Urban Sludge Research Articles

Study on Lowcost Revegetation Technical Measures on Ferrum Tailings Bank in Huludao, Northeast China

This study focused on the technical measures of revegetation on ferrum tailings bank in Huludao, China. Adopting field test method, a revegetation trial was conducted on the Yangjiazhangzi waste ferrum tailings bank. By composting the urban sludge + river mud + straw inside planting pit to ameliorate tailings matrix, planting perennial herb to establish closed type sand barrier to shelter bush-herbage growth, transplanting nutrition cup bush seedlings and sowing herbage seed on the composting pit to establish bush-herbage clump, these technical measures can solve the major constraints to plant growth and establish survival bush-herbage vegetation at lowcost. The results show that Pit layered composting is the cost-effective measure to improve ferrum tailings planting matrix; Planting perennial herb sand barrier t is a good measure to improve microhabitat; Planting bush-herbage clump is a good pattern to resist the extreme ferrum tailing environment; Hippophae rhamnoides Linn., Caragana Korshinskii Kom., Medicago sativa Linn.and Astragalus adsurgens Pall are good pioneer species for revegetation on the ferrum tailings bank. Experiment proved that the combination of these technical measures can reconstruct vegetation, this revegetation pattern is worthy of reference for similar mine ecological restoration.

Microbial enrichment of compost with biological control agents to enhance suppressiveness to four soil-borne diseases in greenhouse

The aim of the present work was to study if the level and reproducibility of suppressive properties of compost can be increased upon enrichment with biological control agents. A compost made from green waste, organic urban waste and urban sludge was inoculated with commercial formulations of Trich oderma and non-pathogenic Fusarium. The compost showed to be suppressive against some soil-borne pathogens, except R. solani, while such activity was lost after sterilisation. The suppressive effect of enriched compost was assessed in greenhouse trials on cucumber, tomato, bean and basil. The addition of T. harzianum T-22 at 4 g l-1 dosage was able to increase suppressiveness against R. solani of a 40% compost and 60% peat mix and to increase biomass of bean compared to a peat inoculated control. The same enrichment did not reduce suppressiveness of compost against P. ultimum and P. nicotianae, so its addition might be considered a good strategy to increase compost suppressiveness. Disease suppressiveness of sterilised compost was restored by the addition of T. viride TV1 (> 4 gl-1) in P. ultimum /cucumber and in P. nicotianae/tomato. This study represents a further step toward the development of a substrate able to control a wide range of soil-borne pathogens and in the use of fortified composts for controlling plant diseases.

Modélisation d'un procédé de séchage solaire de boues urbaines

The greenhouses of solar drying for urban residual sludge represent an economic alternative to the classic thermal dryers. The aim of this study is the modelling with a two-scale approach of the process Solia ™ . A three-dimensional modelling with the software Ansys ® /Fluent ® allows to visualize internal aeraulics and exchanges, and so to underline influent parameters on the process effiency. The systemic zero-dimensional model is developed on Matlab ® /Simulink ® software. It takes into account the previous exchanges and allows a higher physical simulation time, at a day or season scale.

The impact of ammonia nitrogen concentration and zeolite addition on the specific methanogenic activity of granular and flocculent anaerobic sludges

This work presents the effect of ammonia nitrogen concentration and zeolite addition on the specific methanogenic activity (SMA) of different anaerobic sludges with various physical structures (granular and flocculent), operating in batch conditions. Piggery, malting production and urban sludges derived from full-scale anaerobic reactors were tested in the experiment as the source of inoculum in batch digesters. It was found that piggery sludge was the most affected by the increase of ammonia nitrogen concentration while malting producing and municipal sludges were less affected. In general, the addition of zeolite at doses in the range of 0.01–0.1 g/g VSS reduced the inhibitory effect of N-NH4 + for piggery sludge (P.S.). For this sludge, the propionic:acetic ratio increased when the concentration of N-NH4 + increased, indicating that methanogenesis was affected. Finally, a study of the microbial population involved in this study for P.S. by using 16S rRNA based molecular techniques revealed a presence of microorganisms following the order: Methanococcaceae > Methanosarcina > Methanosaeta.

Treatment of Urban Waste Water Sludges by Means of his Appraisement for Incorporation in Ceramic Matrix

Industrial residues generated by the modern society constitute an environmental problem and are harmful both to the health and to the environment (greenhouse effect). In addition, they can give place to leaching pollutants [1,2] more concretely in the European area; it tends to the politics of them 3R, recovery, recycling and reutilization. It is, in this frame, where the present work is included. On the other hand, like result of environmental regulations, bricks of clay are going to be demanded by an increase in the insulating capacity. A way of increasing the insulating capacity of the bricks is to generate porosity in the counterfoil of clay.

Characterization of the Soil Organic Matter in Agricultural Mine Spoils and Reclaimed Soils Treated with Organic Amendments

Recycling organic waste in agricultural soils is a valid solution. We performed short‐term experiments to investigate the fate of urban sludge and composts, in mine spoils, cultivated or uncultivated, and reclaimed soils located in Florence and Milan, Italy. The samples, either treated or untreated, were fractionated by density into light (<1.63 Mg m−3) and heavy (>1.63 Mg m−3) fractions. The fractions were analyzed for total carbon (C) and nitrogen (N) contents and for δ 13C and δ 15N isotopes, and they were characterized by 13C NMR spectroscopy. Treatment increased the heavy fraction. The addition of sludge in the Florence area acts in synergy with the cultivation, increasing the light fraction (LF). In the Milan area, the LF tends to be decomposed and apparently transformed into HF. The addition of amendments or cultivation enhances the decomposition with release of carbon dioxide. For future research, we suggest lengthening the time of the experiments to integrate climatic variations.

Dewatering of primary settled urban sludge in a vertical flow wetland

Sludge drying reed beds (SDRBs) are a combination of traditional sludge drying beds and constructed wetlands. Their main advantages include low investment, infrequent biosolids removal (of the order of years), dewatering and mineralization of biosolids, minimization of biosolid volume, simplicity and economy, and production of a beneficial, well-composted side product. A constructed wetland facility is used to treat the sewage from the municipality of Nea Madytos, Thessaloniki Province, North Greece. The primarily produced biosolids in the Imhoff tank of this facility are treated with a vertical flow SDRB. The performance and dewatering efficiency of this system was monitored for 1year. Over the 12years of operation of the treatment plant, 7884m3 of biosolids from the Imhoff tank were transferred to the SDRBs. Until today, no biosolids were removed, and the level of the dewatered sludge on the bed is built to about 20cm, with a volume of residue sludge of 28m3. This corresponds to a biosolid reduction of 99.64%. At the end of the examination period the TS (VS) content varied from 55% (40%) in the top layer to 65% (35%) in the bottom layer. The heavy metal concentration meets the European Union standards for heavy metals in case of agricultural disposal of the treated sludge.

Humic acids of different origin as modifiers of cadmium-ion chemistry: A spectroscopic approach to structural properties and reactivity

The physical–chemical properties of humic acid fractions (HA) derived from urban sludge (CUS) and cattle manure (CCM) composts, and agricultural soil (FS) fertilised with sludge for ten years, were initially explored by elemental analysis, UV–Vis, FTIR and fluorescence. These properties were then compared with reference HA of terrestrial (SO) and aquatic (SR). To correlate the chemical properties and the reactivity of these HA, the binding of Cd(II) was investigated by fluorescence quenching techniques (FQ). Indeed, fluorescence spectroscopy has been proven to be a powerful tool in discriminating the origin, chemical features and degree of humification of naturally occurring organic matter. The HA compost exhibited higher N content, smaller molecular size and lower aromaticity than the reference HA. In addition, the CUS sample showed clear evidence of impurities, most likely of microbial origin, which was not evident in the FS sample ( i.e. during its further evolution/humification in soil). The quenching effect of Cd(II) is adequately described by a modified Stern–Volmer equation, which is based on two population fluorophores, one not being accessible. The resulting Cd–HA log K (conditional association constants) decreased in the order SO > CUS > FS > CCM > SR, thus reflecting the relative binding affinity. A similar order was found for the corresponding Cd(II) capacity, which is based on total Cd content in Cd-humate precipitates. Lastly, fluorescence analysis of the soluble and insoluble fractions clearly revealed the fluorophores most involved in the binding process. In conclusion, our work provides evidence that compost is a reservoir of “humic-like” material capable of compensating for any organic carbon deficit in soil and lessening the effect of inorganic pollutants.

Assessment of nitrate contamination risk: The Italian experience

The purpose of this study is to show the results of the Italian research project of national interest (PRIN) launched in 2006 and finished in 2008, concerning the “assessment of groundwater contamination risk by nitrates assessment”. The project verified the IPNOA method for nitrate groundwater contamination risk assessment in four test-sites of Italy. The IPNOA is a parametric index which assesses the potential hazard of nitrate contamination originating from agriculture on a regional scale. The method integrates two categories of parameters: the hazard factors (HF), which represent all farming activities that cause, or might cause, an impact on soil quality in terms of nitrate (use of fertilisers, application of livestock and poultry manure, food industry wastewater and urban sludge), and the control factors (CF) which adapt the hazard factors to the characteristics of the site (geographical location, climatic conditions and agronomic practices). Finally, the Potential Risk Map is obtained by coupling the potential hazard of nitrate pollution (IPNOA) and the aquifer Contamination Vulnerability Map. The project was carried out by five Research Units (RU) from the Politecnico di Torino, Universities of Piacenza, Florence, Naples and Palermo. The geochemistry of groundwaters from the four test-sites was studied to determine the distribution of nitrate, and to evaluate groundwater chemical facies. All the study areas are affected by groundwater nitrate contamination and often by hydrogeochemical peculiarities. In some cases isotopic study, δ 18O–NO 3 δ 15N–NO 3, allowed to differentiate nitrates of chemical fertilisers from those of biological origin, as well as denitrification processes.

The use of sewage sludge as soil amendment. The need for an ecotoxicological evaluation

Sewage sludge use in agriculture should be limited by the presence of metals and other persistent environmental pollutants. The present study aims to contribute for the definition of a test battery of ecotoxicological assays that allows a proper ecotoxicological characterization of sludges, providing information on their potential hazard and identified “safe” application levels. Three sludges from distinct sources (urban, olive-processing, and electroplating industries) were tested using avoidance and reproduction tests with earthworms (Eisenia andrei) and springtails (Folsomia candida) and plant growth tests with turnips (Brassica rapa) and oats (Avena sativa). Different soil–sludge mixture concentrations mimicking recommended/realistic field dosages were tested. Only the sludge from the electroplating industry induced an avoidance response from the earthworms (EC50 = 0.4 t/ha) and collembolans (no observed effect concentration (NOEC) = 15 t/ha). This sludge was the only sludge responsible for any effect on the reproductive output of the earthworms (EC50 = 7.74 t/ha). Regarding collembolans, none of the sludges tested caused any significant decrease in reproduction. In higher plant tests, the two industrial sludges were toxic, causing a decrease growth in both species. The EC20 values determined for B. rapa were 20.3 and 24.2 t/ha and for A. sativa 14.7 and 16.2 t/ha for sludges from olive-processing and electroplating industries, respectively. The metal loadings of the different test sludges could partially explain the results obtained. The toxicity of the test sludge from electroplating industry observed on the tested invertebrates and plants could be explained by the high amount of total chromium from which 22.3% was in the most toxic oxidation state—Cr(VI). However, the toxicity caused by the sludge from the olive-processing industry in the test plants could be attributed to the presence of other compounds (not measured in this study) since the metal content was not high enough to induce such an effect. The absence of toxicity showed by the urban test sludge was in agreement with its low levels of metals. The response of the different test organisms and end points varied according to the sludge type. The urban sludge was non-toxic whereas the sludge from the electroplating industry caused a toxic effect on almost all parameters measured (avoidance behavior of both test organisms, reproduction of earthworms, and growth of both plant species). Sludge from the olive-processing industry only caused a toxic effect on growth of both plant species. By analyzing the sensitivity of the different parameters for the most toxic sludge, it was found that avoidance and reproduction were more sensitive than plant growth, whereas plant seed germination was not sensitive at all. The ecotoxicological evaluation of wastes can be used as an environmental safety control of sludge use in agriculture. A tiered approach could be adopted for this purpose, incorporating avoidance tests in the first tier (screening level) and reproduction and plant growth tests in a second tier. But more evidence aiming to define the most suitable ecotoxicological test battery for specific sludges with a different contamination profile is still needed.

Mineralização de compostos nitrogenados após aplicações de lodos de esgoto em quatro cultivos de milho

O teor de N disponível em solos tratados com lodo de esgoto é um dos fatores restritivos à aplicação do resíduo em grandes volumes na agricultura, e deve ser utilizado nas normas que regulamentam seu uso agrícola com o fim de evitar a contaminação ambiental do solo e corpos d'água com nitrato. Quando se aplica o resíduo pela primeira vez em um solo, a disponibilização de N mineral a partir de compostos orgânicos naturais do solo não é diretamente considerada no cálculo da taxa de aplicação máxima, e este procedimento é comum também nas recomendações de adubação mineral. Porém, a aplicação continuada desses resíduos pode causar efeitos residuais acumulativos na geração de N mineral, o que implicaria recomendações específicas para reaplicações em uma mesma área. O objetivo deste trabalho foi avaliar a disponibilidade potencial de N mineral em um Latossolo previamente tratado com lodos de esgoto e com quatro cultivos sucessivos de milho. Amostras de solo da camada de 0-20 cm foram coletadas em subparcelas de um experimento realizado em campo, entre 1999 e 2002, em Jaguariúna (SP), onde foram aplicados 0, 14.716, 29.432, 58.864 e 117.728 kg ha-1 de lodo de origem urbana (Franca, SP) e 0, 22.700, 45.400, 90.800 e 181.600 kg ha-1 de lodo produzido a partir de esgotos urbanos e industriais (Barueri, SP). As doses foram parceladas em quatro aplicações anuais consecutivas. Em laboratório, essas amostras foram incubadas durante 15 semanas. As análises iniciais dos solos evidenciaram que houve efeito residual das aplicações prévias dos lodos sobre o acúmulo de N orgânico e de nitrato. No final da incubação, houve acúmulo de N inorgânico no solo e diminuição do pH em função da maior geração de nitrato com as doses crescentes dos lodos de esgoto. O potencial de mineralização estimado pelo modelo exponencial simples foi de 28 mg kg-1 de N no tratamento sem lodo, e crescente, de 28 para 100 mg kg-1 de N, nos tratamentos com lodo de Franca, e de 40 para 113 mg kg-1 de N tratamentos com lodo de Barueri. Concluiu-se que os efeitos residuais acumulados no solo devem ser considerados quando se pretender fazer novas aplicações de lodos de esgoto num mesmo local. Os potenciais de mineralização de compostos de N do solo e do lodo que será utilizado, além do acúmulo de nitrato no perfil do solo, devem ser determinados e considerados para o cálculo da dose da próxima aplicação.

Estudo geoquímico da disposição de lodo de estação de tratamento de água em área degradada

This survey determined the physical and chemical properties of the gravel place where urban sludge from Rio Descoberto's Water Treatment Plant is disposed. Physical, chemical and biological analysis of the soil samples (n=54), sludge samples (n=2), chemical coagulant (n=20) and samples from superficial waters (n=9) and water table (n=60) were performed. As results we can emphasize the horizontal distribution of mineral phases like gibbsite, organic material, exchanged Ca, available Mn and P on the soils are originated from the sludge. Some of these mobile elements could stimulate the growing of the vegetation, but they also could contaminate the water table.

Characterization of Sewage Sludge Water Vapor Diffusivity in Low-Temperature Conductive Drying

In order to study the low-temperature conductive drying of urban sewage sludge and evaluate its essential characteristics, a laboratory-scale drying device was set up. Sludge is modelled as a coarse aggregated, porous medium, and experiments are conducted to study its rheological behavior throughout a drying cycle and aggregation effects on diffusion. Investigations are based on a macroscopic model of sludge aggregates where only external porosity is accounted for. This paper presents a method to evaluate water vapor diffusivity within urban sludge based on an analytical solution of a Fickian diffusive model which enables diffusivity determination by simple exponential regression over experimental data. Experiments are carried out with three levels of heating fluxes, 300, 525 and 700 W/m2, without any remarkable effect of flux density on water vapor diffusivity over the tested range. Further experiments are conducted to underline the effect of mixing frequency. Predictive correlations for water vapor diffusivity as a function of sludge dry solid content and mixing frequency are reported in this work.

Evaluation of the genotoxicity of treated urban sludge in the Tradescantia micronucleus assay

The sludge produced in sewage treatment plants can contain toxic substances. Among these, the genotoxic substances are of great concern. The present paper aimed at evaluating the genotoxicity of treated sludge samples collected at four different sewage treatment plants (STP) located in the State of São Paulo, Brazil using the Trad-MN assay. Another objective of the study was to compare the responses of the Clone #4430 with the Tradescantia pallida. Sludge samples mixed with reference soil in concentrations of 10, 25 and 50% (v/v) were tested in experiments with 3 months exposure in the field. Negative and positive controls (arsenic trioxide) were also tested with both plants. In Clone #4430 two sludge samples induced genotoxicity while in T. pallida three were positive, although no clear dose-response were observed for both plants. Results with the negative and positive controls suggest that T. pallida presented similar results when compared to the Clone #4430. The protocol using plants chronically exposed to sludge mixed with soil seems to be a promising tool to assess the genotoxicity of sludge although time consuming.

Correlation between dewatering and hydro-textural characteristics of sewage sludge during drying

The aim of this work consists in analysing the dewatering and the shrinkage of a residual urban sludge during convective drying with the objective to find correlations between dewatering and hydro-textural characteristics of the sludge. Laboratory drying experiments are performed in immobile atmosphere, at a temperature of 30 °C, with various relative humidities. Kinetics curves of dewatering and deformation are obtained. A coupled analysis of dewatering and induced volume shrinkage is proposed. This analysis allows: (i) to distinguish the respective parts played by the intrinsic characteristics of the sludge and the process parameter and (ii) to find correlations between the hydro-textural characteristics of the sludge, and its drying and shrinkage aptitudes. Attention is given to the fact that the process parameter, i.e. relative humidity, controls the first constant rate period of the dewatering and that the hydro-textural state of the sludge determine the transitions between the different dewatering periods. The relationships between the hydro-textural characteristics and the dewatering and shrinkage aptitude allow predicting the sludge behaviour during drying according to its characteristics, which is essential information in the choice of the drying strategy.

Estoques de carbono orgânico e de nitrogênio, pH e densidade de um Latossolo após três aplicações de lodos de esgoto

O elevado conteúdo de matéria orgânica de lodo de esgoto é uma das motivações para sua disposição no ambiente como condicionador do solo. O objetivo deste trabalho foi avaliar o efeito de aplicações consecutivas de lodo de esgoto sobre o acúmulo de C e de N (total e mineral), sobre o pH e sobre a densidade de um Latossolo. As avaliações foram feitas em duas profundidades do solo (0-0,1 e 0,2-0,4 m) após três cultivos de milho, em experimento realizado entre os anos de 1999 e 2001, em Jaguariúna-SP. Os tratamentos consistiram de cinco doses crescentes de dois tipos de lodo de esgoto, aplicadas a cada cultivo. O aumento das doses aplicadas (totalizando 0, 10.284, 20.568, 41.136 e 82.272 kg ha-1) do lodo da Estação de Tratamento de Esgotos de Franca-SP, de origem urbana, causou crescimento significativo dos estoques de C orgânico e de N na camada superficial. Nos tratamentos com o lodo da Estação de Tratamento de Esgotos de Barueri-SP (totalizando 0, 17.405, 34.810, 69.620 e 139.240 kg ha-1), produzido a partir de esgotos urbanos e industriais, apesar da incorporação de 14 % a mais de C ao solo, os estoques de C não foram influenciados pelas doses aplicadas e houve crescimento significativo dos estoques de N. A densidade na camada superficial diminuiu significativamente com o aumento das doses dos dois tipos de lodo de esgoto. Houve acidificação do solo nas duas camadas estudadas, com necessidade de duas calagens, após o segundo e terceiro cultivos. Observou-se lixiviação de N-mineral para maiores profundidades do solo.

Coupling a respirometer and a pycnometer, to study the biodegradability of solid organic wastes during composting

A new method, coupling a respirometer and a pycnometer, to follow the biodegradation of solid organic wastes is presented. The pycnometer was used to observe the development of the free air space in the sample during the respirometric experiments and verified that this parameter remained favourable to the substrate oxygenation. To test this new method, respirometric experiments were conducted on four solid waste samples (a mixture of agrofood sludge and pine bark chips, a mixture of urban sludge with new and reused pine bark chips collected before and after 21 days of composting, and a mixture of household wastes). The respirometer is based on a 10 l reactor filled with the sample. It was designed to allow the control of operating conditions: temperature, moisture and aeration. During respirometric experiments, the material temperature was constant and homogeneous. However, large variations in the moisture content were measured between the beginning and the end of respirometric tests. Moreover, the development of moisture variability throughout the substrate was observed. The aeration regime was characterised as a perfectly mixed phase considering the results of retention time-distribution studies and the free air space values measured with the pycnometer. The pycnometer accuracy was confirmed by low differences between experimental and theoretical free air space values for water and spherical glass beads. Moreover, it was verified that this measurement had no influence of respirometric responses. Applying the proposed method to the four substrates demonstrated the interest in mixing the material during the respirometric tests, when the oxygen uptake rate rO2 fell to a low and stable value. Indeed, in some cases, such mixing stimulated the restart of rO2 that confirmed the presence of residual biodegradable organic matter. The major effect of mixing was to restore favourable moisture content throughout the substrate. The results revealed that a small mixing impact corresponded to either a low substrate biodegradability or a high initial moisture content. The pycnometer measurements demonstrated the influence of a low free air space. It appeared that the absence of oxygen uptake restart after mixing, in the presence of residual organic matter, could be due to a low free air space. These results demonstrated the need (i) to mix the samples to quantify all its biodegradable organic matter and (ii) to control the moisture, temperature and aeration to ensure favourable conditions of biodegradation.

Ozone pre-treatment as improver of PAH removal during anaerobic digestion of urban sludge

Polycyclic aromatic hydrocarbons are ubiquitous persistent pollutants. They may accumulate in sludge during wastewater treatment because of their low biodegradability and their hydrophobic characteristics. Combination of ozonation and anaerobic digestion may be efficient to remove PAHs naturally present in sludge. The objective of this study was to investigate the impact of ozone pre-treatment, with and without surfactant addition, on the anaerobic degradation of 12 PAHs (from low to high molecular weight). Under anaerobic digestion without ozonation pre-treatment, the highest removals were obtained for the lightest PAHs (3-aromatic rings). Ozonation pre-treatment of sludge allowed to increase biodegradability or bioavailability of each PAH, and the PAH removals were well correlated to the PAH solubility. Finally, addition of tyloxapol before sludge ozone pre-treatment had antagonist effects on PAH removal during anaerobic digestion: negative impact on anaerobic ecosystem activity and improvement of PAH bioaccessibility (particularly the PAHs with the highest octanol water partition coefficients).

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.

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)).