Quality of dredged material in the River Seine basin (France). I. Physico-chemical properties

In rivers, sediments are frequently accumulating persistent chemicals, especially for those that are more contaminated as a consequence of pressure related to environmental pollution and human activity. The Seine river basin (France) is heavily polluted from nearby industrial activities, and the urban expansion of Paris and its suburbs within the Ile de France region and the sediments present in the Seine river basin are contaminated. To ensure safe, navigable waters, rivers and waterways must be dredged. In this paper, the quality of the sediment dredged in 1996, 1999 and 2000 is discussed. Physico-chemical characteristics of the sediment itself and of the pore-water are presented. Seine basin sediments show very diverse compositions depending on the sampling site. Nevertheless, a geographic distribution study illustrated that the Paris impact is far from being the only explanation to this diversity, the quality of this sediment is also of great concern. The sediment once dredged is transported via barges to a wet disposal site, where the dredged material is mixed with Seine water in order to be pumped into the receiving site. This sort of dumping might be responsible for the potential release of contaminants to the overlying water from the significantly contaminated sediments.     

Dissolved and bioavailable contaminants in the Seine river basin

Diffusive Gradient in Thin Films (DGT) and Semi-Permeable Membrane Devices (SPMDs) were deployed in the Seine river basin in order to assess labile metals and truly dissolved Polycyclic Aromatic Hydrocarbons. We show that the tools are reliable in aquatic environments to assess the speciation of dissolved contaminants and hence provide a good insight into the potential bioavailability of contaminants. The deployment of the DGT and SPMDs in contrasting environments in the Seine river basin allowed distinction to be made of availability of contaminants between headwater streams and much more impacted river reaches and an assessment of bioavailability. At the stations under urban influence, the impact of dissolved organic matter on both copper and PAHs bioavailability is less pronounced than at upstream stations, where humic substances dominate.     

Persistent toxic substance inputs to the river Seine basin (France) via atmospheric deposition and urban sludge application

Paris constitutes a major direct and indirect source of persistent toxic substances (PTS) to the river Seine, its tributaries and its basin, by atmospheric depositions and sewage sludge land-filling. The contaminant cycle and transfer pathways were investigated from 1999 to 2003 at local and inter regional scales in order to determine the respective importance of the main input and diffusion processes (wastewater, rainwater and runoff) from urban to rural areas. Paris constitutes an atmospheric emission hot spot for PAHs and PCBs. For example, for 2002, atmospheric concentrations ranged from 0.5 to 3 ng m(-3) for PAHs (Sigma 6 WHO) and from 0.06 to 0.69 ng m(-3) for PCBs (Sigma 7, EEC) and concentrations in bulk deposition ranged from 6.6 to 647 ng L(-1) for PAHs (Sigma 14) and from 0.6 to 8.1 ng L(-1) for PCBs. At Paris, annual atmospheric deposition inputs of PAHs (Sigma 6) and PCBs (Sigma 7) reached 104 g km(-2) and 35 g km(-2), respectively. PAHs followed a marked seasonal cycle in relation with winter domestic heating and bulk deposition concentrations were 5 to 15 times lower in remote areas. No seasonal cycle was observed for PCBs which varied little according to the area considered. PCB deposition fluxes were ruled by the rainfall amount, while for PAHs, the fluxes depended on local anthropogenic characteristics. At the scale of the Seine-Aval treatment plant comparison of annual inputs of PTS in wet period indicated that PCBs essentially come from atmospheric sources whereas PAHs are derived from both atmospheric and urban runoff sources. At the scale of the sub-basin, atmospheric inputs to the soil (Sigma 3 PAHs: 14-25 g km(-2), Sigma 7 PCBs: 5.6-25 g km(-2)) represent the prevailing source for PAHs and PCBs, as compared to that from the disposal of urban sludge on agricultural plots (Sigma 3 PAHs: 3-8 g km(-2), Sigma 7 PCBs: 0.5-2 g km(-2)).     

Antimicrobial resistance of fecal bacteria in waters of the Seine river watershed (France)

We studied the prevalences of antimicrobial resistance (AR) and multiple antimicrobial resistance (MAR) among the fecal bacteria found in the rivers of a large watershed under strong anthropogenic pressures, the Seine river watershed (France). Two groups of fecal indicator bacteria, Escherichia coli and intestinal enterococci, were tested for their susceptibility to 16 and 10 antimicrobials respectively, using the disk diffusion method. We found that 42% of the 214 E. coli river isolates were AR (resistant to at least one antimicrobial) and 35% were MAR (resistant to at least two antimicrobials). Among the 148 intestinal enterococci isolates from rivers, 83% were AR and 49% were MAR. We also investigated the sources of AR fecal bacteria found in the rivers of the watershed. A total of 715 E. coli isolates and 476 intestinal enterococci isolates were collected in point sources (municipal and hospital wastewaters) and non-point sources (surface runoff and soil leaching waters from agricultural or forest areas). For E. coli, the prevalence of AR differed widely from source to source and ranked in this order: hospital wastewaters (71%) > municipal wastewaters (44%) > agricultural non-point sources (16%) > forest non-point sources (2%). The prevalence of MAR ranked similarly, and the same trend was observed for intestinal enterococci. The AR level of fecal bacteria in the sources was related to their expected exposure level to antimicrobials before their release into the environment. A MAR index was calculated for every source and a good discrimination between them was thus obtained. At the global scale of the Seine river watershed, domestic wastewaters seemed more likely to be the predominant source of the AR fecal bacteria found in the rivers. This was corroborated by the similarity of the MAR indices from river and municipal wastewater isolates for both fecal indicators.     

Organic matter transport and degradation in the river Seine (France) after a combined sewer overflow

The impact of a combined sewer overflow (CSO) upon receiving waters has been studied in the river Seine during Summers 1995 and 1996. Three main events have been monitored with special attention paid to the computation of oxygen, carbon and suspended solids budgets. Bacterial biomass and bacterial production rates have been measured to provide a more accurate understanding of the carbon cycle of the river Seine. Oxygen consumption inside the polluted water masses was totally due to the activity of large bacteria discharged into the river by the CSO, the activity of native small bacteria did not significantly increase after CSOs. Suspended solids issued from the CSO very quickly settles in this deep, slowly flowing river. However, discharged dissolved organic carbon (DOC) cannot account for the observed oxygen depletions, the additional carbon source could be phytoplankton or deflocculated/degraded particulate organic matter.     

Primary production in headwater streams of the Seine basin: the Grand Morin river case study

Periphytic biomass has an important influence on the water quality of many shallow streams. The purpose of this paper is to synthesize the knowledge obtained on periphyton during the PIREN Seine research program. Periphyton was sampled using chl a measurements by acetone extraction and oxygen measurements with microelectrodes. The experiments reveal the presence of an important fixed biomass ranging between 123 and 850 mgchl a m(-2) and the mean gross production (photosynthesis) is shown to range between 180 and 315 mgC m(-2) h(-1). An independent approach was performed using the ProSe model, which simulates transport and biogeochemical processes in 22 km of the Grand Morin stream. A strong agreement between in situ measurements and the model results was obtained. The gross production obtained using ProSe is 220 mgC m(-2) h(-1) for the periphyton, which matches the experimental data. Although the net photosynthetic activity of the phytoplankton (0.84 gC gC(-1) d(-1)) is higher than the periphytic one (0.33 gC gC(-1) d(-1)), the absolute periphytic activity is greater since the mean biomass (3.4 gC m(-)(2)) is 10 times higher than the phytoplanktonic one (0.3 gC m(-2)), due to the short residence time of the water body (1.5d).     

Agriculture and groundwater nitrate contamination in the Seine basin. The STICS-MODCOU modelling chain

A software package is presented here to predict the fate of nitrogen fertilizers and the transport of nitrate from the rooting zone of agricultural areas to surface water and groundwater in the Seine basin, taking into account the long residence times of water and nitrate in the unsaturated and aquifer systems. Information on pedological characteristics, land use and farming practices is used to determine the spatial units to be considered. These data are converted into input data for the crop model STICS which simulates the water and nitrogen balances in the soil-plant system with a daily time-step. A spatial application of STICS has been derived at the catchment scale which computes the water and nitrate fluxes at the bottom of the rooting zone. These fluxes are integrated into a surface and groundwater coupled model MODCOU which calculates the daily water balance in the hydrological system, the flow in the rivers and the piezometric variations in the aquifers, using standard climatic data (rainfall, PET). The transport of nitrate and the evolution of nitrate contamination in groundwater and to rivers is computed by the model NEWSAM. This modelling chain is a valuable tool to predict the evolution of crop productivity and nitrate contamination according to various scenarios modifying farming practices and/or climatic changes. Data for the period 1970-2000 are used to simulate the past evolution of nitrogen contamination. The method has been validated using available data bases of nitrate concentrations in the three main aquifers of the Paris basin (Oligocene, Eocene and chalk). The approach has then been used to predict the future evolution of nitrogen contamination up to 2015. A statistical approach allowed estimating the probability of transgression of different concentration thresholds in various areas in the basin. The model is also used to evaluate the cost of the damage resulting of the treatment of drinking water at the scale of a groundwater management unit in the Seine river basin.     

The potential of pesticides to contaminate the groundwater resources of the Axios river basin. Part II. Monitoring study in the south part of the basin

A monitoring study was conducted during 1992-1994 in the south part of the Axios river basin, which constitutes one of the main rice-cultivated basins of Greece. The potential of pesticides to contaminate groundwater resources was assessed under realistic agricultural conditions using suction lysimeters. Pesticide residues were also measured in local drainage canals, the phreatic horizon and Axios river. Carbofuran, atrazine, alachlor, prometryne and propanil were regularly detected at concentrations exceeding 1 microg/l in the soil water of deeper soil layers and in the phreatic horizon of the fields. Residues of those pesticides were measured in the soil water and the phreatic horizon of all the studied fields even though they had only been applied in certain fields. This almost uniform distribution of pesticide residues across the whole of the studied area was attributed to rice cultivation. Soil water and its pesticidal content was horizontally transported from saturated soil conditions beneath rice paddies to adjacent corn or cotton-cultivated fields with lower soil moisture contents. The presence of high pesticide concentrations in the water of the Axios river, which was used for the irrigation of the studied area, had probably contributed to the generalized pesticide contamination of the soil water in the studied area. These results suggest that there is a high risk for groundwater contamination in the basin.     

A long-term view of nutrient transfers through the Seine river continuum

A model (the Riverstrahler model) is used to describe nutrient transfer and transformation at the scale of the whole drainage network of the Seine based on information concerning the basic mechanisms governing N, P and Si inputs to the drainage network and in-stream transformation and retention. It was used to calculate the budget of these nutrients through the whole river continuum from land to sea. With the help of historical documents, the constraints used as forcing function in this model were reconstructed to express the changing conditions of land-use and urban population over the last five hundred years. The corresponding scenarios were run for different hydrological regimes including dry, mean and wet conditions. The results were validated on the long-term series of nutrient measurements spanning more than a century available at some stations on the Seine, upstream and downstream of the city of Paris. The model was also used to explore past and future trends in nutrient loading, retention and delivery to the coastal zone, in response to human management of the terrestrial watershed. Beside the initial pristine state, used as an idealized reference state (with N, P and Si delivered fluxes of about 45-110 kg N km(-2) yr(-1), 2-5 kg P km(-2) yr(-1), 510-1325 kg Si km(-2) yr(-1)), four periods were distinguished. The first one is that of the traditional cottage economy which prevailed, with quite a constant total population, until the end of the 18th century. N, P and Si fluxes were about 235-750 kg N km(-2) yr(-1), 15-60 kg P km(-2) yr(-1) and 425-1280 kg Si km(-2) yr(-1), depending on hydrological conditions. The second period, from the beginning of the 19th century to about the 1950's, corresponded to rapid increase in the total and urban population with a corresponding increase of point sources of N and P. From 1950 onwards, modern farming practices resulted in a dramatic increase in diffuse sources of nitrogen and to a lesser extent phosphorus: riverine N and P export reached 1320-2800 kg N km(-2) yr(-1), and 310-340 kg P km(-2) yr(-1): silica export remained fairly constant at around 410-1260 kg Si km(-2) yr(-1) depending on the hydrological conditions. In the 1990's, the fourth period is represented by a stabilized population and improved wastewater treatment, when the export of phosphorus is reduced to values as low as 40-60 kg P km(-2) yr(-1), but without as effective a reduction of nitrogen export. This represents an unprecedented situation for the marine coastal system, i.e. a shift from nitrogen to phosphorus limitation, as nitrogen is still delivered far in excess of the amount of silica available for diatom blooms.     

Fecal bacteria in the rivers of the Seine drainage network (France): sources, fate and modelling

The Seine river watershed (France) is a deeply anthropogenically impacted area, due to the high population density, intense industrial activities and intensive agriculture. The water quality and ecological functioning of the different rivers of the Seine drainage network have been extensively studied during the last fifteen years within the framework of a large French multidisciplinary scientific program (PIREN Seine program). This paper presents a synthesis of the main data gained in the scope of this program concerning the microbiological water contamination of the rivers of the Seine drainage network. The more common indicator of fecal contamination (fecal coliforms) was mainly used; some complementary works used E. coli and intestinal enterococci as alternative fecal indicators. Point sources (outfall of wastewater treatment plants) and non point sources (surface runoff and soil leaching) of fecal pollution to the rivers of the watershed were quantified. Results showed that, at the scale of a large urbanised watershed as the Seine basin, the input of fecal micro-organisms by non-point sources is much lower than the inputs by point sources. However, the local impact of diffuse non-human sources (especially surface runoff of pastured fields) can be of major importance on the microbiological quality of small headwater rivers. Fecal contamination of the main rivers of the Seine watershed (Seine, Marne, Oise rivers) was studied showing high level of microbiological pollution when compared to European guidelines for bathing waters. The strong negative impact of treated wastewater effluents outfall on the microbiological quality of receiving rivers was observed in different areas of the watershed. Once released in rivers, culturable fecal bacteria disappeared relatively rapidly due to mortality (protozoan grazing, lysis) or loss of culturability induced by stress conditions (sunlight effect, nutrient concentration, temperature). Mortality rates of E. coli were studied in different types of rivers within the watershed showing, in summer conditions, no major difference in the mortality rates in small and large rivers. As a result of these studies, a module describing the dynamics of fecal bacteria has been developed and embedded within a hydro-ecological model describing the functioning of the rivers of the whole watershed (the SENEQUE model). Once validated, such a model can be used for testing predictive scenarios and thus can be a very useful tool for the management of microbiological water quality at the scale of the whole basin.     

Modelling the impacts of Combined Sewer Overflows on the river Seine water quality

To achieve the objectives of the European Water Framework Directive (EWFD), the Seine basin Water Authority has constructed a number of prospective scenarios forecasting the impact of planned investments in water quality. Paris and its suburbs were given special attention because of their impact on the river Seine. Paris sewer system and overflow control is of major concern in future management plans. The composition and fate of the urban effluents have been characterized through numerous in situ samplings, laboratory experiments and modelling studies. The PROSE model was especially designed to simulate the impact on the river of both permanent dry-weather effluents and of highly transient Combined Sewer Overflow (CSO). It was also used to represent the impact of Paris at large spatial and temporal scales. In addition to immediate effects on oxygen levels, heavy particulate organic matter loads that settle downstream of the outlets contribute to permanent oxygen consumption. Until the late 90s, the 50 km long reach of the Seine inside Paris was permanently affected by high oxygen consumption accounting for 112% of the flux upstream of the city. 20% of this demand resulted from CSO. However, the oxygenation of the system is strong due to high phytoplankton activity. As expected, the model results predict a reduction of both permanent dry-weather effluents and CSOs in the future that will greatly improve the oxygen levels (concentrations higher than 7.3 mgO(2) L(-1), 90% of the time instead of 4.0 mgO(2) L(-1) in the late 90s). The main conclusion is that, given the spatial and temporal extent of the impact of many CSOs, water quality models should take into account the CSOs in order to be reliable.     

Fates of bacteriophages and bacterial indicators in the Moselle river (France)

It has been suggested that bacteriophages can provide useful information about the pathogenic microorganisms, particularly enteric viruses, present in water. This information is complementary to that obtained from bacterial indicators of faecal contamination, which would be of great value for evaluating the risks associated with the use of certain types of water. Before bacteriophages can be used as indicators of faecal contamination, we need to confirm that bacteriophages give a different response to that given by the well-known bacteria indicators and to determine what happens to bacteriophages in river water. Indeed, drinking water is often produced from river water, either by natural filtration through the soil or after undergoing various treatments. We collected 96 river water samples from six different sites between February and November 2000. The samples were analysed for three faecal indicator bacteria (thermotolerant coliforms, enterococci and spores of sulphite-reducing anaerobes) and three types of bacteriophages (somatic coliphages, F-specific phages and Bacteroides fragilis phages). The densities of thermotolerant coliforms and enterococci depended mainly on physical factors such as flow rate and water temperature. High temperature and low flow rate led to a decrease in the density of these microorganisms, especially in the absence of a major input of faecal pollution. Conversely, the densities of somatic coliphages, F-specific phages and spores of sulphite-reducing anaerobes remained constant regardless of the flow rate and temperature. The density of Bacteroides fragilis phages was too low for unambiguous determination of their fate in river water.     

Integrated Risk Assessment for WFD Ecological Status classification applied to Llobregat river basin (Spain). Part II - Evaluation process applied to five environmental Lines of Evidence

Many indicators and indices related to a variety of biological, physico-chemical, chemical, and hydromorphological water conditions have been recently developed or adapted by scientists in order to support water managers in the Water Framework Directive (WFD) implementation. In this context, the achievement of a comprehensive and reliable Ecological Status classification of water bodies across Europe is hampered by the lack of harmonised procedures for selecting an appropriate set of indicators and integrating heterogeneous information in a flexible way.To this purpose, an Integrated Risk Assessment (IRA)² methodology was developed based on the Weight of Evidence approach. This method analyses and combines a set of environmental indicators grouped into five Lines of Evidence (LoE), i.e. Biology, Chemistry, Ecotoxicology, Physico-chemistry and Hydromorphology. The whole IRA methodology has been implemented as a specific module into a freeware GIS (Geographic Information System)-based Decision Support System, named MODELKEY DSS. This paper focuses on the evaluation of the four supporting LoE (i.e. Chemistry, Ecotoxicology, Physico-chemistry and Hydromorphology), and includes a procedure for a comparison of each indicator with proper thresholds and a subsequent integration process to combine the obtained output with the LoE Biology results in order to provide a single score expressing the Ecological Status classification. The approach supports the identification of the most prominent stressors, which are responsible for the observed alterations in the river basin under investigation. The results provided by the preliminary testing of the IRA methodology through application of the MODELKEY DSS to the Llobregat case study are finally reported and discussed.     

Historical perspective of heavy metals contamination (Cd, Cr, Cu, Hg, Pb, Zn) in the Seine River basin (France) following a DPSIR approach (1950-2005)

The Driver-Pressures-State-Impact-Response approach is applied to heavy metals in the Seine River catchment (65,000 km(2); 14 million people of which 10 million are aggregated within Paris megacity; 30% of French industrial and agricultural production). The contamination pattern at river mouth is established on the particulate material at different time scales: 1930-2000 for floodplain cores, 1980-2003 for suspended particulate matter (SPM) and bed-sediments, 1994-2003 for atmospheric fallout and annual flood deposits. The Seine has been among the most contaminated catchments with maximum contents recorded at 130 mg kg(-1) for Cd, 24 for Hg, 558 for Pb, 1620 for Zn, 347 for Cu, 275 for Cr and 150 for Ni. Today, the average levels for Cd (1.8 mg kg(-1)), Hg (1.08), Pb (108), Zn (370), Cu (99), Cr (123) and Ni (31) are much lower but still in the upper 90% of the global scale distribution (Cr and Ni excepted) and well above the natural background values determined on pre-historical deposits. All metal contents have decreased at least since 1955/65, well before metal emission regulations that started in the mid 1970's and the metal monitoring in the catchment that started in the early 1980's. In the last 20 y, major criteria changes for the management of contaminated particulates (treated urban sludge, agricultural soils, dredged sediments) have occurred. In the mid 1990's, there was a complete shift in the contamination assessment scales, from sediment management and water usage criteria to the good ecological state, now required by the 2000 European Directive. When comparing excess metal outputs, associated to river SPM, to the average metal demand within the catchment from 1950 to 2000, the leakage ratios decrease exponentially from 1950 to 2000 for Cd, Cr, Cu, Pb and Zn, meanwhile, a general increase of the demand is observed: the rate of recycling and/or treatment of metals within the anthroposphere has been improved ten-fold. Hg environmental trajectory is very specific: there is a marked decontamination from 1970 to 2000, but the leakage ratio remains very high (10 to 20%) during this period. Drivers and Pressures are poorly known prior to 1985; State evolution since 1935 has been reconstructed from flood plain cores analysis; Impacts were maximum between 1950 and 1970 but remained unknown due to analytical limitation and lack of awareness. Some Responses are lagging 10 y behind monitoring and have much evolved in the past 10 y.     

Analysis for chromium traces in the aquatic ecosystem II. A study of Cr(III) and Cr(VI) in the susquehanna river basin of New York and Pennsylvania

A new procedure for the differential analysis of ppb concentrations of Cr(III) and Cr(VI) in natural waters has been developed. In this method, three-liter samples are filtered, acidified to pH 6.0, and divided into three parts. One liter is passed through an anion-exchange resin bed (AG-1X4, 100–200 mesh, Cl^? form), one liter is passed through a cation-exchange resin bed (50 WX4, 100–200 mesh, Na⁺ form), and one liter remains untreated. 10 ml of 1.0 M HNO₃ are then added to each of the three aliquots and they are individually reduced in volume by evaporation to 10 ml. Analysis by A.A. employing the method of standard addition follows. By difference, cationic, anionic, and non-ionic Cr concentrations in the sample become available. Cr(III) concentration is probably closely related to (cationic + non-ionic), and Cr(VI) concentration in the original sample corresponds to the anionic portion. Precision is ±20 % or better for total, cationic, and anionic Cr at the 1 ppb level. Precision of the non-ionic analyses is closely linked to these other precisions as the concentration of non-ionic Cr species in the original sample is obtained by the mass balance requirement set up by the other three analyses.Application of this technique to the analysis of natural water samples revealed the predominance of trivalent Cr in uncontaminated waters of the Upper Susquehanna River Basin (1–2 ppb). River water samples taken downstream of Binghamton, N.Y. area sewage outfalls revealed an increase in the mean Cr(VI) content of the river from ～0.5 ppb to ～1.6 ppb. The persistence of the Cr(VI) at least as far as 60 km downstream of the outfall area leads to the conclusion that at these levels, little dissolved Cr(VI) is removed from the river as it flows away from a point of contamination. Concentrations of Cr in samples of river sediments also revealed Cr contamination below the outfall area, and Cr contamination extended at least as far as 60 km downstream of the outfall area.     

Assessment of river contamination by estrogenic compounds in Paris area (France)

Wastewater treatment plants (WWTPs) receive a large spectrum of endocrine disrupting compounds (EDCs) that are partially eliminated during treatment processes and discharged into rivers. Given the lack of information in France about river contamination by EDCs, we chose to examine estrogenic potential of WWTP influents, effluents and receiving waters in Paris and its suburbs. Water samples were analyzed using gas chromatography coupled with mass spectrometry for quantifying natural and synthetic estrogens combined with an in vitro estrogenicity bioassay associated to a high pressure liquid chromatography fractionation. The four estrogens investigated, Estrone (E1), 17beta-Estradiol (E2), Estriol (E3) and 17alpha-Ethinylestradiol (EE2) were found in all WWTP and river samples at concentrations ranging from 2.7 to 17.6 ng/l and 1.0 to 3.2 ng/l, respectively. The synthetic estrogen EE2 seems more resistant to biodegradation in WWTPs and thus accounted for 35-50% of the estimated estrogenic activity in rivers. However, fractionation of samples and differences between concentrations of E1, E2, E3 and EE2 and the estrogenic activity measured by the in vitro bioassay suggested a complexity of mechanisms underlying the biological response that could not be attributed only to the investigated molecules.     

Geo-referenced modeling of zinc concentrations in the Ruhr river basin (Germany) using the model GREAT-ER

Zinc enters surface waters from a variety of different emission sources. The geo-referenced model GREAT-ER (Geo-referenced Regional Exposure Assessment Tool for European Rivers) was applied to simulate spatially resolved zinc concentrations in the Ruhr river basin. The model links geo-referenced emissions (loads) to concentrations at local and regional scales and allows for evaluating the relative importance of emission sources. For each emission from point sources (household, industry, urban runoff) and non-point sources (agriculture, natural background), zinc loads were independently estimated using appropriate reference parameters (number of inhabitants, surface area drained, agricultural area, zinc ore regions). For point emissions from industry and mine drainage loads were taken directly from available data compilations. Simulated total zinc concentrations agree well with monitoring data. The strength of the modeling tool became evident from the unequivocal link that could be established between observed surface water concentrations and the large zinc input from geogenic sources and abandoned mines. These emission sources are regional characteristics of the Ruhr river basin and due to the fact that some regions are relatively rich in zinc ore, which was extracted over a long period of time. Although most of these emissions occur in the upper part of the catchment, they contribute to approximately one-third to the zinc load at the confluence with the Rhine River. Urban emissions from household, traffic (road) and buildings (roof) were shown to be responsible for approximately half of the concentration in the Ruhr at the confluence with the Rhine River.     

Spatial dynamics of farming practices in the Seine basin: methods for agronomic approaches on a regional scale

A research procedure is proposed which aims to analyse the agricultural spatial dynamics during the last thirty years using two levels of organisation of farming activity: the agricultural production system and the cropping system. Based on methods of statistical mapping and data mining, this procedure involves modelling the diversity of production systems and cropping systems (crop successions and sequences of cultural practices for each crop) in the form of classes independently of their localisation within the basin. It identifies homogeneous regions made up of groups of contiguous agricultural districts which exhibit similar combinations of production systems, crop successions or cultural practices during a given period of time. The results show a major increase in arable farms since 1970 at the expense of dairy farms and mixed cropping/livestock. This trend however appeared to be greatly spatially differentiated according to the agricultural districts, since livestock remained important on the edges of the basin, whereas it practically disappeared in its centre. The crop successions practiced in the basin and the cultural practices used on them also appear to be spatially differentiated, although the link to the production systems is not always clear. Thus it appears pertinent to combine the analysis of the two levels of organisation of the agriculture (methods of land use described by the concept of cropping system, and also the production systems into which the cropping systems fit) in the context of an environmental problem.