This study investigated the impacts of γ-radiation at a final dose of 25 kGy on the physicochemical properties of a range of wet iron oxyhydroxides (2-line ferrihydrite, lepidocrocite, and goethite) synthesized in the presence of varying concentrations of the polysaccharide Na-alginate (starting solutions containing C/Fe ratios of 0, 0.5, 1.0, and 1.5). The degree of impact to the minerals was examined by chemical extractions, and various analytical techniques including XRD, FTIR-ATR, Mössbauer spectroscopy, and N adsorption-desorption isotherms, as well as by assessing their bioavailability towards the model Fe(III) reducing bacteria CN32. Across all the coprecipitates studied, it was found that γ-irradiation led to a substantial dissolution of Fe and the concomitant release of Fe(II) and alginate into solution. Despite this observation, the bulk mineralogy and crystallinity of the studied iron oxyhydroxides, as determined by XRD and FTIR-ATR, did not appear to change. However, analyses via Mössbauer spectroscopy (77 and 5 K) revealed that the crystallinity of the 2-line ferrihydrites increased post-irradiation. Moreover, among the minerals studied, the specific surface area and porosity decreased for only the post-irradiated 2-line ferrihydrite coprecipitates with a C/Fe ratio of 0.5 or 1.0. The bioreduction rates of the studied minerals and their irradiated counterparts did not significantly differ, whereas the extent of bioreduction of post-irradiated 2-line ferrihydrite coprecipitates (C/Fe 0.5, 1.0, and 1.5) exhibited a significant increase of up to 28%. In contrast, the extent of Fe reduction for select post-irradiated lepidocrocite (C/Fe 0.5) and goethite (C/Fe 1.5) coprecipitates was slightly higher than determined for their corresponding native controls. The observed differences in bioavailability between the native and irradiated coprecipitates were attributed to irradiation induced alteration of particle aggregation and coagulation as determined by particle size analyses and visual observations. In summary, the findings suggest that even a low total dose of 25 kGy, γ-radiation can lead to significant physicochemical changes in coprecipitates with relatively low organic matter content. Therefore, future research designed to investigate organic matter-Fe composite systems in natural samples should be cognizant of the potential effects of sterilization through γ-irradiation. These effects could potentially result in inaccurate over- or under- estimations of the bioavailability of Fe or organic matter, as well as the possible adsorption capacity of organic matter-Fe coprecipitates for contaminants.

中文翻译：

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γ(γ)辐射对不同浓度海藻酸钠共沉淀羟基氧化铁理化性质和生物利用度的影响


本研究调查了 25 kGy 最终剂量的 γ 辐射对在不同浓度的多糖 Na-存在下合成的一系列湿羟基氧化铁（2 线水铁矿、纤铁矿和针铁矿）的物理化学性质的影响。海藻酸盐（起始溶液含有 0、0.5、1.0 和 1.5 的 C/Fe 比率）。通过化学提取和各种分析技术（包括 XRD、FTIR-ATR、穆斯堡尔光谱和 N 吸附-解吸等温线）以及评估其对 Fe(III) 还原细菌模型的生物利用度来检查对矿物质的影响程度CN32。在所有研究的共沉淀物中，发现 γ 辐射导致 Fe 大量溶解，并同时将 Fe(II) 和藻酸盐释放到溶液中。尽管有这一观察结果，通过 XRD 和 FTIR-ATR 测定，所研究的羟基氧化铁的整体矿物学和结晶度似乎没有变化。然而，通过穆斯堡尔光谱（77 和 5 K）的分析表明，2 线水铁矿的结晶度在辐照后增加。此外，在所研究的矿物中，只有C/Fe比为0.5或1.0的辐照后2系水铁矿共沉淀物的比表面积和孔隙率下降。研究矿物及其辐照对应物的生物还原率没有显着差异，而辐照后 2 系水铁矿共沉淀物（C/Fe 0.5、1.0 和 1.5）的生物还原程度显着增加，高达 28% 。相比之下，选定的辐照后纤铁矿 (C/Fe 0.5) 和针铁矿 (C/Fe 1.5) 共沉淀物的 Fe 还原程度略高于其相应的天然对照所测定的程度。 观察到的天然共沉淀物和辐照共沉淀物之间生物利用度的差异归因于通过粒度分析和目视观察确定的辐照诱导的颗粒聚集和凝结的改变。总之，研究结果表明，即使 25 kGy 的低总剂量，γ 辐射也会导致有机物含量相对较低的共沉淀物发生显着的物理化学变化。因此，未来旨在研究自然样品中有机物-铁复合系统的研究应该认识到γ-辐射灭菌的潜在影响。这些影响可能会导致对铁或有机物的生物利用度以及有机物-铁共沉淀物对污染物的可能吸附能力的不准确高估或低估。