Release and Biomethylation of Antimony in Shooting Range Soils upon Flooding

Abstract

Antimony (Sb) is an understudied pollutant with potentially toxic effects at particularly low concentrations. The fate of Sb in the environment is complicated because of its many chemical forms at varying oxidation states. Here, we validated an extraction method and an analytical technique to quantify inorganic and methylated Sb in bulk soil and soil solution. We identified and quantified trimethylantimony (TMSb) in shooting range soils for the first time, up to a concentration of 1.35 mg kg −1 . Then, we evaluated the release of Sb species from soil to soil solution as well as the influence of manure addition upon flooding in an incubation experiment with fresh soils from shooting ranges. This incubation experiment showed an immediate and exhaustive Sb release into the soil solution (within 6 h), reaching over 3000 µg L −1 for one site, followed by a sharp decline and again a slow increase at the end of the incubation in Sb concentrations in the soil solution for two of the three sites. TMSb was also formed in the soil solution after 4 to 10 days. High dissolved organic carbon (DOC) concentrations and the dissolution of Fe-and Mn-(oxy-)hydroxides were the main drivers of Sb release, while the addition of organic matter (OM) drove TMSb formation.

Capacity of Nerium oleander to Phytoremediate Sb-Contaminated Soils Assisted by Organic Acids and Oxygen Nanobubbles

“…Sb has been reported to exceed the value of 5000 mg/kg when background concentration in the natural environment is only 0.2 mg/kg, and the maximum permissible concentration according to the World Health Organization (WHO) is set at 36 mg/kg [ 3 , 10 , 11 ]. The predominant species are Sb(V) under oxic conditions and Sb(III) under reducing conditions [ 12 ]. In active Sb mining areas, a high Sb fraction is bioavailable, comprised primarily of Sb(V) [ 13 ].…”

Antimony Release and Volatilization from Organic-Rich and Iron-Rich Submerged Soils

“…Restricted oxygen diffusion in soils and sediments induced by waterlogging and fluctuating water tables influence metal(loid) mobility by shifting microbial communities to alternative electron acceptors for energy, such as Mn IV and Fe III -(oxyhydr)oxides coupled to the oxidation of organic C [16,22,23,[26][27][28]. Sb typically forms inner-sphere complexes with Fe III -and Mn IV -(oxyhydr)oxides in soils and sediments, and periodic or permanent waterlogging can induce Sb release by reductive dissolution of the host phases [26,27,29,30].…”

“…Restricted oxygen diffusion in soils and sediments induced by waterlogging and fluctuating water tables influence metal(loid) mobility by shifting microbial communities to alternative electron acceptors for energy, such as Mn IV and Fe III -(oxyhydr)oxides coupled to the oxidation of organic C [16,22,23,[26][27][28]. Sb typically forms inner-sphere complexes with Fe III -and Mn IV -(oxyhydr)oxides in soils and sediments, and periodic or permanent waterlogging can induce Sb release by reductive dissolution of the host phases [26,27,29,30]. Soluble Sb can be subsequently sequestered with waterlogging due to stronger adsorption of Sb III to Fe-phases in the soil [23,29], immobilized by sulfides [3,31,32], or Fe II catalyzed Fe III -phase transformations at neutral conditions, which incorporate Sb V into authigenic Fe III -phases (e.g., goethite and feroxyhyte) [33][34][35].…”

“…For example, Sb complexation with thiol-binding sites in sulfide-reacted peat sorbed up to 98% of Sb III , compared to 85% in untreated peat at pH 6 [38]. Dissolved organic matter (DOM) may also enhance Sb mobility by competing for binding sites on Fe III -and Mn IV -(oxyhydr)oxides [26,47,48] or by forming soluble complexes with low molecular weight organic acids [37,44,45]. Many gaps still exist in our understanding of the different influences on Sb mobility in high organic matter containing soils.…”

Uptake and Transformation of Methylated and Inorganic Antimony in Plants

“…Frohne et al ( 2011 ) suggested that low redox potential promotes the mobility of methylated Sb, based on the observation that the concentrations of mono- and di-methylated Sb decreased linearly with increasing redox potential in a soil suspension. Grob ( 2016 ) detected TMSb in the pore water of shooting range soils after 4 days of waterlogging, and Yang and He ( 2016 ) found higher concentration of methylated Sb in paddy soils than in dryland soils. Furthermore, the volatile compound trimethylstibine was found in sewage sludge sampled from anaerobic wastewater (Michalke et al, 2000 ).…”