Duquesne, S., Newton, L. C., Giusti, L., Marriott, S. B., Stärk, H. J., & Bird, D. J. (2006). Evidence for declining levels of heavy-metals in the Severn Estuary and Bristol Channel, U.K. and their spatial distribution in sediments. Environmental Pollution, 143(2), 187-196. https://doi.org/10.1016/j.envpol.2005.12.002