Elemental mercury (Hg0) is a metal with a number of atypical properties, which has resulted in its use in myriad anthropogenic processes. However, these same properties have also led to severe local subsurface contamination at many places where it has been used. As such, we studied the influence of various parameters on Hg(II) sorption onto pyrite (pH, time, Hg(II) concentration), a potential subsurface reactive barrier. Batch sorption studies revealed that total Hg(II) removal increases with both pH and time. X-ray absorption spectroscopy analysis showed that a transformation in the coordination environment at low pH occurred during aging over 2 weeks, to form an ordered monolayer of monodentate Hg–Cl complexes on pyrite. In column studies packed with pure quartz sand, the transport of Hg(II) was significantly retarded by the presence of a thin pyrite-sand reactive barrier, although dissolved oxygen inhibited Hg(II) sorption onto pyrite in the column. Pyrite may be an effective subsurface reactive barrier for Hg in groundwater.

We studied the effectiveness of remediation on microbial endpoints, namely microbial biomass and activity, microbial and plant species richness, of an As-contaminated mine spoil, amended with compost (C) alone and in combination with beringite (B) or zerovalent iron grit (Z), to increase organic matter content and reduce trace elements mobility, and to allow Holcus lanatus and Pinus pinaster growth. Untreated spoil showed the lowest microbial biomass and activity and hydrolase activities, and H. lanatus as sole plant species, whereas the presented aided phytostabilisation option, especially CBZ treatment, significantly increased microbial biomass and activity and allowed colonisation by several plant species, comparable to those of an uncontaminated sandy soil. Microbial species richness was only increased in spoils amended with C alone. No clear correlation occurred between trace element mobility and microbial parameters and plant species richness. Our results indicate that the choice of indicators of soil remediation practices is a bottleneck. Organo-mineral amendment and revegetation of a gold mine spoil increased microbial activity but did not increase microbial species richness.

In winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) rotation system in the North China Plain, maize roots do not extend beyond 1.2 m in the vertical soil profile, but wheat roots can reach up to 2.0 m. Increases in soil nitrate content at maize harvest and significant reductions after winter wheat harvest were observed in the 1.4-2.0 m depth under field conditions. The recovery of 15N isotope (calcium nitrate) from various (1.0, 1.2, 1.4, 1.6, 1.8 and 2.0 m) soil depths showed that deep-rooting winter wheat could use soil nitrate up to the 2.0 m depth. This accounted partially, for the reduced nitrate in the 1.4-2.0 m depth of the soil after harvest of wheat in the rotation system. Deep-rooted wheat can recycle nitrate leached from maize root zone in winter wheat-summer maize rotation system.

In the San Bernardino Mountains of southern California, ozone (O(3)) concentrations have been elevated since the 1950s with peaks reaching 600 ppb and summer seasonal averages >100 ppb in the 1970s. During that period increased mortality of ponderosa and Jeffrey pines occurred. Between the late 1970s and late1990s, O(3) concentrations decreased with peaks approximately 180 ppb and approximately 60 ppb seasonal averages. However, since the late 1990s concentrations have not changed. Monitoring during summers of 2002-2006 showed that O(3) concentrations (2-week averages) for individual years were much higher in western sites (58-69 ppb) than eastern sites (44-50 ppb). Potential O(3) phytotoxicity measured as various exposure indices was very high, reaching SUM00 - 173.5 ppmh, SUM60 - 112.7 ppmh, W126 - 98.3 ppmh, and AOT40 - 75 ppmh, representing the highest values reported for mountain areas in North America and Europe.

Concentrations of polychlorinated biphenyls (PCBs) in blubber of female common dolphins and harbour porpoises from the Atlantic coast of Europe were frequently above the threshold at which effects on reproduction could be expected, in 40% and 47% of cases respectively. This rose to 74% for porpoises from the Southern North Sea. PCB concentrations were also high in southern North Sea fish. The average pregnancy rate recorded in porpoises (42%) in the study area was lower than in the western Atlantic but that in common dolphins (25%) was similar to that of the western Atlantic population. Porpoises that died from disease or parasitic infection had higher concentrations of persistent organic pollutants (POPs) than animals dying from other causes. Few of the common dolphins sampled had died from disease or parasitic infection. POP profiles in common dolphin blubber were related to individual feeding history while those in porpoises were more strongly related to condition. (C) 2007 Elsevier Ltd. All rights reserved.

Ambient concentrations, congener patterns and multi-media distribution of PCDD/Fs and PCBs were determined in air, water, sediment and mussels in a semi-enclosed marine ecosystem (Thau lagoon, France). Sigma 2,3,7,8-PCDD/F and Sigma 7ICES PCB air concentrations (0.2-1.4 and 31-57 pg m(-3), respectively) were typical of rural areas. Concentrations in the water column were very low for PCDD/Fs (163-476 fg L-1) and low for PCBs (138-708 pg L-1). PCDD/F and PCB concentrations found in surface sediment (0.15-1.6 and 2.5-33 ng g(-1) d.w., respectively) and mussel (13-21 pg g(-1) d.w. and 10-39 ng g(-1) d.w., respectively) were medium levels. PCDD/F congener patterns observed in air, water particulate phase and sediments were similar suggesting direct coupling among these compartments and atmospheric inputs of PCDD/Fs into the lagoon. Conversely, for the same set of samples, similar patterns were not observed for PCBs in the mentioned compartments. (C) 2007 Elsevier Ltd. All rights reserved.

Uptake of waterborne Cd, Co, Mn and Zn was determined in laboratory experiments using radiotracer techniques (Cd-109, Co-57, Mn-54 and Zn-65). Labelled Zn was mainly accumulated in the digestive gland (65%) and Co in kidneys (81%); Cd and Mn were similarly distributed in digestive gland and gills. In a complementary field study, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn were analysed in scallops collected at two stations showing different contamination levels. Digestive gland and kidneys displayed the highest concentrations. Ag, As, Cd, and Fe differed in soft tissues from the two stations, suggesting that Comptopallium radula could be a valuable local biomonitor species for these elements. Low Mn and Zn concentrations found in kidneys suggest that their content in calcium-phosphate concretions differs from the other pectinids. Preliminary risk considerations suggest that As would be the only element potentially leading to exposure of concern for seafood consumers. (c) 2007 Elsevier Ltd. All rights reserved.

The suprabenthos comprises all bottom-dependent animals, mainly crustaceans (including decapods and peracarids), which perform - with varying amplitude, intensity and regularity - seasonal or daily vertical migrations above the sea floor. The presence of organisms in the Benthic Boundary Layer is determined by two general factors: (1) organism behaviour, which depends on the light penetration in the water column and (2) boundary-layer hydrodynamics. In the coastal zone of the eastern English Channel, during the spring Phaeocystis bloom, the presence of gelatinous colonies modifies the penetration of light in the water column, which may seriously affect the abundance and/or the behaviour of the suprabenthos community. To clarify this point, 19 suprabenthic hauls were taken with a modified Macer-GIROQ sledge both during the day and during the night, from March to June 2002 (i.e., before, during and after the bloom). Two sites, located in the coastal and offshore areas of the Ophelia medium sand macrobenthic community were investigated. The bloom had no effect on species richness and abundance in either site. However, the diel migrations of some dominant species - such as the cumaceans Pseudocuma longicornis and Pseudoctuma similis, the mysid Gastrosaccus spinifer and the amphipod Stenothoe marina - were modified. During the bloom, diurnal and nocturnal suprabenthic abundances were similar, and in the absence of bloom, species remained benthic during the day. The permanent presence of suprabenthic species in the Benthic Boundary Layer could have a consequence on their predation by fish (mainly juveniles which preferentially consume small crustaceans in their diet), unless fish behaviour and predation efficiency - especially for visual predators - are also disturbed by changes in light intensity. (c) 2007 Elsevier Ltd. All rights reserved.

International audience | Biofilm development in wastewater treatment system by soil infiltration is often mentioned for its participation to purification efficiency and clogging zone formation. It appears necessary to understand its evolution in order to better control the operation of these systems. The objective of this study was to improve knowledge about the temporal evolution of the biofilm structure in the first centimetres of infiltration system. For this purpose, metabolic fingerprints by Biolog EcoPlate (TM) and molecular fingerprints by Ribosomal Intergenic Spacer Analysis (RISA) were carried out on sand, septic effluent and treated effluent samples from two experimental reactors supplied with different hydraulic loads collected at different times. The metabolic capabilities of sand microflora decreased in time. In the same way, molecular structure of the biofilm community changed and converged to similar structure in time. Principal components analysis on RISA gel revealed a ''buffering effect'' of the sand filter on the genetic structure of the bacterial community from treated effluent. The kinetics of evolution of the both metabolic and genetic fingerprints showed a reduction of the metabolic and genetic potentials of septic and treated effluents for the same times. The population dynamic within the biofilms appears interesting evidence in the comprehension of the operation of the treatment systems.

International audience | Biofilm development in wastewater treatment system by soil infiltration is often mentioned for its participation to purification efficiency and clogging zone formation. It appears necessary to understand its evolution in order to better control the operation of these systems. The objective of this study was to improve knowledge about the temporal evolution of the biofilm structure in the first centimetres of infiltration system. For this purpose, metabolic fingerprints by Biolog EcoPlate (TM) and molecular fingerprints by Ribosomal Intergenic Spacer Analysis (RISA) were carried out on sand, septic effluent and treated effluent samples from two experimental reactors supplied with different hydraulic loads collected at different times. The metabolic capabilities of sand microflora decreased in time. In the same way, molecular structure of the biofilm community changed and converged to similar structure in time. Principal components analysis on RISA gel revealed a ''buffering effect'' of the sand filter on the genetic structure of the bacterial community from treated effluent. The kinetics of evolution of the both metabolic and genetic fingerprints showed a reduction of the metabolic and genetic potentials of septic and treated effluents for the same times. The population dynamic within the biofilms appears interesting evidence in the comprehension of the operation of the treatment systems.