Jack pine growth and elemental composition are affected by saline tailings water

In the processing of oil sands from Alberta's Athabasca formation, large quantities of alkaline, saline tailings and associated process-affected waters are produced. These waters may have a negative effect on plants used in reclamation of mined areas in this region of the northern boreal forest. In the present study, we examined the effects of process-affected water on the growth and elemental composition of jack pine (Pinus banksiana Lamb.) seedlings. Seedlings were grown in sand culture, and treated with tailings water to which mineral nutrients had been added. One-month-old seedlings were treated for 14 d, and all measured growth parameters were reduced. Growth and shoot elemental composition were also measured in seven-month-old seedlings that were treated for 10 wk with process-affected water. Shoots had significantly elevated levels of Na, Cl, S, P, B, and Sr, and significantly reduced levels of Fe, Mo, Ba, and K. The relationships between elemental composition and seedling growth and injury were examined using multiple regression. Growth rates, dry weights, and carotenoid content were reduced, but were not related to shoot elemental composition. Needle necrosis was positively related to tissue Na and Cl. Results indicate that reclamation planning must consider substrate Na and Cl levels when planting jack pine on tailings-affected sites.     

Influence of humic substances on the toxic effects of cadmium and zinc to the green alga Pseudokirchneriella subcapitata

A method combining (1 h) algal photosynthesis inhibition tests and tangential-flow ultrafiltration (TFF) technique (cut-off 1 kDa) was used to determine the effect of humic substances (HS) on acute metal toxicity to Pseudokirchneriella subcapitata. Three "standard" HS (soil and peat humic acids and Suwannee River fulvic acids) at two concentrations (1 and 5 mg/l) and two metals (Zn at 390 microg/l and Cd at 200 microg/l) were studied. Toxicity of Cd and Zn to P. subcapitata was significantly (p<0.05) reduced in the presence of humic acids (HA) but not in the presence of Suwannee River fulvic acids (SRFA). Metal partitioning between colloidal (1 microm-1 kDa) and truly dissolved (<1 kDa) fractions was found to match a decrease of metal toxicity in the presence of HA, but not in the presence of SRFA. The results suggested that HA reduced Cd and Zn toxicity in two different ways: (1) HA decrease the amount of free metal ions. Metal-HA complexes are high molecular weight, relatively stable with regard to metal-exchange reactions and consequently the metals were less bioavailable. (2) HA adsorbed onto algal surfaces, shielded the cells from free Cd and Zn ions. Several possible explanations can be postulated to account for the observed SRFA results: (1) Cd- and Zn-SRFA complexes are thought to be labile (i.e. undergo rapid dissociation); (2) SRFA coagulated, presumably during equilibration, and that coagulation altered metal complexing behavior of SRFA; (3) FA has a lower ability to adsorb on cell membranes at pH>7.     

Intercomparison of alpha and gamma spectrometry techniques used in (210)Pb geochronology

(210)Pb geochronology is a widely used tool in sedimentological studies aimed at the absolute ages of modern sediments (up to 100 years). (210)Pb activities required to model sedimentation regimes are measured using either alpha, gamma or beta spectrometry. Sediment accumulation rates derived from (210)Pb activity profiles measured by these methods are often used interchangeably in mass balance studies. Yet there is a lack of investigations considering the comparability of data derived using different analytical methods. Differences between methods could be caused by different behaviors of (210)Pb and (210)Po (used for alpha measurement) in the marine environment. In gamma spectrometry errors may arise when many gamma emitters are measured simultaneously and their activity peaks overlap. In alpha spectrometry chemical separation of (210)Po may result in analytical error due to incomplete sample dissolution. In the present study we evaluate total, supported and excess (210)Pb activities and their use in deriving sediment accumulation rates and (210)Pb excess inventories for three sediment cores collected from the Barents Sea. (210)Pb activities derived by alpha and gamma methods are shown to agree within counting error and there is also good agreement in the derived sediment accumulation rates. The inherent compatibility of analytical results based on alpha or gamma techniques is established.     

A laboratory technique for investigation of diffusion and transformation of volatile organic compounds in low permeability media

A laboratory diffusion cell technique that permits spatial and temporal estimates of porewater concentrations over short intervals suitable for estimation of effective diffusion coefficients (De) and degradation rate constants (k) of volatile organic compounds (VOCs) in saturated low permeability media is presented. The diffusion cell is a sealed cylinder containing vapour reservoirs for sampling, including a vapour reservoir source and an array of vapour-filled "mini-boreholes", which are maintained water- and sediment-free by slightly negative porewater pressures. The vapour reservoirs were sampled by Solid Phase Micro-Extraction (SPME), resulting in minimal disturbance to the experimental system. Porewater concentrations are estimated from the measured vapour concentrations. Experiments were conducted using a non-reactive medium and five VOCs with a range in partitioning properties. Calibration experiments showed that equilibrium partition coefficients could be used for calculating concentrations in the vapour reservoir source from concentrations in the SPME coating after a 1-min microextraction and that the reservoir concentration was insignificantly affected by sampling. However, equilibrium was not reached during the one-min extraction of the boreholes; the microextraction reduced the borehole vapour concentrations, leading to diffusion of VOCs from porewater into the vapour-filled borehole. Thus, empirical partitioning coefficients were required for the determination of porewater VOC concentrations. The experimental data and numerical modelling indicate masses extracted by SPME extraction are relatively small, with minimal perturbation on processes studied in diffusion experiments. This technique shows promise for laboratory investigation of diffusion and transformation processes in low permeability media.     

An application of the theory of kinematics of mixing to the study of tropospheric dispersion

The most common technique used for numerical simulations of tracer mixing is that of the numerical solution of the advection–diffusion equation with the unresolved fluxes parameterized using the similarity theory. Despite correct predictions of the overall directions of transport, models based on a numerical solution of the advection–diffusion equation lack sufficient accuracy to correctly reproduce the coupling of mixing with small scale processes which are sensitive to the microstructure of the tracer distribution. The objective of this paper is to revisit the basic formalism employed in numerical models used to investigate atmospheric tracers. The main mathematical method proposed here is the theory of kinematics of mixing which could be applied effectively for simulations of atmospheric transport processes. At the beginning of the paper, we introduce simple mathematical transformations in order to demonstrate how complex topological structures are created by mixing processes. These idealistic flow systems are essential to explain transport properties of much more complex three-dimensional geophysical flows. An example of the application of the kinematics of mixing to the analysis of tracer transport on a planetary scale is presented in the following sections. The complex filamentary structures simulated in the numerical experiment are evaluated using some commonly applied statistical measures in order to compare the results with the data published in the literature. The results of the experiment are also analysed with the help of simple conceptual models of fluid filaments. The microstructure of the tracer distribution introduced in the paper is essential to increase our understanding of atmospheric transport and to develop more realistic parameterizations of small-scale mixing. The presented results could also be used to improve calculations of the coupling between microphysical processes and tracer mixing.     

Uncertainty analysis of emission estimates in the RAINS integrated assessment model

Uncertainty is a critical issue for all models that attempt to quantify the necessary emission reductions that are required to meet environmental quality targets. This paper discusses a methodology specifically developed to analyse the uncertainties in the emission estimates with the regional air pollution information and simulation (RAINS) integrated assessment model, considering the uncertainties in the model parameters themselves. Overall, it was found that a typical range of uncertainties for modeled national emissions of sulfur dioxide, nitrogen oxides and ammonia in Europe lies between 10 and 30%. In general, the uncertainties are strongly dependent on the potential for error compensation. This compensation potential is larger (and uncertainties are smaller) if calculated emissions are composed of a larger number of equal-sized source categories, where the errors in input parameters are not correlated with each other. Thus, estimates of the national total emissions are generally more certain than estimates of sectoral emissions. A sensitivity analysis with respect to the uncertainty in input parameters showed that the actual uncertainties are critically influenced by the specific situation (pollutant, year, country). However, the emission factor is an important contributor to the uncertainty in estimates of historical emissions, while uncertainty in the activity data dominates the future estimates.     

Water quality index applied to rivers in the Vistula river basin in Poland

Summary A new method of a water quality index has been proposed. The unit indices were determined from the values of individual parameters using continuous functions. The base for such functions were the four water quality classes used in Poland. The summarized WQI is the square root of the harmonic mean of squares of unit indices. Using this mean we have eliminated the use of weights of parameters. Parameters are divided into basic parameters (7) and other additional parameters (19). The additional parameter is considered only if its unit index is lower than WQI from basic parameters. For many measurements at one point the guaranteed WQI has been calculated. The points of WQI were connected and the curves of WQI along the river were obtained.A method of WQI calculating and preparation of WQI curves has been shown using as an example the Pilica river in Poland. The WQI was then calculated for 31 rivers in the Vistula river basin by measuring points.     

Leaf surface compounds of the potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis>) and their influence on Colorado potato beetle (<Emphasis Type="Italic">Leptinotarsa decemlineata</Emphasis>) feeding

Summary.  The sampling behavior of the Colorado potato beetle Leptinotarsa decemlineata Say (CPB) involves examination of the surface of potato leaves. It has been suggested that leaf surface compounds (volatiles and cuticular waxes) may be involved in host-plant recognition, acceptance or discrimination. Here we report on the effect of leaf surface extracts of six Polish commercial potato varieties on CPB feeding. We tested the influence of potato leaf surface extracts on CPB adult and larval feeding, then separated the extracts with HPLC, and finally tested the effect of the HPLC-separated fractions on CPB feeding. The bioassays were performed using potato leaf discs deprived of their original surface compounds. Applied to test discs at concentrations ten times higher than natural (10 leaf area equivalent), the extracts deterred CPB adults and larvae from feeding. HPLC-separated fractions composed of alkanes, sesquiterpene hydrocarbons, wax esters, benzoic acid esters, fatty acid methyl, ethyl, isopropyl and phenylethyl esters, aldehydes, ketones, methyl ketones, fatty acids, primary alcohols, β-amyrin and sterols did not affect adult CPB feeding. Similarly, alkanes, sesquiterpene hydrocarbons, wax esters, methyl ketones, sesquiterpene alcohols and secondary alcohols had no effect on larval CPB feeding. The sterol fraction (cholesterol, β-sitosterol and stigmasterol) acted as a phagostimulant to CPB larvae. We isolated a fraction demonstrating a phagodeterrent effect on CPB adults and larvae. The qualitative composition of the deterrent fraction was quite similar in all potato extracts, but there were quantitative differences between the varieties. Much further work is needed to identify the compounds that can produce the deterrent effect.     

Historical record of mercury contamination in sediments from the Babeni Reservoir in the Olt River,Romania

Background, aim and scope

Mercury (Hg) is a ubiquitous and hazardous contaminant in the aquatic environment showing a strong biomagnification effect along the food chain. The most common transfer path of Hg to humans is contaminated fish consumption. In severely exposed humans, Hg poisoning may lead to damage in the central nervous system. Thus, it is important to examine current and past contamination levels of Hg in aquatic milieu. The Olt River is the largest Romanian tributary of the Danube River. The use of Hg as an electrode in a chlor-alkali plant contributed to the contamination of the aquatic environment in the Rm Valcea region. The purpose of this study was to compare the current state of Hg contamination with the past contamination using a historical record obtained from a dated sediment core from one of the Olt River reservoirs (Babeni) located downstream from the chlor-alkali plant. To our knowledge, no published data on Hg contamination in this region are available. The Babeni Reservoir was selected for this study because it is situated downstream from the chlor-alkali plant, whilst the other reservoirs only retain the pollutants coming from the upstream part of the watershed. Preliminary analyses (unpublished) showed high Hg concentrations in the surface sediment of the Babeni Reservoir. One core was taken in the upstream Valcea Reservoir to provide a local background level of Hg concentrations in sediments.

Results and discussion

Sediment texture was uniform in the cores from both reservoirs. Laminated sediment structure, without any obvious discontinuities, was observed. Hg concentrations in the sediment core from the Valcea Reservoir were low and constant (0.01–0.08 mg/kg). In Babeni Reservoir sediments, Hg concentrations were very high in the deeper core section (up to 45 mg/kg in the longest core) and decreased to lower concentrations toward the top of the cores (1.3–2.4 mg/kg). This decrease probably reflects technological progress in control of emissions from the Hg-cell-based chlor-alkali industry. Two strong peaks could be distinguished in older sediments. The mean rate of sedimentation (5.9 cm/year) was calculated from the depth of the ¹³⁷Cs Chernobyl peak. This was in good agreement with the sedimentation rate estimated at this site from a bathymetric study. Assuming a constant sedimentation rate, the two Hg peaks would reflect two contamination events in 1987 and 1991, respectively. However, it is also possible that the two peaks belong to the same contamination event in 1987 but were separated by a sediment layer richer in sand and silt. This layer had a low Hg concentration, which can be interpreted as a mass deposition event related to a major flood bringing Hg-free sediments.

Conclusions

Whilst the chlor-alkali plant partly switched to a cleaner technology in 1999, no obvious decrease of Hg concentrations was observed in recent decade. Results from the sediment core reflected the historical trend of Hg release from the chlor-alkali plant, revealed important contamination episodes and confirmed a legacy of contamination of Hg in recent sediments even if the concentrations of Hg decreased toward the surface due to a more efficient emission control.

Recommendations and perspectives

Although the Hg concentrations in Babeni Reservoir sediments were extremely high in the late eighties and they remain one order of magnitude higher in the surface sediments than in sediments from the upstream reservoir, little is known about the transfer of Hg to the biota and human population. Our initial measurements indicate the presence of monomethyl-Hg (MMHg) in pore water, but further studies are necessary to evaluate fluxes of MMHg at the sediment–water interface. Samples of fish and hair from various groups of the local population were recently collected to evaluate the potential hazard of Hg contamination to human health in the Rm Valcea region.