Long-term experience in anoxic wastewater treatment plants of planar MFC with Ce-doped cathodes

Planar MFC prototypes were constructed and experimented to operate as sensors of the anoxic condition in a denitrification tank of a wastewater treatment plant in Italy, during different times in 2018 – 2019. Electrodes were differently enriched with carbon paint containing nanotubes and CeO2 nanoparticles. Performances of different electrodes were compared. Results underline critical anoxic conditions in the tank, that caused a very low signal and phenomena of signal reversion during some period of the year. the activity of aerobic microorganisms and protozoa growing and grazing the bacteria on the electrodes strongly influenced the signal of the MFCs. The presence of nanoceria enhanced, for some extent, the MFC signal, both in presence of reversing trends and in absence of these phenomena. In absence of reversing trends, nanoceria enhanced the MFC voltage. Such signal trends from MFCs can give, in real-time, useful information to optimize the purification process without the necessity of frequent biological and chemical analyses.

Hydrocarbon source rocks in Kazhdumi and Pabdeh formations—a quick outlook in Gachsaran oilfield, SW Iran

Geochemical study of Kazhdumi and Pabdeh Formations as potential source rocks in Gachsaran Oilfield demonstrates that the Kazhdumi Formation has a fair to good capability of hydrocarbon generation and predominately contains type II-III kerogen. On the other hand, the Pabdeh Formation has a poor to good petroleum potential and contains different kerogen types, including type II, type II-III, type III and even for one sample, type IV, indicating different depositional conditions for this formation. The geochemical log of the Kazhdumi Formation shows that there is a close correlation between different geological parameters as noticed prominently in well number 55, which suggests the more extensive the anoxic condition, the higher the petroleum potential is for Kazhdumi Formation. By contrast, a poor correlation between TOC and other Rock–Eval-derived parameters for the Pabdeh Formation at a depth of more than 2100 m may demonstrate the inert organic matter and mineral matrix effects at this depth interval. However, biomarkers show differences in lithology and depositional environment for the Kazhdumi Formation in well numbers 55 and 83. On the other hand, the Pabdeh Formation has a mixed lithology (carbonate-shale) deposited in a marine setting under suboxic–anoxic condition. Moreover, thermal maturity indicators suggest that Pabdeh and Kazhdumi Formations are immature and early mature, respectively.

Effect of Hydrocarbon Haze on Marine Primary Production in the Early Earth System

<p>During the Archean (4.0–2.5 Ga), atmospheric oxygen levels would have been much lower than the present value (pO<sub>2</sub> < ~10<sup>–5</sup> PAL) [1], and the majority of the primary production would have been carried by anoxygenic photosynthetic bacteria. In a sufficiently reducing atmosphere (CH4/CO2 > ~0.2) [2], the layer of hydrocarbon haze could be formed in the upper atmosphere, possibly affecting the climate. Because haze particles significantly absorb the solar UV flux, the formation of hydrocarbon haze could affect the marine microbial ecosystem via the change in the production rate of electron donors (H<sub>2</sub> and CO). However, how the formation of hydrocarbon haze affects the global activity of the marine microbial ecosystem remains unclear. Here, we employ a novel carbon cycle model in which a one-dimensional photochemical model “Atmos” [2], a marine microbial ecosystem model, and the carbonate-silicate geochemical cycle model are coupled. We assessed the effect of the formation of hydrocarbon haze on marine microbial ecosystems assuming completely anoxic conditions (pO<sub>2</sub> < ~10<sup>–10</sup> PAL) in the middle Archean and assuming mildly oxidized conditions (pO<sub>2</sub> > 10<sup>–10</sup> PAL) in the late Archean.</p><p>We found that, under the completely anoxic condition, haze formation works as a negative feedback for the oceanic biological activity. This is because the formation rate of electron donors (H<sub>2</sub> and CO) in the atmosphere decreases with the progress of haze formation, so that the changes in the biogenic methane flux and the haze formation rate are suppressed. More specifically, the decrease in the formation rate of electron donors is caused by the decrease in the photo-dissociation rate of CO<sub>2</sub> because of UV-shielding due to haze particles, and also by removal of C- and H-atom, which are supposed to be converted to CO and H<sub>2</sub> if the haze is not formed, due to rainout of haze particles. </p><p>We also found that, under the mildly oxidized condition, there are multiple equilibrium climate states that have a different haze thickness. The solution with thicker haze layer is similar to the completely anoxic condition, however, the other solution with the thinner haze layer is unique to the mildly oxidized condition. In this new equilibrium state, the formation rate of electron donors further decreases with the progress of haze formation because of the decrease in the photo-dissociation rate of formaldehyde. Thus, this mechanism works as a strong negative feedback for ocean biological activity and haze thickness, keeping the haze thickness thinner than the completely anoxic condition. We show that, as a result of this negative feedback, climate with the thinner haze could be stably achieved under the mildly oxidized condition. This result is consistent with a geological record which suggests possible transient formation of the haze in the Late Archean [3]. We suggest that haze formation is a vital process in understanding the biological activity and climate stability on terrestrial Earth-like planets.</p><p>[1] Lyons et al. (2014). Nature 506, 307-315. [2] Arney et al. (2016). Astrobiology 16(11), 873-899. [3] Izon et al. (2017). PNAS 114(13), E2571-E2579.</p>

Facile and rapid synthesis of crystalline quadruply bonded Cr(ii) acetate coordinated with axial ligands

Facile ligation of quadruply bonded Cr(ii) acetates at the axial position under the anoxic condition and their rapid crystallization into single crystals with sub-millimeter scale.