Cadmium in soils and cereal grains after sewage-sludge application on French soils. A review

Abstract

-Recycling sewage sludges as fertilisers on soils for crop production has several potential benefits such as providing large amounts of phosphorous and organic matter. However, the spreading of urban sewage sludge is a constant cause of controversy because it is known to introduce potentially toxic trace metals into the soil, particularly cadmium. In order to clarify this debate, this review article presents a synthesis of the results of several studies carried out in France on the impact of sewage-sludge spreading. This article reports mainly Cd results but also some results on other trace metals such as Cr, Cu, Hg, Ni, Pb and Zn. Two kinds of data are presented: (1) soil data including total metal contents and data from partial extraction to evaluate the phytoavailable fractions, and (2) plant data including metal content of wheat, a major agricultural crop. The field experiments involved very different amounts of applied sewage sludges and Cd. Indeed, three categories of experiments stand out, the first and second involving high amounts of applied Cd, and the third involving low amounts of applied Cd: (1) during the 1970s and '80s, sludges with a high trace metal content, especially Cd, were spread at the INRA trials at Couhins experimental farm on sandy soils and in the Vexin area on silty topsoils. The quantities of applied Cd were very high, ranging from 3600 g to 641 000 g per ha. Here, the results show a notable impact on total Cd contents of topsoil and cereal grains. (2) Sludges containing high levels of industrial cadmium were spread on acid soils in the Limousin region for more than twenty years up to 1998. Topsoil Cd contents were measured in fields where the cadmium input was highest, of 300 to 600 g Cd per ha. Here, a clear increase in the Cd content of cereal grains was found. (3) During the 1990s and 2000s, numerous experiments with sewage-sludge applications compatible with the new French regulations of 1998 were implemented. The amounts of applied Cd were therefore much lower, from 0.6 to 270 g/ha. Here, no impact was detected on the composition of cereal grains. This review article concludes that the application of huge quantities of sewage sludges in the 1970s and '80s had a clear and long-lasting effect on both soil and grain Cd compositions. Nonetheless, spreading sewage sludge in accordance with the new French regulations had no significant impact on soil and cereal-grain Cd concentrations.cadmium / cereal grains / phytoavailability / sewage sludge / soil / total content

Using Data Mining to Predict Soil Quality after Application of Biosolids in Agriculture

“…This leads us to the conclusions that for extractable Cd prediction, (i) the initial composition of biosolids is the strongest indicator; (ii) the maturation processes occurring during sludge composting are not enough to discriminate liquid and composted sludge; and (iii) no correct prediction on Cd bioavailability can be performed from total Cd content, as no clear relation can be established between available and total Cd. Finally, our long‐term in situ results confirm a recent review showing that biosolids applied in accordance with the 1998 French regulation had no significant impact on total soil Cd concentrations (Baize, 2009).…”

“…Total trace element concentrations in soils were systematically lower than threshold values accepted by French legislation (Voynet et al, 1998). In addition to the chemical forms in which each trace metal occurs, metal mobility and behavior into the soil are known to be governed by soil properties, such as the pH, or the abundance of constituents that can easily retain metals, such as iron and manganese oxides or organic matter (Baize, 2009).…”

Robust geostatistical prediction of trace elements across France

“…These classes were created according to their natural geochemical content of TEs, as deduced from previous studies (Atteia et al, 1994(Atteia et al, , 1995Baize, 1997Baize, , 2007Baize, , 2009Sterckeman et al, 2006). It is also known that land-use has a significant effect on the behaviour of certain TEs in sandy and crystalline soils because of management practises that affect pH (Mench et al, 1997;Baize, 2009) and TE mobility. For this reason we subdivided the parent material classes in which the pedogenesis generally leads to sandy and crystalline soils into forested and non-forested subcategories.…”

Cadmium accumulation in wheat grain as affected by mineral N fertilizer and soil characteristics

“…These studies were mainly conducted on soils to which either metal-contaminated sewage sludge or metal salt solution was added (Chaudri et al 2001;Kirkham 2006;Chaudri et al 2007;Baize 2009;Baize et al 2009); there is limited information on the Cd status of wheat grain from relatively unpolluted agricultural soils. There are several studies from western Canada about Cd accumulation under durum wheat cultivation Mitchell et al 2000;Gawalko et al 2001).…”