The Role of Low-Molecular-Weight Organic Carbons in Facilitating the Mobilization and Biotransformation of As(V)/Fe(III) from a Realgar Tailing Mine Soil

Role of MnO2 in controlling iron and arsenic mobilization from illuminated flooded arsenic-enriched soils

“…Microorganisms assimilate low-molecular-weight DOC (e.g., labile acetate) for their extracellular respiration and synchronously produce bio-electrons (Chen et al, 2018b;Liu et al, 2018). In general, the removal of LDOC and SDOC is a proxy for microbial consumption of DOC in our microcosms.…”

“…In soil microcosms, dissolved organic matter (DOM) plays several important roles in controlling metal mobility (Han et al, 2016). On the one hand, labile DOC fractions, like low-molecular-weight sugars, organic acids and amino acids, serve as important electron donors through microbial metabolism to supply bio-electrons which are subsequently transferred to high valence metals, promoting the reductive dissolution of metal from soil (Chen et al, 2018b). On the other hand, high-molecular-weight organic carbon compounds, such as humic and fulvic acid like-compounds, are considered as a capture agent for photoholes, suppressing the recombination of electron-hole pairs (Chen et al, 2019a).…”

Impacts of enhanced microbial-photoreductive and suppressed dark microbial reductive dissolution on the mobility of As and Fe in flooded tailing soils with zinc sulfide

“…After 45 days, almost 27.6%, 37.4%, 48.7%, and 59.10% of the LDOC was removed from the soils that were amended with acetate-ZnS (intermittent illumination), acetate alone (intermittent illumination), acetate-ZnS (dark), and acetate alone (dark), respectively. Loss of LDOC may be attributed to acetate used in the growth of soil microorganisms [32], microbially degraded for electron donation [6], or photodegraded by semiconducting minerals [33]. Considering the input-output electron balance in redox reactions, the behaviors for the conversion of organic substrates and electron transfer should be further studied.…”

“…Soils contain a wide array of organic substrates that play different roles in controlling electron transfer [5,25,32]. For instance, some lowmolecular-weight DOM (such as sugars and amino acids) can readily serve as electron donors for soil microorganisms [32], while some heavy-molecular-weight DOM (such as fulvic and humic acids) can serve as scavengers of photoholes [25]. Thus, we monitored the removal of SDOC to further confirm the potential input of mineral photoelectrons in flooded soils.…”

“…Hence, these electrochemical characteristics suggest that amendment with ZnS under illumination can boost photoelectron transfer, while the behavior of ZnS under dark conditions appeared to suppress electron transfer. As bio-electrons were supplied from microbial degradation of organic substrates [32,34], the composition of the microbial community should be further examined.…”