Yuanan Hu

Lead (Pb) isotopic fingerprinting and its applications in lead pollution studies in China: A review

As the most widely scattered toxic metal in the world, the sources of lead (Pb) observed in contamination investigation are often difficult to identify. This review presents an overview of the principles, analysis, and applications of Pb isotopic fingerprinting in tracing the origins and transport pathways of Pb in the environment. It also summarizes the history and current status of lead pollution in China, and illustrates the power of Pb isotopic fingerprinting with examples of its recent applications in investigating the effectiveness of leaded gasoline phase-out on atmospheric lead pollution, and the sources of Pb found in various environmental media (plants, sediments, and aquatic organisms) in China. The limitations of Pb isotopic fingerprinting technique are discussed and a perspective on its development is also presented. Further methodological developments and more widespread instrument availability are expected to make isotopic fingerprinting one of the key tools in lead pollution investigation.

Municipal solid waste (MSW) as a renewable source of energy: Current and future practices in China

With rapid economic growth and massive urbanization, China faces the problem of municipal solid waste (MSW) disposal and the pressing need for development of alternative energy. Waste-to-energy (WTE) incineration, which recovers energy from discarded MSW and produces electricity and/or steam for heating, is recognized as a renewable source of energy and is playing an increasingly important role in MSW management in China. This article provides an overview of the WTE industry, discusses the major challenges in expanding WTE incineration in China, namely, high capital and operational costs, equipment corrosion, air pollutant emissions, and fly ash disposal. A perspective on MSW as a renewable energy source in China is also presented. Currently, only approximately 13% of MSW generated in China is disposed in WTE facilities. With the significant benefits of environmental quality, the reduction of greenhouse gas (GHG) emissions, and government policies and financial incentives as a renewable energy source, WTE incineration industry is expected to experience significant growth in the coming decade and make greater contribution to supplying renewable energy in China.

Geochemical processes controlling fate and transport of arsenic in acid mine drainage (AMD) and natural systems.

Acid mine drainage (AMD) is often accompanied with elevated concentrations of arsenic, in the forms of arsenite, As(III), and/or arsenate, As(V), due to the high affinity of arsenic for sulfide mineral ores. This review summarizes the major geochemical processes controlling the release, speciation, fate, and distribution of inorganic arsenic in mine drainage and natural systems. Arsenic speciation depends highly on redox potential and pH of the solution, and arsenite can be oxidized to the less toxic arsenate form. Homogeneous oxidation of arsenite occurs rather slowly while its heterogeneous oxidation on mineral surfaces can greatly enhance the reaction rates. Little evidence suggests that precipitation reaction limits the concentrations of arsenic in natural water, while co-precipitation may lead to rapid arsenic removal when large amount of iron hydroxides precipitate out of the aqueous phase upon neutralization of the mine drainage. Both arsenate and arsenite adsorb on common metal oxides and clay minerals through formation of inner-sphere and/or outer-sphere complexes, controlling arsenic concentration in natural water bodies. Arsenite adsorbs less strongly than arsenate in the typical pH range of natural water and is more mobile. Part of the adsorbed arsenic species can be exchanged by common anions (e.g., PO(4)(3-) and SO(4)(2-)), especially phosphate, which leads to their re-mobilization. Understanding the geochemistry of arsenic is helpful for predicting its mobility and fate in AMD and natural systems, and for designing of cost-effective remediation/treatment strategies to reduce the occurrence and risk of arsenic contamination.

Curbing dioxin emissions from municipal solid waste incineration in China: Re-thinking about management policies and practices

As one of the countries with large amounts of dioxin releases, the control of dioxins is a major challenge for China. Municipal solid waste (MSW) incineration should be considered a high priority source of dioxin emissions because it is playing an increasingly more important role in waste management. MSW incineration in China has much higher emission rates of dioxins than in the developed countries, partially resulting from the gaps in the technologies of incineration and flue gas cleaning. Moreover, the current management policies and practices also contribute significantly to the problem. We recommend lowering dioxin emission standard, strengthening fly ash management, and improving regulation enforcement to reduce dioxin releases into the environment from MSW incineration. We also propose that alternative strategies should be considered on dioxin control and call for an expansion of economic instruments in waste management to reduce waste generation and thus the need for incineration.

Improving China’s water resources management for better adaptation to climate change

Challenged by insufficient water resources and by degraded water quality caused by widespread pollution, China faces an imbalance between the supply and the demand of water for supporting the rapid social and economic development while protecting the natural environment and ecosystems. Climate change is expected to further stress freshwater resources and widen the gap between the demand for and supply of water. As a legacy of the earlier planned economy, water resources management has been primarily supply-driven, which largely fails to account for the economic nature of water resources in relation to their natural characteristics. This paper presents a historical perspective on the water resources management policies and practices in China, and recommends demand management and pollution control as key measures for improving water resources management to adapt to climate change based on the current political, socio-economic and water resources conditions. The past and future impacts of climate change on water resources in China and the general adaptation strategies are also presented. How demand management through increasing water use efficiency, improving water rights and rights trade, and effective regulation enforcement, along with pollution control could improve China’s water resources management are discussed in details. Ultimately, China should develop a sustainable water resources management strategy based on both supply- and demand-side management options to make the limited water supplies meet the demands of economic development, social well-being and the conservation of ecosystems in the context of global climate change.

China needs to control mercury emissions from municipal solid waste (MSW) incineration.

H E F A C H E N G * , † , ‡ Y U A N A N H U § State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China, Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94025, United States, and Education Program for Gifted Youth, Stanford University, Stanford, California 94025, United States

Multipass membrane air-stripping (MAS) for removing volatile organic compounds (VOCs) from surfactant micellar solutions.

Air-stripping is one of the most effective technologies for removing volatile organic compounds (VOCs) from surfactant solutions, although the presence of surfactant poses some unique challenges. This study evaluated the effect of a mixed surfactant system on the apparent Henrys law constant of tetrachloroethylene (PCE) and the efficiency of PCE removal from surfactant solutions using a lab-scale hollow fiber membrane contactor. Results show that the presence of surfactant significantly reduced the apparent Henrys law constant of PCE, and the reduction was proportional to the total surfactant concentration. PCE removal efficiency by membrane air-stripping (MAS) decreased as the surfactant system transitioned from solubilization to supersolubilization. Besides significantly reducing the apparent volatility of VOCs, the presence of surfactant brings additional mass transfer resistance in air-stripping, which makes it difficult to achieve high levels of contaminant removal, even at very high air/liquid (A/L) ratios. In contrast, multipass/multistage MAS operated at low A/L ratios could achieve near 100% contaminant removal because of less mass transfer limitation during each stripping pass/stage. Experimental results, together with model calculations demonstrate multipass (and multistage) air-stripping as a cost-effective alternative for removing VOCs from surfactant micellar solutions compared to the options of using large air strippers or operating at high A/L ratios.

Economic Transformation, Technological Innovation, and Policy and Institutional Reforms Hold Keys to Relieving China’s Water Shortages

Although China ranks sixth in total water resources (2.8 trillion m3) in the world, with a population of 1.3 billion the country’s annual per capita renewable freshwater availability (less than 2200 m3) is only a quarter of the world’s average. The spatial distribution of water resources shows a significant mismatch with that of water demand, while large intraand interannual variability makes effective utilization of water resources difficult, particularly in the more arid north China (1). The increasing water demand brought by fast industrial and economic development, population growth, and rapid urbanization, combined with deteriorating water quality, have significantly intensified the water shortages in China. Balancing the limited supply of freshwater resources among various uses supporting agricultural activities, industrial production, and domestic consumption, as well as protecting the natural environment and ecosystems is a daunting challenge. The constraint of water resources on China’s future development and sustainability is further exacerbated by global climate change, which is expected to significantly impact the availability, and the quality and quantity of the accessible water (2). Figure 1 shows the water consumption per capita as a function of gross domestic product (GDP) per capita in China since 1949. With the rise in per capita GDP, agricultural water use first increased and then declined after reaching a plateau. Such relationship, known as the Kuznets curve, is not observed for industrial and domestic water uses yet, although total water consumption per capita has stabilized in recent years. The current water abstraction per capita is less than a quarter of the renewable freshwater availability in China, but further water abstraction is increasingly more difficult and expensive (3). Furthermore, irreversible environmental damage may result if the water abstraction exceeds the ecological threshold. China’s population will peak at 1.6 billion by 2030, lowering the annual per capita renewable freshwater availability to only 1760 m3 (1). It is clear that water demand brought by increasing population and productivity will not be met if the current practices and levels of water use efficiency were to continue. We believe that the long-run relief to China’s water shortages comes from the transformation from extensive to intensive economic growth, innovation in water-saving and treatment technologies, and reforms of policy and institutional framework toward sustainable water resources management. In addition, public