Heavy metal availability in soil amended with composted urban solid wastes

Area of Science:

• Environmental Science
• Soil Science
• Agronomy

Background:

• Composting solid wastes is a common practice for soil amendment.
• The source of compost can influence soil properties and metal bioavailability.
• Time elapsed after compost application affects metal availability in soil.

Purpose of the Study:

• To evaluate the impact of composted solid waste doses on soil pH and metal (Zn, Cu, Mn, Pb, Ni) availability.
• To compare the effects of compost from urban (Rio de Janeiro) versus rural (Coimbra) sources.
• To examine the influence of time on metal availability after soil amendment.

Main Methods:

• Soil amendment with increasing doses of composted solid wastes from two different Brazilian cities.
• Analysis of soil pH and DTPA-extractable heavy metals (Zn, Cu, Mn, Pb, Ni).
• Evaluation of metal availability at different time intervals post-compost application.

Main Results:

• Increased compost application rates significantly raised soil pH and the availability of Zn, Cu, Pb, and Ni.
• Compost from the urban source (Rio de Janeiro) resulted in higher soil pH and metal availability compared to the rural source (Coimbra).
• Longer intervals between compost application and soil sampling correlated with increased availability of Zn, Cu, Mn, and Pb.

Conclusions:

• Composted solid waste application effectively increases soil pH and the availability of essential and potentially toxic metals.
• The origin of compost is a critical factor, with urban sources potentially posing higher risks due to greater metal contamination.
• Time is a significant factor influencing metal bioavailability in amended soils, necessitating careful consideration in risk assessments.