D. Ollivon

Origin and distribution of polyaromatic hydrocarbons and polychlorobiphenyls in urban effluents to wastewater treatment plants of the Paris area (France)

Polyaromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs), were investigated in urban effluents to wastewater treatment plants in the Paris area (France), under different meteorological conditions. The Achères plant was considered with special attention because of its particular features. Wastewater PAH concentration level was 6 fold higher than that of PCBs. In March, PCB concentrations did not vary whatever the meteorological conditions whereas, for PAHs, they were markedly higher during rainy episodes. In September, concentrations of both pollutants increased due to rainy weather. The rise was 30 fold stronger for PAHs. Daily fluxes displayed the same trends. This suggests that the contribution of atmospheric wet deposition to wastewater contamination prevails for PCBs. In contrast, PAHs appeared to originate mainly from urban runoff processes.

Exchanges at the sediment-water interface in the river Seine, downstream from Paris

Abstract The exchanges at the sediment-water interface were studied in the river Seine, downstream from Paris. Various species of nitrogen were considered. A budget of exchanges could be established between the sewage treatment plant at Acheres and Poses, 140 km downstream. For each of the three sites studied the sediments were characterized by their granulometry and their particulate organic carbon and particulate nitrogen contents. To quantify the exchanges between the sediments and the water two techniques were used: study of cores interstitial water and of dialysis cells water allow to establish vertical profiles for nitrogen and phosphorus, essential to calculate molecular diffusion; global exchanges at the interface were determined with a benthic bell-jar, whose water was regularly sampled until anoxy is reached. That study allowed the clarification of the exchange kinetics at the sediment-water interface with regards to the sludge deposited in the river from the sewage treatment plant. Denitrification played a minor role while ammonification of organic nitrogen seemed to be partially responsible for the ammoniacal nitrogen concentrations in the interstitial water. A notable release of phosphorus was also observed. The concentration gradients measured in the dialysis cells experiments were used to calculate the exchanges exclusively due to molecular diffusion, while the measurements obtained with benthic bell-jars took into account all the chemical, biological and physical phenomena. Thus the discrepancies found between the values of molecular diffusion and the exchange values obtained with benthic bell-jars were very marked. These last values allowed the establishment of the mean release budgets in the studied area: ammoniacal nitrogen, 13.4 t d −1 ; phosphorus, 3.7 t d −1 .

Fluxes of polycyclic aromatic hydrocarbons in the Seine estuary, France: mass balance and role of atmospheric deposition

Measurements of polycyclic aromatic hydrocarbons (PAHs) were carried out from 2001 to 2003 in various environmental compartments (ambient air, atmospheric deposition, soils, sediments, runoff, and surface waters) in the Seine Estuary. The goal of this study was to identify the importance of atmospheric fluxes to occurrence of PAHs in the estuary, and to estimate the major pathways of their transport and accumulation within this ecosystem. The annual atmospheric inputs in the estuary ranged from 2.5 to 16 kg for the first sampling year, which is high when compared to those calculated for other European locations. In parallel, PAH transport from the atmosphere to the watershed outlet was investigated for two rural and urban small experimental watersheds within the Seine Estuary. In rural areas, atmospheric inputs are higher than exported loads by surface water and PAHs are accumulating in soils. The inverse occurs in urban areas, where the contribution of atmospheric deposition is negligible compared with PAH exported loads by runoff. These results allowed us to establish a mass balance for PAHs on the scale of the Seine Estuary, and to determine the dynamics of PAH transport. This study highlights the role of the atmospheric compartment in the transfer of contaminants and the importance of the local PAH inputs within the Seine Estuary.

Herbicides and nitrogen in precipitation: progression from west to east and contribution to the Marne river (France).

Herbicides and nitrogen fallout were studied in France at six sites from west to east. Atrazine, a herbicide widely used in France and forbidden in some European countries was found. Its fallout was quantified to 400 kg on the river Marne catchment (13 500 km2), an agricultural region located east of Paris. The average fallout contribution to the Marne river contamination was estimated at 20 ng/l from March to August. Independently of the wind direction, only a small part of this atmospheric contamination can reach adjacent countries.

Daily rhythms in the River Seine: Relative impacts of natural and anthropogenic factors☆

Abstract This publication presents the results obtained from observations on the daily cycles in the River Seine, downstream from the water purification plant at Acheres. Most of these observations concern six stations spread over 59 km. They were made in 1989 at three different times of the year (summer, autumn and winter) for periods lasting from 1 to 24 h according to the stations and the parameters studied: light, temperature, pH, dissolved oxygen, conductivity, chlorophylls, pheopigments, chlorides, bicarbonates, as well as different forms of nitrogen and phosphorus. Regarding conductivity and the concentrations of certain nutrients, an undeniable link was found between their daily rhythms and those of the flows from the Acheres sewage plant. In the absence of heavy rainfall, simple continuous measurements of conductivity along the river are sufficient to follow these flows and study their longitudinal dispersion as they moved downstream. The origin of the daily cycles of dissolved oxygen and chlorophyll are more complex. In June and October, they are mainly linked to light, the concentration of chlorophyll being moreover very closely related to temperature. In December on the other hand, the situation alters completely (minimum light, important fall in temperature, low chlorophyll concentrations). A daily cycle persists for dissolved oxygen but has nothing to do with light, being entirely subject to the discharges from the Acheres sewage plant.

Biota contamination by PCBs and trace metals in the freshwater estuary of the River Seine (France)

We studied the impact of urban and industrial activity upon the occurrence and the distribution of pollutants in the fresh estuary of the River Seine. Contamination was investigated under dry weather conditions, by determination of PCB and trace metal levels upstream and downstream of Rouen and the pollutant content of organisms with different positions in the trophic web. PCB contents of roach were higher downstream than upstream of Rouen. Cd levels showed a regular four fold increase from upstream to downstream of Rouen. Cyprinidae (ablet, roach) showed similar PCB or even higher trace metal levels than their predators (Percidae). This result suggests that contaminated food intake was not the main pathway for pollutant accumulation.

Atmospheric deposition of toxics onto the Seine Estuary, France: example of polycyclic aromatic hydrocarbons

Abstract. Concentrations of Polycyclic Aromatic Hydrocarbons (PAH) were measured in precipitation samples on a weekly basis between March and October 2001, at four sites in the Seine Estuary (France). Mean concentrations of total PAHs ( S 14 PAHs) ranged from 38 to 141 ng L-1. Fluoranthene, phenanthrene and pyrene were the dominant PAH compounds and were detected in each sample. The six potential carcinogenic PAHs accounted for 20 to 25% of the total PAH concentration in bulk deposition. The PAH signatures in bulk (wet and dry) deposition and surface water were also compared to investigate source/sink relationships. Seasonal patterns were observed with maximum loading occurring during the colder months of the studied period (March and April). Mean values of daily flux reported for S 14 PAHs ranged from 108 to 267 ng m-2 d-1. Spatial influences were also observed, indicating both localized and long-range atmospheric source inputs (controlled by hydroclimatic parameters).