“…Many trace elements are now being mined at a pace which exceeds their natural mobilisation rates by greater than an order of magnitude. For example, the catchment of San Francisco Bay has been radically altered through extensive urbanisation, the introduction of massive water management schemes, the agricultural development of the naturally arid Central Valley of California, and the loss of some 96% of the historical area of wetlands Wright and Phillips, 1988). The contributions of anthropogenic ally-derived metals to the total metals present have been quantified for certain local environments, and are seen to be very considerable for many of the more toxic elements (Fig.…”