Solid waste, a lever for decarbonization

Reducing methane emissions from solid waste is already technically possible.

The United States and China on the paths and policies to carbon neutrality

The rapid economic development has highlighted the global climate change problem and carbon dioxide emissions have brought challenges to global climate change. The combined carbon emissions of the United States and China are nearly half of global carbon emissions. These two countries have made great contributions to environmental protection and responded actively to global warming, and set the goal of carbon neutrality. This study takes the United States and China as examples to compare their national paths and policies to achieve carbon neutrality while also analyzing the stage effects of carbon emission reduction in these two countries. This study found that the policy systems in the United States and China are opposites of each other. The United States is a "Bottom to Top" system while China is a "Top to Bottom". The CO₂ emission in the United States is currently in the absolute carbon emission reduction period, that is, the reduction of total carbon emissions; while China is in the relative carbon emission reduction period, that is, the reduction of carbon emission intensity. China's transition time from carbon peaking to carbon neutrality is shorter than that of the United States, which is a huge challenge for China because its population is much larger than that of the United States. The results of this research can be used by other countries and regions for supporting carbon reduction policy decision-making and achieving UN sustainable development goals (SDGs).

Disaster Chain Analysis of Landfill Landslide: Scenario Simulation and Chain-Cutting Modeling

Landfill landslide is a man-made event that occurs when poorly managed garbage mounds at landfills collapse. It has become common in recent decades due to the rising waste volumes in cities. Normally, it is a complex process involving many disaster-causing factors and composed by many sequential sub-events. However, most current studies treat the landslide as a single and independent event and cannot give a full picture of the disaster. We propose a disaster chain analysis framework for landfill landslide in terms of scenario simulation and chain-cutting modeling. Each stage of the landfill landslide is modeled by taking advantage of various advanced techniques, e.g., remote sensing, 3DGIS, non-Newtonian fluid model, central finite difference scheme, and agent-base steering model. The 2015 Shenzhen “1220” landslide was firstly reviewed to summarize the general disaster chain model for landfill landslide. Guided by this model, we then proposed the specific steps for landfill landslide disaster chain analysis and applied them to another undergoing landfill, i.e., Xinwuwei landfill in Shenzhen, China. The scenario simulation in this landfill provides suggestions on potential hazardous risks and some applicable treatments. Through chain-cutting modeling, we further validated the effectiveness and feasibility of these treatments. The most optimized solution is subsequently deduced, which can provide support for disaster prevention and mitigation for this landfill.

Identification of Polycentric Cities in China Based on NPP-VIIRS Nighttime Light Data

Nighttime light data play an important role in the research on cities, while the urban centers over a large spatial scale are still far from clearly understood. Aiming at the current challenges in monitoring the spatial structure of cities using nighttime light data, this paper proposes a new method for identifying urban centers for massive cities at the large spatial scale based on the brightness information captured by the Suomi National Polar-Orbiting Partnership’s Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) sensor. Based on the method for extracting the peak point based on digital elevation model (DEM) data in terrain analysis, the maximum neighborhood and difference algorithms were applied to the NPP-VIIRS data to extract the pixels with the peak nighttime light intensity to identify the potential locations of urban centers. The results show 7239 urban centers in 2200 cities in China in 2017, with an average of 3.3 urban centers per city. Approximately 68% of the cities had significant polycentric structures. The developed method in this paper is useful for identifying the urban centers and can provide the reference to the city planning and construction.

Spatiotemporal Analysis of Water Quality Using Multivariate Statistical Techniques and the Water Quality Identification Index for the Qinhuai River Basin, East China

Monitoring water quality is indispensable for the identification of threats to water environment and later management of water resources. Accurate monitoring and assessment of water quality have been long-term challenges. In this study, multivariate statistical techniques (MST) and water quality identification index (WQII) were applied to analyze spatiotemporal variation in water quality and determine the major pollution sources in the Qinhuai River, East China. A rotated principal component analysis (PCA) identified three potential pollution sources during the wet season (mixed pollution, physicochemical, and nonpoint sources of nutrients) and the dry season (nutrient, primary environmental, and organic sources) and they explained 81.14% of the total variances in the wet season and 78.42% of total variances in the dry season. The result of redundancy analysis (RDA) showed that population density, urbanization, and wastewater discharge are the main sources of organic pollution, while agricultural fertilizer consumption and industrial wastewater discharge are the main sources of nutrients such as nitrogen and phosphorus. The water quality of the Qinhuai River basin was determined to be mainly Class III (slightly polluted) and Class IV (moderately polluted) based on WQII. Temporally, the change trend of WQII showed that water quality gradually deteriorated between 1990 and 2005, improved between 2006 and 2010, and then deteriorated again. Spatially, the WQII distribution map showed that areas with more developed urbanization were relatively more polluted. Our results show that MST and WQII are useful tools to help the public and decision makers to evaluate the water quality of aquatic environment.

Vehicle emission and atmospheric pollution in China: problems, progress, and prospects

China has been the largest vehicle market in the world since 2009. The stalemate between the rapid development of the vehicle industry and delayed vehicle emission control has become increasingly prominent. Vehicle emission has become a significant source of air pollution in China's cities. Understanding the current barriers in the vehicle industry is necessary for the development of effective and sustainable measures and policy to manage vehicle-induced air pollution. This review provides insight into the circumstances and causes of vehicle-induced air pollution and outlines recent progress in policy-makers' long-term strategies and regulations. The development of an integrated mechanism of social participation, technical revolution, and regulatory innovation in vehicles, fuel, and roads is suggested to break the stalemate between air pollution and the automobile boom in China; the implications of this review extend to other countries facing the similar atmospheric pollution problems.

Post-failure behavior analysis of the Shenzhen "12.20" CDW landfill landslide

Since the 1990s, with rapid economic development and urbanization occurring in many countries, the amount of construction and demolition waste (CDW) has also increased. Landfills have become the most commonly used method of disposing of CDW. The safety of landfill slopes is very important. On December 20, 2015, a catastrophic landslide occurred in Shenzhen, Guangdong, Southeastern China. Seventy-seven people were killed, and 33 buildings were buried or damaged. In this paper, the Shenzhen 12.20 landslide is used as an example, and the characteristics of the landfill landslide's post-failure behavior are studied. The following conclusions are made: (1) According to our field investigations, the landslide's motion can be divided into the source area, the propagation area, and the accumulation area. During post-failure motion, loose saturated spoil, which experiences motion similar to that of a slurry flow, and water are the critical factors that cause slope failure and result in a long runout slide. (2) The DAN3D analysis method can satisfactorily reproduce the motion of the Shenzhen "12.20" landslide. (3) A Frictional model can be used for the simulation analysis of the source area. In addition, the Bingham model can be used for the fluidization simulation analysis of the propagation and accumulation areas of a CDW landslide. These conclusions can be used for scientific analysis of CDW landfill landslide hazard zoning and early monitoring and warnings.

Waste management, informal recycling, environmental pollution and public health

With rapid population growth, especially in low-income and middle-income countries, the generation of waste is increasing at an unprecedented rate. For example, annual global waste arising from waste electrical and electronic equipment alone will have increased from 33.8 to 49.8 million tonnes between 2010 and 2018. Despite incineration and other waste treatment techniques, landfill still dominates waste disposal in low-income and middle-income countries. There is usually insufficient funding for adequate waste management in these countries and uptake of more advanced waste treatment technologies is poor. Without proper management, many landfills represent serious hazards as typified by the landslide in Shenzhen, China on 20 December 2015. In addition to formal waste recycling systems, approximately 15million people around the world are involved in informal waste recycling, mainly for plastics, metals, glass and paper. This review examines emerging public health challenges, in particular within low-income and middle-income countries, associated with the informal sector. While informal recyclers contribute to waste recycling and reuse, the relatively primitive techniques they employ, combined with improper management of secondary pollutants, exacerbate environmental pollution of air, soil and water. Even worse, insufficient occupational health measures expose informal waste workers to a range of pollutants, injuries, respiratory and dermatological problems, infections and other serious health issues that contribute to low life expectancy. Integration of the informal sector with its formal counterparts could improve waste management while addressing these serious health and livelihood issues. Progress in this direction has already been made notably in several Latin American countries where integrating the informal and formal sectors has had a positive influence on both waste management and poverty alleviation.

Urban construction and demolition waste and landfill failure in Shenzhen, China

On December 20, 2015 at 11:40 am a landslide in one of China's most advanced cities, Shenzhen, killed 73 people and damaged 33 buildings. In the absence of heavy rainfall or earthquakes, the landslide was an unexpected and profound shock to many people. According to China's Ministry of Land and Resources, the landslide was triggered by the collapse of an enormous pile of construction and demolition waste (CDW). With China's rapid urbanization, an increasing amount of CDW is being generated, especially in major cities. In total, China produces some 30% of the world's municipal solid waste and of this about 40% is CDW. To prevent landslides associated with CDW, the volume of waste dumped in landfills should be regulated. More specifically 4-Rs (reduce, reuse, recycle and recover) policies should be implemented more widely and efficiently. Although landfill will continue to be an important disposal option, proper management and careful monitoring of CDW are urgently needed to satisfy pressing safety issues. International collaboration, sharing of knowledge, and use of the latest technologies are needed so that the similar landslides can be prevented in China and elsewhere.

Carbon emissions from land-use change and management in China between 1990 and 2010

China has experienced enormous changes in land use in recent decades, which are largely driven by its unparalleled economic development. We analyze changes in vegetation and soil carbon storage between 1990 and 2010 resulting from combinations of land-use category conversion and management. Results demonstrate a major decline in grasslands (-6.85%; 20.83 × 10⁶ ha) and large increases in urban areas (+43.73%; 6.87 × 10⁶ ha), farmlands (+0.84%; 1.48 × 10⁶ ha), and forests (+0.67%; 1.52 × 10⁶ ha). The total soil organic carbon pool has been reduced by approximately 11.5 Tg of carbon (TgC) year^-1, whereas 13.2 TgC year^-1 has accumulated in the biomass carbon pool because of land-use category change. Large carbon losses (approximately 101.8 TgC year^-1) have resulted from land management failures, including forest fires and insect pests. Overall land-use change and land management have contributed about 1.45 Pg of carbon to the total carbon released from 1990 to 2010. Our results highlight the importance of improving land-use management, especially in view of the recently proposed expansion of urban areas in China.