Fluctuating climate is a hallmark of Earth. As one transcends deep into Earth time, however, both the evidence for and the causes of climate change become difficult to establish. We report geochemical and sedimentological evidence for repeated, short-term climate fluctuations from the exceptionally well-preserved ∼1.4-billion-year-old Xiamaling Formation of the North China Craton. We observe two patterns of climate fluctuations: On long time scales, over what amounts to tens of millions of years, sediments of the Xiamaling Formation record changes in geochemistry consistent with long-term changes in the location of the Xiamaling relative to the position of the Intertropical Convergence Zone. On shorter time scales, and within a precisely calibrated stratigraphic framework, cyclicity in sediment geochemical dynamics is consistent with orbital control. In particular, sediment geochemical fluctuations reflect what appear to be orbitally forced changes in wind patterns and ocean circulation as they influenced rates of organic carbon flux, trace metal accumulation, and the source of detrital particles to the sediment.

Photoelectrocatalytic (PEC) degradation of organic pollutants into CO2 and H2O is a promising strategy for addressing ever-growing environmental problems. Titanium dioxide (TiO2) has been widely studied because of its good performance and environmental benignancy; however, the PEC activity of TiO2 catalyst is substantially limited due to its fast electron–hole recombination. Herein, we report a TiO2 nanocone-based photoelectrocatalyst with superior degradation performance and outstanding durability. The unique conical catalyst can boost the PEC degradation of 4-chlorophenol (4-CP) with 99% degradation efficiency and higher than 55% mineralization efficiency at a concentration of 20 ppm. The normalized apparent rate constant of a nanocone catalyst is 5.05 h–1 g–1 m2, which is 3 times that of a nanorod catalyst and 6 times that of an aggregated particle catalyst, respectively. Further characterizations reveal that the conical morphology of TiO2 can make photogenerated charges separate and transfer more efficiently, resulting in outstanding PEC activity. Moreover, computational fluid dynamics simulations indicate that a three-dimensional conical structure is beneficial for mass transfer. This work highlights that tuning the morphology of a photoelectrocatalyst at the nanometer scale not only promotes the charge transfer but also facilitates the mass transportation, which jointly enhance the PEC performance in the degradation of persistent pollutants.

Understanding the contribution of road-deposited sediment (RDS) and its washoff process is essential for controlling urban runoff pollution. Ninety-seven RDS samples were collected along the urban–suburban–rural gradient from areas of five administrative units in the Beijing metropolitan region, including central urban (UCA), urban village (UVA), central suburban county (CSA), rural town (RTA), and rural village (RVA) areas. RDS washoff was evaluated with different particle sizes using a rainfall simulator. Heavy metal elements (i.e., Cr, Cu, Ni, Pb, and Zn) were estimated in both RDS and runoff samples. The RDS mass per unit area increased in the order UCA (21 ± 24 g/m2) ≈ CSA (20 ± 16 g/m2) < RTA (59 ± 63 g/m2) < RVA (147 ± 112 g/m2) ≈ UVA (147 ± 198 g/m2). Compared to RDS from the other administrative units, RDS from the UCA and CSA had higher metal concentrations and higher proportions of smaller particles, whereas that from the RVA and UVA had larger quantities of metals per unit area. UCA and CSA had lower potential runoff pollution contributions per unit area. Our findings imply that controlling the first flush in the UCA and CSA, and improving existing street cleaning methods and road surface conditions in the TRA, UVA, and RVA will be appropriate strategies for controlling runoff pollution from RDS.

Abstract. We studied sediments from the ca. 1400 millionyear-old Xiamaling Formation from the North China block. The upper unit of this formation (unit 1) deposited mostly below storm wave base and contains alternating black and green-gray shales with very distinct geochemical characteristics. The black shales are enriched in redox-sensitive trace metals, have high concentrations of total organic carbon (TOC), high hydrogen index (HI) and iron speciation indicating deposition under anoxic conditions. In contrast, the green-gray shales show no trace metal enrichments, have low TOC, low HI and iron speciation consistent with an oxygenated depositional setting. Altogether, unit 1 displays alternations between oxic and anoxic depositional environments, driving differences in carbon preservation consistent with observations from the modern ocean. We combined our TOC and HI results to calculate the differences in carbon mineralization and carbon preservation by comparing the oxygenated and anoxic depositional environments. Through comparisons of these results with modern sedimentary environments, and by use of a simple diagenetic model, we conclude that the enhanced carbon mineralization under oxygenated conditions in unit 1 of the Xiamaling Formation required a minimum of 4 to 8 % of present-day atmospheric levels (PAL) of oxygen. These oxygen levels are higher than estimates based on chromium isotopes and reinforce the idea that the environment contained enough oxygen for animals long before their evolution.

Because of uncomfortable, painful and even deleterious effects of daily injection of insulin, extensive efforts are being made worldwide for developing noninvasive drug delivery systems, especially via the oral route. In this study, we synthesized hydroxyethyl methacrylate (HEMA) nanogel via emulsion polymerization method. The morphology and stability of the nanogel were characterized by scanning electronic microscope and dynamic light scattering. In vivo results showed the soft HEMA nanogel had longer half-live in the body circulation and exhibited almost negligible uptake by the macrophage cells as compared with blank cells. For the FITC-dextran tracking for intestinal penetration, the results indicated that the FITC-dextran in the soft nanogel penetrated faster from the inner side of the abdominal segment, which explained why the soft HEMA nanogel could promote intestinal absorption of encapsulated insulin. In vivo delivery of insulin encapsulated in the soft HEMA nanogel sustained blood glucose control for 12 h, and the overall bioavailability of administrated insulin was much higher than free insulin. Our results showed that the insulin-loaded HEMA nanogel was able to efficiently control blood glucose as a delivery system, suggesting the HEMA nanogel using emulsion polymerization could be an alternative carrier for oral insulin delivery.

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