| Abstract | KB  Full paper
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Background, Aim and Scope:
The contamination of soils by heavy metals engenders important environmental and sanitary problems in the Northern France where a smelter was located since more than one hundred of years. It was one of the most important Pb production site in Europe until its closedown in March 2003. The process was using the fusion of ore and generated considerable atmospheric emissions of dust. Despite of an active environmental strategy, these emissions were still important in 2002 with up to 17 tonnes of Pb, 32 tonnes of Zn and 1 tonne of Cd. Over the years the generated deposits have led to an important contamination of the surrounding soils. Previous studies have shown pollutant transfers to plants, which can induce a risk for human and animal health. The objective of this study was to evaluate the consequences of the smelter closedown on the Cd and Pb contents of wheat (grain and straw) cultivated in the area.
Materials and Methods:
Paired topsoil and vegetable samples were taken at harvest time at various distances to the smelter. The sample sites were chosen in order to represent a large range of soil metal contamination. Sampling was realized on several wheat harvests between 1997 and 2003. 25 samples were collected before the smelter closedown and 15 after. All ears of about 1 m long of two rows were manually picked and threshed in the lab. Similarly, straw was harvested at the same time. Total metal contents in soil and wheat samples were quantified.
Results:
A negative correlation between metal concentrations in soil and the distance to the smelter was shown. The wheat grain and straw showed important Cd and Pb contents. The straw had higher metal contents than the grain. During the smelter activity, the grain contents were up to 0.8 mg kg-1 DM of Cd and 8 mg kg-1 DM of Pb. For the straw, maximum contents were 5 mg kg-1 DM of Cd and 114 mg kg-1 DM of Pb. After the smelter closedown we observed a very large decrease of Pb in the grain (82 %) and in the straw (91 %). A smaller decrease was observed for Cd in grain. Despite of this improvement, 80% of the studied sampled remained non acceptable compared to the European legislation values related to the human consumption, and this mainly due to a too high Cd content.
Discussion:
Results highlighted a difference in metal accumulation in the plant organs as well as a difference in metal uptake. The approach pointed out the importance of atmospheric fallout in the wheat contamination pathways for Pb. The smelter closedown has lead to a decrease of the Pb wheat contents. It is interesting to relate this finding with the lead blood levels of the children living close to the smelter.
Conclusions:
Those results are validating the importance of dust fallout in the plant contamination pathways. Before the closedown Pb measured in the plant was principally originating from the smelter dust emissions. It raised the question of the sanitary risks for humans and animals living in the surrounding area of the smelter.
Recommendations and
Perspectives:
In the literature, very few articles are considering the dust deposit in the crop contamination pathways. However, on highly contaminated sites, this way of contamination can be very important. Thus, it would be worthy to study the metal uptake of the plants by considering a contamination through the foliar system.
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