Mei Zheng

The iron cycle is a fundamental component of the Earth system. Growing evidence indicates that anthropogenic emissions can significantly perturb the iron cycle, beyond the influence of natural dust. The iron isotope technique has emerged as a powerful tool for quantifying anthropogenic iron in the marine environment. However, anthropogenic contributions derived from such an apportionment approach are highly sensitive to the selection of isotopic end‐members, which are mainly determined by source tests and inconsistent across literature. Analysis of aerosol samples collected during a spring 2022 cruise in the Chinese marginal seas showed that anthropogenic iron contributions traced by isotope analysis ranged from 0.12 ± 0.12 to 0.43 ± 0.24, depending on the end‐members derived from literature. To address uncertainty, an observation‐based approach was developed to constrain isotopic end‐members directly from ambient measurements. Shipborne high‐time‐resolution measurements of multiple elements were conducted, and a Positive Matrix Factorization (PMF) receptor model was used to quantitatively distinguish dust and anthropogenic contributions to iron. By combining the constraints from PMF results with filter‐based iron isotope measurements, isotopic end‐members of +0.44‰ for dust iron and −1.43‰ for anthropogenic iron were newly determined in ambient aerosol. Applying these updated end‐members to iron sources based on previously published iron isotope data sets from the North Pacific indicates that anthropogenic contributions were ubiquitously underestimated, with maximum underestimation likely exceeding 30%. The application of observation‐based end‐members, as opposed to the conventional source‐test‐based end‐members, allows for more accurate quantification of anthropogenic iron inputs by better capturing isotopic fractionation during atmospheric transport, thereby advancing isotope biogeochemistry.

The atmospheric environment of the Tibetan Plateau is significantly sensitive to pollutants transported from regions with intensive anthropogenic activity. It is therefore critical to identify source regions and transported air pollutants on the Tibetan Plateau. The present study developed a method to link multiple pollutants measured at receptor sites on the Tibetan Plateau to their source regions by integrating measurements and modeling. Ground-based measurements of over 150 species in fine particulate matter (PM2.5) at the Nam Co Station were conducted for one year. Meanwhile, contributions from different source regions to PM2.5 in each sample were quantified by using an emission inventory-coupled Lagrangian box model. The findings indicated that specific source regions were associated with distinct chemical species and sources. In the premonsoon season, transport from the northwestern South Asia was related to enhanced concentrations of black carbon, organic carbon, K+, anhydrosugars, Pb, and Zn. This suggested a strong influence from intensive biomass burning and industrial activities. However, increased contribution from the northwestern China to PM2.5 was associated with increased concentrations of low-molecular-weight polycyclic aromatic hydrocarbons, Cl–, and several anthropogenic metals, reflecting impacts from mixed industrial and residential sources. During the monsoon season, concentrations of highly oxidized secondary organic aerosol (SOA) species increased with contribution from regions south of the receptor site, highlighting the importance of aged SOA in this season. The findings in this study not only improve our understanding of how transport from different regions shapes atmospheric composition in the Tibetan Plateau but also offer a new approach to investigate impacts of long-range transport on remote environments.

Non-dust emissions have been increasingly recognized as important contributors to atmospheric iron (Fe), influencing marine productivity through enhanced bioavailable Fe inputs. However, accurately quantifying the contributions and spatiotemporal variability of non-dust sources remains challenging due to relatively low time-resolution of traditional filter-based analytical methods. In this study, the contributions of non-dust emissions to atmospheric total and soluble Fe in the Northwest Pacific were quantified based on online measurements from three ship-based observation campaigns in 2021–2022. A Positive Matrix Factorization (PMF) model was applied for source apportionment. Results showed non-dust emissions were notable contributors to atmospheric total Fe, representing 24 %–41 % of total Fe in PM₁₀ and 30 %–56 % in PM_2.5 samples across different cruise legs. Importantly, their contributions to soluble Fe were significantly higher, reaching 88 %–97 % in PM₁₀ and 85 %–98 % in PM_2.5 samples. Among non-dust sources, land anthropogenic emissions contributed substantially to both total and soluble Fe, whereas ship emission contributed a small portion to total Fe but was a major source of soluble Fe, particularly in summer, when its contribution reached 79 % of soluble Fe in PM₁₀ samples in coastal regions. Additionally, Fe from non-dust sources exhibited stronger spatial variability than dust source. The concentrations of land anthropogenic Fe differed by 3–5 times between coastal and open-ocean areas during the same cruises, while ship-derived Fe varied by an order of magnitude or more. This study offers critical observational evidence to advance understanding of how diverse emission sources shape atmospheric composition in Asian continental outflow regions.

Non-dust emissions have been increasingly recognized as important contributors to atmospheric iron (Fe), influencing marine productivity through enhanced bioavailable Fe inputs. However, accurately quantifying the contributions and spatiotemporal variability of non-dust sources remains challenging due to relatively low time-resolution of traditional filter-based analytical methods. In this study, the contributions of non-dust emissions to atmospheric total and soluble Fe in the Northwest Pacific were quantified based on online measurements from three ship-based observation campaigns in 2021–2022. A Positive Matrix Factorization (PMF) model was applied for source apportionment. Results showed non-dust emissions contributed substantially to atmospheric Fe, accounting for 21 %–48 % of total Fe across different regions and seasons. Importantly, their contributions to soluble Fe were significantly higher, reaching 79 %–98 % and largely dominating the bioavailable Fe supply in the study area. Among non-dust sources, land anthropogenic emissions contributed significant portion of both total and soluble Fe, whereas ship emissions contributed small portion to total Fe but was major source of soluble Fe, particularly in coastal regions. In summer, ship emissions over coastal waters even exceeded land anthropogenic sources, becoming the dominant contributor to soluble Fe. Additionally, Fe from non-dust sources exhibited stronger spatial variability than dust source. The concentrations of land anthropogenic Fe differed by 3–5 times between coastal and open-ocean areas during the same cruises, while ship-derived Fe varied by an order of magnitude or more. This study offers critical observational evidence to advance understanding of how diverse emission sources shape atmospheric composition in Asian continental outflow regions.

Non-dust emissions have been increasingly recognized as important contributors to atmospheric iron (Fe), influencing marine productivity through enhanced bioavailable Fe inputs. However, accurately quantifying the contributions and spatiotemporal variability of non-dust sources remains challenging due to relatively low time-resolution of traditional filter-based analytical methods. In this study, the contributions of non-dust emissions to atmospheric total and soluble Fe in the Northwest Pacific were quantified based on online measurements from three ship-based observation campaigns in 2021–2022. A Positive Matrix Factorization (PMF) model was applied for source apportionment. Results showed non-dust emissions contributed substantially to atmospheric Fe, accounting for 21 %–48 % of total Fe across different regions and seasons. Importantly, their contributions to soluble Fe were significantly higher, reaching 79 %–98 % and largely dominating the bioavailable Fe supply in the study area. Among non-dust sources, land anthropogenic emissions contributed significant portion of both total and soluble Fe, whereas ship emissions contributed small portion to total Fe but was major source of soluble Fe, particularly in coastal regions. In summer, ship emissions over coastal waters even exceeded land anthropogenic sources, becoming the dominant contributor to soluble Fe. Additionally, Fe from non-dust sources exhibited stronger spatial variability than dust source. The concentrations of land anthropogenic Fe differed by 3–5 times between coastal and open-ocean areas during the same cruises, while ship-derived Fe varied by an order of magnitude or more. This study offers critical observational evidence to advance understanding of how diverse emission sources shape atmospheric composition in Asian continental outflow regions.

Non-dust emissions have been increasingly recognized as important contributors to atmospheric iron (Fe), influencing marine productivity through enhanced bioavailable Fe inputs. However, accurately quantifying the contributions and spatiotemporal variability of non-dust sources remains challenging due to relatively low time-resolution of traditional filter-based analytical methods. In this study, the contributions of non-dust emissions to atmospheric total and soluble Fe in the Northwest Pacific were quantified based on online measurements from three ship-based observation campaigns in 2021–2022. A Positive Matrix Factorization (PMF) model was applied for source apportionment. Results showed non-dust emissions contributed substantially to atmospheric Fe, accounting for 21 %–48 % of total Fe across different regions and seasons. Importantly, their contributions to soluble Fe were significantly higher, reaching 79 %–98 % and largely dominating the bioavailable Fe supply in the study area. Among non-dust sources, land anthropogenic emissions contributed significant portion of both total and soluble Fe, whereas ship emissions contributed small portion to total Fe but was major source of soluble Fe, particularly in coastal regions. In summer, ship emissions over coastal waters even exceeded land anthropogenic sources, becoming the dominant contributor to soluble Fe. Additionally, Fe from non-dust sources exhibited stronger spatial variability than dust source. The concentrations of land anthropogenic Fe differed by 3–5 times between coastal and open-ocean areas during the same cruises, while ship-derived Fe varied by an order of magnitude or more. This study offers critical observational evidence to advance understanding of how diverse emission sources shape atmospheric composition in Asian continental outflow regions.

Non-dust emissions have been increasingly recognized as important contributors to atmospheric iron (Fe), influencing marine productivity through enhanced bioavailable Fe inputs. However, accurately quantifying the contributions and spatiotemporal variability of non-dust sources remains challenging due to relatively low time-resolution of traditional filter-based analytical methods. In this study, the contributions of non-dust emissions to atmospheric total and soluble Fe in the Northwest Pacific were quantified based on online measurements from three ship-based observation campaigns in 2021–2022. A Positive Matrix Factorization (PMF) model was applied for source apportionment. Results showed non-dust emissions contributed substantially to atmospheric Fe, accounting for 21 %–48 % of total Fe across different regions and seasons. Importantly, their contributions to soluble Fe were significantly higher, reaching 79 %–98 % and largely dominating the bioavailable Fe supply in the study area. Among non-dust sources, land anthropogenic emissions contributed significant portion of both total and soluble Fe, whereas ship emissions contributed small portion to total Fe but was major source of soluble Fe, particularly in coastal regions. In summer, ship emissions over coastal waters even exceeded land anthropogenic sources, becoming the dominant contributor to soluble Fe. Additionally, Fe from non-dust sources exhibited stronger spatial variability than dust source. The concentrations of land anthropogenic Fe differed by 3–5 times between coastal and open-ocean areas during the same cruises, while ship-derived Fe varied by an order of magnitude or more. This study offers critical observational evidence to advance understanding of how diverse emission sources shape atmospheric composition in Asian continental outflow regions.