| Dissolved organic matter (DOM) represents one of the most mobile and reactive organic matter fractions, thereby controlling a number of physical, chemical and biological processes in both terrestrial and aquatic environments. The organic acids present in the DOM can act as a chelating agent, enhancing the mobilisation of toxic heavy metals. For this reason, DOM influences the binding and speciation of metals in the environment and their mobility, toxicity and bioavailability. Unfortunately, only approximately 25% of DOM has been characterized so far, which has greatly limited our understanding of it. Therefore, the study on the characteristics of DOM is necessary. Recently, the research has been shown that DOM has redox properties, which have been mainly attributed to quinones, which can both accept or donate electrons. The electron transfer role of DOM may potentially promote microbial dissimilatory Fe(III) reduction in environment. Dissimilatory Fe(III) reduction is the process in which microorganisms transfer electrons to external Fe(III) oxide as an electron acceptor, reducing it to Fe(II), and microorganisms may absorb energy to support growth or not. Dissimilatory Fe(III) reduction has a major influence not only on the distribution of iron, but also on the fate of a variety of other trace metals and nutrients, and it plays an important role in degradation of organic matter. So there's an important environmental significance to examine the effects of DOM on microbial dissimilatory Fe(III) reduction. In this paper, the related nature of DOM of their own were examined with UV-Vis spectroscopy, cyclic voltammetry (CV) , Fourier transform infra-red spectroscopy (FT-IR). The electron transfer capability (ETC) of DOM derived from different sources were studied with Shewanella putrefaciens 200, Shewanella cinica D14Tand Aeromonas hydrophila HS01 as driving force of electron transfer. DOM's electron shuttling characteristics and its effects on microbial dissimilatory Fe(III) reduction were explored. The main conclusions of this study are as follows:1. UV-visible spectra showed that the features of absorption peak of sludge-DOM, compost-DOM and humic acid (HA) are similar in general. This suggested that the sludge-DOM and compost-DOM include some HA, which is an important component of DOM. Through CV scanning of DOM in the aqueous phase, organic phase and mixed water and organic phase, the results show that the AQDS, HA, sludge-DOM and sludge-DOM have oxidation-reduction properties. There were a lot of similarities in the FT-IR characteristic of four DOMs derived from the sludge, compost, topsoil and deep soil, which suggested they contain the same functional groups. The differences of absorption peak intensity among them indicated that the content of their functional groups was dissimilarity.2. Under different concentrations of electron donor with FeCl3 and Fe (citrate) as the electron acceptor, the electron donoring capacity (EDC) was determined with S. putrefaciens 200, S. cinica D14Tand A. hydrophila HS01 as driving force of electron transfer. The results indicated EDCs with FeCl3 as the electron acceptor were SP200< D14< HS01 and EDCs with Fe (citrate) as the electron acceptor were SP200≈D14 |
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