Grantee Research Project Results

2004 Progress Report: Inflow, Chemistry and Deposition of Mercury to the West Coast of the United States

EPA Grant Number: R829797
Title: Inflow, Chemistry and Deposition of Mercury to the West Coast of the United States
Investigators: Jaffe, Daniel , Prestbo, Eric
Institution: University of Washington
EPA Project Officer: Chung, Serena
Project Period: June 1, 2002 through June 1, 2005
Project Period Covered by this Report: June 1, 2003 through June 1, 2004
Project Amount: $756,774
RFA: Mercury: Transport, Transportation, and Fate in the Atmosphere (2001) RFA Text |  Recipients Lists
Research Category: Heavy Metal Contamination of Soil/Water , Air Quality and Air Toxics , Air , Safer Chemicals

Objective:

The primary objectives of this research project are to quantify the flux of Hg to the United States from global sources, characterize the seasonal patterns and chemical speciation of this flux, and examine the background deposition of Hg along the West Coast of the United States. In particular, we want to evaluate the significance of large Hg sources in Asia on transport and deposition of Hg in the United States. From our previous work, we know that long-range transport of pollutants from Asia to the United States occurs on a fairly regular basis.

Progress Summary:

During Year 2 of this project, we made Hg measurements at two sites: (1) Mt. Bachelor Observatory (MBO), a high elevation (9000 ft), free tropospheric site in central Oregon (March 2004-present); and (2) Cape Hedo, Okinawa, Japan, (Hedo Station Okinawa; HSO) a remote site that receives substantial influence from Chinese pollution sources (March-May 2004).

At both MBO and HSO, the Hg measurements were colocated with instrumentation for CO, ozone (O₃), and aerosols. This will allow us to characterize the general state of the atmosphere, as well as carry out quantitative budget and flux calculations.

The Hg and CO data from Okinawa clearly are elevated above their respective global backgrounds. This reflects the substantial influence from Asian sources at this site. The MBO Hg results are closer to the global background but still somewhat elevated. This likely reflects the location of MBO, which is in the free troposphere and downstream of Asia. Using the Hg/CO ratio, and a well-evaluated emission inventory for CO, we can calculate the emissions of Hg from Asia. Our calculations indicate Asian emissions of Hg⁰ of 1,460 metric tons/year, which is significantly larger then the reported inventories. This method relies on several reasonable assumptions about Hg and CO, which our data largely support. Although it is tempting to conclude that the inventories are incorrect, this would not be a correct interpretation of our results. It is possible that natural and/or reemission of “old” mercury can fully account for the discrepancy. A manuscript describing the details of this work has been accepted for publication in Atmospheric Environment (Jaffe, et al., 2005).
There are several other important results from our 2004 observations, including a pronounced diurnal cycle of reactive gaseous mercury (RGM) at HSO, the consistency of the Hg/CO ratio during Asian plumes at both MBO and HSO, and comparisons with the Global Earth Observations System-Chem global model, in collaboration with Daniel Jacob at Harvard. A summary of Hg and CO observations at HSO and MBO is shown in Table 1.

Table 1. Summary of Hg and CO Observations at HSO (March 23-May 2, 2004) and MBO (March 28-May 17, 2004)

In addition to these observations, during Year 2 of the project, we worked to develop a reliable method for field calibrations of RGM. The system is based on an HgCl₂ permeation tube. To date, we have developed a steady source of HgCl₂; however, collection efficiency of the Tekran denuder system appears to be somewhat low. We are continuing to investigate this challenge and will have more to report in the coming year.

Future Activities:

We will add observations of RGM and particulate Hg at the Mt. Bachelor site. They will be the first observations of these Hg species in the free troposphere. We will conduct aircraft vertical profiles of Hg(0). This will take place in the fall of 2005. In addition to Hg, the aircraft also will measure CO, O₃, aerosols, and temperature/relative humidity. The observations will provide an important constraint to global models on the vertical distribution and lifetime of global atmospheric Hg. We will continue to analyze the data collected in 2004 from MBO and Okinawa. This should lead to several additional publications.

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views

Other project views:	All 34 publications	7 publications in selected types	All 7 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Jaffe D, Prestbo E, Swartzendruber P, Weiss-Penzias P, Kato S, Takami A, Hatakeyama S, Kajii Y. Export of atmospheric mercury from Asia. Atmospheric Environment 2005;39(17):3029-3038.	R829797 (2004) R829797 (2005) R829797 (Final)	Full-text: Science Direct Full Text Exit Abstract: Science Direct Abstract Exit
Journal Article	Weiss-Penzias P, Jaffe DA, Swartzendruber P, Dennison JB, Chand D, Hafner W, Prestbo E. Observations of Asian air pollution in the free troposphere at Mount Bachelor Observatory during the spring of 2004. Journal of Geophysical Research 2006;111:D10304, doi:10.1029/2005JD006522.	R829797 (2004) R829797 (2005) R829797 (Final)	Abstract: AGU Abstract Exit

Supplemental Keywords:

air, ambient air, tropospheric pollution, chemical transport, toxics, air toxics, metals, heavy metals, mercury, environmental chemistry, atmospheric chemistry, pacific northwest, long-range transport,, Scientific Discipline, Water, Mercury, Environmental Chemistry, Ecology and Ecosystems, West Coast, marine boundary layer, mercury detection, atmospheric deposition, mercury measurement, fate and transport, formation, chemical speciation

Relevant Websites:

http://faculty.washington.edu/djaffe Exit

Progress and Final Reports:

Original Abstract

2002

2003 Progress Report

Final Report