科研成果

In recent decade the ambient fine particle (PM2.5) levels have shown a trend of distinct dropping in China, while ground-level ozone concentrations have been increasing in Beijing and many other Chinese mega-cities. The variation pattern in Los Angeles was markedly different, with PM2.5 and ozone decreasing together over past decades. In this study, we utilize observation-based methods to establish the parametric relationship between PM2.5 concentration and key aerosol physical properties (including aerosol optical depth and aerosol surface concentration), and an observation-based 1-D photochemical model to quantify the response of PM2.5 decline in enhancing ground-level ozone pollution over a large PM2.5 concentration range (10–120 μg m−3). We find that the significance of ozone enhancement due to PM2.5 dropping depends on both the PM2.5 levels and optical properties of particles. Ozone formation increased by 37% in 2006–2016 due to PM2.5 dropping in Beijing, while it becomes less important (7%) as PM2.5 reaches below 40 μg/m3, similar to Los Angeles since 1980s. Therefore, the two cities show the convergence of air pollutant characteristics. Hence a control strategy prioritizing reactive volatile organic compound abatement is projected to yield simultaneous ozone and PM2.5 reductions in Beijing, as experienced in Los Angeles.

We quantify the macroeconomic and welfare effects of a social health insurance reform that occurred in China in 2016 using a two-sector model with endogenous rural-to-urban migrant workers. The calibrated model mimics the rural-to-urban migration and rural-urban wage gap from 2007 through 2016. We find that the health insurance reform depresses rural-to-urban migration and leads to reallocation of labor and capital in both the rural and urban sectors. As the result, we find that the consolidation of premium and reimbursement expands the rural-urban wage gap by approximately 6.8% but universal health insurance coveragenarrows the rural-urban wage gap by approximately 0.9%. Keeping the government deficit unchanged, the welfare results favor universal health insurance relative to pure consolidation.

With the successful implementation of the Montreal Protocol on Substances that Deplete the Ozone Layer, the atmospheric abundance of ozone-depleting substances continues to decrease slowly and the Antarctic ozone hole is showing signs of recovery. However, growing emissions of unregulated short-lived anthropogenic chlorocarbons are offsetting some of these gains. Here, we report an increase in emissions from China of the industrially produced chlorocarbon, dichloromethane (CH2Cl2). The emissions grew from 231 (213–245) Gg yr−1 in 2011 to 628 (599–658) Gg yr−1 in 2019, with an average annual increase of 13 (12–15) %, primarily from eastern China. The overall increase in CH2Cl2 emissions from China has the same magnitude as the global emission rise of 354 (281−427) Gg yr−1 over the same period. If global CH2Cl2 emissions remain at 2019 levels, they could lead to a delay in Antarctic ozone recovery of around 5 years compared to a scenario with no CH2Cl2 emissions.

The cardiovascular risk equations for diabetes patients from New Zealand and Chinese electronic health records (CREDENCE) study is a unique prospectively designed investigation of cardiovascular risk in two large contemporary cohorts of people with type 2 diabetes from New Zealand (NZ) and China. The study was designed to derive equivalent cardiovascular risk prediction equations in a developed and a developing country, using the same epidemiological and statistical methodology. Two similar cohorts of people with type 2 diabetes were identified from large general population studies in China and New Zealand, which had been generated from longitudinal electronic health record systems. The CREDENCE study aims to determine whether cardiovascular risk prediction equations derived in patients with type 2 diabetes in a developed country are applicable in a developing country, and vice versa, by deriving and validating equivalent diabetes-specific cardiovascular risk prediction models from the two countries. Baseline data in CREDENCE was collected from October 2004 in New Zealand and from January 2010 in China. In the first stage of CREDENCE, a total of 93,207 patients (46,649 from NZ and 46,558 from China) were followed until December 31st 2018. Median follow-up was 7.0 years (New Zealand) and 5.7 years (China). There were 5926 (7.7% fatal) CVD events in the New Zealand cohort and 3650 (8.8% fatal) in the Chinese cohort. The research results have implications for policy makers, clinicians and the public and will facilitate personalised management of cardiovascular risk in people with type 2 diabetes worldwide.

CO2 sequestration and CO2 enhanced oil recovery (CO2-EOR) are two major processes that can expose the rock to CO2. The behavior of a rock when saturated with CO2 changes over time, affecting both the mechanical and chemical properties of the host rock. CO2 operation involves the injection and pressurization of reservoirs that usually results in changes to the state of in situ stresses that may initiate fractures. This can lead to slippage along pre-existing fracture and fault systems. CO2 storage in tight formations, either for EOR or sequestration purposes, is imperative to contribute to the current energy transition and mitigate climate change. Thus, injection of CO2 may alter the mineralogy, pore structure, mechanics, and other properties and behavior of tight reservoirs, and sometimes may be susceptible to leakage through induced fractures or reactivated faults. Here, we aim to evaluate and reassess studies on CO2 sequestration in tight reservoirs and associated formations. This report focuses on the changes in properties and behavior of tight rocks (shale and tight carbonate rocks) due to CO2 exposure through CO2 sequestration or CO2-EOR. We highlight the most important findings from available studies to date, and we recommend promising areas of research that can advance the knowledge and development of CO2 sequestration in tight formations.

Photocatalytic nitrogen fixation represents an effective technology for the artificial production of ammonia from atmospheric nitrogen, a critical step toward a sustainable economy. Bismuth oxyhalides (BiOX, X = Cl, Br, and I) have emerged as viable catalysts for photocatalytic reduction of nitrogen into ammonia, due to their unique electronic structures and optical properties. Herein, the recent progress of BiOX-based photocatalysts for nitrogen fixation, with a focus on the reaction mechanism and pathways, materials preparation, and strategies of structural engineering for enhanced performance, is summarized. The article is concluded with a perspective where the promises and challenges of bismuth-based photocatalysts for nitrogen reduction to ammonia are highlighted, along with possible future research directions.

Abstract Polymerization sites of small molecule acceptors (SMAs) play vital roles in determining device performance of all-polymer solar cells (all-PSCs). Different from our recent work about fluoro- and bromo- co-modified end group of IC-FBr (a mixture of IC-FBr1 and IC-FBr2), in this paper, we synthesized and purified two regiospecific fluoro- and bromo- substituted end groups (IC-FBr-o & IC-FBr-m), which were then employed to construct two regio-regular polymer acceptors named PYF-T-o and PYF-T-m, respectively. In comparison with its isomeric counterparts named PYF-T-m with different conjugated coupling sites, PYF-T-o exhibits stronger and bathochromic absorption to achieve better photon harvesting. Meanwhile, PYF-T-o adopts more ordered inter-chain packing and suitable phase separation after blending with the donor polymer PM6, which resulted in suppressed charge recombination and efficient charge transport. Strikingly, we observed a dramatic performance difference between the two isomeric polymer acceptors PYF-T-o and PYF-T-m. While devices based on PM6:PYF-T-o can yield power conversion efficiency (PCE) of 15.2?%, devices based on PM6:PYF-T-m only show poor efficiencies of 1.4?%. This work demonstrates the success of configuration-unique fluorinated end groups in designing high-performance regular polymer acceptors, which provides guidelines towards developing all-PSCs with better efficiencies.

<p id="C2"><strong>Aims:</strong> The genome size between species, especially in angiosperms, can be extremely diverse. Here, we compiled genome size data for 11,215 angiosperm species from 2,226 genera and 245 families to explore the relationships between four functional traits (i.e. seed mass, maximum plant height, leaf nitrogen and phosphorus concentrations) with genome size in angiosperms from different life forms (i.e. annual herbs, perennial herbs, and woody plants).<br><strong>Method:</strong> We used the 1C-value of DNA content as a measurement for genome size. Genome sizes were obtained from the latest version of Kew Plant DNA C-values Database and Genome Size in Asteraceae Database (GSAD). We also complemented our taxon sampling with data from the literature over the past 10 years. We obtained life form and functional trait from <i>Flora of China</i>, <i>Flora of North America</i> and the Seed Information Database (SID). We used the most recent updated time-calibrated phylogeny published by Smith and Brown in 2018, and pruned it to the 6,612 species from our species list. We used two indices (i.e. Blomberg’s <i>K </i>and Pagel’s <i>λ</i>) to test for the prescence of a phylogenetic signal for the evolution of angiosperm genome size. We performed a standardized major axes (SMA) Model II and focused on the relationships between genome size and the four functional traits. We also conducted a principal components analysis (PCA) to explore trade-offs between functional traits and genome size in angiosperms with different life forms.<br><strong>Results:</strong> The genome size for most angiosperms was small and few species had large genomes. The median value of angiosperm genome size was 1.58 pg with perennial herbs having the largest median genome size (2.5 pg), followed by annual herbs (1.55 pg), and then woody species (1.14 pg). Variation of the genome size was greatest in perennial herbs distributed over a wider range than woody species and then annual herbs. Tests for phylogenetic signals with genome size indicated that evolution was non-random. The value for Blomberg’s <i>K</i> was 0.031 (<i>P</i>&lt; 0.001) and the value for Pagel’s <i>λ</i> was 0.943 (<i>P</i>&lt; 0.001. There was also a significant difference between functional traits and genome size among the three different life forms. Our results from the standardized major axes regression found that there was a significant relationship between seed mass with genome size in herbs but not woody plants. However, the relationship of maximum plant height was significant with genome size in woody plants but not herbs. There were no significant correlations between leaf nitrogen or phosphorus concentration with genome size except for leaf nitrogen concentration in woody plants. When looking at the relationship between four functional traits with genome size, we fund a negative correlation between seed mass and maximum plant height with genome size, and saw no significant correlation with leaf nitrogen or phosphorus concentration which is consistent with the SMA results.<br><strong>Conclusion:</strong> Our study highlights that the correlation between functional traits and genome size vary between herbaceous and woody species and suggests that trade-offs between genome size, life forms and functional traits might play an essential role in ecological adaptation and evolution of angiosperms.</p>