Editing River Clyde (section)

== Pollution ==
The British Geological Survey has identified and evaluated organic chemical pollutants in the sediment of the Clyde estuary.<ref name="Assessment of Polyaromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) in surface sediments of the Inner Clyde Estuary, UK">{{Cite journal |url=http://nora.nerc.ac.uk/990/|title= Assessment of Polyaromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) in surface sediments of the Inner Clyde Estuary, U.K.|last1= Vane |first1=C.H. |last2=Harrison |first2=I. |last3=Kim |first3=A.W.|date= 2007|journal= Marine Pollution Bulletin|doi=10.1016/j.marpolbul.2007.04.005|volume=54|issue= 8|pages=1301–1306|pmid= 17553529}}</ref><ref name="Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records.">{{Cite journal |url=http://nora.nerc.ac.uk/13301/1/Vane_et_al__Clyde_Anthropocene_2011.pdf | title= Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records.| author= Vane, C.H., Chenery, S.R., Harrison, I., Kim, A.W., Moss-Hayes, V., Jones, D.G | date= 2011 |journal= Philosophical Transactions of the Royal Society A | doi=10.1098/rsta.2010.0298 | pmid=21282161 | volume=369 | issue= 1938| pages=1085–111| s2cid= 1480181}}</ref><ref name="Inventory of Polybrominated diphenyl ethers (PBDEs) in sediments of the Clyde Estuary, U.K.">{{Cite journal |url=https://www.researchgate.net/publication/24258695 | title= Inventory of Polybrominated diphenyl ethers (PBDEs) in sediments of the Clyde Estuary, U.K.| author= Vane, C.H., Yun-Juan Ma, She-Jun Chen and Bi-Xian Mai. | date= 2010 |journal= Environmental Geochemistry & Health | volume= 32| issue= 1| pages= 13–21| doi= 10.1007/s10653-009-9261-6| pmid= 19347590| s2cid= 102768}}</ref> Surface sediments from the Glasgow reaches of the Clyde and [[Cuningar Loop|Cuningar]] to [[Milton, West Dunbartonshire|Milton]], were previously found to contain [[polyaromatic hydrocarbons]] (PAH) from 630&nbsp;μg/kg to 23,711&nbsp;μg/kg and [[polychlorinated biphenyl]] (PCB) in the range of 5 to 130.5&nbsp;μg/kg, which puts these sediments in the range classified as "non-toxic."<ref name="Assessment of Polyaromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) in surface sediments of the Inner Clyde Estuary, UK" /> However, a later study showed PCB concentrations as high as 5,797&nbsp;μg/kg, which is above published threshold levels for such  chlorinated compounds.<ref name="Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records."/> A comparison between individual PAH compounds that have different thermal stabilities shows that the source of PAH pollution in the Clyde is different in different parts of the river. PAH in the inner Clyde (Cuningar to Milton) are from combustion sources (vehicle exhaust, coal burning), whereas PAH in the outer Clyde are from petroleum spills.<ref name="Assessment of Polyaromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) in surface sediments of the Inner Clyde Estuary, UK" /><ref name="Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records."/>

The amount and type of sedimentary pollution in the Clyde reflects the area's industrial history.<ref name="Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records."/> In order to assess how the nature of the pollutants has changed over time, from 1750 to 2002, seven sediment cores of one metre's depth were collected, and dated using lead concentrations and changing lead isotope ratios. The sediments showed a long but declining history of coal usage and, beginning around the 1950s, an increasing reliance on petroleum fuels. The decline of hydrocarbon pollution was followed by the appearance of PCB concentrations in the 1950s. Total PCB concentration levels peaked in the period 1965 to 1977, and declined beginning in the 1990s.<ref name="Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records."/> The [[Polmadie]] [[Burn (landform)|Burn]], which flows into the Clyde at [[Richmond Park, Glasgow|Richmond Park]], remains heavily contaminated by [[hexavalent chromium]], to the extent it turned bright green in 2019,<ref name=flushed>{{cite web | url = https://www.bbc.com/news/uk-scotland-glasgow-west-47295613 | title = Harmful chemicals in green Glasgow burn to be flushed|work=BBC News |date=19 February 2019 |access-date=27 April 2021}}</ref> and yellow in 2021.<ref>{{cite news |last=Suter |first=Ruth |date=April 26, 2021 |title=SEPA called to investigate 'toxic' Glasgow burn |url=https://www.glasgowtimes.co.uk/news/19260608.sepa-called-investigate-toxic-glasgow-burn/ |work=The Glasgow Times |location= |access-date=April 27, 2021}}</ref>

Although pollution from heavy industry and power generation has been decreasing, there is evidence that human-made pollution from new synthetic compounds in electrical products and textiles has been increasing.<ref name="Inventory of Polybrominated diphenyl ethers (PBDEs) in sediments of the Clyde Estuary, U.K."/> The amounts of 16 [[polybrominated diphenyl ether]] (PBDE) compounds used as flame retardants in televisions, computers, and furniture upholstery were measured in sediment cores collected from six sites between Princes Dock and Greenock. Comparison of the amounts of PBDE compounds revealed a decline in certain compounds, in line with the European ban on production of mixtures containing environmentally harmful PBDE with eight and nine [[bromine]] atoms. At the same time, there was an increase in the amounts of the less harmful mixture, composed of ten bromine atoms.<ref name="Inventory of Polybrominated diphenyl ethers (PBDEs) in sediments of the Clyde Estuary, U.K."/>