It transfers only slowly to shoots or fruits. As a result, root vegetables such as carrots or sweet potatoes could potentially have the highest concentrations of lead.
This book gives a current overview of all facets of urban soils. Different urban land-use types in a number of examples worldwide are introduced. Many examples. Human activity goes hand in hand with urban and industrial development. It leads to the emergence of new industrial technologies, construction materials and.
Leafy vegetables, such as Swiss chard, are next. Fruits such as tomatoes are the least likely to contain lead absorbed from the soil.
To determine lead concentrations in the vegetables we tested, the edible portions of the plants were harvested as each plant type reached maturity at the end of the growing season. Also, representative soil samples were collected before adding compost, at planting, and at harvesting from each plot.
Our study found that adding compost at the rate we used diluted the overall lead concentration in the soil by anywhere from 29 to 52 percent. This reduced the amount of lead absorbed by the vegetables.
Also, the phosphorus in compost and iron oxides in some compost materials can help hold lead in the soil, which reduces its availability to plants. Finally, compost increased the soil fertility and resulted in larger vegetables, diluting the concentration of lead in them.
In analyzing the edible portions of the vegetables using the laboratory washing method described below , we found no relation between the concentration of lead in the soil and the concentration of lead in the vegetables. In , on the soil with relatively low levels of lead, the addition of compost had no effect on the lead concentrations in either Swiss chart, tomatoes, or sweet potatoes.
This is most likely because the lead concentration in the produce samples was low, close to the background lead concentration levels.
In , on the soil the relatively high levels of lead, the addition of compost reduced the lead concentration in Swiss chard by 59 percent and in carrots by 20 percent. Since the lead concentration in the soil and produce was high enough in this situation, we could see the compost treatment effectiveness.
On the other hand, the lead concentration in tomatoes was unaffected by the addition of compost, even at this location. Fruits, such as tomatoes, have very low lead concentrations under almost any conditions, so it is not surprising that the compost treatment did not affect lead uptake in tomatoes. The concentration of lead in the vegetables does not necessarily reflect total lead uptake by that vegetable.
In , one of the main reasons for the lower concentration of lead in Swiss chard and carrots in the compost-treated soil is that the vegetables were much larger in the treated soils.
This diluted the concentration of lead in the vegetables, while the absolute amount of lead in the vegetables was not significantly different between the compost-treated and untreated soils. This result indicates that an increase of total biomass of vegetables could be an effective means of reducing potential lead transfer to humans. The various cleaning methods made a significant difference in lead concentrations of Swiss chard and tomatoes but not for carrots.
Swiss chard cleaned with the kitchen cleaning method contained 2. Similarly, kitchen-cleaned tomatoes had 3. Soil column leaching tests were carried out and they indicated that zinc has a higher mobility in the soils than lead. With this knowledge of heavy metal mobility in soils, the soil decontamination schemes can be designed or the potential impact of these soils can be evaluated. Open PDF.
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Key: Open access content Subscribed content Free content Trial content. Abstract: Abstract Since an increasing number of urban dwellers have come to recognize the close relationship between urban soils and water and air quality, as well as the growing popularity of urban agriculture, concern regarding soil contamination is on the increase. However, from the time of the Industrial Revolution onwards, both the scale of urban development and the degree of soil contamination rapidly increased and involved an ever widening spectrum of c- taminants.
With constraints on the supply of land for new urban development in many countries, it is becoming increasingly necessary to re-use previously dev- oped brownfield sites and to deal with their accompanying suites of contaminants.
The author, Helmut Meuser, is Professor of Soil Protection and Soil Clean-up at the University of Applied Sciences, Osnabruck and is one of Europe's foremost experts on contamination from technogenic materials in urban soils. He has many years' experience of research in Berlin, Essen, Osnabruck, other regions of Germany, and several other countries.