How do heavy metals enter the environment during construction?

Heavy metals can enter the environment during construction primarily from machinery and construction waste. During construction activities, machinery such as trucks, bulldozers, and excavators are often used. These machines contain lubricants, hydraulic fluids, and other materials that can leak or spill, introducing heavy metals like lead, cadmium, and zinc into the surrounding environment.

Additionally, construction waste can contribute to heavy metal contamination. This may come from discarded materials, such as old paints, batteries, or metals from renovated structures, all of which can leach heavy metals into soils and water systems. Proper waste management and mitigation strategies are essential to minimize this pollution during construction processes.

In contrast, while organic matter decomposition can contribute organic pollutants, it is not a significant source of heavy metals. Natural groundwater discharge may also contain trace metals, but it is not a primary pathway during controlled construction activities. Atmospheric deposition can bring heavy metals into the environment, but this impact is typically diffuse and not as concentrated as that from direct construction-related sources. Therefore, the most direct and significant pathway for heavy metals during construction is indeed through machinery and construction waste.