Anthropogenic Effects on Biogenic Secondary Organic Aerosol Formation

Abstract

Anthropogenic emissions alter biogenic secondary organic aerosol (SOA) formation from naturally emitted volatile organic compounds (BVOCs). We review the major laboratory and field findings with regard to effects of anthropogenic pollutants (NO_x, anthropogenic aerosols, SO₂, NH₃) on biogenic SOA formation. NO_x participate in BVOC oxidation through changing the radical chemistry and oxidation capacity, leading to a complex SOA composition and yield sensitivity towards NO_x level for different or even specific hydrocarbon precursors. Anthropogenic aerosols act as an important intermedium for gas—particle partitioning and particle-phase reactions, processes of which are influenced by the particle phase state, acidity, water content and thus associated with biogenic SOA mass accumulation. SO₂ modifies biogenic SOA formation mainly through sulfuric acid formation and accompanies new particle formation and acid-catalyzed heterogeneous reactions. Some new SO₂-involved mechanisms for organosulfate formation have also been proposed. NH₃/amines, as the most prevalent base species in the atmosphere, influence biogenic SOA composition and modify the optical properties of SOA. The response of SOA formation behavior to these anthropogenic pollutants varies among different BVOCs precursors. Investigations on anthropogenic—biogenic interactions in some areas of China that are simultaneously influenced by anthropogenic and biogenic emissions are summarized. Based on this review, some recommendations are made for a more accurate assessment of controllable biogenic SOA formation and its contribution to the total SOA budget. This study also highlights the importance of controlling anthropogenic pollutant emissions with effective pollutant mitigation policies to reduce regional and global biogenic SOA formation.

摘 要

人为源排放会改变生物源挥发性有机化合物(BVOCs)的二次有机气溶胶(SOA)形成。本文综述了人为污染物(NO_x,人为源气溶胶,SO₂,NH₃)对生物源SOA形成影响的主要实验室研究和外场观测结果。NO_x通过改变自由基化学和大气氧化能力来参与BVOC的氧化,从而导致不同BVOCs,甚至同一BVOC前体物形成的SOA组成和产率对NO_x浓度水平的复杂敏感性。人为源气溶胶是气粒分配和颗粒相反应的重要媒介,颗粒相态、酸度以及水含量等因素都会影响生物源SOA的质量累积。SO₂主要通过生成硫酸及其引发的新粒子形成和酸催化非均相反应等改变生物源SOA的形成。此外,还总结了SO₂参与的有机硫酸盐形成的新机理。NH₃/有机胺是大气中最普遍的碱性物种,会影响生物源SOA的化学组成并改变其光学性质。SOA的生成对这些人为污染物的响应因不同的BVOC前体物而异。中国一些地区会同时受到人为源和生物源排放的影响,本文进一步总结了这些地区的人为源-生物源相互作用,对更准确地评估生物源SOA中的可控部分及其对SOA总负荷的贡献也提出了一些建议。本文强调了通过有效的污染物控制政策来控制人为污染物排放以减少区域和全球生物源SOA形成的重要性。