Heavy metals soils, sediment, extractable

Singh, S.R, Tack, F.M. and Verloo, M.G. (1998) Heavy metal fractionation and extract-ability in dredged sediment derived soils. Water Air Soil Poll., 102, 313-328. 

The behavior of elements (toxicity, bioavailability, and distribution) in the environment depends strongly on their chemical forms and type of binding and cannot be reliably predicted on the basis of the total concentration. In order to assess the mobility and reactivity of heavy metal (HM) species in solid samples (soils and sediments), batch sequential extraction procedures are used. HM are fractionated into operationally defined forms under the action of selective leaching reagents. 

DeCaF treats soil, sludges, solids (e.g., slag), residues, and sediments contaminated with radioactive elements and other hazardous constituents. The technology has potential applications in the treatment of heavy metals. The technology can treat uranium-contaminated calcium fluoride matrices, rare-earth ore residues, and fluorspar contaminated with uranium. The technology can also extract more complex fluoride by-products. 

The acid extraction treatment system (AETS) reduces the concentrations and/or leachability of heavy metals in contaminated soils so that the soils can be returned to the original site. The main application of the AETS is to extract heavy metals from soils. Additional applications of the AETS include treatment of contaminated sediments, sludges, and other heavy-metal-containing solids. 

SOLFIX is an ex situ stabilization technology that treats heavy metals by reacting contaminated soils and sediments with cement, pozzolanic materials, and other additives to chemically immobilize contaminants into an insoluble form. SOLFIX can be used either as a stand-alone technology or it can be incorporated with Hydro-SEP (a sediment washing technology) and ORG-X (a solvent extraction technology) into a three-step remediation process termed integrated sediment decontamination system (ISDS). 

Much work has been reported on the evaluation of sequential extraction procedures. The three-stage sequential extraction procedure for speciation of heavy metals proposed by the Commission of the European Communities Bureau of References (BCR) was found to be acceptable and reproducible with some modifications [29]. In another study, when applied to real soils and sediments, this (unmodified) BCR method was queried [30]. Lopez-Sanchez et al. [31 ] found that significant results can be obtained when different sequential extraction procedures are used. 

Ure, A.M., Quevauviller, Ph., Muntau, H. and Griepink, B. (1993a) Speciation of heavy metals in soils and sediments. An account of the improvement and harmonisation of extraction techniques under the auspices of the BCR of the Commission of the European Communities. Int.J. Environ. Anal. Chem., 51, 135-151. 

The impact of heavy metals from highways on adjacent soils and receiving waters has also been investigated by sequential extraction (Stone and Marsalek, 1996). Airborne dust, at least partly derived from motorways, was found to be a significant source of soil contamination in two satellite cities of Seoul, South Korea (Chon et al., 1998). A comparison between roadside soil and sediment from... 

Sequential extraction is now a well-established tool in soil and sediment analysis. Although the approach is unlikely to provide precise information on the mineral phases to which trace metals are bound, it does provide useful information on potential mobilities of heavy metal contaminants which is not available from (pseudo)total metal determination. The adoption of standard protocols, such as that recommended by BCR, means that reliable and comparable data can be obtained by different laboratories. 

Rauret, G. (1998). Extraction procedure for the determination of heavy metals in contaminated soil land sediment. Talanta 46, 449-455. 

These complications provide an explanation for the lack of agreement obtained from many studies which have been carried out to assess the effect of pH on heavy metal availability, as well as the relative effectiveness of various reagents for the extraction of these metals from clays, soils, and sediments. The extractability or leachability of these metals should be viewed in terms of the Eh and pH of the system, soil plus extractant, as compared with that of the system soil plus pore water, and the solubilities of Fe(OH)3(a) and Mn02(a ), especially the latter, in the extractant utilized, [(a) indicates an x-ray amorphous solid as opposed to (c), a crystalline phase.]... 

Specifically sorbed carbonate-bound. Significant concentrations of trace elements can be associated with sediment carbonates. A mixture of M NaOAc with HOAc at pH 5 has been shown to extract > 99% of total carbonate present in the soils (Jackson, 1958). This method was used as a specific extractant for the determination of carbonate-bound heavy metals in soils (Tessier et al, 1979 Foerstner et al., 1981 Harrison et al, 1981 Robbins et al, 1984 Hickey and Kittrick, 1984 Krishnamurti et al., 1995a Krishnamurti and Naidu, 2000). Other reagents that were also used include 2.5% HOAc (MacLaren and Crawford, 1973 Gupta and Chen, 1975 Garcia-Mirgaya et al, 1981) and 0.05 M Na2-EDTA (Sposito et al, 1982). 

In the case of Mn (Fig. 2) it is evident that Mn is dominantly present in its most mobile phases (172.98 pg mL , i.e. 33% after the first, and 251.46 pg mL, i.e. 47% of the totally extracted Mn after the second phase). The abundance of extracted Mn after the second phase indicates that Mn is in the form of hydroxides, and in this form, it represents one of the main substrates for heavy metals. Also, it is evident that some quantity of Mn (172.98 pg mL" ) was extracted after the first phase. This result indicates that hydroxides and oxides of Mn were notably extracted in the first extraction step of the sequential extraction with ammonium-acetate [81, 86]. On the basis of these results decreasing of pH and increasing of ionic strength values will raise the mobility of heavy metals by dissolution of Mn-hydroxides in soils and sediments. 

Kheboian C, Bauer CF (1987) Accuracy of selective extraction procedures for metal speciation in model aquatic sediments. Anal Chem, 59 1417-1423 Legret M (1993) Speciation of heavy metals in sewage sludge and sludge-amended soil. Int J Environ Anal Chem, 51 161-165... 

Rauret G (ed)(1993) Workshop on sequential extraction in sediments and soils. Selected papers. Intern J Environ Anal Chem., (special issue), 51 Roszyk E, Szerszeh L (1988a) Accumulation of heavy metals in the arable layer of soils of the sanitary protection zone in the vicinity of copper metallurgic plants. Part 1 Legnica. Rocz Glebozn 39,4 135-141... 

Hass, A., and P. Fine. 2010. Sequential selective extraction procedures for the study of heavy metals in soils, sediments, and waste materials—K critical review. Critical Reviews in Environmental Science and Technology 40, no. 5 365-399. doi 10.1080/10643380802377992. 

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