Qingjun Guo

Sulfates are critical constituents of atmospheric fine particulate matter (PM _2.5 ) that significantly influence air quality and climate dynamics. While stable isotope fractionation analysis is a powerful tool for tracing atmospheric sulfate formation mechanisms, conventional isotopic models rely on idealized complete SO ₂ oxidation scenarios. This oversimplification introduces systematic errors and neglects vital kinetic isotope effects generated during incomplete SO ₂ processing. To address this knowledge gap, we established a field-validated analytical framework combining seasonal PM _2.5 observations in Nanjing, China, with Bayesian isotope mixing and process-specific Rayleigh fractionation modeling. Our kinetic fractionation-corrected approach accounts for actual atmospheric oxidation processes, revealing that transition-metal ion (TMI)-catalyzed and NO ₂ -mediated pathways dominate secondary sulfate production. Conversely, comparative analysis demonstrates that traditional complete-oxidation models disproportionately diminish TMI pathway contributions. Furthermore, implementing kinetic fractionation corrections successfully resolves systematic biases in source apportionment. We demonstrate that traditional models misrepresent source contributions, overestimating coal combustion by 10 % and underestimating traffic emissions by 8 % during summer photochemical episodes. These findings establish a refined isotopic tracing framework that resolves long-standing calculation discrepancies. Ultimately, this framework delivers essential constraints for atmospheric sulfur cycle modeling and underscores the necessity for multi-pollutant regulation strategies targeting vehicular emissions and co-emitted transition meals.

Sulfates represent a critical constituent of atmospheric fine particulate matter (PM_2.5), significantly influencing air quality and climate dynamics. Precise quantification of atmospheric sulfate formation mechanisms and emission sources through stable isotope fractionation analysis represents a critical advancement in particulate matter pollution control. Conventional isotopic models relying on idealized complete SO₂ oxidation scenarios, while providing preliminary source apportionment estimates, exhibit systematic errors in reaction pathway quantification. Our field-validated approach incorporating actual atmospheric oxidation processes demonstrates that transition-metal ions (TMI)-catalyzed and NO₂-mediated pathways dominate sulfate production, with coal combustion (overestimate by 10.8 % in summer) and traffic emissions (underestimated by 8.2 % in summer) constituting primary sources. Comparative analysis reveals that traditional complete-oxidation models disproportionately diminish TMI pathway contributions, highlighting the necessity of kinetic fractionation corrections. These findings establish an improved isotopic tracing framework that resolves longstanding calculation discrepancies, delivering essential constraints for atmospheric sulfur cycle modeling and emission regulation strategies.

Sulfates represent a critical constituent of atmospheric fine particulate matter (PM_2.5), significantly influencing air quality and climate dynamics. Precise quantification of atmospheric sulfate formation mechanisms and emission sources through stable isotope fractionation analysis represents a critical advancement in particulate matter pollution control. Conventional isotopic models relying on idealized complete SO₂ oxidation scenarios, while providing preliminary source apportionment estimates, exhibit systematic errors in reaction pathway quantification. Our field-validated approach incorporating actual atmospheric oxidation processes demonstrates that transition-metal ions (TMI)-catalyzed and NO₂-mediated pathways dominate sulfate production, with coal combustion (overestimate by 10.8 % in summer) and traffic emissions (underestimated by 8.2 % in summer) constituting primary sources. Comparative analysis reveals that traditional complete-oxidation models disproportionately diminish TMI pathway contributions, highlighting the necessity of kinetic fractionation corrections. These findings establish an improved isotopic tracing framework that resolves longstanding calculation discrepancies, delivering essential constraints for atmospheric sulfur cycle modeling and emission regulation strategies.

Sulfates represent a critical constituent of atmospheric fine particulate matter (PM_2.5), significantly influencing air quality and climate dynamics. Precise quantification of atmospheric sulfate formation mechanisms and emission sources through stable isotope fractionation analysis represents a critical advancement in particulate matter pollution control. Conventional isotopic models relying on idealized complete SO₂ oxidation scenarios, while providing preliminary source apportionment estimates, exhibit systematic errors in reaction pathway quantification. Our field-validated approach incorporating actual atmospheric oxidation processes demonstrates that transition-metal ions (TMI)-catalyzed and NO₂-mediated pathways dominate sulfate production, with coal combustion (overestimate by 10.8 % in summer) and traffic emissions (underestimated by 8.2 % in summer) constituting primary sources. Comparative analysis reveals that traditional complete-oxidation models disproportionately diminish TMI pathway contributions, highlighting the necessity of kinetic fractionation corrections. These findings establish an improved isotopic tracing framework that resolves longstanding calculation discrepancies, delivering essential constraints for atmospheric sulfur cycle modeling and emission regulation strategies.

Atmospheric particulate‐bound mercury (PBM), adsorbed onto aerosols like TSP and PM _2.5 (PBM _TSP and PBM _2.5 ), is crucial to the Hg biogeochemical cycle. However, the mechanisms underlying the formation and transportation of PBM remain unclear. This study aims to explore these mechanisms by utilizing Hg isotopes and collecting PBM _TSP and PBM _2.5 samples at five distinct sites in North China. Both PBM _TSP and PBM _2.5 exhibited positive odd and even mass‐independent fractionation (MIF), with Δ ¹⁹⁹ Hg values in PBM _2.5 enriched by 0.25 ± 0.35‰ relative to PBM _TSP . The slopes between Δ ¹⁹⁹ Hg and Δ ²⁰¹ Hg, along with sulfur MIF and backward trajectories, suggest that intense photoreduction reactions during long‐distance and high‐altitude transport are the primary driver of the elevated Δ ¹⁹⁹ Hg in fine particulate matter. Importantly, significant positive MIF signatures can occur not only in remote areas but also in anthropogenic Hg emission regions, underscoring the underestimated role of atmospheric transport, particularly on clean days.

Increasing industrial activity has led to a growing risk of cadmium (Cd) accumulations and biomagnifications in plants and humans. Arbuscular mycorrhizal fungi (AMF) have been extensively studied as a soil amendment technique due to their capability to reduce the accumulation of Cd in plant tissues. However, a quantitative and data-based consensus has yet to be reached on the effect of AMF on host plant growth, Cd uptake, and tolerance. Here, a meta-analysis was conducted to quantitatively evaluate the impact of AMF using 2079 individual observations from 157 articles. The research showed that adding AMF to the plants stopped the accumulation of Cd in the shoots and roots and increased biomass, phosphorus (P), and catalase (CAT) in the leaves compared to the control. Yet these effects varied with different mycorrhizal colonization rates, AMF species, plant families and functional types, and soil Cd contents. Mycorrhizal colonization rates positively correlate with changes in biomass and P content in shoots and roots, and CAT and proline in leaves, while showing no significant correlation with Cd concentration in plant tissues. Plants inoculated with Funneliformis caledonium exhibited greater biomass accumulation, while those inoculated with Rhizophagus irregularis showed higher P uptake. Mycorrhizal Legumes demonstrated the most significant reduction in Cd concentration among the plant families, whereas Compositae exhibited the highest increase in biomass, P content, and CAT. In addition, soils with intermediate and high Cd levels were more favorable for AMF to promote plant biomass accumulation. This study shows that AMF can help plants become more resistant to environments with excessive Cd. It also talks about how to manage and use them as bio-inoculants for farming and environmental restoration. AcknowledgmentsThis research received funding from the National Key Research and Development Program of China (No. 2022YFC3701303) and the National Natural Science Foundation of China (Grant Nos. U2344228).