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====== Polycyclic Aromatic Hydrocarbons (PAHs) - MMO Requirements and Analysis ======

The Marine Management Organisation (MMO) has specific requirements regarding the analysis of Polycyclic Aromatic Hydrocarbons (PAHs) in sediments, particularly for applications concerning the disposal of dredged material at sea. This document summarizes key information based on these requirements. General guidance on sediment analysis can be found on the [[https://www.gov.uk/guidance/marine-licensing-sediment-analysis-and-sample-plans|MMO's marine licensing and sediment analysis page]].

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===== MMO Requirements for PAH Analysis in Dredged Material =====

The Marine Management Organisation (MMO) requires the analysis of a specific suite of polycyclic aromatic hydrocarbons (PAHs) in sediments as part of applications for the disposal of dredged material at sea. These requirements align with international conventions, particularly the [[https://www.ospar.org|OSPAR (Oslo/Paris) Convention for the Protection of the Marine Environment of the North-East Atlantic]].

While the precise number and list of PAHs for any specific project are finalised within the sediment sampling plan agreed with the MMO in consultation with the Centre for Environment, Fisheries and Aquaculture Science (Cefas), a standard set of PAHs is expected to be analysed ([[https://www.gov.uk/guidance/marine-licensing-sediment-analysis-and-sample-plans|MMO Guidance]]).

==== OSPAR Defined PAHs ====

The OSPAR guidelines, which the MMO adheres to (see general MMO and OSPAR principles), explicitly define a sum of **nine specific PAHs (ΣPAH9)** that are commonly assessed. These are often referred to in OSPAR context documents (check specific [[https://www.ospar.org/work-areas/hasec/chemicals/hazardous-substances-strategies|OSPAR hazardous substances strategies]] for details on monitored substances):

  * //Anthracene//
  * //Benzo[a]anthracene//
  * //Benzo[ghi]perylene//
  * //Benzo[a]pyrene//
  * //Chrysene//
  * //Fluoranthene//
  * //Indeno[1,2,3-cd]pyrene//
  * //Pyrene//
  * //Phenanthrene//

==== Broader Suite of PAHs Typically Analysed ====

Although OSPAR guidelines highlight specific sets (like the 9 PAHs above, and others like a list of 16), it is common practice and often implicitly required by regulatory bodies aligning with such conventions to analyse for a broader suite. This often includes the US EPA (Environmental Protection Agency) 16 priority PAHs to ensure comprehensive assessment.

The 16 US EPA priority PAHs generally include:

  * //Naphthalene//
  * //Acenaphthylene//
  * //Acenaphthene//
  * //Fluorene//
  * //Phenanthrene//
  * //Anthracene//
  * //Fluoranthene//
  * //Pyrene//
  * //Benz[a]anthracene//
  * //Chrysene//
  * //Benzo[b]fluoranthene//
  * //Benzo[k]fluoranthene//
  * //Benzo[a]pyrene//
  * //Indeno[1,2,3-cd]pyrene//
  * //Dibenz[a,h]anthracene//
  * //Benzo[ghi]perylene//

Cefas, which provides scientific advice to the MMO, also has a history of analysing comprehensive lists of PAHs in dredged materials.

==== Regulatory Context ====

The MMO's specific guidance on [[https://www.gov.uk/government/publications/marine-licensing-sediment-analysis-and-sample-plans/chemical-determinands|Chemical determinands]] for sediment sampling specifies PAHs as a standard group of chemicals requiring analysis. The results of these analyses are assessed against action levels to determine the suitability of the dredged material for disposal at sea.

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===== All MMO's PAH Chemical Determinands =====

The Marine Management Organisation (MMO) lists a standard set of polycyclic aromatic hydrocarbons (PAHs) that are potentially required for sediment characterisation as part of marine licence applications. This definitive list is detailed on the UK government's official guidance page: [[https://www.gov.uk/government/publications/marine-licensing-sediment-analysis-and-sample-plans/chemical-determinands|Chemical determinands - GOV.UK]].

The MMO's PAH chemical determinands, according to this source, are:

  * //Acenapthene//
  * //Acenapthylene//
  * //Anthracene//
  * //Benz[a]anthracene//
  * //Benzo[a]pyrene//
  * //Benzo[b]fluoranthene//
  * //Benzo[e]pyrene//
  * //Benzo[g,h,i]perylene//
  * //Benzo[k]fluoranthene//
  * //C1-Naphthalenes// (alkylated naphthalenes with one additional carbon atom)
  * //C1-Phenanthrenes// (alkylated phenanthrenes/anthracenes with one additional carbon atom)
  * //C2-Naphthalenes// (alkylated naphthalenes with two additional carbon atoms)
  * //C3-Naphthalenes// (alkylated naphthalenes with three additional carbon atoms)
  * //Chrysene//
  * //Fluoranthene//
  * //Fluorene//
  * //Indeno[123-c,d]pyrene//
  * //Naphthalene//
  * //Perylene//
  * //Phenanthrene//
  * //Pyrene//
  * //Dibenz[a,h]anthracene//

This list comprises 22 specific PAHs and groups of alkylated PAHs. The guidance also specifies the limits of detection and quantification for these determinands.

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===== Reasons for Requiring Analysis of these 22 PAHs =====

The MMO requires the analysis of this specific list of 22 PAHs for several key reasons, aimed at protecting the marine environment and ensuring consistent regulatory assessment. These reasons are underpinned by scientific understanding of PAH behaviour and international best practice (see general principles in MMO and [[https://www.ospar.org|OSPAR]] guidance).

  - **Environmental Significance (Toxicity, Persistence, and Bioaccumulation):**
    - **Toxicity:** Many PAHs are toxic, carcinogenic, mutagenic, or teratogenic. //Benzo[a]pyrene// is a well-known potent carcinogen. (This is established scientific knowledge, often detailed in OSPAR CEMP documents and underpinning Cefas action levels).
    - **Persistence:** PAHs can persist in sediments, posing long-term risks.
    - **Bioaccumulation:** PAHs can accumulate in marine organisms and transfer up the food chain.

  - **Source Identification and Comprehensive Characterisation:**
    - The list covers a range of LMW and HMW PAHs, including parent and alkylated forms. This helps distinguish between petrogenic (oil-related) and pyrogenic (combustion-related) sources. The inclusion of alkylated PAHs (//C1-Naphthalenes//, etc.) is particularly important for this, a concept detailed in environmental forensics literature and applied by agencies like Cefas.

  - **Regulatory Consistency and Assessment against Standards:**
    - A standardised list ensures consistent data for comparing applications and assessing against Cefas Action Levels, as outlined in [[https://www.gov.uk/guidance/marine-licensing-sediment-analysis-and-sample-plans|MMO guidance]].

  - **Alignment with International Obligations and Best Practice:**
    - Many listed PAHs are recognized as priority pollutants by international bodies like [[https://www.ospar.org/work-areas/hasec/chemicals|OSPAR]] (e.g., on its List of Chemicals for Priority Action).

  - **Indicator Properties:**
    - Some PAHs (e.g., //Benzo[a]pyrene//) act as markers for overall PAH contamination. The broad suite provides a comprehensive contamination picture.

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===== Indicative Order of the 22 PAHs by Increasing Risk to the Marine Environment =====

Ordering the 22 PAHs by precise increasing risk is complex, as risk depends on multiple factors (toxicity, persistence, bioaccumulation, bioavailability, concentration). The following is a **general, indicative grouping** primarily using carcinogenic potential as a differentiator for higher risk categories. This is based on established PAH toxicology (information reflected in how agencies like the US EPA or OSPAR assess PAHs), not a specific MMO ranking document.

==== General Indicative Grouping by Increasing Potential Risk ====
(//Caveat: All listed PAHs are of regulatory concern. This is a simplified, generalized ranking.//)

  * **Group 1: Generally Considered Lower Risk (especially regarding carcinogenicity; may still pose acute toxicity risks):**
      - //Naphthalene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //C1-Phenanthrenes//, //Anthracene//, //Perylene//, //Fluoranthene//, //Pyrene//, //Benzo[e]pyrene//
  * **Group 2: Moderate or Variable Concern:**
      - //Chrysene//, //Benz[a]anthracene//, //Benzo[g,h,i]perylene//
  * **Group 3: Generally Considered Higher Risk (primarily due to higher carcinogenic potency, persistence, bioaccumulation):**
      - //Benzo[k]fluoranthene//, //Benzo[b]fluoranthene//, //Indeno[1,2,3-cd]pyrene//, //Benzo[a]pyrene//, //Dibenz[a,h]anthracene//

==== Important Considerations ====
  * **Alkylated PAHs:** Properties vary within these groups.
  * **Mixtures:** PAHs occur as complex mixtures, and their combined effects are critical.
  * **Acute vs. Chronic Effects:** LMW PAHs can be more acutely toxic; HMW PAHs are often associated with chronic effects like cancer.
  * **Site-Specific Conditions:** Actual risk is site-specific.

The comprehensive analysis of 22 PAHs allows for a better overall risk characterisation ([[https://www.gov.uk/guidance/marine-licensing-sediment-analysis-and-sample-plans|MMO Sediment Analysis Guidance]]).

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===== Indicative Ordering of the 22 PAHs by Various Environmental Properties =====

The following lists provide **generalised orderings** based on broad scientific principles of PAH chemistry and environmental behaviour. These are not absolute rankings from a specific MMO document but reflect established scientific understanding (found in environmental chemistry literature and informing guidance from bodies like US EPA, OSPAR, and UK agencies).

==== Increasing Persistence in the Marine Environment ====
(//Generally, LMW < HMW; linear/angular < highly condensed.//)
  * **Lower Persistence:** //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//
  * **Moderate Persistence:** //Fluoranthene//, //Pyrene//
  * **Higher Persistence:** //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
  * **Very High Persistence:** //Benzo[b]fluoranthene//, //Benzo[k]fluoranthene//, //Benzo[a]pyrene//, //Indeno[1,2,3-cd]pyrene//, //Dibenz[a,h]anthracene//, //Benzo[g,h,i]perylene//, //Perylene//

==== Increasing Bioaccumulation Potential ====
(//Generally increases with Kow and molecular size; HMW PAHs are typically more bioaccumulative.//)
  * **Lower BAP:** //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//
  * **Moderate BAP:** //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//, //Fluoranthene//, //Pyrene//
  * **Higher BAP:** //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
  * **Very High BAP:** //Benzo[b]fluoranthene//, //Benzo[k]fluoranthene//, //Benzo[a]pyrene//, //Indeno[1,2,3-cd]pyrene//, //Dibenz[a,h]anthracene//, //Benzo[g,h,i]perylene//, //Perylene//

==== Increasing Bioavailability (from water or potential for desorption from sediment) ====
(//Generally, higher for more soluble (LMW) PAHs; inversely related to sorption strength (Koc).//)
  * **Lower Bioavailability (Stronger sorption):** //Indeno[1,2,3-cd]pyrene//, //Dibenz[a,h]anthracene//, //Benzo[g,h,i]perylene//, //Perylene//, //Benzo[a]pyrene//, //Benzo[b]fluoranthene//, //Benzo[k]fluoranthene//
  * **Moderate-Low Bioavailability:** //Benzo[e]pyrene//, //Chrysene//, //Benz[a]anthracene//
  * **Moderate-High Bioavailability:** //Fluoranthene//, //Pyrene//, //C1-Phenanthrenes//, //C3-Naphthalenes//
  * **Higher Bioavailability (Weaker sorption, higher solubility):** //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //Acenaphthylene//, //Naphthalene//

==== Increasing Toxicity (Overall Hazard Approach) ====
(//Considers acute aquatic toxicity (often higher for LMW PAHs) and carcinogenic/chronic toxicity (often higher for HMW PAHs).//)
  * **Relatively Lower Overall Toxic Concern:** //Perylene//, //Benzo[e]pyrene//
  * **Primarily Acute Toxicants / Lower Carcinogenic Concern (LMW PAHs):** //Naphthalene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //C1-Phenanthrenes//, //Anthracene//, //Fluoranthene//, //Pyrene//
  * **Increasing Carcinogenic and Chronic Toxicity Concern (HMW PAHs):** //Benzo[g,h,i]perylene//, //Chrysene//, //Benz[a]anthracene//, //Benzo[k]fluoranthene//, //Benzo[b]fluoranthene//, //Indeno[1,2,3-cd]pyrene//, //Benzo[a]pyrene//, //Dibenz[a,h]anthracene//

==== Increasing Natural Abundance in the Marine Environment ====
(//Refers to significant contributions from non-direct-industrial-effluent sources like natural seeps, diagenesis, or natural fires.//)
  * **Lowest Natural Abundance (Predominantly anthropogenic):** //Dibenz[a,h]anthracene//, //Benzo[a]pyrene//, //Indeno[1,2,3-cd]pyrene//, //Benzo[b]fluoranthene//, //Benzo[k]fluoranthene//, //Benzo[g,h,i]perylene//, //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
  * **Low to Moderate Natural Input:** //Fluoranthene//, //Pyrene//
  * **Moderate Natural Input:** //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes// (especially from natural oil seeps)
  * **Highest Potential for Natural Contribution Among this List:** //Perylene// (known for diagenetic formation)

**Important Disclaimer:** These are generalised orderings. Actual properties and effects vary.

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===== Methods to Identify the Source of a PAH Mixture Found on Analysis =====

Identifying PAH sources involves "fingerprinting" by comparing sample PAH compositions to known source profiles. The MMO's comprehensive 22 PAH list ([[https://www.gov.uk/government/publications/marine-licensing-sediment-analysis-and-sample-plans/chemical-determinands|Chemical determinands - GOV.UK]]) aids these methods. (//General principles of source apportionment are found in environmental forensics literature; specific regulatory application would be guided by Cefas expertise and MMO requirements.//)

  - **PAH Ratios (Diagnostic Ratios):**
    - **Principle:** Certain PAHs form in different proportions depending on the source.
    - **Commonly Used Ratios (examples; threshold values can vary in literature):**
      - **LMW PAHs / HMW PAHs:** Distinguishes petrogenic vs. pyrogenic.
      - **//Anthracene// / (//Anthracene// + //Phenanthrene//) (ANT/[ANT+PHE]):** <0.1 often petrogenic; >0.1 pyrogenic.
      - **//Fluoranthene// / (//Fluoranthene// + //Pyrene//) (FLA/[FLA+PYR]):** Petrogenic (<0.4), liquid fossil fuel combustion (0.4-0.5), biomass/coal combustion (>0.5).
      - **//Benz[a]anthracene// / (//Benz[a]anthracene// + //Chrysene//) (BaA/[BaA+CHR]):** <0.2 petrogenic; 0.2-0.35 mixed/petroleum combustion; >0.35 combustion.
      - **//Indeno[1,2,3-cd]pyrene// / (//Indeno[1,2,3-cd]pyrene// + //Benzo[g,h,i]perylene//) (IcdP/[IcdP+BghiP]):** Petroleum combustion (0.2-0.5) vs. biomass/coal combustion (>0.5).

  - **Alkylated vs. Parent PAH Profiles:**
    - **Principle:** Petrogenic PAHs are rich in alkylated homologues (e.g., //C1-C3 Naphthalenes//); pyrogenic PAHs are dominated by parent compounds.
    - **Application:** High alkylated/parent ratios suggest petrogenic sources.

  - **Homologue and Isomer Patterns:**
    - **Principle:** Detailed distributions within alkylated series or isomer patterns provide clues.

  - **Multivariate Statistical Analysis:**
    - **Principle:** Techniques like Principal Component Analysis (PCA) or Positive Matrix Factorization (PMF) use the full 22 PAH dataset to identify patterns and compare with source profiles.

  - **Comparison with Source Libraries:**
    - **Principle:** Comparing the sample's PAH profile to a library of known source fingerprints.

==== Important Considerations and Limitations ====
  * **Weathering:** Environmental processes alter PAH profiles.
  * **Mixed Sources:** Common in marine sediments, complicating interpretation.
  * **Regional Variability:** Source fingerprints can vary regionally.
  * **Analytical Accuracy:** Crucial for reliable ratio calculation.

Combining these methods with the comprehensive 22 PAH data allows for more robust source identification.