Guidance

Chemical determinands

Updated 28 November 2024

Where chemical analysis is required, sediment samples must be analysed for a standard set of chemicals including metals and organotins. Chemicals must be tested for the appropriate sediment fraction – either whole or less than 2mm – as detailed below.

The Marine Management Organisation (MMO) may also require, depending on the history of the proposed site, that applicants assess sediments for:

• polychlorinated biphenyls (PCBs)
• polycyclic aromatic hydrocarbons (PAHs)
• organochlorine pesticides
• brominated flame retardants such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD)

Samples taken for chemical analysis must be stored frozen in glass containers. These containers must be acid cleaned (10% volume-to-volume aqueous nitric acid), and solvent-rinsed (hexane or pentane) before they are used. The integrity of container closure must also be protected (solvent-rinsed aluminium foil) to avoid potential loss of determinands, contamination of samples, or both.

Any additional chemical determinands and required methodologies will be defined when you engage with MMO before you apply, and will be dependent upon the location of proposed activity(s), site history, surrounding land use, depth and nature of the proposed activity(s). Other determinands may include:

• other chlorobiphenyls
• organophosphorus pesticides
• petroleum hydrocarbons
• other organotin compounds
• other anti-fouling agents
• polychlorinated dibenzodioxins or polychlorinated dibenzofurans
• radiological analysis

A temperature of 25°C should not be exceeded at any stage of storage or transportation. If the samples are not analysed within 48 hours, they must be stored at 4°C (short-term storage, under 1 week). Storage for over 1 week and up to 3 months is only possible for frozen samples (-20°C or below).

1. Quality control requirements

Methodologies must meet the limits of detection and quantification specified. All laboratories are expected to provide full details of methods used to measure the limits of detection.

All laboratories must demonstrate that they comply with the precision – specifically intermediate precision or within-laboratory reproducibility – and accuracy requirements detailed in the table below. On-going analytical accuracy and precision must be demonstrated using at least 1 relevant certified reference material (CRM) or in-house reference material (IHRM) for each group of determinands.

CRMs and IHRMs must reflect the matrix type (marine sediments) and determinand composition and concentration range of the sample material as closely as possible. The IHRM must be homogeneous and well characterised for the determinands of interest within the analytical laboratory. Ideally, stability tests should be undertaken to prove that the IHRM yields consistent results over time.

CRMs or IHRM must be fully analysed with every batch of samples and multiple CRMs/IHRMs must be used where necessary.

Results obtained from the CRM or IHRM analyses are used to produce and maintain control charts like a Shewhart chart. When using a new CRM or IHRM, at least 10 replicate results obtained from 10 separate sample batches is the minimum acceptable number of data points required to create a new control chart.

A procedural blank must be measured with each sample batch, and should be prepared simultaneously to the samples analysed using the same chemical reagents and solvents as for the samples.

For organic determinations, an analytical batch should not exceed 10 samples, excluding CRMs and procedural blanks.

1.1 Acceptable precision and accuracy criteria for quantitative methods

Concentration (mg/kg)	Precision (within laboratory reproducibility) – relative standard deviation, excluding any contribution due to sample heterogeneity (%)	Accuracy – mean recovery range (%)
Less than 0.001	35	50 to 120
0.001 to 0.01	30	60 to 120
0.01 to 0.1	20	70 to 120
0.1 to 1	15	70 to 110
Greater than 1	10	70 to 110

2. Trace metals

The standard set of trace metals that must be analysed in sediment samples obtained in support of a marine licence application for the disposal of dredged materials to sea are detailed in the table below.

Trace metals analysis must be carried out on whole (non-sieved) sediments. Before taking a subsample for analysis, the sample should be thoroughly mixed using a clean plastic spatula.

The samples must go through a partial digestion. The use of dilute nitric acid in an enclosed vessel microwave is recommended.

Quantification should be carried out by inductively coupled plasma-optical emission spectroscopy (ICP-OES), -mass spectrometry (ICP-MS), or both. The use of multi-level instrument calibration with at least 5 calibration levels is expected to define the calibration curve adequately. Quantification should be conducted in the linear region of the calibration curve. An internal standard must be used.

Alternative methods of partial digestion, like hot plate, heating block, use of different acids, and other types of analytical instruments and/or detection modes are acceptable if fitness for purpose is demonstrated. The use of total digestion methods (such as the HF method) or smaller sediment fraction – less than 63 micrometres (µm) – is not recommended as they are expected to produce higher levels of trace metals compared to a partial digestion of the whole sediment.

Results must be reported on a dry weight basis by taking into account the dry matter of the sample.

2.1 Standard set of metals required for sediment characterisation with limits of detection and quantification as dry weight (mg/kg)

Metals	Limits of detection	Limits of quantification
Arsenic (As)	2	6
Cadmium (Cd)	0.040	0.120
Chromium (Cr)	4	12
Copper (Cu)	4	12
Lead (Pb)	5	15
Mercury (Hg)	0.015	0.045
Nickel (Ni)	2	6
Zinc (Zn)	13	39

3. Organotins

The organotins that must be analysed in sediment samples obtained in support of a marine licence application for the disposal of dredged materials to sea are:

• tributyltin
• dibutylin

The limits of detection and limits of quantification for both organotins is 10µg/kg and 30µg/kg.

The analysis of organotins must be carried out on whole (non-sieved) sediment. Before taking a subsample for analysis, the sample should be thoroughly mixed using a clean plastic spatula.

Organotins are extracted from the sediment sample, such as by alkaline saponification, and can be converted into their hydrides using sodium borohydride.

The organotin hydrides can be extracted into an apolar solvent, like hexane, and analysed by gas chromatography, for example with mass spectrometric detector or flame photometric detector. Quantification is achieved in the linear region of the calibration curve which must be produced from 5 or more calibration levels. An internal standard must be used.

Alternative extraction and derivatisation methods (ethylation, pentylation) and other types of analytical instruments and/or detection modes may be acceptable. However, fitness for purpose must be demonstrated to ensure outputs are comparable with methods specified above.

Results must be reported on a dry weight basis by taking into account the dry matter of the sample.

4. Polychlorinated biphenyls

Where PCBs congeners analysis is required, the PCBs that should be analysed in sediment samples obtained in support of a marine licence application for the disposal of dredged materials to sea are detailed in the table below.

Before taking a sub-sample for analysis, the samples should be thoroughly mixed using a solvent-rinsed metal spatula. Plastic materials must not be used for sampling and storage owing to possible adsorption of the PCBs onto the container material, or contamination of sample extracts with potentially interfering organic contaminants.

The analysis of PCBs must be carried out on dry sediment sieved to less than 2mm fraction.

Organic solvent(s) must be used to extract PCBs from the sediment matrix. Ideally a mixture of non-polar and polar solvents such as hexane and acetone should be used. It is recommended that the Soxhlet method, a reference extraction technique, is used for PCB extraction. However any appropriate exhaustive extraction technique may be utilised if comparability with the Soxhlet method is demonstrated.

For PCB analysis, the crude sample extract must undergo at least one clean-up step to remove other co-extracted compounds present in sediment. It is expected that at least one of the analytical steps allows the removal of sulphur.

Gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detection (GC-ECD), or both should be used for the determination of PCBs. Due to the large number of possible PCB congeners that are present in the environment, chromatographic separation should be optimised.

Other types of analytical instruments and/or detection modes may be acceptable may be acceptable. However, fitness for purpose must be demonstrated to ensure outputs are comparable with methods specified above.

The use of multi-level instrument calibration with at least 5 calibration levels is expected to define the calibration curve adequately. Quantification should be conducted in the linear region of the calibration curve. An internal standard method should be used.

Results must be reported on a dry weight basis by taking into account the dry matter of the sample.

4.1 Standard set of PCBs potentially required for sediment characterisation with limits of detection and quantification as dry weight – ICES 7 PCBs are labelled with an *

PCBs (IUPAC Name)	Congener numbers	Limits of detection	Limits of quantification
2,2’,5- Trichlorobiphenyl	CB18	0.08µg/kg	0.24µg/kg
* 2,4,4’-Trichlorobiphenyl	CB28	0.08µg/kg	0.24µg/kg
2,4’,5-Trichlorobiphenyl	CB31	0.08µg/kg	0.24µg/kg
2,2’,3,5’-Tetrachlorobiphenyl	CB44	0.08µg/kg	0.24µg/kg
2,2’,4,4’-Tetrachlorobiphenyl	CB47	0.08µg/kg	0.24µg/kg
2,2’,4,5’-Tetrachlorobiphenyl	CB49	0.08µg/kg	0.24µg/kg
* 2,2’,5,5’-Tetrachlorobiphenyl	CB52	0.08µg/kg	0.24µg/kg
2,2’,4,4’-Tetrachlorobiphenyl	CB66	0.08µg/kg	0.24µg/kg
* 2,2’,4,5,5’-Pentachlorobiphenyl	CB101	0.08µg/kg	0.24µg/kg
2,3,3’,4,4’-Pentachlorobiphenyl	CB105	0.08µg/kg	0.24µg/kg
2,3,3’,4’,6-Pentachlorobiphenyl	CB110	0.08µg/kg	0.24µg/kg
* 2,3’,4,4’,5-Pentachlorobiphenyl	CB118	0.08µg/kg	0.24µg/kg
2,2’,3,3’,4,4’-Hexachlorobiphenyl	CB128	0.08µg/kg	0.24µg/kg
* 2,2’,3,4,4’,5’-Hexachlorobiphenyl	CB138	0.08µg/kg	0.24µg/kg
2,2’,3,4,5,5’-Hexachlorobiphenyl	CB141	0.08µg/kg	0.24µg/kg
2,2’,3,4’,5’,6-Hexachlorobiphenyl	CB149	0.08µg/kg	0.24µg/kg
2,2’,3,5,5’,6-Hexachlorobiphenyl	CB151	0.08µg/kg	0.24µg/kg
* 2,2’,4,4’,5,5’-Hexachlorobiphenyl	CB153	0.08µg/kg	0.24µg/kg
2,3,3’,4,4’,5-Hexachlorobiphenyl	CB156	0.08µg/kg	0.24µg/kg
2,3,3’,4,4’,6-Hexachlorobiphenyl	CB158	0.08µg/kg	0.24µg/kg
2,2’,3,3’,4,4’,5-Heptachlorobiphenyl	CB170	0.08µg/kg	0.24µg/kg
* 2,2’,3,4,4’,5,5’-Heptachlorobiphenyl	CB180	0.08µg/kg	0.24µg/kg
2,2’,3,4,4’,5’,6-Heptachlorobiphenyl	CB183	0.08µg/kg	0.24µg/kg
2,2’,3,4,5,5’,6-Heptachlorobiphenyl	CB187	0.08µg/kg	0.24µg/kg
2,2’,3,3’,4,4’,5,5’-Octachlorobiphenyl	CB194	0.08µg/kg	0.24µg/kg
Sum of ICES 7		1µg/kg	3µg/kg
Sum of 25 congeners		2µg/kg	6µg/kg

5. Polycyclic aromatic hydrocarbons

Where PAH analysis is required, the PAHs that should be analysed in sediment samples obtained in support of a marine licence application are detailed in the table below.

Plastic materials must not be used for sampling and storage owing to possible adsorption of the PAHs onto the container material.

Exposure to direct sunlight or other strong light must be avoided during storage of the samples as well as during all steps of sample preparation, including extraction and storage of the extracts. The use of amber glassware is strongly recommended. The analysis of PAHs must be carried out on total (non-sieved) sediment. Wet sediments must be analysed for PAHs determination and sediment samples must not be dried by physical means, like oven or freeze drying, before analysis. Before taking a sub-sample for analysis, the samples should be thoroughly mixed using a metal spatula.

If required, the total hydrocarbon concentration (THC) must be determined by ultra-violet fluorescence spectroscopy using the crude sample extract.

For PAH analysis, the crude sample extract must undergo at least one clean-up step to remove other co-extracted compounds present in sediment. It is expected that at least one of the analytical steps allows the removal of sulphur.

GC-MS is the recommended instrumental technique for the determination of the PAHs listed in the table below. Other types of analytical instruments and/or detection modes may be acceptable may be acceptable. However, fitness for purpose must be demonstrated to ensure outputs are comparable with methods specified above.

The use of multilevel instrument calibration with at least 5 calibration levels is expected in order to define the calibration curve adequately. Quantification should be conducted in the linear region of the calibration curve. An internal standard method should be used.

Results must be reported on a dry weight basis by taking into account the dry matter of the sample.

5.1 Standard set of PAHs potentially required for sediment characterisation with limits of detection and quantification as dry weight

PAHs	Limits of detection	Limits of quantification
Acenapthene	10µg/kg	30µg/kg
Acenapthylene	10µg/kg	30µg/kg
Anthracene	10µg/kg	30µg/kg
Benz[a]anthracene	10µg/kg	30µg/kg
Benzo[a]pyrene	10µg/kg	30µg/kg
Benzo[b]fluoranthene	10µg/kg	30µg/kg
Benzo[e]pyrene	10µg/kg	30µg/kg
Benzo[g,h,i]perylene	10µg/kg	30µg/kg
Benzo[k]fluoranthene	10µg/kg	30µg/kg
C1-Naphthalenes	10µg/kg	30µg/kg
C1-Phenanthrenes	10µg/kg	30µg/kg
C2-Naphthalenes	10µg/kg	30µg/kg
C3-Naphthalenes	10µg/kg	30µg/kg
Chrysene	10µg/kg	30µg/kg
Fluoranthene	10µg/kg	30µg/kg
Fluorene	10µg/kg	30µg/kg
Indeno[123-c,d]pyrene	10µg/kg	30µg/kg
Naphthalene	10µg/kg	30µg/kg
Perylene	10µg/kg	30µg/kg
Phenanthrene	10µg/kg	30µg/kg
Pyrene	10µg/kg	30µg/kg
Dibenz[a,h]anthracene	1µg/kg	3µg/kg
Total hydrocarbon content	1 mg/kg	3mg/kg

6. Brominated flame retardants

Where brominated flame retardant analysis is required, the PAHs that should be analysed in sediment samples obtained in support of a marine licence application are detailed in the above table.

The brominated flame retardants, such as PBDEs, that might need to be analysed in sediment samples obtained in support of a marine licence application are detailed in the below table.

Before taking a sub-sample for analysis, the samples should be thoroughly mixed using a solvent-rinsed metal spatula. Plastic materials must not be used for sampling and storage owing to possible adsorption of the PBDEs onto the container material, or the presence of PBDEs as contaminants in the plastic.

Analytical blanks must be analysed and assessed, due to the real possibility that contamination of samples with PBDEs may occur in the laboratory.

The analysis of PBDEs must be carried out on dry sediment sieved to less than 2mm fraction.

Special precautions are required in the laboratory when analysing PBDEs due to their sensitivity to UV light. PBDEs are prone to photolytic degradation and if exposed to UV light debromination can occur. Therefore, incoming light to the laboratory should be minimised by placing UV filters on the windows and over fluorescent lightings, or by not using any artificial lighting within the laboratory. It is recommended that all calibration and spiking standards are prepared and stored in amber glassware.

Samples should be extracted with organic solvent(s) to extract PBDEs from the sediment matrix, with a mixture of non-polar and polar solvents, such as hexane and acetone or dichloromethane giving the best results. A reference extraction technique uses Soxhlet apparatus, but other exhaustive extraction techniques may be used provided that they give comparable results to the Soxhlet method.

The crude sample extract must undergo at least one clean-up step to remove the many other compounds present in sediment which are co-extracted, with at least one of the clean-up steps to allow the removal of sulphur.

Either GC-MS or GC-MS (ion trap or triple quadropole) should be used in either electron ionisation or electron capture negative ionisation mode for the determination of the PBDEs listed below.

The use of multilevel instrument calibration with at least 5 calibration levels is expected to define the calibration curve adequately. Quantification should be conducted in the linear region of the calibration curve. An internal standard method should be used.

Results are reported on a dry weight basis by taking into account the dry matter of the sample.

6.1 Standard set of brominated flame retardants potentially required for sediment characterisation with limits of detection (0.1µg/kg) and quantification (0.3µg/kg) as dry weight

Brominated flame retardants	Congener numbers
2,2’,4,4’,6-pentabromodiphenyl ether	BDE 100
2,2’,3,4,4’,5’-hexabromodiphenyl ether	BDE 138
2,2’,4,4’,5,5’-hexabromodiphenyl ether	BDE 153
2,2’,4,4’,5,6’-hexa-bromodiphenyl ether	BDE 154
2,2´,4-tri-bromodiphenylether	BDE 17
2,2’,3,4,4’,5’,6-heptabromodiphenyl ether	BDE 183
2,2’,3,3’,4,4’,5,5’,6,6’-decabrominated diphenyl ether	BDE 209
2,4,4’-tribromodiphenyl ether	BDE 28
2,2’,4,4’-tetrabromodiphenyl ether	BDE 47
2,3’,4,4’-tetrabromodiphenyl ether	BDE 66
2,2’,3,4,4’-pentabromodiphenyl ether	BDE 85
2,2’,4,4’,5-pentabromodiphenyl ether	BDE 99

7. Organochlorine pesticides

The organochlorine pesticides that might need to be analysed in sediment samples obtained in support of a marine licence application are detailed in the list below.

The same methodological restrictions that apply to PCBs also apply to organochlorine pesticides.

Results are reported on a dry weight basis basis by taking into account the dry matter of the sample.

Standard set of organochlorine pesticides potentially required for sediment characterisation with limits of detection and quantification as dry weight with limits of detection and limits of quantification of 0.1µg/kg and 0.3µg/kg.

• alpha-hexachlorocyclohexane (α-HCH)
• gamma-hexachlorocyclohexane (γ-HCH)
• Dieldrin
• Hexachlorobenzene
• 1,1-Dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE)
• Dichlorodiphenyltrichloroethane (DDT)
• 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (TDE)