Tracer Studies of Sulfur Dioxide Oxidation in Clouds

EPA Grant Number: R823422
Title: Tracer Studies of Sulfur Dioxide Oxidation in Clouds
Investigators: Husain, Liaquat , Dutkiewicz, Vincent A.
Current Investigators: Husain, Liaquat
Institution: Wadsworth Center: New York State Department of Health , The State University of New York at Albany
Current Institution: The State University of New York at Albany
EPA Project Officer: Shapiro, Paul
Project Period: September 1, 1995 through August 31, 1998
Project Amount: $335,659
RFA: Exploratory Research - Chemistry and Physics of Air (1995) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Air , Engineering and Environmental Chemistry


The primary objective of this project is to quantify the oxidation of sulfur dioxide in cloud droplets in the Northeastern U.S. This information is essential to determine the Source-Receptor relationship between the regional sulfur dioxide emissions and the downwind acid deposition at distant locations. However, it is difficult to study sulfur dioxide oxidation in clouds because the product sulfate is derived from both gas- phase as well as aqueous-phase oxidation. A tracer technique developed in this laboratory overcomes this problem. The tracers used are the elements Se, As and Sb emitted in anthropogenic emissions from a variety of sources which reside on accumulation mode aerosols, i.e., the same size as sulfate aerosols produced in gas-phase oxidation. Since the only source of these elements in cloud water is the scavenging of aerosols, a determination of sulfate/(Se, As, or Sb) ratios in cloud water and cloud-free air yields the amount of sulfate formed in cloud from sulfur dioxide oxidation. Field campaigns to collect cloud water and associated aerosols and to measure gas-phase sulfur dioxide, hydrogen peroxide and supporting meteorologic data will be conducted during May through October at Whiteface Mountain (1.5 km amsl), New York. Major ions and selected trace metal determinations will be made on all cloud water and associated aerosols. In-cloud oxidation will be quantified with the tracer technique and compared to available hydrogen peroxide and meteorologic variables. By measuring both the depletion of reactant concentrations and quantifying sulfate formed in situ in short time intervals, we can follow the progress of the reaction in a detailed meteorologic-chemical model. This model would yield information on the mixing of an air parcel into the cloud and therefore an estimate of its residence time. Using a mountain-based site and sampling many clouds during various seasons, the effect of oxidant availability on in situ sulfate formation can elucidate the source-receptor relationship.

Publications and Presentations:

Publications have been submitted on this project: View all 2 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

air, ambient air, atmosphere, oxidants, sulfates, H2O2, SO2, environmental chemistry, monitoring, measurement methods, Northeast, New York, NY, Region 2, Scientific Discipline, Air, Geographic Area, Physics, Environmental Chemistry, State, Chemistry, Engineering, Chemistry, & Physics, EPA Region, ambient aerosol, anthropogenic stress, fate and transport, sulfur dioxide absorption, aerosol particles, source receptor relationship, field monitoring, gas-phase oxidation, meterology, tracer studies, Region 2, acid rain

Progress and Final Reports:

  • 1996
  • 1997
  • Final Report