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

Abstract

The present invention is a rapid method for determining the mass content of all organic pollutants contained in excavated material. Abstract figure: Figure 1

Description

Title of the invention: DETERMINATION OF ORGANIC POLLUTANT CONTENT BY INFRARED SPECTROMETRY IN NATURAL SOILS AND EXCAVATED MATERIALS technical field

[0001] The present disclosure falls within the field of characterization of natural soils and excavated materials, in particular extracted by tunnel boring machine, to determine their mass content of organic pollutants such as total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX. Previous technique

[0002] During any construction on or in the ground, particularly during tunnel excavation, ground preparation is carried out 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 subway line produces approximately 800 tonnes of excavated material per day.

[0003] The excavated materials thus extracted contain various chemical species. Some chemical species originate from the composition of the rock or sand; these are referred to as the matrix. Other chemical species are present in smaller quantities; these are referred to as trace elements. When these trace elements exhibit toxicity, they are called pollutants. Some of these pollutants are, for example, hydrocarbons. There is endogenous pollution, originating from the geological environment of the extraction site, and pollution linked to local human activity at the surface. These chemical species can pose a risk to the environment when the excavated materials are stored after extraction. Before storing these excavated materials, it is therefore necessary to determine their contamination level. Determining this contamination level allows the materials to be directed to one of the three existing treatment streams.These three treatment channels are as follows: . 1) Inert materials are stored in order to be recycled, 2) Slightly contaminated materials are stored in specialized landfills (whose subsoil does not allow runoff into groundwater), 3) Contaminated materials are sent to a recovery facility to recover pollutants.

[0004] The selection of the appropriate treatment process depends, among other things, on the content mass concentration of organic pollutants in the excavated material. For example, the maximum permissible mass concentration thresholds for hydrocarbons are set by legislation. In France, these are Decision No. 2003 / 33 / EC of 19 December 2002 establishing criteria and procedures for the acceptance of waste at landfills and the decrees of 30 December 2002 concerning the storage of hazardous waste and of 12 December 2014 concerning the conditions for the acceptance of inert waste [...]. According to this Decision and these decrees, the maximum permissible mass concentration thresholds for hydrocarbons are among the most stringent in Europe. These thresholds are shown in Table 1 below.

[0005] [Tables 1] Organic pollutants to be detected ISDI limit value* ISDND limit value** ISDD limit value*** Mass content in mg / kg 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 (THCs) 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 Order of 12.12.2014 ** Decision No. 2003 / 33 / EC of 19.12.2002 *** Annex I of the decree of 30.12.2002

[0006] If the mass content of each organic pollutant in the excavated material is less than the ISDI limit value indicated in Table 1, then the excavated material is considered inert. It can then be stored in inert waste storage facilities for recovery, for example as a construction material or for landscaping.

[0007] If the mass content of at least one of the organic pollutants contained in the excavated material is between the ISDI and ISDND limit values If the levels of contamination are indicated in Table 1, then the excavated material is considered to be slightly contaminated. It can then be stored in non-hazardous waste storage facilities.

[0008] If the mass concentration of at least one of the organic pollutants contained in the excavated material falls between the ISDND and ISDD limit values ​​indicated in Table 1, then the excavated material is considered contaminated. It is then stored in hazardous waste storage facilities. There, it can be decontaminated to recover and reuse the organic pollutants.

[0009] The procedure for determining the mass content of each organic pollutant in an excavated material is set out in 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.

[0010] 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 very time-consuming. These procedures consist of a physicochemical analysis of the composition of the leachate obtained after simulated leaching of the excavated material. According to the French standards mentioned above, leaching (a well-known water treatment that dissolves soluble species) of the excavated material is simulated for 24 hours at ambient temperature (20°C ± 5°C). The leachate (residual liquid from the leaching) is then 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. These procedures take a minimum of 48 hours. To this must be added the time required for transport to a laboratory external to the excavation site and the processing time, for a total general duration of seven days. During this long period, it is necessary to store the excavated materials extracted from the construction sites which are very often located in geographical areas with very high constraints (urban area, mountain valley).

[0011] Surprisingly, the Applicant has found a method to de quickly determine the mass content of all organic pollutants contained in an excavated material. Summary

[0012] A method for analyzing an excavated material is proposed, comprising the following steps: a) analysis by infrared spectroscopy of a sample of excavated material in a range of wavenumbers between 4000 cm1 and 500 cm1, in particular between 3500 cm1 and 600 cm1, more particularly between 3000 cm1 and 650 cm1 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), organic pollutants being chosen from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and their combinations.

[0013] Advantageously, step a) of the method of the present invention makes it possible to obtain an infrared spectrum that may include: - absorption bands between 1630 cm1 and 1680 cm1 and around 1645 cm1 which are specific to total hydrocarbons, - absorption bands around 1450 cm1, 1500 cm1, 1580 cm1 and 1600 cm1 which are specific to polycyclic aromatic hydrocarbons, - absorption bands between 3610 cm1 and 3670 cm1, between 3200 cm1 and 3400 cm1 and around 1735 cm1 which are specific to volatile organic compounds, - absorption bands around 540 cm1 and 760 cm1 that are specific to polychlorinated biphenyls, and - an absorption band between 1610 cm1 and 1650 cm1 which is specific to BTEX.

[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 determine precisely the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX in the sample of the excavation material.

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

[0016] Indeed, infrared spectrometers are known, compact, reliable and robust devices that can be used on a construction site and can perform step a) of analysis in a few seconds.

[0017] Furthermore, the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX present in the excavation material determined by the analytical 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 method for excavated materials is also proposed, comprising the following steps: c) comparison of the mass content of each organic pollutant determined by the analytical method as described above with a fixed limit value, d) selection of the treatment process according to the following criteria: - if the mass content of each organic pollutant contained in the sample is less than the limit value set, then the material is considered inert (Stream 1), - if the mass content of an organic pollutant is greater than the limit value set then the material is considered contaminated and can be stored in specialized landfills (Stream 2) or can be decontaminated (Stream 3).

[0019] The limit value set for each of the organic pollutants may be established by national or international legislation or regulations. This limit value may be that indicated in Table 1 above. Brief description of the drawings

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

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

[0022] According to a first object of the invention, a method for analyzing an excavation material is proposed, comprising the following steps: a) analysis by infrared spectroscopy of a sample of excavated material in a range of wavenumbers between 4000 cm1 and 500 cm1, in particular between 3500 cm1 and 600 cm1, more particularly between 3000 cm1 and 650 cm1 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 their combinations.

[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 the conversion of this absorption into molecular vibration. This absorption corresponds specifically to the bonds present in the molecule. Using 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 analyzed sample. The absorption band may also be referred to as a peak in this application.

[0024] For the purposes of this application, "excavated material" means any material excavated during civil engineering or construction work, whether on the Earth's surface, for example during excavations or foundation work, or underground, for example during the digging of tunnels, caverns, and galleries. Typically, excavated material includes: - loose rocks such as gravel, sand, silt, clay and mixtures thereof; - crushed rocks; - materials originating from previous buildings or polluted sites such as landfills; or - excavation sludge.

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

[0026] Typically, excavation mud 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 their combinations.

[0029] For the purposes of this application, "total hydrocarbons", also abbreviated as THC, refers to a group of organic compounds derived from petroleum distillation and belonging to the family of persistent organic pollutants with a chain of between 10 and 40 carbon atoms. These compounds may be n-alkanes, iso-alkanes, cyclo-alkanes, alkylbenzenes and / or alkylnaphthalenes.

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

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

[0032] For the purposes of this application, "polychlorinated biphenyls", also noted as or PCB, means 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 excavated material used in step a) may have a dry matter content, or dryness, of 70% to 100%, in particular 75% to 90%, especially 78% to 82%.

[0035] For the purposes of this application, the "dry matter content" is the ratio between the dry mass of excavated material and the mass of the excavated material before drying, the dry mass of the excavated material being measured after drying approximately 30 grams of excavated material for 30 minutes at 145°C.

[0036] 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.

[0037] Drying excavated material is a standard step known to those skilled in the art. They will therefore be able to implement a drying step for the excavated material to obtain the dry matter content described above.

[0038] The excavation material implemented in step a) may have a particle size distribution such that 35% by mass of the excavation material has a diameter of less than 63 pm, in particular 95% by mass of the excavation material has a diameter of less than 125 pm, in particular 100% by mass of the excavation material has a diameter of less than 200 pm.

[0039] The particle size of the excavated material can be determined by sieving.

[0040] This particle size distribution can be obtained by manual or automatic grinding, in particular manual grinding, more specifically manual grinding in an agate mold. Manual grinding is advantageously suited to the varying hardness of the components of the excavated material.

[0041] Step b) of the analytical method may include the following substeps: b11) detection between 1600 cm⁻¹ and 1700 cm⁻¹ of a specific absorption band for 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 to be made obtained in step b21) with a calibration curve to determine the mass content of total hydrocarbons of the excavated material.

[0042] Advantageously, the wavenumber range of substep b11) allows for the reproducible and precise calculation of the specific absorption band for total hydrocarbons during step b21). From this area, it is then possible to determine, reproducibly and precisely, the mass content of total hydrocarbons in the excavated material during step b31).

[0043] These substeps bll)tob31) can allow the total hydrocarbon mass content of the excavated material to be determined quickly, precisely and reproducibly.

[0044] Step b) of the analysis method may, alternatively or additionally to substeps b11) to b31), comprise the following substeps: bl2) detection between 1400 cm⁻¹ and 1500 cm⁻¹ of a specific absorption band for 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 to be made obtained in step b22) with a calibration curve to determine the mass content of polycyclic aromatic hydrocarbons of the excavated material.

[0045] Advantageously, the wavenumber range of substep b 12) allows for the reproducible and precise calculation of the specific absorption band for polycyclic aromatic hydrocarbons during step b22). From this area, it is then possible to determine, reproducibly and precisely, the mass content of polycyclic aromatic hydrocarbons in the excavated material during step b32).

[0046] These substeps b 12) to b32) can allow for the rapid, precise and reproducible determination of the mass content of polycyclic aromatic hydrocarbons in the excavated material.

[0047] Step b) of the analysis method may, alternatively or additionally to substeps b11) to b31) and b12) to b32), comprise the following substeps: bl3) detection between 3300 cm 1 and 3400 cm 1 of a specific absorption band for volatile organic compounds in the infrared spectrum obtained in step a), b23) integration of the absorption band detected in step b13) to calculate a area, and b33) comparison of the area obtained in step b23) with a calibration curve to determine the mass content of volatile organic compounds of the excavated material.

[0048] Advantageously, the wavenumber range of substep b 13) allows for the reproducible and precise calculation of the specific absorption band for volatile organic compounds during step b23). From this area, it is then possible to determine, reproducibly and precisely, the mass content of volatile organic compounds in the excavated material during step b33).

[0049] These substeps b 13) to b33) can allow for the rapid, precise and reproducible determination of the mass content of volatile organic compounds in the excavated material.

[0050] 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: b 14) 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 b 14) to calculate an area, and b34) comparison to be made obtained in step b24) with a calibration curve to determine the mass content of polychlorinated biphenyls in the excavated material.

[0051] Advantageously, the wavenumber range of substep bl4) allows for the reproducible and precise calculation of polychlorinated biphenyl-specific absorption bands during step b24). From this area, it is then possible to determine, reproducibly and precisely, the mass content of polychlorinated biphenyls in the excavated material during step b34).

[0052] These substeps b 14) to b34) can allow the mass content of polychlorinated biphenyls in the excavated material to be determined quickly, precisely and reproducibly.

[0053] Step b) of the analysis method may, alternatively or additionally to substeps b11) to b31), bl2) to b32), bl3) to b33) and bl4) to b34) comprise the following substeps: bl5) 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 to be made obtained in step b25) with a calibration curve to determine the mass content of BTEX of the excavated material.

[0054] Advantageously, the wavenumber range of substep b 15) allows for the reproducible and precise calculation of the specific absorption band for BTEX during step b25). From this area, it is then possible to determine, reproducibly and precisely, the mass content of BTEX in the excavated material during step b35).

[0055] These substeps bl5) to b35) can allow the mass content of BTEX in the excavated material to be determined quickly, precisely and reproducibly.

[0056] Thanks to the precise determination of the mass contents of total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls and BTEX of the excavation material by the analytical method of the present invention, it is possible to select the right reprocessing channel for an excavation material.

[0057] Thus, according to a second object of the invention, a method for selecting a reprocessing channel for excavated materials is proposed, comprising the following steps: c) comparison of the mass content of each organic pollutant determined by the analytical method as described above with a fixed limit value, d) selection of the treatment process according to the following criteria: - if the mass content of each organic pollutant contained in the sample is less than the limit value set, then the material is considered inert (Stream 1), - if the mass content of an organic pollutant is greater than the limit value set then the material is considered contaminated and can be stored in specialized landfills (Stream 2) or can be decontaminated (Stream 3).

[0058] In this selection method, the organic pollutants are the same as the organic pollutants in the analysis method, i.e. those chosen from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and their combinations.

[0059] Typically, according to French legislation, excavation material is considered inert if the mass content of each organic pollutant is less than the ISDI limit value indicated in Table 1. This excavation material is then reusable, for example as a construction material or for landscaping (Stream 1).

[0060] Typically, according to French legislation, excavated material is considered slightly contaminated if the mass concentration of an organic pollutant contained in said excavated material is between the ISDI and ISDND limit values ​​indicated in Table 1. This excavated material is considered as slightly contaminated is stored in specialized landfills such as non-hazardous waste storage facilities (Stream 2).

[0061] Typically, according to French legislation, excavated material is considered contaminated if the mass concentration of an organic pollutant contained in said excavated material is between the ISDND and ISDD limit values ​​indicated in Table 1. This excavated material, considered contaminated, is stored in specialized landfills such as hazardous waste storage facilities. Typically, it can be decontaminated there to recover and reuse the pollutants (Stream 3a).

[0062] Typically, excavated material is considered heavily contaminated if the mass concentration of an organic pollutant contained in said excavated material exceeds the ISDD limit value indicated in Table 1. This excavated material, considered heavily contaminated, is stored in specialized landfills. Typically, it can be decontaminated there to recover and reuse the pollutants (Stream 3b).

[0063] A third object of the invention is a method of valorizing an excavation material considered to be inert according to the selection method of the second object of the invention as defined above, said method comprising a step of valorizing said excavation material as a construction material.

[0064] Typically, the construction material can be an embankment or an aggregate, in particular an embankment, an aggregate for concrete or an aggregate for asphalt.

[0065] For the purposes of this application, "fill" means a construction material intended to raise land, fill a hollow or fill voids in mining operations.

[0066] For the purposes of this application, "aggregate" means a construction material used for the construction of civil engineering works, road works and buildings.

[0067] Concrete aggregate and asphalt aggregate are examples of aggregate.

[0068] For the purposes of this application, "aggregate for asphalt" means an aggregate used for the production of bituminous asphalt.

[0069] For the purposes of this application, "concrete aggregate" means aggregate used in the production of concrete.

[0070] The valorization step may include a step of producing a construction material from the inert material.

[0071] Typically the production step may include one or more sub-steps for shaping the inert material, the sub-step or sub-steps being adapted to the construction material, in particular to the fill or aggregate, more particularly to the fill, aggregate for concrete or aggregate for asphalt.

[0072] The choice of construction material depends on the concentration of organic pollutants contained in the excavated material. Thus, the production stage, and the sub-stage(s) of shaping the inert material, can be chosen using the determination method as defined above.

[0073] A fourth object of the invention is a method of storing an excavation material considered to be contaminated according to the selection method of the second object of the invention as defined above, said method comprising a step of storing said excavation material.

[0074] Depending on the mass content of organic pollutants contained in the excavated material, the material is stored in a Non-Hazardous Waste Storage Facility or in a Hazardous Waste Storage Facility. The storage facility can be chosen using the analytical method as defined above.

[0075] The storage stage depends on the facility in which the inert material is stored. Thus, the storage stage 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.

[0076] The storage of material in one of these facilities is known to a person skilled in the art. He will therefore be able to implement the storage step.

[0077] A fifth object of the invention is a method for decontaminating an excavation material considered to be contaminated according to the selection method of the second object of the invention as defined above, said method comprising a step of decontaminating said excavation material.

[0078] The decontamination of excavated material is a step known to a person skilled in the art. He will therefore know how to carry it out. Examples

[0079] Example 1: Determination of the mass content of THCs, PAHs and VOCs of different soil samples.

[0080] Different soil samples are tested after a preliminary preparation phase which consists of light grinding followed by sieving at 200 µm. Conventional analyses according to current standards made it possible to determine the mass content of HCT, PAHs and VOCs in the different soil samples. Rapid IR analysis enabled the detection of HCT at a specific peak of 1640 cm1, PAHs at a specific peak of 1400 cm1 and VOCs at a specific peak of 3350 cm1. The results are presented in Table 2 below.

[0081] [Tables2] Organic pollutants Sample 1 Sample 2 Sample 3 Sample 4 Mass content of THC (mg / kg dry matter) determined according to standard NF EN ISO 16703 <20 170 310 850 Peak area at 1640 cm² 1 1 2.5 2.2 1.3 Mass content of PAHs (mg / kg dry matter) determined according to standard NF EN 17503 - 35 59 170 Peak area at 1450 cm² 1 3.6 7.3 10.5 Mass content of VOCs (mg / kg dry matter) according to standard ISO 22155 - - - 39000 Peak area at 3350 cm² 1 - - - 32.2

[0082] Table 2 highlights that it is possible to rapidly detect the presence of HCTs, PAHs and VOCs in soils through infrared spectroscopy analysis of samples of these soils. Furthermore, the peak areas calculated and presented in Table 2 are in agreement with the mass concentrations of THCs, PAHs and VOCs in soils determined by conventional analyses according to current standards.

[0083] Example 2: Determination of the mass content of BTEX in a soil sample.

[0084] A soil sample is tested after a preliminary preparation phase consisting of light grinding followed by sieving at 200 µm. Conventional analysis according to the applicable standard was used to determine the mass content of BTEX in the soil sample. Rapid IR analysis enabled the detection of BTEX at a specific peak of 1620 cm The results are presented in Table 3 below.

[0085] [Tables3] Pollutants Sample 5 Mass content of BTEX (mg / Kg dry matter) according to ISO 22155 6.5 Peak area at 1620 cm² 1 0.23

[0086] Table 3 highlights that it is possible to quickly detect the presence of BTEX in soil through infrared spectroscopy analysis of a sample of that soil. Furthermore, the peak areas calculated and presented in Table 3 are in agreement with the mass content of BTEX in the soil determined by conventional analysis according to the standard in force.

Claims

Demands

1. Method for analyzing an excavated material comprising the following steps: a) infrared spectroscopic analysis of a sample of an excavated material in a wavenumber range between 4000 cm1 and 500 cm1 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 selected from total hydrocarbons, polycyclic aromatic hydrocarbons, volatile organic compounds, polychlorinated biphenyls, BTEX and combinations thereof, wherein step b) comprises the following substeps: b1) detection between 1600 cm1 and 1700 cm1 of a specific absorption band for total hydrocarbons in the infrared spectrum obtained in step a), b2) integration of the absorption band detected in step b1) to calculate an area,and b31) comparison to be made obtained in step b2) with a calibration curve to determine the mass content of total hydrocarbons in the excavated material.

2. Method according to claim 1 wherein the excavated material has a dry matter content of 70% to 100%.

3. Method according to claim 1 or claim 2 wherein, prior to step a), the excavated material undergoes a grinding step to exhibit a particle size distribution such that 35% by mass of the excavated material has a diameter of less than 63 pm.

4. A method according to any one of claims 1 to 3 wherein step b) comprises the following substeps: b12) detection between 1400 cm1 and 1500 cm1 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 excavated material.

5. A method according to any one of claims 1 to 4 in which Step b) includes the following substeps: b13) detection between 3300 cm1 and 3400 cm1 of a specific absorption band for 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 excavated material.

6. A method according to any one of claims 1 to 5 wherein step b) comprises the following substeps: b 14) detection between 800 cm1 and 500 cm1 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 b 14) 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 excavated material.

7. A method according to any one of claims 1 to 6 wherein step b) comprises the following substeps: b15) detection between 1650 cm1 and 1600 cm1 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 excavated material.

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

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

10. Method according to claim 9 wherein the construction material is an embankment 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.