Stability of organic matter-iron-phosphate associations during abiotic reduction of iron

ShuaiLong Wen; YueHan Lu; JiaRu Dai; XiuLin Huang; ShiLin An; JingJing Liu; ZhengWen Liu; YingXun Du; YunLin Zhang

doi:10.1016/j.jhazmat.2023.131016

Stability of organic matter-iron-phosphate associations during abiotic reduction of iron

J Hazard Mater. 2023 May 5:449:131016. doi: 10.1016/j.jhazmat.2023.131016. Epub 2023 Feb 15.

Authors

ShuaiLong Wen¹, YueHan Lu², JiaRu Dai³, XiuLin Huang⁴, ShiLin An¹, JingJing Liu¹, ZhengWen Liu¹, YingXun Du⁵, YunLin Zhang¹

Affiliations

¹ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Molecular Eco-Geochemistry (MEG) Laboratory, Department of Geological Sciences, The University of Alabama, 201 7th Ave, Tuscaloosa, AL 35485, USA.
³ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 210008, China.
⁴ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; School of Environmental and Chemical Engineering, Chongqing Three Gorges University, Chongqing 404020, China.
⁵ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: yxdu@niglas.ac.cn.

PMID: 36821894
DOI: 10.1016/j.jhazmat.2023.131016

Abstract

The stability of organic matter-iron-phosphate (OM-Fe-P) association has an important impact on the migration and sequestration of organic carbon (OC) and P in the environment. Here, we examined the release characteristics of Fe, P and OM due to the abiotic reduction of OM-Fe-P associations by Na-dithionite. The associations were synthesized with algae-derived OM (AOM) and terrestrial humic acid (HA) through either adsorption onto iron (hydr)oxide or coprecipitation with Fe(III). Results indicated that OM and P adsorbed onto the associations were rapidly released, whereas coprecipitation yielded much lower release rates of Fe, P, and OM. The stronger inhibitory effect on reduction from coprecipitation can be explained by larger particles formed by coprecipitation and coprecipitation taking up more OC that had a passivation effect on the associations. The release rates of OM and P were lower in coprecipitates formed with HA than formed with AOM for a given OC/Fe ratio. This observation can be attributed to a patchy distribution of OC in AOM associated coprecipitates, which showed a weaker aggregation of OC with Fe and P. In contrast, the distribution of OC in HA-associated coprecipitates was more homogenous, enabling a stronger aggregation of OM with P and a greater passivation effect on P release. Our results revealed that OM sources, association formation pathways, and elemental stoichiometry collectively controlled the stability of OM-Fe-P associations.

Keywords: Adsorption; Coprecipitation; FESEM-EDS; Mössbauer spectrum; Organic matter source.