Junfeng Ji’s research while affiliated with Nanjing University and other places

The response of the East Asian summer monsoon (EASM) precipitation to Pleistocene global cooling is crucial for understanding Earth's climate and hydrological cycles. The long‐term trend of the EASM precipitation during the Pleistocene remains hotly debated with two main hypotheses: one suggesting a gradually weakening EASM driven by global cooling, whereas the other proposing a gradually intensifying EASM influenced by the uplift of the Tibetan Plateau or strengthening Pacific Walker Circulation. The primary challenge in resolving this debate lies in disentangling the temperature effects from existing monsoon precipitation proxies, which complicates the interpretation of past climate records. Here, we present a new record of Pleistocene EASM precipitation change from North China, based on soil dolomite and calcite contents that are independent of temperature. Our results indicate increased interglacial EASM precipitation but near‐constant glacial EASM precipitation in the long‐term trend. This finding challenges the conventional view that global cooling weakened monsoon precipitation. We propose that Pleistocene EASM long‐term evolution is controlled by the competition between the monsoon‐weakening effects of global cooling and the monsoon‐enhancing effects of the strengthening Walker Circulation, suggesting that even a cooling climate could strengthen monsoon precipitation. Our results hold profound implications for assessing the complex relationship between hydroclimatic cycles and global temperatures during the late Cenozoic.

Enhanced silicate weathering (ESW) is a geoengineering method aimed at accelerating carbon dioxide (CO2) removal (CDR) from atmosphere by increasing the weathering flux of silicate rocks and minerals. It has emerged as a promising strategy for CDR. Theoretical studies underscore ESW’s substantial potential for CDR and its diverse benefits for crops when applied to croplands. However, the well-known significant discrepancies in silicate weathering rates between laboratory and field conditions introduce uncertainty in CDR through ESW. By compiling data from recent literature, we calculated and compared CDR efficiency (t CO2 tsilicate−1 ha−1 y−1) observed in mesocosm experiments and field trials. The findings indicate that CDR efficiencies in field trials are comparable to or exceeding that observed in mesocosm experiments by 1–3 orders of magnitude, particularly evident with wollastonite application. The hierarchy of CDR efficiency among silicates suitable for ESW is ranked as follows: olivine ⩾ wollastonite > basalt > albite ⩾ anorthite. We suggest the potential role of biota, especially fungi, in contributing to higher CDR efficiencies observed in field trials compared to mesocosm experiments. We further emphasize introducing fungi known for their effectiveness in silicate weathering could potentially enhance CDR efficiency through ESW in croplands. But before implementing fungal-facilitated ESW, three key questions need addressing: (i) How does the community of introduced fungi evolve over time? (ii) What is the long-term trajectory of CDR efficiency following fungal introduction? and (iii) Could fungal introduction lead to organic matter oxidation, resulting in elevated CO2 emissions? These investigations are crucial for optimizing the efficiency and sustainability of fungal-facilitated ESW strategy.

Heavy metals were analyzed in rhizosphere soils and rice grains collected from typical black shale areas. The concentrations of As, Cd, Cu, and Zn in the rhizosphere soil exceeded the current soil environmental quality standards. Cd exhibited the highest bioaccumulation capacity, with 45% of rice grains exceeding food safety limit. Structural equation modeling (SEM) revealed that soil organic matter indicated that 34.79% of rice Cd accumulation and approximately 10%–25% of other metals were inhibited. Multiple regression modelling showed that in areas with high geological background of black shales, the screening and intervention values for soil Cd were adjusted to 0.24 mg kg⁻¹ and 0.42 mg kg⁻¹ for pH ≤ 5.5 and 0.27 mg kg⁻¹ and 1.66 mg kg⁻¹ for pH 5.5 – 6.5 respectively. Primary exposure pathways for non-carcinogenic risks were identified as food ingestion and skin contact. This study provides fundamental information for land use application and development in region with high geological background.

Silicate weathering acts as a significant carbon sink and sustains ecosystems by supplying essential elements, thus shaping Earth's habitability. However, our understanding the evolution of silicate weathering rates remains incomplete, with most knowledge focusing on rate decreases at solution‐silicate interfaces, while reactivity at fungi‐weathered silicate interfaces is poorly understood. This study shows that the fungus Talaromyces flavus significantly enhances the dissolution of olivine and lizardite covered by Si‐rich layers up to 3.6 μm thick by one to two orders of magnitude compared to abiotic conditions. Initially, fungal hyphae create dissolution channels ∼10–65 nm deep, promoting element release from altered layers and underlying pristine minerals while oxidizing structural Fe(II). Over time, hyphae penetrate these altered layers, exposing and etching the underlying minerals. Our data suggest that fungal etching and penetration degrade the altered layers, leading to increased interdiffusion of weathering agents and released cations, thereby continuously driving silicate weathering.

Rice and wheat, being major food crops worldwide, are susceptible to pollution risks associated with potentially toxic elements (PTEs). However, the accumulation and transfer patterns of different PTEs within rice and wheat systems remain a topic of debate. In this study, we conducted a holistic investigation of the risk flow of seven PTEs (As, Cd, Cr, Cu, Ni, Pb, and Zn) in the soil-root-straw-grain continuum of a typical rice-wheat rotation system. Laboratory analyses were performed on a total of 72 samples, comprising complete rice and wheat plants as well as paired soil samples. These samples were collected from nine cropland sites located in the Yangtze River Delta (YRD), a highly industrialized region in China. Our results revealed that Cd and Pb levels in the soils exceeded acceptable limits. Additionally, Cd, Cr, Ni, Pb, and Zn levels in wheat grains, as well as Cd in rice grains, exceeded food safety standards. Based on their behaviors within the soil-root-straw-grain continuum of rice and wheat, the seven PTEs can be classified into three categories: (1) The siderophile elements, Cr and Ni, exhibited higher concentrations in wheat roots, straws, and grains than in rice. (2) The chalcophile elements, Cd, Cu, Zn, and Pb, showed higher contents in rice roots and straws but lower contents in rice grains than in wheat. (3) The metalloid element, As, exhibited significantly higher concentrations and uptake capacity in rice than in wheat. Our findings suggest that wheat has a greater internal translocation capacity for PTEs than rice, leading to higher contamination levels and lower risk resistances for wheat crops. This study provides insights into agronomic regulations of different PTEs in rice and wheat cultivation areas.

Black shale-derived soils exhibit significant heavy metal enrichment, notably cadmium (Cd) enrichment. This study pioneered the reporting of δ114/110Cd isotopic values within a black shale-soil system, offering novel insights into the geochemical behaviors and enrichment mechanisms of Cd during soil formation processes influenced by weathering. Systematic rock‒soil sampling was conducted on the lower Cambrian Hetang Formation in western Zhejiang, China, which is characterized by Cd-rich black shale. Employing analytical methods, including principal component analysis and multiple linear regression, we investigated the factors influencing heavy metal content in soil, such as element dissolution during weathering, soil pH, and the presence of iron-manganese oxides, sulfides, organic matter, and clay minerals. Our findings revealed a compositional range of δ114/110Cd in black shale (1.93‰–3.31‰) contrasting with that in adjacent soils (0.31‰–1.82‰), illustrating significant Cd isotopic fractionation during weathering, where heavier Cd isotopes are preferentially leached, and lighter isotopes are enriched in the soil in association with iron-manganese oxides. This research not only deepens the understanding of Cd enrichment mechanisms within the rock‒soil system against a black shale geological background but also elucidates the formation processes of soil Cd pollution in areas with a high geochemical background.