Some of the greatest forest health impacts in North America are caused by invasive forest insects and pathogens (e.g., emerald ash borer and sudden oak death in the US), by severe outbreaks of native pests (e.g., mountain pine beetle in Canada), and fires exacerbated by changing climate. Ozone and N and S pollutants continue to impact the health of forests in several regions of North America. Long-term monitoring of forest health indicators has facilitated the assessment of forest health and sustainability in North America. By linking a nationwide network of forest health plots with the more extensive forest inventory, forest health experts in the US have evaluated current trends for major forest health indicators and developed assessments of future risks. Canada and Mexico currently lack nationwide networks of forest health plots. Development and expansion of these networks is critical to effective assessment of future forest health impacts.

Upcoming decades will experience increasing atmospheric CO2 and likely enhanced O3 exposure which represents a risk for the carbon sink strength of forests, so that the need for cause-effect related O3 risk assessment increases. Although assessment will gain in reliability on an O3 uptake basis, risk is codetermined by the effective dose, i.e. the plant's sensitivity per O3 uptake. Recent progress in research on the molecular and metabolic control of the effective O3 dose is reported along with advances in empirically assessing O3 uptake at the whole-tree and stand level. Knowledge on both O3 uptake and effective dose (measures of stress avoidance and tolerance, respectively) needs to be understood mechanistically and linked as a pre-requisite before practical use of process-based O3 risk assessment can be implemented. To this end, perspectives are derived for validating and promoting new O3 fluxbased modelling tools.

A detailed investigation was conducted to understand the contamination characteristics of a selected set of potentially toxic metals in Shanghai. The amount of Pb, Zn, Cu, Cr, Cd and Ni were determined from 273 soil/dust samples collected within urban area. The results indicated that concentration of all metals except Ni in soils was significant, and metal pollution was even severer in roadside dust. A series of metal spatial distribution maps were created through geostatistical analysis, and the pollution hotspots tended to associate with city core area, major road junctions, and the regions close to industrial zones. In attempt of identifying the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Pb, Zn and Cu mainly originated from traffic contaminants; soil Ni was associated with natural concentration; Cd largely came from point-sourced industrial pollution; and Cr, Ni in dust were mainly related to atmospheric deposition. Human activities have led to high accumulation of potentially toxic metals in urban soils and roadside dust of Shanghai.

We present a user-friendly tool for footprint calculations of flux measurements in the surface layer. The calculations are based on the analytical footprint model by Kormann, R. and Meixner, F.X. [2001. An analytical footprint model for Non-neutral Stratification. Boundary-Layer Meteorology 99, 207-224]. The footprint density function of a flux sensor is determined using readily available data from standard eddy covariance measurements. This footprint density function is integrated over defined surface areas given as quadrangular polygons representing e.g. agricultural fields. We illustrate the use and performance of the tool by applying it to CO2 flux measurements with three eddy covariance system at the Swiss CarboEurope grassland site. Two flux towers were positioned in the centre of two neighbouring fields, respectively, that showed a very different CO2 flux during the study period. The third tower was located near the border of the two fields and was frequently influenced by both fields to a similar degree. The calculated footprint fractions were used to simulate the latter flux from the other two systems. The measured and simulated fluxes showed a good agreement and thus support the reliability of the footprint calculation. The presented simple footprint tool can be used as a routine quality check for flux monitoring stations influenced by surface areas with varying vegetation covers and/or land-use. A simple tool for operational footprint calculations is presented and its reliability is assessed using CO2 flux measurements in a patchy agricultural landscape.

Solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS) was used to analyze two triazine (atrazine and simazine) and three chloroacetamide herbicides (acetochlor, alachlor, and metolachlor) in water samples from a midwest US agricultural drainage ditch for two growing seasons. The effects of salt concentration, sample volume, extraction time, and injection time on extraction efficiency using a 100-μm polydimethylsiloxane-coated fiber were investigated. By optimizing these parameters, ditch water detection limits of 0.5 μg L-1 simazine and 0.25 μg L-1 atrazine, acetochlor, alachlor, and metolachlor were achieved. The optimum salt concentration was found to be 83% NaCl, while sample volume (10 or 20 mL) negligibly affected analyte peak areas. The optimum extraction time was 40 min, and the optimum injection time was 15 min. Results indicated that atrazine levels in the ditch water exceeded the US maximum contaminant level for drinking water 12% of the time, and atrazine was the most frequently detected among studied analytes. Solid-phase microextraction methods were successfully developed to quantify low levels of herbicides in tile-fed drain water by gas chromatography-mass spectrometry.

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

To investigate the consequences of acidification and metal accumulation on the biology of aquatic bryophytes, the acid-tolerant liverwort Scapania undulata (L.) Dum. and the acid-sensitive moss Rhynchostegium riparioides (Hedw.) Cardot were transplanted from one stream to two other streams of differing acidity (pH 5.20 and 6.38). The bryophytes were collected in a circumneutral (pH 6.57) stream in the Vosges Mountains. Metal accumulation was semiquantitatively measured in shoots by energy dispersive TEM X-ray spectroscopy (EDXS). After 1 month, the two species remained green without alteration signs. Although no marked ultrastructural damage was observed in either species, some cells seemed to be necrotic, with flattened chloroplasts, in R. riparioides. Lipid droplet accumulation was observed in some leaf cells of S.undulata when transplanted to the most acidic stream. Metal was mostly localised in the cell wall, and was only sometimes detected in small vacuoles. Under acidic conditions, R. riparioides showed the highest relative amount of Al and the lowest amount of Fe, whereas the acid-tolerant bryophyte species S. undulata contained more Fe and less Al. The capability to limit the uptake of metals into the cytoplasm varies according to the bryophyte species. This could be an explanation of the tolerance of S. undulata to acidification. | International audience

Remediation and management of contaminated sediments and dredged material is often difficult due to the complex mixtures of chemical substances that usually impact the sediments. The selection of the best option that leads to the sustainable management of the sediments of a site is not an easy task, and it should be based on the integration of technical, economic, social and environmental criteria. In this paper, an overview of the main alternatives for the management of contaminated sediments and dredged material is presented. This work highlights the wide variety of techniques and treatments that can be applied, including no action (i.e. monitored natural recovery), in-situ capping, in-situ treatments, ex-situ treatments or confined disposal. The utilisation of contaminated dredged material for a beneficial use, directly or after treatment, should be considered as its preferred final destination. Therefore, special emphasis has been given in this study to the presentation of possible beneficial uses of dredged material. The results of our research group, which are summarised in this paper, about the use of contaminated sediments as alternative raw materials in the manufacture of traditional clay-based ceramics, can serve as an example of beneficial uses that lead to marketable products. | This work was conducted under the framework of the Spanish Ministry of Education and Science Projects CTM2005-07282-C03/3 and CTM 2006-07960. M. Alvarez-Guerra was funded by the Spanish Ministry of Education and Science by means of an F.P.U. fellowship.