Metal Distribution and Biogeochemical Cycles of the Twenty-First Century

Globalization is leading to a dramatic modification in the distribution of metals that, when coupled with shifts in biogeochemical cycles induced by progressive climate change, will have environmental consequences far different than observed in past centuries. Human induced alteration of metal distribution, principally through mining activities, has been extensive for centuries. However, we are now reaching new levels of change through a combination of increased fossil fuel consumption (e.g., coal) and industrial processing of metals, which in concert with continued mining activities and transcontinental metal disposal practices is leading to an entirely new paradigm in metal deposition. In particular, the demand for metals used in urban development (iron and copper, for example) are hitting unprecedented levels owing principally to a rapid pace of advancement in China and India. Furthermore, redistribution of metals is also now occurring not only from mining and manufacturing but from global waste streams, where metal containing waste is often shipped from more to less developed countries for ‘disposal'. Shipment of electronic waste from throughout the world to receptors in China is a prime example of newly evolving global waste streams contributing to metal deposition. The environmental impact of metal redistribution on humans and ecosystems will be dependent largely on their fate and transport: Airborne release leads to local to global dissemination depending on physical form and atmospheric conditions; Release to soils/sediments or water will be dictated local biogeochemical and hydrological processes at receptor sites. In order to address and predict the ramifications of changing metal streams we will therefore need to couple knowledge of global flow paths, release processes, and physical-biogeochemical factors—ultimately a convolution of socioeconomic and biophysical processes.