The canopy budget model simulates the interaction of major ions within forest canopies based on throughfall and precipitation measurements. The model has been used for estimating dry deposition and canopy exchange fluxes in a wide range of forest ecosystems, but different approaches have been reported. We give an overview of model variations with respect to the time step, type of open-field precipitation data, and tracer ion, and discuss the strengths and weaknesses of different assumptions on ion exchange within forest canopies. To examine the effect of model assumptions on the calculated fluxes, nine approaches were applied to data from two deciduous forest plots located in regions with contrasting atmospheric deposition, i.e. a beech (Fagus sylvatica L.) plot in Belgium and a mixed sugar maple (Acer saccharum Marsh.) plot in Quebec.For both forest plots, a semi-annual time step in the model gave similar results as an annual time step. Na⁺ was found to be more suitable as a tracer ion in the filtering approach than Cl⁻ or [Formula: see text]. Using bulk instead of wet-only precipitation underestimated the potentially acidifying deposition. To compute canopy uptake of [Formula: see text] and H⁺, ion exchange with K⁺, Ca²⁺, and Mg²⁺ as well as simultaneous cation and anion leaching should be considered. Different equations to allocate [Formula: see text] vs H⁺ uptake had most effect on the estimated fluxes of the cation that was less important at a plot. More research is needed on the relative uptake efficiency of H⁺, [Formula: see text], and [Formula: see text] for varying tree species and environmental conditions.

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.

Xenobiotic compounds are widely used in several industries; hence they frequently appear in industrial wastewaters. It is a well-known fact that even the discharge of conventionally treated wastewater may have adverse effects on the receiving water environment. Turkey, a developing EU applicant country, has many industrial sectors producing large amounts of xenobiotic-containing wastewaters. The problem is only enlarged by the lack of monitoring of these substances due to the deficiencies associated with their analysis and detection. Thus, studies in Turkey are based on the use of some collective parameters as a substitute for the xenobiotic itself. Biological, physicochemical, and integrated treatment technologies have been investigated for the removal and/or minimization of the possible adverse effects of xenobiotics in industrial wastewaters. In this respect, this paper provides an overview of the studies conducted on xenobiotic-containing wastewaters from specific industries in Turkey. Although the studies add invaluable information to the scientific background on the subject, new research on the exact biochemical mechanisms of xenobiotic biodegradation will further extend our understanding for improving treatment.

The major objective of this paper is to provide insights to sources and sinks of nitrous acid in urban areas, and their seasonal dependency on meteorology, photochemistry and long range transport. With this aim, nitrous acid (HONO) mixing ratios and other compounds were measured in Ashdod (south of Tel Aviv, Israel), a typical Mediterranean urban area. Statistical data analysis revealed the expected correlation between HONO and nitrogen oxides during the autumn campaign when HONO sources appeared to be traffic-, harbor-, and industry-related. Conversely, during summer HONO and NO₂ were no longer correlated: NO₂ at nighttime was probably deposited onto surfaces, soil and plants, whereas HONO at daytime was likely destroyed photolytically contributing to the OH concentration. Photolysis was expected to be the dominant HONO sink at daytime, especially during the summer period. Using modeled photolytical HONO lifetimes we estimate the magnitude of heterogeneous and/or organic electron transfer source reactions of HONO as 6-8 ppbv/h.

In the daily and final landfill cover barrier system, the hydraulic properties of compacted soil liners and the strength of soil can be adversely affected by desiccation cracking, resulting in the loss of effectiveness and integrity of the containment system as a barrier. Recently, there is an interest of using fiber additive to overcome the desiccation cracking problem. In this study, the desiccation crack test was conducted to investigate the effect of fiber additive on suppressing desiccation cracks in compacted Akaboku soils. Polypropylene (C₃H₆) fiber was used as an additive material for soil sample. The percentages of fiber used were varied as 0.0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0% and 1.2% (by dry weight of samples). The soil specimens were compacted under the conditions of maximum dry density and optimum water content. The surficial cracking area was measured to determine the crack intensity factor (CIF) of the soil samples. The desiccation crack test results indicated that the percentage of volume change of the compacted soil specimen decreased with addition of fiber. The change in the soil surface area decreased with increasing in the fiber content (FC), and consequently, the volumetric shrinkage strain decreased. The CIF for the soil without fiber (FC = 0.0%) were significantly higher than the soil with fiber additive. The CIF of soil at FC = 0.0% decreased from 2.75% to 0.6% for the soil at FC = 0.2%. It was also found that the maximum crack depth reaches almost 50% of the thickness of the soil without fiber additive. This study suggests the potential application of the fiber additives to soils as an available method to suppress desiccation cracks encountered in landfill cover barriers.

Toxaphene contamination of minke whales (Balaenoptera acutorostrata) from North Atlantic waters was examined for the first time. Total toxaphene and SumCHB (sum of 11 chlorobornanes) concentrations in blubber samples ranged from 170 ± 110 and 41 ± 39 ng/g lipid weight (l.w.) for female minke whales from southeastern Greenland to 5800 ± 4100 and 1100 ± 780 ng/g l.w. for males from the North Sea, respectively. Very large variations in toxaphene concentrations among sampling areas were observed suggesting a spatial segregation of minke whales. However, much of the apparent geographical discrimination was explained by the seasonal fluctuation of animal fat mass. Patterns of CHBs in males revealed that recalcitrant CHBs were in higher proportions in animals from the more easterly areas than in animals from the more westerly areas. This trend may be influenced by the predominance of the US, over the European, input of toxaphene to North Atlantic waters.

International audience | Water-use efficiency is an important functional trait that can be defined at very different temporal and spatial scales in trees as well as in crops. Transpiration efficiency (TE) is usually defined at tree or even stand level as the ratio between transpired water and accumulated biomass. Intrinsic water-use efficiency (Wi) is defined at instant leaf scale as the ratio net CO2 assimilation rate vs. stomatal conductance (A/gs). Wi is usually estimated by isotopic discrimination against 13CO2 during photosynthesis (Delta). Delta can be measured at the instantaneous time-scale on-line with new spectroscopic techniques, but is usually recorded from the isotopic composition of different metabolic pools (bulk leaf matter, soluble sugars, cellulose in leaves and wood). Delta is a plastic trait and is therefore largely used as an index for short term (interannual) changes in water availability and for climate constraints. Delta is also under tight genetic control in trees like in many other species and shows a large diversity. This was shown for populations from different origins, within populations on ecological clines, and among clones. Furthermore, quantitative genetics approaches identified a few highly significant QTLs for Delta in full-sib offsprings of oaks, maritime pine, chestnut and poplars, and thus identified a small number of genomic regions that are active in the control of Delta. The range of genotypic values identified in these approaches encompasses up to 3-4 ‰, which would translate into 30-50% difference in intrinsic water-use efficiency. Due to technical difficulties, much less evidence is available about the genetic control of Wi and of TE. Moreover, the parameters of the model relating Delta to Wi may also display some degree of genotypic variability, and the suitability of Delta as an index for Wi has been questioned. In this presentation, some evidence will be produced in support for the tight correlation between Delta and Wi in support of the use of Delta as a screening tool for Wi and even TE. Based on the accumulated data demonstrating the large diversity of Wi as well as the tight genetic control over this trait, a few research perspectives will be identified and discussed