What is the source of heavy metals and give reference
Heavy metals can be sourced from a variety of natural and anthropogenic activities, including mining, industrial processes, agricultural practices, and urbanization. Some common sources of heavy metals include:
1. Mining activities: Heavy metals such as lead, cadmium, and mercury are often found in high concentrations in mining areas where they are extracted from the earth.
2. Industrial processes: Industries such as smelting, coal combustion, and metal processing release heavy metals into the environment through emissions and waste disposal.
3. Agricultural practices: The use of fertilizers and pesticides containing heavy metals can lead to contamination of soil and water sources.
4. Urbanization: Urban areas are sources of heavy metal pollution due to vehicle emissions, waste disposal, and construction activities.
Reference: M. K. Ciffoni, A. M. Bernabé, R. P. Soares, "Heavy Metals from Natural and Anthropogenic Sources in Urban Surface Sediments—A Case Study: Cubatão City, Brazil," Water 2020, 12(11), 3139.