Friday, 2 September 2016

Glasgow’s got the Hydrocarbon Hump: Urban Pollution Transport Corridors in the River Clyde...by Christopher Vane

Recent research on the surface sediment chemistry of the upper River Clyde, Glasgow reaches and tributaries as well as tidal estuary has shown that Glasgow’s urban tributaries have got the ‘hump’. Organic geochemists call the ‘hump’ a fancy name, the unresolvable complex mixture (UCM), because it’s comprised of thousands of hydrocarbon compounds which are difficult to separate using standard analytical methods such as gas-chromatography (GC).  The largest humps are usually found in soils and sediments which have accumulated weathered crude oils and or refined oil products such as engine and industrial lubricants. These leak into soils and are washed into river sediments via road run-off .


BGS geochemists Drs’ Chris Vane,  Alex Kim and Raquel dos Santos extracted oil from sediments in the Clyde found that nearly all the samples in and around Glasgow had the hump and that the hump disappeared in sediments collected a few kilometres downstream of the city only to return again in and around Greenock and Port Glasgow which are situated toward the outer estuary. 

This suggests that these areas are either receiving modern day fugitive hydrocarbon pollution or that legacy hydrocarbon pollution is being remobilised or both. Other eco-toxicological studies have suggested that the UCM (hump) is toxic and has known negative health effects on sediment dwelling biota.  We also discovered that with a few exceptions, sediments from the more rural upper Clyde didn’t have the hump but were comprised of straight chain hydrocarbons called n-alkanes which show up as nice straight peaks that are easy to separate and mainly sourced from the natural peat and soil in the catchment  suggesting no or very low man-made hydrocarbon input.

Other  new investigations by the Organic Geochemistry team at BGS  focus on understanding the  concentration and possible health effects from persistent organic pollutants in Glasgow’s soils measurement and tracking the distribution of  the toxic metal mercury through the Clyde river-estuarine continuum  as well as assessing  the transport of natural soil carbon from land to out to sea.  The findings have just been submitted to Earth and Environmental Science Transactions of the Royal Society of Edinburgh special issue on the Clyde Basin organised by BGS’s Diarmad Campbell and Fiona Fordyce.  

Taken together the existing and new organic pollution studies (see references below)  show us that the urban tributaries act as conduits, both receiving and occasionally delivering polluted sediment to the main river and then out to sea. Additionally, we show that the impact of the anthropogenic pollution extends down-stream but not upstream due to the flow of water and the presence of tidal barriers which can impede sediment movement.

Published References on Clyde estuary sediments:

Vane, C.H., Chenery, S.R., Harrison, I., Kim, A.W., Moss-Hayes, V., Jones, D.G. 2011. Chemical Signatures of the Anthropocene in the Clyde Estuary, UK: Sediment hosted Pb, 207/206Pb, Polyaromatic Hydrocarbon (PAH) and Polychlorinated Biphenyl (PCB) Pollution Records.  Philosophical Transactions of the Royal Society (A) 369, 1085-1111. DOI: 10.1098/rsta.2010.0298

Vane, C.H. Yun-Juan Ma, She-Jun Chen and Bi-Xian Mai. 2010. Inventory of Polybrominated diphenyl ethers (PBDEs) in sediments of the Clyde Estuary, U.K. Environmental Geochemistry & Health, 32(1), 13-21. DOI: 10.1007/s10653-009-9261-6

Vane, C.H., Harrison, I., Kim, A.W. 2007. Assessment of Polyaromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) in surface sediments of the Inner Clyde Estuary, U.K. Marine Pollution Bulletin, 54, 8, 1301-1306. DOI: 10.1016/j.marpolbul.2007.04.005

New BGS Research on River Clyde and Glasgow Soils: 

Vane, C.H., Moss-Hayes, V., Kim, A.W., Edgley., J Bearcock.  Mercury (Hg), n-alkane and unresolved complex mixture (UCM) hydrocarbon pollution in surface sediment across rural-urban-estuarine continuum of the Clyde, UK. Earth and Environmental Science Transactions of the Royal Society of Edinburgh (In Review)

Kim, A.W., Vane, C.H., Moss-Hayes, V. Berriro, D.B., Fordyce, F., Everrett, P. Nathanail, P.C. Polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) in urban soils of Glasgow, UK. Earth and Environmental Science Transactions of the Royal Society of Edinburgh. (In Review).

Lopes dos Santos and Vane, C.H. Tracking natural organic carbon in the River Clyde using glycerol dialkyl glycerol tetraethers (GDGT). Earth and Environmental Science Transactions of the Royal Society of Edinburgh (In Review)
 
 

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