Effect of beringite on cadmium and zinc uptake by plants and earthworms: More than a liming effect?

Abstract

Metal-contaminated soils are potentially harmful to plants, animals, and humans. Harmful effects are often related to the free-metal concentration in the soil solution. Immobilization is a potentially useful method to improve the quality of metal-contaminated soils by transforming free-metal ions into species that are less mobile and less toxic. The effect of many immobilizing products can be attributed to sorption on the surface of the material. Alkaline materials also enhance adsorption to soil particles by decreasing proton competition. Immobilization should preferably be evaluated independently of soil pH to discriminate between these processes. In this study, the immobilizing effect of beringite, an alkaline alumino silicate, was compared with that of lime. Plants (Swiss chard [Beta vulgaris L. var. cicla]) were grown on a soil contaminated with cadmium and zinc and treated with graded amounts of beringite or lime. Metal availability, as determined by a 0.01 M CaCl2 extraction, and metal uptake by plants strongly decreased in all treated soils. Beringite did not reduce metal availability more than liming when the obtained pH levels were similar. The effect of beringite can, therefore, be explained as a liming effect, at least for the duration of our experiment (10 weeks). The effect of beringite and lime on metal accumulation by earthworms (Eisenia veneta and Lumbricus rubellus) was small or not significant, although the CaCl2-extractable metal concentration in treated soils decreased by more than 90%. We conclude that immobilizing agents based on a liming effect can decrease metal uptake by plants, but they will hardly affect metal uptake by earthworms. Hence, these materials can reduce negative ecological effects of metal contamination on plants and herbivores, but not on earthworm predators.

Understanding the Effects of Soil Characteristics on Phytotoxicity and Bioavailability of Nickel Using Speciation Models

“…At pH close to 7, the EC50 of total Ni in CS is larger than in SS. The EC50 of total Ni in the organic matter and iron (hydr)oxides-rich sandy soil (OMFe) is significantly larger and is 2-3 times of that in E (%) ) 1 1 + (C/EC 50 ) n (1) SS and CS at the same pH (Figure 2), indicating a lower bioavailability and toxicity of Ni in the OMFe soil. The EC50 of total Ni in the OMFe soil at pH 5 is about the same as the EC50 in SS and CS at pH 6.…”

Immobilising of Cd, Pb, and Zn contaminated arable soils close to a former Pb/Zn smelter: a field study in Austria over 5 years

“…In comparison Pb was decreased by 76, 97, 97% and Cd by 63, 92 and 93%, respectively. It can be assumed that these reductions are mostly due to pH elevation and to a lesser extent to the provided surface for fixation (Oste et al 2001).…”

Copper mobility in contaminated soils of the Puchuncaví valley, central Chile

“…Lime and other alkaline materials are known to reduce Cu dissolution in contaminated soils if pH did not exceed 8.5 (Oste et al, 2001;Lombi et al, 2003;Ruttens et al, 2006). The effect of liming is based on the formation of new particles, i.e.…”