Scotland's Marine Atlas: Information for The National Marine Plan

HAZARDOUS SUBSTANCES

What are hazardous substances?

Substances which accumulate in the environment and impact on wildlife are considered to be hazardous. Substances identified as a particular cause for concern include cadmium, mercury, lead, pesticides, polychlorinated biphenyls ( PCBs), polycyclic aromatic hydrocarbons ( PAHs) and brominated flame retardants ( PBDEs).

Hazardous substances are released to the environment as a result of human activities such as manufacturing, pest control and the burning of fossil fuels. Trace metals may also be released naturally by leaching from rocks and soils. Although the use of some substances has been banned ( PCBs and some brominated flame retardants) they continue to be present in the environment as a result of historical use.

The marine environment is the ultimate sink for these substances through direct introduction from marine activities such as dredge spoil dumping, transport via rivers or deposition from the atmosphere by solution at the surface or in rainfall. Inputs of selected substances to the marine environment via rivers and effluent discharges have been quantified for the OSPAR Rivers and Direct Discharges ( RID) programme since 1990.

Measuring hazardous substance inputs to Scottish marine waters

Hazardous substance inputs to the marine environment from rivers and effluents are estimated by measuring the concentration in the discharge and multiplying this by the flow to give the load. Inputs are reported by ICES sea areas. These are named SC1, SC2, SC2a, SC2b, SC3, SC4 and SC5 and are shown on the map opposite. If the concentration of a substance in the discharge is too low to be measured the estimated load assumes that the concentration is at the limit of detection. Inputs from the dumping of dredge spoil are measured separately.

Inputs of trace metals from discharges

Inputs of cadmium and mercury are often at concentrations too low to be measured so they are estimated from the limit of detection of the analysis. These estimates have decreased as improvements to analytical methods have lowered limits of detection so trends are difficult to quantify. In 2008 it was estimated that between 0.4 and 2 tonnes of cadmium and between 0.2 and 0.3 tonnes of mercury were discharged to Scottish coastal waters. In 2008 approximately 85 tonnes of copper, 35 tonnes of lead and 300 tonnes of zinc were discharged to the sea in Scotland. The highest inputs of all metals were from urban and industrial areas. Inputs of copper, lead and zinc have all decreased since monitoring began in 1990. Lead inputs decreased substantially following the introduction of unleaded petrol in 1988, and inputs of copper and zinc have decreased as a result of improvements to effluent treatment. There is considerable variability in the amount of decrease in different areas. For example, inputs of copper and zinc appear to increase in SC3 in 2000 however this is due to an increase in the number of discharges monitored rather than an actual increase in inputs.

The marine caged fish farm industry is a potential source of trace metals in less populated areas however they are not monitored as there is no aqueous discharge. Since 2007 inputs of copper and zinc from marine caged fish farms have been estimated from the trace metal content of the fish food, the amount used and the amount deposited on the sea bed through waste, plus the amount of copper-based antifoulants used to treat cage nets. These estimates show that fish farms are potentially a substantial source of copper and zinc compared to other inputs in the north and west of Scotland. However the metals released from fish farms are contained in particulate material deposited on the sea bed and it is not known what proportion can be taken up by animals and plants.

Intertidal mussel sampling

© SEPA

Inputs of Cadmium and Mercury to Scottish Sea Areas in 2008

Source: SEPA

Inputs of trace organic compounds

Most trace organic compounds are not soluble in water and are present below the limit of detection in discharges. Inputs of Lindane have been quantified as it is relatively soluble in water and present in measurable concentrations. Lindane (?-hexachlorocyclohexane ( HCH)) enters the environment through its use as an insecticide in a wide range of products. The use of lindane as an insecticide is declining and aqueous inputs to Scottish seas decreased from 225 kg in 1991 to 17 kg in 2008. Current inputs are highest in the Clyde sea area ( SC2).

Estimated inputs of Copper and Zinc from the marine caged fish farm industry

ICES Sea Area	Copper t/yr	Copper t/yr	Zinc t/yr	Zinc t/yr
	2007	2008	2007	2008
SC2	32.4	39.3	1.9	4.9
SC2a	16.2	32.4	4.0	11.1
SC2b	16.8	21.0	3.8	10.7
Total	65.3	92.8	9.6	26.7

Source: SEPA

Inputs of lindane from aqueous discharges to the sea in 2008

Source: SEPA

Trace metals in dredged sediments

Trace metals in dredge spoil

Trace metal inputs in dredge spoil deposited on the sea bed in Scotland have decreased since 2005 in all areas except the East Scotland coast where inputs of copper and zinc increased in 2009. This increase resulted from the disposal of dredge spoil from Peterhead which contained relatively high concentrations of copper and zinc.

Beaufort's Dyke

The Beaufort's Dyke, (692 sq.kms), was historically used to dump munitions. Recent underwater TV surveys highlight the abundance and widespread nature of material in the north east corner of the site and also beyond the boundary of the original dumping site. Records show various types of ammunition (shells, ammunition boxes, mines and other debris) within the site and at locations 5.5-9 km away. Some of the munitions contained (and may still contain) phosgene gas that will remain liquid at the pressures and temperatures at this site. The seabed in these locations varies from silty sand to coarser sand, mollusc shells and pebbles and much of the debris is colonised with flora and fauna indicating that it has not been disturbed for some time.

Summary of Tonnages 2005-2009

Source: Marine Scotland

Dredged sediment contamination (tonnes) for the Forth (2005-2009) Source: Marine Scotland	Dredged sediment contamination (tonnes) for the East Scotland Coast (2005-2009) Source: Marine Scotland	Beaufort's Dyke (rippled sand, burrowing anemone) © Marine Scotland
Dredged sediment contamination (tonnes) for the Clyde (2005-2009) Source: Marine Scotland	Dredged sediment contamination (tonnes) for the Moray Firth (2005-2009) Source: Marine Scotland	Sediment grabbing © SEPA

Location of OSPAR Riverine input and direct discharge monitoring sites and trace metal inputs by ICES Sea Area

Monitoring contaminants in the marine environment

Contaminants are measured in waters, sediments and biota (mussels and fish) to determine their long term fate. Water soluble contaminants may remain in solution. Less soluble contaminants are more likely to be incorporated onto particulate matter in the water column and deposited on the sea bed. Contaminants may be bio-accumulated, that is, absorbed into animal tissue by ingestion from particulate matter or absorption from solution.

Hazardous substances in water

Hazardous substance concentrations in seawater are compared to internationally and nationally agreed Environmental Quality Standards ( EQS). Environmental Quality Standards are set at a safe level below the concentration at which toxicity to sensitive organisms was observed, in laboratory tests.

Environmental Quality Standards for dissolved trace metals and lindane in marine waters (µg/l, annual average)

	Environmental Quality Standard µg/l
Cadmium	0.2
Copper	5.0
Lead	7.2
Zinc	40
Mercury	0.05
Lindane	0.02

Source: Water Research Centre, UK

Contaminant concentrations in Scottish estuaries and coastal waters are low compared to Environmental Quality Standards. Mercury concentrations are below the limit of detection (10 ng/L), and lindane concentrations are close to the limit of detection. Slightly elevated concentrations of cadmium, copper and zinc occur at sites close to localised inputs, with the highest concentrations in the Clyde and Forth estuaries where the main inputs are located.

2009 Cadmium in Water	2009 Lead in Water
2009 Zinc in Water	2009 Copper in Water
2009 ? HCH in Water	2009 ? HCH in Biota

Hazardous substances in sediments and biota

Contaminants in sediments and biota are compared with international standards developed by OSPAR⁽¹⁾. Contaminant concentrations are considered to be low if they are below the Background Assessment Concentration ( BAC) ¹ and slightly elevated if they are greater than the BAC but less than the Environmental Assessment Criteria ( EAC). Contaminant concentrations are considered to be of concern if they exceed the EAC, that is, they may cause adverse biological effects in marine species. Concentrations of trace metals and PAH are considered to be of concern towards other marine species if they exceed the Effects Range Low ( ERL) ² in sediments. Trace metals are of concern towards humans if they exceed the EC maximum acceptable dietary level in biota.

Trace metal concentrations in sediments are expressed as concentrations relative to aluminium and trace organic contaminant concentrations are expressed in concentrations relative to organic carbon to compensate for different sediment types. Trace organic contaminant concentrations in fish livers are expressed in concentrations relative to lipid to allow for differences in fat content.

There are no standards for copper and zinc in biota or for brominated flame retardants (polybrominated diphenyl ethers, PBDEs) in sediments and biota. Therefore the environmental significance of the concentrations found can not be assessed, but spatial comparisons can be made.

^{1 BACs were derived from observed background concentrations for naturally occurring substances, and are based on low concentrations which are measurable and close to zero for man-made substances.
2 The Effects Range Low is the 10 percentile concentration of each contaminant above which toxic effects were observed.}

2008 Copper in Sediments normalised to 5% AI	2009 Copper in Biota
2008 Zinc in Sediments normalised to 5% AI	2009 Zinc in Biota

OSPAR assessment criteria for contaminants in sediment, mussels and fish liver

Group	Substance	Sediment			Mussels			Fish
		µg/kg dry weight normalised to 2.5% TOC			µg/kg dry weight			ug/kg lipid weight
		< BAC	BAC - EAC	> EAC	< BAC	BAC - EACa	> EACa	< BACb	BACb - EACa	> EACa
PCB	CB153	<0.19	0.19 - 40	>40	<0.6	0.6 - 80	80	<0.1	0.1 - 1,600	>1,600
	CB118	<0.17	0.17 - 0.6	>0.6	<0.6	0.6 - 1.2	1.2	<0.1	0.1 - 24	>24
	CB52	<0.12	0.12 - 2.7	>2.7	< 0.75	0.75 - 5.4	5.4	< 0.08	0.08 - 108	>108
Group	Substance	Sediment			Mussels
		µg/kg dry weight normalised to 2.5% TOC			µg/kg dry weight
		< BAC	BAC - ERL	> ERL	< BAC	BAC - EAC	> EAC
PAH	Pyrene	<24	24 - 665	>665	<9	9 - 100	100
Group	Substance	Sediment			Mussels			Fish
		µg/kg dry weight normalised to 5% Al			µg/kg dry weight			µg/kg wet weight
		< BAC	BAC - ERL	> ERL	< BAC	BAC - EC	> EC	< BAC	BAC - EC	> EC
Trace Metals	Cadmium	<310	310 - 1,200	>1,200	<1,940	1,940 - 5,000	5,000	<26	26 - 1,000	>1,000
	Mercury	<70	70 - 150	>150	<140	140 - 2,500	2,500	<35	35 - 500	>500
	Lead	<38,000	38,000 - 47,000	>47,000	<1,520	1,520 -7,500	7,500	<26	26 - 1,500	>1,500
	Copper	<27,000	27,000 - 34,000	>34,000
	Zinc	<122,000	122,000 - 150,000	>150,000
Pesticide	?- HCH	<0.13	0.13 - 3.0	>3.0	<0.97	0.97 - 1.45	1.45

Note: Cadmium and lead are measured in fish liver whereas mercury is measured in fish flesh.
^aEAC^passive, calculated from the EAC for sediment.
^bBAC for fish liver is on a wet weight basis.

Trace metals in biota and sediments

Trace metals are measured in blue mussels ( Mytilus edulis) and fish, and these data need to be assessed separately. This is because mussels are short-lived, sessile and shore-based, with relatively low fat content, whereas fish are longer-living, mobile and where livers are analysed, have higher fat content. Fish such as dab, plaice and flounder are collected in coastal waters while in deep waters offshore, other species are collected. These differences result in different metal concentrations, and for this reason, different background assessment concentrations are used. Hence while cadmium concentrations are close to background in mussels they are elevated in fish livers at all sites. Lead is close to background in mussels in less populated areas but slightly elevated in the more industrialised areas and in the majority of fish samples. Mercury is close to background in mussels at most sites on Shetland and most sites on the west coast but is elevated on the east coast and several sites on the west coast. Mercury is slightly elevated in all fish except the sample caught in the Moray Firth.

The geographical distribution of copper in mussels is similar to that for lead, although concentrations of copper are much lower. The relatively high concentrations of copper in mussels on Islay may be related to inputs from several distilleries in this area. There are relatively high concentrations of zinc in mussels on Shetland and in the Forth Estuary plus a few isolated sites on the west coast. Discharges of zinc are low in these areas, and the elevated zinc concentrations may be linked to local mineralisation.

Trace metal concentrations in sediments are highest in the Inner Firth of Clyde where all samples exceed the Effects Range - Low for all metals, except cadmium. Cadmium concentrations are low in sediments compared to other metals and close to background at most sites. Forth estuary and Firth of Forth sediments all exceed the Effects Range - Low for mercury and exceed the Background Assessment Criteria or Effects Range - Low for lead. The trace metal concentration of coastal sediments is low. However, some sites exceeded the assessment criteria when normalised to aluminium, as their aluminium content was low.

The data highlight an interesting contrast in copper and zinc concentrations in mussels and sediments between the Forth and Clyde Estuaries. Concentrations of these metals are higher in sediments in the Clyde than in the Forth, but higher in mussels in the Forth compared to the Clyde. This may be because the Forth is a more turbid estuary due to the stronger tides which mix the sediments into the water column. This will result in particulate bound metals being more available to filter feeders such as mussels.

2008 Cadmium in Sediments normalised to 5% AI	2008-09 Cadmium in Biota
2008 Lead in Sediments normalised to 5% AI	2008-09 Lead in Biota
2008 Mercury in Sediments normalised to 5% AI	2008-09 Mercury in Biota

Trace organic compounds in biota and sediments

Lindane (?- HCH) concentrations in mussels are low and close to background at the majority of sites. Concentrations are slightly elevated at a few sites in remote areas which may be related to localised inputs.

Polychlorinated biphenyls ( PCBs) include a range of compounds of varying toxicity. CB153 (the identifying number relates to the number and distribution of chlorine atoms) is the most abundant but one of the less toxic compounds whereas CB52 and 118 are less abundant but more toxic. The least toxic PCB ( CB153) is above the BAC at all biota and most sediment sites but below the EAC at all sites. The most toxic PCB ( CB118) is present above the EAC in all mussels and is above the EAC in sediments in the Inner Firth of Clyde and some sites in the Forth, Minch Malin and the Moray Firth. CB52 is above the EAC in mussels and one sediment sample in the Firth of Clyde. The overall picture is that PCBs are widespread in sediments and biota but that concentrations are only of concern, that is, adverse biological effects may be observed in marine species, in the Firth of Clyde.

Polycyclic aromatic hydrocarbons ( PAHs) also include a range of compounds of varying toxicity. They are described here using pyrene which is easily measurable and has agreed assessment criteria. Pyrene is close to background concentrations in coastal and offshore sediments and in mussels collected in the North West. It is slightly elevated in inshore sediments and mussels located near more populated and industrialised areas. Pyrene exceeds the EAC and is therefore of concern in mussels in the Forth and Clyde estuaries and exceeds the ERL in Firth of Clyde sediments, indicating that adverse biological effects in marine species may be observed in these areas.

Polybrominated diphenyl ethers ( PBDEs) are synthetic compounds used as brominated flame retardants in electronic equipment, textiles and furniture, and these are discharged to marine waters via industrial effluents and waste water treatment works. PBDEs consist of technical mixtures of approximately 20 compounds, of which the most frequently detected in sediment and fish liver is BDE47. PBDEs were not detected in any of the sediments from East Shetland, West Shetland and East Scotland. PBDEs were detected most frequently in sediment and fish from the Clyde region, although even here they were not found in all samples. PBDEs were also detected in three species of deep water fish indicating that they are widespread in the environment. Concentrations in deep water fish were low and comparable to those found in shallow water species from the Minches and Malin Sea region.

Dioxins are a particularly toxic group of organic compounds which are formed as by-products in industrial processes (e.g. during the manufacture of industrial chemicals such as pentachlorophenol and chlorobenzenes, and in paper production). They are also produced during incineration processes, both industrial, including power generation and cement manufacture, and natural (e.g. forest fires). A recent survey indicated that dioxins were present either below the limit of detection or at low concentrations in biota and sediments in the Forth and Clyde Estuaries and in the Firth of Forth.

CB153 in Sediments normalised to 2.5% TOC	CB153 in Biota
2008 CB52 in Sediments normalised to 2.5% TOC	2009 CB52 in Biota
CB118 in Sediments normalised to 2.5% TOC	CB118 in Biota

Impact of hazardous substances in sediments

The biological effect of hazardous substances in sediments is determined by bioassays using the crustacean Corophium volutator and the polychaete worm Arenicola marina. Both animals live in the sediment, and while A. marina ingests sediment, C. volutator grazes on sediment particles. In both bioassays, the animals are exposed under controlled conditions to sediment samples, and mortality is measured after 10 days. Toxicity is determined by the number of test organisms which survive in the test sediments compared to uncontaminated control sediment samples.

Mortality of the test organisms was significantly greater than the control sample at two adjacent sites in the inner Firth of Clyde, between Wemyss Bay and Toward Point. The sediments from the Inner Firth of Clyde contained the highest levels of contaminants and the bioassay results indicate that adverse effects of contaminants are possible at these sites, in line with the comments above on contaminant concentrations. However analysis of the benthic community in the sediments does not show any adverse impacts. This illustrates the difficulties in drawing conclusions from laboratory tests and relating these to the marine environment, where the complexity of marine benthic communities is such that these may adapt and develop tolerances to their local conditions. The benthic community is at high or good status at the majority of sites with some at moderate status in the Forth, outer Clyde and Minches and one at poor status in the Forth estuary. It is thought that seabed damage due to fishing and the stresses of natural changes in coastal and estuarine environments, for example salinity, are the causes of downgrading at these sites rather than contaminants.

Impact of hazardous substances on fish and shellfish

A range of techniques are used to determine the sub lethal effects of hazardous substances in biota. Contaminant specific techniques include the determination of cytochrome P450 enzymes (specifically EROD [7-Ethoxyresorufin-O-deethylase] in fish exposed to hydrocarbons and imposex in dog whelks exposed to tri-butyl tin. Recent research is investigating the use of genomics to determine the sub lethal impacts of contaminants on mussels. These biological effects techniques are described in more detail overleaf.

Trends in hazardous substances

Hazardous substance concentrations in water have decreased over time and are now low, reflecting reductions in inputs, which are well controlled. Hazardous substance concentrations in sediments reflect integration over many years, including historical contamination, and remain high in some industrialised estuaries and harbours. Hazardous substance concentrations in mussels are decreasing in response to changes in inputs, but remain elevated for some substances due to their accumulation from contaminated sediments.

Pyrene in Sediments normalised to 2.5% TOC	Pyrene in Biota
BDE47 in Sediments normalised to 2.5% TOC	BDE47 in Biota
Classification of sediment dwelling organisms	Sediment toxicity to corophium