The Efficiency of Using Na EDTA and DTPA to Extract Different Fractions of Soil Strontium

Abstract

TRONTIUM takes the same uptake and distribution pathways of Ca within plants; hence disturbs many secondary metabolites. In humans, it can replace Ca in bones and teeth, making them brittle. Thus, remediating Sr-polluted soils has become an obligation to attain a hazard-free environment. In this context, Sr is one of the potentially toxic elements that have received little attention. Thus, the current study aims at investigating the efficiency of using different chelating agents i.e. Na EDTA and DTPA for the chemical extraction of Sr from contaminated soils. To attain this aim, three soil types i.e. a clay loam one and two sandy loam soils varying in their CaCO 3 content were artificially polluted with Sr at three levels (50, 100 and 200 mg Sr kg -1 ); then left to equilibrate for 3 months. Thereafter, Sr was determined within the different soil fractions. In the clayey soil, most Sr was bounded with sesquioxide; followed by the exchangeable fraction, while in the other two soils (sandy loam ones), most of soil-Sr dominated within the exchangeable form, followed by the carbonate bound fraction. The contaminated soils were then subjected to soil leaching via either Na EDTA or DTPA and the extractable amount by both methods were comparable, with slight superiority for DTPA. Generally, the extraction efficiencies of Sr by these chelating agents were low in the sandy loam soils which contained 50 mg Sr kg -1 while increased considerably with increasing the level of soil contamination recording approximately 76-88%. Afterward, fractionation of Sr was accomplished again where the carbonate and organic bound fractions were the dominant ones; yet the exchangeable fraction still represents a substantial percentage. Generally, all fractions prior to soil leaching were correlated with each other. T he two chelating agents were capable of extracting Sr among the different soil fractions except for the sesquioxide bound which was not extractable by Na-EDTA (r 2 =0.371) yet it can be extracted by DTPA (r 2 =0.413). This result provides more evidence for the feasibility of using both EDTA-2Na and DTPA in the chemical extraction of Sr from contaminated soils.