The Effect And Modification Of Surface Properties Mineral Granules Mediated By Three Common Bacteria And Extracellular Polymeric Substances(EPS)

With the rapid development of economy and urbanization accelerated, inhalable particulate matter pollution is becoming an increasingly serious issue, serious impact on human health. The main component of atmospheric particulates included fine mineral particles and microorganisms. At present, the research about toxicity and surface properties on microorganisms living cells to fine mineral particles was still very limited. Extracellular polymeric substances(EPS) played an important role in the process of microorganisms to fine mineral particles. Therefore, research on bacterial EPS to atmospheric fine mineral particles was very necessary.In this paper, calcite, Nano-CaCO3, quartz, Nano-SiO2 and albite, the typical fine mineral particles in the atmosphere, were used as the research object. Permanent soil bacteria(i.e. Bacillus mucitaginosus), air common pathogenic bacteria(i.e. Staphylococcus aureus) and the human body’s normal bacteria(i.e. Escherichia coli) were used as the experimental strains. In order to analyze the process between the fine mineral particles, from in soil- air- human body, and different common bacteria. The bacterial EPS main component including low molecular weight organic acids, amimo acids and monosaccharide components in polysaccharides obtained were determined by high performance liquid chromatography(HPLC). Inductively coupled plasma(ICP), Xray fluorescence(XRF), X- ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), Scanning electron microscope(SEM) and Zeta potential were used to characterize the soluble ions, surface charge, surface groups and surface morphology of residual solid. The results are list as follows:(1) The main components of three common bacterial EPS showed that low molecular weight organic acids consisted of oxalic acid, lactic acid, citric acid and succinic acid; amino acids consisted of histidine, arginine, tyrosine and cysteine; monosaccharide components in polysaccharides consisted of mannose, ribose and glucuronic acid.(2) Three bacterial EPS could significantly change the surface properties(the soluble ions, surface charge, surface groups and surface morphology) of the five minerals, and the impact on carbonate minerals was greater than aluminosilicate minerals was greater than silicate minerals. That was the degree of changed of surface properties of several minerals: calcite > albite > quartz, Nano-CaCO3> Nano-SiO2.(3) It was significantly different for three bacterial EPS to micron-mineral and nano-mineral. With the nano-mineral surface high chemical activity and adsorption capacity, made it more easily to react with organic substance. The results of soluble ions showed, the soluble ions caused by organic acids, amino acids and monosaccharides for nano-mineral significantly higher than for micron-mineral. The results of FTIR showed, nano-mineral surface could adsorb more organic substance or their groups, and its adsorption capacity was significantly higher than micron-mineral. However, nano-mineral had high surface energy, made the effect on its surface electrical properties was lower than micron-mineral in organic acids, amino acids and monosaccharides. The impact of bacterial EPS on the surface properties of mineral particles significantly was greater than the EPS main components. When nano-mineral in the role of bacteria or their EPS, the characteristic of nano-mineral surface was broken. The results of Zeta potential showed, bacteria and their EPS could significantly make the Zeta potential of nano-mineral shifted to the negative charge.(4) Surface properties of fine mineral particles in the role of bacterial EPS, the imfluence degree successively was cells were greater than bacterial EPS was greater than EPS free cells. The results of SEM showed, in the process of bacteria influence on mineral surface morphology, EPS layer was the main major contributor.In summary, the three bacterial EPS could affect the surface properties of five minerals. Different bacterial EPS had different effects on the same mineral, the same bacterial EPS had different effect on the different minerals, and the same bacterial EPS had significantly different effect on micron-mineral and nano-mineral, this was closely related to the component of bacterial EPS and the characteristics of mineral surface. These results suggested that the surface properties of fine mineral particles occurred constantly changed throughout the migration process, especially the soluble toxic Si ions, so as to make the fine mineral particles modified. When the fine mineral particles migrated to human body, the hurt weakened. It is important for the establishment of the inhaled fine particles of mineral environmental and health impact assessment system.