Adsorption—desorption and/or precipitation—dissolution processes of zinc in soils

Sequential sorption of lead and cadmium in three tropical soils

“…It is also interesting to note that the trend of Pb:Cd NERs of the soils (Oxisol > Ultisol > Mollisol) paralleled the pro portions of variable charged surfaces (oxidic minerals, 1:1 phyllosilicates, and organic matter), and were opposite CEC trends (Table 1). Therefore, on a relative basis, compared to Cd, Pb appeared to have a very high specificity for variable charged surfaces compared to constant surface charge mate rials (Brummer et al, 1983;Forbes et al, 1976;Jenne, 1968;McKenzie, 1980). In Figs.…”

Factors influencing metal bioavailability in soils: preliminary investigations for the development of a critical loads approach for metals

“…Metals may also be precipitated as metal hydroxides, removing OH -ions from solution (Basta and Tabatabai, 1992). Precipitation is unlikely to occur in acidic conditions and unless large quantities of both anions and cations are present: Brümmer et al, (1983) report that very high concentrations of Zn can be adsorbed before precipitation occurs. Similarly, Boekhold et al (1993) state that precipitation of Cd is unlikely to occur in neutral and acid soils except where very high concentrations of carbonate, sulphate or phosphates occur.…”

“…Whilst recognising the importance of precipitation in the partition of metals between the solid and solution phases, there are analytical and theoretical problems in extrapolating the concept of solubility products to precipitation reactions in natural soils. Furthermore, it has been shown that the concentrations of elements in the soil solution cannot be explained by solubility isotherms (Brümmer et al, 1983;Garcia-Miragaya, 1984). Natural soil-water systems are known to be much more complex than those in which solubility products are determined, namely solutions in equilibrium with pure compounds.…”

Zinc-enriched fertilisers as a potential public health intervention in Africa

“…Such soils are commonly defined as having a Zn concentration extractable by ethylene diamine tetra-acetic acid (EDTA) or diethyl triamine penta-acetic acid (DTPA) less than 1.5 and 1.0 mg kg −1 DW of soil, respectively (Trierweiler and Lindsay 1969;Lindsay and Norvell 1978). Low phytoavailability of Zn can result from low soil Zn concentrations or the influence of soil characteristics that limit Zn solubility such as high pH values or large concentrations of available phosphate or CaCO 3 (Brümmer et al 1983;Graham et al 1992;White and Zasoski 1999;Cakmak 2002Cakmak , 2004Alloway 2008;Lu et al 2011). Deficiency of Zn on cultivated soils is widespread, affecting >50 % of soils in India, Pakistan and Turkey, >30 % of soils in China and most soils in Western Australia and Africa (Alloway 2008).…”