Guangzhou Institute of Geochemistry

• Biomass burial rates first increased before 1000 Ma, in the Mesoproterozoic. • Significant O 2 production began prior to the late Neoproterozoic Oxidation Event. • Estimated biomass burial rates are used to calculate annual fluxes for O 2 production. Strongly Peraluminous Granites (SPGs) are mostly formed by the partial melting of Al-rich sedimentary rocks and can reflect the chemical properties of their sedimentary protoliths. Recent work suggests that the nitrogen content ([N]) of SPGs preserve changes in biomass burial over time (Mikhail et al., 2024). This mechanism occurs because in unaltered samples, SPGs with elevated [N] are thought to reflect the elevated [N] of their sedimentary protolith, and this additional nitrogen would come from sediment-hosted biomass. This archive reveals an increase in biomass burial by a factor of 5- to 8-fold between 1.4–0.5 Ga. In this study, we analysed the nitrogen abundances and isotopic values of SPG samples from 1.0 to 0.7 Ga to better resolve the period when biomass burial increased. We find that SPG [N] increases 2.4-fold across the Mesoproterozoic-Neoproterozoic boundary at 1.0 Ga and 2.8-fold across the Neoproterozoic-Phanerozoic boundary at 0.5 Ga. Therefore, with consideration of the time lag from biomass burial to SPG formation, we suggest that biomass burial first began to increase in the late Mesoproterozoic. Biomass burial removes organic carbon, a reductant, from Earth’s surface, causing a net production of O 2 . Therefore, these data permit us to calculate an increase in O 2 production from biomass burial starting in the Mesoproterozoic, yielding an additional 6.3 × 10 20 to 30 × 10 20 moles of O 2 throughout the Neoproterozoic, possibly contributing to the Neoproterozoic Oxygenation Event and to the chain of events which resulted in an environment capable of supporting animal life in the Cambrian.

Abstract. Organic nitrates (ONs) are important temporary reservoirs of atmospheric NOx and, for sufficiently low-volatility species, contributors to secondary organic aerosol formation. However, online measurements of particle-phase ONs remain limited, hindering quantitative constraints on ON abundance and gas–particle partitioning. Here we present a five-channel thermal dissociation cavity-enhanced absorption spectrometer (TD–CEAS) for in situ, time-resolved measurements of NO2 and operationally defined ON classes in both the gas and particle phases. The instrument combines a room-temperature channel for ambient NO2 with thermal dissociation channels operated at 250 and 450 °C to quantify total peroxy nitrates (ΣPNs) and total alkyl nitrates (ΣANs), respectively. Gas–particle separation is achieved using paired inlet/filter configurations, and gas- and particle-phase ΣPNs and ΣANs are retrieved by channel differencing. The 1σ (1 s) detection limits are 49 pptv for gΣPNs, 49 pptv for pΣPNs, 48 pptv for gΣANs, and 68 pptv for pΣANs. Laboratory characterization included temperature-dependent dissociation measurements, cross-validation of PAN against GC–ECD (R2=0.988; slope = 0.987), and an operational calibration for particulate ΣANs using 2-ethylhexyl nitrate (recovery slope=1.036±0.028; method detection limit =0.029 µg NO2). Dedicated interference experiments showed that NO and NO2 can introduce substantial nonlinear biases in ΣPN measurements; these effects were parameterized using a multiple nonlinear regression model. The instrument was deployed at an urban site in Guangzhou during September–October 2025 and provided 6 min measurements of NO2, gas- and particle-phase ΣPNs, and gas- and particle-phase ΣANs under high-NOx conditions. During the October intensive period, corrected gas-phase ΣPNs covaried well with independently measured PAN (R2=0.83), and PAN accounted for 78 % of daytime gΣPNs. This five-channel TD–CEAS provides a framework for continuous observations of ON phase partitioning and reactive nitrogen processing in polluted urban atmospheres.

Abstract Light strongly regulates plant isoprene emissions, yet tropical light responses vary across studies, partly due to measurement protocol differences. Using a uniform portable chamber protocol across multiple sites, seasons, species, and temperatures in South China, we find a strikingly consistent rectangular‐hyperbolic isoprene light response across sunlit tropical leaves. Pooling 26 response curves yields α (the initial slope) of 0.0026 ± 0.0001, with no detectable light and temperature interaction on minute‐hour scales within our experiments for sunlit leaves. Relative to MEGAN's (Model of Emissions of Gases and Aerosols from Nature) default α = 0.0014, emission increases about twice faster under sub‐saturating photosynthetically active radiation, reducing underestimation in the morning/late afternoon conditions. Two modeling options match observations: adopt a static α = 0.0026 for sunlit tropical leaves, or increase the constant term in the α algorithm from 0.004 to 0.0053 for tropical Asia. These changes are straightforward to implement and improve diurnal isoprene simulations regionally.

Determining the origin of light oil presents a significant challenge due to the diversity of genetic types and the limitation of conventional biomarkers. Diamondoid hydrocarbons, characterized by their thermal stability and enrichment in high maturity oil, are considered effective indicators for elucidating generation mechanisms and secondary alteration processes of light oils. In this study, the diamondoid distributions are examined in light oil samples from various regions (i.e., Wushi, Bozi, Dabei, Keshen, Kela, Dina, Dibei, Tuzi, Tudong, Yangtake, Yingmai, Hongqi, and Yaha) in the Kuqa Depression of the Tarim Basin, Northwest China, to discern the origin of the oils. Diamondoids concentrations and ratios in the Kuqa oils show significant variations, indicating two dominant source rock types and various maturity levels. Total diamondoid concentrations (including adamantanes, diamantanes, and triamantanes) vary from 141 to 19,137 ppm. Notably, the light oils from the Kela and Tuzi regions exhibit unusually high diamondoid concentrations (> 9000 ppm), while those from Yingmai, Hongqi, Yaha, Wushi, Keshen, and Tudong regions have relatively lower concentrations (< 2000 ppm). Employing our previously developed source facies discriminant model based on multivariate statistical analysis of multiple diamondoid indices, we suggest that the light oils from the Kela, Keshen, Yangtake, and Yaha regions are originated from lacustrine shales. In contrast, the other studied samples are inferred to primarily derive from coaly source rocks. Meanwhile, our maturity prediction model indicates that the maturity of the Kuqa oils ranges from 0.81 to 2.44 EASY%Ro. The highest maturity is found in the Kela light oils (2.3-2.5 EASY%Ro), while the lowest maturity is observed in the samples from the Wushi, Yingmai, and Hongqi areas (0.8-1.1 EASY%Ro). The formation mechanisms for some samples with anomalous diamondoid distributions are also explored. The Kela light oils, distinguished by their high maturity, abundant diamondoids, and relatively high biomarker concentrations, demonstrate a mixed origin with a notable contribution from highly mature condensates derived from the maturation of lacustrine kerogens. The Tuzi coal-derived oils, exhibiting moderate maturity (1.25% EASYRo) and characterized by elevated adamantane concentrations coupled with inconsistently relatively lower diamantane concentrations, are inferred to be condensates underwent evaporative (or migration) fractionation during upward migration from deeper reservoirs. Our findings corroborate the potential application of diamondoids as previously suggested. In summary, the diamondoid hydrocarbons provide a robust methodology for elucidating the origins, thermal maturity, and formation mechanisms of light oils, particularly within highly mature systems.

Large Igneous Province (LIP) volcanism is widely invoked as a primary driver of major carbon-cycle perturbations and climate extremes in Earth history, yet its short-term eruptive tempo and terrestrial environmental impacts remain poorly constrained. Most existing models assume temporally smoothed volcanic carbon release, largely due to the limited temporal resolution of marine sedimentary archives. Here we present a sub-millennial-resolution lacustrine sedimentary record spanning Oceanic Anoxic Event 1a (OAE1a) from the Aptian Jiufotang Formation in the Kazuo Basin, northeastern China, providing a rare terrestrial perspective on high-frequency LIP activity. A total of 199 samples were collected from a ~130 kyr interval (covering the transition from high to low 187Os/188Os) of organic-rich lacustrine black shales, achieving a temporal resolution of ~0.3–1.0 kyr per sample—comparable to Quaternary paleoclimate studies but applied to a deep-time volcanic event. High-resolution stratigraphic profiles of carbon isotopes reveal repeated, abrupt excursions, indicating episodic volatile release associated with super-eruptive volcanism. These geochemical signals are stratigraphically coupled with sedimentological features, including volcanic ash layers, sulfide laminae, and storm-induced deposits, demonstrating that individual eruptive pulses are not only geochemically resolvable but also sedimentologically expressed. Additional Pb isotope constraints further support an Ontong Java Plateau mantle source. Importantly, the magnitude and frequency of lacustrine carbon isotope excursions exceed those typically observed in coeval marine records, implying strong terrestrial amplification through enhanced organic carbon burial, primary productivity blooms, and potentially intensified methanogenesis. These results challenge conventional time-averaged carbon-cycle models and highlight that the climatic and ecological impacts of LIP volcanism are governed by short-lived, threshold-crossing forcing events. Lacustrine systems thus provide a uniquely sensitive archive for resolving the true temporal structure of deep-time volcanic perturbations and their consequences for Earth’s surface environments.