International audience | Les changements de productivité des forêts ont été étudiés intensément à partir des années 1990, à la suite des événements relatifs au dépérissement des forêts européennes. Dans cette contribution, on analyse les problèmes méthodologiques soulevés par ce type d'étude, les sources de données disponibles pour l'analyse, et les éléments de diagnostic acquis sur plusieurs espèces forestières du territoire français. Les implications pour le cadre théorique qui prévalait dans les années 1980 concernant la productivité des peuplements forestiers sont enfin discutées. problèmes méthodologiques, sources de données, cadre théorique, éléments du diagnostic

[Departement_IRSTEA]MA [TR1_IRSTEA]TED / EPURE | With the aim of improving the WSP effluent quality, different types of Vertical Flow Constructed Wetlands and Intermittent Sand Filters were tested in a pilot plant in Aurignac (France). The effectiveness of each design for upgrading the effluent from the pond was studied over a period of two years. Physicochemical parameters were monitored by taking composite samples over 24 hours and weekly punctual samples. The hydraulic behaviour of the filters was studied by tracing methods (using NaCl) and monitoring the infiltration rate. This paper describes the influence of: (a) the characteristics of the medium (presence of Phragmites, depth, type of sand), (b) feeding modes and (c) the presence of an algae clogging layer on the performance of the beds. Overall, both Vertical Flow Constructed Wetlands and Intermittent Sand Filters are appropriate systems for retaining algae, completing organic matter degradation and nitrifying the WSP influent. The design and operation bases, the hydraulic behavior and the advantages and disadvantages (in terms of efficiency and maintenance) of the different configurations were determined.

Human transport by land, sea and air has increased exponentially through time in intensity, paralleling rises in population, prosperity and rates of technological change. Transport has considerable ecological effects, many of them detrimental to environmental sustainability. This volume brings together international experts from a variety of disciplines to review the ecological effects and their causes in terms of road, rail, ship and aircraft transport. The contributors have different attitudes and agendas. Some are ecologists, some planners, others social scientists. Focus ranges from identification of threats and amelioration of damaging effects through to future design of transport systems to minimize environmental degradation. Some chapters consider restricted areas of the globe; others the globe itself. Views encompass deep pessimism and cautious optimism. Uniquely, the volume considers transport effects in all environments. This is the first book that attempts to discuss the relationship between human transport and all ecosystems. It appeals not only to the specialist environmentalist by picking out novel topics, but also to anyone involved in transport issues as it tackles the issues from an historical perspective, encompassing the past, present and future of the effects of human transport.

Lithological and granulometric investigations of the surface and short core sediments in L. Martiska (northeastern Estonia) showed that variations in the grain-size parameters and LOI content were influenced by the changes in deposition conditions during the regression and transgression phases monitored in the lake since the 1960s. During the regression and transgression phases displacement of the erosion-transport-accumulation zones in the lake took place depending on the bottom topography. The water level fluctuations are especially clearly reflected in grain-size variations in cores from peripherial area.

A major focus of palynological research has been to assess the various pathways by which pollen is delivered to sedimentary archives. In open lake systems, the contribution of streamborne pollen to lake sediments is thought to be highly significant. Despite this, little research has attempted to identify changes in the pollen record that might be attributed to changing sediment pathways rather than to changes in vegetation. This research aims to partially redress this gap by examining a dated pollen sequence from Kyre Pool, Worcestershire, England. The results presented in this paper suggest that some changes in sediment source, as determined by a fingerprinting approach, can influence the pollen record reconstructed from a lake sediment profile.

The overall objective of this research was to develop a reliable, robust, and maintenance-free passive system for biological denitrification in on-site wastewater treatment systems. The process relies on sulfur oxidizing denitrifying bacteria in upflow packed bioreactors. Since this process consumes alkalinity, it is necessary to add a solid-phase buffer that can scavenge the H⁺ as it is generated by the biologically-mediated reaction and arrest the drop in the pH value. This study investigated the use of limestone, marble chips and crushed oyster shell as solid-phase buffers that provide alkalinity. Two bench-scale upflow column reactors and two field-scale bioreactors were constructed and packed with sulfur pellets and an alkalinity source. The pilot scale bioreactors (~200 L each) were installed at the Massachusetts Alternative Septic System Test Center (MASSTC) in Sandwich, MA. The pilot-scale bioreactors performed better when oyster shell was used as the solid-phase buffer vis-à-vis marble chips. In both (pilot-scale and laboratory-scale) systems, denitrification rates were high with the effluent NO₃ - --N concentration consistently below 8 mg/L.

Cohesive sediments besides their typical heterogeneity are characterised by structural discontinuity. Particularly, organic consolidated muds are a good example of sediments that consist of vast aggregates, pore water and gaseous products. The texture of a cohesive sediment bed is a result of a number of mutually affecting factors, such as deposition history, mineral and organic composition, kind of biota and oxygen uptake. The presented work attempts to quantify the effect of sediment physical properties and sediments structure on the sediment erosion potential, considering incipient motion and erosion rate. This quantification is made on the basis of comparative testing of both unremoulded and remoulded samples of a river mud. Due attention is paid to sediment handling to preserve the delicate structure of the sediment for the laboratory experiments. Mud with two degrees of consolidation has been examined in a tilting flume under different flow situations. The test results show a typical increase of erosion strength with dry matter concentration of the mud. It has also been found that the structural properties increase the erosion strength for the less consolidated mud. An opposite effect has been recorded for a more consolidated deposit. As a consequence, due to the sediment structure, the original beds differ much less in erosion resistance in relation to the dry mass concentration than their disturbed analogues. Finally, the erosion resistance of the examined mud is compared with data from the literature.

The Erzgebirge, part of the so-called former “Black Triangle”, used to represent the strongest regional air pollution of Central Europe. To test the hypothesis of deposition enhancement with height, an altitudinal gradient along a N-S transect from the Elbe river lowlands to the Erzgebirge summit was chosen to investigate chemical composition, elevation-related variability, temporal changes, and seasonal patterns of ion concentrations from 1993 to 2002. The following questions were to be answered: (1) Which role does orography play on the composition of precipitation?, (2) Does fog occurrence overrule the orographic influence?, (3) Are there changes in the past 10 years, and if so, why?, (4) Do relevant seasonal changes occur and why? Air streams from westerly and to a lesser degree south-easterly directions prevail. The average precipitation was ion-poor (23 μS cm-¹ and acidic (pH 4.5). Sulphate still was the dominant anion (52.3-59.9 μeq L-¹, while NH⁺ ₄ determined the cations (41.9-62.2 μeq L-¹. Ion concentrations decreased with altitude to about 735 m a.s.l. and subsequently increased. The seeder-feeder effect largely explains the chemical composition of precipitation; enhanced in winter through snow crystals. Sub-cloud scavenging does not explain the observed patterns. Fog occurrence enhanced the observed effects at higher altitudes. Deposition amounts doubled from the lowlands to the Erzgebirge summit. From 1993 to 2002, acidity decreased by about 50%, mainly due to reduced SO₂ -emissions.