Abstract
This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Review pubs.acs.org/CR Multiphase Chemistry at the Atmosphere−Biosphere Interface Influencing Climate and Public Health in the Anthropocene Ulrich Po schl* and Manabu Shiraiwa* Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany air contaminants (SHCC) and their multiphase chemical interactions at the atmosphere−biosphere interface, including human lungs and skin, plant leaves, cryptogamic covers, soil, and aquatic surfaces. After an overview of different groups of SHCC, we address the chemical interactions of reactive oxygen species and reactive nitrogen species (ROS, RNS), primary biological and secondary organic aerosols (PBA, SOA), as well as carbonaceous combustion aerosols (CCA) including soot, black/elemental carbon, polycyclic aromatic hydrocarbons, and related compounds (PAH, PAC). ROS and RNS interact strongly with other SHCC and are central to both atmospheric and physiological processes and their coupling through the atmosphere−biosphere interface, for example, in the formation and aging of biogenic and combustion aerosols as well as in CONTENTS inflammatory and allergic immune responses triggered by air pollution. Deposition of atmospheric ROS/RNS and aerosols 1. Introduction and Motivation can damage biological tissues, modify surface microbiomes, and 2. Health- and Climate-Relevant Air Contaminants induce oxidative stress through Fenton-like reactions and 2.1. Reactive Oxygen and Nitrogen Species immune responses. The chemical mechanisms and kinetics are 2.2. Primary Biological Aerosols not yet fully elucidated, but the available evidence suggests that 2.3. Secondary Organic Aerosols multiphase processes are crucial for the assessment, prediction, 2.4. Carbonaceous Combustion Aerosols and handling of air quality, climate, and public health. Caution 2.5. Other Air Contaminants Linking Atmospher- should be taken to avoid that human activities shaping the ic and Physiological Chemistry Anthropocene create a hazardous or pathogenic atmosphere 3. Multiphase Chemical Reactions at Specific Bio- overloaded with allergenic, corrosive, toxic, or infectious logical Interfaces contaminants. 3.1. Lung Lining Fluid Multiphase chemistry deals with chemical reactions, trans- 3.2. Human Skin port processes, and transformations between gaseous, liquid, 3.3. Plant Surfaces and Cryptogamic Covers and solid matter. These processes are essential for Earth system 3.4. Soil and Aquatic Surfaces science and climate research as well as for life and health 4. Conclusions and Outlook sciences on molecular and global levels, bridging a wide range Author Information of spatial and temporal scales from below nanometers to Corresponding Authors thousands of kilometers and from less than nanoseconds to Notes years and millennia as illustrated in Figure 1. Biographies From a chemical perspective, life and the metabolism of most Acknowledgments living organisms can be regarded as multiphase processes References involving gases like oxygen and carbon dioxide; liquids like water, blood, lymph, and plant sap; and solid or semisolid substances like bone, tissue, skin, wood, and cellular 1. INTRODUCTION AND MOTIVATION membranes. Even primitive forms of life and metabolic activity Multiphase chemistry plays a vital role in the Earth system, under anaerobic conditions generally involve multiple liquid climate, and health. Chemical reactions, mass transport, and and solid or semisolid phases structured by cells, organelles, and phase transitions between gases, liquids, and solids are essential membranes. 2 On global scales, the biogeochemical cycling of for the interaction and coevolution of life and climate. chemical compounds and elements, which can be regarded as Knowledge of the mechanisms and kinetics of these processes the metabolism of planet Earth, also involves chemical is also required to address societally relevant questions of global reactions, mass transport, and phase transitions within and environmental change and public health in the Anthropocene, that is, in the present era of globally pervasive and steeply Special Issue: 2015 Chemistry in Climate increasing human influence on planet Earth. 1 In this work, we review the current scientific understanding and recent advances Received: September 1, 2014 in the investigation of short-lived health- and climate-relevant Published: April 9, 2015 © 2015 American Chemical Society DOI: 10.1021/cr500487s Chem. Rev. 2015, 115, 4440−4475
Highlights
Secondary Organic Aerosols (SOA) account for a major fraction of fine particulate matter in the atmosphere,8d,h,i,k,84 affecting climate by scattering sunlight and serving as nuclei for cloud droplets and ice crystals.5,8c,e,j−m,85 They are formed via oxidation of volatile organic compounds (VOC) by atmospheric oxidants such as OH, O3, NO3, or reactive halogen species,[86] generating myriads of semiand low-volatile compounds that partition into the particle phase.33b,87 Prominent SOA precursors include biogenic VOC88 such as isoprene, monoterpenes (C10H16: α- and βpinene, limonene, etc.), and sesquiterpenes (C15H24) as well as anthropogenic VOC89 such as alkanes and aromatics
Review source of HNCO to humans at levels that may lead to such adverse health effects.18b The gas-phase concentration of HNCO can be up to 600 ppb in laboratory biomass fires and up to 200 ppt in ambient air in urban Los Angeles, CA and in Boulder, carbon monoxide (CO).18b,195 Global chemical transport modeling has suggested that annual mean surface HNCO concentrations were highest over parts of China, but episodic fire emissions gave much higher levels, exceeding 4 ppb in tropical Africa and the Amazon, and exceeding 10 ppb in Southeast Asia and Siberia. These results suggest that large biomass burning events associated with high concentrations of HNCO and aerosol particles could result in deleterious health effects for the human population in these regions.[199]
Relevant are the following groups of short-lived health- and climate-relevant air contaminants (SHCC) as reviewed in this work: (1) reactive oxygen and nitrogen species (ROS/reactive nitrogen species (RNS)) in the gas phase (O3, OH, H2O2, NOx, HONO, HNO3, etc.) as well as long-lived reactive oxygen intermediates (ROI) and persistent radicals on aerosol particles; (2) primary biological aerosols (PBA) comprising natural bacteria, fungal spores, and pollen as well as chemically or genetically modified organisms or proteins; (3) secondary organic aerosols (SOA) that are formed by oxidation of volatile organic compounds from biogenic and anthropogenic sources and undergo further chemical aging and phase transitions in the atmosphere; and (4) carbonaceous combustion aerosols (CCA) including soot, black/elemental carbon (BC/EC), polycyclic aromatic compounds, and other hazardous species like transition metals
Summary
Recent studies have used the term “short-lived climate pollutants” (SLCP) for atmospheric constituents that affect climate as well as public health with atmospheric lifetimes from days to a few decades.[16]. Aerosol interactions substantially alter the relative importance of SLCP emissions and influence the assessment and effects of mitigation policies.[18] While the narrow original definition of SLCP comprised only soot, ozone, hydrofluorocarbons (HFC), and CH4,16a we follow up on wider definitions[19] and suggest that all short-lived air contaminants relevant for health and climate, including toxic volatile and semivolatile compounds and elements like polycyclic aromatic hydrocarbon (PAH), isocyanic acid (HNCO), and mercury,[20] as well as aerosol particles from biogenic and anthropogenic sources such as primary biological and secondary organic aerosol (PBA/SOA), soil dust,[21] and volcanic ashes, be summarized under the common umbrella term “short-lived health- and climaterelevant air contaminants (SHCC)” This umbrella term includes but goes beyond legislatively regulated categories of “hazardous air pollutants” and “toxic air contaminants”[22] (see Table 16.15 of Finlayson-Pitts and Pitts (2000)[23]). Biosphere exchange of select groups of SHCC: reactive oxygen and nitrogen species; primary biological, secondary organic, and carbonaceous combustion aerosols; and other prominent air contaminants
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