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i abstract we are a group of 8 students from beaussier high school and we have been working on sediments in seyne but what is sediments in seyne it is a scientific and social project indeed we wanted to know why the harbour of our city la seyne sur mer on the coast of the mediterranean sea in the south of france was not being renovated to know the reason we had a partnership with the protee laboratory a laboratory of the south university toulonvar which helped us on the material level as on the knowledge one after some research newspapers we discovered that the sediments they compose the seafloor were the problem of the delay of the building of this harbour because of the pollutants present in these sediments this pollution is due to several factors such as the scuttling of the fleet during world war 2 the boat cemetery present in the harbour and the fact that people consider the harbour as an open dump they throw all kinds of things in the sea we made some experiments in toulon university to know how these sediments released their pollutants in the seawater by concentrating on the carbon because it was easier for us to make experiments with it as the protee laboratory researchers had told us that the pollutants could be released about the same way we made some calculations for the lead a pollutant and we found out that the releasing concentration of these sediments for the lead was 77 times higher than the normal one so we concluded that we had to clean the sediments more than a hundred times the harbour needs a dredging that s why we tried to find out solutions for a clean dredging and we worked on two potential solutions first solution a geotextile which prevents pollutants from being scattered in the seawater during a dredging second a chelating resin that can be included in a geotextile which is capable of confining pollutants in this resin thanks to our partnership with the bay contract we will be allowed to participate in the dredging and in the following analysis of seawater next november finally to inform the population of the city of la seyne sur mer we organized an awareness campaign we appeared in several newspapers of our city also on the website of our academy the academy of nice we created a group on facebook as well as our own website where we detailed all our experiments and research we also created a gazette where we explained with simple words why the harbour wasn t renovated and the contamination of the seafloor this gazette is given in all public places schools sports hall town council -1-

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ii contents iabstract ii contents iii list of abbreviations and acronyms iv acknowledgements v sediments in seyne 1 introduction history of the project 2 methodology and results how do sediments release in the seawater 3 discussion solutions 4 conclusion 5 communication awareness campaign vi bibliography iii list of abbreviations and acronyms · cartochim mapping of sedimentation rate and processes · ifremer french research institute for exploration of the sea · le grenelle de la mer conference on environmental issues · protee transfer and exchange processes in environment · rocch network for chemical contaminants observatory · sedimard contaminated and dredged sea sediments · up ultra pure · ustv university of south toulon var iv acknowledgements we are grateful to the laboratory protee of the ustv which allowed us to make our experiments and analysis on their laboratory machines to the regional council of paca region provence alpes côte d azur which helped us financially to the town of la seyne which paid for printing the gazette and to the bay contract for its partnership concerning the monitoring of the dredging and finally to laseyne.info a local media which broadcast the results and the information about our project -2-

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v sediments in seyne insane 1 introduction history of the project we are a group of high school students preparing a scientific a-level living in la seyne sur mer on the mediterranean shore in the largest french roadstead of toulon which is also the most important navy base in france the current harbour of our city has been the subject of renovation projects it implies the building of some entertainment places shops cinemas restaurants but these projects have always been delayed because of the contamination by sediments of these places to build them it would be necessary to dredge the seafloor and so to move the sediments if we don t take measures before the dredging the pollutants present in the seafloor will be released in the seawater and that will imply great pollution · the composition of the sediments a sediment is composed of clay and fine sand whose cohesion is ensured by a ciment pore water and some heavy metals such as lead copper mercury are present in these sediments these sediments constitute the seafloor an important thing is that sedimentation is a natural process and it increases by 2mm per year drawing of the composition of the sediments -3-

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· some works made by french institutes some french institutes specialized in the contamination of these sediments carried out research for example ifremer a french institute made a mapping which describes the toxicity of the sediments of the harbour of toulon and so for the sediments we can see thanks to the graduation on the right that the bluer it is the more polluted it is in red this is a seawall so the harbour is semi-closed and there is not current we conclude that the toxicity of the sediments is not regulated the toxicity of the sediments in the toulon roads ifremer ­ laboratory ler ­ activity report 2009 to know when dredging is allowed a french organization le grenelle de la mer created three dredging levels · the first is level n1 for this one the operation of dredging and the offshore piling of the sediments are allowed because these sediments are considered as clean wastes · the second is the level between n1 and n2 where some studies are required to know the toxicity of the sediments · and finally the third level n2 when the dredging and the offshore piling of the sediments are forbidden because these sediments are considered as toxic wastes a table was made by sedimard a french institute in 54 harbours of our department the var in white it is level n1 in yellow the level between n1 and n2 in orange level n2 and finally in red it is beyond level n2 this table shows us that it is the navy base which is the most polluted in copper mercury lead and tbt for the tbt it is due to the antifouling paint effect that is renewed every year and for the others it is due to the scuttling of the fleet during the second world war the boat cemetery present in the harbour and also the fact that people consider the harbour of la seyne sur mer as an open dump -4-

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sedimard diagnosis of the measures taken in 54 harbours of the var three graphics also made by sedimard assert what we said about the contamination of the seafloor in this navy base it breaks records in mercury copper tbt pcb lead and zinc these measures were taken after some experiments and develop protocols on dry sediments graphics of the toxicity of the navy base -5-

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finally three mappings were made by ifremer on several pollutants and we noticed the toulon roads were highly contaminated in pcb lead and mercury these measures were taken after experiments were made on mussels to know if they died rapidly depending on the pollutants concentration for it is well known that mussels are natural water filters and so store inside all the water pollutants that they filter mappings of the pollution of the toulon roads in pcb tbt and mercury ifremer rocch network for chemical contaminants observatory 2 methodology and results how do sediments release in the seawater we made experiments and analysis in the protee laboratory to answer to our scientific problematic how do sediments release in the seawater we don t have such analysis machines in our high school that is why we are in partnership with the university of toulon our experiments were validated by the researchers who supervised our works -6-

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· step 1 before beginning some experiments the national navy made a sampling called in this situation a coring we used the 2 cm top portion of one which represents the last 10 years of sedimentation at that moment we could start the experiments patrick in front of the machine cutting the coring of sediments · step 2 our goal was to simulate and be closer to reality for this we took 8 flasks salty waters ph 6/8/10 and ultra-pure water in which we introduced different sea or fresh waters and added 1.0 g of sediments in 50ml let us explain our protocol 4 flasks were stirred for 2 hrs in order to simulate boat which just pssed over or a propeller which stirread the sediments actually it represents a short stirring 4 other flasks were stirred for 1 night which represents a long stirring so it could be in reality a storm even a dredging leo pipette filling to prepare our 4 different solutions salty waters · step 3 after that experiment we centrifuged with a machine which consists in separating the pellet the sediments and the supernatant in the sea it represents the water just above the sediments kenza and julia pipette filling the supernatant -7-

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· step 4 when it was finished we took the supernatant and we eventually analyzed it with two different methods the first one is with a uv spectroscope because we know thanks to the beer lambert law that the absorbance is proportional to the concentration of the solutions we measured the dissolved carbon with a second machine samples of supernatant and the machine measuring dissolved carbon · step 5 after some analysis we got the following results from the spectroscopy we have several graphs but we just chose to show you the one that best illustrates our analysis spectroscopy the absorbance versus the wavelength nm -8-

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in this first graph we can see 2 curves the blue curve represents the up water stirred for 2hrs and the pink one represents the up water stirred for 1 night so it is the same water but not the same duration of stirring we observe that there is an important difference of concentration between the 2 curves so we suppose that time is a factor influencing the releasing process spectroscopy the absorbance versus the wavelength nm in the second graph we can see 4 curves representing 4 different waters which underwent the same time of stirring the first curve in yellow represents the up water stirred for 2hrs and the last 3curves represent the different salty waters with different ph balances by analysing this graph we notice that without the time factor we haven t got a huge difference between the different salty waters except for one the ph8 it can be explained by the fact that this ph corresponds to the sea ph about 8.5 but we can notice that the difference of concentration between the fresh and the salty waters is important from the other machine which measures dissolved carbon concentration mg.l-1 of different solutions in dissolved carbon -9-

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there aren t differences between the different ph but we can notice the influence of time here too because the concentration is really not the same between the solutions stirred 2hrs and the ones stirred 1night we can also see a difference of concentration between the up water and the salty waters and if time influences it is normal that the initial supernatant is extremely high in its concentration because it had been in contact with the sediments for about 10 years thanks to all these results we can conclude that the ph doesn t influence the result the sediments free more carbon in fresh water than in sea water so it makes us think that salinity and rain water are very important in the releasing process time is a very important factor the longer sediments stay in water the more carbon they free · step 6 we made other manipulations in order to know the percentage of particle carbon in the sediments for this we took a piece of sediments of our coring we centrifuged it took the pellet and put it into a drying oven we got it back crushed it and put the dry residue into a machine named solid simple module thanks to this manipulation and the results we can conclude that the sediments are composed of 9.5 of mass carbon it means that 1.0g of dry sediments is composed of 95mg of particle carbon so we introduced 1.0 g of dry sediments in 50ml of up water and we obtained a dissolved concentration of 17 mg.l-1 that is to say 170.050 0.85 mg of dissolved carbon we know then that about 1 of the imprisoned carbon of the sediments is released into the water fatima and laura taking a sample of sediments to measure the percentage of carbon inside 10 -

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it s important to know that if we measured the dissolved carbon it s because it was the easiest experiment to do but we know that the other elements such as tbt pcb or heavy metals behave the same way according toprotee researchers they advised us against working on trace metals because of the very complex methodology and notions for high school students so 1 of carbon is liberated but we wanted to know if 1 is more or less concentrated than the normal concentration of the seawater we took the example of lead during a dredging we know that there are 10g of sediments in 1.0l of sea water according to protee researchers we also know that there are 478 mg of lead per kg of sediments thanks to sedimard that s to say 0.478 mg of lead in 1.0l of seawater containing the sediments for 1 liberated mass concentration 0.478.10-3/100 4.7810-6 g.l-1 molar concentration 4.7810-6 207.2 23 nmol.l-1 thanks to the information of the protee laboratory the measures of the lead concentration realised in la baie du lazaret is 0.30 nmol.l-1 and it is the highest limit allowing aquafarming 23/0.30 77 which means that our result is about 77 times higher in conclusion we can say that the releasing potential of sediments is very important because to eliminate all the carbon present in the sediment we would have to repeat the experiment more than one hundred times 11 -

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3 discussion solutions after our experiments we wondered if there were solutions to dredge without polluting nowadays we can use several solutions according to the specificities of the area to dredge each case has got its differences the sediments are not polluted the same way this is why cartochim and the bay contract in partnership with the navy and the protee laboratory made a chemical inventory of the bay by making corings and by mapping the different concentrations for the different pollutants · what would happen if we did nothing our experiments showed that if the sediments are moved by a boat or a storm they can potentially release pollutants but none of them behave exactly the same way if we are able to quantify the pollution of the sediments it is more difficult to quantify the streaming flows that generate a contamination of the ecosystem so it is difficult to know if a sediment even if it is heavily polluted is potentially dangerous or not this is why some studies are conducted by the laboratory protee to know more about the behaviour of the different pollutants and particularly about the desorption of heavy metals · why are we sometimes forced to carry out a dredging a dredging is sometimes required especially in the roadstead of toulon where thirteen new frigates will arrive in 2013 but their keels are too long and the thickness of the sediments would prevent them from sailing the dredging planned for next november will allow to gain in bathymetry in some places in the roadstead · the geotextile a clean dredging solution a dredging is very expensive because of the remediation of sediments and the precautions to limit the transfer of pollutants there is a technique to restrict the remobilization of pollutants in seawater the geotextile that is a huge cover put over the sediments this is a porous membrane which allows water to pass through but not the particles in this way the sediments are isolated and the pollutants cannot be released anymore in the water dredging consists in pumping the sediments through an opening in the geotextile and the wasted water towards a system of treatment 12 -

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the action of the geotextile · what could happen to the dredged sediments what is expensive is not the dredging itself it is to find what to do with the polluted sediments if they exceed the level n2 they can be placed in a type 1 dump where they are buried with the final wastes which are the most toxic 1300 euros per ton of sediment to bury but sediments can also be used if the mass of polluted sediment is reduced by a screening to get clean sand it can be used as filling for roads to produce concrete or to bail beaches this would reduce the mass of sediments to bury thus the price to pay the polluted part of the sediments can enter into the composition of industrial cement because it contains aluminium silica and iron which then become very useful another solution is to give the sediments to the platform of research and treatment sedimard · what is sedimard the project sedimard has lasted for three years it means contaminated and dredged sea sediments it was initiated by the general council of the var and led to the construction of a platform of treatment between la seyne and toulon there the sediments will be treated experimentally in order to find ways of valorisation or to make them less toxic 13 -

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if we did not need to win in bathymetry there would be physical chemical or biological solutions to eliminate the pollutants or to stop the fluxes without dredging · the other solutions the capping consists in putting sand on the sediments this way we hope to stop or to curve the fluxes between the sediments and the sea water but we are not sure that this method allows to stop completely the fluxes could we put sand to stop the fluxes the chelating resin is chemically reactive so it is capable of capturing heavy metals contained in the sediments and of preventing remobilization of pollutants this is possible thanks to the affinities between the components of the resin and the pollutants for example clays bind with heavy metals and charcoal with the organic contaminants but when we decide to use it we must predict when it will be saturated depending on the concentrations of pollutants and the ability of the resin this method s problem is that we have to take it off from the seawater when it is saturated and it is impossible with a resin we propose to adapt a geotextile membrane by confining a chelating resin between 2 layers of membrane like a mattress this solution already exists for road engineering but not in seawater with our solution there would be no problem to take the geotextile and the chelating resin out of the water the last solution we know is the bioremediation it implies to grow bioaccumulators plants which can capture heavy metals contained in the sediments 14 -

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