Heavy Metals in Soil
A significant amount of research has been conducted into the transfer of impurities like heavy metals from fertilizers to soils and ultimately into the food chain. The extent of the problem, the degree of influence on the human body and potential solutions are the subject of active discussion at many levels (more information in the Health section).
The transferability of heavy metals, such as cadmium, into soils and plants, is complex and influenced by different factors. The type and characteristics of the soil, as well as the plant’s genetics, play important roles in determining the rate of transfer. In general, leguminous crops have the lowest rates of transferability. Cereals, pumpkins and umbelliferous plants (such as parsley and carrots) show a moderate degree of accumulation, while cruciferous vegetables (cabbage and radish), chenopodioideae (beetroot and spinach), nightshade (potato and tomato) and composite flowers (sunflower and chicory) exhibit higher rates .
It has been found that heavy metals do not distribute evenly across the plant. As such, the concentration in the main part of the plant may differ from that found in the roots. Limited movement of cadmium from the root system to the plant above ground may be the reason why cadmium concentration found in fruits and grains varies from that in leaves and roots.
The accumulation of cadmium in crops is a result of the close interaction of soil resources, plants and the environment. Cultivation must be done in a way that is mindful of potential sources of heavy metal contamination. Additionally, careful monitoring of human impact on the environment should be encouraged to better understand the factors that contribute to the accumulation of cadmium over a longer period of time.