DETERMINATION OF ORGANIC POLLUTANT CONTENT BY INFRARED SPECTROMETRY IN NATURAL SOILS AND EXCAVATIONAL MATERIALS

Abstract

The present invention is a rapid method for determining the mass content of all organic pollutants contained in an excavated material from an infrared spectroscopic analysis of the excavated material.

Description

Technical field

[0001] The present disclosure relates to the field of characterization of natural soils and excavation materials, in particular extracted by tunneling, to determine their mass content of organic pollutants such as total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX. Prior art

[0002] During any construction on or in the ground, particularly during tunneling, the ground is developed by excavation. Quantities of excavated material are then extracted, depending on the scale and type of work. Typically, a tunnel boring machine used to excavate a tunnel during the construction of a metro line produces approximately 800 tonnes of excavated material per day.

[0003] The excavated materials thus extracted contain various chemical species. Some chemical species come from the composition of the rock or sand, and are then referred to as the matrix. Other chemical species are present in smaller quantities, and are then referred to as traces. When the traces are toxic, they are called pollutants. Some of these pollutants are, for example, hydrocarbons. There is endogenous pollution, originating from the geological environment of the sample, and pollution linked to local human activity, on the surface. These chemical species can represent a risk for the environment when the excavated materials are stored after being extracted. Before storing these excavated materials, it is therefore necessary to determine their contamination level. Determining this contamination level makes it possible to direct the materials into one of the three existing treatment processes.These three processing lines are as follows: . 1) Inert materials are stored for recovery, 2) Slightly contaminated materials are stored in specialized landfills (whose subsoil does not allow flow into groundwater), 3) Contaminated materials are sent to the recovery sector to recover the polluting elements.

[0004] The selection of the appropriate treatment process depends, among other things, on the mass content of organic pollutants in the excavated material. For example, the threshold values ​​for the maximum mass content of hydrocarbons to be respected are set by legislation. In France, this is Decision No. 2003 / 33 / EC of 19.12.2002 establishing criteria and procedures for the admission of waste to landfills and the decrees of 30.12.2002 on the storage of hazardous waste and of 12.12.2014 on the conditions for the admission of inert waste [...]. According to this Decision and these decrees, the limit values ​​for the mass content of hydrocarbons to be detected are among the most stringent in Europe. These limit values ​​are shown in Table 1 below. [Table 1] Organic pollutants to be detected ISDI limit value* ISDND limit value** ISDD*** limit value Mass content in mg / kg of dry matter Polycyclic Aromatic Hydrocarbons (PAHs) 50 100 500 Volatile Organic Compounds (VOCs) 30 000 50 000 60 000 Polychlorinated biphenyls (PCBs) 1 50 - Total Hydrocarbons (THC) 500 800 1 000 Benzene, Toluene, Ethylbenzene and Xylene (BTEX) 6 30 - ISDI: Inert Waste Storage Facility ISDND: Non-Hazardous Waste Storage Facility ISDD: Hazardous Waste Storage Facility * Annex II of the decree of 12.12.2014 ** Decision No. 2003 / 33 / EC of 19.12.2002 *** Annex 1 of the decree of 30.12.2002

[0005] If the mass content of each organic pollutant contained in the excavation material is lower than the ISDI limit value indicated in Table 1, then the excavation material is considered inert. It can then be stored in inert waste storage facilities in order to be recovered, for example as a construction material or for landscaping.

[0006] If the mass content of at least one of the organic pollutants contained in the excavation material is between the ISDI and ISDND limit values ​​indicated in Table 1, then the excavation material is considered to be slightly contaminated. It can then be stored in non-hazardous waste storage facilities.

[0007] If the mass content of at least one of the organic pollutants contained in the excavation material is between the ISDND and ISDD limit values ​​indicated in Table 1, then the excavation material is considered contaminated. It is then stored in hazardous waste storage facilities. It can be decontaminated there to recover and recycle the organic pollutants.

[0008] The procedure for determining the mass content of each organic pollutant in an excavation material is set by national standards. In France, these are the French standards NF EN ISO 16703 for total hydrocarbons, NF EN 17503 for polycyclic aromatic hydrocarbons, ISO 22155 for BTEX and volatile organic compounds and NF EN 17322 for polychlorinated biphenyls.

[0009] The procedures for determining the mass content of total hydrocarbons, polycyclic aromatic hydrocarbons, BTEX, volatile organic compounds and polychlorinated biphenyls present in an excavated material are identical but are very long. These procedures consist of a physicochemical analysis of the composition of the leachate obtained after a simulated leaching of the excavated material. According to the French standards mentioned above, a leaching (well-known water treatment that results in the dissolution of soluble species) of the excavated material is simulated for 24 hours at room temperature (20°C ± 5°C). Then the leachate (residual liquid from the leaching) is analyzed to determine the mass content of total hydrocarbons, polycyclic aromatic hydrocarbons, BTEX, volatile organic compounds and polychlorinated biphenyls present in said leachate.The mass content determined in the leachate is representative of the mass content of total hydrocarbons, polycyclic aromatic hydrocarbons, BTEX, volatile organic compounds and polychlorinated biphenyls present in the excavated material. The duration of these procedures is at least 48 hours. To this duration must also be added the time for transport to a laboratory external to the site of extraction of the excavated materials and the processing time for a total duration of seven days. During this long period, it is necessary to store the excavated materials extracted on construction sites which are very often located in geographical areas with very high constraints (urban areas, mountain valleys).

[0010] Surprisingly, the Applicant has found a method for quickly determining the mass content of all organic polluting elements included in an excavation material. Summary

[0011] A method for analyzing excavation material is proposed, comprising the following steps: a) analysis by infrared spectroscopy of a sample of an excavation material in a wave number range between 4000 cm -1< and 500 cm -1< , in particular between 3500 cm -1< and 600 cm -1< , more particularly between 3000 cm -1< and 650 cm -1< to obtain an infrared spectrum, b) determination of the mass content of organic pollutants in said sample from the infrared spectrum obtained in step a), the organic pollutants being chosen from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and combinations thereof.

[0012] Advantageously, step a) of the method of the present invention makes it possible to obtain an infrared spectrum which may comprise: absorption bands between 1630 cm -1< and 1680 cm -1< and around 1645 cm -1< which are specific to total hydrocarbons, absorption bands around 1450 cm-', 1500 cm-', 1580 cm -1< and 1600 cm -1< which are specific to polycyclic aromatic hydrocarbons, absorption bands between 3610 cm -1< and 3670 cm-', between 3200 cm -1< and 3400 cm -1< and around 1735 cm -1< which are specific to volatile organic compounds, absorption bands around 540 cm -1< and 760 cm -1< which are specific to polychlorinated biphenyls, and an absorption band between 1610 cm -1< and 1650 cm -1< which is specific to BTEX.

[0013] As indicated in Table 1 above, the mass contents of organic pollutants to be detected for the ISDI limit value are very low. In addition, it is commonly accepted that the low detection limit must be three times lower than the limit value to be detected. It is therefore necessary to be able to detect a mass content of PAHs of at least 16 mg / kg. Thanks to the wavenumber ranges indicated above, the analytical method makes it possible to reliably and reproducibly determine the low mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX present in the excavation material. Indeed, these wavenumber ranges do not overlap with the 2700 cm -1< - 3100 cm -1< range in which the specific band of water, an element very present in the excavation material, is detectable.

[0014] By determining the areas of one or more of these absorption bands and comparing it to a calibration curve previously obtained from the spectroscopic analysis of samples whose mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and / or BTEX are known, it is possible to precisely determine the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX in the sample of excavation material.

[0015] Advantageously, the method of the present invention makes it possible to simply, quickly, reliably and reproducibly determine the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX present in the excavation material.

[0016] In fact, infrared spectrometers are well-known, compact, reliable and robust devices that can be used on a construction site and can carry out step a) of analysis in a few seconds.

[0017] In addition, the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX present in the excavation material determined by the analysis method of the present invention are consistent with the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX present in the excavation material determined by the conventional procedure according to the standards in force.

[0018] A method for selecting a processing line for excavation materials is also proposed, comprising the following steps: c) comparison of the mass content of each organic pollutant determined by the analysis method as described above with a fixed limit value, d) selection of the treatment route according to the following criteria: if the mass content of each organic pollutant contained in the sample is lower than the fixed limit value then the material is considered inert (Routine 1), if the mass content of an organic pollutant is higher than the fixed limit value then the material is considered contaminated and can be stored in specialized landfills (Routine 2) or can be decontaminated (Routine 3).

[0019] The limit value set for each of the organic polluting elements may be set by a national or international legislative or regulatory text. This limit value set may be that indicated in Table 1 above. Brief description of the drawings

[0020] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which: Fig. 1

[0021] [ Fig. 1 ] shows an infrared spectrum of a sample of excavation material undergoing the analysis method according to the invention. Description of the embodiments

[0022] According to a first object of the invention, a method of analyzing an excavation material is proposed comprising the following steps: a) analysis by infrared spectroscopy of a sample of an excavation material in a wave number range between 4000 cm -1< and 500 cm-', in particular between 3500 cm -1< and 600 cm-', more particularly between 3000 cm -1< and 650 cm -1< to obtain an infrared spectrum, b) determination of the mass content of organic pollutants in said sample from the infrared spectrum obtained in step a), the organic pollutants being chosen from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and combinations thereof.

[0023] For the purposes of this application, "infrared spectroscopy" means a chemical analysis technique based on the absorption of light by most molecules in the infrared region of the electromagnetic spectrum and converting this absorption into molecular vibration. This absorption corresponds specifically to the bonds present in the molecule. With a spectrometer, this absorption of infrared radiation by the sample material is measured as a function of wavenumbers. The result is an infrared spectrum comprising one or more absorption bands specific to the molecules present in the sample analyzed. The absorption band may also be referred to as a peak in this application.

[0024] For the purposes of this application, "excavation material" means any material excavated during civil engineering or construction works, whether on the surface of the Earth, for example during excavations or foundation creation, or in the subsoil, for example during the digging of tunnels, caverns and galleries. Typically, excavation material includes: loose rocks such as gravels, sands, silts, clays and their mixtures; crushed rocks; materials from previous construction or contaminated sites such as landfills; or excavation sludge.

[0025] According to one embodiment, the excavation material is an excavation slurry.

[0026] Typically, excavation slurry can be produced by a tunnel boring machine excavating a tunnel during the construction of a subway line, a train line, a road.

[0027] According to a particular embodiment, the excavation mud is extracted from the Parisian subsoil.

[0028] In the present application, the organic pollutants are selected from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and combinations thereof.

[0029] For the purposes of this application, "total hydrocarbons", also referred to as HCT, designates a set of organic compounds originating from the distillation of petroleum and forming part of the family of persistent organic pollutants whose chain comprises between 10 and 40 carbon atoms. These compounds may be n-alkanes, iso-alkanes, cyclo-alkanes, alkyl-benzenes and / or alkylnaphthalenes.

[0030] For the purposes of this application, "polycyclic aromatic hydrocarbons", also referred to as PAH, designates a set of organic compounds consisting of carbon and hydrogen atoms and whose structure comprises at least two fused aromatic rings. Naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, bbenzo(b)fluoranthene, benzo(k)fluoranthene, benzopyrene (BaP), indeno(123) pyrene and dibenzo(a,h)anthracene are part of this set.

[0031] For the purposes of this application, "volatile organic compounds", also known as VOCs, designates organic compounds found in gaseous form in the Earth's atmosphere.

[0032] For the purposes of this application, "polychlorinated biphenyls", also noted or PCB, designates halogenated hydrocarbons, high molecular weight organochlorine aromatic compounds, derived from biphenyl.

[0033] For the purposes of this application, "BTEX" means a group of organic compounds which includes benzene, toluene, ethylbenzene and xylenes (mp-xylenes and o-xylene).

[0034] The excavation material used in step a) may have a dry matter content, or dryness, of 70% to 100%, in particular 90% to 100%, most particularly 99% to 99.99%.

[0035] Alternatively, the excavation material used in step a) may have a dry matter content, or dryness, of 70% to 100%, in particular 75% to 90%, most particularly 78% to 82%.

[0036] For the purposes of this application, the "dry matter content" is the ratio between the dry mass of excavation material and the mass of the excavation material before drying, the dry mass of the excavation material being measured after drying approximately 30 grams of excavation material for 30 minutes at 145°C.

[0037] Advantageously, using an excavation material with such a dry matter content makes it possible to obtain an infrared spectrum whose resolution allows the identification of absorption bands specific to organic pollutants.

[0038] Drying an excavation material is a classic step known to those skilled in the art. They will therefore know how to implement a drying step for the excavation material to obtain the dry matter content described above.

[0039] The excavation material used in step a) may have a particle size such that 35% by mass of the excavation material has a diameter of less than 63 µm, in particular 95% by mass of the excavation material has a diameter of less than 125 µm, and in particular 100% by mass of the excavation material has a diameter of less than 200 µm.

[0040] The particle size of the excavated material can be determined by sieving.

[0041] This particle size can be obtained by manual grinding or automatic grinding, in particular manual grinding, more particularly manual grinding in an agate mold. Manual grinding is advantageously suited to the disparity in hardness of the components of the excavation material.

[0042] Step b) of the analysis method may include the following sub-steps: b11) detection between 1600 cm -1< and 1700 cm -1< of an absorption band specific to total hydrocarbons in the infrared spectrum obtained in step a), b21) integration of the absorption band detected in step b11) to calculate an area, and b31) comparison of the area obtained in step b21) with a calibration curve to determine the mass content of total hydrocarbons in the excavation material.

[0043] Advantageously, the wavenumber range of sub-step b11) makes it possible to calculate, in a reproducible and precise manner, the area of ​​the absorption band specific to total hydrocarbons during step b21). From this area, it is then possible to determine, in a reproducible and precise manner, the mass content of total hydrocarbons in the excavation material during step b31).

[0044] These sub-steps b11) to b31) can make it possible to quickly, precisely and reproducibly determine the mass content of total hydrocarbons in the excavation material.

[0045] Step b) of the analysis method may, alternatively or additionally to sub-steps b11) to b31), comprise the following sub-steps: b12) detection between 1400 cm -1< and 1500 cm -1< of an absorption band specific to polycyclic aromatic hydrocarbons in the infrared spectrum obtained in step a), b22) integration of the absorption band detected in step b12) to calculate an area, and b32) comparison of the area obtained in step b22) with a calibration curve to determine the mass content of polycyclic aromatic hydrocarbons in the excavation material.

[0046] Advantageously, the wave number range of sub-step b12) makes it possible to calculate, in a reproducible and precise manner, the area of ​​the absorption band specific to polycyclic aromatic hydrocarbons during step b22). From this area, it is then possible to determine, in a reproducible and precise manner, the mass content of polycyclic aromatic hydrocarbons in the excavation material during step b32).

[0047] These sub-steps b12) to b32) can make it possible to quickly, precisely and reproducibly determine the mass content of polycyclic aromatic hydrocarbons in the excavation material.

[0048] Step b) of the analysis method may, alternatively or additionally to substeps b11) to b31) and b12) to b32), comprise the following substeps: b13) detection between 3300 cm -1< and 3400 cm -1< of an absorption band specific to volatile organic compounds in the infrared spectrum obtained in step a), b23) integration of the absorption band detected in step b13) to calculate an area, and b33) comparison of the area obtained in step b23) with a calibration curve to determine the mass content of volatile organic compounds in the excavation material.

[0049] Advantageously, the wave number range of sub-step b13) makes it possible to calculate, in a reproducible and precise manner, the area of ​​the absorption band specific to volatile organic compounds during step b23). From this area, it is then possible to determine, in a reproducible and precise manner, the mass content of volatile organic compounds in the excavation material during step b33).

[0050] These sub-steps b13) to b33) can make it possible to quickly, precisely and reproducibly determine the mass content of volatile organic compounds in the excavation material.

[0051] Step b) of the analysis method may, alternatively or additionally to substeps b11) to b31), b12) to b32) and b13) to b33) comprise the following substeps: b14) detection between 800 cm -1< and 500 cm -1< of one or two absorption bands specific to polychlorinated biphenyls in the infrared spectrum obtained in step a), b24) integration of the absorption bands detected in step b14) to calculate an area, and b34) comparison of the area obtained in step b24) with a calibration curve to determine the mass content of polychlorinated biphenyls in the excavation material.

[0052] Advantageously, the wavenumber range of sub-step b14) makes it possible to calculate, in a reproducible and precise manner, the area of ​​the absorption bands specific to polychlorinated biphenyls during step b24). From this area, it is then possible to determine, in a reproducible and precise manner, the mass content of polychlorinated biphenyls in the excavation material during step b34).

[0053] These sub-steps b14) to b34) can make it possible to quickly, precisely and reproducibly determine the mass content of polychlorinated biphenyls in the excavation material.

[0054] Step b) of the analysis method may, alternatively or additionally to substeps b11) to b31), b12) to b32), b13) to b33) and b14) to b34) comprise the following substeps: b15) detection between 1600 cm -1< and 1650 cm -1< of a BTEX-specific absorption band in the infrared spectrum obtained in step a), b25) integration of the absorption band detected in step b15) to calculate an area, and b35) comparison of the area obtained in step b25) with a calibration curve to determine the BTEX mass content of the excavation material.

[0055] Advantageously, the wavenumber range of sub-step b15) makes it possible to calculate, in a reproducible and precise manner, the area of ​​the BTEX-specific absorption band during step b25). From this area, it is then possible to determine, in a reproducible and precise manner, the BTEX mass content of the excavation material during step b35).

[0056] These sub-steps b15) to b35) can make it possible to quickly, precisely and reproducibly determine the BTEX mass content of the excavation material.

[0057] By accurately determining the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX in the excavated material using the analysis method of the present invention, it is possible to select the correct reprocessing route for an excavated material.

[0058] Thus, according to a second object of the invention, a method is proposed for selecting a process for reprocessing excavation materials comprising the following steps: c) comparison of the mass content of each organic pollutant determined by the analysis method as described above with a fixed limit value, d) selection of the treatment route according to the following criteria: if the mass content of each organic pollutant contained in the sample is lower than the fixed limit value then the material is considered inert (Routine 1), if the mass content of an organic pollutant is higher than the fixed limit value then the material is considered contaminated and can be stored in specialized landfills (Routine 2) or can be decontaminated (Routine 3).

[0059] In this selection method, the organic pollutants are the same as the organic pollutants in the analysis method, iethose selected from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and combinations thereof.

[0060] Typically, according to French legislation, the excavation material is considered inert if the mass content of each organic pollutant is lower than the ISDI limit value indicated in Table 1. This excavation material is then reusable, for example as a construction material or for landscaping (Sector 1).

[0061] Typically, according to French legislation, the excavation material is considered to be slightly contaminated if the mass content of an organic pollutant contained in said excavation material is between the ISDI and ISDND limit values ​​indicated in Table 1. This excavation material considered to be slightly contaminated is stored in specialized landfills such as non-hazardous waste storage facilities (Sector 2).

[0062] Typically, according to French legislation, the excavation material is considered contaminated if the mass content of an organic pollutant contained in the said excavation material is between the ISDND and ISDD limit values ​​indicated in Table 1. This excavation material considered contaminated is stored in specialized landfills such as hazardous waste storage facilities. Typically, it can be decontaminated there to recover and recycle the polluting elements (Phase 3a).

[0063] Typically, the excavation material is considered highly contaminated if the mass content of an organic pollutant contained in the excavation material is higher than the ISDD limit value indicated in Table 1. This excavation material considered highly contaminated is stored in specialized landfills. Typically, it can be decontaminated there to recover and recycle the polluting elements (Phase 3b).

[0064] A third subject of the invention is a method for recovering an excavation material considered to be inert according to the selection method of the second subject of the invention as defined above, said method comprising a step of recovering said excavation material as a construction material.

[0065] Typically, the construction material may be fill or aggregate, particularly fill, concrete aggregate or asphalt aggregate.

[0066] For the purposes of this application, "fill" means a construction material intended to raise land, fill a hollow or fill voids from mining operations.

[0067] For the purposes of this application, "aggregate" means a construction material used for the construction of civil engineering works, road works and buildings.

[0068] Concrete aggregate and asphalt aggregate are examples of aggregate.

[0069] For the purposes of this application, "aggregate for coating" means an aggregate used for the production of bituminous coatings.

[0070] For the purposes of this application, "concrete aggregate" means an aggregate used for making concrete.

[0071] The recovery step may include a step of producing a construction material from the inert material.

[0072] Typically, the production step may comprise one or more sub-steps of shaping the inert material, the sub-step(s) being adapted to the construction material, in particular to the backfill or to the aggregate, more particularly to the backfill, to the aggregate for concrete or to the aggregate for asphalt.

[0073] The choice of construction material depends on the concentration of organic pollutants in the excavation material. Thus, the production stage and the sub-stage(s) of shaping the inert material can be chosen using the determination method defined above.

[0074] A fourth subject of the invention is a method of storing an excavation material considered to be contaminated according to the selection method of the second subject of the invention as defined above, said method comprising a step of storing said excavation material.

[0075] Depending on the mass content of organic pollutants in the excavated material, the material is stored in a Non-Hazardous Waste Storage Facility or a Hazardous Waste Storage Facility. The storage facility can be chosen using the analysis method as defined above.

[0076] The storage step depends on the facility in which the inert material is stored. Thus, the storage step can be adapted to storage in a Non-Hazardous Waste Storage Facility or in a Hazardous Waste Storage Facility, in particular in a Hazardous Waste Storage Facility.

[0077] The storage of material in one of these facilities is known to those skilled in the art. They will therefore know how to implement the storage step.

[0078] A fifth subject of the invention is a method for decontaminating an excavation material considered to be contaminated according to the selection method of the second subject of the invention as defined above, said method comprising a step of decontaminating said excavation material.

[0079] The decontamination of excavated material is a step known to those skilled in the art. They will therefore know how to implement it. Examples Example 1: Determination of the mass content of HCT, PAH and VOC in different soil samples.

[0080] Different soil samples are tested after a preliminary preparation phase which consists of drying at 145°C for 30 minutes, followed by light grinding and then sieving at 200 µm. The soil samples thus prepared have a dry matter content of approximately 99.99%.

[0081] Conventional analyses according to current standards made it possible to determine the mass content of HCTs, PAHs and VOCs in the different soil samples. Rapid IR analysis (from 400 cm -1< to 4000 cm -1< , Michelson interferometer with a resolution of 0.5 cm -1< and DTGS detector) made it possible to detect HCTs at the specific peak of 1640 cm-', PAHs at the specific peak of 1400 cm -1< and VOCs at the specific peak of 3350 cm -1< .

[0082] The results are presented in Table 2 below.

[0083] Despite the almost complete drying of the soil samples, a specific band of water is detected between 2700 cm -1< and 3100 cm -1< . This band prevents any detection of a specific peak of organic pollutants whose mass contents indicated in Table 2 below are very low. [Table 2] Organic pollutants Scale 1 Scale 2 Scale 3 Exch.4 Mass content of HCT (mg / Kg of dry matter) determined according to standard NF EN ISO 16703 < 20 170 310 850 Peak area at 1640 cm -1< 1 2,5 2,2 1,3 Mass content of PAH (mg / kg of dry matter) determined according to standard NF EN 17503 - 35 59 170 Peak area at 1450 cm -1< -. 3,6 7,3 10,5 Mass content of VOCs (mg / kg of dry matter) according to ISO 22155 standard - - - 39000 Peak area at 3350 cm -1< - - - 32,2

[0084] Table 2 shows that it is possible to rapidly detect the presence of HCTs, PAHs and VOCs in soils using infrared spectroscopy analysis of soil samples. In addition, the peak areas calculated and presented in Table 2 are consistent with the mass contents of HCTs, PAHs and VOCs in soils determined by conventional analyses according to current standards. Example 2: Determination of the mass content of BTEX in a soil sample.

[0085] A soil sample is tested after a preliminary preparation phase which consists of drying at 145°C for 30 minutes, followed by light grinding and then sieving at 200 µm. The soil sample thus prepared has a dry matter content of approximately 99.99%. Conventional analysis according to the current standard made it possible to determine the mass content of BTEX in the soil sample. Rapid IR analysis made it possible to detect BTEX at the specific peak of 1620 cm -1< . The results are presented in Table 3 below. [Table 3] Pollutants Scale 5 Mass content of BTEX (mg / Kg of dry matter) according to ISO 22155 standard 6,5 Peak area at 1620 cm -1< 0,23

[0086] Table 3 shows that it is possible to quickly detect the presence of BTEX in a soil using infrared spectroscopy analysis of a soil sample. In addition, the peak areas calculated and presented in Table 3 are consistent with the BTEX mass content in the soil determined by conventional analysis according to the current standard.

Claims

1. Method for analyzing an excavation material comprising the following steps: a) analysis by infrared spectroscopy of a sample of an excavation material in a wave number range between 4000 cm -1 and 500 cm -1 to obtain an infrared spectrum, b) determining the mass content of organic pollutants in said sample from the infrared spectrum obtained in step a), the organic pollutants being chosen from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and combinations thereof.

2. Method according to claim 1 in which the excavation material has a dry matter content of 70% to 100%.

3. Method according to claim 1 or claim 2 in which step b) comprises the following sub-steps: b11) detection between 1600 cm -1 and 1700 cm -1of an absorption band specific to total hydrocarbons in the infrared spectrum obtained in step a), b21) integration of the absorption band detected in step b1) to calculate an area, and b31) comparison of the area obtained in step b2) with a calibration curve to determine the mass content of total hydrocarbons in the excavation material.

4. Method according to any one of claims 1 to 3 in which step b) comprises the following sub-steps: b12) detection between 1400 cm -1 and 1500 cm -1 of an absorption band specific to polycyclic aromatic hydrocarbons in the infrared spectrum obtained in step a), b22) integration of the absorption band detected in step c1) to calculate an area, and b32) comparison of the area obtained in step c2) with a calibration curve to determine the mass content of polycyclic aromatic hydrocarbons in the excavation material.

5. Method according to any one of claims 1 to 4 in which step b) comprises the following sub-steps: b13) detection between 3300 cm -1 and 3400 cm -1 of an absorption band specific to volatile organic compounds in the infrared spectrum obtained in step a), b23) integration of the absorption band detected in step b13) to calculate an area, and b33) comparison of the area obtained in step b23) with a calibration curve to determine the mass content of volatile organic compounds in the excavation material.

6. Method according to any one of claims 1 to 5 in which step b) comprises the following sub-steps: b14) detection between 800 cm -1 and 500 cm -1of one or two absorption bands specific to polychlorinated biphenyls in the infrared spectrum obtained in step a), b24) integration of the absorption bands detected in step b14) to calculate an area, and b34) comparison of the area obtained in step b24) with a calibration curve to determine the mass content of polychlorinated biphenyls in the excavation material.

7. Method according to any one of claims 1 to 6 in which step b) comprises the following sub-steps: b15) detection between 1650 cm -1 and 1600 cm -1 of a BTEX-specific absorption band in the infrared spectrum obtained in step a), b25) integration of the absorption band detected in step b15) to calculate an area, and b35) comparison of the area obtained in step b25) with a calibration curve to determine the BTEX mass content of the excavation material.

8. Method for selecting a reprocessing route for excavation material comprising the following steps: c) comparison of the mass content of each organic pollutant determined by the analysis method as defined according to any one of claims 1 to 7 with a fixed limit value, d) selection of the treatment route according to the following criteria: - if the mass content of each organic pollutant contained in the sample is lower than the fixed limit value then the material is considered inert (Routine 1), - if the mass content of an organic pollutant is higher than the fixed limit value then the material is considered contaminated and can be stored in specialized landfills (Routine 2) or can be decontaminated (Routine 3).

9. Method for recovering an excavation material considered to be inert according to the selection method as defined in claim 8 comprising a step of recovering said excavation material as a construction material.

10. A method according to claim 9 wherein the construction material is a fill or an aggregate.

11. Method of storing an excavation material considered to be contaminated according to the selection method as defined in claim 8 comprising a step of storing said excavation material.

12. Method for decontaminating an excavation material considered to be contaminated according to the selection method as defined in claim 8 comprising a step of decontaminating said excavation material.