The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
G B Shimmield - One of the best experts on this subject based on the ideXlab platform.
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Historical storage budgets of organic carbon, nutrient and Contaminant elements in saltmarsh sediments: biogeochemical context for managed realignment, Humber Estuary, UK.
The Science of the total environment, 2008Co-Authors: Julian E. Andrews, G Samways, G B ShimmieldAbstract:Biogeochemical data from Welwick marsh (Humber Estuary, UK), an actively accreting saltmarsh, provides a decadal-centennial-scale natural analogue for likely future biogeochemical storage effects of managed realignment sites accreting either intertidal muds or saltmarsh. Marsh topographic profiles and progradation history from aerial photographs were combined with (137)Cs and niobium contamination history to establish and verify chronology and sediment mass accumulation. These data, combined with down-core measurements of Particulate organic carbon (C(org)), organic nitrogen (N(org)), particle reactive phosphorus and selected Contaminant metal (Zn, Pb, Cu, As and Nb) contents were then used to calculate sediment and chemical storage terms and to quantify changes in these over time. These data are used to help predict likely future biogeochemical storage changes at managed realignment sites in the estuary. The net effect of returning some 26 km(2) of reclaimed land to intertidal environments now (about 25% of the maximum possible realignment storage identified for the estuary) could result in the storage of some 40,000 tonnes a(-1) of sediment which would also bury about 800 tonnes a(-1) of C(org) and 40 tonnes a(-1) of N(org). Particulate Contaminant P burial would be around 25 tonnes a(-1) along with approximately 6 tonnes a(-1) Contaminant Zn, 3 tonnes a(-1) Contaminant Pb, and approximately 1 tonnes a(-1) Contaminant As and Cu. The study also shows that reclamation activities in the outer estuary since the mid-1700s has prevented, in total, the deposition of about 10 million tonnes of sediment, along with 320,000 tonnes of C(org) and 16,000 tonnes of N(org). The study provides a mid-1990s baseline against which future measurements at the site can determine changes in burial fluxes and improvement or deterioration in Contaminant metal contents of the sediments. The data are directly relevant for local managed realignment sites but also broadly indicative for sites generally on the European North Sea Coast.
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Historical storage budgets of organic carbon, nutrient and Contaminant elements in saltmarsh sediments: Biogeochemical context for managed realignment, Humber Estuary, UK
Science of The Total Environment, 2008Co-Authors: Julian E. Andrews, G Samways, G B ShimmieldAbstract:Abstract Biogeochemical data from Welwick marsh (Humber Estuary, UK), an actively accreting saltmarsh, provides a decadal–centennial-scale natural analogue for likely future biogeochemical storage effects of managed realignment sites accreting either intertidal muds or saltmarsh. Marsh topographic profiles and progradation history from aerial photographs were combined with 137 Cs and niobium contamination history to establish and verify chronology and sediment mass accumulation. These data, combined with down-core measurements of Particulate organic carbon (C org ), organic nitrogen (N org ), particle reactive phosphorus and selected Contaminant metal (Zn, Pb, Cu, As and Nb) contents were then used to calculate sediment and chemical storage terms and to quantify changes in these over time. These data are used to help predict likely future biogeochemical storage changes at managed realignment sites in the estuary. The net effect of returning some 26 km 2 of reclaimed land to intertidal environments now (about 25% of the maximum possible realignment storage identified for the estuary) could result in the storage of some 40,000 tonnes a − 1 of sediment which would also bury about 800 tonnes a − 1 of C org and 40 tonnes a − 1 of N org . Particulate Contaminant P burial would be around 25 tonnes a − 1 along with ~ 6 tonnes a − 1 Contaminant Zn, 3 tonnes a − 1 Contaminant Pb, and ~ 1 tonnes a − 1 Contaminant As and Cu. The study also shows that reclamation activities in the outer estuary since the mid-1700s has prevented, in total, the deposition of about 10 million tonnes of sediment, along with 320,000 tonnes of C org and 16,000 tonnes of N org . The study provides a mid-1990s baseline against which future measurements at the site can determine changes in burial fluxes and improvement or deterioration in Contaminant metal contents of the sediments. The data are directly relevant for local managed realignment sites but also broadly indicative for sites generally on the European North Sea Coast.
Julian E. Andrews - One of the best experts on this subject based on the ideXlab platform.
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Historical storage budgets of organic carbon, nutrient and Contaminant elements in saltmarsh sediments: biogeochemical context for managed realignment, Humber Estuary, UK.
The Science of the total environment, 2008Co-Authors: Julian E. Andrews, G Samways, G B ShimmieldAbstract:Biogeochemical data from Welwick marsh (Humber Estuary, UK), an actively accreting saltmarsh, provides a decadal-centennial-scale natural analogue for likely future biogeochemical storage effects of managed realignment sites accreting either intertidal muds or saltmarsh. Marsh topographic profiles and progradation history from aerial photographs were combined with (137)Cs and niobium contamination history to establish and verify chronology and sediment mass accumulation. These data, combined with down-core measurements of Particulate organic carbon (C(org)), organic nitrogen (N(org)), particle reactive phosphorus and selected Contaminant metal (Zn, Pb, Cu, As and Nb) contents were then used to calculate sediment and chemical storage terms and to quantify changes in these over time. These data are used to help predict likely future biogeochemical storage changes at managed realignment sites in the estuary. The net effect of returning some 26 km(2) of reclaimed land to intertidal environments now (about 25% of the maximum possible realignment storage identified for the estuary) could result in the storage of some 40,000 tonnes a(-1) of sediment which would also bury about 800 tonnes a(-1) of C(org) and 40 tonnes a(-1) of N(org). Particulate Contaminant P burial would be around 25 tonnes a(-1) along with approximately 6 tonnes a(-1) Contaminant Zn, 3 tonnes a(-1) Contaminant Pb, and approximately 1 tonnes a(-1) Contaminant As and Cu. The study also shows that reclamation activities in the outer estuary since the mid-1700s has prevented, in total, the deposition of about 10 million tonnes of sediment, along with 320,000 tonnes of C(org) and 16,000 tonnes of N(org). The study provides a mid-1990s baseline against which future measurements at the site can determine changes in burial fluxes and improvement or deterioration in Contaminant metal contents of the sediments. The data are directly relevant for local managed realignment sites but also broadly indicative for sites generally on the European North Sea Coast.
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Historical storage budgets of organic carbon, nutrient and Contaminant elements in saltmarsh sediments: Biogeochemical context for managed realignment, Humber Estuary, UK
Science of The Total Environment, 2008Co-Authors: Julian E. Andrews, G Samways, G B ShimmieldAbstract:Abstract Biogeochemical data from Welwick marsh (Humber Estuary, UK), an actively accreting saltmarsh, provides a decadal–centennial-scale natural analogue for likely future biogeochemical storage effects of managed realignment sites accreting either intertidal muds or saltmarsh. Marsh topographic profiles and progradation history from aerial photographs were combined with 137 Cs and niobium contamination history to establish and verify chronology and sediment mass accumulation. These data, combined with down-core measurements of Particulate organic carbon (C org ), organic nitrogen (N org ), particle reactive phosphorus and selected Contaminant metal (Zn, Pb, Cu, As and Nb) contents were then used to calculate sediment and chemical storage terms and to quantify changes in these over time. These data are used to help predict likely future biogeochemical storage changes at managed realignment sites in the estuary. The net effect of returning some 26 km 2 of reclaimed land to intertidal environments now (about 25% of the maximum possible realignment storage identified for the estuary) could result in the storage of some 40,000 tonnes a − 1 of sediment which would also bury about 800 tonnes a − 1 of C org and 40 tonnes a − 1 of N org . Particulate Contaminant P burial would be around 25 tonnes a − 1 along with ~ 6 tonnes a − 1 Contaminant Zn, 3 tonnes a − 1 Contaminant Pb, and ~ 1 tonnes a − 1 Contaminant As and Cu. The study also shows that reclamation activities in the outer estuary since the mid-1700s has prevented, in total, the deposition of about 10 million tonnes of sediment, along with 320,000 tonnes of C org and 16,000 tonnes of N org . The study provides a mid-1990s baseline against which future measurements at the site can determine changes in burial fluxes and improvement or deterioration in Contaminant metal contents of the sediments. The data are directly relevant for local managed realignment sites but also broadly indicative for sites generally on the European North Sea Coast.
G Samways - One of the best experts on this subject based on the ideXlab platform.
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Historical storage budgets of organic carbon, nutrient and Contaminant elements in saltmarsh sediments: biogeochemical context for managed realignment, Humber Estuary, UK.
The Science of the total environment, 2008Co-Authors: Julian E. Andrews, G Samways, G B ShimmieldAbstract:Biogeochemical data from Welwick marsh (Humber Estuary, UK), an actively accreting saltmarsh, provides a decadal-centennial-scale natural analogue for likely future biogeochemical storage effects of managed realignment sites accreting either intertidal muds or saltmarsh. Marsh topographic profiles and progradation history from aerial photographs were combined with (137)Cs and niobium contamination history to establish and verify chronology and sediment mass accumulation. These data, combined with down-core measurements of Particulate organic carbon (C(org)), organic nitrogen (N(org)), particle reactive phosphorus and selected Contaminant metal (Zn, Pb, Cu, As and Nb) contents were then used to calculate sediment and chemical storage terms and to quantify changes in these over time. These data are used to help predict likely future biogeochemical storage changes at managed realignment sites in the estuary. The net effect of returning some 26 km(2) of reclaimed land to intertidal environments now (about 25% of the maximum possible realignment storage identified for the estuary) could result in the storage of some 40,000 tonnes a(-1) of sediment which would also bury about 800 tonnes a(-1) of C(org) and 40 tonnes a(-1) of N(org). Particulate Contaminant P burial would be around 25 tonnes a(-1) along with approximately 6 tonnes a(-1) Contaminant Zn, 3 tonnes a(-1) Contaminant Pb, and approximately 1 tonnes a(-1) Contaminant As and Cu. The study also shows that reclamation activities in the outer estuary since the mid-1700s has prevented, in total, the deposition of about 10 million tonnes of sediment, along with 320,000 tonnes of C(org) and 16,000 tonnes of N(org). The study provides a mid-1990s baseline against which future measurements at the site can determine changes in burial fluxes and improvement or deterioration in Contaminant metal contents of the sediments. The data are directly relevant for local managed realignment sites but also broadly indicative for sites generally on the European North Sea Coast.
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Historical storage budgets of organic carbon, nutrient and Contaminant elements in saltmarsh sediments: Biogeochemical context for managed realignment, Humber Estuary, UK
Science of The Total Environment, 2008Co-Authors: Julian E. Andrews, G Samways, G B ShimmieldAbstract:Abstract Biogeochemical data from Welwick marsh (Humber Estuary, UK), an actively accreting saltmarsh, provides a decadal–centennial-scale natural analogue for likely future biogeochemical storage effects of managed realignment sites accreting either intertidal muds or saltmarsh. Marsh topographic profiles and progradation history from aerial photographs were combined with 137 Cs and niobium contamination history to establish and verify chronology and sediment mass accumulation. These data, combined with down-core measurements of Particulate organic carbon (C org ), organic nitrogen (N org ), particle reactive phosphorus and selected Contaminant metal (Zn, Pb, Cu, As and Nb) contents were then used to calculate sediment and chemical storage terms and to quantify changes in these over time. These data are used to help predict likely future biogeochemical storage changes at managed realignment sites in the estuary. The net effect of returning some 26 km 2 of reclaimed land to intertidal environments now (about 25% of the maximum possible realignment storage identified for the estuary) could result in the storage of some 40,000 tonnes a − 1 of sediment which would also bury about 800 tonnes a − 1 of C org and 40 tonnes a − 1 of N org . Particulate Contaminant P burial would be around 25 tonnes a − 1 along with ~ 6 tonnes a − 1 Contaminant Zn, 3 tonnes a − 1 Contaminant Pb, and ~ 1 tonnes a − 1 Contaminant As and Cu. The study also shows that reclamation activities in the outer estuary since the mid-1700s has prevented, in total, the deposition of about 10 million tonnes of sediment, along with 320,000 tonnes of C org and 16,000 tonnes of N org . The study provides a mid-1990s baseline against which future measurements at the site can determine changes in burial fluxes and improvement or deterioration in Contaminant metal contents of the sediments. The data are directly relevant for local managed realignment sites but also broadly indicative for sites generally on the European North Sea Coast.
Marina Coquery - One of the best experts on this subject based on the ideXlab platform.
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Sampling of suspended Particulate matter using particle traps in the Rhône River: Relevance and representativeness for the monitoring of Contaminants
Science of the Total Environment, 2018Co-Authors: M. Masson, M. Launay, H. Angot, C. Le Bescond, A. Dabrin, Cecile Miege, J. Le Coz, Marina CoqueryAbstract:Monitoring hydrophobic Contaminants in surface freshwaters requires measuring Contaminant concentrations in the Particulate fraction (sediment or suspended Particulate matter, SPM) of the water column. Particle traps (PTs) have been recently developed to sample SPM as cost-efficient, easy to operate and time-integrative tools. But the representativeness of SPM collected with PTs is not fully understood, notably in terms of grain size distribution and Particulate organic carbon (POC) content, which could both skew Particulate Contaminant concentrations. The aim of this study was to evaluate the representativeness of SPM characteristics (i.e. grain size distribution and POC content) and associated Contaminants (i.e. polychlorinated biphenyls, PCBs; mercury, Hg) in samples collected in a large river using PTs for differing hydrological conditions. Samples collected using PTs (n = 74) were compared with samples collected during the same time period by continuous flow centrifugation (CFC). The grain size distribution of PT samples shifted with increasing water discharge: the proportion of very fine silts (2-6 µm) decreased while that of coarse silts (27-74 µm) increased. Regardless of water discharge, POC contents were different likely due to integration by PT of high POC-content phytoplankton blooms or low POC-content flood events. Differences in PCBs and Hg concentrations were usually within the range of analytical uncertainties and could not be related to grain size or POC content shifts. Occasional Hg-enriched inputs may have led to higher Hg concentrations in a few PT samples (n = 4) which highlights the time-integrative capacity of the PTs. The differences of annual Hg and PCB fluxes calculated either from PT samples or CFC samples were generally below 20%. Despite some inherent limitations (e.g. grain size distribution bias), our findings suggest that PT sampling is a valuable technique to assess reliable spatial and temporal trends of Particulate Contaminants such as PCBs and Hg within a river monitoring network.
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Particulate Contaminant fluxes in the Upper Rhône River
2012Co-Authors: M. Launay, H. Angot, Marina Coquery, Jérôme Le CozAbstract:Suspended Particulate matters (SPM) have been recognized as the main way of transport for the hydrophobic Contaminants. Estimating Particulate Contaminant fluxes is thus of huge interest for waterquality managers in order to identify sources, transport and fate of Contaminants at the river basin scale, and to plan remediation measures. The Particulate Contaminant flux across a river section is the product of the water discharge, the SPM concentration and the Contaminant content adsorbed on particles. In order to evaluate Particulate fluxes of PCBs and Hg with minimal uncertainty and to investigate the spatio-temporal variability of these fluxes, a dedicated monitoring network was set up in September 2011 on the Upper Rhône River (France), and on the outlets of its main tributaries. The monitoring strategy relies on fortnightly measurements of Contaminant concentrations and a specific monitoring of flood events. In order to collect a sufficient amount of SPM to allow for Contaminant analysis (PCBs, Hg), appropriate centrifugation and filtration devices were deployed. This study highlighted that for PCBs and Hg, SPM concentration monitoring is essential during flood events to avoid an underestimation of fluxes. Indeed, SPM concentration appeared to be the most influencing parameter of the flux assessment, as it varied from 1 to 1000 mg/L between base-flow and flood periods. Nevertheless, Contaminant concentrations should be accurately studied during hydrological events as they appeared to vary between base-flow and sediment-laden events.
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Particulate Contaminant analysis: assessment and comparison of sampling techniques
2011Co-Authors: H. Angot, M. Launay, Jérôme Le Coz, Marina CoqueryAbstract:The European Water Framework Directive came into force in 2000, taking the 1976 Barcelona Convention into account and thus encouraging the contracting parties to evaluate pollution discharge to the Mediterranean Sea. Under the umbrella of the Rhone Sediment Observatory a monitoring station was set up upstream from Lyon in order to measure hydrophobic organic compounds and mercury contents of particles and to evaluate fluxes. To analyse those various Contaminants several grams of dried suspended Particulate matter (SPM) are required – which can be challenging considering low SPM levels in the Rhone river during base-flow regime. To face that problem several sampling techniques have been implemented: manual or automatic sampling, a continuous centrifuge running during several hours and an integrative sediment trap. For the sake of data homogeneity, we must assess and compare these different sampling techniques. The particle size distribution analysis of SPM sampled manually in the Rhone river showed two main peaks: one around 0.25 µm (10% volume) and another around 8 to 15 µm (90% volume). In contrast, the particle size distribution analysis of SPM collected with the continuous centrifuge and the sediment trap highlighted that finest particles were not successfully sampled. These results were confirmed by detectable SPM concentrations for water collected at the outlet of the continuous centrifuge and of the sediment trap. Thus, we investigated SPM Contaminant contents according to the particle size classes. Particulate mercury analysis revealed that finest particles are the most contaminated ones. Therefore, all Particulate Contaminant contents should be normalized using particle size distribution data especially when comparisons are needed between Contaminants content of particles sampled with different techniques, or sampled in bed deposits.
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Assessing Particulate Contaminant fluxes throughout river networks and the associated uncertainties
2011Co-Authors: M. Launay, H. Angot, Jérôme Le Coz, L. Roux, Marina CoqueryAbstract:The Particulate Contaminant flux (φ) across a river section is the product of the discharge (Q), the suspended Particulate matter concentration (Cs) and the content in Contaminant adsorbed on the particles (Ci.) High temporal resolution sampling of Q and Cs can provide continuous time series with a controlled uncertainty for both parameters. In contrast, Ci measurements are often infrequent, due to analysis costs and sampling difficulties, resulting in a larger uncertainty in the flux estimation. The influence of the temporal sampling of Ci was studied using a large data set on particles content for many Contaminants collected 4 times per year from 2000 to 2009 at 17 sites throughout the Rhône River catchment by the regional water authority. About 300 individual molecules were analysed, however many of them were never quantified. Information about the molecule hydrophobicity and comparison with data collected in the liquid phase may allow to optimize the number of analysis. Then we studied discontinuity over time of the Ci values for some Contaminants and highlighted changes in extraction protocols and reported limits of quantification, that were linked with a change of the analytical laboratory. Intercomparison exercises between laboratories and a complete documentation on analytical methods and quality control results are therefore of utmost importance. Finally, we observed that events with the highest Cs values were unsurveyed, which probably leads to an underestimation of the Ci variations. Thus extrapolation of Ci can lead to huge uncertainties on calculated fluxes for the most contributing events. Therefore, the sampling effort should be focused on the most sediment-laden events, relying on an automatic sampler, to estimate Ci variability with the hydrological cycle.
M. Launay - One of the best experts on this subject based on the ideXlab platform.
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Sampling of suspended Particulate matter using particle traps in the Rhône River: Relevance and representativeness for the monitoring of Contaminants
Science of the Total Environment, 2018Co-Authors: M. Masson, M. Launay, H. Angot, C. Le Bescond, A. Dabrin, Cecile Miege, J. Le Coz, Marina CoqueryAbstract:Monitoring hydrophobic Contaminants in surface freshwaters requires measuring Contaminant concentrations in the Particulate fraction (sediment or suspended Particulate matter, SPM) of the water column. Particle traps (PTs) have been recently developed to sample SPM as cost-efficient, easy to operate and time-integrative tools. But the representativeness of SPM collected with PTs is not fully understood, notably in terms of grain size distribution and Particulate organic carbon (POC) content, which could both skew Particulate Contaminant concentrations. The aim of this study was to evaluate the representativeness of SPM characteristics (i.e. grain size distribution and POC content) and associated Contaminants (i.e. polychlorinated biphenyls, PCBs; mercury, Hg) in samples collected in a large river using PTs for differing hydrological conditions. Samples collected using PTs (n = 74) were compared with samples collected during the same time period by continuous flow centrifugation (CFC). The grain size distribution of PT samples shifted with increasing water discharge: the proportion of very fine silts (2-6 µm) decreased while that of coarse silts (27-74 µm) increased. Regardless of water discharge, POC contents were different likely due to integration by PT of high POC-content phytoplankton blooms or low POC-content flood events. Differences in PCBs and Hg concentrations were usually within the range of analytical uncertainties and could not be related to grain size or POC content shifts. Occasional Hg-enriched inputs may have led to higher Hg concentrations in a few PT samples (n = 4) which highlights the time-integrative capacity of the PTs. The differences of annual Hg and PCB fluxes calculated either from PT samples or CFC samples were generally below 20%. Despite some inherent limitations (e.g. grain size distribution bias), our findings suggest that PT sampling is a valuable technique to assess reliable spatial and temporal trends of Particulate Contaminants such as PCBs and Hg within a river monitoring network.
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Particulate Contaminant fluxes in the Upper Rhône River
2012Co-Authors: M. Launay, H. Angot, Marina Coquery, Jérôme Le CozAbstract:Suspended Particulate matters (SPM) have been recognized as the main way of transport for the hydrophobic Contaminants. Estimating Particulate Contaminant fluxes is thus of huge interest for waterquality managers in order to identify sources, transport and fate of Contaminants at the river basin scale, and to plan remediation measures. The Particulate Contaminant flux across a river section is the product of the water discharge, the SPM concentration and the Contaminant content adsorbed on particles. In order to evaluate Particulate fluxes of PCBs and Hg with minimal uncertainty and to investigate the spatio-temporal variability of these fluxes, a dedicated monitoring network was set up in September 2011 on the Upper Rhône River (France), and on the outlets of its main tributaries. The monitoring strategy relies on fortnightly measurements of Contaminant concentrations and a specific monitoring of flood events. In order to collect a sufficient amount of SPM to allow for Contaminant analysis (PCBs, Hg), appropriate centrifugation and filtration devices were deployed. This study highlighted that for PCBs and Hg, SPM concentration monitoring is essential during flood events to avoid an underestimation of fluxes. Indeed, SPM concentration appeared to be the most influencing parameter of the flux assessment, as it varied from 1 to 1000 mg/L between base-flow and flood periods. Nevertheless, Contaminant concentrations should be accurately studied during hydrological events as they appeared to vary between base-flow and sediment-laden events.
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Particulate Contaminant analysis: assessment and comparison of sampling techniques
2011Co-Authors: H. Angot, M. Launay, Jérôme Le Coz, Marina CoqueryAbstract:The European Water Framework Directive came into force in 2000, taking the 1976 Barcelona Convention into account and thus encouraging the contracting parties to evaluate pollution discharge to the Mediterranean Sea. Under the umbrella of the Rhone Sediment Observatory a monitoring station was set up upstream from Lyon in order to measure hydrophobic organic compounds and mercury contents of particles and to evaluate fluxes. To analyse those various Contaminants several grams of dried suspended Particulate matter (SPM) are required – which can be challenging considering low SPM levels in the Rhone river during base-flow regime. To face that problem several sampling techniques have been implemented: manual or automatic sampling, a continuous centrifuge running during several hours and an integrative sediment trap. For the sake of data homogeneity, we must assess and compare these different sampling techniques. The particle size distribution analysis of SPM sampled manually in the Rhone river showed two main peaks: one around 0.25 µm (10% volume) and another around 8 to 15 µm (90% volume). In contrast, the particle size distribution analysis of SPM collected with the continuous centrifuge and the sediment trap highlighted that finest particles were not successfully sampled. These results were confirmed by detectable SPM concentrations for water collected at the outlet of the continuous centrifuge and of the sediment trap. Thus, we investigated SPM Contaminant contents according to the particle size classes. Particulate mercury analysis revealed that finest particles are the most contaminated ones. Therefore, all Particulate Contaminant contents should be normalized using particle size distribution data especially when comparisons are needed between Contaminants content of particles sampled with different techniques, or sampled in bed deposits.
-
Assessing Particulate Contaminant fluxes throughout river networks and the associated uncertainties
2011Co-Authors: M. Launay, H. Angot, Jérôme Le Coz, L. Roux, Marina CoqueryAbstract:The Particulate Contaminant flux (φ) across a river section is the product of the discharge (Q), the suspended Particulate matter concentration (Cs) and the content in Contaminant adsorbed on the particles (Ci.) High temporal resolution sampling of Q and Cs can provide continuous time series with a controlled uncertainty for both parameters. In contrast, Ci measurements are often infrequent, due to analysis costs and sampling difficulties, resulting in a larger uncertainty in the flux estimation. The influence of the temporal sampling of Ci was studied using a large data set on particles content for many Contaminants collected 4 times per year from 2000 to 2009 at 17 sites throughout the Rhône River catchment by the regional water authority. About 300 individual molecules were analysed, however many of them were never quantified. Information about the molecule hydrophobicity and comparison with data collected in the liquid phase may allow to optimize the number of analysis. Then we studied discontinuity over time of the Ci values for some Contaminants and highlighted changes in extraction protocols and reported limits of quantification, that were linked with a change of the analytical laboratory. Intercomparison exercises between laboratories and a complete documentation on analytical methods and quality control results are therefore of utmost importance. Finally, we observed that events with the highest Cs values were unsurveyed, which probably leads to an underestimation of the Ci variations. Thus extrapolation of Ci can lead to huge uncertainties on calculated fluxes for the most contributing events. Therefore, the sampling effort should be focused on the most sediment-laden events, relying on an automatic sampler, to estimate Ci variability with the hydrological cycle.