Mediaeval lead pollution in the River Ouse at York, England

The City of York in northern England has a long history of being flooded by the River Ouse. Excavations of a 9 m sedimentary profile were carried out by the York Archaeological Trust on the site of a pumping station associated with a flood prevention scheme at North Street on the south-west bank of the River Ouse. This profile records evidence of human activity and episodic river sedimentation over a period from the 2nd to the 14th century AD. Anthropogenic materials in the profile include waterfront timber and wattle structures, and dumps of organic domestic debris and industrial waste. Evidence of historic floods is preserved in interleaved alluvial deposits. This study reports on the degree of lead (Pb) contamination at the site from Roman to Mediaeval times and the sources of both alluvial and manufactured lead deposited in the profile. Archaeological, sedimentological, geochemical and mineralogical evidence suggest that Yorkshire Dales mining activity during the 9th-13th centuries AD may have both directly and indirectly caused lead contamination of the alluvial deposits at North Street.