Effects of sterilization on the chemical forms of heavy metals in soils

Abstract

We used sequential extraction to investigate changes in the amounts of six chemical forms of manganese, cobalt and cadmium in soil samples after chloroform fumigation. The six forms were designated as follows: exchangeable, dilute-acid-soluble, manganese-oxide-occluded, organically bound, iron-oxide-occluded and residual. For all three metals, the decreases in the amounts of manganese-oxide-occluded forms were equivalent to the sum of the increases in the amounts of exchangeable and dilute-acid-soluble forms. The amounts of the other three forms did not change significantly after fumigation. These results indicate that some of the cobalt and cadmium in the manganese oxides was converted into exchangeable and dilute-acid-soluble forms, which suggests that soil sterilization may increase the availability of these heavy metals to plants.

Applicability of selective dissolution of manganese oxide by acidified 0.1M NH2OH–HCl in Japanese soils

“…Therefore, Mn oxides can play an important role in scavenging heavy metals in soils, holding metals on the surface and in the interlayer and its crystal lattice by isomorphic substitution (Miyata et al, 2007). Mn oxides can be mobilized with changes in environmental conditions, such as soil flooding (Patrick and Jugsujinda, 1992), soil drying (Makino et al, 2000), and soil sterilization (Suda et al, 2009). These findings suggest that trace elements that are bound onto or occluded into Mn oxides are released to the soil solution easily; therefore, Mn oxides potentially control the cycling of trace elements and their bioavailability in soils.…”

Speciation of soil trace elements in different fumigated soils#

“…The speciation and bioavailability of STEs depend on the interactions among soil pH, organic matters, microbes, and animals (Ge et al., 2000). Soil fumigation merely kills a large number of soil animals and some microorganisms for 7 days, but it cannot substantially change the physical and chemical properties of the soil (Ibekwe et al., 2001); consequently, pH was not responsible for the changing of Mn and Co. One reason for this phenomenon was that organic matter derived from dead microbial cells after fumigation played an important role in dissolving Mn oxides and increasing the content of Mn in F1 (Suda et al., 2009). In addition, the microorganism population involved in the Mn‐oxidizing process was inhibited with PIC, DMDS, and DZ fumigation due to the broad spectrum of fumigants for microbes.…”

“…For example, soil fumigation can significantly affect the mineralization of soil nitrogen, inhibit ammonia oxidation (Yan et al., 2013), and change the mineralization of sulfur and phosphorus elements due to soil microbes killed in the process after fumigation in the soil (Klose et al., 2006). Meanwhile, microorganisms have the ability to impact on bioavailability and mobility of soil trace elements (STEs; Suda et al., 2009). Thus, these fumigants may also affect the bioavailability and mobility of STEs due to inhibitory and biocidal effects of soil microorganisms after fumigation (Sessitsch et al., 2013; Weyens et al., 2009).…”

Activation effect of soil available nitrogen, manganese and cobalt after addition of different fumigants

“…Generally, it is very clear that fumigated soils have a readily and rapidly increase of available Mn and Co (figure 2). Previous studies have reported that some fumigation and sterilization methods increased the available Mn and Co, such as chloroform fumigation and gamma sterilization (Mcnamara et al (2003), Suda et al 2009). These reports showed that neutral monosaccharides and organic matter derived from dead microbial cells and cell lysis have dissolved Mn oxides and correspondingly increased the amounts of available forms of Mn and Co.…”