Historic metal mining inputs to Tees River sediment

Historic metal mining has greatly influenced sediment delivery and metal contamination in the Tees River Basin. Investigations of metal-contaminated overbank river sediment show that sediment-borne metal concentrations decrease downstream of mining areas. Metalliferous mineralogy also changes: sulphides and carbonates are abundant in the upstream part of the basin, and both decline and disappear downstream where iron oxyhydroxides dominate. Mineral compositional and textural information can be used to trace sources of mining-related contaminated sediment. Sulphides, carbonates, and oxyhydroxides which pseudomorph ore deposit minerals, are interpreted to be derived from outcropping ore bodies and mine-waste tips. The relative abundance of these grains suggests that the ore bodies and mine-waste tips are still important sources of metal pollutants. This is corroborated by morphological mapping and coring of Tees floodplain sequences, which also suggests that metal-contaminated alluvium downstream has experienced limited re-working.