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--- gemini_-_pahs [2025/05/28 22:19] – created nefcadmin
+++ gemini_-_pahs [2025/05/28 22:23] (current) – nefcadmin
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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.
+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]].
 ----
 ===== 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 OSPAR (Oslo/Paris) Convention for the Protection of the Marine Environment of the North-East Atlantic.
+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.
+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, explicitly define a sum of **nine specific PAHs (ΣPAH9)** that must be assessed. These are:
+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//
@@ Line 26: / Line 26: @@
 ==== Broader Suite of PAHs Typically Analysed ====
-Although the OSPAR guidelines explicitly list these nine PAHs, it is common practice and often implicitly required to analyse for a broader suite, typically **16 PAHs**, often referred to as the US EPA (Environmental Protection Agency) 16 priority PAHs. This more comprehensive analysis allows for a more thorough assessment of potential contamination and ensures that values for other OSPAR-referenced sums, such as ΣPAH16, can be calculated.
+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:
@@ Line 47: / Line 47: @@
   * //Benzo[ghi]perylene//
-Cefas, which provides scientific advice to the MMO, has also historically analysed a comprehensive list of PAHs in dredged materials.
+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 guidance on "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, where available, to determine the suitability of the dredged material for disposal at sea. Applicants must agree on a sediment sampling plan with the MMO, which will confirm the specific analytical requirements, including the list of PAHs to be determined.
+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.
 ----
 ===== 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 list is detailed on the UK government's official guidance page, "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 are:
+The MMO's PAH chemical determinands, according to this source, are:
   * //Acenapthene//
@@ Line 83: / Line 83: @@
   * //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. It's important to note that while this is the standard set, the exact requirements for a specific project will be confirmed in the sediment sampling plan agreed with the MMO.
+This list comprises 22 specific PAHs and groups of alkylated PAHs. The guidance also specifies the limits of detection and quantification for these determinands.
 ----
 ===== Reasons for Requiring Analysis of these 22 PAHs =====
-The Marine Management Organisation (MMO) requires the analysis of a specific list of 22 PAHs and alkylated PAH groups in sediments for several key reasons, all aimed at protecting the marine environment and ensuring consistent regulatory assessment for the disposal of dredged material at sea. These reasons include:
+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 on the list are known to be toxic, with some being carcinogenic (cancer-causing), mutagenic (causing genetic mutations), and/or teratogenic (causing birth defects) to marine organisms and potentially humans if they enter the food chain. Specific PAHs like //Benzo[a]pyrene// are well-known potent carcinogens.
+    - **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 marine sediments for long periods, resisting degradation. This longevity means they can pose a long-term risk to the marine ecosystem. Higher molecular weight PAHs, in particular, tend to be more persistent.
+    - **Persistence:** PAHs can persist in sediments, posing long-term risks.
-    - **Bioaccumulation:** PAHs can accumulate in marine organisms. Hydrophobic PAHs, especially those with higher molecular weights, tend to adsorb to particulate matter and can be ingested by sediment-dwelling organisms, potentially being transferred up the food chain.
+    - **Bioaccumulation:** PAHs can accumulate in marine organisms and transfer up the food chain.
   - **Source Identification and Comprehensive Characterisation:**
-    - The list includes a range of PAHs, from lower molecular weight (e.g., //Naphthalene// and its alkylated forms) to higher molecular weight compounds (e.g., //Benzo[g,h,i]perylene//, //Indeno[1,2,3-cd]pyrene//).
+    - 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.
-    - Crucially, it includes both **parent PAHs** (non-alkylated) and **alkylated PAHs** (e.g., //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//). The relative proportions of these different types of PAHs can help indicate the source of the contamination:
-      - **Petrogenic PAHs** (originating from petroleum sources like crude oil or refined products) are often rich in alkylated PAHs and lower molecular weight parent PAHs.
-      - **Pyrogenic PAHs** (originating from the incomplete combustion of organic materials, such as fossil fuels, wood, or waste) are typically dominated by non-alkylated, higher molecular weight PAHs.
-    - Including compounds like //Perylene//, which can have both natural (diagenetic) and anthropogenic sources, adds to the comprehensiveness of the assessment.
   - **Regulatory Consistency and Assessment against Standards:**
-    - The MMO aims to ensure that sediment analysis data is consistent and comparable across different applications for disposal at sea. A standardised list of determinands is essential for this.
+    - 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]].
-    - The concentrations of these PAHs are assessed against Cefas Action Levels (where available) as part of a weight-of-evidence approach to determine the suitability of dredged material for sea disposal. Having a defined list allows for a clear framework for these regulatory decisions.
   - **Alignment with International Obligations and Best Practice:**
-    - Many of the PAHs on the list are recognized as priority pollutants by international bodies. For example, PAHs as a group are on the OSPAR (Oslo/Paris Convention) List of Chemicals for Priority Action due to their hazardous properties.
+    - 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).
-    - The selection reflects a scientifically informed approach to monitoring common and hazardous PAHs found in marine environments, aligning with broader European and international monitoring strategies (e.g., requirements under the Water Framework Directive for certain PAHs).
   - **Indicator Properties:**
-    - Some PAHs, like //Benzo[a]pyrene//, are often used as markers for the presence and potential toxicity of the entire PAH mixture.
+    - Some PAHs (e.g., //Benzo[a]pyrene//) act as markers for overall PAH contamination. The broad suite provides a comprehensive contamination picture.
-    - The analysis of a broad suite provides a more complete picture of the overall PAH contamination burden in the sediment.
-In summary, the MMO's requirement to analyse these 22 PAHs is driven by the need to comprehensively assess the potential environmental risks associated with dredged material disposal, understand the sources of contamination, ensure regulatory consistency, and meet national and international commitments for protecting the marine environment.
 ----
 ===== Indicative Order of the 22 PAHs by Increasing Risk to the Marine Environment =====
-Ordering the 22 Polycyclic Aromatic Hydrocarbons (PAHs) required for analysis by the Marine Management Organisation (MMO) by their precise order of increasing risk to the marine environment is a complex task. "Risk" is not a single, easily quantifiable value but rather a function of several factors, including:
+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.
-  * **Toxicity**
-  * **Persistence**
-  * **Bioaccumulation Potential**
-  * **Bioavailability**
-  * **Concentration**
-However, we can provide a general, indicative grouping of these PAHs from typically lower to higher concern, primarily using carcinogenic potential as a key differentiator for higher risk categories, while also considering persistence and molecular weight. This ranking is a simplification and should be interpreted with caution, as all listed PAHs are of concern to the MMO.
 ==== General Indicative Grouping by Increasing Potential Risk ====
+(//Caveat: All listed PAHs are of regulatory concern. This is a simplified, generalized ranking.//)
-It's important to note that even "lower risk" PAHs can be harmful at high concentrations or to specific sensitive species. Alkylated PAHs are groups of compounds, and their properties can vary.
+  * **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//
-  * **Group 1: Generally Considered Lower Risk (especially regarding carcinogenicity; may still pose acute toxicity risks, particularly at high concentrations)**
+==== Important Considerations ====
-    These are often Lower Molecular Weight (LMW) PAHs (2-3 rings) or PAHs with low carcinogenic potency according to common Toxic Equivalency Factor (TEF) schemes. LMW PAHs can be more water-soluble and cause acute toxicity.
+  * **Alkylated PAHs:** Properties vary within these groups.
-      - //Naphthalene//
+  * **Mixtures:** PAHs occur as complex mixtures, and their combined effects are critical.
-      - //C1-Naphthalenes//
+  * **Acute vs. Chronic Effects:** LMW PAHs can be more acutely toxic; HMW PAHs are often associated with chronic effects like cancer.
-      - //C2-Naphthalenes//
+  * **Site-Specific Conditions:** Actual risk is site-specific.
-      - //C3-Naphthalenes//
-      - //Acenaphthylene//
-      - //Acenaphthene//
-      - //Fluorene//
-      - //Phenanthrene//
-      - //C1-Phenanthrenes// (and anthracenes)
-      - //Anthracene//
-      - //Perylene// (Often has natural sources too, generally low toxicity compared to potent carcinogens)
-      - //Fluoranthene// (Low carcinogenic TEF, but can have other toxic effects)
-      - //Pyrene// (Low carcinogenic TEF, but can have other toxic effects)
-      - //Benzo[e]pyrene// (Generally considered to have low or no carcinogenic TEF)
-  * **Group 2: Moderate or Variable Concern**
+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]]).
-    These PAHs may have some carcinogenic potential (moderate TEFs), or be notably persistent and bioaccumulative.
-      - //Chrysene// (TEF varies, can be significant; persistent)
-      - //Benz[a]anthracene// (Recognised carcinogen, moderate TEF)
-      - //Benzo[g,h,i]perylene// (High Molecular Weight (HMW) PAH, very persistent and a marker of pyrogenic sources, but usually assigned a low/zero carcinogenic TEF)
-  * **Group 3: Generally Considered Higher Risk (primarily due to higher carcinogenic potency, persistence, and bioaccumulation)**
-    These are typically High Molecular Weight (HMW) PAHs (4-6 rings) that are known or probable human carcinogens and have significant TEF values relative to //Benzo[a]pyrene//.
-      - //Benzo[k]fluoranthene// (Recognised carcinogen, significant TEF)
-      - //Benzo[b]fluoranthene// (Recognised carcinogen, significant TEF)
-      - //Indeno[1,2,3-cd]pyrene// (Recognised carcinogen, significant TEF, persistent)
-      - //Benzo[a]pyrene// (Reference compound for PAH carcinogenicity, high TEF of 1, known human carcinogen, persistent, bioaccumulative)
-      - //Dibenz[a,h]anthracene// (Often has one of the highest TEF values, sometimes even higher than //Benzo[a]pyrene//; potent carcinogen, persistent)
-==== Important Considerations for this Generalised Order ====
-  * **Alkylated PAHs:** The groups C1, C2, C3-Naphthalenes and C1-Phenanthrenes represent multiple individual compounds. Alkylation can sometimes increase persistence and toxicity compared to the parent PAH, particularly for LMW PAHs. They are key indicators of petrogenic (oil-related) pollution.
-  * **Mixtures:** PAHs almost always occur as complex mixtures in the environment. The combined effect of these mixtures (synergistic, additive, or antagonistic) is a critical aspect of risk assessment that a simple ranking of individual compounds cannot capture.
-  * **Acute vs. Chronic Effects:** LMW PAHs, while often less carcinogenic, can be more acutely toxic to aquatic organisms than HMW PAHs, which tend to cause chronic effects like cancer.
-  * **Site-Specific Conditions:** The actual risk posed by these PAHs at a specific location depends on their concentrations, the sediment characteristics, water conditions, and the local marine ecosystem.
-The MMO's requirement to analyse all 22 of these PAHs allows for a comprehensive characterisation of sediment contamination, enabling a more informed assessment of the potential risks associated with the disposal of dredged material at sea, rather than implying that all 22 pose an identical level of risk.
 ----
 ===== Indicative Ordering of the 22 PAHs by Various Environmental Properties =====
-Creating definitive, strictly ordered lists of the 22 PAHs required by the Marine Management Organisation (MMO) for increasing toxicity, persistence, bioaccumulation potential, bioavailability, and natural abundance is highly challenging. These properties are influenced by numerous factors. However, based on general scientific understanding, we can provide indicative groupings. The alkylated PAHs (e.g., //C1-Naphthalenes//) are groups of isomers, and their properties are generally considered based on the parent compound or lower alkylated forms.
+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).
-The 22 PAHs referred to 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//, //C1-Phenanthrenes// (and/or anthracenes), //C2-Naphthalenes//, //C3-Naphthalenes//, //Chrysene//, //Fluoranthene//, //Fluorene//, //Indeno[1,2,3-cd]pyrene//, //Naphthalene//, //Perylene//, //Phenanthrene//, //Pyrene//, //Dibenz[a,h]anthracene//.
 ==== Increasing Persistence in the Marine Environment ====
-Persistence generally increases with molecular size and complexity.
+(//Generally, LMW < HMW; linear/angular < highly condensed.//)
+  * **Lower Persistence:** //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//
-  * **Lower Persistence (Relatively more degradable, volatile, or soluble):**
+  * **Moderate Persistence:** //Fluoranthene//, //Pyrene//
-    - //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//
+  * **Higher Persistence:** //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
-    - //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//
+  * **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//
-  * **Moderate Persistence:**
-    - //Fluoranthene//, //Pyrene//
-  * **Higher Persistence:**
-    - //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
-  * **Very High Persistence (Highly resistant to degradation):**
-    - //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 ====
-Bioaccumulation potential generally increases with Kow and molecular size.
+(//Generally increases with Kow and molecular size; HMW PAHs are typically more bioaccumulative.//)
+  * **Lower BAP:** //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//
-  * **Lower Bioaccumulation Potential (Lower Kow):**
+  * **Moderate BAP:** //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//, //Fluoranthene//, //Pyrene//
-    - //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//
+  * **Higher BAP:** //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
-  * **Moderate Bioaccumulation Potential:**
+  * **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//
-    - //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//
-    - //Fluoranthene//, //Pyrene//
-  * **Higher Bioaccumulation Potential:**
-    - //Benz[a]anthracene//, //Chrysene//, //Benzo[e]pyrene//
-  * **Very High Bioaccumulation Potential (Higher Kow):**
-    - //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) ====
-Bioavailability from water is generally higher for more soluble PAHs. This list considers general potential for uptake from water or desorption.
+(//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//
-  * **Lower Bioavailability (Tend to be strongly bound to sediment, low water solubility):**
+  * **Moderate-Low Bioavailability:** //Benzo[e]pyrene//, //Chrysene//, //Benz[a]anthracene//
-    - //Indeno[1,2,3-cd]pyrene//, //Dibenz[a,h]anthracene//, //Benzo[g,h,i]perylene//, //Perylene//
+  * **Moderate-High Bioavailability:** //Fluoranthene//, //Pyrene//, //C1-Phenanthrenes//, //C3-Naphthalenes//
-    - //Benzo[a]pyrene//, //Benzo[b]fluoranthene//, //Benzo[k]fluoranthene//
+  * **Higher Bioavailability (Weaker sorption, higher solubility):** //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //Acenaphthylene//, //Naphthalene//
-  * **Moderate-Low Bioavailability:**
-    - //Benzo[e]pyrene//, //Chrysene//, //Benz[a]anthracene//
-  * **Moderate-High Bioavailability:**
-    - //Fluoranthene//, //Pyrene//
-    - //C1-Phenanthrenes//, //C3-Naphthalenes//
-  * **Higher Bioavailability (Higher water solubility, weaker sediment binding):**
-    - //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//
-    - //C1-Naphthalenes//, //C2-Naphthalenes//, //Acenaphthylene//, //Naphthalene//
 ==== Increasing Toxicity (Overall Hazard Approach) ====
-This ranking considers a combination of acute aquatic toxicity and carcinogenic/chronic toxicity.
+(//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//
-  * **Relatively Lower Overall Toxic Concern (but not harmless):**
+  * **Primarily Acute Toxicants / Lower Carcinogenic Concern (LMW PAHs):** //Naphthalene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //C1-Phenanthrenes//, //Anthracene//, //Fluoranthene//, //Pyrene//
-    - //Perylene//
+  * **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//
-    - //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 ====
-"Natural abundance" here refers to contributions from sources other than direct anthropogenic industrial discharges, such as natural geological processes or natural combustion events.
+(//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//
-  * **Lowest Natural Abundance (Predominantly from anthropogenic combustion/industrial sources):**
+  * **Low to Moderate Natural Input:** //Fluoranthene//, //Pyrene//
-    - //Dibenz[a,h]anthracene//
+  * **Moderate Natural Input:** //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//, //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes// (especially from natural oil seeps)
-    - //Benzo[a]pyrene//
+  * **Highest Potential for Natural Contribution Among this List:** //Perylene// (known for diagenetic formation)
-    - //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 (From broader combustion sources including natural fires, some geological):**
-    - //Fluoranthene//
-    - //Pyrene//
-  * **Moderate Natural Input (Can have sources from natural seeps, biomass combustion, some diagenesis):**
-    - //Naphthalene//, //Acenaphthylene//, //Acenaphthene//, //Fluorene//, //Phenanthrene//, //Anthracene//
-    - //C1-Naphthalenes//, //C2-Naphthalenes//, //C3-Naphthalenes//, //C1-Phenanthrenes//
-  * **Highest Potential for Natural Contribution Among this List:**
-    - //Perylene//
-**Important Disclaimer:**
+**Important Disclaimer:** These are generalised orderings. Actual properties and effects vary.
-These lists provide generalised orderings. The actual properties and effects of these PAHs can vary significantly. For regulatory purposes and detailed risk assessment, specific data and context are crucial.
 ----
 ===== Methods to Identify the Source of a PAH Mixture Found on Analysis =====
-Identifying the source of a mixture of the 22 Polycyclic Aromatic Hydrocarbons (PAHs) required by the Marine Management Organisation (MMO) involves "fingerprinting" techniques that compare the specific composition of PAHs in a sample to known source profiles. The comprehensive list of 22 PAHs provides a robust dataset for these methods.
+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.//)
-Here are some of the best methods:
   - **PAH Ratios (Diagnostic Ratios):**
-    - **Principle:** Relies on the fact that certain PAHs are formed in different proportions depending on the source. Ratios of specific PAH isomers or related compounds are calculated and compared to established ranges.
+    - **Principle:** Certain PAHs form in different proportions depending on the source.
-    - **Commonly Used Ratios:**
+    - **Commonly Used Ratios (examples; threshold values can vary in literature):**
-      - **Low Molecular Weight (LMW) PAHs / High Molecular Weight (HMW) PAHs:** Petrogenic sources tend to have higher LMW proportions; pyrogenic sources are HMW dominated.
+      - **LMW PAHs / HMW PAHs:** Distinguishes petrogenic vs. pyrogenic.
-      - **//Anthracene// / (//Anthracene// + //Phenanthrene//) (ANT/[ANT+PHE]):** Values <0.1 often suggest petrogenic sources, while values >0.1 suggest pyrogenic sources.
+      - **//Anthracene// / (//Anthracene// + //Phenanthrene//) (ANT/[ANT+PHE]):** <0.1 often petrogenic; >0.1 pyrogenic.
-      - **//Fluoranthene// / (//Fluoranthene// + //Pyrene//) (FLA/[FLA+PYR]):** Helps distinguish petroleum (<0.4), petroleum combustion (0.4-0.5), and biomass/coal combustion (>0.5).
+      - **//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]):** Values <0.2 may indicate petrogenic; 0.2-0.35 mixed/petroleum combustion; >0.35 combustion.
+      - **//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]):** Can help differentiate petroleum combustion (0.2-0.5) from grass/wood/coal combustion (>0.5).
+      - **//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).
-    - **Benefit of the 22 PAH list:** Provides all necessary parent PAHs for these ratios.
   - **Alkylated vs. Parent PAH Profiles:**
-    - **Principle:** Petrogenic PAHs are rich in alkylated homologues. Pyrogenic PAHs are dominated by parent (non-alkylated) PAHs.
+    - **Principle:** Petrogenic PAHs are rich in alkylated homologues (e.g., //C1-C3 Naphthalenes//); pyrogenic PAHs are dominated by parent compounds.
-    - **Application:** The MMO's list includes //C1, C2, C3-Naphthalenes// and //C1-Phenanthrenes//.
+    - **Application:** High alkylated/parent ratios suggest petrogenic sources.
-      - **High proportions of alkylated PAHs relative to parent PAHs** strongly suggest petrogenic contamination.
-      - **Low proportions of alkylated PAHs** point to pyrogenic sources.
-    - **Benefit of the 22 PAH list:** Explicit inclusion of alkylated series is crucial.
   - **Homologue and Isomer Patterns:**
-    - **Principle:** Detailed examination of the distribution of specific isomers within an alkylated series or the relative abundance of different parent PAHs can provide further clues.
+    - **Principle:** Detailed distributions within alkylated series or isomer patterns provide clues.
-    - **Benefit of the 22 PAH list:** Comprehensive analysis allows detailed pattern recognition.
   - **Multivariate Statistical Analysis:**
-    - **Principle:** Techniques like Principal Component Analysis (PCA), Positive Matrix Factorization (PMF), or cluster analysis can be applied to the full dataset of 22 PAH concentrations.
+    - **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.
-    - **Application:** PCA can group samples with similar PAH profiles. PMF can attempt to quantitatively apportion source contributions.
-    - **Benefit of the 22 PAH list:** More comprehensive data leads to more robust statistical analyses.
   - **Comparison with Source Libraries:**
-    - **Principle:** The PAH profile of the unknown sample is compared to a library of PAH fingerprints from known specific sources.
+    - **Principle:** Comparing the sample's PAH profile to a library of known source fingerprints.
-    - **Application:** Requires access to a relevant source library.
 ==== 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.
-  * **Weathering:** Environmental processes can alter PAH profiles over time, making source identification challenging.
+Combining these methods with the comprehensive 22 PAH data allows for more robust source identification.
-  * **Mixed Sources:** Sediments often contain PAHs from multiple sources, complicating interpretation.
-  * **Regional Variability:** PAH fingerprints for a source type can vary regionally.
-  * **Analytical Accuracy:** Accurate quantification of individual PAHs is critical.
-By using a combination of these methods, leveraging the detailed information from the analysis of all 22 MMO-required PAHs, environmental scientists can make more robust identifications of PAH contamination sources.