SEARCH Articles Figures Tables However, fly ash emissions from coal-fired power plants is probably a more important source of atmospheric heavy-metal pollution due to the fact that these power plants are the main sources of electricity for much of the world s population. In addition, sewage sludge is a major contributor of heavy-metal pollution in soils as land disposal of human waste becomes the only practical solution. It is not surprising that riverine particulates are so enriched in Pb, Zn, Cd, Cu, and Ni as soils polluted with atmospheric emissions from mining and smelting activities, and those altered by the addition of sewage sludge are swept into streams and rivers that eventually empty into the ocean. [Publishers Imprint] See Also: However, fly ash emissions from coal-fired power plants is probably a more important source of atmospheric heavy-metal pollution due to the fact that these power plants are the main sources of electricity for much of the world s population. In addition, sewage sludge is a major contributor of heavy-metal pollution in soils as land disposal of human waste becomes the only practical solution. It is not surprising that riverine particulates are so enriched in Pb, Zn, Cd, Cu, and Ni as soils polluted with atmospheric emissions from mining and smelting activities, and those altered by the addition of sewage sludge are swept into streams and rivers that eventually empty into the ocean.