatial variability in emissions was most influential. For freshwater concentrations of BaP, intermodel differences and lack of spatial variability in dimensions of fresh water bodies were the dominant sources of uncertainty. For soil, all sources of uncertainty were of comparable magnitude. Our results indicate that uncertainty in Simplebox can be as large as three orders of magnitude for BaP concentrations in the environment and would be substantially underestimated by focusing on one source of uncertainty only.     

What does it mean to transform knowledge into action in falls prevention research? Perspectives from the Canadian Institutes of Health Research

Introduction

The concept of knowledge translation as defined by the Canadian Institutes for Health Research and the Knowledge to Action Cycle, described by Graham et al (Graham et al., 2006), are used to make a case for the importance of using a conceptual model to describe moving knowledge into action in the area of falls prevention.

Method

There is a large body of research in the area of falls prevention. It would seem that in many areas it is clear what is needed to prevent falls and further syntheses can determine where the evidence is sufficiently robust to warrant its implementation as well as where the gaps are that require further basic research.

Conclusion

The phases of the action cycle highlight seven areas that should be paid attention to in order to maximize chances of successful implementation.