Research on sustainable development evaluation and improvement path of resource-based cities based on coupling of emergy and system dynamics.

The evaluation of the sustainable development of resource-based cities is still one of the hotspots in today's social research. Taking Jining, Shandong Province, as the research object, this work combines a relevant emergy evaluation index system with system dynamics, establishes a resource-based city emergy flow system dynamics model, and studies sustainable development path in the next planning year. In the work, the key factors affecting the sustainable development of Jining are obtained through the coupling of regression and SD sensitivity analysis, and some scenarios are set up by combining them with the local 14th Five-year plan. Besides, the appropriate scenario (M-L-H-H) for Jining's future sustainable development is chosen in accordance with regional circumstances. That is, during the 14th Five-year Plan period, the appropriate development ranges for the growth rate of social fixed assets investment, the growth rate of raw coal emergy, the growth rate of grain emergy and the reduction rate of solid waste emergy are 17.5-18.3%, - 4.0 to - 3.2%, 1.8-2.6% and 4-4.8%. The methodology system constructed in this article can serve as a reference for similar studies, and the research findings can aid the government in formulating pertinent plans for resource-based cities.

Coordinated effects of energy transition on air pollution mitigation and CO2 emission control in China.

China has made progress in energy transition to improve air quality, but still confronts challenges including further ambient PM2.5 reduction, O3 pollution mitigation, and CO2 emission control. To explore the coordinated effects of energy transition on air quality and carbon emission in the near term in China, we designed 4 scenarios in 2025 based on different projections of energy transition progress with varying end-of-pipe control level, in each of which we calculated emissions of major air pollutants and CO2, and simulated ambient PM2.5 and O3 concentrations. Results show that energy transition has disparate effects on emission reduction of different air pollutants and sectors, which largely depends on their current end-of-pipe control levels. The different effects on emission reduction may result in opposite variation tendencies of ambient PM2.5 and O3 concentration in a future scenario with aggressive energy transition policies and end-of-pipe control level in 2018. With the end-of-pipe control level strengthened in 2025, PM2.5 and O3 concentration could both reduce on the national scale, but the reduction of ambient O3 lags behind PM2.5, indicating the difficulty of O3 pollution control. As to CO2, national emission would go up in 2025 either implementing current or aggressive energy transition policies due to growing needs of electricity and on-road transportation, but emissions in most provinces could decline to below the 2018 level with aggressive energy transition policies because of substitution of clean energy in industrial, residential and off-road transportation sectors. The study results suggest strictly implementing restrictive end-of-pipe control measures along with energy transition to simultaneously reduce ambient PM2.5 and O3 concentration, and accelerating substitution of renewable energy in power sectors where electricity generation grows rapidly to synergistically control air pollution and CO2 emissions. Furthermore, the projection of CO2 emissions could provide references for short-term emission control targets from the perspective of air quality improvement.

A comparative study of EOF and NMF analysis on downward trend of AOD over China from 2011 to 2019.

In recent decades China has experienced high-level PM2.5 pollution and then visible air quality improvement. To understand the air quality change from the perspective of aerosol optical depth (AOD), we adopted two statistical methods of Empirical Orthogonal Functions (EOF) and Non-negative Matrix Factorization (NMF) to AOD retrieved by MODIS over China and surrounding areas. Results showed that EOF and NMF identified the important factors influencing AOD over China from different angles: natural dusts controlled the seasonal variation with contribution of 42.4%, and anthropogenic emissions have larger contribution to AOD magnitude. To better observe the interannual variation of different sources, we removed seasonal cycles from original data and conducted EOF analysis on AOD monthly anomalies. Results showed that aerosols from anthropogenic sources had the greatest contribution (27%) to AOD anomaly variation and took an obvious downward trend, and natural dust was the second largest contributor with contribution of 17%. In the areas surrounding China, the eastward aerosol transport due to prevailing westerlies in spring significantly influenced the AOD variation over West Pacific with the largest contribution of 21%, whereas the aerosol transport from BTH region in winter had relative greater impact on the AOD magnitude. After removing seasonal cycles, biomass burning in South Asia became the most important influencing factor on AOD anomalies with contribution of 10%, as its interannual variability was largely affected by El Niño. Aerosol transport from BTH was the second largest contributor with contribution of 8% and showed a decreasing trend. This study showed that the downward trend of AOD over China since 2011 was dominated by aerosols from anthropogenic sources, which in a way confirmed the effectiveness of air pollution control policies.