Liang Zhao’s research while affiliated with Nanjing University and other places

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.

Silicate weathering, which is of great importance regulating global carbon cycle, has been found to be affected by complicate factors including climate, tectonics, vegetation, and etc. However, the exact transfer function between these factors and silicate weathering rate is still unclear, leading to large model-data discrepancies of the CO2 consumption associated with silicate weathering. Here we propose a simple parameterization for the influence of vegetation cover on erosion rate to improve the model-data comparison based on a state-of-the-art silicate weathering model. We found out that the current weathering model tends to overestimate the silicate weathering fluxes in the tropical region, which can hardly be explained by either the uncertainties in climate and geomorphological conditions or the optimization of model parameters. We show that such an overestimation of tropic weathering rate can be rectified significantly by considering the shielding effect of vegetation cover on the erosion rate of the leached soils considering that the geographic distribution of such soils is coincident with regions with the highest leaf area index (LAI). We propose that the heavy vegetation in the tropical region likely slows down the erosion rate, much more so than thought before, through reducing extreme stream flow in response to precipitation. The silicate weathering model thus revised gives a smaller global weathering flux which is arguably more consistent with the observed value and the recently reconstructed global outgassing, both of which are subject to uncertainties. The model is also easily applicable to the deep-time Earth to investigate the influence of land plant on global biogeochemical cycle.

CO2 mineral carbonation induced by microalgae is an emerging approach to carbon capture, utilization, and storage (CCUS). Freshwater cyanobacteria are common microalgae in nature that can raise the pH of eutrophic waters and drive the precipitation of carbonate. Still, limited studies have been conducted to evaluate and select appropriate cyanobacteria strains for CCUS. Here we present experimental investigations to compare the capacity of different freshwater cyanobacterial strains in converting CO2 to carbonates. We compare five cyanobacterial strains by monitoring their growth curves. We examine three metrics, the maximum pH of the solution, hydroxide production capacity, and extracellular polymeric substances (EPS) secretion capacity, to assess the capacity for carbon sequestration. Our results indicate that among the five strains, Microcystis aeruginosa shows the highest pH and EPS content per unit cell number, marking the most significant capacity for CO2 carbonation. We observe carbonate precipitates as hydromagnesite and dypingite. We suggest the negatively charged, hydrophilic EPS can effectively promote the precipitation of magnesium carbonate and inhibit the precipitation of calcium carbonate. Overall, our approach provides a framework for assessing and selecting cyanobacterial strains for CO2 carbonation, advancing the understanding of the mechanism of microalgae-induced CO2 Mg-carbonation from the perspective of EPS surface properties.

Plain Language Summary The provenance of silt‐sized particles in the Taklimakan Desert is critical for understanding aridification and climate dynamics in central Asia, as well as the production mechanism of dust—a key player in the global biogeochemical cycles of nutrient elements. Here, we measured the uranium‐strontium‐neodymium isotopes in silt‐sized particles from the Taklimakan Desert and the adjacent mountains to understand the source, production, and transport of dust in the region. The uranium isotopes record the timespan since particles were separated from the bedrock and are independent of bedrock composition. Our results indicate that the silt‐sized materials in the Taklimakan Desert are mainly sourced from the eastern Kunlun Shan, with partial contribution from the Pamir mountains. The isotopic evidence weakens the possibility that the Taklimakan Desert is a major source of the Chinese Loess Plateau. We found that besides mountainous (fluvial and glacial) processes, in‐situ desert processes (e.g., abrasion) produce a significant amount of the silts in the Taklimakan Desert and the aeolian dust flux from the Tarim Basin, which gets transported by the westerly jet and influences global ecosystems. These findings shed new light on dust production and transport in arid areas.

Fungi possess remarkable abilities to acquire mineral nutrients through foraging for and weathering minerals, and these fungal behaviors are influenced by the physiochemical properties of the minerals. Here, we investigated the dynamic processes underlying these behaviors in the interactions between the common fungus Talaromyces flavus and two serpentine minerals (antigorite and lizardite) and quartz as a control. In the culture of T. flavus on solid Czapek medium with these minerals, we found that the elongation rates of T. flavus hyphae toward antigorite and lizardite particles were similar, and both were much higher than those toward quartz particles. After reaching the minerals, the growth of T. flavus was promoted significantly by antigorite and lizardite. Atomic force microscopy measurements uncovered the production of distinct dissolution channels with a depth of 29.34 ± 6.18 nm on the lizardite surface, but no local dissolution was found on the antigorite surface. Laser ablation multicollector inductively coupled plasma mass spectrometric analysis indicated that the total Fe in T. flavus hyphae grown on the surfaces of lizardite and antigorite flakes was ~8.3 and 2.3 times, respectively of those grown on the surface of medium. Whewellite was ubiquitously found at the hyphal tips and their vicinity during T. flavus interactions with lizardite. These results demonstrate that fungal hyphae have a remarkable capacity to sense and respond to minerals and to extract structurally bound inorganic nutrients, and highlight that the instant weathering of minerals by fungi represents an important but unassessed contributor to the short-term release of mineral nutrients and should be incorporated into biogeochemical models.

The foraminifera shell Mg/Ca thermometer has been extensively used in reconstructing temperature evolution of the past oceans. An important, yet poorly understood observation is the 1-2 orders of magnitude lower Mg/Ca in foraminifera calcite shells than expected from inorganically precipitated calcite. Transient unstable carbonate was long hypothesized as a precursor of foraminiferal calcification, but its potential role in explaining apparent ‘vital effects’ of trace element partitioning is not well understood. In particular, a recent study has identified vaterite as a likely precursor phase during biomineralization of calcite foraminifera shells (Jacob et al., 2017). Here, we explore the possibility of vaterite as a precursor phase in affecting Mg incorporation into foraminifera calcite shells by experimentally calibrating the temperature dependent Mg partition coefficients between carbonate solution and vaterite under different solution Mg concentrations. The experimentally determined sensitivity of Mg incorporation into vaterite as a function of temperature (T in °C) is expressed as: ln⁡(λvateriteMg)=0.022±0.002⋅T−3.65±0.03. It is demonstrated that Mg partitioning is mainly controlled by the strain energy originated from cation substitution in the discontinuous lattices of vaterite particles, without distinct kinetic-controlled effects. We have developed a two-step partition model applying the above experimental results, with the assumption that vaterite is directly precipitated from a seawater-like fluid and later converts to calcite through dissolution-reprecipitation mediated by a second fluid in a localized environment. Within the constrained range of model parameters during phase conversion, the two-step partition model could directly reproduce foraminiferal calcite Mg/Ca temperature dependencies in both magnitude and sensitivity. Our model provides a theoretical framework that could be broadly applied to understand the impact of precursor phase on trace metal partition in biominerals. Overall, our study implies that the energy-consuming biological pumping of Mg outside foraminifera calcifying fluid, as widely believed, might not be a precondition for foraminifera shell mineralization.

This study investigated the reaction processes of microbially induced magnesium carbonate precipitation (MIMP) with Sporosarcina pasteurii (ATCC 11859) and evaluated its feasibility for controlling desertification in the desert areas in Northwest China. We explored systematically bacterial growth curves, mineralogy of precipitates, and relative chemical conversion efficiencies of the reaction using magnesium carbonate and bacterial urea hydrolysis with Sporosarcina pasteurii. We also compared the results of MIMP with the previously, well-studied microbially induced calcium carbonate precipitation (MICP). Our results indicate that excess Mg 2þ motivated bacterial growth slightly. Magnesium carbonate precipitates appeared as nesquehonite, Mg-amorphous calcium car-bonate, and Mg-rich calcite. The relative chemical conversion efficiency was higher in Mg medium than in Ca medium. We next evaluated the potential of using MIMP to mitigate desertification. We validated our results using the Mg-rich solution obtained by dissolving abandoned Mg salts that formed from the potassium salt plants nearby salt lakes. MIMP could potentially overcome shortcomings of traditional sand fixing methods, and was particularly suitable for controlling desertification in desert areas in Northwest China where there are abundant Mg resources. If MIMP works at field scales, this approach would further benefit ecosystem reconstruction because MIMP has main products of organic nutrients and ammonia, which would facilitate the development of biomass and soils. Overall, this work provides new insights into MIMP and its geoengineering potential in controlling desertification. ARTICLE HISTORY

Significance Coal combustion releases CO 2 but also leaves behind solid waste, or fly ash, which contains considerable amounts of carbon. The organic carbon sourced from fly ash resists chemical breakdown, and we find that it now contributes nearly half of the fossil organic carbon exported by the Chang Jiang—the largest river in Asia. The fly ash flux in this basin is similar to the natural sediment flux to the oceans because dam building has reduced sediment transport, while increased coal consumption generates abundant fly ash. Our results show that fly ash is an important component of the present-day carbon load in rivers and illustrates that human-driven carbon cycling can match the pace of the geological carbon cycle at decadal timescales.