Assessment of Pollution Sources and Contribution in Urban Dust Using Metal Concentrations and Multi-Isotope Ratios (13C, 207/206Pb) in a Complex Industrial Port Area, Korea

The metal concentrations and isotopic compositions (13C, 207/206Pb) of urban dust, topsoil, and PM10 samples were analyzed in a residential area near Donghae port, Korea, which is surrounded by various types of industrial factories and raw material stockpiled on empty land, to determine the contributions of the main pollution sources (i.e., Mn ore, Zn ore, cement, coal, coke, and topsoil). The metal concentrations of urban dust in the port and residential area were approximately 85~112 times higher (EF > 100) in comparison with the control area (EF < 2), especially the Mn and Zn ions, indicating they were mainly derived from anthropogenic source. These ions have been accumulating in urban dust for decades; furthermore, the concentration of PM10 is seven times higher than that of the control area, which means that contamination is even present. The isotopic (13C, 207/206Pb) values of the pollution sources were highly different, depending on the characteristics of each source: cement (−19.6‰, 0.8594‰), Zn ore (−24.3‰, 0.9175‰), coal (−23.6‰, 0.8369‰), coke (−27.0‰, 0.8739‰), Mn ore (−24.9‰, 0.9117‰), soil (−25.2‰, 0.7743‰). As a result of the evaluated contributions of pollution source on urban dust through the Iso-source and SIAR models using stable isotope ratios (13C, 207/206Pb), we found that the largest contribution of Mn (20.4%) and Zn (20.3%) ions are derived from industrial factories and ore stockpiles on empty land (Mn and Zn). It is suggested that there is a significant influence of dust scattered by wind from raw material stockpiles, which are stacked near ports or factories. Therefore, there is evidence to support the idea that port activities affect the air quality of residence areas in a city. Our results may indicate that metal concentrations and their stable isotope compositions can predict environmental changes and act as a powerful tool to trace the past and present pollution history in complex contexts associated with peri-urban regions.

A New Model for the Genesis of Carboniferous Mn Ores, Longtou Deposit, South China Block

The lower Carboniferous Luzhai and Baping Formations (ca. 359 Ma) of the South China block, Guangxi Province, comprise an ca. 170-m-thick clastic-carbonate succession capped by Mn ore horizons near the town of Longtou. Excellent exposure of the stratigraphic succession provides an unparalleled opportunity to investigate the origin of carbonate-hosted Mn deposits, which are generally understudied. Lithofacies associations suggest inner and middle shelf clastic rocks accumulated with deposition of carbonates on a mesotrophic middle to outer shelf. In the Longtou region, carbonate deposition during marine transgression culminated with the precipitation of high-grade Mn deposits during maximum flooding. Mn ore horizons are composed of amalgamated alabandite-bearing rhodochrosite, Mn calcite, and braunite laminae. Mn carbonates have been largely interpreted as forming in oxic water columns via reduction of Mn oxides by organic matter. However, paragenetic relationships and δ13C values (similar to those of seawater) indicate the Mn carbonates of Longtou were formed during authigenesis by the emplacement of anoxic, Mn-rich water masses on the distal to middle shelf. Such anoxia is interpreted to have shut down the carbonate factory and diminished sedimentation, a prerequisite for the concentration and precipitation of Mn carbonates in pore water. This research supports the notion that areas of the Paleozoic deep ocean were persistently anoxic and periodically tapped by coastal upwelling to produce Mn- and Fe-rich deposits. Application of this emerging ore deposit model to other economically important carbonate-hosted Mn deposits may improve resource exploration.

Earthquake-induced clastic dyke and fluid inflow at the Miguel Burnier manganese-ore deposit, Quadrilátero Ferrífero of Minas Gerais, Brazil

A clastic dyke has been recognised within manganese (Mn)-rich Cenozoic sediments near a historical Mn-ore deposit in the Miguel Burnier district, Quadrilátero Ferrífero, in the southern São Francisco craton, Brazil. Here, we describe the clastic dyke, a subvertical fissure that is filled with friable arenaceous fragments, and characterise it as seismite. An overprint by stockwork-like Mn-oxide veinlets and Mn-oxide dissemination, mineralogically expressed as birnessite, lithiophorite and jianshuiite, and geochemically represented by metalliferous enrichments, particularly mercury (Hg), occurs in the clastic dyke and its immediate vicinity. Such an overprint also contains illite, which forms a mineral association with birnessite, lithiophorite and jianshuiite, and constrains the temperature of hydrothermal alteration to less than 300 °C. The recognition of seismite and its Hg enrichment indicate that the Cenozoic history of the Quadrilátero Ferrífero cratonic terrane has been affected by seismic episodes, which were not only conducive to local enrichment in Mn at Miguel Burnier, but also to recent seismic-related phenomena such as a dam failure (Agurto-Detzel et al. in GRL 43: 4929–4936, 2016).

Manganese Ore-based Wet Flue-Gas Desulfurization: A Review

The removal of SO2 from flue gases is necessary for eliminating haze and controlling acid rain. However, developing the traditional wet and dry flue-gas desulfurization (FGD) is challenging due to the disposal issue of several byproducts. Manganese (Mn) orebased wet FGD possesses many advantages, including good desulfurization property, low cost, and high economic benefit. The environment friendliness and reusability of MnSO4 provide new ideas and methods in the future research direction of FGD. This review summarizes the background information of Mn ore slurry desulfurization, the desulfurization mechanism, the technological process, and the desulfurization devices. The role of operating parameters, such as temperature, liquid/solid ratio, pH, SO2 concentration, and particle size, in the desulfurization efficiency and manganese leaching rate are also discussed. The temperature (20°C-80°C) has exerted little effect on the desulfurization efficiency, whereas a low pH value is beneficial for SO2 removal. Moreover, a low inlet SO2 concentration and small particle size are beneficial for SO2 removal. The control and digestion techniques related to the byproduct (manganese dithionate) are also presented, along with the future development direction of Mn ore-based wet FGD in different industries.