Content

Lead and Cadmium in Soils 1991

Introduction

Heavy Metals in the Environment

Heavy metals are natural components of soil. Most elements are only present in minimal, insignificant eco-toxicological concentrations in undisturbed locations in the greater Berlin area. A few heavy metals are important as trace elements for physiological processes in plants and animals.

Heavy metals are introduced into the eco-system by the manufacture and use of materials containing heavy metals as well as the disposal of this waste. Soil is contaminated by material from the air and by direct depositing of pollutants. The accumulation of contaminants is aided by the capability of soil to bind them with clay minerals or organic substances, for example.

Lead and cadmium are widely distributed in the environment and are considered particularly toxic elements. Their accumulation has multiple effects on the usability and functions of soil in the eco-system.

Effects of Cadmium

Cadmium is an especially toxic heavy metal that is very mobile in soil. Even minimal amounts in soil that has a low pH or humus level will result in cadmium uptake into plants. Levels exceeding guidelines for foodstuffs or feeds can result.

Effects of Lead

Lead is less mobile and is absorbed by plant roots only in exceptional cases. Contaminated soil can result in pollution by both elements onto the surfaces of plants. Even minimal contents in soil can negatively effect plant growth and damage soil organisms.

Very high lead or cadmium levels in playgrounds, allotment gardens and other areas can cause health risks for small children by oral ingestion. If heavy metal contamination exceeds the binding capability of the soil, there is a danger that heavy metal compounds can flow with percolation (seepage) into the groundwater.

Heavy metal soil contamination is particularly problematic because they are not degraded in soil. Heavy metals in soil cannot be permanently eliminated. At best they can be locally reduced by a redistribution in the eco-system or removed from circulation by immobilization.