气候变化领域集成服务门户(CCPortal): Global modeling of cloud water acidity, precipitation acidity, and acid inputs to ecosystems

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DOI	10.5194/acp-20-12223-2020
	Global modeling of cloud water acidity, precipitation acidity, and acid inputs to ecosystems
	Shah V.; Jacob D.J.; Moch J.M.; Wang X.; Zhai S.
发表日期	2020
ISSN	1680-7316
起始页码	12223
结束页码	12245
卷号	20 期号:20
英文摘要	Cloud water acidity affects the atmospheric chemistry of sulfate and organic aerosol formation, halogen radical cycling, and trace metal speciation. Precipitation acidity including post-depositional inputs adversely affects soil and freshwater ecosystems. Here, we use the GEOS-Chem model of atmospheric chemistry to simulate the global distributions of cloud water and precipitation acidity as well as the total acid inputs to ecosystems from wet deposition. The model accounts for strong acids (H2SO4, HNO3, and HCl), weak acids (HCOOH, CH3COOH, CO2, and SO2), and weak bases (NH3 as well as dust and sea salt aerosol alkalinity). We compile a global data set of cloud water pH measurements for comparison with the model. The global mean observed cloud water pH is 5:2 ± 0:9, compared to 5:0 ± 0:8 in the model, with a range from 3 to 8 depending on the region. The lowest values are over East Asia, and the highest values are over deserts. Cloud water pH over East Asia is low because of large acid inputs (H2SO4 and HNO3), despite NH3 and dust neutralizing 70 % of these inputs. Cloud water pH is typically 4 5 over the US and Europe. Carboxylic acids account for less than 25 % of cloud water HC in the Northern Hemisphere on an annual basis but 25 % 50 % in the Southern Hemisphere and over 50 % in the southern tropical continents, where they push the cloud water pH below 4.5. Anthropogenic emissions of SO2 and NOx (precursors of H2SO4 and HNO3) are decreasing at northern midlatitudes, but the effect on cloud water pH is strongly buffered by NHC 4 and carboxylic acids. The global mean precipitation pH is 5.5 in GEOS-Chem, which is higher than the cloud water pH because of dilution and below-cloud scavenging of NH3 and dust. GEOS-Chem successfully reproduces the annual mean precipitation pH observations in North America, Europe, and eastern Asia. Carboxylic acids, which are undetected in routine observations due to biodegradation, lower the annual mean precipitation pH in these areas by 0.2 units. The acid wet deposition flux to terrestrial ecosystems taking into account the acidifying potential of NO-3 and NHC4 in Nsaturated ecosystems exceeds 50 meqm-2 a-1 in East Asia and the Americas, which would affect sensitive ecosystems. NHC4 is the dominant acidifying species in wet deposition, contributing 41 % of the global acid flux to continents under N-saturated conditions. © 2020 Author(s).
语种	英语
scopus关键词	acidity; aerosol; atmospheric chemistry; carboxylic acid; cloud water; halogen; modeling; pH; precipitation (climatology); speciation (chemistry); sulfate; trace metal; wet deposition
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/247446
作者单位	Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, United States; Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, United States; School of Energy and Environment, City University of Hong Kong, Hong Kong, Hong Kong
推荐引用方式 GB/T 7714	Shah V.,Jacob D.J.,Moch J.M.,et al. Global modeling of cloud water acidity, precipitation acidity, and acid inputs to ecosystems[J],2020,20(20).
APA	Shah V.,Jacob D.J.,Moch J.M.,Wang X.,&Zhai S..(2020).Global modeling of cloud water acidity, precipitation acidity, and acid inputs to ecosystems.ATMOSPHERIC CHEMISTRY AND PHYSICS,20(20).
MLA	Shah V.,et al."Global modeling of cloud water acidity, precipitation acidity, and acid inputs to ecosystems".ATMOSPHERIC CHEMISTRY AND PHYSICS 20.20(2020).