Redistribution of Ag in Two Calcareous and Noncalcareous Spiked Soils

Abstract

Abstract<br><br>Review of literature clearly shows that environmental data are scarce on the behavior of silver (Ag) in soils. Ag toxicity and its fate in the environment are currently being debated and are important as challenging research topics. Even though there are several studies on its total content in soils, fractionation of Ag, especially in calcareous soils has not been investigated. Therefore, we utilized an eight-step chemical extraction procedure to determine the chemical fractions of Ag (i.e., EXCH, CARB, Me-Org, re-MeOx, H2O2-Org, am-MeOx, cr-FeOx, and RES) following 30 and 60 days incubation in a calcareous and noncalcareous soil amended with Ag (0 and 15 mg kg-1). Experimental results showed that Ag in nonamended soils was predominantly in the forms H2O2-Org &gt; Me-Org &gt; RES &gt; CARB. These four fractions contributed more than 5% of total Ag concentration in noncalcareous soil. Redistribution of Ag in spiked noncalcareous soil was EXCH (34%), H2O2-Org (33%) and RES (17%). After 30 days incubation in contaminated noncalcareous soil, EXCH-Ag increased whereas CARB- and H2O2-Org-Ag decreased. However EXCH-Ag decreased and H2O2-Org-Ag increased after 60 days incubation (P &lt; 0.05). In calcareous soil after 30 days, EXCH- and RES-Ag increased but at the end of 60 days H2O2-Org-Ag increased. From our data we may conclude that addition of Ag results in increase of Ag mobility in soils but incubation may have adverse effect on its mobility. In general, chemical behavior of Ag, in terms of its redistribution into labile fractions in calcareous soil differed from noncalcareous soil.