Hacherl E L, Kosson D S, Young L Y, Cowan R M
Department of Civil and Environmental Engineering, Vanderbilt University, Nashvillie, Tennessee 37235, USA.
Environ Sci Technol. 2001 Dec 15;35(24):4886-93. doi: 10.1021/es010830s.
The quinol form (AHDS) of 9,10-anthraquinone-2,6-disulfonate (AQDS) was used as a titrant to determine bioavailability of Fe(III) in pure iron minerals and several soils. AHDS oxidation to AQDS was coupled to Fe(III) reduction to Fe(ll) in biological media consisting of trace salts and vitamins, providing estimates of bioavailability consistentwith the biogeochemical mechanisms and conditions that control Fe(III) availability to iron-reducing bacteria. Iron(III) oxide sources were synthetic oxides (amorphous and crystalline) and three soils separated into two size fractions each (0-500 and 500-1000 microm). This titration gave a measurement of the amount of Fe(III) available to dissimilatory iron-reducing bacteria and was compared to hydroxylamine reduction, oxalate extraction, and biological reduction by Shewanella alga BrY. The advantage of AHDS titration over existing chemical techniques is that it can be performed at normal soil pH and ionic strength, and it allows for distinction of iron(III) oxides rendered unavailable by sorption of Fe(II) or by other pH-dependent geochemical processes. This approach also allows distinction of Fe(III) present in micropores that is not directly available to bacteria but bioavailable in the presence of an electron shuttle capable of transporting electrons into the micropores.
9,10-蒽醌-2,6-二磺酸盐（AQDS）的醌型（AHDS）被用作滴定剂，以测定纯铁矿物和几种土壤中Fe(III)的生物有效性。在由痕量盐和维生素组成的生物介质中，AHDS氧化为AQDS与Fe(III)还原为Fe(II)相耦合，提供了与控制铁还原细菌可利用Fe(III)的生物地球化学机制和条件一致的生物有效性估计值。氧化铁来源为合成氧化物（无定形和结晶）以及三种土壤，每种土壤又分为两个粒径级分（0 - 500和500 - 1000微米）。这种滴定法测量了异化铁还原细菌可利用的Fe(III)量，并与羟胺还原法、草酸盐萃取法以及希瓦氏菌BrY的生物还原法进行了比较。AHDS滴定法相对于现有化学技术的优势在于，它可以在正常土壤pH值和离子强度下进行，并且能够区分因Fe(II)吸附或其他pH依赖的地球化学过程而变得不可利用的氧化铁。这种方法还能够区分存在于微孔中、细菌无法直接利用但在存在能够将电子传输到微孔中的电子穿梭体时具有生物可利用性的Fe(III)。
